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An enlarged version of the ubiquitous tetrathiafulvalene-tetrabenzoic acid is described, with 4,4′-biphenyl moieties as spacers between the coordination moieties and the electroactive core. The obtained rectangular ligand has a 14 × 22 Å2 size and is combined with Zn(II) under solvothermal conditions to yield a coordination polymer endowed with large cavities of ca. 15 × 11 Å2/10 × 10 Å2. The topology of the material is discussed in detail using the Points of Extension and Metals (PE&M) or the Straight-rod (STR) representation, and the sqc1121 or tfo topological type of the structure is observed, respectively. Its stability towards solvent removal and electrical properties are discussed. The material does not present any permanent porosity upon desolvation according to nitrogen sorption measurements at 77 K. Nevertheless, a significant increase in conductivity is observed on compressed pellets of the material upon post-synthetic oxidation with iodine. Raman spectroscopy combined with density functional theory (DFT) calculations has been used to characterize the oxidation state of tetrakis(4-carboxylic acid biphenyl)tetrathiafulvalene for coordination polymers. [ABSTRACT FROM AUTHOR]

Electrocrystallization of ortho-dimethyltetrathiafulvalene (o-DMTTF) in the presence of a nitrite (NO2−) anion affords a 2 : 1 phase, namely (o-DMTTF)2NO2, the first example of an isolated cation radical salt with NO2−. The o-DMTTF molecule organizes into strongly dimerized stacks that adopt a rare chessboard organization, associated with a strongly 1D structure. As a consequence of dimerization, the salt exhibits a semiconducting behavior (σRT = 5 S cm−1, Eact = 0.1 eV). The bent NO2− anion is disordered on the inversion center but does not exhibit any anion-ordering transition. Combined SQUID magnetometry and electron paramagnetic resonance (EPR) experiments demonstrate the appearance of a spin-Peierls transition with TSP = 70 K. The temperature dependence of the spin gap and associated dimerization parameter δ across the spin-Peierls transition have been determined. The low-temperature narrow EPR line observed below TSP is attributable to intrinsic magnetic defects localized on the o-DMTTF molecules themselves. The broadening of the EPR line at higher magnetic fields is associated with the disordered NO2− anions surrounding these magnetic defects, contributing to the inhomogeneity of their g factor. [ABSTRACT FROM AUTHOR]

Harnessing a bis(selenomethyl)tetrathiafulvalene (TTF) derivative as a donor, conducting charge transfer (CT) salts are realized thanks to original packing structures supported by chalcogen bonding (ChB) interactions. Specifically, reaction of EDT-TTF(SeMe)2 (EDT = ethylenedithio) with an acceptor, 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane (F2TCNQ), afforded two polymorphs of 1 : 1 CT salts, α- and β-[EDT-TTF(SeMe)2](F2TCNQ). The donor and the acceptor molecules in both polymorphs organize into segregated and uniform stacks. Based on the structure, the α-salt shows a quasi-complete CT while the β-salt shows a partial CT with ρ ∼±0.8. The oxidation of TTF activates the σ-hole on Se atoms to be engaged in highly linear ChB interactions with the N atoms on F2TCNQ. The formation of directional ChB interactions resulted in original packing structures of the donor and the acceptor stacks that are distinct between α- and β-salts. In particular, the ChB motif observed in the β-salt allows F2TCNQ molecules within the stack to be closer than those in the α-salt. Consequently, the α-salt is a semi-conductor, while the β-salt shows metallic behaviour with a two-step metal-to-insulator (MI) transition. Moreover, the observed MI transition temperature in the β-salt (180 K) is substantially higher than that in other known CT salts, likely owing to the 3D coupling of the modulation in different chains brought about by the –SeMe substituents. [ABSTRACT FROM AUTHOR]

Chalcogen bonding (ChB) interactions are investigated in two new –SeMe substituted tetrathiafulvalene (TTF) derivatives, RTTF(SeMe)2 (R = Me2, SCH2CH2S). Upon oxidation to 1 : 1 cationic radical salts, Se atoms are engaged in highly linear ChB interactions with bromide anions, demonstrating the efficient σ-hole activation of selenium through redox-active substituents. [ABSTRACT FROM AUTHOR]

Electrocrystallization of TMTTF (tetramethyltetrathiafulvalene) in the presence of the dianionic [Pt(qS)2]2− platinum complex (qS: 5-sulfo-8-quinolinol) afforded simultaneously two phases. Phase A with isolated dicationic (TMTTF)22+ species is fully insulating and characterized by C–H hydrogen bonds with the anionic sulfonate moieties. Phase B is a mixed valence salt formulated as (TMTTF)3[Pt(qS)2]. It is organized into strongly trimerized chains, with a notably higher conductivity (σRT = 4 × 10−5 S cm−1). The charge distribution within the TMTTF trimers has been evaluated from the intramolecular bond distances, and IR and Raman spectra, converging all to a +0.5/+1/+0.5 motif, which is not modified at lower temperatures. Spectroscopic studies of such trimeric structures are scarce and the doublet (or triplet) structure expected in the IR of trimers is clearly identified here in the EMV-activated ν8(ag) mode associated with the totally symmetric vibration of methyl groups, in relation to the weak C–H⋯O hydrogen bonds between the radical cation and the dianionic [Pt(qS)2]2− platinum complex. [ABSTRACT FROM AUTHOR]

Modulation of the packing of the donors in the solid state and of the conducting behaviour is achieved in chiral radical cation salts based on the mono-alkylated donors methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF 1) and ethyl-ethylenedithio-tetrathiafulvalene (Et-EDT-TTF 2), underlining the paramount role of the number of stereogenic centres and substituent steric hindrance. Both donors have been prepared as racemates and then separated as pure enantiomers by chiral HPLC. Electrocrystallization experiments provided two complete series of crystalline radical cation salts formulated as [(R)-1]2PF6, [(S)-1]2PF6, and [(rac)-1]2PF6 and [(R)-2]2PF6, [(S)-2]2PF6 and [(rac)-2]PF6·(THF), respectively. The mixed valence salts of 1 show metal-like conductivity in the high temperature regime, while the radical cation salts of 2 are semiconductors, with a much higher conductivity for the enantiopure compounds than the racemic one. Tight-binding band structure calculations of the extended Hückel type performed for all the materials explain the observed conducting behaviour and show the differences in the intermolecular interactions triggered by the change of substituent between 1 and 2. [ABSTRACT FROM AUTHOR]

Neutral nickel bis(dithiolene) complexes, because of their closed-shell character, are usually considered as insulating materials, unless they are formed out of highly delocalized tetrathiafulvalenedithiolate ligands. We describe here an original series of S-alkyl substituted neutral bis(thiazole-4,5-dithiolate) nickel complexes formulated as [Ni(RS-tzdt)2] (R = Me, Et), which organize in the solid state into uniform stacks and exhibit semiconducting behavior, with room temperature conductivities comparable to those reported in the prototypical [Ni(dmit)2] and [Ni(Et-thiazdt)2] neutral complexes. These findings provide new perspectives in the current search for single component molecular conductors. [ABSTRACT FROM AUTHOR]

Control of the structural type in metallic enantiopure and racemic radical cation salts is achieved through hydrogen bonding interactions between the chiral donor DM-EDT-TTF and the XF6 anions (X = P, As, Sb), determined by the anion size and the chiral information. [ABSTRACT FROM AUTHOR]

In the search for single component conductors, eventually blessed with chirality, we have prepared three novel Au(iii) bis(dithiolene) complexes of the 6,7-dihydro-5H-1,4-dithiepine-2,3-bis(thiolate) ligand exhibiting a fused seven-membered ring. The unsubstituted ligand as well as two chiral enantiopure derivatives, with methyl groups in 5,7 positions or a ketal moiety in 6 position, were used to provide the corresponding anionic d8 Au(iii) bis(dithiolene) complexes (1, 2 and 3) as Bu4N+ salts. The anions adopt a square planar geometry around the gold atom with a pseudo centrosymmetric chair conformation of the outer seven-membered rings. Cyclic voltammetry experiments demonstrate that they can be easily oxidized to the neutral radical state in a 0.40–0.50 V range (vs. SCE). Their electrocrystallization afforded neutral radical species for two of them, which were structurally characterized. An original transformation of the unsubstituted complex 1 upon oxidation is observed in its oxidation product, leading to an unexpected radical complex 1′′, with two different dithiolene ligands. Its peculiar electronic structure and the formation of alternated stacks in the solid state explains its semiconducting character with direct gap. On the other hand, the radical complex 3′ derived from the chiral ketal derivative 3 is organized into face-to-face dimers, isolated from each other in the crystal. [ABSTRACT FROM AUTHOR]

The Z and E isomers of the iodinated TTF derivative (Z,E)-Me2I2-TTF co-crystallize in a mixed-valence salt with Br− anions, and are segregated into Z and E stacks, each of them with a different charge localization pattern, which also revealed charge-assisted halogen bonding. [ABSTRACT FROM AUTHOR]

In the presence of MeI or EtI, N-tert-butyl-1,3-thiazoline-2-thione derivatives undergo a transformation to 2-alkylthio-thiazoledithiolate pro-ligands with elimination of the tert-butyl substituent. The corresponding AuIII dithiolene complexes [Au(RS-tzdt)2]− (R = Me, Et) oxidize readily to the neutral radical species, such as the semi-conducting [Au(EtS-tzdt)2]Ṗ, which organizes into dimers in the solid state. [ABSTRACT FROM AUTHOR]

A novel 1D hybrid salt (MQ)[CuBr2]∞ (MQ = N-methylquinoxalinium) is reported. Structural, spectroscopic and magnetic investigations reveal a minimal CuII doping of less than 0.1%. However it is not possible to distinguish CuI and CuII. The unusually close packing of the organic moieties and the dark brown colour of the crystals suggest a defect electronic structure. [ABSTRACT FROM AUTHOR]

The single crystal X-ray structure of the all-axial conformer of the (R,R,R,R) enantiomer of the chiral donor tetramethyl-BEDT-TTF (TM-BEDT-TTF) was described and compared to the all-equatorial conformer. (S,S,S,S)-Tetramethyl-BEDT-TTF formed crystalline 1:1 complexes with TCNQ and TCNQ-F4, as well as a THF solvate of the TCNQ complex. Donors bis((2S,4S)-pentane-2,4-dithio)tetrathiafulvalene and (ethylenedithio)((2S,4S)-pentane-2,4-dithio)tetrathiafulvalene, which contain seven-membered rings bearing chirally oriented methyl groups, only formed complexes with TCNQ-F4. The TCNQ-F4 complexes contain planar organosulfur systems, in contrast to the TCNQ complexes in which there is minimal charge transfer. A variety of crystal packing modes were observed. Electrocrystallization experiments with both enantiomers and the racemic form of tetramethyl-BEDT-TTF afforded mixed valence radical cation salts with the AsF6 and SbF6 anions formulated as (TM-BEDT-TTF)2XF6 (X = As, Sb). Electrical conductivity was only found in one charge transfer complex, while the radical cation salts are all semiconducting. [ABSTRACT FROM AUTHOR]

A mixed-valence salt of tTTF-I with ClO4 -, formulated as (tTTF-I)2ClO4, is characterized by the presence of two crystallographically independent donor molecules, segregated in different layers and linked together through I...O interactions with the ClO4 - anion disordered at room temperature. The tTTF-I donor molecule was prepared by metallation of tTTF (trimethylene tetrathiafulvalene) followed by reaction with iodine to afford the mono and diiodo derivatives tTTF-I and tTTFI2, respectively. The crystal structure of the latter neutral tTTFI2 shows the occurrence of strong type II, I...I halogen bond interactions. Band structure calculations of the dual-layer structure of the 2 : 1 salt (tTTF-I)2ClO4 show co-existence of both 1D open and 2D closed Fermi surfaces. The salt undergoes a metal-insulator phase transition at TMI = 90 K, associated with an electronic dimensionality decrease, since already at 100 K, the 2D part of the Fermi surface transforms into 1D corrugated planes. High resolution X-ray investigations performed at 100 K, combined with multipolar refinements, indicate an approximately equivalent +0.5e charge in both donor molecules, as also deduced from the intramolecular bond distances. On the other hand, Raman spectroscopic investigations show that at ambient temperature the charge is actually distributed non-uniformly in conducting layers of tTTF-I molecules, with the identification of molecules with charges +1, +0.5, 0e, while at low temperature the charge distribution becomes essentially uniform (+0.5e), as confirmed from the X-ray high resolution data. These apparently contradictory behaviors are actually a consequence of a partial electron transfer between the two independent slabs to reach a common Fermi level in the metallic phase. [ABSTRACT FROM AUTHOR]

Using a slow liquid–gas diffusion method, the mixed-valence viologen salt (MV)2(BF4)3 (1) and the radical cation salt (MV)(BF4) (2) are crystallized. Both structures contain regular stacks of MVṖ+ radical cations (2) or alternating MVṖ+ and MV2+ entities (1). A short intrastack intermolecular separation (3.23 Å) unprecedently reveals strong interactions between MV2+ and MVṖ+ in 1. [ABSTRACT FROM AUTHOR]

A chiral organic conductor with metallic conductivity has been obtained by electrocrystallisation of a diiodotetrathiafulvalene derivative and enantiopure D-camphorsulfonate anion, associated in the solid state by halogen bonding interactions. [ABSTRACT FROM AUTHOR]

Electrocrystallization of TMTTF (tetramethyltetrathiafulvalene) in the presence of the dianionic [Pt(qS)2]2− platinum complex (qS: 5-sulfo-8-quinolinol) afforded simultaneously two phases. Phase A with isolated dicationic (TMTTF)22+ species is fully insulating and characterized by C–H hydrogen bonds with the anionic sulfonate moieties. Phase B is a mixed valence salt formulated as (TMTTF)3[Pt(qS)2]. It is organized into strongly trimerized chains, with a notably higher conductivity (σRT = 4 × 10−5 S cm−1). The charge distribution within the TMTTF trimers has been evaluated from the intramolecular bond distances, and IR and Raman spectra, converging all to a +0.5/+1/+0.5 motif, which is not modified at lower temperatures. Spectroscopic studies of such trimeric structures are scarce and the doublet (or triplet) structure expected in the IR of trimers is clearly identified here in the EMV-activated ν8(ag) mode associated with the totally symmetric vibration of methyl groups, in relation to the weak C–H⋯O hydrogen bonds between the radical cation and the dianionic [Pt(qS)2]2− platinum complex. [ABSTRACT FROM AUTHOR]

An enlarged version of the ubiquitous tetrathiafulvalene-tetrabenzoic acid is described, with 4,4'-biphenyl moieties as spacers between the coordination moieties and the electroactive core. The obtained rectangular ligand has a 14 × 22 Å 2 size and is combined with Zn(II) under solvothermal conditions to yield a coordination polymer endowed with large cavities of ca . 15 × 11 Å 2 /10 × 10 Å 2 . The topology of the material is discussed in detail using the Points of Extension and Metals (PE&M) or the Straight-rod (STR) representation, and the sqc1121 or tfo topological type of the structure is observed, respectively. Its stability towards solvent removal and electrical properties are discussed. The material does not present any permanent porosity upon desolvation according to nitrogen sorption measurements at 77 K. Nevertheless, a significant increase in conductivity is observed on compressed pellets of the material upon post-synthetic oxidation with iodine. Raman spectroscopy combined with density functional theory (DFT) calculations has been used to characterize the oxidation state of tetrakis(4-carboxylic acid biphenyl)tetrathiafulvalene for coordination polymers.

Neutral nickel bis(dithiolene) complexes, because of their closed-shell character, are usually considered as insulating materials, unless they are formed out of highly delocalized tetrathiafulvalenedithiolate ligands. We describe here an original series of S-alkyl substituted neutral bis(thiazole-4,5-dithiolate) nickel complexes formulated as [Ni(RS-tzdt)2] (R = Me, Et), which organize in the solid state into uniform stacks and exhibit semiconducting behavior, with room temperature conductivities comparable to those reported in the prototypical [Ni(dmit)2] and [Ni(Et-thiazdt)2] neutral complexes. These findings provide new perspectives in the current search for single component molecular conductors.

Control of the structural type in metallic enantiopure and racemic radical cation salts is achieved through hydrogen bonding interactions between the chiral donor DM-EDT-TTF and the XF 6 anions (X = P, As, Sb), determined by the anion size and the chiral information.

The Z and E isomers of the iodinated TTF derivative (Z,E)-Me2I2-TTF co-crystallize in a mixed-valence salt with Br(-) anions, and are segregated into Z and E stacks, each of them with a different charge localization pattern, which also revealed charge-assisted halogen bonding.

A novel 1D hybrid salt (MQ)[CuBr2]∞ (MQ = N-methylquinoxalinium) is reported. Structural, spectroscopic and magnetic investigations reveal a minimal Cu(II) doping of less than 0.1%. However it is not possible to distinguish Cu(I) and Cu(II). The unusually close packing of the organic moieties and the dark brown colour of the crystals suggest a defect electronic structure.

A mixed-valence salt of tTTF-I with ClO4(-), formulated as (tTTF-I)2ClO4, is characterized by the presence of two crystallographically independent donor molecules, segregated in different layers and linked together through I···O interactions with the ClO4(-) anion disordered at room temperature. The tTTF-I donor molecule was prepared by metallation of tTTF (trimethylene tetrathiafulvalene) followed by reaction with iodine to afford the mono and diiodo derivatives tTTF-I and tTTFI2, respectively. The crystal structure of the latter neutral tTTFI2 shows the occurrence of strong type II, II halogen bond interactions. Band structure calculations of the dual-layer structure of the 2 : 1 salt (tTTF-I)2ClO4 show co-existence of both 1D open and 2D closed Fermi surfaces. The salt undergoes a metal-insulator phase transition at T(MI) = 90 K, associated with an electronic dimensionality decrease, since already at 100 K, the 2D part of the Fermi surface transforms into 1D corrugated planes. High resolution X-ray investigations performed at 100 K, combined with multipolar refinements, indicate an approximately equivalent +0.5e charge in both donor molecules, as also deduced from the intramolecular bond distances. On the other hand, Raman spectroscopic investigations show that at ambient temperature the charge is actually distributed non-uniformly in conducting layers of tTTF-I molecules, with the identification of molecules with charges +1, +0.5, 0e, while at low temperature the charge distribution becomes essentially uniform (+0.5e), as confirmed from the X-ray high resolution data. These apparently contradictory behaviors are actually a consequence of a partial electron transfer between the two independent slabs to reach a common Fermi level in the metallic phase.

Using a slow liquid-gas diffusion method, the mixed-valence viologen salt (MV)2(BF4)3 (1) and the radical cation salt (MV)(BF4) (2) are crystallized. Both structures contain regular stacks of MV˙(+) radical cations (2) or alternating MV˙(+) and MV(2+) entities (1). A short intrastack intermolecular separation (3.23 Å) unprecedently reveals strong interactions between MV(2+) and MV˙(+) in 1.

The electrocrystallization of o-dimethyl-tetrathiafulvalene in the presence of halide anions affords 2:1 salts formulated as [o-DMTTF]2 X, (X = Cl, Br, I). The three salts are isomorphous, crystallizing in the tetragonal system, space group I42d, with the halide anion on the -4 site and the o-DMTTF molecule along a two-fold axis, forming strictly uniform stacks along c, and is further stabilized by C-H...X hydrogen bonds. Detailed physical investigations were performed on the bromide salt. It exhibits a metallic behaviour down to T(MI) = 50 K, while application of pressure moves the metal insulator transition to 39 K at 7.9 kbar. Band-structure calculations indicate a strong one-dimensional character, also confirmed by the anisotropy ratio of the conductivity, sigma / sigma = 500, as determined by two independent methods (four-contact, low-frequency transport measurements and analysis of the anisotropy of the Dysonian EPR line). The singular temperature dependence of the g tensor and the EPR line width at the phase transition suggests charge ordering.

Complementary shapes of the neutral symmetrical halogen-bond bis-donor core and octahedral inorganic cluster core prevent halogen-bonded polymers developing in more than one direction, favouring further templating by conducting radical cation slabs and yielding an 8 : 1 : 1 phase formulation instead of n : 2 : 1, with a 2D net, or m : 3 : 1, with a pseudo-cubic architecture, which may in principle also be targeted.