New functionalized tetrathiafulvalenes: X-ray crystal structures and physico-chemical properties of TTF-C(O)NMe2 and TTF-C(O)-O-C4H9: a joint experimental and theoretical study

The synthesis of the new mono- and di-functionalized tetrathiafulvalene (TTF) derivatives 4, 5 and 12-15 is reported. Compounds 4 and 5 have been studied in detail: their single crystal X-ray structures are reported and theoretical calculations at both semiempirical and ab initio levels have been performed. The TTF moiety in the crystal of 4 is folded, whereas in the crystal of 5 it is essentially planar. In the crystal structure of 4 the molecules related via an inversion centre form close dimers which pack in a severely distorted kappa-arrangement. Molecules of 5 assemble into uniform stacks with TTF moieties overlapping the side chains of adjacent molecules. Calculated geometries are in good agreement with the X-ray data, and the distortion from planarity in the crystal of 4 can be explained by nonbonding interactions between the amide substituent and the TTF rings of adjacent molecules. Evidence for intramolecular charge-transfer from the TTF ring to the electron-withdrawing amide and ester substituents of 4 and 5, respectively, is provided by UV-VIS spectroscopy in solution, analysis of the bond lengths in the crystal structure, and by theoretical calculations.