Enantiopure Radical Cation Salt Based on Tetramethyl-Bis(ethylenedithio)-Tetrathiafulvalene and Hexanuclear Rhenium Cluster

Abstract

Electrocrystallization of the (S,S,S,S) enantiomer of tetramethyl-bis(ethylenedithio)-tetrathiafulvalene donor 1 in the presence of the dianionic hexanuclear rhenium (III) cluster [Re 6 S 6 Cl 8 ] 2á ffords a crystalline radical cation salt formulated as [(S)-1] 2¨R e 6 S 6 Cl 8 , in which the methyl substituents of the donors adopt an unprecedented all-axial conformation. A complex set of intermolecular TTF¨¨¨TTF and cluster¨¨¨TTF interactions sustain an original tridimensional architecture.

Conducting chiral nickel(ii) bis(dithiolene) complexes: structural and electron transport modulation with the charge and the number of stereogenic centres

“…40 As a comparison, the all-eq conformation is largely more often encountered in the solid state structures of tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) based radical cation salts, although mixed ax-eq or all-ax conformations occasionally occurred as well. 49,50 Here we observe that the ax or eq conformation can be also influenced by the racemic or enantiopure configuration of the complexes, yet they are isostructural. Accordingly, in (TBA)[Ni(S-me-dddt)2] and (TBA)[Ni(R-me-dddt)2], the cis isomer presents the all-ax conformation and the trans isomer the ax-eq one, while in the racemic complex, with both independent molecules as trans isomers, the all-ax conformation is observed.…”

Conformational Study and Chiroptical Properties of Chiral Dimethyl-Ethylenedithio-Tetrathiafulvalene (DM-EDT-TTF)

“…1), while in the meso compounds they are necessarily cis (ax, eq). [13] In the corresponding radical cation salts the most often encountered conformation is, by far, the all-equatorial one [2,4,7,9a-c,10] but in a very few cases mixed (ax, ax, eq, eq) [9c-d,14] or all-axial [15] conformations have been observed as well for TM-BEDT-TTF derivatives. Clearly, the most important consequence of this conformational issue in the case of the crystalline radical cation salts is for the donor packing, which strongly influences the electron transport properties, while in the case of the neutral precursors different chiroptical properties could possibly arise.…”

Unusual stoichiometry, band structure and band filling in conducting enantiopure radical cation salts of TM-BEDT-TTF showing helical packing of the donors

“…While in most of the salts described to date the donors show an all-eq conformation, favouring intermolecular face-to-face overlap, the all-ax 27 and mixed (ax, ax, eq, eq) 26 conformations have been occasionally observed as well. In our ongoing search for chiral TTF based crystalline conductors with extensive expression of chirality in the packing we have focused on the association of TM-BEDT-TTF with the Lindqvist type dianion [Mo 6 O 19 ] 2À .…”

“…14 Whereas several methyl substituted chiral BEDT-TTF and EDT-TTF derivatives, such as DM-BEDT-TTF, [13][14][15][16] DM-EDT-TTF, [8][9][10]17 DM-EDT-TTF diamides, 18 or Me-EDT-TTF, 19,20 provided interesting conducting materials, TM-BEDT-TTF still remains the flagship donor of this family of chiral precursors when considering the number of reported radical cation salts based on the enantiomers of TM-BEDT-TTF and various anions of different shapes, charge and magnetic properties. Indeed, several crystalline salts formulated as (TM-BEDT-TTF) 2 XF 6 (X = P, As, Sb), 21 (TM-BEDT-TTF)I 3 , 22 (TM-BEDT-TTF) 3 (XO 4 ) 2 (X = Cl, Re), 23 (TM-BEDT-TTF) x [MnCr(ox) 3 ] (ox = oxalate), 24 (TM-BEDT-TTF)[(rac)-TRISPHAT], 25 (TM-BEDT-TTF) 3 (PPh 4 )[KFe(Cl 2 An) 3 ] (Cl 2 An = dichloroanilate), 26 or (TM-BEDT-TTF) 2 (Re 6 S 6 Cl 8 ), 27 obtained by electrocrystallization and showing semiconducting or metallic behaviour, have been described over the years since the initial report on TM-BEDT-TTF. 1 However, in spite of the presence of stereogenic centres on the donor and, thus, crystallization in non-centrosymmetric space groups, expression of chirality at the crystal level, such as helical packing, was never achieved within TM-BEDT-TTF salts contrary to DM-EDT-TTF in (DM-EDT-TTF) 2 ClO 4 , for which the two enantiomeric compounds crystallized in the enantiomorphic hexagonal space groups P6 2 22 and P6 4 22, with, however, the helical axis perpendicular to the stacking direction of the donors.…”