Isotope effect on metal–insulator transition of (EDO-TTF)2XF6 (X = P, As) with multi-instability of metallic state

Abstract The partially deuterated 4,5-ethylenedioxy-tetrathiafulvalene- d 2 (EDO-TTF- d 2 ) was synthesized from the undeuterated EDO-TTF- d 0 . The single crystals of (EDO-TTF- d 2 ) 2 XF 6 (X = P, As) were prepared by the conventional electrocrystallization technique. The deuterium contents of EDO-TTF- d 2 itself and the radical cation salts were 99% D by mass spectral analysis. The magnetic susceptibility measurement revealed that (EDO-TTF- d 2 ) 2 XF 6 undergoes a metal–insulator transition at 2–3 K higher temperature than the undeuterated salts. In infrared and Raman spectra, significant isotope shifts were observed not only on C–H vibrational modes but also on TTF-skeletal modes. The assignment of experimental bands was performed on the basis of normal-mode analysis at B3LYP/6-31G(d,p) level of theory.