Infrared and Raman spectroscopic studies on the H–D equilibrium isotope effect in the electron-transfer equilibrium of thianthrene and its radical cation

Infrared and resonance Raman spectra of thianthrene (Th), perdeuteriated thianthrene ([2H8]Th) and their radical cation perchlorates (Th˙+ClO–4 and [2H8]Th˙+ClO–4, respectively) have been measured. Comparison of the frequency shifts caused by the perdeuteriation and the radical cation formation of thianthrene enables evaluation of the free energy change of 137 cal mol–1 for the electron-exchange equilibrium Th +[2H8]Th˙+⇌ Th˙++[2H8]Th.