Bichromophoric compounds and their uses, notably in the study of metallo-biomedical agents

Abstract

The present invention concerns bichromophoric compounds and methods of preparation thereof. Said invention also concerns the uses of these compounds, notably in the study of metallo-biomedical agents, notably metallo-pharmaceuticals or metallo-contrast agents, in particular for the study of the biotransformations of metallo-biomedical agents, notably metallo-pharmaceuticals or metallo-contrast agents, more particularly to localize and / or quantify in vitro or in vivo the biotransformations of metallo-biomedical agents, notably metallo-pharmaceuticals or metallo-contrast agents.

Description

[0001] BICHROMOPHORIC COMPOUNDS AND THEIR USES, NOTABLY IN THE

[0002] STUDY OF METALLO-BIOMEDICAL AGENTS

[0003] The present invention concerns bichromophoric compounds and methods of preparation thereof. Said invention also concerns the uses of these compounds, notably in the study of metallo-biomedical agents. Said invention particularly concerns the study of the biotransformations of metallo-biomedical agents, more particularly to localize and / or quantify in vitro or in vivo the biotransformations of metallo-biomedical agents.

[0004] Metallo-biomedical agents biotransformation reactions are essential chemical processes, mainly mediated by enzymes, small redox active molecules (such as glutathione) or variation of physiological parameters (such as pH, oxygenation, or ionic strength), which lead to the formation of drug metabolites that are excreted from the body. This metabolism is known as a detoxification mechanism. However, these reactions which govern the pharmacological efficacy of the drugs, may in many cases, also be responsible for toxic unwanted effects. Due to the large variety of chemical structures, metallo-biomedical agents biotransformation involves numerous and sophisticated reaction mechanisms and metabolic pathways.

[0005] Knowing the biotransformations of a metallo-biomedical agent is therefore a necessary step in its design. Indeed, insufficient knowledge of these biotransformations slows down the metallo-biomedical agents development process and sometimes even leads to biomedical agents being withdrawn from the market.

[0006] In particular, metallo-biomedical agents, i.e. biomedical agents containing a metal (e.g. cisplatin), although having excellent potential for treating diseases with a poor prognosis, possess dative bonds that are reputed to be less stable than covalent bonds, and are likely to undergo biotransformations. For example, such a biotransformation occurs when cisplatin enters a cell and undergoes aquation involving loss of one or both chloride ligands. The newly formed complex can then interact with DNA.

[0007] Biotransformations of biomedical agents, which are a dynamic process, are generally studied using ex situ methods (fluid sampling and analysis by chromatography and spectroscopy).

[0008] However, a number of reviews have highlighted the urgent need to develop a different approach for in situ investigation of their biotransformations. In the case of metallo-biomedical agents, several groups have suggested studying these transformations by measuring variations in fluorescence of a coordinated fluorophore, but the proposed methods do not provide information on the quantification of these biotransformations, and their detection limit is relatively high.

[0009] Accordingly, it is an object of the present invention to provide new compounds that enable the quantification of the biotransformations undergone by metallo-biomedical agents in real time and with a low detection limit .

[0010] Another object of this invention is to provide new tools able to detect biotransformations that emcompass degradation of the metallobiomedical agent, transmetallation, transchelation, metal oxidation, and departure of a metal from a coordination sphere.

[0011] Another object of this invention is to provide new tools that make it possible to localize and / or quantify metallo-biomedical agents biotransformations in vitro or in vivo, for studying their dynamics.

[0012] Better understanding of the biotransformations undergone by metallo-biomedical agents is thus achievable thanks to the present invention. It enables an earlier go / no go decision-making and a quicker and more rational drug design to prevent deleterious biotransformations.

[0013] Thus, the present invention relates to a compound of the following formula (I):

[0014] DI-EI-(MBA)-E2-D2(I), wherein :

[0015] MBA is a metallo-biomedical agent, notably a metallo-pharmaceutical or a metallo-contrast agent, in which the metal is a metal M chosen from Co, Fe, Ni, Cu, Pt, Pd, Ru, Ir, Cr, and Mn; said metallo-biomedical agent MBA comprising at least one coordination moiety Zi constituted by or comprising at least one Ai coordinating atom, Zi being chosen from:

[0016] • -O’, -OH, or -ORa,

[0017] • -S’, -SH, or -SRa,

[0018] • -S(O)Ra, -S(O)2Ra, or -SO3,

[0019] • -Se’, -SeH, or -SeRa,

[0020] • -COO’, -COOH, or -COORa,

[0021] • -PRaRb or -P(O)RaRb, • -NH2, -NHRa or -NRaRb,

[0022] • carbens, in particular N-heterocyclic carbens, more particularly normal and abnormal N-heterocyclic carbens,

[0023] • heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, and

[0024] • aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, being substituted by at least one group R chosen independently from: o -O’, -OH, or -ORa, o -S’, -SH, or -SRa, o -S(O)Ra, -S(O)2Ra, or -SO3, o -Se’, -SeH, or -SeRa, o -COO’, -COOH, or -COORa, o -PRaRb or -P(O)RaRb, o -NH2, -NHRa or -NRaRb,

[0025] R being in particular -O’, -OH, or -ORa, more particularly -O’ or -OH, said aryl being in particular 2-HO-phenyl or 2-O’-phenyl,

[0026] Ra, Rb being independtly chosen from and Ci-Ce-alkyl groups, aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl;

[0027] Ei being bound to MBA by being covalently bound to Zi,

[0028] E2 being bound through the atom or group X when it exists or through Eaotherwise to MBA by being covalently bound to MBA;

[0029] Di and D2 are organic fluorophores, Di being different from D2;

[0030] Ei is a linker of following formula (Ila):

[0031] -(A)x-(B)y-(C)z- (Ila), in which : x, y and z are independtly 0 or 1, with x + y + z > 0,

[0032] A, B and C are independtly chosen from -C(R’)=C(R”)-, -C=C-, arene diyl groups, in particular benzene diyl, and heteroarene diyl groups, in particular triazole diyl or tetrazine diyl, with R’ and R” being independently chosen from H and Ci-Cs-alkyl groups; or Ei is absent;

[0033] E2 is a linker of following formula (lib):

[0034] -(X)i-Ea-(Y)j-(Eb)k- (lib), in which : i, j and k are independtly 0 or 1,

[0035] X is O or NRC, with Rcbeing chosen from H and Ci-Cs-alkyl groups,

[0036] Eaand Ebare independently chosen from Ci-Cn-alkane diyl groups, said groups being optionnaly interupted by one or more -O- and / or -NH- residues;

[0037] Y is chosen from O or NRC, with Re being chosen from H and Ci-Cs-alkyl groups, - NHCO-, -CONH-, -C(=O)-, -COO-, OC(=O), -C(R’)=C(R”)-, with R’ and R” being independently chosen from H and Ci-Cs-alkyl groups, -C=C-, maleimide diyl, arene diyl groups, in particular benzene diyl, and heteroarene diyl groups, in particular aza-heteroarene diyl groups, more particularly triazole diyl or tetrazine diyl.

[0038] In the framework of the present invention, the metal M is able to modulate the fluorescence of the two fluorophores, which are distinct from said metal.

[0039] Hence, the coordination moiety Zi can be the coordinating atom Ai or a residue comprising said coordinating atom Ai. As defiend above, Ai can be a O, S, Se, C, N or P atom. And said Zi can be a O, S, Se, C, N or P atom or a carbene comprising said atom, an heteroaryl comprising said atom, or an aryl or heteroaryl bearing said atom.

[0040] And the MBA corresponds in particular to the complex comprising the metal M, and the coordination moiety or moieties, and optionnaly halogens, water molecules, and / or solvent molecules completing the coordination sphere of the metal M.

[0041] By « metallo-biomedical agent », is notably meant a metallo-pharmaceutical or a metallo-contrast agent.

[0042] A “metallo-biomedical agent” refers in particular to a molecular compound where a metal atom is stabilized by one or more organic scaffolds termed ligands, and used for biomedical applications such as therapeutic agents for therapy or contrast agents for medical imaging.

[0043] By « metallo-pharmaceutical », is notably meant a metallo-drug, in particular an approved metallo-drug or a metallo-drug candidate.

[0044] By « metallo-biomedical agent », « metallo-pharmaceutical », « metallo-drug », « metallo-drug candidate » and « metallo-contrast agent », are in particular meant, respectively a biomedical agent, pharmaceutical, drug, drug and contrast agent, which contains a metal, for example as an active ingredient.

[0045] By « coordination moiety Zi» is in particular meant a coordinating atom Ai or a group of the metallo-biomedical agent comprising at least one Ai coordinating atom, which is bound to the metal M through at least one dative bond (also known as coordinate bond).

[0046] When the metallo-biomedical agent, in particular metallo-pharmaceutical or metallo- contrast agent MBA comprises more than one coordination moiety, the coordination moieties may or may not be bound together or to some of them, in particular through single bonds, double bonds, triple bonds, arene diyl, in particular benzene diyl, and heteroarene diyl groups, in particular triazole diyl or tetrazine diyl.

[0047] In particular, the at least one coordination moiety is bound to others, in particular one or two, coordination moieties, notably through single bonds, double bonds, triple bonds, arene diyl, in particular benzene diyl, and heteroarene diyl groups, in particular triazole diyl or tetrazine diyl.

[0048] E2 may be bound to MBA through Zi or through another of the coordination moiety when they are present.

[0049] In particular, E2 is bound to MBA through acoordination moiety that is not Zi.

[0050] By “organic fluorophores” is in particular meant that Di and D2 are intrinsic organic fluorophores, or are fluorescent when bound to Ei and E2 respectivelly.

[0051] In a prefered embodiment, Di and D2 display distinct excitation and / or emission wavelengths, in particular excitation and emission wavelengths.

[0052] Arene diyl groups and heteroarene diyl groups are in particular para-arene diyl groups and heteroarene diyl groups, respectively.

[0053] The coordination sphere of the metal M may be completed by halogens, ligands (as well known from the skilled in the art), in particular small ligands (as well known from the skilled in the art), for example CO, CN’, NO, water molecules, and / or solvent molecules.

[0054] In a particular embodiment, MBA comprises, further to Zi, n additional coordination moieties Z’, with n being chosen from 1, 2, 3, 4 or 5.

[0055] In a particular embodiment, the additional coordination moieties Z’ constituted by or comprising at least one A’ coordinating atom, Z’ being chosen from:

[0056] -O’, -OH, or -ORa,

[0057] -S’, -SH, or -SRa,

[0058] -S(O)Ra, -S(O)2Ra, or -SO3, • -Se; -SeH, or -SeRa,

[0059] • -COO; -COOH, or -COORa,

[0060] • -PRaRb or -P(O)RaRb,

[0061] • -NH2, -NHRa or -NRaRb,

[0062] • carbens, in particular N-heterocyclic carbens, more particularly normal and abnormal N-heterocyclic carbens,

[0063] • heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, and

[0064] • aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, being substituted by at least one group R chosen independently from: o -O -OH, or -ORa, o -S -SH, or -SRa, o -S(O)Ra, -S(O)2Ra, or -SO3, o -Se", -SeH, or -SeRa, o -COO; -COOH, or -COORa, o -PRaRb or -P(O)RaRb, o -NH2, -NHRa or -NRaRb,

[0065] R being in particular -O; -OH, or -ORa, more particularly -O' or -OH, said aryl being in particular 2-HO-phenyl or 2-O'-phenyl,

[0066] Ra, Rb being independently chosen from and Ci-Ce-alkyl groups, aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl.

[0067] In a particular embodiment, the additional coordination moieties Z’ are chosen from:

[0068] • carbens, in particular N-heterocyclic carbens, more particularly normal and abnormal N-heterocyclic carbens,

[0069] • heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, and

[0070] • aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, being substituted by at least one group R chosen independently from: o -O; -OH, or -ORa, o -S’, -SH, or -SRa, o -S(O)Ra, -S(O)2Ra, or -SO3, o -Se', -SeH, or -SeRa, o -COO’, -COOH, or -COORa, o -PRaRb or -P(O)RaRb, o -NH2, -NHRa or -NRaRb,

[0071] R being in particular -O', -OH, or -ORa, more particularly -O' or -OH, said aryl being in particular 2-HO-phenyl or 2-O'-phenyl,

[0072] Ra, Rb being independently chosen from and Ci-Ce-alkyl groups, aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl.

[0073] In a particular embodiment, Zi is chosen from:

[0074] • pyridinyl groups,

[0075] • carbens, in particular N-heterocyclic carbens, more particularly normal and abnormal N-heterocyclic carbens, and

[0076] • W-aryl groups, in particular W-phenyl group, wherein W is OH, SH, NH2 or PRa, with Rd being phenyl.

[0077] In a particular embodiment, Zi is chosen from:

[0078] • terpyridine, bis-terpyridine and their derivatives, in particular 2,2':6',2"-terpyridine and bis-2,2':6',2"-terpyridine;

[0079] • (carbene)(phenol)pyridine, in particular 2-(2-phenol)-6-(N-heterocyclic carbene)pyridine;

[0080] • bis(carbene)pyridine, bis-bis(carbene)pyridine and their derivatives, in particular 2,6-bis(normal N-heterocyclic carbene)pyridine, 2, 6-bi subnormal N-heterocyclic carbene)pyridine, bis-2,6-bis(normal N-heterocyclic carbene)pyridine, bis-2,6- bis(abnormal N-heterocyclic carbene)pyridine; and

[0081] • bis(phosphine)pyridine and their derivatives.

[0082] In a particular embodiment, Di and D2 are independently chosen from coumarine, carbazole, thieno[3,2-b]thiophene, triphenylamine, FsC-benzene, trifluoromethyl-benzene, anthracene, benzo[de]isoquinoline-l,3(lH,3H)-dione, BODIPY, rhodamines, cyanine3 amine, cyanine5 amine, cyanine? amine compounds, and their derivatives.

[0083] By “derivatives” is in particular meant that said compounds are substitued by at least a R’” group chosen from C1-C3 alkyl groups, aryls, in particular phenyl, heteroaryls, -OH, ORa, -NH2, -NHRa, -NRaRb, Ra and Rb being as defined above.

[0084] In a particular embodiment, M is Co, Fe, Ni, Cu, Pt, or Pd, in particular Fe, Co and Ru.

[0085] In a particular embodiment, Ei is a benzene diyl, in particular para-benzene diyl, or a thiophene diyl, in particular a 2,5- thiophene diyl.

[0086] In a particular embodiment, E2 is such as:

[0087] -(X)i-Ea-(Y)j-(Eb)k- (Hb),

[0088] • i, j and k are 1,

[0089] • X is O,

[0090] • Eais a Ci-Ci2-alkane diyl group, in particular a Ci-Cs-alkane diyl group,

[0091] • Eb is a Ci-Ci2-alkane diyl group, in particular a C2-Ci2-alkane diyl group, and / or

[0092] • Y is an arene diyl, in particular benzene diyl, or an heteroarene diyl, in particular a tri azole diyl group.

[0093] In another aspect, the present invention concerns the use of a compound of formula (I) as defined above, for the in vitro, ex situ or ex vivo study of the metallo-biomedical agent MBA, notably a metallo-pharmaceutical or a metallo-contrast agent.

[0094] In another aspect, the present invention concerns a method of in vitro, ex situ or ex vivo study of a metallo-biomedical agent MBA, notably a metallo-pharmaceutical or a metallo-contrast agent, comprising a step of fluorescence measurement related to a compound of formula (I) as defined above.

[0095] This fluorescence measurement may be performed by techniques that are well known from the skilled person in the art.

[0096] For example, the fluorescence spectra are recorded on a SAFAS-Xenius spectrometer (Monaco) and corrected for instrument response. Solutions of the samples are typically prepared freshly in ethanol at a concentration corresponding to an absorbance of 0.1 OD and analyzed at 20°C in a quartz cuvette with an optical pathlength of 10mm. As described in example 2, and in a typical experiment, Di is quenched (generally more than 95% quenched) when the MBA is untransformed while D2 acts as an internal standard.

[0097] When the MBA undergoes degradation, for example transchelation, fluorescence of Di is restored. In another aspect, the present invention concerns a compound of formula (I) as defined above, for its use in the in vivo study of the metallo-biomedical agent MBA, notably a metallo-pharmaceutical or a metallo-contrast agent.

[0098] DEFINITIONS

[0099] The following terms and expressions contained herein are defined as follows:

[0100] As used herein, a range of values in the form “x-y” or “x to y”, or “x through y”, include integers x, y, and the integers therebetween. For example, the phrases “1-6”, or “1 to 6” or “1 through 6” are intended to include the integers 1, 2, 3, 4, 5, and 6. Preferred embodiments include each individual integer in the range, as well as any subcombination of integers. For example, preferred integers for “1-6” can include 1, 2, 3, 4, 5, 6, 1-2, 1-3, 1-4, 1-5, 2-3, 2-4, 2-5, 2-6, etc.

[0101] As used herein, the term “alkyl” refers to a straight-chain, or branched alkyl group having 1 to 6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secbutyl, tert-butyl, pentyl, isoamyl, neopentyl, 1 -ethylpropyl, 3 -methylpentyl, 2,2- dimethylbutyl, 2,3 -dimethylbutyl, hexyl, etc. The alkyl moiety of alkyl -containing groups, such as aralkyl or O-alkyl groups, has the same meaning as alkyl defined above. Lower alkyl groups, which are preferred, are alkyl groups as defined above which contain 1 to 4 carbons. A designation such as “C1-C4 alkyl” refers to an alkyl radical containing from 1 to 4 carbon atoms. The term “alkyl” can also refer to a cycloalkyl, as defined below.

[0102] As used herein, the term “cycloalkyl” refers to a saturated or partially saturated mono- or bicyclic alkyl ring system containing 3 to 7 carbon atoms. A designation such as “C5-C6 cycloalkyl” refers to a cycloalkyl radical containing from 5 to 6 ring carbon atoms. Examples of cycloalkyl groups include such groups as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, pinenyl, and adamantanyl. The cycloalkyl moiety of cycloalkyl-containing groups, such as O-cycloalkyl groups, has the same meaning as alkyl defined above.

[0103] As used herein, the term “aryl” refers to a substituted or unsubstituted, mono- or bicyclic hydrocarbon aromatic ring system having 6 to 10 ring carbon atoms. Examples include phenyl and naphthyl. Preferred aryl groups include unsubstituted or substituted phenyl and naphthyl groups. Included within the definition of “aryl” are fused ring systems, including, for example, ring systems in which an aromatic ring is fused to a cycloalkyl ring. Examples of such fused ring systems include, for example, indane, indene, and tetrahydronaphthalene.

[0104] As used herein, the term “heteroaryl” refers to an aromatic group containing 5 to 10 ring carbon atoms in which one or more ring carbon atoms are replaced by at least one hetero atom such as -O-, -N-, or -S-. Examples of heteroaryl groups include pyrrolyl, furanyl, thienyl, pirazolyl, imidazolyl, thiazolyl, isothiazolyl, isoxazolyl, oxazolyl, oxathiolyl, oxadiazolyl, triazolyl, oxatriazolyl, furazanyl, tetrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, indolyl, isoindolyl, indazolyl, benzofuranyl, isobenzofuranyl, purinyl, quinazolinyl, quinolyl, isoquinolyl, benzoimidazolyl, benzothiazolyl, benzothiophenyl, thianaphthenyl, benzoxazolyl, benzisoxazolyl, cinnolinyl, phthalazinyl, naphthyridinyl, and quinoxalinyl. Included within the definition of “heteroaryl” are fused ring systems, including, for example, ring systems in which an aromatic ring is fused to a heterocycloalkyl ring. Examples of such fused ring systems include, for example, phthalamide, phthalic anhydride, indoline, isoindoline, tetrahydroisoquinoline, chroman, isochroman, chromene, and isochromene.

[0105] FIGURES

[0106] Figure 1 represents the 2D fluorescence spectrum of compound Fel-2 of example 1, according to the experiments of example 2.

[0107] Figure 2 represents the quenching of Di, while D2 acts as an internal standard, when the compound Fel-2 of example 1 is intact.

[0108] Figure 3 illustrates one of the possible degradations of a metallo-biomedical agent (MBA).

[0109] Figure 4 shows that the fluorescence of Di is restored when a degradation of the MBA occurs.

[0110] Figure 5 shows a representative example of emission spectra of an Fe(II) complex bearing a ^-conjugated fluorophore and the corresponding ligand, showing fluorescence quenching due to Fe(II)-induced photoinduced energy transfer. Figure 6 represents a representative example of emission spectra of a Fe(II) complex carrying a non-7t-conjugated bound fluorophore and the corresponding ligand, showing the significant maintenance of fluorescence due to the absence of photoinduced energy transfer by Fe(II).

[0111] EXAMPLES

[0112] Example 1: Synthesis of compounds of the invention

[0113] Synthesis of 7-azido-4-methylcoumarin: 7-Amino-4-methylcoumarin (1 equiv, 0.5 g) was dissolved in 3 M HCI (15 mL). The solution was cooled to 0 °C, and an aqueous solution of sodium nitrite (1.25 equiv, 0.25 g) was slowly added. The mixture was stirred for 30 min, followed by the addition of sodium azide (2 equiv, 0.37 g) in deionized water (10). After 3 h of stirring in the dark, the resulting brown solution was extracted with ethyl acetate (3 x 15 mL). The combined organic layers were washed with brine. Removal of the solvents resulted in 500.5 mg (87%) of 7-azido-4-methylcoumarin as a yellow-solid. 1H NMR (400 MHz, CDC13) 8 7.58 - 7.54 (m, 1H), 6.97 - 6.93 (m, 2H), 6.21 (q, J = 1.3 Hz, 1H), 2.41 (d, J = 1.3 Hz, 3H). HRMS (ESI-TOF) m / z [M+H]+Calcd for C10H10NO2 m / z 176.0706; Found: 176.0779.

[0114] 1) NaH 60% (1.2 equiv)

[0115] General protocol for the synthesis of azido-carbazoles: Carbazole (1 equiv, 0.5 g, 2.98 mmol) was dissolved in dry DMF (about 10 ml) in a roudlflask and cooled to 0°C, then 144 mg of NaH (.2 equiv, 11.96 mmol) was added to the solution. With the evolution of H2 gas, the colorless solution became turbid. After 45 minutes, 1.2 equivalent of dibromo alcane (5.98 mmol) was added to the mixture of solution and refluxed at 90 °C overnight. The reaction was stopped when by TLC no carbazole was observed and several new intense spots were observed. The mixture was purified by column chromatography by using silica gel cyclohexane as eluent, colorless solid or oil were obtained.

[0116] 1H NMR (400 MHz, CDCI3) 8 8.15 (d, J = 6.8 Hz, 1H), 7.51 (s, 2H), 7.30 (s, 1H), 4.51 (t, J = 6.5 Hz, 1H), 3.40 (t, J = 6.2 Hz, 1H), 2.45 (p, J = 6.4 Hz, 1H).

[0117] General protocol for the synthesis of azido-naphtalimides: 1H,3H- benzo[de]isochromene-l, 3-dione (1 equiv, 100 mg, 0.5 mmol) was added to a solution of 3- azidopropan-1 -amine (2 equiv, 142 mg, 1 mmol) in 10 mL of DMSO and heated at 80°C overnight. The mixture was further diluted with DI water, extracted with DCM (5x20 mL), washed with brine, MgSO4, filtered and dried under vacuum to afford the corresponding compound as a yellow oil. 8.51 (d, J = 7.4 Hz, 2H), 8.13 (d, J = 8.4 Hz, 2H), 7.67 (t, J = 7.9 Hz, 2H), 4.13 (m, 2H), 3.23 (t, J = 6.9 Hz, 2H), 1.72 (m, 2H), 1.59 (m, 2H), 1.43 (m, 2H). HRMS (ESI-TOF) m / z [M+H]+Calcd for C18H19N4O2 m / z 323.1503; Found: 323.1511.

[0118] General protocols for the synthesis of ‘always ON’ fragments

[0119] Synthesis of 1: In a round bottom flask, both [2,2':6',2"-terpyridin]-4'-ol (1 equiv, 50 mg, 0.2 mml) and K2CO3 (1.2 equiv, 33 mg, 0.24 mmol) were added to a solution of 5 mL of degassed DMF. Then, 3 -bromo- 1 -propyne (3 equiv, 89 mg, 0.6 mmol) was added to the mixture and further stirred at 90°C for 24h. The mixture was then diluted by DCM, washed by water and brine prior drying under vacuum. Finally, the desired product was isolated upon recrystallization in hot ethanol as fine off-white needles. 1H NMR (400 MHz, d6-DMSO) 5 8.77-8.69 (m, 2H), 8.63 (d, J = 7.9 Hz, 2H), 8.04 (s, 2H), 8.01 (td, 2H), 7.51 (ddd, 2H), 5.11 (d, J = 2.4 Hz, 2H), 3.72 (t, J = 2.4 Hz, 1H). HRMS (ESI-TOF) m / z [M+H]+Calcd for C18H14N3O m / z 288.1131; Found: 288.1144.

[0120] Synthesis of 2: In a Schlenk were added both the ligand (1 equiv) and FeCL precursor (0.5 equiv, 20 mg, 0.16 mmol), then three Argon-vacuum were made and 2 mL of dry methanol were added under vigorous stirring. The reaction mixture turning purple was allowed to proceed at room temperature over 30 min, then filtrated over a pad of celite, concentrated and precipitated by addition of Et2O. The precipitate was collected by filtration, washed by Et2O and dried under vacuum to afford the desired complex as a fine purple powder. 1H NMR (400 MHz, d6-acetone) 5 8.52 (s, 4H), 8.44 (d, J = 7.9 Hz, 4H), 7.87 (m, 4H), 7.14 (d, J = 5.2 Hz, 4H), 7.06 (m, 4H), 5.35 (d, J = 2.4 Hz, 4H).

[0121] General protocol for the synthesis of 3: In a brown tinted round bottom flask, were added the alkyne complex (1 equiv, 12 mg, 0.013 mmol) with the azide (2.8 equiv, 0.033 mmol), copper iodide (0.3 equiv, 1.54 mg, 0.016 mmol) and sodium L-ascorbate (0.6 equiv, 3.2 mg, 0.016 mmol) in 1 mL of DMF and further reacted for 4h to 12h depending on the azide.

[0122] Scoumarin: 1H NMR (400 MHz, d6-acetone) 5 9.16 (s, 2H), 9.06 (s, 4H), 8.81 (d, 4H), 8.07 (m, 8H), 7.96 (s, 2H), 7.55 (d, 4H), 7.27 (m, 4H), 6.45 (s, 2H), 6.03 s, 4H). HRMS (ESI- TOF) m / z [M]2+Calcd for Csel eFeNeCh m / z 315.0728; Found: 315.0746.

[0123] General protocols for the synthesis of ‘switch’ ligand General protocol for the synthesis of Tpy switch: In a round bottom flask, the benzaldehyde derivative (1 equiv, 1.9 mmol) is added with 2-acetylpyridine (2.2 equiv, 4.2 mmol) in 25 mL of ethanol. Then, KOH (2.5 equiv, 4.75 mmol) is slowly added at room temperature and followed by 20 mL of ammoniac. The mixture is allowed to react at room temperature under vigorous agitation for 24h until a heavy precipitate forms. The precipitate is concentrated by half under vacuum, filtrated and washed by a minimum of cold ethanol. The precipitate is then recrystallized in a CHCh-IhiO mixture affording the desired product as yellow needles.

[0124] 1H NMR (400 MHz, CDCI3) 6 7.33 (t, 2H, Har), 7.38 (d, 2H, Har), 7.44-7.52 (m, 4H,Har), 7.73 (d, 2H, Har), 7.91 (t, 2H, Har), 8.16 (m, 4H, Har), 8.71 (d, 2H, Har), 8.76 (d, 2H, Har), 8.66 (s, 2H, Har);13C NMR (CDCI3, 400 MHz, 25°C): 5 110.0, 119.0, 120.4, 120.5, 120.6, 121.6, 123.8, 124.1, 126.3, 127.6, 129.1, 137.1, 137.7, 138.7, 140.9, 149.4, 149.5, 156.3; HRMS (ESLTOF) m / z [M+H]+Calcd for C33H23N4 m / z 474.1800; Found: 475.1917.

[0125] 1) 2.1 eq 2,4-dimethylpyrrole,

[0126] Synthesis of TpyBODipy: In a Schlenk was added the 4-([2,2':6',2"-terpyridin]-4'- yl)benzaldehyde (1 equiv, 200 mg, 0.59 mmol), then three Argon-vacuum were made prior adding 381 mg of 2,4-dimethylpyrrole, 300 mL of dry DCM and 31 pL of TFA and stirred for 24h at room temperature. P-chloranil (1 equiv, 145 mg, 0.59 mmol) was added to the mixture and further stirred at room temperature over 4h. 3.8 mL of freshly distilled triethylamine were dropped to the mixture which was further stirred at room temperature for another 2h. Finally, 3.1 mL of BFs.EteO was dropped to the mixture and allowed to react for 24h. The mixture was washed by water, brine and dried by vacuum. Finally, the product was purified by chromatography over basic alumina with CHCh-cyclohexane to afford the desired product as an orange powder. 1H NMR (400 MHz, CDCI3) 8 8.79 (s, 2H), 8.74 (d, J = 4.1 Hz, 2H), 8.69 (d, J = 7.6 Hz, 2H), 8.00 (d, J = 8.02 Hz, 2H), 7.89 (dt, J = 7.8 Hz and 1.6 Hz, 2H), 7.44 (d, J = 8.2 Hz, 2H), 7.36 (m, 2H), 6.01 (s, 2H), 2.56 (s, 6H), 1.45 (s, 6H). General protocol for the synthesis of Tpyswitch: In a Schlenk were added both the ligand (1 equiv) and FeCh precursor (0.5 equiv, 20 mg, 0.16 mmol), then three Argon-vacuum were made and 2 mL of dry methanol were added under vigorous stirring. The reaction mixture turning purple was allowed to proceed at room temperature over 30 min, then filtrated over a pad of celite, concentrated and precipitated by addition of Et2O. The precipitate was collected by filtration, washed by Et2O and dried under vacuum to afford the desired complex as a fine purple powder.

[0127] Synthesis of 1: In a round flask charged with 2,6-di(lH-imidazol-l-yl)pyridin-4-amine (400 mg, 1.77 mmol) and lH,3H-benzo[de]isochromene-l, 3-dione (386 mg, 1.94 mmol), 6 mL of DMF was added and the reaction was heated at 150°C for 18h (overnight). After this time a precipitate insoluble (white off) was formed. To the mixture, EtOAc was added (15 mL) and the mixture was filtered through a glass funnel (#4) and washed with EtOAc (15mL) and Et2O (3x10 mL), obtaining 0.47 g (67%) white powder 1. 1H NMR (400 MHz, DMSO- d6) 5 8.77 (s, 1H), 8.64 (s, 1H), 8.62 (s, 1H), 8.10 (t, J = 1.5 Hz, 1H), 8.03 (s, 1H), 7.99 (t, J = 7.8 Hz, 1H), 7.21 (t, J = 1.3 Hz, 1H).

[0128] Synthesis of 2 (npthCNC): In a round flask with 1 (471 mg), 2 mL of DMF was added followed by the addition of Mel (2.4 equiv, 0.18 mL). The reaction was heated at 110°C overnight (18h) and covered with aluminum foil from light. After this time, the reaction was quenched by the addition of H2O (10-14 mL) and KPFe (1.1 equiv, 235 mg). The mixture was stirred for 5 min and the solid was filtered through a glass funnel (#3) and washed with Et2O (40 mL), recovering 0.75 g (89%) a with-off solid 2. 1H-NMR (400 MHz, ACN-d3) 5 9.51 (s, 1H), 8.65 (d, J = 7.3 Hz, 1H), 8.50 (d, J = 8.3 Hz, 1H), 8.15 (s, 1H), 8.07 (s, 1H), 7.92 (t, J = 7.8 Hz, 1H), 7.63 (s, 1H), 4.02 (s, 3H). 13C-NMR (100 MHz, ACN-d3) 5 163.95, 152.25, 146.99, 136.17, 136.14, 132.59, 132.27, 128.92, 128.06, 125.90, 122.54, 120.10, 116.62, 37.39. HRMS (ESI-TOF) m / z [M]2+Calcd for C25H19N6O2 m / z = 435.1572; Found: 435.1569.

[0129] Synthesis of [Fe(npthCNC)2]2+: In a schlenk with ligandnpthCNC (1 equiv, 50 mg) and FeCh (0.5 equiv, 4.36 mg) three Argon -vacuum were made, then 2 mL of DMF was added and stirred by 5 min at r.t., after this time KHMDS (2.4 equiv, 33 mg) was added. The reaction was stirred at room temperature overnight (dark red color). The next day a saturated solution of KPFe in water (10 mL) was added and filtered through a sintered glass funnel #4 and washed with Et2O (abundant, until it was a fine powder > 50 mL). To remove the unreacted ligand the mixture was added into a round flask in ACN (around 5 mL) and KHMDS was added (around 15 mg) the mixture was stirred for 5 min, then H2O (10 mL) was added and the mixture was extracted with CH2Q2 (3xl0mL). The organic fractions were mixed and dried over MgSCh, the solvent was removed under a vacuum. An alumina column was wade with eluent Et2O:ACN starting with mixture 10: 1 -> 3: 1 -> 1 : 1 -> ACN, the fractions with the complex were collected and evaporated affording 20 mg (12%) of a reddish solid [Fe(npthCNC)2]2+1H NMR (400 MHz, ACN-d3) 5 8.69 (dd, J = 7.3, 1.1 Hz, 1H), 8.52 (dd, J = 8.4, 1.1 Hz, 1H), 7.97 - 7.92 (m, 2H), 7.87 (s, 1H), 7.06 (d, J = 2.2 Hz, 1H), 2.73 (s, 3H). 13C NMR (100 MHz, ACN-d3) 5 200.64, 164.30, 155.11, 146.60, 135.96, 132.68, 132.14, 128.05, 127.37, 122.94, 117.28, 107.34, 35.12. HRMS (ESI-TOF) m / z [M]2+Calcd for C50H36N12O4 m / z = 43.1161; Found: 434.1175.

[0130] Synthesis of 1: In a round flask 2,6-dichloro-4-iodopyridine (1 equiv, 0.5 g), carbazole (1.1 equiv, 0.66 g), CS2CO3 (1 equiv, 0.31 g) and CU2O (0.1 equiv, 26 mg) were mixed in 10 mL of DMF, then the reaction was heated at 150°C overnight. The reaction was followed by TLC until the pyridine was consumed. The reaction was filtered through celite washing with CH2CI2. The mixture was purified by silica collumn with a mixture Hex:EtOAc (40: 1) + 1% Et3N. Obtaining a white solid in 0.51 g (45%). 1H NMR (400 MHz, CDCI3) 8 8.12 (d, J = 7.7 Hz, 1H), 7.58 (d, J = 6.3 Hz, 2H), 7.49 (ddd, J = 8.6, 7.1, 1.1 Hz, 1H), 7.38 (ddd, J = 7.9, 7.0, 0.7 Hz, 1H). 13C NMR (100 MHz, CDCI3) 6 152.27, 149.62, 139.04, 126.96, 124.81, 122.20, 120.91, 119.23, 109.94. HRMS (ESI-TOF) m / z [M+H]+Calcd for C17H10CI2N2 m / z = 313.0324; Found: 313.0299.

[0131] Synthesis of 2 (cbzCNC): In a round flask with 1 (1 equiv, 0.42 g) and N-methylimidazole (4.4 equiv, 0.47 mL) 0.5 mL of DMF was added. The reaction was stirred for 72h at 150 °C until a white-off solid appeared. The reaction was filtered washing with acetone. The isolated powder was dried under vacuum affording the desired compoundcbzCNC in 0.42 g (65%) yield. 1H NMR (400 MHz, MeOD4) 6 8.67 (s, 1H), 8.44 (s, 1H), 8.18 (d, J = 7.7 Hz, 1H), 7.92 (s, 1H), 7.87 (d, J = 8.8 Hz, 1H), 7.54 (t, J = 7.2 Hz, 1H), 7.42 (t, J = 7.7 Hz, 1H), 4.16 (s, 3H). 13C NMR (100 MHz, MeOD4) 6 153.65, 148.73, 140.08, 128.24, 126.16, 126.09, 123.70, 121.65, 120.91, 111.71, 111.40, 37.36. HRMS (ESI-TOF) m / z [M]2' Calcd for C25H22N6 m / z = 405.1833; Found: 405.1828.

[0132] Synthesis of [Fe(cbzCNC)2]2+: In a Schlenk with the ligandcbzCNC (1 equiv, 50 mg) and FeCh (0.5 equiv, 6.6 mg) three Argon -vacuum were made, then 2 mL of DMF was added and stirred by 5 min, after this time KHMDS (2.4 equiv, 50.3 mg) was added. The reaction was stirred at room temperature overnight. The next day a red-homogeneous mixture was quenched by the addition of KPFe in water (around 10 mL). The solid was filtered through a funnel #4 and washed with diethyl ether (3 x 15 mL). The solid was recovered with ACN and a neutral alumina column was made, starting with the mixture diethyl ether: ACN 3 : 1 to only ACN, the collected fractions afforded 27.4 mg (33%) red solid. 1H NMR (400 MHz, ACN-d3) 5 8.33 - 8.26 (m, 1H), 8.14 (s, 1H), 8.12 (d, J = 2.2 Hz, 1H), 7.94 (d, J = 8.3 Hz, 1H), 7.61 (ddd, J = 8.4, 7.2, 1.3 Hz, 1H), 7.50 - 7.45 (m, 1H), 7.09 (d, J = 2.1 Hz, 1H), 2.78 (s, 3H). 13C NMR (100 MHz, ACN-d3) 5 201.50, 125.36, 122.98, 121.68, 117.85, 111.92, 103.86, 35.87. HRMS (ESI-TOF) m / z [M]2+Calcd for CscTLoNnFe m / z = 433.1419; Found:

[0133] 434.1443.

[0134] General protocol for the synthesis of bichromophoric complex

[0135] General protocol for the synthesis of Fel-2: In an Eppendorf tube, were added both complexes Fel (1 equiv, 10 mg, 9.0 xl0'6mol) and Fe2 (1 equiv, 9.7 mg, 9.0 xl0'6mol) in 1 mL of deionized water. The mixture was incubated at 37°C for 2 days under stirring and purified by preparative HPLC (gradient EEO-MeOH with 0.02% TFA) to afford the desired complex Fel-2 as a purple powder.

[0136] 1H-NMR (400 MHz, MeOD) 5 9.55 (s, 2H), 9.13 (s, 1H), 8.97 (s, 2H), 8.86 (d, J = 7.6 Hz, 2H), 8.70 (t, J = 8.7 Hz, 4H), 8.23 (d, J = 7.8 Hz, 2H), 7.96-8.07 (m, 8H), 7.60 (d, J = 8.4 Hz, 2H), 7.51 (t, J = 7.6 Hz, 2H), 7.32-7.39 (m, 6H), 7.18-7.25 (m, 4H), 6.48 (d, J = 1.1 Hz, 1H), 6.02 (s, 2H), 2,57 (d, J=2.2 Hz, 3H). HRMS (ESI-TOF) m / z [M]2+Calcd for C61H42N10O3 m / z 509.1390; Found: 509.1438.

[0137] Example 2: Synthesis of other compounds of the invention and of homoleptic correspondents (1.1 equiv)

[0138] In a round flask charged with 2,6-di(lH-imidazol-l-yl)pyridin-4-amine (400 mg, 1.77 mmol) and lH,3H-benzo[de]isochromene-l, 3-dione (386 mg, 1.94 mmol), 6 mL of DMF was added and the reaction was heated at 150°C for 18h (overnight). After this time a precipitate insoluble (white off) was formed. To the mixture, EtOAc was added (15 mL) and the mixture was filtered through a glass funnel (#4) and washed with EtOAc (15mL) and Et2O (3x10 mL), obtaining 0.47 g (67%) white powder 2-(2,6-di(lH-imidazol-l-yl)pyridin- 4-yl)-lH-benzo[de]isoquinoline-l,3(2H)-dione (low solubility in everything). 1H NMR (400 MHz, DMSO-d6) 5 8.77 (s, 1H), 8.64 (s, 1H), 8.62 (s, 1H), 8.10 (t, J = 1.5 Hz, 1H), 8.03 (s, 1H), 7.99 (t, J = 7.8 Hz, 1H), 7.21 (t, J = 1.3 Hz, 1H).

[0139] In a round flask with 2-(2,6-di(lH-imidazol-l-yl)pyridin-4-yl)-lH-benzo[de]isoquinoline- l,3(2H)-dione (471 mg), 2 mL of DMF was added followed by the addition of Mel (2.4 equiv, 0.18 mL). The reaction was heated at 110°C overnight (18h) and covered with aluminum foil from light. After this time, the reaction was quenched by the addition of H2O (10-14 mL) and KPFe (1.1 equiv, 235 mg). The mixture was stirred for 5 min and the solid was filtered through a glass funnel (#3) and washed with Et2O (40 mL), recovering 0.75 g (89%) of npthCNC as a with-off solid. 1H-NMR (400 MHz, ACN-d3) 5 9.51 (s, 1H), 8.65 (d, J = 7.3 Hz, 1H), 8.50 (d, J = 8.3 Hz, 1H), 8.15 (s, 1H), 8.07 (s, 1H), 7.92 (t, J = 7.8 Hz, 1H), 7.63 (s, 1H), 4.02 (s, 3H). 13C-NMR (100 MHz, ACN-d3) 5 163.95, 152.25, 146.99, 136.17, 136.14, 132.59, 132.27, 128.92, 128.06, 125.90, 122.54, 120.10, 116.62, 37.39. HRMS (ESI-TOF) m / z [M]2+Calcd for C25H19N6O2 m / z = 435.1572; Found: 435.1569.

[0140] In a schlenk with ligandnpthCNC (1 equiv, 50 mg) and FeCh (0.5 equiv, 4.36 mg) three Argon-vacuum were made, then 2 mL of DMF was added and stirred by 5 min at r.t., after this time KHMDS (2.4 equiv, 33 mg) was added. The reaction was stirred at room temperature overnight (dark red color). The next day a saturated solution of KPFe in water (10 mL) was added and filtered through a sintered glass funnel #4 and washed with Et2O (abundant, until it was a fine powder > 50 mL). Then NMR, by NMR nothing conclusive, looks like it has Fe20s or something paramagnetic but the peak around 11 ppm of the unprotonated ligand was still observed plus two big signals around 4 and 3 ppm corresponding to the -CH3 of the pre-ligand and the complex. The complex was confirmed by Mass spectrometry. To remove the unreacted ligand the mixture was added into a round flask in ACN (around 5 mL) and KHMDS was added (around 15 mg) the mixture was stirred for 5 min, then H2O (10 mL) was added and the mixture was extracted with CH2CI2 (3xl0mL). The organic fractions were mixed and dried over MgSCU, the solvent was removed under a vacuum. NMR -> dirty, then a column was made. An alumina column was wade with eluent Et2O:ACN starting with mixture 10: 1 -> 3: 1 -> 1 : 1 -> ACN, the fractions with the complex were collected and evaporated affording 20 mg (12%) of a reddish solid [Fe(npthCNC)2]2+. 1H NMR (400 MHz, ACN-d3) 5 8.69 (dd, J = 7.3, 1.1 Hz, 1H), 8.52 (dd, J = 8.4, 1.1 Hz, 1H), 7.97 - 7.92 (m, 2H), 7.87 (s, 1H), 7.06 (d, J = 2.2 Hz, 1H), 2.73 (s, 3H). 13C NMR (100 MHz, ACN-d3) 5 200.64, 164.30, 155.11, 146.60, 135.96, 132.68, 132.14, 128.05, 127.37, 122.94, 117.28, 107.34, 35.12. HRMS (ESLTOF) m / z [M]2+Calcd for C50H36N12O4 m / z = 43.1161; Found: 434.1175.

[0141] In a round flask 2,6-dichloro-4-iodopyridine (1 equiv, 0.5 g), carbazole (1.1 equiv, 0.66 g), CS2CO3 (1 equiv, 0.31 g) and CU2O (0.1 equiv, 26 mg) were mixed in 10 mL of DMF, then the reaction was heated at 150°C overnight. The reaction was followed by TLC until the pyridine was consumed. The reaction was filtered through celite washing with CH2Q2. The mixture was purified by silica collumn with a mixture Hex:EtOAc (40: 1) + 1% EtsN. Obtaining 9-(2,6-dichloropyridin-4-yl)-9H-carbazole asa white solid in 0.51 g (45%). 1H NMR (400 MHz, CDCI3) 8 8.12 (d, J = 7.7 Hz, 1H), 7.58 (d, J = 6.3 Hz, 2H), 7.49 (ddd, J = 8.6, 7.1, 1.1 Hz, 1H), 7.38 (ddd, J = 7.9, 7.0, 0.7 Hz, 1H). 13C NMR (100 MHz, CDCI3) 6 152.27, 149.62, 139.04, 126.96, 124.81, 122.20, 120.91, 119.23, 109.94. HRMS (ESI-TOF) m / z [M+H]+Calcd for C17H10CI2N2 m / z = 313.0324; Found: 313.0299.

[0142] In a round flask with 9-(2,6-dichloropyridin-4-yl)-9H-carbazole (1 equiv, 0.42 g) and N- methylimidazole (4.4 equiv, 0.47 mL) 0.5 mL of DMF was added. The reaction was stirred for 72h at 150 °C until a white-off solid appeared. The reaction was filtered washing with acetone. The isolated powder was dried under vacuum affording the desired compoundcbzCNC in 0.42 g (65%) yield. 1H NMR (400 MHz, MeOD) 5 8.67 (s, 1H), 8.44 (s, 1H), 8.18 (d, J = 7.7 Hz, 1H), 7.92 (s, 1H), 7.87 (d, J = 8.8 Hz, 1H), 7.54 (t, J = 7.2 Hz, 1H), 7.42 (t, J = 7.7 Hz, 1H), 4.16 (s, 3H). 13C NMR (100 MHz, MeOD) 5 153.65, 148.73, 140.08, 128.24, 126.16, 126.09, 123.70, 121.65, 120.91, 111.71, 111.40, 37.36. HRMS (ESLTOF) m / z [M]2' Calcd for C25H22N6 m / z = 405.1833; Found: 405.1828.

[0143] In a Schlenk with the ligandcbzCNC (1 equiv, 50 mg) and FeCL (0.5 equiv, 6.6 mg) three Argon-vacuum were made, then 2 mL of DMF was added and stirred by 5 min, after this time KHMDS (2.4 equiv, 50.3 mg) was added. The reaction was stirred at room temperature overnight. The next day a red-homogeneous mixture was quenched by the addition of KPFe in water (around 10 mL). The solid was filtered through a funnel #4 and washed with diethyl ether (3 x 15 mL). The solid was recovered with ACN and a neutral alumina column was made, starting with the mixture diethyl ether : ACN 10: to 3: 1 to only ACN, the collected fractions afforded 27.4 mg (33%) of [Fe(cbzCNC)2]2+as a red solid. 1H NMR (400 MHz, ACN-d3) 5 8.33 - 8.26 (m, 1H), 8.14 (s, 1H), 8.12 (d, J = 2.2 Hz, 1H), 7.94 (d, J = 8.3 Hz, 1H), 7.61 (ddd, J = 8.4, 7.2, 1.3 Hz, 1H), 7.50 - 7.45 (m, 1H), 7.09 (d, J = 2.1 Hz, 1H), 2.78 (s, 3H). 13C NMR (100 MHz, ACN-d3) 5 201.50, 125.36, 122.98, 121.68, 117.85, 111.92, 103.86, 35.87. HRMS (ESI-TOF) m / z [M]2+Calcd for CscTLoNnFe m / z = 433.1419; Found:

[0144] 434.1443.

[0145] In a schlenk with 4-bromo-2,6-(diimidazol-l-yl)pyridine (400 mg, 1.38 mmol), 4- formylphenylboronic acid (228 mg, 1.52 mmol), K2CO3 (381 mg, 2.75 mmol) and Pd(dppf)2C12 (50.4 mg, 0.069 mmol) and PPI13 (36.1 mg, 0.138 mmol) in a degassed mixture 4: 1 of dioxane (20 mL) and water (5 X mL) were refluxed for 16 h. After cooling to room temperature and addition of water (25 mL), the mixture was extracted with CH2CI2 (3 x 10 mL). The combined organic layers were dried with MgSCh, filtered and concentrated, the solid-crude of 4-(2,6-di(lH-imidazol-l-yl)pyridin-4-yl)benzaldehyde (4- formylphenyl)b or onate was washed with copious amounts of n-hexane and it was used without further purification (400 mg, 89%).

[0146] In an oven-dried schlenk with 4-(2,6-dichloropyridin-4-yl)benzaldehyde (250 mg, 0.79 mmol) was dissolved in dry DCM (45 mL), and the solution was degassed with Argon for 15 min, To this solution 2,4-dimethyl-lH-pyrrole (158 pL, 1.66 mmol), followed by the addition of a few drops of TFA. The reaction was stirred at r.t for 24h. After this time, p- chloroanil was added (198 mg, 0.79 mmol) and stirred for 4H. Then, an excess of Et3N was added dropwise to the reaction mixture and stirred for 2h. Finally, 2mL of BF3°Et2O was added and let stirred for 24h at r.t. After this time, The reaction mixture was washed twice with 60 mL of NaHCO3(saturated solution) and once with brine (60 mL). The organic layer was dried over MgSCh and the solvent was removed under vacuum. After a silica column was made using the mixture DCM:MeOH (20: 1). To finally crystalize in a mixture by diffusion H2O:MeOH affording an orange-red fluorescent product BODIPY-im isolated in 25 mg (7%). 'H NMR (400 MHz, CDC13) 6 8.50 (s, 1H), 7.88 (d, J = 8.3 Hz, 1H), 7.77 (d, J = 1.5 Hz, 1H), 7.54 (t, J = 7.9, 3.7 Hz, 2H), 7.28 (d, J = 1.5 Hz, 1H), 6.02 (s, 1H), 2.58 (s, 3H), 1.44 (s, 3H).13C NMR (100 MHz, CDC13) 6 156.18, 154.32, 149.16, 142.74, 139.91, 137.47, 137.43, 135.20, 131.20, 129.57, 127.81, 121.61, 116.30, 107.90, 14.71.19F NMR (375 MHz, CDC13) 6 -146.17 (dd, J = 65.7, 32.5 Hz). HRMS (ESI-TOF) m / z [M+H]+Calcd for C30H26BF2N7 m / z = 534.2394; Found: 534.2376.

[0147] In a round flask charged with 4 (25 mg, 0.47 mmol) and MeOTf (23 pL, 0.14 mmol), in 1.5 mL of DMF was added and the reaction was heated at 50°C for 18h (overnight). After this time, a saturated solution of KPFe was added and the solid was filtered through a glass funnel (#3) and washed with Et2O (3 x 15 mL) obtaining 21 mg (53%) orange-powderBODIPYCNC. 1H NMR (400 MHz, ACN-d3) 8 9.51 (s, 2H), 8.29 (t, J = 2.0 Hz, 2H), 8.21 (s, 2H), 8.13 (d, J = 8.3 Hz, 2H), 7.69 (d, J = 8.3 Hz, 2H), 7.65 (t, J = 1.9 Hz, 2H), 6.14 (s, 2H), 4.03 (s, 6H), 2.52 (s, 6H), 1.48 (s, 6H). 13C NMR (101 MHz, ACN-d3) 6 156.67, 156.55, 146.84, 144.01, 141.43, 138.30, 136.46, 136.09, 131.56, 130.21, 129.13, 125.85, 122.16, 120.16, 113.25, 37.44, 14.43. HRMS (ESI-TOF) m / z [M]2+Calcd for C32H32BF2N7 = 281.6381; Found:

[0148] 281.6385.

[0149] In a schlenk with ligandBODIPYCNC (18.5 mg, 0.021 mmol) and FeCh (1.34 mg, 0.0106 mmol) three Argon-vacuum were made, then 1 mL of DMF was added and stirred by 5 min at r.t., after this time KHMDS (10.3 mg, 0.051 mmol) was added. The reaction was stirred at room temperature during 2h. Then, a saturated solution of KPFe in water (10 mL) was added and filtered through a sintered glass funnel #3 and washed with Et2O (abundant, until it was a fine powder > 50 mL). Then a column using Acetone :H2O:KNO3 (10:3: 1) was made, followed by a crystallization by diffusion suing acetone(IN) / diethylether(OUTSIDE) to afford the complex [Fe(BODIPYCNC)2]2+in 7 mg (30%). 1H NMR (400 MHz, ACN-t / 3) 8 8.24 (d, J= 8.2 Hz, 1H), 8.17 (s, 1H), 8.15 (d, J= 2.2 Hz, 2H), 7.70 (d, J= 8.1 Hz, 1H), 7.05

[0150] (d, J= 2.2 Hz, 1H), 6.17 (s, 1H), 2.63 (s, 3H), 2.53 (s, 3H), 1.53 (s, 3H). HRMS (ESI-TOF) m / z [M]2+Calcd for C64H6oB2F4FeNi4 = 589.2293; Found: 589.2295.

[0151] 9-(6-bromohexyl)-9H-carbazole (0.054 g, 0.163 mmol) was charged in a 25 mL round bottomed flask and dissolved in 1 mL of DMF. Then added KI (0.054 g, 0.327 mmol) to the above solution and stirred for 1 h. After 1 h, complex [Fe(CNCpyr)2]2+(0.040 g, 0.041 mmol) was added to the above solution and heated at 100 °C for overnight. After completion of complexation, saturated solution of NH4PF6 was added (10 ml) and the precipitate was collected by filtration. Then the crude was further purified on silica gel column chromatography using acetone / H2O / KNO3(sat) = 10: 3: 0.5 mixture. The bluish fraction was collected and after the evaporation of acetone, the left solution was treated with a saturated solution of NH4PF6. Affording the precipitation of the desired complex, it was then filtered, washed with distilled water followed by ether, and dried under vacuum. The isolated [Fe(CNCcbz)i]2+was obtained as a dark blue colour (0.040 g, 55.3% yield).JH NMR (400 MHz, CD3CN, 5 ppm): 8.85 (d, J= 6.51 Hz, 2H), 8.57 (d, J= 6.44 Hz, 2H), 8.24 (s, 2H), 8.18-8.14 (m, 4H), 7.58-7.56 (m, 2H), 7.52-7.49 (m, 2H), 7.25 (t, J= 7.33 Hz, 2H), 7.09 (d, J= 1.73 Hz, 2H), 4.56 (t, J= 7.36 Hz, 2H), 4.43 (t, J= 6.98 Hz, 2H), 2.58 (s, 6H), 2.02-2.01 (m, 2H), 1.93-1.91 (m, 2H), 1.47-1.46 (m, 4H).13C NMR (100 MHz, CD3CN, 5 ppm): 199.25, 155.12, 152.89, 145.70, 143.14, 141.01, 127.80, 126.55, 126.33, 123.13, 120.82, 119.42, 117.26, 109.70, 104.21, 62.19, 43.03, 35.33, 31.22, 28.94, 26.77, 26.04. ESI-HRMS calcd for C72H72FeNi4 m / z = 594.2701. Found: 594.2716 [M-2PF6], C72H7iFeNi4 m / z = 395.8440. Found: 395.8502 [M]3+.

[0152] In a schlenk with 2,6-bisimidazole-pyridine (100 mg, 0.47 mmol) and 4-(bromolethy)-7- methoxycoumarine (319 mg, 1.118 mmol) three three Ar-vacuum, 2.5 of DMF were added. The reaction was stirred overnight at 110°C. After this time a TLC using a mixture Acetone :H2O:KNO3 (10:3:3) was made and no signs of starting material 2,6-bisimidazole- pyridine was observed. Then 8 mL of water was added and 96 mg of KPFe was added, the mixture was stirred for 5 min. The precipitate was filtered through a sintered funnel #3 and washed with di ethylether (3x25 mL), affordingCOU2CNC in 380 mg (92% off-white solid). 'HNMR (400 MHz, ACN-t / 3) 8 9.67 (s, 2H), 8.47 (t, J= 8.1 Hz, 1H), 8.31 (s, 2H), 7.97 (d, J= 8.2 Hz, 2H), 7.74 (s, 2H), 7.64 (d, J= 8.8 Hz, 2H), 6.98 (d, J= 8.1 Hz, 4H), 6.02 (s, 2H), 5.72 (s, 4H), 3.90 (s, 6H).13C NMR (100 MHz, ACN-tZ3) 6 164.15, 160.51, 156.23, 147.75, 145.99, 145.65, 136.51, 125.77, 125.17, 120.99, 116.06, 113.16, 112.39, 110.81, 102.03, 56.50, 50.34. HRMS (ESI-TOF) m / z [M]2+Calcd for C33H26N5O6: 588.1883; Found:

[0153] 588.1883.

[0154] In a schlenk with 2,6-bisimidazole-pyridine (100 mg, 0.47 mmol) and l-bromo-3 -carbazole (300 mg, 1.04 mmol) three Ar-vacuum, then 5 mL of DMF were added. The reaction was stirred in dark overnight at 110°C. Then, 5 mL of cold acetone were added and the precipitate was filtered, the solid was recovered and diluted with MeOH (3 mL) then, 15 mL of water was added and 173 mg (2 equiv) of KPFe was added, the mixture was stirred for 5 min. The precipitate was filtered through a sintered funnel #3 and washed with diethylether (3x25 mL), affordingcbz2CNC in 674 mg (82% white-off solid).JH NMR (400 MHz, ACN-tfe) 5 8.81 (s, 2H), 8.34 (t, J= 8.1 Hz, 1H), 7.94 (d, J= 7.8 Hz, 4H), 7.75 (s, 2H), 7.63 (d, J= 8.1 Hz, 2H), 7.55 (d, J= 8.3 Hz, 4H), 7.44 (t, J= 7.7 Hz, 4H), 7.34 (s, 2H), 7.12 (t, J= 7.5 Hz, 4H), 4.60 (t, J= 6.5 Hz, 2H), 4.37 (t, J= 7.0 Hz, 2H), 2.65 (p, J= 6.8 Hz, 2H).13C NMR (100 MHz, ACN-tfe) 8 145.72, 140.90, 134.70, 127.01, 124.12, 123.57, 121.21, 120.23, 119.77, 115.42, 109.98, 49.76, 40.95, 28.6. HRMS (ESLTOF) m / z [M]2+Calcd for C41H37N7: 626.3032; Found: 626.3030.

[0155] In a schlenk with ligandcbz2CNC (50 mg, 0.054 mmol) and FeCh (3.4 mg, 0.027 mmol) three Argon-vacuum cycles were made, then 1.5 mL of DMF was added and stirred by 5 min at r.t. (until it was homogeneous), after this time KHMDS (26 mg, 0.136 mmol) was added. The reaction was stirred at room temperature during 3h, the reaction changed from colorless to clear reddish solution. After this time a TLC was made (Acetone:H2O:KNO3- 10: 1 :0.5-), an orange spot was observed and no signs of protonatedcbz2CNC. Then excess of NH4PF6 in water was added (60 mg in 10 mL) forming a yellow precipitate, which was filtered through a sintered funnel #3 and washed with H2O (2x5 mL) and di ethylether (3x10 mL). The solid was recovered with ACN, solvent was removed under vacuum. A column using Acetone:H2O:KNO3 (10: 1 :0.5) was made. The product was not pure so a size exclusion column (LH20) was made using ACN as eluent, affording the desired complex in 10 mg (23%, yellow-orange solid). 'H NMR (400 MHz, Acetone- e) 5 8.31 (d, J= 7.7 Hz, 4H), 7.64 (d, J= 2.2 Hz, 2H), 7.43 (ddd, J= 8.3, 7.2, 1.3 Hz, 4H), 7.37 - 7.32 (m, 4H), 7.30 (d, J= 2.2 Hz, 2H), 7.13 (d, J= 8.3 Hz, 4H), 7.05 (t, J= 8.1 Hz, 1H), 6.65 (d, J= 8.1 Hz, 2H), 4.04 (t, J = 6.3 Hz, 4H), 2.90 - 2.82 (m, 4H), 1.53 (td, J = 14.4, 12.1, 6.4 Hz, 4H). HRMS (ESI-TOF) m / z [M]2+Calcd for C82H7oFeNi4: 653.2326; Found: 653.2328.

[0156] In a schlenk with ligandcbz2CNC (50 mg, 0.054 mmol),npthCNC (39.6 mg, 0.054 mmol) and FeCh (6.9 mg, 0.054 mmol) three Argon-vacuum were made, then 3.5 mL of DMF was added and stirred by 5 min at r.t. (until it was homogeneous), after this time KHMDS (52 mg, 0.26 mmol) was added. The reaction was stirred at room temperature during 3h, the reaction changed from colorless to clear reddish solution. After this time a TLC was made (Acetone:H2O:KNO3; 10: 1 :0.5), three different spots were observed the most a-polar (yellow) on the top is the homoleptic [Fe(cbz2CNC)2]2+, in the middle a red spot for [Fe(nptbCNC)2]2+and the most polar (reddish) that matched for [Fe(cbz2CNC) (nptbCNC)]2+according to mass spectrometry. As for the treatment, an excess of NH4PF6 in water was added (120 mg in 10 mL) forming a red, which was filtered through a sintered funnel #3 and washed with H2O (2x10 mL) and diethylether (3x15 mL). The crude was purified over silica column using Acetone:H2O:KNO3 (10: 1 :0.5) as eluent isolating the last fraction. Then a preparative TLC was made with the same eluent, obtaining the product in 8 mg (10%). HRMS (ESI-TOF) m / z [M]2+Calcd for CeeHssFeN^: 557.6892; Found: 657.6967.

[0157]

[0158] In a schlenk with ligandcbz2CNC (50 mg, 0.054 mmol),cbzCNC (37.6 mg, 0.054 mmol) and FeCh (6.9 mg, 0.054 mmol) three Argon-vacuum were made, then 3.5 mL of DMF was added and stirred by 5 min at r.t. (until it was homogeneous), after this time KHMDS (52 mg, 0.26 mmol) was added. The reaction was stirred at room temperature during 3h, the reaction changed from colorless to clear reddish solution. After this time a TLC was made (Acetone:H2O:KNO3-10: 1 :0.5-), three different spots were observed the most a-polar (yellow) on the top is the homoleptic [Fe(cbz2CNC)2]2+, in the middle a red spot for [Fe(cbz2CNC) (nptbCNC)]2+and the most polar (reddish) that matched for [Fe(cbzCNC)2]2+according to mass spectrometry. As treatment, an excess of NH4PF6 in water was added (120 mg in 10 mL) forming a red, which was filtered through a sintered funnel #3 and washed with H2O (2x10 mL) and diethylether (3x15 mL). The crude was purified over silica column using Acetone:H2O:KNO3 (10: 1 :0.5) as eluent isolating the last fraction. Then a preparative TLC was made with the same eluent, obtaining the product in 7 mg (10%). HRMS (ESL TOF) m / z [M]2+Calcd for C66H53FeNi3: 542.7021; Found: 542.7026.

[0159] To a solution of 2,6-bis(2-methyl-lH-imidazol-l-yl)pyridin-4-amine (0.342 g, 1.34 mmol) in 7.3 mL HBr 48% in H2O, a solution of NaNCh (0.092 g, 1.34 mmol) in 1.4 mL of H2O was slowly added at 0 °C. The mixture was stirred for 15 min and added to a solution of CuBr2 (0.149 g, 0.69 mmol) in 2.3 mL HBr 48%. The resulting mixture was stirred and refluxed for 2 h. The reaction mixture was quenched with saturated NaOH until pH ~ 12. The suspension thus obtained was extracted with ethyl acetate (3 X 100 mL). The organic layer was washed with aqueous NaCl, dried over Na2SO4 and concentrated to dryness. The desired yellow compound 4-bromo-2,6-bis(2-methyl-lH-imidazol-l-yl)pyndine was obtained without purification and used directly for next step (0.296g, 0.93 mmol, 70%).1H NMR : (400.3 MHz, CDC13) : 6.47 (s, 2H), 7.33 (s, 2H), 7.05 (s, 2H), 2.71 (s, 6H).13C NMR (100.6 MHz, CDCI3+CD3OD) : = 150.30, 145.56, 137.13, 128.01, 119.45, 118.63, 15.61. HRMS (ESI-QTOF) (m / z) : calcd. for Ci3Hi3N5Br [M+H]+: 318.0354, found: 318.0355.

[0160] In a schlenk with 4-bromo-2,6-(dimethylimidazol-l-yl)pyridine (110 mg, 0.34 mmol), 4- formylphenylboronic acid (57 mg, 0.38 mmol), K2CO3 (94 mg, 0.68 mmol) and Pd(dppf)2C12 (12 mg, 0.017 mmol) and PPI13 (9 mg, 0.034 mmol) in a degassed mixture 4:1 of dioxane (8 mL) and water (2 mL) were refluxed for 18 h. After cooling to room temperature and addition of water (7 mL), the mixture was extracted with CH2Q2 (3 x 10 mL). The combined organic layers were dried with MgSCU, filtered and concentrated, the solid-crude was washed with copious amounts of n-hexane and it was used without further purification (0.102g, 0.3 mmol, 88%). 'HNMR : (400.3 MHz, CDCI3) : 10.12 (s, H), 8.06 (s, 2H), 7.84 (s, 2H), 7.51 (s, 2H), 7.40 (s, 2H), 7.07 (s, 2H), 2.70 (s, 6H).13C NMR (100.6 MHz, CDCI3) : = 191.32, 153.43, 150.73, 145.20, 142.31, 137.45, 130.81, 128.60, 128.06, 119.04, 112.97, 16.12. HRMS (ESI-QTOF) (m / z) : calcd. for C20H17N5O [M+H]+: 344.1511, found: 344.1512.

[0161] In a oven-dried schlenk with 4-(2,6-dichloropyridin-4-yl)benzaldehyde (102 mg, 0.3 mmol) was dissolved in dry DCM (19 mL), and the solution was degassed with Argon for 15 min, To this solution 2,4-dimethyl-lH-pyrrole (63 pL, 0.63 mmol), followed by the addition of a 3 drops of TFA. The reaction was stirred at r.t for 24h. After this time, p-chloroanil was added (74 mg, 0.3 mmol) and stirred for 4H. Then, an excess of EtsN (1 mL, 7.3 mmol) was added dropwise to the reaction mixture and stirred for 2h. Finally, 0.9 mL (7.3 mmol) of BF3°Et2O was added and let stirred for 24h at r.t. After this time, the reaction mixture was washed twice with 60 mL of NaHCCh (saturated solution) and once with brine (60 mL). The organic layer was dried over MgSCh and the solvent was removed under vacuum. After a Flash silica column was made using the mixture DCM:MeOH (9.9:0.1).

[0162] A mixture of 2,6-dibromopyridine (0.25g, 1.06 mmol), 2-Hydroxyphenylboronic acid (0.146g, 1.06 mmol), PPF13 (0.028 g, 0.106 mmol) and PdC12(dppf) complex (0.039 g, ca. 0.05 mmol) were dissolved under an inert atmosphere in DME (7.4 mL). A 2 M CS2CO3 solution (3.2 mL) was then added, and the mixture was stirred at reflux until consumption of the starting materials (ca. 20 h, TLC monitoring). The mixture was poured into a separation funnel, diluted with water and extracted with ethyl ether (4 x 20 mL). The combined organic layers were washed 3 times with brine. After desiccation over anhydrous Na2SO4, the volatiles were removed under reduced pressure. This afforded an oily material which was subjected to column chromatography on silica gel (hexane-EtOAc 4: 1) to obtain the desired 2-(6-bromopyridin-2-yl)phenol (0.11g, 0.44 mmol, 42%). 'H NMR : (400.3 MHz, CDCh) : 12.67 (s, 1H), 7.83 (d, J= 8.05 Hz, 1H), 7.73 (q, J = 2.99 Hz, 1 H), 7.67 (t, J = 7.95 Hz, 1 H), 7.41 (d, J = 7.80 Hz, 1 H), 7.36-7.30 (m, J = 4.17 Hz, 1 H) 7.04 (d, J = 8.28 Hz, 1 H), 6.95-6.89 (m, 1 H).13C NMR (100.6 MHz, CDCh) : = 159.24, 158.92, 139.64, 138.41, 132.17, 126.49, 125.52, 119.25, 118.84, 118.11, 117.87. HRMS (ESLQTOF) (m / z) : calcd. for Cl lH8BrNO [M+H]+: 249.9868, found: 249.9864. ,

[0163] Carbazole (1g, 5.98 mmol) was dissolved in dry THF (50 mL) in a 100 ml RB then at 0°C NaH 60% in dispersion in mineral oil (287 mg, 7.18 mmol) was added to the solution. With the evolution of H2 gas, the colorless solution became turbid. After 30 minutes, 1 equivalent of 1,3 -dibromopropane (0.607 mL, 5.98 mmol) was added to the mixture of solution and refluxed at 70 °C for 18 hours. The turbit solution was turn to clear honey color. Then stopped the reaction and TLC checked, a new intense spot was observed. After that, the solvent was removed with the help of vacuum and the obtained crude solid was purified by Flash chromatography by using silica gel with cyclohexane as eluent, colorless solid was obtained.

[0164] A mixture of 9-(3-bromopropyl)-9H-carbazole (500 mg, 1.73 mmol), imidazole (1.78 g, 17.3 mmol) and K2CO3 (478mg, 3.46 mmol) was stirred in dry acetonitrile (50 ml) at 75°C for 10 h (monitored by TLC). After cooling to room temperature, the solvent was concentrated and the residue was diluted with DCM (20 mL). The organic layer was washed with NaHCO3 solution (3 x 20 mL), dried over anhydrous Na2SO4 and concentrated. The residue was obtain by precipitation of impurities in n-pentane to afford 9-(3-(lH-imidazol- l-yl)propyl)-9H-carbazole in 86 % yield as light brown oil. The product was use without further purification. 'H NMR (400 MHz, (CD3)2CO) : 8.14 (d, J=7.76 Hz, 2 H), 7.57 (s, 1 H), 7.44 (m, 4 H), 7.21 (m, 2 H), 7.15 (s, 1H), 6.96 (s, 1H), 4.45 (t, J=14.83 Hz, 2 H), 4.20 (t, J=7.19 Hz, 2 H), 2.40 (quint, J=14.59 Hz, 2 H).13C NMR (101 MHz, (CD3)2CO) : 140.28, 137.26, 129.12, 125.72, 122.85, 120.19, 118.95, 118.74, 108.76, 44.09, 39.84, 30.21.

[0165] The title compound is obtained as follows: ( , eq) ,

[0166] Example of heteroleptic complexes of the invention

[0167] In a schlenk withcbz2CNC (50 mg, 0.054 mmol),NPTHCNC (39.6 mg, 0.054 mmol) and C0CI2 (24 mg, 0.054 mmol), three Ar-vacuum cycles were made, then 3.5 mL of DMF were added. After 3 min of stirring under Ar athmosphere KHMDS (24 mg, 0.12 mmol) were added and the reaction was stirred for 2h at r.t. Then 5 mL of diethyl ether were added and the reaction was filtered off recovering the solid by addition of MeOH (5 mL), then 10 mL of KPF6(saturated solution) were added and no precipitate appeared, an extraction was made with DCM (3x7 mL), giving an orange solid. HRMS-ESI m / z: [M]2+calcd for C66H53CoNi3O2: 559.1883 ; found: 559.1883.

[0168] Synthesis of [CoNPTHtpycbztpy]2+

[0169] In a schlenk withNPTHtpy (20 mg, 0.035 mmol) andcbztpy (16.8 mg, 0.035 mmol), three Ar- vacuum were made, then 1.5 mL of DMF were added and heated around 80°C to solubilizeNPTHtpy. Then the mixture was cooled to r.t., then C0CI2 (4.6 mg, 0.035 mmol) was added. The reaction was stirred for 2h. Two reddish different spots were observed. Then 5 mL of diethyl ether were added and the reaction was filtered off recovering the solid by addition of MeOH (5 mL), then 10 mL of KPFe (saturated solution) were added and no precipitate appeared, an extraction was made with DCM (3x7 mL), giving an orange solid. HRMS-ESI (pos. mode) m / z: [M ]2+calcd for C69H48N8O3CO 547.6591; found, 547.6578. Example 3: Fluorescence behavior of the compounds of the invention

[0170] The compounds described above, for instance Fel-2 as described in example 1, have been studied regarding their fluorescence behavior. The fluorescence spectra were recorded on a SAFAS-Xenius spectrometer (Monaco) and corrected for instrument response. Solutions of Fel-2 were prepared freshly in ethanol at a concentration corresponding to an absorbance of 0.1 OD and analyzed at 20°C in a quartz cuvette with an optical pathlength of 10mm.

[0171] Regarding Fel-2, and as shown in figure 1, and represented in figure 2, Di is quenched (typically more than 95% quenched) when the MBA is untransformed while D2 acts as an internal standard.

[0172] Without wishing to be bound by theory, it is believed that Di is quenched by PET (Photoinduced Energy Transfer).

[0173] When the MBA undergoes degradation, for example transchelation, fluorescence of Di is restored, as shown with another compound (figures 3 and 4).

[0174] Analogously, compounds of example 2 were tested using the same protocol.

Claims

CLAIMS1. A compound of the following formula (I):DI-EI-(MBA)-E2-D2(I), wherein :MBA is a metallo-biomedical agent, in which the metal is a metal M chosen from Co, Fe, Ni, Cu, Pt, Pd, Ru, Ir, Cr, and Mn; said metallo-biomedical agent MBA comprising at least one coordination moiety Zi constituted by or comprising at least one Ai coordinating atom, Zi being chosen from:• -O’, -OH, or -ORa,• -S’, -SH, or -SRa,• -S(O)Ra, -S(O)2Ra, or -SO3,• -Se’, -SeH, or -SeRa,• -COO’, -COOH, or -COORa,• -PRaRb or -P(O)RaRb,• -NH2, -NHRa or -NRaRb,• carbens, in particular N-heterocyclic carbens, more particularly normal and abnormal N-heterocyclic carbens,• heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, and• aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, being substituted by at least one group R chosen independently from: o -O’, -OH, or -ORa, o -S’, -SH, or -SRa, o -S(O)Ra, -S(O)2Ra, or -SO3, o -Se’, -SeH, or -SeRa, o -COO’, -COOH, or -COORa, o -PRaRb or -P(O)RaRb, o -NH2, -NHRa or -NRaRb,R being in particular -O’, -OH, or -ORa, more particularly -O’ or -OH,said aryl being in particular 2-HO-phenyl or 2-O'-phenyl,Ra, Rb being independtly chosen from and Ci-Ce-alkyl groups, aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl;Ei being bound to MBA by being covalently bound to Zi,E2 being bound through the atom or group X when it exists or through Eaotherwise to MBA by being covalently bound to one of the coordination moi eties of MBA;Di and D2 are organic fluorophores, Di being different from D2;Ei is a linker of following formula (Ila):-(A)x-(B)y-(C)z- (Ila), in which : x, y and z are independtly 0 or 1, with x + y + z > 0,A, B and C are independtly chosen from -C(R’)=C(R”)-, -C=C-, arene diyl groups, in particular benzene diyl, and heteroarene diyl groups, in particular triazole diyl or tetrazine diyl, with R’ and R” being independently chosen from H and Ci-Cs-alkyl groups; or Ei is absent;E2 is a linker of following formula (lib):-(X)1-Ea-(Y)J-(Eb)k- (lib), in which : i, j and k are independtly 0 or 1,X is O or NRC, with Rcbeing chosen from H and Ci-Cs-alkyl groups,Eaand Ebare independently chosen from Ci-Ci2-alkane diyl groups, said groups being optionnaly interupted by one or more -O- and / or -NH- residues;Y is chosen from O or NRc, with Re being chosen from H and Ci-Cs-alkyl groups, - NHCO-, -CONH-, -C(=O)-, -COO-, OC(=O), -C(R’)=C(R”)-, with R’ and R” being independently chosen from H and Ci-Cs-alkyl groups, -C=C-, maleimide diyl, arene diyl groups, in particular benzene diyl, and heteroarene diyl groups, in particular aza-heteroarene diyl groups, more particularly triazole diyl or tetrazine diyl.

2. The compound according to claim 1, wherein MBA comprises, further to Zi, n additional coordination moieties Z’, with n being chosen from 1, 2, 3, 4 or 5.

3. The compound according to claim 2, wherein the additional coordination moi eties Z’ constituted by or comprising at least one A’ coordinating atom, Z’ being chosen from:• -O’, -OH, or -ORa,• -S’, -SH, or -SRa,• -S(O)Ra, -S(O)2Ra, or -SO3,• -Se’, -SeH, or -SeRa,• -COO’, -COOH, or -COORa,• -PRaRb or -P(O)RaRb,• -NH2, -NHRa or -NRaRb,• carbens, in particular N-heterocyclic carbens, more particularly normal and abnormal N-heterocyclic carbens,• heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, and• aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl, being substituted by at least one group R chosen independently from: o -O’, -OH, or -ORa, o -S’, -SH, or -SRa, o -S(O)Ra, -S(O)2Ra, or -SO3, o -Se’, -SeH, or -SeRa, o -COO’, -COOH, or -COORa, o -PRaRb or -P(O)RaRb, o -NH2, -NHRa or -NRaRb,R being in particular -O’, -OH, or -ORa, more particularly -O’ or -OH, said aryl being in particular 2-HO-phenyl or 2-O’-phenyl,Ra, Rb being independtly chosen from and Ci-Ce-alkyl groups, aryls, in particular phenyl, and heteroaryls, in particular azaheteroaryls, more particularly aromatic amine groups, for example pyridinyl or quinoleinyl.

4. The compound according to anyone of the preceding claims, wherein Zi is chosen from: pyridinyl,• carbens, in particular N-heterocyclic carbens, more particularly normal and abnormal N-heterocyclic carbens, and• W-aryl groups, in particular W-phenyl group, wherein W is OH, SH, NH2 or PRa, with Rd being phenyl.

5. The compound according to anyone of the preceding claims, wherein MBA is chosen from:• terpyridine, bis-terpyridine and their derivatives, in particular 2,2':6',2"-terpyridine and bis-2,2':6',2"-terpyridine;• (carbene)(phenol)pyridine, in particular 2-(2-phenol)-6-(N-heterocyclic carbene)pyridine;• bis(carbene)pyridine, bis-bis(carbene)pyridine and their derivatives, in particular 2,6-bis(normal N-heterocyclic carbene)pyridine, 2,6-bis(abnormal N-heterocyclic carbene)pyridine, bis-2,6-bis(normal N-heterocyclic carbene)pyridine, bis-2,6- bis(abnormal N-heterocyclic carbene)pyridine; and• bis(phosphine)pyridine and their derivatives.

6. The compound according to anyone of the preceding claims, wherein Di and D2 are independently chosen from coumarine, carbazole, thieno[3,2-b]thiophene, triphenylamine, FsC-benzene, trifluoromethyl-benzene, anthracene, benzo[de]isoquinoline-l,3(lH,3H)- dione, BODIPY, rhodamines, cyanine3 amine, cyanine5 amine, cyanine? amine compounds, and their derivatives.

7. The compound according to anyone of the preceding claims, wherein M is Co, Fe, Ni, Cu, Pt, or Pd, in particular Fe, Co and Ru.

8. The compound according to anyone of the preceding claims, wherein Ei is a benzene diyl, in particular para-benzene diyl, or a thiophene diyl, in particular a 2,5- thiophene diyl.

9. The compound according to anyone of the preceding claims, wherein E2 is such as: -(X)i-Ea-(Y)j-(Eb)k- (lib),• i, j and k are 1,• X is O,• Eais a Ci-Cn-alkane diyl group, in particular a Ci-Cs-alkane diyl group,• Eb is a Ci-Cn-alkane diyl group, in particular a C2-Ci2-alkane diyl group, and / or• Y is an arene diyl, in particular benzene diyl, or an heteroarene diyl, in particular a tri azole diyl group.

10. Use of a compound according to claim 1, for the in vitro, ex situ or ex vivo study of the metallo-biomedical agent MBA.

11. Method of in vitro, ex situ or ex vivo study of a metallo-biomedical agent MBA, comprising a step of fluorescence measurement related to a compound according to claim 1.

12. A compound according to claim 1, for its use in the in vivo study of the metallo- biomedical agent MBA.

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