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Within this work we have investigated spiro‐based tetrathiafulvalenes (TTFs) obtained as mixtures of stereoisomers from racemic spiro[5.5]undeca‐1,8‐dien‐3‐one. Compared to previously described spiro‐TTFs, enantiomeric and diastereoisomeric forms have been here separated by chiral HPLC and fully characterized both experimentally and theoretically. The two types of spiro‐based chiral derivatives contain either one (2) or three (1) chiral centres out of each one is spiro‐type. Experimental CD, supported by TD‐DFT calculations, shows differences in the optical activity between the 1 and 2 and their intermediates. The low optical activity of 2 and 3 (spiro alone chirality) was attributed to the presence of two conformers in the solution (ax and eq) of opposite Cotton effect whereas in the case of 1 and 5 (spiro and stereogenic centres) the spiro chirality seems to be responsible of the Cotton effect in the high energy region whereas the R and S chirality in the low energy region. Racemic and enantiopure forms have been successfully used for the synthesis of charge transfer complexes with tetracyanoquinodimethane (TCNQ) based acceptors. [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 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]

Novel coordination polymers embedding electroactive moieties present a high interest in the development of porous conducting materials. While tetrathiafulvalene (TTF) based metal‐organic frameworks were reported to yield through‐space conducting frameworks, the use of S‐enriched scaffolds remains elusive in this field. Herein is reported the employment of bis(vinylenedithio)‐tetrathiafulvalene (BVDT‐TTF) functionalized with pyridine coordinating moieties in coordination polymers. Its combination with various transition metals yielded four isostructural networks, whose conductivity increased upon chemical oxidation with iodine. The oxidation was confirmed in a single‐crystal to single‐crystal X‐ray diffraction experiment for the Cd(II) coordination polymer. Raman spectroscopy measurements and DFT calculations confirmed the oxidation state of the bulk materials, and band structure calculations assessed the ground state as an electronically localized antiferromagnetic state, while the conduction occurs in a 2D manner. These results are shedding light to comprehend how to improve through‐space conductivity thanks to sulfur enriched ligands. [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]

Chiral bis(TTF) diamides have been obtained in good yields (54–74%) from 1,2-cyclohexane-diamine and the corresponding TTF acyl chlorides. The (R,R)-1 and (S,S)-1 enantiomers have been characterized by circular dichroism and the racemic form by single-crystal X-ray diffraction. The neutral racemic bis(TTF)-diamide shows the formation of a pincer-like framework in the solid state, thanks to the intramolecular S···S interactions. The chemical oxidation in a solution using FeCl3 provides stable oxidized species, while the electrocrystallization experiments provided radical cation salts. In particular, single-crystal resistivity measurements on the racemic donor with AsF6− as a counterion demonstrate semiconductor behavior in this material. The DFT and TD-DFT calculations support the structural and chiroptical features of these new chiral TTF donors. [ABSTRACT FROM AUTHOR]

Methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF (1) and dimethyl-ethylenedithiotetrathiafulvalene (DM-EDT-TTF (2) are valuable precursors for chiral molecular conductors, which are generally obtained by electrocrystallization in the presence of various counter-ions. The number of the stereogenic centers, their relative location on the molecule, the nature of the counter-ion and the electrocrystallization conditions play a paramount role in the crystal structures and conducting properties of the resulting materials. Here, we report the preparation and detailed structural characterization of the following series of radical cation salts: (i) mixed valence (1)2AsF6 as racemic, and (S) and (R) enantiomers; (ii) [(S)-1]AsF6•C4H8O and [(R)-1]AsF6•C4H8O where a strong dimerization of the donors is observed; (iii) (1)I3 and (2)I3 as racemic and enantiopure forms and (iv) [(meso)-2]PF6 and [(meso)-2]XO4 (X = Cl, Re), based on the new donor (meso)-2. In the latter, the two methyl substituents necessarily adopt axial and equatorial conformations, thus leading to a completely different packing of the donors when compared to the chiral form (S,S)/(R,R) of 2 in its radical cation salts. Single crystal resistivity measurements, complemented by thermoelectric power measurements in the case of (1)2AsF6, suggest quasi-metallic conductivity for the latter in the high temperature regime, with σRT ≈ 1-10 S cm-1, while semiconducting behavior is observed for the (meso)-2 based salts. [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]

Among single component molecular conductors, neutral radical gold dithiolene complexes [(R-thiazdt)2Au]. derived from the N-alkyl-1,3-thiazoline-2-thione-4,5-dithiolate (R-thiazdt) ligand provide an extensive series of conducting, non-dimerized, half-filled band systems. Analogues of the known R=isopropyl ( iPr) derivative were investigated here with R=NMe2, cyclopropyl (cPr) and n-propyl ( nPr), aiming at rationalizing the different solid state structures adopted by these compounds despite very closely related substituents on the heterocyclic nitrogen atom. An original crisscross organization within dimerized chains is observed with R=NMe2, differing however from the analogous iPr derivative by a 180° rotation of the heterocyclic nitrogen substituent. On the other hand, the cyclopropyl and n-propyl substituents lead to robust, uniform, non-dimerized chains with a strongly 1 D electronic structure and a formal half-filled electronic structure. The semiconducting behaviour of these two radical complexes is characteristic of a Mott insulator, whose sensitivity to external pressure has been evaluated up to 2.5 GPa. [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 enantiopure radical cation salts [( S, S)-DM-BEDT-TTF]4[ReCl6] ([( S, S)- 1]4[ReCl6]) and [( R, R)-DM-BEDT-TTF]4[ReCl6] ([( R, R)- 1]4[ReCl6]) [DM-BEDT-TTF = dimethylbis(ethylenedithio)tetrathiafulvalene] have been prepared by electrocrystallization of the chiral precursor DM-BEDT-TTF in the presence of NBu4[ReCl5(pyrazine)] (NBu4 = tetra- n-butylammonium cation; pyz = pyrazine) as supporting electrolyte. The single-crystal X-ray analysis shows that the compounds crystallize in the triclinic system, non-centrosymmetric space group P1, and that the donors arrange in parallel columns. The four independent donor molecules possess approximate charges of +1, +1/2, +1/2 and 0, according to the structural parameter analysis and band-structure calculations, which also support the semiconducting behaviour of the materials. The rhenium(IV) ion in both compounds is six-coordinate with six chloro atoms that describe a slightly distorted octahedral environment with Re-Cl distances that cover the short range 2.348-2.374 Å. Magnetic measurements on polycrystalline samples of [( S, S)- 1]4[ReCl6] and [( R, R)- 1]4[ReCl6] have been investigated in the temperature range 2-295 K. They are practically identical and confirm the presence of high-spin S = 3/2 [ReCl6]2- isolated monomers together with a Pauli paramagnetism, typical of this kind of system. The magnetic susceptibility data are thoroughly reproduced over the whole temperature range with a simple model of isolated S = 3/2 ions with a zero-field splitting plus a temperature-independent paramagnetism (TIP), and the best-fit parameters being gRe = 1.875(2), | D| = 4.50(3) cm-1 and TIP = 3630(20)×10-6 cm3 mol-1 (2 D is the energy gap between the MS = ±3/2 and MS = ±1/2 Kramers doublets). [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]

Oxidation of diiodoethylenedithiotetrathiafulvalene (EDT-TTF-I2), C8H4I2S6, with the strong oxidizer tetrafluorotetracyanoquinodimethane (TCNQF4), C12F4N4, affords, depending on the crystallization solvent, two polymorphs of the 2:1 charge-transfer salt (EDT-TTF-I2)2(TCNQF4), represented as D2A. In both salts, the TCNQF2 is reduced to the radical anion state, and is associated through short C-I. . .NC halogen bonds to two EDT-TTF-I2 molecules. The two polymorphs differ in the solid-state association of these trimeric D-A-D motifs. In polymorph (I) the trimeric motif is located on an inversion centre, and hence both EDT-TTF-I2 molecules have +0.5 charge. Together with segregation of the TTF and TCNQ derivatives into stacks, this leads to a chargetransfer salt with high conductivity. In polymorph (II) two crystallographically independent EDT-TTF-I2 molecules bear different charges, close to 0 and +1, as deduced from an established correlation between intramolecular bond lengths and charge. Overlap interactions between the halogen-bonded D0-A-•-D+• motifs give rise, in a perpendicular direction, to diamagnetic A22- and D0-D22+-D0 entities, where the radical species are paired into the bonding combination of respectively the acceptor LUMOs and donor HOMOs. The strikingly different solid-state organization of the halogen-bonded D- A-D motifs provides an illustrative example of two modes of face-to-face interaction between π-type radicals, into either delocalized, uniform chains with partial charge transfer and conducting behaviour, or localized association of radicals into face-to-face A22- and D22+ dyads. [ABSTRACT FROM AUTHOR]

Charge-assisted halogen bonding is unambiguously revealed from structural and electronic investigations of a series of isostructural charge-transfer complexes derived from iodinated tetrathiafulvalene and tetracyanoquinodimethane derivatives, (EDT-TTFI2)2(TCNQF n), n=0-2, which exhibit variable degrees of ionicity. The iodinated tetrathiafulvalene derivative, EDT-TTFI2, associates with tetracyanoquinodimethane (TCNQ) and its derivatives of increasing reduction potential (TCNQF, TCNQF2) through highly directional CI⋅⋅⋅N≡C halogen-bond interactions. With the less oxidizing TCNQ acceptor, a neutral and insulating charge-transfer complex is isolated whereas with the more oxidizing TCNQF2 acceptor, an ionic, highly conducting charge-transfer salt is found, both of 2:1 stoichiometry and isostructural with the intermediate TCNQF complex, in which a neutral-ionic conversion takes place upon cooling. A correlation between the degree of charge transfer and the CI⋅⋅⋅N≡C halogen-bond strength is established from the comparison of the structures of the three isostructural complexes at temperatures from 300 to 20 K, thus demonstrating the importance of electrostatics in the halogen-bonding interaction. The neutral-ionic conversion in (EDT-TTFI2)2(TCNQF) is further investigated through the temperature dependence of its magnetic susceptibility and the stretching modes of the C≡N groups. [ABSTRACT FROM AUTHOR]

Oxidation of 3,4-ethylenedithio-3'-iodo-tetrathiafulvalene (EDT-TTF-I) and 3,4-ethylenedithio-3',4'-diiodo-tetrathiafulvalene (EDT-TTF-I2) with DDQ afforded two different salts formulated as (EDT-TTF-I)(DDQ) and (EDT-TTF-I2)2(DDQ)⋅(CH3CN), both characterized with a full charge transfer to the DDQ acceptor moiety and by short and linear halogen bonding interactions between the iodine atom as halogen bond donor, and the carbonyl oxygen or the nitrile nitrogen atoms of reduced DDQ. [ABSTRACT FROM AUTHOR]

Tetramethyl-tetraselenafulvalene (TMTSF) and bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) are flagship precursors in the field of molecular (super)conductors. The electrocrystallization of these donors in the presence of (n-Bu4N)TaF6 or mixtures of (n-Bu4N)TaF6 and (n-Bu4N)PF6 provided Bechgaard salts formulated as (TMTSF)2(TaF6)0.84(PF6)0.16, (TMTSF)2(TaF6)0.56(PF6)0.44, (TMTSF)2(TaF6)0.44(PF6)0.56 and (TMTSF)2(TaF6)0.12(PF6)0.88, together with the monoclinic and orthorhombic phases δm-(BEDT-TTF)2(TaF6)0.94(PF6)0.06 and δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57, respectively. The use of BEDT-TTF and a mixture of (n-Bu4N)TaF6/TaF5 afforded the 1:1 phase (BEDT-TTF)2(TaF6)2·CH2Cl2. The precise Ta/P ratio in the alloys has been determined by an accurate single crystal X-ray data analysis and was corroborated with solution 19F NMR measurements. In the previously unknown crystalline phase (BEDT-TTF)2(TaF6)2·CH2Cl2 the donors organize in dimers interacting laterally yet no organic-inorganic segregation is observed. Single crystal resistivity measurements on the TMTSF based materials show typical behavior of the Bechgaard phases with room temperature conductivity σ ≈ 100 S/cm and localization below 12 K indicative of a spin density wave transition. The orthorhombic phase δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57 is semiconducting with the room temperature conductivity estimated to be σ ≈ 0.16–0.5 S/cm while the compound (BEDT-TTF)2(TaF6)2·CH2Cl2 is also a semiconductor, yet with a much lower room temperature conductivity value of 0.001 to 0.0025 S/cm, in agreement with the +1 oxidation state and strong dimerization of the donors. [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]

Introduction of chirality in the field of molecular conductors has received increasing interest in recent years in the frame of modulation of the crystal packing, and hence conducting properties, with the number of stereogenic centers and absolute configuration, e.g., racemic or enantiopure forms. Here, we describe the preparation by electrocrystallization of chiral radical cation salts, based on the donors methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF) 1 and ethyl-ethylenedithio-tetrathiafulvalene (Et-EDT-TTF) 2 containing one stereogenic center, with the perchlorate anion. Donor 1 provided the series of crystalline materials [(rac)-1]ClO4, [(S)-1]2ClO4 and [(R)-1]2ClO4, while for donor 2 only the 1:1 salts [(rac)-2]ClO4 and [(R)-2]ClO4 could be prepared as suitable single crystals for X-ray analysis. The enantiopure salts of 1 show β-type packing and metallic conductivity in the high temperature regime, with room temperature conductivity values of 5–10 S cm−1, whereas compound [(rac)-2]ClO4 is a very poor semiconductor. Tight-binding extended Hückel band structure calculations support the metallic conductivity of the enantiopure salts of 1 and suggest that small structural changes, possibly induced by thermal contraction or pressure, could lead to a pseudo-elliptic closed Fermi surface, typical for a 2D metal. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue is the group of Narcis Avarvari (CIMI team) at the Laboratory MOLTECH-Anjou, UMR 6200 CNRS - Université d'Angers, France. The cover image shows the enantiopure tetrathiafulvalene precursors used for the preparation of chiral radical cation conducting salts, together with an artwork of their packing diagrams and the suggested mirror image relationship between them. [ABSTRACT FROM AUTHOR]

The cover picture shows the mirror‐image relationship, like that between the two hands in the background, between two enantiopure dimethylbis(ethylenedithio)tetrathiafulvalene (DM‐BEDT‐TTF) precursors. Also shown are the solid‐state packing diagrams, represented in an artistic manner, of the mixed‐valence radical cation salts of these precursors with the hexachlororhenate(IV) dianion. These paramagnetic semiconducting chiral materials have been obtained by electrocrystallization, and their transport properties were determined by single‐crystal resistivity measurements, supported by band‐structure calculations. The organic/inorganic segregation shown in the picture is an important prerequisite for extensive electron delocalization, although charge localization occurs here in the donors. Details are discussed in the article by N. Avarvari et al. on p. 3855 ff. For more on the story behind the cover research, see the Cover Profile. [ABSTRACT FROM AUTHOR]