Structures and energetics study of tetrathiafulvalene-based donors of organic superconductors

The donors of the best organic superconductors are all based on organic donor molecules (X) containing a core of tetrathiafulvalene (TTF) or a Se-substituted derivative. In this paper, we present ab initio quantum mechanical calculations (HF, MP2, and DFT using the 6-31G** basis) for the optimized structures and other properties of TTF-based organic donors X and X⁺. We find that X⁺ is planar but that X deforms to a boat structure. The cases in which the boat is most stabilized with respect to the planar conformation are observed to be superconductors.