Deuteration Effect and Possible Origin of the Charge-Ordering Transition of (TMTTF)2X

ESR, NMR and X-ray measurements were performed for pristine and fully perdeuterio-TMTTF, TMTTF- d 12 salts. Significant enhancement by deuteration of the charge-order phase transition temperature, T CO , was observed in ESR measurements for all (TMTTF) 2 X salts measured. No obvious relation between the SbF 6 anion motion and the TMTTF charge-order was found by 19 F NMR. We also performed single crystal X-ray measurements to understand the deuteration effects and temperature dependence of the crystal structure. A possible relationship between the T CO 's and crystallographical parameters is proposed. The deuteration effects and possible origin of the charge-ordering transition of TMTTF salts are discussed.