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© 2020 by the authors., 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., This research was partially funded in France by the National Agency for Research (ANR), Project 15-CE29-0006-01 ChiraMolCo, in Spain by the Spanish MICIU through Grant PGC2018-096955-B-C44 and the Severo Ochoa FUNFUTURE (CEX2019-000917-S) Excellence Center distinction, as well as by Generalitat de Catalunya (2017SGR1506) and in Portugal by FCT under contracts UIDB/04349/2020 and LISBOA-01-0145-FEDER-029666. This work was supported in France by the CNRS and the University of Angers. The collaboration between the Portuguese and French team members was also supported by a FCT–French Ministry of Foreign Affairs bilateral action FCT/PHC-PESSOA 2020-21 (Project 44647UB)., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

International audience; The occurrence of isostructural conducting radical cation salts of diversely substituted tetrathiafulvalene (TTF) precursors with the same anion is most often limited to very similar derivatives such as tetramethyl-tetrathiafulvalene (TMTTF) and tetramethyl-tetraselenafulvalene (TMTSF). Here we show that the use of the oxo-bis[pentafluorotantalate(V)] dianion [Ta2F10O]2− affords upon electrocrystallization of TMTTF, TMTSF, bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF), racemic dimethyl-ethylenedithio-tetrathiafulvalene ((rac)-DM-EDT-TTF), and enantiopure (S,S)-DM-EDT-TTF a series of mixed valence crystalline radical cation salts with the same 3 : 1 stoichiometry. The donor layers show similar features in the five materials, such as alternation of trimeric units within stacks which arrange in parallel columns of β-type. The anion arranges either parallel or perpendicular to the stack direction and establishes numerous intermolecular CH⋯F hydrogen bonds. Thus, the [Ta2F10O]2− dianion, most likely because of its shape and propensity to engage in hydrogen bonding, is the first one to be able to induce the same type of structural arrangement for a broad series of different donors, a result which is important in the crystal engineering of molecular conductors. All the compounds are band gap semiconductors, according to single crystal resistivity measurements and extended Hückel band structure calculations. The room temperature conductivity values are relatively high, i.e. 0.25–1.1 S cm−1, except for the TMTTF salt, whose conductivity value is two orders of magnitude smaller than its isostructural TMTSF counterpart, in agreement with the band gap energy value. As a general feature of these materials, variations in the inter- and intra-trimer interactions modulate their band structure, i.e. energy dispersion and band gaps. The preparation of this series of radical cation salts with a sturdy 3 : 1 stoichiometry might question previous assignments of the anion as [Ta2F11]− in radical cation salts of TMTSF and BEDT-TTF.

The occurrence of isostructural conducting radical cation salts of diversely substituted tetrathiafulvalene (TTF) precursors with the same anion is most often limited to very similar derivatives such as tetramethyltetrathiafulvalene (TMTTF) and tetramethyl-tetraselenafulvalene (TMTSF). Here we show that the use of the oxo-bis[pentafluorotantalate(V)] dianion [Ta2F10O]2 affords upon electrocrystallization of TMTTF, TMTSF, bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF), racemic dimethyl-ethylenedithio-tetrathiafulvalene ((rac)- DM-EDT-TTF), and enantiopure (S,S)-DM-EDT-TTF a series of mixed valence crystalline radical cation salts with the same 3 : 1 stoichiometry. The donor layers show similar features in the five materials, such as alternation of trimeric units within stacks which arrange in parallel columns of b-type. The anion arranges either parallel or perpendicular to the stack direction and establishes numerous intermolecular CH/F hydrogen bonds. Thus, the [Ta2F10O]2 dianion, most likely because of its shape and propensity to engage in hydrogen bonding, is the first one to be able to induce the same type of structural arrangement for a broad series of different donors, a result which is important in the crystal engineering of molecular conductors. All the compounds are band gap semiconductors, according to single crystal resistivity measurements and extended Huckel band structure calculations. The room temperature conductivity ¨ values are relatively high, i.e. 0.25–1.1 S cm 1 , except for the TMTTF salt, whose conductivity value is two orders of magnitude smaller than its isostructural TMTSF counterpart, in agreement with the band gap energy value. As a general feature of these materials, variations in the inter- and intra-trimer interactions modulate their band structure, i.e. energy dispersion and band gaps. The preparation of this series of radical cation salts with a sturdy 3 : 1 stoichiometry might question previous assignments of the anion as [Ta2F11] in radical cation salts of TMTSF and BEDT-TTF., This work was supported in France by the National Agency for Research (ANR, Project 15-CE29-0006-01 ChiraMolCo), the CNRS and the University of Angers. Work at Bellaterra (Spain) was supported by the Spanish MICIU through Grant PGC2018-096955-B-C44 and the MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2015-0496 as well as by Generalitat de Catalunya (2017SGR1506).

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 b-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., This work was supported in France by the CNRS and the University of Angers. The collaboration between the Portuguese and French team members was also supported by a FCT – French Ministry of Foreign Affairs bilateral action FCT/PHC-PESSOA 2020-21 (Project 44647UB).

Puzzled by the unusual conducting behavior of the as described (TMTSF)3Ta2F11 radical cation salt[1] (TMTSF = tetramethyl-tetraselenafulvalene) and the potential interest of the Ta2F11 monoanion in other molecular conductors, we have decided to revisit and extend the family of TTF radical cation salts containing this particular anion. During our investigation it turned out that the real anionic species was in fact the Ta2OF10 dianion.In this work we describe the structures, conductivity and band structure calculations of the (TMTXF)2Ta2OF10 hybrid salts (X = S or Se). We also present the new (DM-EDT-TTF)3Ta2OF10 materials based on the chiral donor dimethyl-ethylenedithio-tetrathiafulvalene (DM-EDT-TTF).

International audience; This work presents and analyzes electrical resistivity data on the organic superconductor (TMTSF) 2 ClO 4 and their anion-substituted alloys (TMTSF) 2 (ClO 4) 1−x (ReO 4) x along the least conducting c axis. Nonmagnetic disorder introduced by finite size domains of anion ordering on non-Fermi-liquid character of resistivity is investigated near the conditions of quantum criticality taking place at x = 0. The evolution of the T-linear resistivity term with anion disorder shows a limited decrease in contrast with the complete suppression of the critical temperature T c as expected for unconventional superconductivity beyond a threshold value of x. The resulting breakdown of scaling between both quantities is compared to the theoretical predictions of a linearized Boltzmann equation combined to the scaling theory of umklapp scattering in the presence of disorder-induced pair breaking for the carriers. The theory shows that quantum antiferromagnetic fluctuations, which are at the core of unconventional Cooper pairing and inelastic scattering of T-linear resistivity in these systems, are weakly affected by disorder while the phase coherence responsible for a finite T c can be completely suppressed.

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