Conducting or semiconducting salt

Abstract

A conducting or semiconducting salt, wherein the salt formula unit is formed from n monovalent cations, or from n / 3 trivalent cations, wherein 2<n<4, and an anion having a charge k, wherein -4<k<-2, such that a neutral formula unit is formed with the n monovalent cations or the n / 3 trivalent cations, wherein the anion is planar and when in isolation has at least one unpaired electron and contains frontier π-orbitals, and wherein the anions in one direction of a crystal of the salt are aligned face-to-face.

Description

[0001]CONDUCTING OR SEMICONDUCTING SALT TECHNICAL FIELD The present disclosure relates to electrically conducting or semiconducting salts formedfrom monovalent or trivalent cations and an anion that is planar and when in isolation has atleast one unpaired electron and contains frontier π-orbitals. BACKGROUND ARTIonic materials based on abundant elements and organic materials, have the potential to becheaper, lighter, and more flexible than metals, such as Cu, and semiconductors such as Si,GaAs, and GaN, as well as established families of organic conductors. Ionic salts that are alsoelectrically conducting or semi-conducting are ideal from a design perspective, as both the cation and the anion can be modified to tailor properties, such as mass density, conductivity,and cost. While electrically conducting and semi-conducting ionic salts are known, theirperformances are relatively poor, with typical conductivities ranging from about 10-6to 10-2S·cm⁻¹ at room temperature, as seen for example in tetracyanoquinodimethane (TCNQ)-based charge-transfer salts and in conductive metal-organic frameworks (MOFs). Forcomparison, elemental copper exhibits an electrical conductivity of approximately 105S·cm⁻¹ under the same conditions.There is, hence, a demand for electrically conducting and semi-conducting ionic salts withbetter performance, such as increased electrical conductivity and / or improved thermalstability, and also electrically conducting ionic salts with possibility of superconductivity.SUMMARY OF THE INVENTION It is an object of the present disclosure to provide electrically conducting ionic salts with improved performance as compared to known electronically conducting ionic salts. Such salts could for example be used in electrical conductors and possibly also in superconductors. Those salts that are not metallic will instead be semiconducting and can be used in for example spintronics, optoelectronic devices, electrochemical sensors, diodes, solar cells, photovoltaics, or integrated circuits. The invention is defined by the appended independent patent claims. Non-limiting embodiments emerge from the dependent claims, the appended drawings and the following description. According to a first aspect there is provided a conducting or semiconducting salt, whereinthe salt formula unit is formed from n monovalent cations or from n / 3 trivalent cations,wherein 2<n<4, and an anion having a charge k, wherein -4<k<-2, such that a neutral formulaunit is formed with the n monovalent cations or the n / 3 trivalent cations, wherein the anionis planar and when in isolation has at least one unpaired electron and contains frontier π-orbitals and wherein the anions in one direction of a crystal of the salt are aligned face-to-face.The anions are aligned in face-to-face (including parallel-displaced) stacks along onedirection in the crystalline solid of the conducting or semiconducting salt. ‘Aligned’ heremeans that the mean planes of neighboring anions are substantially parallel and includecomplete alignment as well as some degree of offset from complete alignment. The face-to-face alignment is at least partially stabilized by multi-center inter-anion (‘pancake’) bonding.At the molecular level, such interactions can be described as covalent spin-pairing or partial electron sharing between planar or near-planar π-radical anions at interplanar separationscomparable to typical π–π stacking distances (e.g., about 2.7–3.8 Å), as well as below thesum of the van der Waals radii of the facing atoms. The anions should be close enough toallow favorable overlap between the π-systems of adjacent anions, even if offset fromcomplete alignment. ‘Face-to-face’ includes parallel-displaced geometries in which the meanplanes are substantially parallel (e.g., tilt ≤ about 10°) and includes arrangements with alateral offset of less than about 1.0 Å between the centroids of adjacent anions, sufficient tomaintain significant π-overlap.Such salts, i.e., compounds where ionic and covalent bonds are mixed in a solid-statestructure can be either metallic or semiconducting and exhibit a range of properties neededin, for example, conducting cables, spintronics, superconductors, optoelectronic devices,electrochemical sensors, diodes, solar cells, photovoltaics, or integrated circuits. Improvedperformance compared to known electronically conducting salts and other organic conductors is enabled by multi-center bonding between stacked anions, which can facilitate many electronic states near the Fermi level. The salt unit formula may be described by: Mn(CpX6-pOqY6-q), wherein M is the monovalentcations, or Nn / 3(CpX6-pOqY6-q), wherein N is the trivalent cation, wherein 2<n<4, wherein0≤ p ≤ 6 and 0≤ q ≤ 6 and wherein X represents substitution(s) of carbon, and Y represents substitution(s) of oxygen in the anion.The anion, when in isolation, may have a frontier π-orbitals occupied by 1, 2 or 3 electrons,at least one of which is unpaired. It is to be understood that one or more of the atoms included in the salt could be substitutedwith one of their corresponding isotopes, i.e. an atom having the same atomic number but adifferent mass number. By way of non-limiting example, this includes the substitution of carbon (12C) with its isotopes such as13C or14C, the substitution of oxygen (16O) with itsisotopes such as 17O or 18O, the substitution of 1H with 2H, or the substitution of a cationsuch as lithium (7Li) with another of its isotopes, for instance, ⁶Li. According to a secondaspect there is provided an electrical conductor, superconductor or semiconductorcomprising the conducting or semiconducting salt described above.According to a third aspect there is provided a use of the conducting or semiconducting saltdescribed above in an electrical conductor, superconductor or semiconductor.BRIEF DESCRIPTION OF THE DRAWINGSFig. 1 shows two examples of conducting salts whose structures have been predicted using acombination of Density Functional Theory (DFT) and structure search algorithms. A)predicted equidistantly stacked P6 / mmm phase of K3C6O6, B) predicted non-equidistantlystacked P1phase of K3.5C6O6. K, C and O atoms are indicated in the figure.Fig. 2 shows a schematic representation of the frontier molecular orbitals of the radicalanion [C6O6]3-.Fig. 3 shows a schematic representation of some electronic properties of the conductingsalts described herein. A) A fractional band occupation of highly disperse bands that arepredominately of π-type B) Electronic levels at the bottom of the frontier bands arepredominately bonding in nature between adjacent ions. Examples of such bondinginteractions are derived from the orbitals shown in Fig. 2. C) Electronic levels at the top ofthe frontier bands are predominately anti-bonding in nature between adjacent ions.Examples of such bonding interactions are derived from the orbitals shown in Fig. 2. D) Aquasi-one-dimensional electronic structure gives rise to characteristic Van Hove-like featuresin the Density of States (DOS), which provided suitable band occupation can result in manystates near εf,, which contributes to high electrical conductivity. E) The quasi-one-dimensional electronic structure ensures that the π-bands have a large dispersion across directions in the 1stBrillouin zone that correspond to the anion stacking direction Z. Fig.4 shows a schematic illustration of some consequences of a Peierls distortion in thedescribed materials. Peierls distortion is a structural instability common in low-dimensionalsystems where the lattice distorts periodically, opening an energy gap and lowering the system's total energy, often leading to altered electronic and transport properties. A)Example of a DOS of the frontier π-bands, filled by ¼, resulting from an equidistant stackingof radicals of formal charge -3. B) Result of a Peierls distortion, where the distances between radicals of formal charge -3 alternates, resulting in a gap opening above the Fermi level (εf).At the limiting case where the charge of the anions is -4 (i.e., where k equals -4), the Fermilevel has risen and the bottom band becomes completely filled, rendering the material semi- conducting.Fig. 5 shows electronic structure of the ground state P6 / mmm phase of K3C6O6, predictedusing DFT. A) A band structure showing significant dispersion of (on average ¼ occupied)frontier π-bands. B) DOS near the Fermi level (εf) showing characteristics of a one-dimensional electronic structure, including Van Hove-like peaks. Orbital projected DOS are shown for K, C and O. Fig.6 shows an example of the frequency resolved Eliashberg spectral function α2Fcalculated for a P6 / mmm phase of K3C6O6 along with the cumulative contribution of theelectron-phonon coupling strength λ (line marked by λ in the figure). Most of the electronphonon coupling is associated with soft modes that alter distances between stacked anions.Fig. 7 shows the pattern of the synthesized K3C6O6 salt using Powder X-ray Diffraction (PXRD)with a laboratory X-ray source (λ(Kα1) = 1.540596 Å and λ(Kα2) = 1.544493 Å, intensity ratioKα2 to Kα2 ≈ 2:1) on a Bruker D8 Discover diffractometer. Asterisk mark the strongest peaksof K3C6O6. Fig.8 shows the pattern of the synthesized K3C6O6 salt using Powder X-ray Diffraction (PXRD) with a synchrotron X-ray source (λ = 0.4940 Å). Model data were refined versus the pattern by the Rietveld method. All peaks can be explained with a single crystalline phase, meaning that the crystalline phase of the sample contains purely K3C6O6. The Rietveld fitting methoduses a least squares approach to refine a theoretical line profile until it matches themeasured profile. The quality of the Rietveld refinement was confirmed by a goodness of fit χ² value of 1.49 and a weighted-profile R-value (R_wp) of 3.57 %. The experimentally determined crystal structure from this pattern confirms that the planar [C6O6]3−anions arearranged in a face-to-face stacked configuration along one direction of the crystal. (On Fig. 8,circles show measured data and black line shows simulated data.)Fig. 9 shows DFT calculated Density of States (DOS) of the P6 / mmm phase of Li3C6O6,Na3C6O6, and Rb3C6O6. These calculations predict metallicity, under the assumption that thisphase is stable, and that the phase is stable has been confirmed for K3C6O6. The differencesin the DOS shapes arise because of decreasing π-band dispersion with larger cations, whichleads to a larger number of states N(εF) at the Fermi level for Rb>Na>Li, as expected.Fig. 10 is a photo taken of K3C6O6 as a black powder, a color commonly associated withmetallic or narrow-band gap behavior. The photo confirms that the material exhibitscharacteristics consistent with a conducting salt as defined herein.DETAILED DESCRIPTION Below is described in more detail a conducting or semi-conducting salt, wherein the generalsalt formula unit (the simplest whole-number ratio of ions representing the smallestelectrically neutral unit of the salt) is formed from n monovalent cations or from n / 3trivalent cations, wherein 2<n<4, and an anion having a charge k, wherein -4<k<-2, such thata neutral formula unit is formed with the n monovalent cations or the n / 3 trivalent cations,wherein the anion is planar and when in isolation has at least one unpaired electron andcontains frontier π-orbitals, and wherein the anions in one direction of a crystal of the salt are aligned face-to-face. The salt unit formula may be described by: Mn(CpX6-pOqY6-q), wherein M is the monovalentcations, or Nn / 3(CpX6-pOqY6-q), wherein N is the trivalent cations, wherein 2<n<4, wherein 0≤ p≤ 6 and 0≤ q ≤ 6, and wherein X represents substitution(s) of carbon and Y represents substitution(s) of oxygen in the anion.The stoichiometry n in Mn(CpX6-pOqY6-q) or Nn / 3(CpX6-pOqY6-q) is changed around the value 3such that 2<n<4, thereby affecting the electronic state of reduction of the anion as describedbelow. In other words, k can be any integer or non-integer number smaller than -2 andlarger than -4, such as e.g. -3.9 to -2.1, or -3.5 to -2.5. In some examples k is -2.5, -3, -3.5 or -3.54. In one embodiment the charge is -3.5 ≤ k ≤ -2.5. The anion may comprise a smalleramount of charge caused by a dopant, such as an additional charge of ±0.001-0.1. Oneexample of such a radical anion is the C6O6-3(Fig 1). Another example of a suitable anion is [C6O3(NH)3]3-, which comprises six carbon atoms and six substituents selected from oxygen and NH. This anion is planar and exhibits a radical ground state with frontier π-orbitals, enabling multi-center bonding when stacked face-to- face in the solid state. The presence of NH substituents introduces hydrogen bonding interactions and high-frequency vibrational modes, which can influence electron–phonon coupling and potentially enhance superconducting properties. Both [C6O6]3-and [C6O3(NH)3]3-satisfy the structural and electronic requirements described herein for achieving conducting or semiconducting behavior. In all embodiments, the anions, including [C6O6]3-and [C6O3(NH)3]3-, are arranged in a face- to-face stacked configuration along at least one crystallographic direction. This alignment facilitates multi-center bonding and the formation of highly dispersive π-bands, which are essential for achieving the desired electrical conductivity or semiconductivityX represents substitution(s) of carbon atoms (C) with one or more of B or N in the anion.When p=6, there are no substitutions of carbon atoms. Y represents substitution(s) of oxygen atoms (O) with one or more atoms or groups selected from S, CH2, NH, PH, or CF2 in the anion. When q=6, there are no substitutions of oxygen atoms. In one embodiment, Y represents substitution(s) of oxygen atoms (O) with one or more NH. p in the salt formula unit may be 0, 2, 4 or 6, and each pair of substituted C in the anion may then be substituted with one B and one N atom. The effect of such CC -> BN isoelectronic substitution is to slightly perturb the electronic structure of the anion and affect the conducting properties, and / or increase the stability of the anion, and / or tailor the interactions between anions and cations, and / or to introduce higher or lower phonon frequencies so to change the electron-phonon coupling, in turn important for the conducting properties. q in the salt formula unit may be 0, 1, 2, 3, 4, 5 or 6, and each substituted O in the anion maythen be substituted with an atom or group selected from S, CH2, NH, PH or CF2. The effect ofmaking substitutions of O can be to modify the electronic structure of the anion, and / or to increase the stability of the anion, and / or tailor the interactions between anions and cations, and / or to introduce higher or lower phonon frequencies so to change the electron-phonon coupling, in turn important for the conducting properties.q in the salt formula unit may be 3 and three O may then be substituted with an atom orgroup selected from S, CH2, NH, PH or CF2. Alternatively, q may be 0 and three O may thenbe substituted with one atom or group and three O may be substituted with a different atomor group, both selected from S, CH2, NH, PH and CF2. The effect of making substitutions of Oin a symmetric manner is to facilitate crystallization.In one embodiment q is 3 or 6 and each substituted O is substituted with NH.The p and q may be selected, and atoms may be arranged in such a way that the anions havea three-fold or six-fold rotational symmetry axis. One advantage of a high symmetry of theanion is to facilitate crystallization of the salt into phases, where anions stack face-to-face inone direction. Key to identifying the above conducting salts and the general salt formula unit are band- engineering rationales for performing design of materials related to the examples shown in Fig.1, which are K3C6O6 and K3.5C6O6. The salt structures have been predicted using a combination of Density Functional Theory (DFT) and structure search algorithms. A)Predicted equidistantly stacked P6 / mmm phase of K3C6O6, B) Predicted non-equidistantlystacked P1 phase of K3.5C6O6. K, C and O atoms are indicated in the figure.Fig. 9 shows DFT calculated Density of States (DOS) of the P6 / mmm phase of Li3C6O6,Na3C6O6, and Rb3C6O6. These calculations predict metallicity, under the assumption that thisphase is stable, and that the phase is stable has been confirmed for K3C6O6. The differencesin the DOS shapes arise because of decreasing π-band dispersion with larger cations, which leads to a larger number of states N(εF) at the Fermi level for Rb>Na>Li, as expected.The anion, when in isolation, needs to have a radical ground state. A radical ground state is necessary to enable multi-center covalent bonding between face-to-face stacked anions in the solid state, in turn needed for tailoring electrical conduction or semi-conduction. The anions need to be planar to be able to stack on top of one another in a crystal, eitherequidistantly as in Fig. 1A, or near-equidistantly as in Fig. 1B. This orientation disfavourslocalization of electrons, and facilitates for delocalized multi-centre bonding, described below. The anion needs to carry frontier π-orbitals that allows for multi-center bonding betweenstacked anions. The anion, when in isolation, may have frontier π-orbitals occupied by 1, 2 or3 electrons. Thereby ensuring a radical ground state. The e1g orbitals of [C6O6]3- shown in Fig.2 are one example of such topology. They explain how by varying the number of electronsaround the value 3 in a material, i.e.2 < n <4, a radical character can be formally maintained.The anion, when in isolation, may have two degenerate frontier π-orbitals occupied by 1electron. Thereby, ensuring a radical ground state. The e1g orbitals of [C6O6]3- shown in Fig. 2are one example of such topology, which require a high symmetry of the anion.Provided that the frontier orbitals of the anion are partially occupied, the electronic π-bandsthat result from such stacking may also become partially filled (see Fig. 3 point A). Theorbital topology of the anion is such that the occupied π-bands are predominately bondingbetween neighbouring anions (see Fig. 3 point B), which acts to stabilize the stackedstructure. Stacking of anions along one-direction in a crystal lattice is essential to generate aquasi-one-dimensional electronic structure, in which the density of states (DOS) near theFermi level, εf, is high (see Fig. 3 point C). A high DOS near the εf is one necessity for goodelectrical conductance, and is exemplified in DFT predictions of K3C6O6 in Figure 5B, and Li3C6O6, Na3C6O6 and Rb3C6O6 in Figure 9. Other criteria for good electrical conductance arehigh electron velocity and small effective electron mass, both of which are ensured by high adispersion of partially occupied frontier π-bands (see Fig. 3 point D and Fig 5A). Suchdisperse bands will when partially occupied have large gradients and curvatures near εf, which corresponds to high electron velocity and small effective electron mass, respectively. The anion needs to have a high charge -4<k<-2, which ensures strong mutual electrostatic repulsion. The charge needs to be commensurate with a formal radical character and a frontier orbital topology described above. A large electrostatic repulsion is important as it favours the formation of equidistant or near-equidistant stacking of the anion in thecondensed phase. One example of such a radical anion is [C6O6]3- shown in Fig. 1A.Multiple designs of the anion are possible beyond the C6O6n-example that uphold theconditions discussed above. Examples of such designs are discussed below, and includevalence isoelectronic modification of C6O6n-, i.e., changes to C6O6n-that change the atomic composition but not the formal number of valence electrons or their electronic disposition, alongside other substitutions that can enable control of conducting properties by acting as small perturbations to the electronic structure, for instance by shifting the energies of frontier π levels in predictable directions. The cation may be selected from Group 1 metal ions, ammonium, guanidinium, imidazolium,guanylurea ions, or phosphonium-containing cations. Examples of Group 1 metal ionsinclude Li+, Na+, K+, Rb+, and Cs+. Molecular cations may include ammonium-containing ionssuch as NH4+, NF4+, and CH3NH3+, quaternary (tetraorgano)ammonium ions such as N(CH3)4+and NPh4+, guanidinium (C(NH2)3+), imidazolium derivatives, guanylurea ions, andphosphonium-containing cations such as P(CH3)4+. These cations can be used individually orin combination to tailor the structural and electronic properties of the salts. The presence ofH in the cations can introduce hydrogen bonding interactions and high-frequency vibrationalmodes, which can influence electron–phonon coupling and potentially enhance superconducting properties. The monovalent cation may be selected from one or more of monovalent alkali cations, ormonovalent molecular cations. The monovalent cations in the salt may be selected from thesame group (listed immediately above) of monovalent cations or different groups of monovalent cations.Monovalent alkali cations may be selected from Li+, Na+, K+, Rb+ and Cs+.Monovalent molecular cations may be selected from ammonium-containing ions,phosphonium-containing ions, guanidinium cations, aromatic cations, imidazolium cations,pyridinium cations, guanylurea cations, and biguanide cations.Ammonium-containing cations may e.g. be: NH4+, NF4+, N(CH3)4+, CH3NH3+, or N(C6H6)4+.Phosphonium-containing cations may e.g. be: PH4+, PF4+, P(CH3)4+ or P(C6H6)4+.Imidazolium cations may e.g. be: 1,2,3-trimethylimidazolium, 1-ethyl-2,3-dimethylimidazolium , 1,2,3-Trimethylimidazolium, 1-Ethyl-2,3-dimethylimidazolium, 1,3- Dimethyl-2-phenylimidazolium, 1-Benzyl-2,3-dimethylimidazolium. Guanidinium cations may e.g. be: C(NH2)3+.Biguanide cations may e.g. be: C2H7N5+.Guanylurea cations may e.g. be: C2H7N4O+.Alternatively, the cation may be a trivalent cation selected from trivalent main group (p- block) cations, trivalent transition metal (d-block) cations, trivalent lanthanide (f-block) cations, and trivalent actinide (f-block) cations.A trivalent cation corresponds to the charge of three monovalent cations.The trivalent main group (p-block) cations may be selected from Al3+, Ga3+, In3+, Tl3+ andBi3+.The trivalent transition metal (d-block) cations may be selected from Sc3+, Y3+, Cr3+, Fe3+,Co3+, Ru3+, Rh3+, Ir3+, Au3+ and La3+.The trivalent lanthanide (f-block) cations may be selected from Ce3+, Pr3+, Nd3+, Pm3+, Sm3+,Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+ and Lu3+.The trivalent actinide (f-block) cations may be U3+or Th3+.In one example, the trivalent cation is selected from Al3+, Ga3+, Al3+, Sc3+, Bi3+, Y3+, La3+, Ce3+,Pr3+, Nd3+, Pm3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, or Lu3+.The electronic structure of the anion, the size of the cation, and an optional incorporation ofhydrogen in the anion and / or in the cation are all important design choices for enhancingthe likelihood of strong electrical conduction, electron phonon coupling, as well assuperconductivity at practically useful temperatures (nearing liquid nitrogen), rationales forwhich are described below. Some materials may alternatively be semi-conductors, the reasons for which are also described below. The specific criteria described for the anion is what gives rise to π-bands running along reciprocal space directions of the 1stBrillouin zone that corresponds to the real spacedirection of anion stacking (Fig. 3). Provided these bands are quasi-one dimensional they willgive rise to singularitity-like spikes in the density of states which, depending on the occupation of the bands, can ensure a large number of occupied levels N(εF) near the Fermilevel (Figs 3, 4, and 5).Arguments for good conducting properties in the described materials derives from molecular orbital theory and band theory, which tells us that salts composed from certain radical anions (e.g., as shown in Figs 1 and 2) stacked along one direction should facilitate for largenumber of electrons at the Fermi level, N(εF), which is crucial for a good conductor (Fig 3 and4). These arguments have been verified for a selection of materials using DFT, one examplebeing K3C6O6 for which N(εF) calculates as approximately 0.19 –0.27 states / eV / atom (Fig. 5),depending on level of theory. Other examples include Li3C6O6 (N(εF)≈0.1), Na3C6O6(N(εF)≈0.2) and Rb3C6O6(N(εF)≈0.4) in Figure 9. For comparison, elemental Cu, the maincomponent of conventional conducting wires and cables, has 0.29 states / eV / atom at theFermi level.The stacking distance d between the anions is what determines the dispersion of said π-bands, and hence the number of occupied levels N(εF) near the Fermi level. To a first orderof approximation, a higher N(εF) leads to a more conducting material. One possibility toaffect changes to d is by temperature. Temperature increases d through lattice expansion,which in turn decreases the band dispersion, which increases N(εF). The latter argument explains why a negative temperature coefficient of resistivity can be expected for thedescribed salts. One chemical way in which d can be rationally designed to increase ordecrease is by cation substitution, which is why there are several possible cations of different sizes listed above. Electron phonon coupling, approximately the response of the frontier bands to vibrational motion in a material, are essential for various material properties ranging from electrical conduction, thermoelectric materials, polaronic materials, colossal magnetoresistance, and conventional superconductivity. Electron phonon coupling in most of the described salts willbe dominated by relatively soft, i.e., low frequency, phonon modes that alter the stackingdistance d between anions, because such changes directly affect the dispersion of thefrontier π-bands, as just described, as well as the inter-anion multi-centre bonding (Fig 3).Fig.6 shows an example of frequency resolved Eliashberg spectral function α2F calculated forthe P6 / mmm phase of K3C6O6 along with the cumulative contribution of the electron-phonon coupling strength λ (line marked with λ in the figure). Most of the electron phononcoupling is associated with soft modes that alter distances between stacked anions. Changing the cation size and nature is therefore one way to rationally engineer the electron phonon coupling strength λ, (Eq 1)where ω is the phonon frequency. Equation 1 shows that if low frequency modes can bemade to couple to the frontier π-bands, λ can be increased. One way to affect such change isthrough substitution for larger and heavier cations and / or anions.Provided that superconductivity is phonon mediated, we can argue that to increase the critical superconducting temperature Tcin the salts described, one needs to ideally increaseN and λ as well as ensure the presence of both low frequency and high frequency phononmodes. To see why, we show Eq 2 which derives from a Bardeen-Cooper-Schrieffer (BCS)theory approximation to Tc, followed by Eq 3, the well-established McMillan-Allen-Dynesapproximation to the Eliashberg equations for calculating Tc: where in Eq 3, μ*is a parameter describing the effective coulomb repulsion, and ωlogis the logarithmic average phonon frequency. Eq 2 shows the critical dependence of Tc on N(εF)and λ, while Eq 3 depends crucially on ωlog. In other words, Eq 3 explains why also highfrequency modes are desirable for a high Tc – they will increase ωlog. One way to introduce high frequency modes is to include light elements, preferablyhydrogen, into the material. The inclusion of hydrogen atoms in the anion, or themonovalent molecular cations, introduces high frequency stretching and bending modes as well as hydrogen bonding interactions in the material. The latter kinds of interactions serve to couple high frequency modes to the movement of frontier bands. While not essential for conventional electrical conductivity, the inclusion of hydrogen in either cations or anions are likely necessary for any of the described salts to be superconducting near practically usefultemperatures (nearing liquid nitrogen).The rationales outlined above refer partly to a situation of equidistant stacked radicalanions, as also predicted for K3C6O6(see Fig.1). While such equidistant stacking can be favored by the large electrostatic repulsion of the anions and the multi-center covalent bonding interactions (Fig 3), such structures are rare and are in many cases expected to undergo a symmetry breaking (Peierls) distortion that creates stacks of pairs of coupled radicals (see K3.5C6O6in Fig 1). If such symmetry breaking occurs and depending on the degree of reduction of the anion, an electronic gap may open rendering the material in question semi-conducting instead of metallic. A Mott transition, a phenomenon in whichstrong electron correlation in a material causes the opening of a gap (large or small), despiteband theory (Fig 4) predicting metallic behaviour, is another way in which some describedmaterial may become semi-conducting. Semi-conducting salts of the kind described mayprove exceedingly useful in a range of applications such as spintronics, optoelectronic devices, electrochemical sensors, diodes, solar cells, photovoltaics, or integrated circuits. Some specific examples of combinations of cations and anions in the salt formula unit are: [Na]3C6O6and [Rb3]C6O6, both examples out of several plausible in which differently sized cations are used to modify the electronic structure and conducting properties of the salt.[NH4]3[C6O6], [N(CH3)4]3[C6N6H6], and [C(NH2)3]3[C3N3H3O3], all examples out of severalplausible examples that introduce hydrogen bonding and light elements that provide high frequency modes, beneficial to raise Tc.[Cs]3C6O6, [La]C6O6 and [Lu]C6O6, examples out of several plausible examples that introducesheavy elements that can provide low frequency modes, beneficial to raise λ and Tc. [Bi]C6(CF2)3(PH)3 and [Cs]3C6(CH2)3(S)3 examples out of several plausible examples that introduces heavy elements that can provide low frequency modes, beneficial to raise λ andTc, and light elements that provide high frequency modes, beneficial to raise Tc.[K]3B3N3O6 and [P(CH3)4]3B3N3O6, both examples out of several possible examples whereisoelectronic CC ↔BN substitution are used to modify the electronic structure and conducting properties of the salt. EXAMPLESThe following example demonstrate the synthesis, structural characterization, and functionalproperties of an embodiment of the conducting salt described as: a conducting orsemiconducting salt, wherein the salt formula unit is formed from n monovalent cations orfrom n / 3 trivalent cations, wherein 2<n<4, and an anion having a charge k, wherein -4<k<-2,such that a neutral formula unit is formed with the n monovalent cations or the n / 3 trivalentcations, wherein the anion is planar and when in isolation has at least one unpaired electronand contains frontier π-orbitals, and wherein the anions in one direction of a crystal of said salt are aligned face-to-face.Several examples are given with the monovalent cation K+, but it is understood that thesame synthesis can be used for other monovalent cations or trivalent cations covered by thedescription above. Several examples are given for the anion [C6O6]3- but it is understood thatthe same synthesis can be used when using other anions covered by the description above,and for combinations of such cations and anions. The exemplified salts can also be producedfrom other reactants. Further, larger or smaller amounts of reagents may be used and the volume of solvent might be varied. The type of solvent can be varied beyond the examples mentioned, and temperatures may be higher or lower than what is described. All manipulations involving reduced salts were performed under inert atmosphere (Ar) using oven-dried glassware. Anhydrous THF or MeCN were used throughout. Drying was under vacuum unless otherwise stated. “Salt metathesis” herein means solution-phase counterion exchange between salts under anhydrous conditions, typically driven by precipitation of an insoluble potassium salt (KX) and / or cation complexation; no ion-exchange resin is used.Reduced salts can be air / moisture sensitive, why storage and transfer should be made underAr / N2 in sealed vessels.Cation exchange and elemental composition can be verified by Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP-OES). Samples were dissolved in dilute nitric acid to a known concentration prior to analysis.Phase purity of the crystalline salts can be assessed by Powder X-ray Diffraction (PXRD)under exclusion of air. Data were collected on a Bruker D8 Discover diffractometer using CuKα radiation (λ(Kα1) = 1.540596 Å, λ(Kα2) = 1.544493 Å, Intensity ratio Kα1 to Kα2 ≈ 2:1)over a 2θ range of 15° to 66° with a step size of 0.02°.Example 1: Preparing K3C6O6from K2C6O6and potassium metal -Under inert conditions, 1 eq. of benzophenone is dissolved in tetrahydrofuran(THF, 7.5 mg benzophenone per mL THF) and 1 eq. of K2C6O6(95 % purity, possibly partially hydrated) is added to the liquid. -1.5 eq. of potassium metal is freshly cut under inert conditions and added tothe mixture. -The mixture is left to react (blue coloration appears) while stirring until theblue color disappears again (roughly 4 h). -The stirring is stopped and the powder is allowed to settle. The supernatant isremoved and the powder washed with THF of the same volume three times, then left to dry. Drying can be performed in room temperature. The purposeof the drying step is to evaporate the solvent. -Phase purity assessed by PXRD.Example 2: Preparation of Na3C6O6 from Na2C6O6 and sodium metalUnder inert conditions, dissolve 1^equiv benzophenone in THF (7.5^mg·mL⁻¹) and add 1^equivNa2C6O6. Introduce 1.1^equiv freshly cut sodium metal. Stir until the blue colorationdisappears (~4^h). Isolate by decanting / filtration, wash with THF (3×), and dry in inert atmosphere at room temperature and / or under vacuum.Examples 1 and 2 above can be generalized to alkalis monovalent cations, including Li+, Na+,K+, Rb+, and Cs+. Example 3: Preparation of K3.5C6O6 (non integer stoichiometry) Under inert conditions, dissolve 1^equiv benzophenone in THF (7.5^mg·mL⁻¹) and add 1^equiv K2C6O6 (≈95%). Add potassium metal in two portions: first 1.5^equiv and, after the blue color dissipates (~4^h), an additional 0.5^equiv. After the second blue phase decays (~4^h), isolate, wash with THF (3×), and dry.Example 3 can be generalized to alkalis monovalent cations, including Li+, Na+, K+, Rb+, andCs+. Example 4. Preparing K3C6O6from H2C6O6dihydrate -Under inert conditions, 1 eq. of benzophenone is dissolved in THF and H2C6O6 · 2 H2Ois added to the liquid. -3.5 eq. of potassium metal is freshly cut under inert conditions and added to themixture. -The mixture is left to react (bubble formation and blue coloration appears) whilestirring until the blue color disappears again (roughly 4 h). -The stirring is stopped and the powder is allowed to settle. The supernatant isremoved and the powder washed with THF of the same volume three times, then left to dry. Drying can be performed in room temperature, at elevated temperature,under vacuum conditions. The purpose of the drying step is to evaporate the solvent. Example 4bExample 4 above can be generalized to alkalis monovalent cations, including Li+, Na+, K+, Rb+,and Cs+.Example 5. Preparing K3C6O6 by Crown-assisted Salt Metathesis from Na3C6O6Uses 15-crown-5 to hold Na⁺ in solu^on; exchange can run at room temperature; mild warming is optional if dissolution is slow; isolation is by cooling + dry hydrocarbon antisolvent. -Under argon, dissolve Na3C6O6 (1.0 eq) in a dry solvent mixture that gives a clearsolution (e.g., THF / MeCN 4:1 to 1:1, total ~10–20 mL per mmol).- In a separate vial, prepare a clear solution of KPF6 or KBF4 (3.3–3.6 eq) and 15-crown-5 (3.3–3.6 eq) in dry MeCN (5–10 mL per mmol).- Add the K+ / crown solution dropwise to the Na3C6O6 solution at room temperaturewith vigorous stirring (optionally 35–50 °C if needed for complete dissolution / fastexchange; remain strictly anhydrous). Stir 2–12 h.- Cool to ~0 °C, then induce precipitation by slow addition of a rigorously dryhydrocarbon antisolvent (e.g., hexane, heptane, or cyclohexane; 3–5× volume) withstirring. -Stop stirring, allow solids to settle, and collect on a dry Schlenk frit under Ar; discardthe filtrate (mother liquor), which contains [Na(15-crown-5)]⁺ and PF6- or BF4-.- Wash the cake with cold, dry hydrocarbon, then (if needed) a brief dry THF:hexane(1:1) rinse to strip residual crown.- Dry under high vacuum (room temperature); store under Ar, protected frommoisture.Example 5b: Synthesis of K3C6O6 by crown-assisted ball-mill Salt Metathesis from Na3C6O6In an Ar-filled glovebox, combine Na3C6O6 (1.0 eq), KPF6 or KBF4 (3.5–4.0 eq), and 15-crown-5 (3.5–4.0 eq) in a sealed milling jar. -Ball-mill 30–60 min with cooling intervals as needed.- Transfer the powder to a dry frit; wash through sequentially with dry MeCN, then dryTHF, then dry hexane until washes test Na-free (spot test or ICP on an aliquot).- Dry under high vacuum (room temperature); store under Ar.Structural Characterization of K3C6O6The phase purity of the synthesized K3C6O6 salt produced as in Example 1 was initially confirmed by Powder X-ray Diffraction (PXRD), see Fig.8. Fig.8 shows the pattern of the synthesized K3C6O6salt using PXRD with a synchrotron X-ray source (λ = 0.4940 Å). Model data were refined versus the pattern by the Rietveld method. The Rietveld fitting methoduses a least squares approach to refine a theoretical line profile until it matches themeasured profile. This technique involves fitting a calculated diffraction pattern to the observed pattern by iteratively refining structural parameters such as lattice constants, atomic positions, and thermal factors. The quality of the Rietveld refinement was confirmed by a goodness of fit χ² value of 1.49 and a weighted-profile R-value (R_wp) of 3.57 %. All peaks can be explained with a single crystalline phase, meaning that the crystalline phase of the sample contains purely K3C6O6. The experimentally determined crystal structure is inagreement with the computationally predicted structure shown in Figure 1A and confirmsthat the planar [C6O6]3−anions are arranged in an equidistant, face-to-face stacked configuration along one direction of the crystal. In Fig.7 simulated powder pattern of K3C6O6 based on crystal structure with more common wavelength of monochromated Cu-source (λ = 1.5406 Å) used in laboratory x-ray diffraction is shown. Fig.10 is a photo taken of K3C6O6as a black powder, a color commonly associated withmetallic or narrow-band gap behavior. The photo confirms that the material exhibitscharacteristics consistent with a conducting salt as defined herein. The result is consistentwith the theoretical framework disclosed, wherein the multi-center bonding between stacked anions facilitates the formation of highly disperse frontier π-bands and a high density of states near the Fermi level, leading to electrical conduction.Electrical Characterization of K3C6O6The K3C6O6salt is cast into a cylindrical, densified pellet of 95 % relative to thecrystallographic density by a laboratory hydraulic press. The length of the pellet is measuredvia a micrometer, the diameter is given by the diameter of the casting die. Two copper platesare polished, then placed on top and bottom of the pellet to increase the contact area. Theresistance is determined via touching the different copper plates with one probe of a multimeter as a two-point probe. As this measurement also measures resistances of contacts and wires, the value represents an upper boundary, not the intrinsic resistivity ofthe sample. Samples measured this way have a resistivity of about 50 to 60 Ohm⋅m, which isin the range of intrinsic resistivities of undoped seminconductors like silicon or germanium.Electrical conductivity measurements can be performed on pressed pellets using a standardfour-point probe method. Powders of the material are pressed into pellets of 10 mmdiameter with larger equal 95 % density of the crystalline phase (approx.2.2 g / cm^3). The flat top plane of the pellet is contacted to an electrical circuit with four equidistant wires,patches of sputtered metal contacts and wires attached with silver epoxy glue underexclusion of air. The wires are contacted to an impedance analyzer and measured either atroom temperature or during heating / cooling in a four-point probe configuration. Example 6: General preparation of M3C6O6 from K3C6O6 via Salt MetathesisThis example converts K3C6O6 to a tris(cation) salt M3C6O6 by precipitating an insolublepotassium salt KX. Choose X⁻ and solvent window so that KX precipitates while M3C6O6 staysin solution until you crash it with a dry hydrocarbon. -Under inert conditions (Ar / N2), dissolve K3C6O6 (1.0 eq) in a dry solvent system to aclear solution (0.02–0.05 M). Route 1 (halide driver): MeCN / THF 1:1 (MeCN ≥30% v / v).Route 2 (PF6- or BF4- driver): THF (MeCN ≤20% v / v total).- In a separate vial, prepare a solution of M+X- (3.3–3.6 eq) in dry MeCN (minimalvolume). Route 1: X⁻ = Cl- (to precipitate KCl).Route 2: X⁻ = PF6- or BF4- (to precipitate KPF6 or KBF4).- Add the M+X- solution dropwise to the stirred K₃C₆O₆ solution at rt; stir 1–4 h.Route 1: expect a fine KCl precipitate to form.Route 2: expect KPF6 or KBF4 to precipitate in THF-rich media.- Cool to ~0 °C, stop stirring, and filter under inert on a dry frit to remove KX (discardcake). Rinse the cake with small portions of cold, dry solvent (Route 1: MeCN / THF1:1; Route 2: THF). Combine filtrates. -Induce product precipitation by slow addition of a rigorously dry hydrocarbonantisolvent (hexane, heptane, or cyclohexane; 3–5× volume) at 0 °C with stirring.- Collect the solid M3C6O6 on a dry frit under Ar; wash with cold, dry hydrocarbon (and,if needed, a brief dry THF:hexane 1:1 rinse to strip residual donor solvent).- Dry the solid under high vacuum (rt); store under Ar, protected from moisture andlight. -Confirm cation exchange by ICP-OES and phase purity with PXRD as above.Example 6 above can be generalized to alkalis and molecular monovalent cations:Alkali cations may be: Li+, Na+, K+, Rb+, Cs+. Ammonium-containing cations may e.g. be: NH4+, NF4+, CH3NH3+, N(CH3)4+, N(C2H5)4+, N(n- C3H7)4+, N(n-C4H9)4+, N(n-C6H13)4+, N(C6H5)4+, Phosphonium-containing cations may e.g. be: P(n-C4H9)4+, P(C6H5)4+, PPh3Me+, PH4+, PF4+, or P(CH3)4+. Imidazolium cations may e.g. be: 1,2,3-trimethylimidazolium, 1-ethyl-2,3- dimethylimidazolium , 1,2,3-Trimethylimidazolium, 1-Ethyl-2,3-dimethylimidazolium, 1,3- Dimethyl-2-phenylimidazolium, 1-Benzyl-2,3-dimethylimidazolium. Aromatic onium cations may e.g. be: N-methylpyridinium, N-ethylpyridinium, N- butylpyridinium. Guanidinium cations may e.g. be: C(NH2)3+. Biguanide cations may e.g. be: C2H7N5+. Guanylurea cations may e.g. be: C2H7N4O+.Example 6a: Preparation of [PPh4]3C6O6 from K3C6O6 via Salt Metathesis- Under inert conditions (Ar / N2), dissolve K3C6O6 (1.0 eq) to a clear solution (0.02–0.05M) in dry MeCN (use MeCN / THF 1:1 only if needed for solubility).- Add of [PPh4]Cl (3.3–3.6 eq) as a pre-dried fine solid or concentrated solution in dryMeCN portionwise / dropwise at rt with vigorous stirring; stir 1–4 h. Afine KCl precipitate forms.- Cool to ~0 °C, and filter under inert on a dry frit to remove KCl (discard cake); rinsethe cake with cold, dry MeCN; combine filtrates.- Induce product precipitation by slow addition of a rigorously dry hydrocarbonantisolvent (hexane, heptane, or cyclohexane; 3–5× vol) at 0 °C with stirring (orvapor-diffuse hydrocarbon into the MeCN solution at 0–5 °C). -Collect the solid [PPh4]3C6O6 on a dry frit under Ar; wash with cold, dryhydrocarbon; dry under high vacuum (rt); store under Ar.- ICP-OES and PXRD as above.Example 6b: Preparation of [N(CH3)4]3C6O6 from K3C6O6 via Salt Metathesis -Under inert conditions (Ar / N2), dissolve K3C6O6 (1.0 eq) in dry MeCN / THF (1:1) to aclear solution (ca 0.02–0.05 M).- Add [N(CH3)4]Cl (3.3–3.6 eq) as a pre-dried fine solid or as a concentrated solutionin dry MeCN portionwise / dropwise at rt with vigorous stirring.- Cool to ~0 °C and stir 1–4 h; a fine KCl precipitate should form.- Filter under inert on a dry frit to remove KCl (discard cake); rinse cake with smallportions of cold, dry MeCN / THF (1:1) and combine filtrates.- Induce product precipitation by slow addition of a rigorously dry hydrocarbonantisolvent (hexane, heptane, or cyclohexane; 3–5× vol) at 0 °C with stirring.- Collect the solid [N(CH3)4]3C6O6 on a dry frit under Ar, wash with cold, dryhydrocarbon, and dry under high vacuum (rt).- Dry under high vacuum (rt); store under Ar.- Confirm cation exchange by ICP-OES and phase purity with PXRD as above.Example 7: Synthesis of Mixed-alkali Double Salt Na3K3(C6O6)2- Under Ar / N2 at 0–5 °C, prepare two clear solutions in dry THF (optionally ≤20% v / vMeCN if needed for clarity):– Solution K: K3(C6O6) (1.00 eq) at 0.02–0.05 M.– Solution Na: Na3(C6O6) (1.00 eq) at 0.02–0.05 M.- Combine equal volumes of Solution K and Solution Na at 0–5 °C, giving a mixedsolution with total anion concentration 0.02–0.05 M. Pre-equilibrate 15–30 min withvigorous stirring. -Crystallization (preferred, slow diffusion): Transfer the mixed solution to a dry, Ar-flushed vial at 0–5 °C and allow slow vapor diffusion of dryhexane / heptane (reservoir method) for 12–72 h until crystallization completes.Alternative (controlled crash): At 0 °C, add dry hexane / heptane dropwise to incipientturbidity, stop addition, age 1–4 h, then continue in small increments to a total of 3–5× vol while keeping the slurry mobile.- Collect crystals of Na3K3(C6O6)2 on a dry Schlenk frit under Ar; wash with cold, dryhydrocarbon(hexane / heptane); dry under high vacuum (rt); store under Ar,protected from moisture / light. -PXRD: single phase distinct from either Na3(C6O6) or K3(C6O6)Example 7b: Synthesis of Mixed-alkali Double Salt A3B3(C6O6)2The procedure outlined in Example 7 extends to mixed-cation double salts A3B3(C6O6)2 where A+ and B+ are any two monovalent cations listed in Example6, using the same co-crystallization from pre-isolated A3[C6O6] and B3[C6O6]; adjustthe THF / MeCN ratio to co-dissolve both (THF-rich for alkali, MeCN-richer for bulkyonium), and prefer slow diffusion at 0–5 °C; if fractionation occurs, seed with a 1:1mechanochemical pre-mix and re-grow.Example 8: Synthesis of M[C6O6] (M = Trivalent Cation) via Salt Metathesis- Suspend or dissolve K3C6O6 in dry THF (or THF-rich THF / MeCN) under inert gas, thenadd an anhydrous trihalide MCl3 (solvent)x so that KCl precipitates while M[C6O6]remains in solution until isolation. -Under Ar / N2, charge K3C6O6 (1.0 eq) and dry THF (to ~0.02–0.05 M) in an oven-driedflask; begin vigorous stirring at rt.- Add MCl3(THF)^ or MCl3 (MeCN)x (1.0–1.1 eq) portionwise or as a solution (dryTHF / MeCN). M3+is selected from: Al3+, Ga3+, In3+, Sc3+, Y3+, La3+, and the lanthanides Ce3+–Lu3+, Bi3+, or actinides U3+ or Th3+ . For Cr3+, Fe3+, Ru3+, Rh3+, Ir3+, see Example 8b.- Stir 2–24 h at rt (optionally up to 50 °C if needed for solubility), maintainingstrictly anhydrous conditions. A fine KCl precipitate should form.- Cool to ~0 °C, stop stirring, and filter under inert on a dry frit to remove KCl (discardcake); rinse cake with small portions of cold, dry THF and combine filtrates.- Induce precipitation of M[C6O6] by slow addition of a rigorously dry hydrocarbonantisolvent (hexane, heptane, or cyclohexane; 3–5× volume) at 0 °C with stirring, orby slow cooling of a THF solution if the product is poorly soluble. -Collect the dark solid M[C6O6] on a dry frit under Ar; wash with cold, dryhydrocarbon; dry under high vacuum (rt).- Dry the solid under high vacuum (rt); store under Ar, protected from moisture andlight. -Confirm cation exchange by ICP-OES and phase purity with PXRD as above.Example 8b: Preparation of La[C6O6] from K3C6O6 -Under Ar, dissolve K3C6O6 (1.00 eq) in dry THF (0.03 M) at rt.- Add LaCl3(THF)2 (1.05 eq) as a solution in minimal dry THF portionwise over 5–10min; stir 16 h at rt (or 40 °C if needed). KCl forms as a fine solid.- Cool to 0 °C, filter under inert to remove KCl; rinse cake with cold, dry THF; combinefiltrates. -Precipitate La[C6O6] by adding dry hexane (to 3–5× total) at 0 °C with stirring; collecton a dry frit; wash with cold, dry hexane; dry under high vacuum (rt).- Dry the solid under high vacuum (rt); store under Ar, protected from moisture andlight. -Confirm cation exchange by ICP-OES and phase purity with PXRD as above.Example 8c: Synthesis of M[C6O6] (M =Trivalent Cation) via Salt Metathesis with moreOxidizing M (e.g., Cr3+, Fe3+, Ru3+, Rh3+, Ir3+).- Under Ar / N2, pre-cool two solutions to −30 to −20 °C:Solution A: K3C6O6 (1.0 eq) in dry THF (0.02–0.05 M).Solution B: MCl3(MeCN)x (1.0–1.1 eq) in dry MeCN (minimal volume).- Charge a jacketed reactor with Solution A at −30 to −20 °C, vigorous s^rring;begin co-addition of dry hexane (2–3× total reaction volume over the addition) tolower the dielectric during the exchange. -Add Solution B dropwise via syringe pump (10–30 min) into Solution A at ≤−20°C while continuing hexane co-addition; a fine KCl precipitate should form.- Maintain ≤−20 °C for 10–20 min post-addition; immediately filter under inert on apre-cooled dry frit to remove KCl (discard cake); rinse cake with ice-cold dry THF;combine filtrates. -Induce precipitation of M[C6O6] by further addition of dry hexane / heptane (to 3–5×total) at 0 °C with stirring.- Collect the solid M[C6O6] on a dry frit under Ar; wash with cold, dry hydrocarbon; dryunder high vacuum (rt); store under Ar, protected from moisture / light. -Confirm cation exchange by ICP-OES and phase purity with PXRD as above. Example 8d: Synthesis of Actinide(III) salts An[C6O6] (An= U3+, Th3+) via Low-temperature Salt Metathesis -Under Ar / N2, pre-cool two solutions to −30 to −20 °C:Solution A: K3C6O6 (1.0 eq) in dry THF (0.02–0.05 M).Solution B: AnCl3(THF)x (An = U or Th) (1.0–1.1 eq) as a solution in minimal dry THF(optionally MeCN ≤20% v / v). -Charge a jacketed reactor with Solution A at −30 to −20 °C (vigorous s^rring);begin co-addition of dry hexane (2–3× total reaction volume over the addition) tolower the dielectric and promote KCl precipitation. -Add Solution B dropwise (10–30 min) at ≤−20 °C while continuing hexane co-addition;a fine KCl precipitate should form.- Maintain ≤−20 °C for 10–20 min post-addition; immediately filter under inert on apre-cooled dry frit to remove KCl (discard cake); rinse cake with ice-cold dry THF;combine filtrates. -Induce precipitation of An[C6O6] by further addition of dry hexane / heptane (to 3–5×total) at 0 °C with stirring.- Collect the solid An[C6O6] on a dry frit under Ar; wash with cold, dry hydrocarbon; dryunder high vacuum (rt); store under Ar, protected from moisture / light. Example 9: Preparation of K3[C6O3(=NH)3] from 1,3,5-triamino 2,4,6-trihydroxybenzene All operations under dry argon in oven dried glassware. THF (anhydrous, stored over 4^Å sieves) is used throughout. Step I: Oxidative dehydrogenation To a 50^mL Schlenk under Ar, add 1,3,5-triamino-2,4,6-trihydroxybenzene (0.50^mmol) anddry THF (10^mL; ~0.05^M). Cool to 0-5 °C.Add 2,6-dimethylpyridine (4.0^eq) by syringe at 0-5^°C. Add 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (3.3^eq) portionwise over 20-30^min,maintaining ≤5 °C with vigorous stirring.Stir 0-5^°C for 30-60^min, monitoring by IR (growth of C=O / C=N) or UV vis (onset of iminoquinone type bands). Filter cold and dry through a PTFE syringe filter or short Celite / alumina plug directly into a pre cooled, inert receiver (or the cannula leading to Step II) to remove DDQH₂ and fines (retained on the filter). Keep the filtrate cold under Ar for immediate use in Step II. Step II: Three electron reduction and K+capture In a 100^mL three neck under Ar at −78^°C, charge dry THF (50^mL) and a solu^on of K naphthalenide (0.10^M in THF, 1.60^mmol e⁻, 16^mL). S^r vigorously. Cannula transfer the cold Step I THF solution dropwise (10–20^min) into the −78^°C reduc^on flask.Maintain -78 to -60 °C for 15–30^min a^er comple^on of addi^on, then warm to −20 → 0 °Cover 30-60^min. If needed, add a small extra aliquot of K naphthalenide (0.2–0.3^eq) during −60 to −40^°C to ensure full uptake. Endpoint cues: (i) stable UV–vis spectrum over 5–10^min at the set temperature, and (II) no further spectral change after a diagnostic 0.1^eq increment of reductant at −60 to −40^°C. Step III: Isolation Hold at ~0^°C and induce precipitation by slow addition of a rigorously dry hydrocarbonantisolvent (3–5x volume), e.g., hexane, heptane, or cyclohexane, with vigorous stirring.(Avoid Et2O unless freshly dried and verified water free.) Collect the dark solid on a dry Schlenk frit under argon. Discard the filtrate (mother liquor), which contains naphthalene and 2,6 lutidine. Wash the cake with cold, dry hydrocarbon, e.g., hexane, heptane, or cyclohexane. Dry the solid under high vacuum at room temperature; store under Ar, protected from moisture and light. Example 10: Preparation of K3[C6O3(=NH)3] from 1,3,5-triamino 2,4,6-trihydroxybenzeneReplace K naphthalenide in Example 9 with a well stirred slurry of KC8 in dry THF delivering3.2^eq electrons at −78 → 0^°C. A^er reduc^on, perform a rapid coldfiltra^on under Ar to remove spent graphitic carbon, then precipitate the product with dry hydrocarbon, same as in 1a. The synthesis of salts containing the [C6O3(NH)3]3-anion can follow the general proceduresdescribed in Examples 9 and 10, using 1,3,5-triamino-2,4,6-trihydroxybenzene as the startingmaterial. Oxidative dehydrogenation followed by controlled reduction and cation exchange yields salts such as K3[C6O3(=NH)3].Analogous procedures can be applied to prepare salts with any of the monovalent ortrivalent cations described herein for [C6O6]3-, using [C6O3(NH)3]3- as a drop-inreplacement in the metathesis and mixed-cation procedures (see Examples 5-8, and 8c-d foroxidizing M3+), run THF-rich with MeCN ≤20% v / v at 0–5 °C to preserve =NH; proticammonium and unblocked imidazoliums require cold / fast handling. Example 10b: Preparation of M3[C6O3(NH)3] from K3[C6O3(NH)3] (where M is a monovalent cation)Follow general metathesis procedure outlined in Example 6 above, but with the K3C6O6reagent replaced by K3[C6O3(NH)3] and use Route 2 (THF; MeCN ≤20% v / v) at 0–5 °C topreserve =NH; stoichiometry and work-up unchanged. This procedure yields tris(cation) saltsof the NH-substituted anion, such as [PMe4]+3[C6O3(NH)3], and confirms the feasibility ofextending the synthesis to other anionic systems.Example 11: Preparation of M[C6O3(NH)3] from K3[C6O3(NH)3] (where M is a trivalent cation)Follow general metathesis procedure outlined in Example 8 above, but with the K3C6O6reagent replaced by K3[C6O3(NH)3] and use anhydrous MCl3(solvent)_x (1.0–1.1 eq; e.g., LaCl3(THF)2) as the cation source; run THF with MeCN ≤20% v / v at 0–5 °C to preserve =NH, rely onKCl precipitation as the driver, filter KCl cold, and isolate by dry hydrocarbon crash as inExample 8. This procedure yields trivalent salts of the NH-substituted anion, such asLa[C6O3(NH)3], and confirms the feasibility of extending the synthesis to trivalent cation saltsof [C6O3(NH)3]3- and similar systems.

Claims

CLAIMS1. Conducting or semiconducting salt, wherein the salt formula unit is formed from nmonovalent cations or from n / 3 trivalent cations, wherein 2<n<4, and an anion having acharge k, wherein -4<k<-2, such that a neutral formula unit is formed with the n monovalentcations or the n / 3 trivalent cations, whereinthe anion is planar and when in isolation has at least one unpaired electron and containsfrontier π-orbitals, and wherein the anions in one direction of a crystal of said salt are aligned face-to-face.

2. The conducting or semiconducting salt of claim 1, wherein the salt unit formula isdescribed by: Mn(CpX6-pOqY6-q), wherein M is the monovalent cations, or Nn / 3(CpX6-pOqY6-q), wherein N is thetrivalent cations, wherein 2<n<4, wherein 0≤ p ≤ 6 and 0≤ q ≤ 6 and wherein X representssubstitution(s) of carbon, and Y represents substitutions of oxygen in the anion.

3. The conducting or semiconducting salt of any of the preceding claims, wherein theanion, when in isolation, has frontier π-orbitals occupied by 1, 2 or 3 electrons, at least oneof which is unpaired.

4. The conducting or semiconducting salt of any of the preceding claims, wherein theanion, when in isolation, has two degenerate frontier π-orbitals occupied by 1 electron.

5. The conducting or semiconducting salt of any of claims 2-4, wherein the X representssubstitution(s) of C with one or more of B or N.

6. The conducting or semiconducting salt of any of claims 2-5, wherein the Y representssubstitution(s) of O with one or more atoms or groups selected from S, CH2, NH, PH and CF2.

7. The conducting or semiconducting salt of any of claims 2-6, wherein p and q,independently of each other, are 0, 3 or 6.

8. The conducting or semiconducting salt of claim 5, wherein p is 0, 2, 4 or 6, andwherein each pair of substituted C in the anion is substituted with one B and one N atom.

9. The conducting or semiconducting salt of any of claims 6-8, wherein q is 3 and threeO are substituted with an atom or group selected from S, CH2, NH, PH or CF2, or wherein q is0 and three O are substituted with one atom or group and three O are substituted with adifferent atom or group, both selected from S, CH2, NH, PH and CF2.

10. The conducting or semiconducting salt of any of the preceding claims, wherein theanion has a charge that is -3.5 ≤ k ≤ -2.5.

11. The conducting or semiconducting salt of any of the preceding claims, wherein themonovalent cations are selected from one or more of monovalent alkali cations ormonovalent molecular cations.

12. The conducting or semiconducting salt of any of claims 1-10, wherein the trivalentcations are selected from trivalent main group (p-block) cations, trivalent transition metal (d- block) cations, trivalent lanthanide (f-block) cations, and trivalent actinide (f-block) cations.

13. The conducting or semiconducting salt of claim 2, wherein the anion is a planarradical anion comprising six carbon atoms and six substituents selected from oxygen and NH.

14. The conducting or semiconducting salt of claim 13, wherein the anion is selectedfrom the group consisting of [C6O6]3-and [C6O3(NH)3]3-.

15. The conducting or semiconducting salt of claim 13, wherein the anion is [C6O6]3-.

16. The conducting or semiconducting salt of claim 13, wherein the anion is [C6O3(NH)3]3.

17. The conducting or semiconducting salt of any of claims 1–16, wherein the cation isselected from Group 1 metal ions, ammonium, guanidinium, imidazolium, guanylurea ions,or phosphonium cations.

18. The conducting or semiconducting salt of any of claims 1–16, wherein the cation is anammonium or phosphonium cation.

19. The conducting or semiconducting salt of any of claims 1–16, wherein the saltcontains M3(C6O6), where M is a monovalent cation selected from Li+, Na+, K+, Rb+, or Cs+.

20. The conducting or semiconducting salt of any of claims 1–16, wherein the trivalentcation is selected from, Al3+, Ga3+, Al3+, Sc3+, Bi3+, Y3+, La3+, Ce3+, Pr3+, Nd3+, Pm3+, Gd3+,Tb3+,Dy3+,Ho3+,Er3+,Tm3+,or Lu3+.

21. The conducting or semiconducting salt of any of claims 1–20, wherein the anions arealigned face-to-face along one crystallographic direction.

22. An electrical conductor, superconductor or semiconductor comprising the conductingor semiconducting salt of any of claims 1-21.

23. Use of the conducting or semiconducting salt of any of claims 1-21 in an electricalconductor, superconductor or semiconductor.

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