Tetramethyltetrathiafulvalenium Bromide Benzonitrile Water Solvate

The title compound, C 10 H 12 S 4 + .Br - .0.5C 7 H 5 N.0.5H 2 O, is a cation-radical salt of tetramethyltetrathiafulvalene (TMTTF) and bromine with a ratio of TMTTF to Br of 1:1. The TMTTF cations have crystallographically imposed C s symmetry with mirror planes at y = 0 and y = 1/2 which lie along the central C=C bonds. The cations are stacked to form a column structure extending along the c axis and face each other to assume dimeric structures around the inversion centres, with short S...S contacts of 3.430 (2) and 3.508 (2) A. The central double-bond lengths of 1.394(9) and 1.413(8)A are longer than the reported value of the corresponding CC distance of 1.35 A in TMTTF 2 Br. This is consistent with the findings that the greater the charge on the tetrathiafulvalene cation the longer the C=C bond distance.