Charge transfer complexes and radical cation salts of chiral methylated organosulfur donors

Abstract

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-F 4 , 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-F 4. The TCNQ-F 4 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 AsF 6 and SbF 6 anions formulated as (TM-BEDT-TTF) 2 XF 6 (X = As, Sb). Electrical conductivity was only found in one charge transfer complex, while the radical cation salts are all semiconducting.

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

“…The same trend was also observed for the closely related donors DM-EDT-TTF [10,15] and DM-BEDT-TTF [22][23][24]. Only in very few cases mixed (ax,ax,eq,eq) conformations have been found in the solid state structures of 1 for charge transfer complexes with TCNQ [2], radical cation salts with the iron(III) chloroanilate complex anion [7], and a cycloadduct with tetrachlorocatecholate [25], while the all-ax conformation has been never observed. We describe herein the first crystalline enantiopure radical cation salt of TM-BEDT-TTF in which the oxidized donor adopts a (ax,ax,ax,ax) conformation.…”

“…It has been shown by theoretical calculations that in the gas phase the all-axial conformation is slightly more stable than the all-equatorial one, both being in equilibrium in solution [1] (Figure 1). While neutral 1 has been crystallized as both all-ax [2] and all-eq [1] conformers, its radical cation salts show in most cases all-eq conformation [1,2,5,6], very likely as a means to maximize the packing. The same trend was also observed for the closely related donors DM-EDT-TTF [10,15] and DM-BEDT-TTF [22][23][24].…”

“…Tetramethyl-bis(ethylenedithio)-tetrathiafulvalene 1 (TM-BEDT-TTF) has in principle several possible stereoisomers, yet the only ones which have been properly described are the (S,S,S,S) ( Figure 1) and (R,R,R,R) enantiomers [1][2][3], henceforth abbreviated (S)-1 and (R)-1, respectively.…”

“…Tetramethyl-bis(ethylenedithio)-tetrathiafulvalene 1 (TM-BEDT-TTF) has in principle several possible stereoisomers, yet the only ones which have been properly described are the (S,S,S,S) ( Figure 1) and (R,R,R,R) enantiomers [1][2][3], henceforth abbreviated (S)-1 and (R)-1, respectively. (S)-1 represents the first example of a chiral TTF derivative [4], and its synthesis allowed the preparation of several TTF based chiral conducting radical cation salts by electrocrystallization [1,5], including the ferromagnetic metal [TM-BEDT-TTF]x[MnCr(ox)3] (ox = oxalate) [6] or the paramagnetic semiconductor [TM-BEDT-TTF]3(PPh4)[K I Fe III (Cl2An)3] (Cl2An = dichloroanilate) [7].…”

Isolation of a chiral anthracene cation radical: X-ray crystallography and computational interrogation of its racemization

“…For example, it was shown for several radical-cation salts that enantiopure materials show enhanced conductivity when compared with the corresponding racemic mixtures owing to the structural disorder. 5,6 …”