Crystal structure of tetramethyltetrathiafulvalenium (1S)-camphor-10-sulfonate dihydrate

Abstract

Electro-oxidation of tetramethyltetrathiafulvalene (TMTTF) in the presence of the chiral anion (1S)-camphor-10-sulfonate (S-camphSO3−) in tetrahydrofuran/water medium afforded a 1/1 salt formulated as TMTTF·S-camphSO3·2H2O or 2-(4,5-dimethyl-1,3-dithiol-2-ylidene)-4,5-dimethyl-1,3-dithiole radical ion (1+) [(1S)-7,7-dimethyl-2-oxobicyclo[2.2.1]heptan-1-yl]methanesulfonate dihydrate, C10H12S4+·C10H15O4S−·2H2O. In this salt, two independent TMTTF units are present but, in both cases, the observed bond lengths and especially the central C=C distance [1.392 (6) and 1.378 (6) Å] are in agreement with a complete oxidation of TMTTF which is thus present as TMTTF.+ radical cations. These cations form one-dimensional stacks in which they are associated two by two, forming dimers with short [3.472 (1) to 3.554 (2) Å] S...S contacts. The two S-camphSO3 anions present also form stacks and are connected with each other via the water molecules with many O—H...O hydrogen bonds ranging from 1.86 (3) to 2.15 (4) Å; the O—H...O hydrogen-bonding network can be described as being constituted of C22(6) chains bearing R33(11) lateral rings. On the other hand, the columns of cations and anions are connected through C—H...O hydrogen bonds, forming a system expanding in three directions; finally, the result is a three-dimensional network of O—H...O and C—H...O hydrogen bonds.

Keywords

• crystal structure
• tetrathiafulvalene-based materials
• chirality
• hydrogen bonding