Compounds for use as iron (III) MRI contrast agents containing anionic pendants and ancillary groups

Abstract

To provide macrocyclic compounds that can be complexed with Fe(III).SOLUTION: The macrocyclic complexes or macrocyclic compounds have a 1,4,7-triazacyclononane (TACN) moiety with one or more amine group(s) or an O- or S- substituted TACN moiety. The macrocyclic complexes have a high-spin Fe(III) atom coordinated to the TACN moiety. The macrocyclic complexes can be used in imaging methods.SELECTED DRAWING: None

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 62 / 768,823, filed November 16, 2018, the disclosure of which is incorporated herein by reference.

[0002] [Statement Regarding Federally Sponsored Research] This invention was made with Government support under Contract No. 1710224 awarded by the National Science Foundation and Contract No. EB025369 awarded by the National Institutes of Health. The Government has certain rights in this invention. [Technical field]

[0003] The present disclosure relates generally to macrocyclic compounds that, when complexed with iron(III), can be used as MRI contrast agents. Summary of the Invention

[0004] It is an object of the present disclosure to provide macrocyclic compounds capable of complexing Fe(III), as well as compositions and methods of making and using said compounds and complexes.

[0005] Fe(III) coordination complexes for use as T1 MRI contrast agents are disclosed. The disclosed Fe(III) T1 MRI contrast agents include macrocyclic ligands. The Fe(III) complexes may also be used as T2 MRI contrast agents.

[0006] The present disclosure provides macrocyclic compounds or rings (macrocycles) having i) a macrocyclic core containing at least two heteroatoms as ligand donors, and ii) at least one pendant donor (sometimes referred to as an anionic pendant) as a substituent of the macrocyclic core. The macrocyclic core has a ring structure containing carbon atoms and at least one heteroatom (e.g., N, O, or S atom). The macrocyclic core may be a TACN moiety. The macrocyclic core may be a TACN moiety in which one or more of the N atoms are replaced with O or S atoms.

[0007] For example, the pendant donor can be an oxygen-containing group (e.g., an alcohol, an oxide (e.g., an alkoxide or phenoxide), a sulfonate, a phosphinate, a phosphonate, etc.). Some pendant donors, such as alcohols, phosphinic acids, phosphonic acids, or sulfonic acids, can be deprotonated when complexed with Fe(III) or at certain pHs.

[0008] The macrocycle may include one or more auxiliary pendant groups, which may be one or more coordinating auxiliary pendant groups and / or one or more non-coordinating auxiliary pendant groups.

[0009] In one embodiment, the compounds of the present disclosure have two or more macrocyclic cores tethered together via aromatic groups (eg, aryl groups), macrocyclic rings, polymers, dendrimers, proteins, or peptides.

[0010] For use in the methods of the present disclosure, the compounds or complexes described herein can be administered as pharmaceutical preparations. Thus, they can be provided in a variety of compositions and can be combined with one or more pharma- ceutically acceptable carriers.

[0011] In one aspect, the present disclosure provides a method of imaging using the macrocyclic compounds described herein. The imaging method employs magnetic resonance imaging methods. Examples of such methods include, but are not limited to, magnetic resonance imaging (MRI). Specifically, the macrocyclic compounds of the present disclosure, when complexed with Fe(III), can be used as T1MRI contrast agents. The imaging methods of the present disclosure can be used to image cells, tissues, organs, vascular systems (vasculature), or parts thereof. The cells, tissues, organs, vascular systems can be part of an individual.

[0012] [Background to disclosure] Contrast agents containing Fe(III) as trivalent iron offer an alternative to Gd(III) contrast agents. To date, nearly all clinically used contrast agents contain gadolinium (Gd as trivalent Gd(III)), despite the fact that a significant proportion of patients in the US population (approximately 10%) are considered at risk for being given Gd(III) contrast agents. There is emerging concern that Gd(III)-based MRI contrast agents are leading to deposition of Gd(III) in the brain, bone and skin of all patients. Alternatives to Gd(III) contrast agents that contain biologically relevant transition metal ions, such as high-spin Fe(III) complexes, are expensive. Alternatives to Gd(III) contrast agents that contain biologically relevant transition metal ions include high-spin Mn(II) and high-spin Fe(III) complexes. Potential advantages of using Fe(III) include the widespread mechanisms in the human body to recycle and store iron, as the most abundant transition metal ion. Fe(III) complexes are also less prone to dissociation than Mn(II). Notably, the redox potentials of both Mn(II) and Fe(III) complexes can be tuned to prevent the generation of reactive oxygen species (ROS). For example, certain ligands form redox-inactive Fe(III) complexes that do not generate hydroxyl radicals, even under harsh conditions. The Fe-based MRI contrast agents described herein (as trivalent Fe(III)) generate contrast by the same paramagnetic mechanism as Gd(III) agents, and are in small molecule form as coordination complexes, i.e., not nanoparticles.

[0013] Most Fe(III) MRI contrast agents reported to date contain simple linear chelators, including those with an ethylenediamine backbone with a combination of phenol and carboxylate pendants, such as EHBG (N-N'-ethylenebis[(2-hydroxybenzyl)glycine]). Another type contains polyaminocarboxylate ligands, such as Fe(III) complexes of EDTA. A third type includes the microbial siderophore, desferrioxamine (DFO). All of these complexes suffer from a lack of exchangeable water ligands, a reduction potential that makes them susceptible to ROS generation, and / or It has drawbacks including difficulties in synthetic modification. Also, the aqueous solution chemistry of the Fe(III) complexes is dominated by the formation of insoluble complexes with hydroxide and bridging oxide ligands. Improvements are needed to obtain Fe(III) complexes that are desirable T1 moderators rather than effective catalysts for generating ROS by altering the redox potential to stabilize Fe(III). An additional consideration is the overall charge of the complex. Anionic groups attached to Fe(III) as pendants or more remotely attached as auxiliary groups are important for modulating the pharmacokinetics of the contrast agent and its elimination from the body.

[0014] Based at least on the foregoing, there exists an unmet need in the art for Fe(III) MRI contrast agents with improved properties. [Brief description of the drawings]

[0015] FIG. 1 shows a synthetic scheme for the TASO ligand.

[0016] FIG. 2 shows the synthesis scheme of the TRAP-Ph macrocycle with phosphine pendants and the corresponding Fe(III) complex.

[0017] FIG. 3 shows the synthesis of macrocycles with pendant phosphinic acids.

[0018] FIG. 4 shows the synthesis of macrocycles bearing pendant phosphinic or phosphonic acid compounds and the corresponding Fe(III) complexes.

[0019] FIG. 5 shows the synthetic scheme of the triazole pendant bearing an anionic group, its attachment to the macrocyclic ring, and the formation of the Fe(III) complex.

[0020] Figure 6 shows the structure of Fe(TASO) 1 H NMR shows a broadening in the baseline, consistent with high spin Fe(III), and a shift in the t-butanol proton resonance is observed.

[0021] Figure 7 shows that Fe(III) contrast agents such as Fe(TASO) do not oxidize benzoate in the presence of peroxide and ascorbate, unlike Fe(III) complexes of EDTA or CDTA. Oxidation of benzoate by 50 μM complex, 50 μM H2O2, 50 μM ascorbate (pH 7.2). The oxidation rate of [Fe(EDTA)] is set to 100%.

[0022] Figure 8 shows the results for various temperatures. 17 1 shows plots of data obtained from an O NMR study. For experiments containing 20 mM Fe(TASO) at pH 4.5, 17 The natural logarithm of the inverse transverse relaxation rate of the O NMR resonance is shown as a function of temperature.

[0023] FIG. 9 shows plots of the time course of T1 relaxivity in mice following Fe-TASO injection for various tissues including liver and kidney (compared to Gd(DTPA) and Fe(TOB)).

[0024] FIG. 10 shows plots of the time course of T1 relaxivity in mice following Fe(TASO) injection in blood (compared to Gd(DTPA) and Fe(TOB)).

[0025] FIG. 11 shows relaxivity data obtained at 4.7 Tesla and 37° C. for examples of macrocyclic complexes of the present disclosure. Fe-NOTP has a relaxivity of 0.66±0.01 mM -1 s -1 The r1 of Fe-NOTP with HSA was 1.04 ± 0.06 mM -1 s -1 The r1 was shown.

[0026] FIG. 12 shows cyclic voltammograms of 1.0 mM solutions of Fe(TASO) at various pHs in water containing potassium chloride (100 mM) as the supporting electrolyte and HEPES buffer. The maximum sweep width was between −1.5 V and 1.5 V, the scan rate for Fe(TASO) was 100 mV / s, and the E at pH 7. 1 / 2 was found at -204 mV and at pH 3 at 513 V, corrected for NHE.

[0027] FIG. 13 shows the cross-sectional profile for Fe(TASO) measured over a range of pH values ​​and compared with Fe(DTPA), Fe(TOB), and Fe(CDTA). 17 O NMR relaxivity as a function of temperature, ln(1 / T 2r )). Fe(CDTA) has exchangeable water ligands, while Fe(DTPA) has no exchangeable inner sphere water ligands.

[0028] Figure 14 shows the UV-Vis absorption spectra of Fe(TASO) obtained over 72 hours at 37° C. The aqueous solution contained 0.2 mM Fe(TASO) dissolved in 0.1 M HCl. ε(250nm)=6097 M- cm-, ε(325nm)=3557 M -1 cm -1 . After 24 hours, the dissociation rate was 18.1%. After 72 hours, the dissociation rate was 53.6%.

[0029] Figure 15 shows the UV-Vis absorption spectrum of Fe(TASO) obtained over 72 hours at 37 °C using an aqueous solution containing 0.2 mM Fe(TASO) dissolved in 25 mM NaHCO, 0.50 mM Na2HPO4, 10 mM HEPES buffer at pH 7.1. ε(245nm)=6960 M-cm-, ε(325nm)=3571 M -1 cm -1 .

[0030] FIG 16. UV-Vis absorption spectra of Fe(TASO) were obtained over 72 h at 37° C. The aqueous solution contained 0.2 mM Fe(TASO) dissolved in 10 mM HEPES buffer at pH 7.1. ε(245nm)=6762 M- cm-, ε(325nm)=3687 M -1 cm -1 .

[0031] Figure 17 shows T1-weighted MRI of a healthy Balb / C mouse at 4.7T with a dose of 0.2 mmol / kg Fe(TASO). Top row: before injection (a), 5 min (b), and 40 min (c). Post-injection images show kidney enhancement (arrow). Bottom row: images of the bladder (arrow). Before injection (d), 5 min, and 40 min (f).

[0032] Figure 18 shows T1-weighted MRI of healthy Balb / C mice at a dose of 0.05 mmol / kg Fe(TASO) at 4.7 T. Top: before (a), 30 min (b), 4 h (c), and 24 h (d). Post-injection images show kidney enhancement (arrows). The stomach is labeled S. Bottom: images of the liver (L) and gallbladder (arrows) before (e), 30 min (f), 4 h (g), and 24 h (h) post-injection.

[0033] FIG. 19 shows pharmacokinetic data in mice for Fe(TASO).

[0034] FIG. 20 shows pharmacokinetic data in mice for Fe(TASO) compared to clinically used Gd complexes.

[0035] FIG. 21 shows T1-weighted MR images of a healthy Balb / C mouse at 3, 7, and 12 minutes with a dose of 0.05 mmol / kg Fe(L4) at 4.7 T. Enhancement is shown in the bladder.

[0036] It is an object of the present disclosure to provide macrocyclic compounds capable of complexing Fe(III), as well as compositions and methods of making and using said compounds and complexes.

[0037] High-spin Fe(III) complexes with macrocyclic ligands may be used as T1 MRI contrast agents. In particular, high-spin Fe(III) has favorable paramagnetic properties that shorten the T1 relaxation time of water protons for MRI imaging through both inner- and outer-sphere interactions with water molecules.

[0038] Disclosed are Fe(III) coordination complexes for use as T1 MRI contrast agents. The disclosed Fe(III) T1 MRI contrast agents include macrocyclic ligands. Without intending to be bound by any particular theory, it is believed that the macrocyclic ligand controls the spin and oxidation state, and the anionic group controls the overall charge of the complex. The Fe(III) complexes can also be used as T2 MRI contrast agents.

[0039] When complexed with Fe(III), the macrocycles of the present disclosure (as ligands) are advantageous in achieving control over spin and oxidation state, as well as interactions with inner and outer sphere water. The cavity of these macrocycle ligands is suitable for stabilizing high spin forms of Fe(III). Also, control over aqueous solution chemistry can be achieved with these macrocycles. The macrocycle complexes described herein mostly encapsulate Fe(III), but in some cases have coordination sites for water ligands that enhance their effectiveness as T1 MRI contrast agents. In some cases, the inner sphere water ligands can cause T1 relaxivity of bulk water protons through second sphere interactions. The Fe-based MRI contrast agents described herein (macrocycles complexed with high spin, trivalent Fe(III)) generate contrast by the same paramagnetic mechanism as Gd(III) agents. Also, as coordination complexes, they are in small molecule form, i.e., they are not nanoparticles.

[0040] As used herein, unless otherwise specified, the term "group" or "moiety" refers to a chemical entity that is monovalent (i.e., has one end that can be covalently bonded to another chemical species), divalent, or polyvalent (i.e., has two or more ends that can be covalently bonded to other chemical species). Examples of groups include, but are not limited to, the following: [ka]

[0041] As used herein, unless otherwise specified, the term "alkyl" or "alkyl group" refers to a branched or unbranched saturated hydrocarbon group. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n- and isopropyl, n-, iso-, sec-, and tert-butyl groups. For example, alkyl groups include C1 to C6. 12(including all integer carbon numbers and ranges of carbon numbers therebetween). The alkyl group may be unsubstituted or substituted with one or more substituents. Examples of substituents include, but are not limited to, various substituents such as, for example, halogens (-F, -Cl, -Br and -I), aliphatic groups (e.g., alkyl groups, alkenyl groups, alkynyl groups), aryl groups, alkoxide groups, thioalkoxide groups, carboxylate groups, carboxylic acids, ether groups, and the like, and combinations thereof.

[0042] As used herein, unless otherwise indicated, the term "aryl" or "aryl group" refers to any of the C5 to C6 12 (including all integer carbon numbers and ranges of carbon numbers therebetween), aromatic or partially aromatic carbocyclic groups. An aryl group may also be referred to as an aromatic group. An aryl group may include, for example, fused ring or polyaryl groups, such as biaryl groups. An aryl group may be unsubstituted or substituted with one or more substituents. Examples of substituents include, but are not limited to, for example, halogens (-F, -Cl, -Br, and -I), aliphatic groups (e.g., alkenes, alkynes, etc.), aryl groups, alkoxides, thioalkoxides, carboxylates, carboxylic acids, ether groups, etc., and combinations thereof. Examples of aryl groups include, but are not limited to, phenyl groups, biaryl groups (e.g., biphenyl groups, etc.), and fused ring groups (e.g., naphthyl groups, etc.).

[0043] As used herein, unless otherwise stated, the term "aralkyl" refers to any group derived from an alkyl group by replacing one or more hydrogen atoms on the alkyl group with one or more aryl groups.

[0044] As used herein, unless otherwise specified, the term "heterocyclic group" refers to a C-C heterocyclic group that contains one or more heteroatoms (e.g., N, O, S, etc.) as part of the ring structure. 20 (For example, C3, C4, C5, C6, C7, C8, C9, C 10, C 11 , C 12、 C 13 , C 14 , C 15 , C 16 , C 17 , C 18 , C 19 , C 20 ) cyclic groups. Heterocyclic groups can be substituted or unsubstituted and / or have additional degrees of unsaturation. Heterocyclic groups can be fused rings (e.g., pyrrolidinyl groups, etc.). Non-limiting examples of heterocyclic groups include furanyl, oxazolyl, isothiazolyl, thiazolyl, tetrahydropyranyl, piperazinyl, dioxanyl, pyrrolidinyl, tetrahydrothiophenyl, tetrahydrofuranyl, quinuclidinyl, azaadamantanyl, decahydroquinolinyl, etc.

[0045] The present disclosure provides a macrocyclic compound or ring (macrocycle) having i) a macrocyclic core containing at least two heteroatoms as ligand donors, and ii) at least one pendant donor as a substituent on the macrocyclic core. The macrocyclic core has a ring structure containing carbon atoms and at least one heteroatom (e.g., N atom, O atom, or S atom). As used herein, "macrocyclic donor" refers to a heteroatom that has a lone pair of electrons available to donate to the Fe(III) center when present in the macrocyclic core of the compound. For example, the macrocyclic donor can be a nitrogen atom (e.g., tertiary amine, secondary amine), or an oxygen atom (e.g., ether). As used herein, "pendant donor", including anionic pendants and auxiliary pendants, refers to a heteroatom that has a lone pair of electrons available to donate to the Fe(III) center when present in a substituent on the macrocyclic core of the compound. For example, the pendant donor can be an oxygen-containing group (e.g., an alcohol, an oxide (e.g., an alkoxide or phenoxide), a sulfonate, a phosphinate, a phosphonate, etc.). Some pendant donors, such as alcohols, phosphinic acids, phosphonic acids, or sulfonic acids, can be deprotonated when complexed with Fe(III) or at a certain pH. Such protonated and deprotonated forms are within the scope of the present disclosure. In some embodiments, the macrocycle forms a complex with Fe(III) to provide a stabilized trivalent state (E0<0 mV vs. NHE). In certain embodiments of Schemes I and II, R1 can be an auxiliary group that does not bind Fe(III). Anionic groups can be added to auxiliary groups that do not bind Fe(III), including sulfonate, phosphinate, phosphate, phosphonate, or carboxylate groups.

[0046] The macrocyclic core may be a TACN moiety in which one or more of the N atoms are replaced with an O atom or a S atom.

[0047] In one embodiment, the macrocyclic ring has the structure (Scheme 1): [ka] Scheme I Where: X1, X2, X3 are N; W1 is O or S; Y1, Y2, Y3 are each independently: i) a pendant donor comprising O, where O has at least one lone pair, but preferably has two or three lone pairs (e.g., a ketone, an alcohol, an alkoxide, a phenol or phenoxide, a sulfonic acid, a phosphinic acid, or a phosphonic acid, or a deprotonated form thereof, such as an oxide, e.g., an alkoxide or a phenoxide); or ii) a pendant donor comprising N, where N has at least one lone pair of electrons (e.g., triazole, etc.); m1, m2, and m3 are each independently 1, 2, or 3; n1, n2, and n3 are each independently 1, 2, or 3; R1 is a substituted or unsubstituted aryl, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkyl, where each of the alkyl segments of the alkyl-Y chain (alkyl-Y1, alkyl-Y2, and / or alkyl-Y3) can be independently substituted or unsubstituted. In another embodiment, any or all of alkyl-Y1, alkyl-Y2, and alkyl-Y3 can each independently be any of Structures 1-9 defined in Scheme III.

[0048] In certain embodiments, R1 is not substituted with a pendant donor.

[0049] In some embodiments, the macrocyclic ring may have the following structure (Scheme II): [ka] Scheme II where R1 is substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl, or substituted or unsubstituted alkyl, where if the macrocyclic ring has structure I, Z1 is H or one of the pendant groups of Scheme III, and Z2 and Z3 are each independently one of the pendant groups of Scheme III; where if the macrocyclic ring has structure II or III, Z1 and Z2 are each independently one of the pendant groups of Scheme III; and where for all structures I-III, each of Z1, Z2, Z3, where applicable, are selected independently of each other. This paragraph is hereafter referred to as "Scheme II."

[0050] In some embodiments, when the macrocycle of Scheme II is complexed with Fe(III), R1 is not coordinated to Fe(III).

[0051] In one embodiment, the macrocyclic ring as defined in paragraph

[0045] or according to Scheme I or II has at least one pendant donor on the macrocyclic core. For example, the pendant donor may have the following structure (Scheme III): [ka] Scheme III where R2 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group (which may be an aryl group) or a substituted ether; R3 is a substituted or unsubstituted alkyl or a substituted or unsubstituted aryl group, and R4 is a substituted alkyl (e.g., substituted with a hydroxyl or carboxylate group, etc.), or an unsubstituted alkyl, or a substituted or unsubstituted aryl group. Some pendant donors, such as alcohols, phosphinic acids, phosphonic acids, or sulfonic acids, may deprotonate when complexed with Fe(III) or at certain pH values. Such protonated and deprotonated forms are within the scope of the present disclosure. For example, the pendant donor may be an alkoxide, phosphinate, phosphonate, or sulfonate (as shown in Scheme IV). TIFF2024178308000005.tif35169 Scheme IV - Ionizable groups

[0052] In certain embodiments, the R 1 group (which may be a coordinating or non-coordinating auxiliary) of the macrocyclic ring of Schemes I and II may have a structure according to Scheme V. [ka] Scheme V where A and A' are each independently a linear or branched substituted or unsubstituted C1-C 12An alkyl group, or a proton, and Q1 is an aryl substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), an alkyl group substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), or an aralkyl group substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), where at least one of A or A' is an alkyl group substituted with an anionic group (e.g., an amino acid, particularly glycine, serine, or aspartic acid). Aminophosphinic acids and phosphate esters are preferred.

[0053] In one embodiment, Q1 is aralkyl and the alkyl portion of the aralkyl group is methyl (C1).

[0054] In some embodiments, the pendant donors of Scheme V (e.g., R1 in Schemes I and II) do not coordinate to the Fe(III) center. Without intending to be bound by any particular theory, it is believed that these pendants help to regulate the charge on the complex and aid in binding to serum albumin. In other embodiments, the pendant donors of Scheme V (e.g., R1 in Schemes I and II) coordinate to the Fe(III) center.

[0055] As previously mentioned, some pendant donors, such as alcohols, sulfonic acids, phosphinic acids, or phosphonic acids, may deprotonate when complexed with Fe(III) or in a solution with a more basic pH. The corresponding alkoxides, sulfonates, phosphinates, phosphonates are within the scope of this disclosure.

[0056] A particular pendant may have more than one N or O donor atom (eg, triazole, or phosphonate, or phosphinate), but generally only one is coordinated to the metal ion.

[0057] When two or more pendant donors are present, they may be the same or different. In various examples, when two or more pendant donors are present, the individual pendants may be the same or different.

[0058] The macrocycle may include one or more auxiliary pendant groups, which may be one or more coordinating auxiliary pendant groups and / or one or more non-coordinating auxiliary pendant groups.

[0059] Non-coordinating auxiliary pendant groups do not have heteroatoms that can bind to Fe(III) metal ions to form 5- or 6-membered chelates. Non-limiting examples of non-coordinating auxiliary pendant groups include benzyl groups, phenyl groups, and other aromatic (e.g., aryl) groups with one or more methylene groups or no methylene groups attached to the aromatic group, alkyl groups (both branched and straight chain groups), and the like. Other non-limiting examples of non-coordinating auxiliary pendant groups include biphenyl, naphthyl, anthracenyl, pyridyl, quinolyl, methyl, ethyl, isopropyl, n-propyl, ethyl methoxy ether, PEG derivatives (polyethylene glycol), and the like.

[0060] Non-limiting examples of coordinating auxiliary pendant groups (e.g., the third pendant group when two are hydroxypropyl, phosphinate, or phosphonate) include oxygen or nitrogen donors that form five- or six-membered chelates, such as, for example, amides, carboxylates, alcohols, or phenols, or derivatives of triazoles, imidazoles, pyrazoles, picolyls, pyridines, alkylamines, aminopyridines, aminophenols, anilines, etc. Some of these groups can deprotonate when bound to Fe(III).

[0061] Macrocyclic complexes containing one or more non-coordinating auxiliary pendant groups may have one or more open coordination sites (open coordination), which may be inner sphere water molecule(s), hydroxide(s), or a combination thereof. Macrocyclic complexes containing one or more coordinating auxiliary pendant groups may have no open coordination sites (closed coordination). In closed or open coordination, the macrocyclic complex may have second sphere water molecule(s).

[0062] In various examples, the macrocyclic core can have 2 or 3 nitrogen atoms, 0 or 1 oxygen atoms, and / or 0 or 1 sulfur atoms. For example, the macrocyclic core can have 6, 7, 8, or 9 carbons. For example, the macrocyclic core can have 9-12 atoms (including all ranges and integers therebetween), where at least one of the atoms in the macrocyclic core is a heteroatom, such as, for example, N. In another embodiment, at least two of the atoms in the macrocyclic core are heteroatoms, such as, for example, N. In various examples, there are 2 or 3 carbon atoms separating the heteroatoms in the macrocyclic core. One or more carbons in the macrocyclic core can be unsubstituted (e.g., -CH2-) or substituted (e.g., -CHR- or -CHRR-), provided that at least one carbon in the macrocyclic core is substituted with a pendant donor. For example, they can be substituted with the substituents disclosed herein. In another embodiment, the macrocyclic core comprises at least two heteroatoms, each of which is independently N or O, separated from each other by at least two carbon atoms.

[0063] In some embodiments, the pendant groups are covalently attached to the macrocyclic core (eg, to the nitrogen): in particular, TACN(I).

[0064] Non-limiting examples of macrocyclic compounds are shown in Schemes VI and VII below: [ka] [ka] [ka] [ka]

[0065] In some embodiments, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 6 of Scheme III where R3 is unsubstituted ethyl, Z3 is not structure 6 of Scheme III where R3 is unsubstituted ethyl. In further embodiments, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 6 of Scheme III where R3 is unsubstituted or substituted ethyl, Z3 is not structure 6 of Scheme III where R3 is unsubstituted or substituted ethyl. In additional embodiments, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 6 of Scheme III where R3 is unsubstituted alkyl, Z3 is not structure 6 of Scheme III where R3 is unsubstituted alkyl. In yet another embodiment, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 6 of Scheme III where R3 is unsubstituted or substituted alkyl, Z3 is not structure 6 of Scheme III where R3 is unsubstituted or substituted alkyl.

[0066] In certain embodiments, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 7 of Scheme III, Z3 is not structure 7 of Scheme III.

[0067] In certain embodiments, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R3 is alkyl with terminal hydroxyl substitution, Z3 is not structure 8 of Scheme III where R3 is not alkyl with terminal hydroxyl substitution. In further embodiments, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R3 is substituted alkyl, Z3 is not structure 8 of Scheme III where R3 is substituted alkyl.

[0068] In some embodiments, when the macrocyclic ring has structure (II) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R4 is alkyl with terminal hydroxyl substitution, R1 is not an alkyl with a terminal aryl group. In additional embodiments, when the macrocyclic ring has structure (II) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R4 is alkyl with terminal hydroxyl substitution, R1 is not a substituted alkyl.

[0069] In certain embodiments, Fe(III) is complexed with the macrocyclic ring. In other embodiments, Fe(III) is not complexed with the macrocyclic ring. Fe(III) can be complexed with the macrocyclic rings shown herein.

[0070] Without intending to be bound by any particular theory, it is believed that the macrocycles described herein, when binding Fe(III), can stabilize the trivalent iron (Fe(III)) state. Coordination geometries are designed for favorable binding of Fe(III) relative to Fe(II), e.g., to maintain the Fe(III) oxidation state under biologically relevant conditions. Stabilization of the Fe(III) state (E0<0mV vs. NHE) also serves to suppress the generation of reactive oxygen species resulting from reduction of the complex to the Fe(II) state.

[0071] The Fe(III) center is desirably stabilized relative to Fe(III) so that it does not react with biological reductants to generate reactive oxygen species (ROS). Such redox-inactive Fe(III) centers have a negative redox potential relative to NHE. Examples of macrocyclic complexes of the present invention having macrocyclic cores and pendant groups that generate stabilized Fe(III) include, but are not limited to, 1,4,7-triazacyclononane macrocyclic cores and alcohol pendant groups that are deprotonated upon binding of Fe(III).

[0072] In various examples, the macrocyclic compounds or compounds of the present disclosure exhibit a reduction potential (E0) of less than 0 mV versus the NHE in aqueous solution at a biologically relevant pH (e.g., pH 6.5-7.5 or 7.2-7.4). In various other examples, the macrocyclic compounds or compounds of the present disclosure exhibit a reduction potential (E0) of at least -100, at least -150, at least -200, at least -300, at least -400, at least -500, or at least -600 mV versus the NHE in aqueous solution at a biologically relevant pH (e.g., pH 6.5-7.5 or 7.2-7.4). In various other examples, the macrocyclic compounds or compounds of the present disclosure exhibit a reduction potential (E0) in aqueous solution at a biologically relevant pH (e.g., pH 6.5-7.5 or 7.2-7.4) versus the normal hydrogen electrode (NHE) that is less than 0, more negative than -100, more negative than -150, more negative than -200, more negative than -300, more negative than -400, more negative than -500, or more negative than -600 mV.

[0073] In various other examples, the macrocyclic compounds or compounds of the present disclosure exhibit a reduction potential (E0) of less than 0 to -600 mV versus the NHE in aqueous solution at biologically relevant pH (e.g., pH 6.5-7.5 or 7.2-7.4). In various other examples, the macrocyclic compounds or compounds of the present disclosure exhibit a reduction potential (E0) of less than 0 to -600 mV versus the NHE in aqueous solution at biologically relevant pH (e.g., pH 6.5-7.5 or 7.2-7.4).

[0074] The shortening of the T1 relaxation time of water protons, T1 relaxivity, is promoted by both inner and outer sphere water. That is, in various examples, the macrocyclic complexes and compounds of the present disclosure include one or more pendant donor groups that can hydrogen bond to water through heteroatoms such as oxygen or nitrogen. Non-limiting examples of such pendant donor groups are pendant alcohol groups, phosphinates, and phosphonates that deprotonate to alkoxide groups (forming hydrogen bonds to second sphere water). Furthermore, in various examples, the macrocyclic complexes and compounds of the present disclosure include open coordination sites that bind water. These water ligands can ionize to form hydroxide ligands at neutral pH, as shown, for example, by pH potentiometric titration. It is desirable for the water ligands to exchange rapidly. Evidence of rapid water ligand exchange can be seen in the determination of the water ligands at various temperatures. 17 O NMR spectroscopy studies have shown that the reduced transverse relaxation time (T 2r )teeth 17 It is approximated by measuring the linewidth of the O resonance.

[0075] The chemical nature of the coordination of Fe(III) depends on the coordination number. The compounds of the present disclosure have donor groups that can be part of the macrocyclic core, also called macrocyclic donors, and donor groups can be part of the substituents on the macrocyclic core, also called pendant donors. In one embodiment, when Fe(III) is complexed to the compounds of the present disclosure, 4-7 donors are complexed to the metal ion center. In one embodiment, the macrocyclic core can have 2-4 donors and 1-4 (e.g., 2-4) pendant donors, including all combinations. In various embodiments, there are 2 macrocyclic donors and 3 pendant donors, 2 macrocyclic donors and 4 pendant donors, 3 macrocyclic donors and 1 pendant donor, 3 macrocyclic donors and 2 pendant donors, 3 macrocyclic donors and 3 pendant donors.

[0076] Scheme VIII presents several macrocyclic complexes (involving Fe(III)) that are within the scope of the present disclosure. [ka]

[0077] As used herein, a macrocyclic complex refers to a macrocyclic compound that is complexed with Fe(III). In some embodiments of the macrocyclic complex, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 5 of Scheme III, Z3 is not structure 5 of Scheme III.

[0078] In some embodiments of the macrocyclic complex, when the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R4 is unsubstituted aryl, Z3 is not structure 8 of Scheme III where R4 is unsubstituted aryl.

[0079] In one embodiment, the compounds of the invention can have two or more macrocyclic cores tethered together via aromatic (e.g., aryl) groups, macrocycles, polymers, dendrimers, proteins, peptides. [ka]

[0080] For tumor uptake and retention, the size of the molecules containing the contrast agent is important. Furthermore, the degree of T1 relaxivity increases proportionally to the number of iron complexes, and the size of the molecule, more precisely the rotational correlation time (τ c ), the use of multiple tethered macrocyclic complexes should enhance contrast. c Increased binding can also be achieved by binding to blood proteins, particularly human serum albumin (HSA). Certain ligand functional groups promote binding to human serum albumin (HSA). Typically, these include anionic and aromatic groups (e.g., aryl groups).

[0081] In various embodiments, the compounds of the present disclosure are salts, partial salts, hydrates, polymorphs, or stereoisomers, or compounds of the present disclosure, or mixtures thereof.For example, the compounds can exist as racemic mixtures, single enantiomers, single diastereomers, or mixtures of diastereomers.In certain embodiments, after metal complexation, the compounds exist as mixtures of diastereomers and / or conformers that can be measured by NMR.Diastereomers arise from the conformation of the macrocyclic core and the orientation of the substituents on the macrocyclic core.

[0082] The compounds of the present disclosure may have inner sphere water or hydroxide ligands. In one embodiment, the compound has one inner sphere ligand (q) that contributes to relaxivity as in Formula 1:

number

[0083] Equation 1 indicates that relaxivity has contributions from bound water (inner sphere, IS) and second sphere (SS) and (outer sphere) water. Equation 2 predicts that a larger number of bound water molecules and a faster ligand exchange rate constant (short lifetime (τm) of bound water) are favorable. In particular, r1, the parameter used to characterize relaxivity, is in the order of mM -1 s -1 It has units of T lobs (s -1 ) plot. A similar relationship exists for second sphere water, although the numbers and residence times are not well defined. The r1 and r2 relaxivities (from the T1 and T2 relaxation rate constants at 37°C and 4.7T) are summarized in Table 1. [Table 1]

[0084] The structures of certain complexes in Table 1 are shown below. [ka]

[0085] In particular, it is desirable for the ratio of T1 relaxivity to T2 (r1 / r2) of the macrocyclic complexes or compounds of the present disclosure to be as close to 1 (unity) as possible. By definition, r2, or transverse relaxivity, is always greater than r1, or longitudinal relaxivity. In various preferred examples, the Fe(III) contrast agents of the present disclosure have low r2, providing an r1 / r2 ratio close to 1, as shown, for example, in Table 1. In various examples, the macrocyclic complexes or compounds of the present disclosure have an r1 / r2 ratio between 0.3 and 1.0. These data show the suitability of TACN ligands, alcohol pendants and open coordination sites, for example in Fe(TASO), compared to complexes that do not have open coordination sites for mononuclear complexes, such as Fe(TOP). (See, for example, Table 1). However, pendant groups such as phosphonates and phosphinates are expected to have strong second sphere interactions that increase r1, as shown for Fe(TRAP-Ph) in Table 1.

[0086] Table 1 shows that the interaction of Fe(III) complexes with water molecules can enhance the relaxation of water protons. Without being bound to a particular theory, it is believed that the exchange of inner sphere water with bulk water is an important mechanism for proton relaxation. However, Fe(III) is a much smaller metal ion than Gd(III) (0.78 Å and 1.25 Å, respectively). The shorter M-H distance in the bound water of Fe(III) compared to Gd(III) suggests that the relative efficiency of second sphere and inner sphere contributions may be different for the two metal ion complexes.

[0087] Associated paramagnetic relaxation of water (1 / T 1m There are three mechanisms that contribute to the longitudinal relaxation, namely the scalar (contact) contribution, the dipole-dipole contribution, and the Curie spin relaxation. The most important of these for the longitudinal relaxation considered here is the dipole-dipole contribution (1 / T1DD). For field strengths above 1.5 T, 1 / T1DD is defined as shown in Equation 3, where S is the spin quantum number and ω H is the Larmor frequency of the proton, r MH is the metal ion-proton distance, γH is the gyromagnetic ratio of the proton, ge is the g-factor of the electron, μ B is the Bohr magneton, μ o is the dielectric constant of vacuum. In particular, 1 / T1DD increases with larger total spin (S) (higher relaxivity) which favors Gd(III) over Fe(III). However, the distance (r MH ) is shorter, especially for 1 / r 6 Considering the dependence, it is favorable for proton relaxation of Fe(III).

number

[0088] The correlation time (τ c ) is the lifetime of bound water (1 / τ m ), the rotational motion of the contrast agent (1 / τ R ) and the longitudinal relaxation of the unpaired electron (1 / T 1e ), which is influenced by a variety of processes including τ. Any of these three processes can contribute, but their importance depends on the strength of the magnetic field. Much of the literature has focused on the importance of these processes at low magnetic field strengths (<1 T). Under these conditions, rotational processes or electronic relaxation times may be limited, resulting in a τ m should be in a narrow range close to 10ns (k ex =10 8 s -1 However, at higher magnetic field strengths (≥1.5T), the optimal τ m Simulations indicate that T has a larger range (1-100 ns) and that the rotational motion should have intermediate values ​​between those of small molecules and proteins. 1e , i.e., the electronic relaxation time, is an important parameter. 1e arise from complexes with a high degree of symmetry, which can cause little zero-field splitting and lead to slow relaxation of electronic states. Also, the coordination sphere must favor the high-spin (S=5 / 2) and not the low-spin S=1 / 2 Fe(III). 1The defects in the H NMR spectrum are also consistent with high-spin Fe(III) efficiently relaxing water protons (Figure 6). The solution effective magnetic moment μ of 5.8 eff also coincides with the S=5 / 2 state.

[0089] The test to determine whether a metal complex has bound water is carried out at variable temperature. 17 The data in Figure 8 was obtained using a Varian 400 MHz NMR spectrometer with a broadband probe. 17 Since the O isotope is naturally abundant, each complex is H2 17 The NMR studies were carried out at various temperatures. For Fe(TASO), the temperature range was 298K to 340K. The temperature-dependent transverse relaxation data were fitted to various equations by least-squares fitting analysis using Scientist for Windows version 3.0. First, complexes with open coordination sites are known to follow the Swift-Connick equation shown in Equation 5a:

number

[0090] For the complexes tested over the temperature range for which data were recorded and analyzed, T 2m -1 and 1 / T 2os can be neglected and the Swift-Connick equation reduces to Equation 5b. Relatedly, because the reduced transverse relaxation rates are often very large, taking the natural logarithm on both sides of the equation allows for better scaling and simpler representation of the data, as shown in Equation 5c:

number

[0091] The inverse of the residence time of bound water and the chemical shift difference between bound water and bulk water are represented by Equations 6a and 6b, respectively:

number

[0092] In formula 6a, k ex is the rate constant for water exchange at the coordination site, which is the inverse of the residence time of bound water. b is the Boltzmann constant, h is the Planck constant, T is the absolute temperature, and ΔS ‡ and ΔH ‡ represent the activation entropy and enthalpy, respectively. In Equation 6b, g L is the isentropic Landé factor, μ bis the magnetic moment, S is the total spin state, B is the applied magnetic field, and (A / h) is the hyperfine coupling constant. In Equation 6b, the isentropic Landé factor, magnetic moment, spin state, magnetic field, and hyperfine coupling constant terms are integrated into a single parameter, which is solved in the processing of the data. This integration restricts Equation 6a to a simple inverse temperature dependence, the simplified constant being represented by the constant C. Using this method, the exchange rate constant of the bound water in Fe(TASO) was tested, as shown in Figure 8. Additional studies over a range of pH values ​​confirmed the lack of inner sphere ligands at neutral pH (Figure 13). The data compared Fe(CDTA), a complex with bound water, and Fe(DTPA), a complex lacking inner sphere water, revealing that Fe(TASO) lacks directly bound inner sphere water. Thus, the T1 relaxivity is caused by second and outer sphere water molecules.

[0093] The compounds of the present disclosure are thermodynamically stable and / or kinetically inert to dissociation. In one embodiment, the compounds are thermodynamically stable and kinetically inert to dissociation. In one embodiment, the kinetic inactivity of the compounds of the present disclosure can be described using the rate constant of dissociation. In one embodiment, the macrocyclic donor and the pendant donor 1) do not significantly dissociate from the metal center in the presence of 25 mM carbonate, 0.40 mM phosphate, 100 mM NaCl (pH 7.2) at neutral pH for up to 24 hours.

[0094] In one embodiment, Fe(III) is high spin S=5 / 2. A paramagnetic spin state is required for efficient T1 (longitudinal) relaxation. To keep Fe(III) in the high spin state, the ligand (or crystal) field splitting must not be too large. If the crystal field splitting is larger than the pairing energy, a low spin (S=1 / 2) state will result. Fe(III) is easily maintained in the high spin paramagnetic state with a range of ligand donor groups, especially those containing anionic oxygen or nitrogen donors.

[0095] It is desirable that the Fe(III) complex remain in the trivalent oxidation state and not be reduced by peroxides, superoxide, ascorbate, or glutathione at concentrations present in the extracellular medium of cells, such as mammalian cells (e.g., human cells). Usually, a redox potential more negative than zero mV (<0 mV) relative to the NHE is sufficient. If the complex is reduced to Fe(II) and Fe(II) complexes, and the complex has a positive redox potential relative to the NHE, reactive oxygen species can be generated. For example, [Fe(EDTA)] has a redox potential of approximately 300 mV and generates ROS as shown in the assay in Figure 7.

[0096] For use in the methods of the present disclosure, the compounds or complexes described herein can be administered as pharmaceutical preparations. Thus, they can be provided in various compositions and can be combined with one or more pharma- ceutically acceptable carriers. Some examples of pharma-ceutically acceptable carriers can be found in Remington: The Science and Practice of Pharmacy (2005) 21st Edition, Philadelphia, PA. Lippincott Williams & Wilkins. The compositions can be provided as liquid, solution, or solid, and can be combined with any suitable delivery form or vehicle, including but not limited to caplets, capsules, tablets, inhalants, or aerosols.

[0097] The composition of the present disclosure can be introduced into an individual using various methods known to those skilled in the art.These methods include, but are not limited to, intravenous, intramuscular, intracranial, intrathecal, intradermal, subcutaneous, and oral routes.In one embodiment, the composition is administered intravenously.

[0098] In certain embodiments, the complexes used in the methods of the present disclosure may have the following structure: [ka] [ka]

[0099] The required solubility of the complexes depends on their effectiveness in producing contrast. For an Fe(III)T1 contrast agent with good relaxivity, the complexes should be 100μ -2 A solubility of at least 1.5 mM is required. However, other additives such as, for example, human serum albumin (HSA) or meglumine may be used to increase solubility or increase relaxivity. In a non-limiting example, at 4.7 Tesla, a solubility of at least 1.5 mM is required. -1 s -1 Contrast agents with a relaxivity of 0.6 to 1.4 mM are considered to have good relaxivity when conjugated to human serum albumin in vitro. The addition of HSA (35 mg / mL) to some of the iron(III) complexes can give higher T1 relaxivities, as shown in Table 1. However, in vitro, contrast agents with moderate relaxivities (0.6 to 1.4 mM HSA) can give higher T1 relaxivities. -1 s -1 ) may produce good contrast in vivo if the contrast agent interacts with organs such as the kidney or liver. Solubility is generally measured in aqueous solution at approximately neutral pH (6.5-7.5) in 100 mM NaCl with 25 mM carbonate and 0.4 mM phosphate at 37°C. The dose of the composition used will necessarily depend on the needs of the individual to whom the composition of the present disclosure is administered. These factors include, but are not necessarily limited to, the individual's weight, age, sex, and medical history. Shown in Figures 9 and 10 are data from an in vivo MRI study conducted in mice. The contrast agent, Fe(TASO), was injected as 0.20 mL of 6.3 mM Fe(TASO) (10.5 mg HSA or 2 equivalents of meglumine).

[0100] In one aspect, the present disclosure provides a method of imaging using the macrocyclic compounds described herein. The imaging method employs magnetic resonance imaging methods. Examples of such methods include, but are not limited to, magnetic resonance imaging (MRI).

[0101] Specifically, when complexed with Fe(III), the macrocycles of the present disclosure can be used as T1 MRI contrast agents. These complexes can have properties that change with changes in pH. Such properties make these complexes useful, for example, for pH mapping, which allows for better therapeutic treatment of diseases such as cancer, stroke, and heart disease. When complexed with Fe(III), the macrocycles can also be used as T2 MRI contrast agents.

[0102] The imaging method of the present disclosure may be used to image a cell, tissue, organ, vasculature, or a portion thereof. The cell, tissue, organ, vasculature may be part of an individual. By "individual" is meant a human or an animal. In one embodiment, the present disclosure provides a method of obtaining an image of at least a portion of a cell, tissue, organ, or vasculature, comprising contacting the cell, tissue, organ, or vasculature with a compound of the present disclosure and imaging at least a portion of the cell, tissue, organ, or vasculature to obtain an image of the cell, tissue, organ, or vasculature portion. At least a portion of the cell, tissue, or organ may be alive or dead. Similarly, the individual may be alive or dead.

[0103] In one embodiment, the macrocycles can form complexes with Fe(III) and are used as T1 MRI contrast agents. This contrast is produced by T1 weighted imaging, which gives positive contrast to areas where the iron complexes accumulate. The complexes are high spin Fe(III) under biological reducing conditions with inner or outer sphere water interactions that decrease the T1 relaxation time of bulk water protons.

[0104] The following statements provide non-limiting examples of the macrocyclic complexes, macrocyclic compounds, and imaging methods of the present disclosure: statement 1 a 1,4,7-triazacyclononane (TACN) moiety or a substituted TACN moiety (e.g., an O-substituted TACN moiety or an S-substituted TACN moiety); one or more anionic pendant groups which are substituents on the TACN moiety and are independently selected from: [ka] wherein R2 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, which may be an aryl group, or a substituted ether; R3 is a substituted or unsubstituted alkyl, or a substituted or unsubstituted aryl group; R4 is a substituted alkyl (e.g., substituted with a hydroxyl or carboxylate group or the like), or an unsubstituted alkyl, or a substituted or unsubstituted aryl group; and Q1 is an aryl substituted with an anionic group (e.g., a carboxylate, a sulfonate, a phosphonate, a phosphate ester, or a phosphinate, etc.), an alkyl group substituted with an anionic group (e.g., a carboxylate, a sulfonate, a phosphonate, a phosphate ester, or a phosphinate, etc.), or an aralkyl group substituted with an anionic group (e.g., a carboxylate, a sulfonate, a phosphonate, a phosphate ester, or a phosphinate, etc.); and i) a TACN moiety or a substituted TACN moiety, and ii) a high spin Fe(III) cation complexed to at least one anionic pendant group substituent of the macrocycle (e.g., the TACN moiety or the substituted TACN moiety). or a salt, partial salt, hydrate, polymorph or stereoisomer thereof. statement 2 When the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 5 of Scheme III, then Z3 is not structure 5 of Scheme III; and / or When the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R4 is unsubstituted aryl, Z3 is not structure 8 of Scheme III where R4 is unsubstituted aryl. 2. The macrocyclic complex of claim 1. statement 3 3. The macrocyclic complex of claim 1 or 2, wherein at least one or all of the one or more pendant groups are covalently bonded to a nitrogen atom on the TACN moiety. statement 4 A macrocyclic complex according to any one of the preceding statements, wherein the macrocyclic complex has at least one open coordination site. statement 5 A macrocyclic complex according to any one of the preceding statements, wherein the macrocyclic complex has at least one water and / or at least one hydroxide complexed to a high spin Fe(III) cation. statement 6 At least one of the pendant groups is substituted at the benzylic position or at any carbon of the alkyl group connected to a heteroatom of the pendant group; , A macrocyclic complex according to any one of the preceding statements. statement 7 The macrocyclic complex of any one of the preceding statements, wherein the macrocyclic complex further comprises one or more auxiliary groups (e.g., one or more coordinating pendant groups, one or more non-coordinating pendant groups, or a combination thereof). statement 8 8. The macrocyclic complex of claim 7, wherein the coordinating or non-coordinating pendant group has the structure: [ka] where A and A' are each independently a linear or branched substituted or unsubstituted C1-C 12An alkyl group or a proton, and Q1 is an aryl substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), an alkyl group substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), or an aralkyl group substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), where at least one of A or A' is an alkyl group substituted with an anionic group (e.g., amino acid, particularly glycine, serine, or aspartic acid). Aminophosphinic acid and phosphate ester are preferred. In one example, O1 is an aralkyl, and the alkyl portion of the aralkyl group is methyl (C1). statement 9 The macrocyclic complex is TACN part containing two pendants selected from TIFF2024178308000024.tif40169, TACN portion including that selected from TIFF2024178308000025.tif42169 The macrocyclic complex of any one of the preceding statements, comprising: statement 10 The macrocyclic complex of any one of the preceding statements, wherein the TACN portion has one of the following structures: [ka] where X1, X2, and X3 are N; W1 is O or S; Y1, Y2, and Y3 are each independently i) a pendant donor comprising O, where O has at least one lone pair of electrons, but preferably has two or three lone pairs of electrons (e.g., a ketone, an alcohol, an alkoxide, a phenol or phenoxide, a sulfonic acid, a phosphinic acid, or a phosphonic acid, or a deprotonated form thereof, e.g., an oxide such as an alkoxide or phenoxide); or ii) a pendant donor comprising N, where N has at least one lone pair of electrons (e.g., triazole); m1, m2, and m3 are each independently 1, 2, or 3; n1, n2, and n3 are each independently 1, 2, or 3; R1 is a substituted or unsubstituted aryl, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkyl, where each alkyl segment of the alkyl-Y chain (alkyl-Y1, alkyl-Y2, and / or alkyl-Y3) can be independently substituted or unsubstituted. statement 11 The macrocyclic complex of any one of the preceding statements, wherein the TACN moiety or O-substituted TACN moiety has the structure: [ka] wherein R1 is a substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted alkyl, and Z1, Z2, Z3 are independently anionic pendants. statement 12 When the macrocyclic ring has structure I, Z1 is H or one of the pendant groups of Scheme III, and Z2 and Z3 are each independently one of the pendant groups of Scheme III; and / or When the macrocyclic ring has structure II or III, Z1 and Z2 are each independently one of the pendant groups of Scheme III; and / or For all structures I-III, each of Z1, Z2, and Z3 is independently selected when applicable. 12. The macrocyclic complex of claim 11. statement 13 The macrocyclic complex of any one of the preceding statements, wherein the TACN portion has one of the following structures: [ka] [ka] statement 14 14. The macrocyclic complex of any one of statements 1 to 13, wherein the macrocyclic complex has one of the following structures: [ka] [ka] statement 15 A compound or polymer comprising: a linker group or one or more macrocyclic complex groups covalently bonded to a polymer, dendrimer, protein or peptide, comprising one or more pendant macrocyclic complex groups covalently bonded to said polymer, said dendrimer, said protein or said peptide; A compound or polymer wherein each of the individual macrocyclic complex groups is derived from a macrocyclic complex according to any one of statements 1 to 14. statement 16 16. The compound or polymer of claim 15, wherein the compound comprises the structure: [ka] Statement 17 16. The compound or polymer of claim 15, wherein the compound has the structure: [ka] statement 18 A composition comprising one or more macrocyclic compounds according to any one of statements 1-14, and / or one or more compounds or polymers according to any one of statements 15-17, and a pharma- ceutically acceptable carrier. Statement 19 20. The composition of claim 18, wherein the composition further comprises human serum albumin and / or meglumine. statement 20 1. A method for obtaining an image of at least a portion of a cell, organ, vasculature, or tissue, comprising: contacting a cell, organ, vasculature, or tissue (or a portion thereof) with one or more macrocyclic compounds according to any one of statements 1-14, and / or one or more compounds according to any one of statements 15-17, and / or one or more compositions according to any one of statements 18-19, and / or Fe(NOTP) and / or Fe(TRAP-Ph); imaging at least a portion of the cell, organ, vasculature, or tissue to obtain an image of the cell, organ, vasculature, or portion of the tissue; A method wherein the image is obtained by using magnetic resonance. statement 21 21. The method of claim 20, wherein the cell, organ, vasculature, or tissue is part of an individual. statement 22 22. The method of claim 20 or 21, wherein the image is obtained using magnetic resonance imaging (MRI). statement 23 23. The method of any one of claims 20 to 22, wherein the macrocyclic compound and / or compound is a T1 agent(s). statement 24 a 1,4,7-triazacyclononane (TACN) moiety, or an O-substituted TACN moiety; and one or more anionic pendant groups which are substituents on the TACN moiety and are independently selected from: [ka] wherein R2 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, which may be an aryl group, or a substituted ether; R3 is a substituted or unsubstituted alkyl, or a substituted or unsubstituted aryl group, R4 is a substituted alkyl (e.g., substituted with a hydroxyl or carboxylate group or the like), or an unsubstituted alkyl, or a substituted or unsubstituted aryl group; and Q1 is an aryl substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate, etc.), an alkyl group substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate, etc.), or an aralkyl group substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate, etc.); or a salt, partial salt, hydrate, polymorph, or stereoisomer thereof. statement 25 When the macrocycle has structure (I) of Scheme II and Z1 and Z2 are structure 6 of Scheme III where R3 is an unsubstituted ethyl group, Z3 is not structure 6 of Scheme III where R3 is an unsubstituted ethyl group; and / or and / or if the macrocycle has structure (I) of Scheme II and Z1 and Z2 are structure 6 of Scheme III where R3 is an unsubstituted or substituted ethyl group, then Z3 is not structure 6 of Scheme III where R3 is an unsubstituted or substituted ethyl group; and / or if the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 6 of Scheme III where R3 is unsubstituted alkyl, then Z3 is not structure 6 of Scheme III where R3 is unsubstituted alkyl; and / or if the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 6 of Scheme III where R3 is unsubstituted or substituted alkyl, then Z3 is not structure 6 of Scheme III where R3 is unsubstituted or substituted alkyl; When the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 7 of Scheme III, Z3 is not structure 7 of Scheme III; and / or and / or if the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R3 is alkyl with terminal hydroxyl substitution, then Z3 is not structure 8 of Scheme III where R3 is not alkyl with terminal hydroxyl substitution; and / or and / or if the macrocyclic ring has structure (I) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R3 is substituted alkyl, then Z3 is not structure 8 of Scheme III where R3 is substituted alkyl; and / or When the macrocyclic ring has structure (II) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R4 is an alkyl with a terminal hydroxyl substitution, R1 is not an alkyl with a terminal aryl group; and / or When the macrocyclic ring has structure (II) of Scheme II and Z1 and Z2 are structure 8 of Scheme III where R4 is an alkyl with terminal hydroxyl substitution, R1 is not a substituted alkyl. 25. The macrocyclic compound of claim 24. statement 26 26. The macrocyclic compound of claim 24 or 25, wherein at least one or all of the one or more pendant groups are covalently bonded to a N on the TACN moiety. statement 27 At least one of the pendant groups is substituted at the benzylic position or at any carbon of the alkyl group connected to a heteroatom of the pendant group; 27. A macrocyclic compound according to any one of claims 24 to 26. statement 28 28. The macrocyclic compound of any one of claims 24-27, wherein the macrocyclic ring further comprises one or more auxiliary groups (e.g., one or more coordinating pendant groups, one or more non-coordinating pendant groups, or a combination thereof). statement 29 29. The macrocyclic compound according to claim 28: [ka] where A and A' are each independently a linear or branched substituted or unsubstituted C1-C 12 An alkyl group or a proton, and Q1 is an aryl substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), an alkyl group substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), or an aralkyl group substituted with an anionic group (e.g., carboxylate, sulfonate, phosphonate, phosphate ester, or phosphinate), where at least one of A or A' is an alkyl group substituted with an anionic group (e.g., amino acid, particularly glycine, serine, or aspartic acid). Aminophosphinic acid and phosphate ester are preferred. In one example, O1 is an aralkyl, and the alkyl portion of the aralkyl group is methyl (C1). statement 30 30. The macrocyclic compound of any one of claims 24-29, wherein the macrocyclic ring has one of the following structures: [ka] where X1, X2, and X3 are N; W1 is O or S; Y1, Y2, and Y3 are each independently i) a pendant donor comprising O, where O has at least one lone pair of electrons, but preferably has two or three lone pairs of electrons (e.g., a ketone, an alcohol, an alkoxide, a phenol or phenoxide, a sulfonic acid, a phosphinic acid, or a phosphonic acid, or a deprotonated form thereof, e.g., an oxide such as an alkoxide or phenoxide); or ii) a pendant donor comprising N, where N has at least one lone pair of electrons (e.g., triazole); m1, m2, and m3 are each independently 1, 2, or 3; n1, n2, and n3 are each independently 1, 2, or 3; R1 is a substituted or unsubstituted aryl, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkyl, where each alkyl segment of the alkyl-Y chain (alkyl-Y1, alkyl-Y2, and / or alkyl-Y3) can be independently substituted or unsubstituted. statement 31 31. The macrocyclic compound of any one of claims 24 to 30, wherein the macrocyclic ring has the structure: [ka] wherein R1 is a substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted alkyl; and Z1, Z2, and Z3 are independently anionic pendants; wherein when the macrocyclic ring has structure I, Z1 is H or one of the pendant groups of Scheme III, and Z2 and Z3 are each independently one of the pendant groups of Scheme III; or When the macrocyclic ring has structure II or III, Z1 and Z2 are each independently one of the pendant groups of Scheme III; and For all structures I-III, each of Z1, Z2, and Z3 is independently selected when applicable. statement 32 32. The macrocyclic compound of any one of claims 24 to 31, wherein the macrocyclic ring has the structure: [ka] [ka]

[0105] In this application, the use of the singular encompasses the plural and vice versa.

[0106] The macrocyclic compounds of the present disclosure can be prepared, for example, as described in the Experimental Details. The following examples are presented to illustrate the present disclosure. They are not intended to be limiting in any way. Those skilled in the art will recognize that routine modifications can be made to these embodiments that are intended to be within the scope of the present disclosure.

[0107] The method steps described in the various embodiments and examples disclosed herein are sufficient to carry out the method of the present disclosure. Thus, in one embodiment, the method consists essentially of a combination of the method steps disclosed herein. In another embodiment, the method consists solely of such steps.

[0108] Experimental details Measurement methods A Varian Inova 500 MHz NMR spectrometer equipped with an FTS Systems TC-84 Kinetics Air Jet Temperature Controller was used. 1 1 H NMR data was collected. 13 C NMR spectra were obtained using a Varian Mercury 300 MHz NMR spectrometer operating at 75 MHz. 17O NMR spectra were recorded on a Varian Inova 400 MHz spectrometer equipped with a 5 mm broadband probe operating at a resonant frequency of 54.24 MHz. All pH measurements were obtained by using an Orion 8115BNUWP Ross Ultra Semi Micro pH electrode connected to a 702 SM Titrino pH. Mass spectral data were collected using a ThermoFinnigan LCQ Advantage IonTrap LC / MS equipped with a Surveyor HPLC system. Absorbance spectra were collected using a Beckman-Coulter DU 800 UV-vis spectrophotometer equipped with a Peltier temperature controller. 1% H2 17 Samples were prepared in water containing 1000 nm. Chemical shifts and line widths at half maximum of the symmetric water peak were measured in the presence and absence of metal complexes at various temperatures and pH 6. Transverse relaxation times were calculated using the Swift-Connick equation (Eqs. 5-6) using the line widths at half maximum of the signals in the presence and absence of metal complexes at variable temperatures. All fits were derived from simultaneous least-squares fits of the measured data.

[0109] TASO To a 25 mL round bottom flask with a gas inlet and stir bar was added 0.100 g of TACN (1,4,7-triazacyclononane) (0.774 mmol) in a solution of 4 mL toluene·1 mL chloroform. 0.0920 g of N,N-dimethylformamide dimethyl acetal (0.774 mmol) was added to the flask. The solution was stirred at room temperature for 24 h. ESI-MS (m / z) of 1,4,7-triazatricyclo[5.2.1.04,10]decane (TACN-orthoamide), calculated: 140.1 [M+H +] (100%). The solution was dried by placing the flask on a rotary evaporator. The dried TACN-orthoamide and 15 mL of dry tetrahydrofuran (THF) were added to a 50 mL three-neck round-bottom flask equipped with a magnetic stir bar, reflux condenser, gas inlet tube, and addition funnel. 92.2 μL of benzyl bromide (0.774 mmol) was added to the flask, and the solution was stirred at room temperature overnight. The white-beige precipitate was collected by suction filtration and washed with dry THF (10 mL) and diethyl ether (10 mL). 7 mL of methanol and 7 mL of 12 M HCl were added to the precipitate in the flask for deprotection treatment. The solution was heated to reflux for 4 hours. After the solution was cooled to room temperature, NaOH pellets were added to bring the pH of the solution to 8. The solution was then filtered to remove the NaCl salt precipitate and extracted with chloroform (3×60 mL). ESI-MS(m / z), calculated value: 220.3[M+H + ] (100%). The solution was rotary evaporated and dissolved in 15 mL ethanol in a 25 mL round bottom flask containing 0.225 g S-propylene oxide (3.870 mmol) and stirred at room temperature for 24 h. The solution was rotary evaporated, dried under vacuum on a Schlenk line and dissolved in 10 mL methanol. %ESI-MS (m / z), calculated: 336.3 [M+H + ] (100%). Benzyl deprotection was performed with Pd / C (10%) catalyst. 30 mg of Pd / C (10%) in 5 mL of methanol and 1 mL of water was added to the ligand solution. The solution was deaired under argon gas for 30 min. Catalytic hydrogenation was carried out under hydrogen atmosphere at room temperature with vigorous stirring for 3 days. The mixture was filtered through Celite to remove the catalyst from the reaction solution, yielding (1,4,7-triazonane-1,4-diyl)bis(propan-2-ol) (DACO ligand). ESI-MS (m / z), calculated: 246.3 [M+H +] (100%). The solution was dried by placing the flask on a rotary evaporator. The DACO ligand was dissolved in 15 mL acetonitrile in a 25 mL round bottom flask. One equivalent of 1,3-propane sultone and N,N-diisopropylethylamine (DIEA) in 3 mL acetonitrile were added to the flask. The solution was stirred under reflux for 3 days. The solution was rotary evaporated and dried under vacuum on a Schlenk line. The purification process was carried out by a basic alumina column with MeOH / DCM solvent. The yield was calculated to be 37%. ESI-MS (m / z) (0.1% formic acid method), calculated: 368.3 [M+H + ](100%) and 390.3[M+Na + ](27%).

[0110] Fe(TASO) (see, for example, Figure 1) In a 25 mL round bottom flask equipped with a stir bar, TASO ligand (0.0589 g, 0.160 mmol) and 8 mL of ethanol were added. Then, FeCl2·4H2O (0.0318 g, 0.160 mmol) was dissolved in 2 ml of ethanol and added to the flask. The solution was stirred at room temperature for 2 days. A yellow precipitate was obtained. The precipitate was obtained by centrifugation and washed three times with diethyl ether. A yellow powder was obtained by removing the solvent by rotary evaporation. ESI-MS (m / z), calculated: 421.1 [M+H + ](100%) and 443.2[M+Na + ](55%), where M is the neutral form of Fe(TASO). The magnetic susceptibility of Fe(TASO), measured in aqueous solution using the Evans method, is 5.67 μeff.

[0111] NOTPMe (see, for example, Figure 4) 1,4,7-Triazacyclononane (3.1 mmol) was added to a two-neck flask. Paraformaldehyde (15.4 mmol, 5 equiv.) and triethyl phosphite (31 mmol, 10 equiv.) were added under an argon atmosphere. The reaction was stirred at 60° C. for 12 hours. Excess reactants were removed under reduced pressure. 0.50 g of the resulting material (hexaethyl((1,4,7-triazonane-1,4,7-triyl)tris(methylene))tris(phosphonate)) was weighed into a flask containing 2.5 mL of H2O. 1.25 g of sodium hydroxide pellets were added and the mixture was stirred until all of the sodium hydroxide was dissolved. Once dissolved, the mixture was refluxed for 15 minutes after which the flask was removed from the apparatus and 3 mL of H2O was added immediately after removal and then cooled to room temperature. After reaching room temperature, the flask was cooled in ice for an additional 15 minutes during which time crystals began to form. The solvent was removed and the crystals were then washed with water and a 1:1 mixture of ethanol and ethyl ether. ESI-MS: 494 [MH + ], 516[M+Na + ], where M is a neutral ligand (NOTPMe).

[0112] TRAP-H Synthesis (see, for example, Figure 3) Triazacyclononane (500 mg, 3.87 mmol) and paraformaldehyde (527 mg, 17.5 mmol) were dissolved in hypophosphorous acid (2.5 mL of 50 wt % aqueous solution, 23.2 mmol) in water (18.75 mL) and stirred at room temperature for 48 h. The reaction mixture was evaporated under vacuum with gentle heating below 40° C. The resulting oil was purified on a strong cation exchanger, DOWEX 50H+ foam, using water elution. Fractions containing the pure ligand (confirmed by ESI mass spectrometry on LCQ) were combined and the solvent was removed with gentle heating below 40° C. to give a clear oil (492 mg, 35%). MS (ESI, positive): m / z 364 [(TRAP-H)+H + ].

[0113] TRAP-Ph synthesis (see, for example, Figure 2) 1,4,7-Triazacyclononane (0.30 mmol) was added to a two-neck flask, which was attached to a reflux apparatus under an argon atmosphere. Dimethylphenylphosphonite (1.35 mmol, 4.5 equiv.) and paraformaldehyde (1.8 mmol, 6 equiv.) were then added to a flask containing 15 mL of dry tetrahydrofuran. The solution was refluxed for 16 h. Excess solvent was then removed under reduced pressure. ESI-MS: 634 [M+H + ].

[0114] The resulting TRAP-Ph-methoxy was then transferred to a duplicate next flask along with 4 mL of 50% w / v carbonate-free sodium hydroxide. The flask was attached to a reflux apparatus and refluxed for 30 minutes. 4 mL of distilled water was added and the solution was refluxed for another 30 minutes. After the second reflux, the reflux apparatus was removed and the solvent was allowed to evaporate until the two-phase system was reformed. The flask was then removed from the heat source and allowed to cool to room temperature. The supernatant oil was removed and dissolved in ethanol. The ethanol was evaporated to leave TRAP-Ph. The resulting product was purified by recrystallization in methanol, followed by acetone and then dichloromethane. ESI-MS: 590 [M+H + ], where M is the neutral form of TRAP-pH.

[0115] Fe(TRAP-Ph) (see, for example, Figure 2) TRAP-Ph was complexed with iron by mixing it with 1 equivalent of 0.01M iron(III) nitrate in methanol. The solution was stirred at room temperature for 4 days. The methanol was then evaporated to give the resulting product. ESI-MS: 645, 667 [M+Na + ].

[0116] 1,4,7-Triazacyclononane (0.15 mmol) was measured in a two-neck flask and set up on a reflux apparatus. Phosphorous acid (0.9 mmol, 6 equiv.) was further added to the flask along with 0.35 mL of hydrochloric acid and 1.0 mL of distilled water. Once the solution was refluxed, paraformaldehyde (0.675 mmol, 4.5 equiv.) was added to the solution over 1 h. After the addition of paraformaldehyde was complete, the solution was refluxed for an additional hour. The solution was cooled to room temperature and then slowly added dropwise to ethanol in an ice bath. After all the solution was added, the mixture was stirred for an additional hour, after which the solid was collected and washed with ether and ethanol. The solid was recrystallized in a small amount of hot water to give pure NOTP as a white solid. ESI-MS in negative mode: 410.2 [MH + ], where M is neutral NOTP.

[0117] NOTP was complexed to iron by combining it with 1 equivalent of 0.01 M aqueous iron(II) bromide. The solution was stirred at room temperature for 4 days, after which the water was evaporated. ESI-MS (negative mode): 465 [MH + ], where M is the neutral form of Fe(NOTP).

[0118] Synthesis of DRAP-H (see, e.g., FIG. 3) 1-Benzyl-1,4,7-triazacyclononane dihydrobromide (1.0 g, 2.64 mmol) and paraformaldehyde (0.24 g, 7.92 mmol) were dissolved in a mixture of 50% aqueous H3PO2 (1.3 mL, 11.9 mmol) and water (5 mL). The reaction mixture was stirred at room temperature for 24 h, then coevaporated three times with water and washed with a strong cation exchanger (DOWEX50, H + -form). The column was washed with deionized water and then an increasing NaCl gradient (5% to 10% by weight) was applied to collect the fractions with benzyl TRAP-H (monitored by MS). The eluate was evaporated to give a light brown oil. 1H NMR (300MHz, D2O): δ = 3.02-3.52 (m, ring-CH2, 12H and N-CH2-P, 4H), 4.35 (s, N-CH2-C6H5, 2H), 7.30-7.50 (m, -C6H5, 5H). MS (ESI, positive): m / z=376[M+H + ], where M is a neutral ligand.

[0119] Synthesis of DRAP-OH (Figure 3) DRAP-H was dissolved in 6 M HCl (20 mL). Paraformaldehyde (0.24 g, 7.92 mmol) was added and the solution was refluxed for 5 h (monitored by MS) and then evaporated to give crude benzyl DRAP-OH. MS (ESI, positive): m / z] = 436 [M+H + ]. M is a neutral ligand. Fe(NO3)3·9H2O and benzyl DRAP-OH were dissolved in 10 ml deionized water in a 1:1 ratio and stirred for 4 days (monitored using MS). MS (ESI, positive): m / z=489 [M + ], where M is a neutral Fe(III) complex.

[0120] A general method for "clicked" triazole pendants and their attachment to macrocycles (see, e.g., FIG. 5). 2 equivalents of sodium azide were added to the methanolic solution of the bromo / chloro reagent using a suitable sized round bottom flask. The solution was heated to 60°C and stirred for 4 hours. The next reaction step was carried out without isolation or purification of the previous product. 1.1 equivalents of propargyl alcohol were added to the stirred solution from the previous reaction. In a separate flask, 0.1 equivalents of copper sulfate hexahydrate and 0.2 equivalents of sodium ascorbate (in 2 mL of water) were combined. The mixture was stirred for 1 minute and then added to the previous reaction flask. The reaction mixture was stirred at 60°C for 8-12 hours or until complete (monitored by TLC). The reaction mixture was evaporated to dryness, water was added, and the product was extracted with EtOAc (3x). The organic layers were combined and dried over anhydrous sodium sulfate. The EtOAc was removed under vacuum to give the crude product. Purification was carried out by recrystallization in EtOAc / DCM solution at 0°C or on silica gel (25-50% EtOAc in hexanes). ESI-MS (m / z): 262.3 (product 1), 186.2 (product 2). Three equivalents of PBr3 were added to a DCM solution of the above product under Ar(g). After 12 h, the reaction was quenched with water and the product was extracted with DCM. The organic layers were combined and dried over anhydrous sodium sulfate. The DCM was removed under vacuum to give the crude product. Purification was performed by recrystallization in EtOAC / DCM solution at 0 °C or on silica gel (25-50% EtOAc in hexanes). ESI-MS (m / z): 323.1 / 325.1 (product 1), 247.1 / 249.1 (product 2).

[0121] The starting reagents were dissolved in acetonitrile and 1.5 equivalents of DIPEA were added. Stir for 8 hours or until complete (monitored by ESI-MS). The solvent was removed under vacuum and the crude product was purified on basic alumina (1-10% MeOH in DCM). ESI-MS (m / z): 489.6 (product 1), 413.5 (product 2).

[0122] The ligand from the previous reaction was dissolved in ethanol and 2 equivalents of KOH dissolved in water were added. Stirred for about 4 hours or until complete (monitored by ESI-MS). The solvent was removed under vacuum. Equal volumes of 1M HCl and DCM were added. The product was extracted with DCM (3x) and the layers were combined and dried over anhydrous sodium sulfate.

[0123] The ligand was dissolved in ethanol and 1 equivalent of FeCl2 was added with stirring at 60° C. After completion of the metallation (monitored by ESI-MS), diethyl ether was added until the product precipitated. The product was filtered, washed with diethyl ether and dried under vacuum.

[0124] ICP-MS Iron concentrations were measured using a Thermo X-Series 2 ICP-MS. All samples were diluted (1 μM) with 2% nitric acid to a total of 10 mL of aqueous solution and digested by heating (90 °C) for 24 h. For quantification, a linear calibration curve of iron metal ranging from 0.1 ppb to 250 ppb was generated daily. Samples were digested in nitric acid over a period of 4 days and iron concentrations were measured.

[0125] Magnetic moment Samples for magnetic moment testing using the Evans method were prepared with a coaxial NMR insert containing a diamagnetic standard of 5% t-butanol in D2O. The outer 5 mm NMR tube contained 5 mM paramagnetic complex with fixed concentrations of 4 mM, 8 mM, 40 mM, and 70 mM in the presence of 5% t-butanol. The effective magnetic moment (μ eff ,BM) were calculated at 298K (T) using the modified Evans method for small molecules.

[0126] Preparation of specimens for phantom MR imaging: Samples for phantom imaging experiments contained 50-500 µM of the complex, 20 mM HEPES and 100 mM NaCl. For samples containing human serum albumin (HSA), 35 mg of HSA was added to these solutions. The pH of all solutions was adjusted to 7.0.

[0127] Phantom (in vitro) imaging at 4.7T MRI acquisitions were performed using a General Electric 4.7T / 33 cm horizontal bore magnet (GE NMR instruments, Fremont, CA) incorporating AVANCE digital electronics (Bruker BioSpec platform with ParaVision v 3.0.2 acquisition software, Bruker Medical, Billerica, MA). Each complex was diluted to concentrations ranging from 0.05 mM to 400 mM with HEPES in 100 mM NaCl (pH 7.4) and imaged at 25 °C. T1 relaxation rates (r1) were obtained utilizing a saturation recovery, spin-echo (SE) sequence (with fixed echo time [TE], 10 ms and repetition times [TR] ranging from 75 to 8000 ms). Signal intensities at each repetition time were sampled by taking the average intensity within a region of interest (ROI) using commercial image processing software (Analyze 7.0, AnalyzeDirect, Overland, KS), and r1 and SMAX were calculated by nonlinear fitting of the equation using Matlab's Curve Fitting Toolbox (Matlab 7.0, MathWorks Inc, Natick, MA). The T1 relaxivity for each complex was then determined by obtaining the slope of the compound molar concentration-versus-r1 by linear regression fitting of the data. Similarly, T2 relaxation rates (R2) were acquired using a multi-echo, Carr-Purcell-Meiboom Gill (CPMG) SE sequence with a fixed TR of 2500 ms and TE times of 15-300 ms. R2 and SMAX were then calculated using the equation as described above. As described above, T2 relaxivity was determined by obtaining the slope of the concentration-versus-r2 via linear regression fitting of the data.

[0128] In vivo imaging in mice The efficacy of Fe(III) complexes for contrast enhancement in vivo was tested in a mouse model (BABC / cJ, Jackson Laboratory) at 4.7 T Bruker preclinical MRI. A sealed phantom was included for the imaging session for signal standardization. A scan was acquired before contrast administration to serve as a baseline value for enhancement. Two scanning protocols were used: (1) a T1-weighted, 3D, spoiled gradient echo scan covering the mouse rib cage to tail to measure signal enhancement, and (2) an inversion recovery, steady-state free precession scan (IR-SSFP) to measure T1 velocities in blood (inferior vena cava), kidneys, liver, gallbladder, and back muscles. Compounds were injected intravenously via the tail vein at doses of 50–200 μmol [Fe] / kg, and MR data were acquired continuously up to 1 h after injection to examine distribution and clearance kinetics. Mice were injected with 0.2 mL of 6 mM stock solution, 0.05 mmol / kg, 0.100 mmol / kg, or 0.200 mmol / kg. Additional scans were acquired 3 and 6 hours after injection to identify slower clearance rates through the biliary system. FDA approved MRI contrast agents: Gadopentetate dimeglumine (Gd-DTPA, Magnevist [登録商標] ) or Dotarem (Gd(DOTA)) were injected at 50 μmol [Gd] / kg into a separate cohort of mice for comparison. The data are shown in Figures 17 and 18. For the SPGR data set, signal intensity was normalized to the phantom and the signal enhancement for each organ was measured as well as the contrast-to-noise enhancement compared to the back muscle. Fe(III) concentration was estimated by calculating the increase in T1 velocity and dividing by the relaxivity value of the compound measured in vitro.

[0129] NOTP synthesis scheme [ka]

[0130] NOTP iron complex formation [ka]

[0131] FIG. 11 shows relaxivity data for examples of macrocyclic complexes of the present disclosure. Fe-NOTP has a relaxivity of 0.66±0.01 mM -1 s -1 The r1 of Fe-NOTP with HSA was 1.04 ± 0.06 mM -1 s -1 The r1 was shown.

[0132] NOTP was synthesized using a procedure similar to that found in the literature. The off-white precipitate was collected by vacuum filtration and then recrystallized multiple times from a 50:50 hot water:ethanol mixture until a pure white solid was formed. MS (ESI negative mode) m / z: 410.2 (MH + ). 1 H NMR(DO) 3.19 (6H, doublet, J 11.30) 3.42 (12H, singlet). 31 P NMR(DO) 11.95. 13 C NMR(D2O) 51.02(6C, singlet) 53.03(3C, doublet, J 141.61).

[0133] The purified NOTP ligand (0.33 mmol) was dissolved in water (20 mL) along with sodium hydroxide (1.01 mmol, 3 equiv). The solution was heated to 55° C. for 5 min. After 5 min, an aqueous solution (10 ml) of FeBr2 (0.33 mmol, 1 equiv) was added to the heated solution. The combined solution was heated for an additional 1 h. After cooling to room temperature, the solvent was evaporated under reduced pressure to give a yellow oil. The yellow oil was dissolved in water (2 mL) and ethanol (20 mL) was added to precipitate a yellow solid. The solid was collected and dried. MS (ESI negative mode) m / z: 463.2 (MH + ), where M is the neutral Fe(NOTP) complex. eff 5.85±0.14 ICP-MS Purity: 95% Log P of Fe-NOTP Octanol Water: -2.02±0.30

[0134] Synthesis of DAPO DAPO was synthesized as follows. [ka] 1,4,7-Triazonan-1,4-diyl-bis(propan-2-ol) was synthesized as previously published. 1,4,7-Triazonan-1,4-diyl-bis(propan-2-ol) (0.301 mmol) was dissolved in 500 μL of 3.3 M HCl solution. To this solution was added phosphorous acid (1.80 mmol, 6 equiv.) and the mixture was set to reflux. Once reflux was reached, paraformaldehyde (1.35 mmol, 4.5 equiv.) was added over 1 h, after which the solution was refluxed for an additional 24 h.

[0135] Synthesis of TRAP-POP TRAP-POP was synthesized as follows. [ka] Di-tert-butyl-1,4,7-triazacyclonane-1,4-dicarboxylate was synthesized as published in the literature. 0.566 mmol was dissolved in 1.1 mL of 3.3 M HCl along with phosphorous acid (1.98 mmol, 3.5 equiv). The solution was set to reflux and once reflux was reached, paraformaldehyde (1.13 mmol, 3 equiv) was added over 1 h. Once all the paraformaldehyde had been added, the solution was refluxed for an additional hour. MS-ESI: 224.1 [M+H + ]. The product from step 1 (1.52 mmol) was dissolved in 30 mL of MeOH and an inert atmosphere was created with argon. Dimethylphenylphosphonite (3.04 mmol, 2 equiv.) and paraformaldehyde (1.52 mmol, 1 equiv.) were added and the solution was stirred at room temperature for 16 h. The solvent was removed under reduced pressure. MS-ESI (negative mode): 557.7 [MH + ], where M is a neutral ligand.

[0136] Synthesis of NOTPMe NOTPMe was synthesized as follows. [ka] The synthesis was carried out as reported in the literature. ESI-MS: 494 [M+H + ], 516[M+Na + ] where M is a neutral ligand.

[0137] Photo Synthesis TPhOTO was synthesized as follows. [ka] PHOTO-Methoxy was synthesized by dissolving TACN-benzyl (0.74 mmol) in 30 mL of methanol. Dimethylphenylphosphonite (3.68 mmol, 5 equiv.) was added to the solution along with paraformaldehyde (2.94 mmol, 4 equiv.). The solution was refluxed under inert atmosphere for 16 h, after which the solvent was removed under reduced pressure. MS (ESI) + m / z: 556.2 (M+H + ) where M is a neutral ligand. The dried PhOTO-Methoxy was dissolved in 4 mL of 30% w / v carbonate-free sodium hydroxide. The solution was refluxed with vigorous stirring for 30 minutes at which point 4 mL of carbonate-free water was added. After the water was added, the solution was refluxed for an additional 30 minutes. At the end of the second reflux, the solution was heated to reduce the solvent volume until a two-phase system appeared. The flask was cooled to room temperature. The top layer (oil) was collected, dissolved in ethanol, and then evaporated to dryness. MS(ESI) - m / z: 526.4(MH + ), where M is a neutral ligand.

[0138] Synthesis of TOPA TOPA was synthesized as follows. [ka] 1-Benzyl-1,4,7-triazacyclononane was synthesized according to previously published procedures. 1-Benzyl-1,4,7-triazacyclononane (0.576 mmol) was measured into a two-neck flask and set up in a reflux apparatus. Phosphorous acid (6.91 mmol, 12 eq.) was further added to the flask along with 0.200 mL of hydrobromic acid and 0.538 mL of distilled water. Once the solution was refluxed, paraformaldehyde (1.15 mmol, 2 eq.) was added to the solution over 1 hour. After the addition of paraformaldehyde was complete, the solution was refluxed for 24 hours. The solution was then reduced to a minimum volume and diluted with Dowex H. + The product was loaded onto an ion exchange column. The column was first eluted with water to remove impurities, followed by elution of the product with 5% ammonium hydroxide solution. The fractions containing the ligand were dried under reduced pressure and dissolved in water. An Amberlite CG-50 Type 1 ion exchange column was used to obtain the product, which was eluted with water to give a white solid. MS(ESI) - m / z: 406.18(MH + ) where M is a neutral ligand. δ H( D2O ) 3.05 (4H, doublet, J 10.96) 3.32 (12H, multiplet) 4.34 (2H, singlet) 7.38 (5H, multiplet) δ P (D2O) 14.93

[0139] Bis(phosphonate)biphenyl TACN (TOBP) Starting from the biphenyl TACN derivative, a similar procedure was used as for the TOPA ligand. H( D2O ) (500MHz): doublet (2H, 7.704-7.687), doublet (2H, 7.644-7.628), doublet (2H, 7.601-7.585), triplet (2H, 7.452-7.421), triplet (1H, center 7.354), singlet (4.369, 2H). The broad resonance between 3.365 and 2.973 represents approximately the 21H. MS(ESI) m / z: 484.2 (MH +The Fe(III) complex was prepared by adding Fe(NO3)3 and refluxing overnight. MS(ESI) - m / z: 535.17(M - ) where M is the neutral Fe(TOBP) complex. [ka]

[0140] Synthesis of TRAP-OPO TRAP-OPO was synthesized as follows. [ka] 1,4,7-Triazabicyclo[5.2.1]decane (0.475 mmol) was dissolved in 10 mL of methanol. An inert atmosphere was created and dimethylphenylphosphonite (0.095 mmol, 0.2 equiv.) was added along with paraformaldehyde (0.118 mmol, 0.25 equiv.). The solution was stirred overnight at room temperature and the solvent was removed under reduced pressure. MS-ESI: 310.2 [M+H + ] where M is a neutral ligand. Dry methyl((1,4,7-triazabicyclo[5.2.1]decan-4-yl)methyl)(phenyl)phosphinate (0.221 mmol) was dissolved in 400 μL of 3.3 M HCl and phosphorous acid (1.11 mmol, 5 equiv.) was added. The solution was set to reflux and once reflux was reached, paraformaldehyde (0.442 mmol, 2 equiv.) was added over 1 h. After addition of paraformaldehyde was complete, the solution was refluxed for an additional hour. MS-ESI (negative mode): 470.5 [MH + ], where M is a neutral ligand.

[0141] Synthesis of TRAP-Ph TRAP-Ph was synthesized as follows. [ka] TRAP-Ph-methoxy was synthesized as previously reported. Dried TRAP-Ph-methoxy was dissolved in 4 mL of 50% w / v carbonate-free sodium hydroxide. The solution was refluxed with vigorous stirring for 30 minutes, at which point 4 mL of carbonate-free water was added. After the water was added, the solution was refluxed for an additional 30 minutes. At the end of the second reflux, the solution was heated to reduce the solvent volume until two phases appeared. The solution was cooled to room temperature and the top layer (oil) was removed, dissolved in ethanol, and then evaporated to dryness. TRAP-Ph was then purified by precipitation. Excess salt was removed by precipitating the salt with methanol. The methanol was removed under reduced pressure and acetone was added, forming another solid, which was recrystallized in dichloromethane. .MS(ESI) - m / z: 590.7(MH + ). 1 H NMR (DO, pD~0.9): 3.02 (12H, multiplet), 3.09 (6H, doublet, J 7.12), 7.31 (9H, multiplet), 7.48 (6H, multiplet) 31 P NMR(DO, pD~0.9) 29.27 The iron complex was synthesized according to a previously published procedure. MS(ESI) + m / z: 645.1 (M+H + ), 667.1(M+Na + ) where M is a neutral ligand. [ka] Synthesis of 1,3-bis((1,4,7-triazonan-1-yl)methyl)benzene To a 25 mL round bottom flask with a gas inlet and stir bar was added 0.100 g of TACN (0.774 mmol) in 4 mL of toluene·1 mL of chloroform solution. 0.0920 g of N,N-dimethylformamide dimethyl acetal (0.774 mmol) was added to the flask. The solution was stirred at room temperature for 24 h. 1,4,7-Triazatricyclo[5.2.1.0 4,10] ESI-MS (m / z) of decane (TACN orthoamide), calculated value: 140.1 [M+H + ](100%). The solution was dried by placing the flask on a rotary evaporator. The dried TACN orthoamide and 15 mL of dry acetonitrile were added to a 50 mL 3-neck round bottom flask equipped with a magnetic stir bar, reflux condenser, gas inlet tube and addition funnel. 0.100 g (0.384 mmol) of α,α'-dibromo-m-xylene in 10 mL of dry acetonitrile solution was added to the flask dropwise over 30 minutes via the addition funnel. The solution was heated to reflux for 2 hours and stirred at room temperature overnight. The white-beige precipitate was collected by suction filtration and washed with dry acetonitrile (5 mL) and diethyl ether (5 mL). 6 mL of methanol and 6 mL of 12 M HCl were added to the precipitate in the flask for deprotection treatment. The solution was heated to reflux for 4 hours. After the solution was cooled to room temperature, NaOH pellets were added to bring the pH of the solution to 8. The solution was then filtered to remove the NaCl salt precipitate and extracted with chloroform (3×60 mL). ESI-MS(m / z), calculated value: 361.4[M+H + ](100%), where M is a neutral ligand.

[0142] Synthesis of m-diTOPA 1,3-Bis((1,4,7-triazonan-1-yl)methyl)benzene (0.155 mmol) was dissolved in 500 μL of 3.3 M HCl and phosphorous acid (1.86 mmol, 12 equiv.) was added. The solution was attached to a reflux apparatus and once reflux conditions were achieved, paraformaldehyde (0.930 mmol, 6 equiv.) was added over 1 h. Once all the paraformaldehyde had been added, the solution was refluxed for an additional hour. MS-ESI - :735.3 [MH + ]. where M is a neutral ligand. [ka]

[0143] The Fe(TASO) complex was synthesized using iron(II) chloride tetrahydrate. The product was isolated as a yellow solid by diethyl ether washing in ethanol solvent. Fe content calculated by ICP-MS for NaFe(L1)Cl: 11.29%, found: 11.13% ± 0.17%. LCQ-MS: found m / z 421.2 (M+H + , 70%), m / z 443.2 (M+Na + , 30%), m / z 841.0 (2M+H + , 100%), and m / z 863.0 (2M + Na + , 18%). Here, M is neutral Fe (TASO complex). The effective magnetic moment was 5.68.

[0144] Fe(TASO) was characterized by cyclic voltammetry as shown in Figure 12. Cyclic voltammograms of a 1.0 mM solution of Fe(TASO) were obtained at various pH values ​​in water with potassium chloride (100 mM) and HEPES buffer as the supporting electrolyte.

[0145] Fe(TASO) was characterized by UV-Vis absorbance, and the data are shown in Figures 14-16.

[0146] TBzC esters Bis(2-hydroxypropyl)-1,4,7-triazacyclononane (0.245 g, 1.0 mmol) was dissolved in acetonitrile (5.0 mL) and heated to 60 °C. Anhydrous potassium carbonate (0.207 g, 1.5 mmol) was then added to the solution followed by ethyl 4-(bromomethyl)benzoate (0.304 g, 1.2 mmol). The reaction was stirred for 8-12 h until complete (monitored by ESI-MS). The solvent was then removed under vacuum and the crude product was purified over alumina with 0 / 100-5 / 95 methanol / dichloromethane and the product eluted with approximately 1 / 99 methanol / dichloromethane as a pale yellow oil (0.288 g, 71%). 1H NMR (500MHz, DCM-d2) δ7.98(d, J=10Hz, 2H), 7.49(d, J=10Hz, 2H), 4.35(dd, J=15Hz, 2H), 3.89(s, 2H), 3.72-3.68(m, 2H), 2. 88-2.76(m, 6H), 2.67-2.45(m, 10H), 2.25(dd, J=10Hz, 2H), 1.39(t, J=5Hz, 3H), 1.05(d, J=10Hz, 6H). 13 C NMR (75MHz, CHCl3-d) δ 167.0, 144.8, 129.5, 129.4, 128.9, 66.5, 63.9, 62.5, 60.8, 55.7, 55.4, 54.6, 19.8, 14.3. ESI-MS:m / z 408.3(M + , 100%), 430.3(M+Na + , 10%).

[0147] TBZC synthesis The TBZC ester (0.408 g, 1.0 mmol) was dissolved in ethanol (10.0 mL) and heated to 90 °C. NaOH (0.120 g, 3.0 mmol) was then added to the solution and the reaction was stirred for 12-24 h until completion was monitored by ESI-MS. The solution was washed with dichloromethane (3 x 25 mL) and the aqueous layer was collected. The solvent was removed under vacuum. The ligand was obtained by adding 12 M HCl until the solution was pH 3 and extracting the product (7) into dichloromethane (3 x 25 mL). The organic layers were then combined, dried over anhydrous sodium sulfate and the solvent removed under vacuum. The product was isolated as a pale yellow oil (0.278 g, 73%). 1 H NMR (500MHz, D2O) δ7.77(d, J=5Hz, 2H), 7.40(d, J=5Hz, 2H), 3.82(q, J=15Hz, 2H), 3.00(d, J=10Hz, 2H), 2.87-2.58(m, 16H), 1.04(d, J=5Hz, 6H). 13 C NMR (75MHz, D2O) δ 171.0, 140.4, 135.8, 129.7, 129.0, 63.6, 63.0, 60.2, 51.0, 49.7, 48.8, 19.7. ESI-MS: m / z 380.3(M+ , 100%).

[0148] Fe(TBZC) The complex was synthesized using ferrous chloride tetrahydrate and the product was isolated as a yellow solid (45.7 mg, 52%). Fe content by ICP-MS calculated for [Fe(H2-L4)Cl]Cl: Cl: 9.56%, found: 9.52% ± 0.10%. FT-ICR-MS: calculated m / z 514.198541, found m / z 514.198394 (M + , 100%) where M is a neutral Fe(TZBC) complex.

[0149] beside 17 O NMR relaxivity, ln(1 / T) as a function of temperature for Fe(L2) measured at pH 3.5 2r ) was measured for various examples of macrocycles of the present disclosure. The data is shown in FIG.

[0150] Relaxation values ​​of Fe(TASO) with and without HSA measured at 4.7T and 9.4T, pH 7.2 and 37°C. Compared to Gd(DTPA). Data are shown in Tables 2 and 3. [Table 2] [Table 3]

[0151] Fe(TASO) was used as the T1 contrast agent. T1 weighted MRI of a healthy Balb / C mouse at 4.7T with a dose of 0.2mmol / kg Fe(TASO) is shown in Figure 17. T1 weighted MRI of a healthy Balb / C mouse at 4.7T with a dose of 0.05mmol / kg Fe(TASO) is shown in Figure 18. Fe(TBZC) was used as the contrast agent and T1 weighted MRI is shown in Figure 19.

[0152] A pharmacokinetic study of Fe(TASO) was performed. Pharmacokinetic data in mice for Fe(TASO) are shown in Figures 19 and 20. T1-weighted MR images were acquired in healthy Balb / C mice at a dose of 0.05 mmol / kg Fe(L3) at 4.7 T. The time course of T1 rate constants for Fe(TASO), Gd(DOTA) and Gd-DTPA was determined in kidney, liver and blood of healthy Balb / C mice at 0.05 mmol / kg 4.7 T. Signal intensities were normalized to the phantom and the signal increase in each organ was measured and the increase in contrast-to-noise ratio was compared to muscle.

[0153] Although the present disclosure has been described with reference to one or more particular embodiments and / or examples, it will be understood that other embodiments and / or examples of the present disclosure are possible without departing from the scope of the present disclosure.

Claims

1. a 1,4,7-triazacyclononane (TACN) moiety or an O-substituted TACN moiety; one or more anionic pendant groups which are substituents on the TACN moiety or O-substituted TACN moiety and are independently selected from: 【Chemistry 1】 Here, R 2 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, or a substituted ether; R 3 is a substituted or unsubstituted alkyl or substituted or unsubstituted aryl group; R 4 is a substituted or unsubstituted alkyl, or a substituted or unsubstituted aryl group; and Q 1 is an anionic group-substituted aryl, an anionic group-substituted alkyl, or an anionic group-substituted aralkyl; and a high spin Fe(III) cation complexed to a TACN moiety and at least one anionic pendant group substituent of a 1,4,7-triazacyclononane (TACN) moiety or an O-substituted TACN moiety; or a salt, partial salt, hydrate, polymorph or stereoisomer thereof, 【Chemistry 2】

2. 2. The macrocyclic complex of claim 1, wherein at least one or all of the one or more pendant groups are covalently bonded to a nitrogen atom on the TACN moiety.

3. 2. The macrocyclic complex of claim 1, wherein the macrocyclic complex has at least one open coordination site.

4. 2. The macrocyclic complex of claim 1, wherein the macrocyclic complex has at least one water and / or at least one hydroxide complexed to a high spin Fe(III) cation.

5. 10. The macrocyclic complex of claim 1, wherein the macrocyclic complex further comprises one or more auxiliary groups.

6. 6. The macrocyclic complex of claim 5, wherein the one or more auxiliary groups are one or more coordinating pendant groups, one or more non-coordinating pendant groups, or a combination thereof.

7. 7. The macrocyclic complex of claim 6, wherein the coordinating or non-coordinating pendant groups independently have the structure: 【Chemistry 3】 where A and A′ are each independently a substituted or unsubstituted C 1 ~C 12 an alkyl group, or a proton, and at least one of A or A′ is an alkyl group substituted with an anionic group; and Q 1 is an aryl group substituted with an anionic group, an alkyl group substituted with an anionic group, or an aralkyl group substituted with an anionic group.

8. The macrocyclic complex is A TACN moiety comprising two pendants selected from: The TACN moiety includes those selected from:

2. The macrocyclic complex of claim 1 comprising:

9. 2. The macrocyclic complex of claim 1 , wherein the TACN moiety or O-substituted TACN moiety has the structure: 【Chemistry 6】 Where: R 1 is substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted alkyl, and Z 1 , Z 2 , Z 3 is independently an anionic pendant.

10. When the macrocyclic ring has the structure I, Z 1 is H or an anionic pendant group; Z 2 and Z 3 are each independently an anionic pendant group; and / or When the macrocyclic ring has structure II or III, Z 1 and Z 2 are each independently an anionic pendant group; and / or For all structures I-III, Z 1 , Z 2 , Z 3 Each of these is selected independently when applicable. The macrocyclic complex of claim 9.

11. 2. The macrocyclic complex of claim 1, wherein the TACN moiety has one of the following structures: 【Chemistry 7】 【Chemistry 8】 【Chemistry 9】 【Chemistry 10】

12. 2. The macrocyclic complex of claim 1, wherein the macrocyclic complex has one of the following structures: 【Chemistry 11】 【Chemistry 12】

13. A compound or polymer comprising: a linker group or one or more macrocyclic complex groups covalently bonded to a polymer, dendrimer, protein or peptide, comprising one or more pendant macrocyclic complex groups covalently bonded to said polymer, said dendrimer, said protein or said peptide; A compound or polymer, wherein each of the individual macrocyclic complex groups is derived from a macrocyclic complex according to any one of claims 1 to 12.

14. 14. The compound or polymer of claim 13, wherein the compound comprises the structure: 【Chemistry 13】

15. 14. The compound or polymer of claim 13, wherein the compound has the structure: 【Chemistry 14】

16. A composition comprising one or more macrocyclic compounds according to any one of claims 1 to 12, and / or one or more compounds or polymers according to any one of claims 13 to 15, and a pharma- ceutically acceptable carrier.

17. The composition of claim 16, wherein the composition further comprises human serum albumin and / or meglumine.

18. 1. A method for obtaining an image of at least a portion of a cell, organ, vasculature, or tissue, comprising: contacting a cell, organ, vasculature, or tissue with one or more macrocyclic compounds according to claim 1 and / or one or more compounds according to claim 13, or Fe(NOTP) or Fe(TRAP-Ph); imaging at least a portion of the cell, organ, vasculature, or tissue to obtain an image of the cell, organ, vasculature, or portion of the tissue; A method wherein the image is obtained by using magnetic resonance.

19. 20. The method of claim 18, wherein the cell, organ, vasculature, or tissue is part of an individual.

20. 20. The method of claim 18, wherein the images are obtained using magnetic resonance imaging (MRI).

21. The macrocyclic compound(s) and / or compound(s) are selected from the group consisting of T １ 20. The method of claim 18, wherein the agent(s) is / are an

22. a 1,4,7-triazacyclononane (TACN) moiety, or an O-substituted TACN moiety; and one or more anionic pendant groups which are substituents on the TACN moiety or O-substituted TACN moiety and are independently selected from: 【Chemistry 15】 Here, R 2 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group or a substituted ether; R 3 is a substituted or unsubstituted alkyl or substituted or unsubstituted aryl group; R 4 is a substituted or unsubstituted alkyl, or a substituted or unsubstituted aryl group; and Q 1 is an anionic group-substituted aryl, an anionic group-substituted alkyl, or an anionic group-substituted aralkyl; or a salt, partial salt, hydrate, polymorph, or stereoisomer thereof, comprising Where: 【Chemistry 16】 and / or 【Chemistry 17】 and / or 【Chemistry 18】 and / or 【Chemistry 19】 and / or 【Chemistry 20】 and / or 【Chemistry 21】 and / or 【Chemical 22】 and / or 【Chemistry 23】 and / or 【Chemistry 24】

23. 23. The macrocycle of claim 22, wherein at least one or all of the one or more pendant groups are covalently bonded to an N on the TACN moiety.

24. 23. The macrocyclic compound of claim 22, wherein the macrocyclic ring further comprises one or more auxiliary groups.

25. 25. The macrocycle of claim 24, wherein the one or more auxiliary groups are one or more coordinating pendant groups, one or more non-coordinating pendant groups, or a combination thereof.

26. 26. The macrocycle of claim 25, wherein the coordinating or non-coordinating pendant groups independently have the structure: 【Chemistry 25】 where A and A′ are each independently a substituted or unsubstituted C 1 ~C 12 an alkyl group, or a proton, and at least one of A or A′ is an alkyl group substituted with an anionic group; and Q 1 is an aryl group substituted with an anionic group, an alkyl group substituted with an anionic group, or an aralkyl group substituted with an anionic group.

27. 23. The macrocycle of claim 22, wherein the macrocycle has the structure: 【Chemistry 26】 Here, R 1 is substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted alkyl; Wherein when the macrocyclic ring has the structure I, Z 1 is H or an anionic pendant group; Z 2 and Z 3 are each independently an anionic pendant group; or When the macrocyclic ring has structure II or III, Z 1 and Z 2 are each independently a pendant group.

28. 23. The macrocyclic compound of claim 22, wherein the macrocyclic ring has the structure: 【Chemical 27】 【Chemistry 28】 【Chemical 29】 【Chemistry 30】

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