Theoretical estimation of the electron–molecular vibration coupling in several organic donor molecules

The electron–molecular vibration (EMV) coupling constants and the accompanying vibronic energy values of five kinds of organic donor molecules (TTF +1, TTP +1, TTPY +1, TOF +1 and TSF +1) are crucial ingredients of metallic organic salts, and have been theoretically estimated in order to systematically investigate their dependencies on the molecular structures. The effect of the replacement of sulfur atoms in TTF +1 with oxygen and selenium atoms (TOF +1 and TSF +1) has been paid particular attention. It has been found that the EMV coupling constant decreases in the order of TOF +1>TTF +1>TSF +1>TTP +1>TTPY +1. That is, the smaller coupling constants appear in the larger-sized molecule with heavier atoms.