Tetramethyltetrathiafulvalenium Bromide Benzonitrile Water Solvate

The title compound, C₁₀H₁₂S₄⁺.Br⁻.0.5C₇H₅N.0.5H₂O, 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 Cs 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) Å. The central double-bond lengths of 1.394 (9) and 1.413 (8) Å are longer than the reported value of the corresponding C—C distance of 1.35 Å in TMTTF₂Br. This is consistent with the findings that the greater the charge on the tetrathiafulvalene cation the longer the C=C bond distance.

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