EXPERIMENTAL EVALUATION OF THE ELECTRON-INTRAMOLECULAR-VIBRATION COUPLING-CONSTANTS OF TETRAMETHYLTETRATHIAFULVALENE

The relevant electron-intramolecular vibrations coupling constants of tetramethyltetrathiafulvalene (TMTTF) have been experimentally obtaine d. The determination was possible studying the optical properties of d imers of TMTTF(+) in polymethyl-methacrylate films on the basis of a H olstein-Hubbard dimer model. Electron paramagnetic resonance measureme nts of the singlet-tripler energy gap of the dimers made possible the calculation of the coupling constants without the need for absolute va lues of the optical spectra and the knowledge of structural parameters . The values of the coupling constants show differences with previousl y reported values for TMTTF or related molecules like TTF and bis-ethy lenedithio-TTF (BEDT-TTF).