TETRAMETHYLTETRATHIAFULVALENIUM BROMIDE BENZONITRILE WATER SOLVATE

The title compound, C10H12S4+.Br-.0.5C(7)H(5)N.O.5H(2)0, is a cation-r adical salt of tetramethyltetrathiafulvalene (TMTTF) and bromine with a ratio of TMTTF to Br of 1:1. The TMTTF cations have crystallographic ally imposed C-s symmetry with mirror planes at y = 0 and y = 1/2 whic h lie along the central C=C bonds. The cations are stacked to form a c olumn structure extending along the c axis and face each other to assu me dimeric structures around the inversion centres, with short S...S c ontacts of 3.430(2) and 3.508 (2) Angstrom. The central double-bond le ngths of 1.394(9) and 1.413(8) Angstrom are longer than the reported v alue of the corresponding C-C distance of 1.35 Angstrom in TMTTF2Br. T his is consistent with the findings that the greater the charge on the tetrathiafulvalene cation the longer the C=C bond distance.