Structure and physical properties of a hydrogen-bonded self-assembled material composed of a carbamoylmethyl substituted TTF derivative

Abstract

Crystal structures of the carbamoylmethyl substituted TTF derivative AMET are characterized by polymeric hydrogen bonding between amide groups. As a result, the TTF moieties stack in parallel even in the neutral crystal. The nu;NH absorbtions of neutral AMET at 3426 and 3184cm1 show shifts to lower wavenumber, Delta;k, of 37 and 58cm1, respectively, at 4.1GPa. Therefore the shrinkage of the NH‥O distance is estimated to be ca. 0.04 at this pressure. The pressure dependence of the IR spectra of iodine-doped samples at doping ratios of less than 45 was exactly the same as that for a neutral sample, suggesting that the hydrogen bonding pattern is not affected significantly upon doping.Although crystalline AMET is an insulator in the neutral state (sigma;rt=ca. 108 Scm1), the conductivity is enhanced by a factor of 107 upon iodine doping of 45mol (sigma;rt=1.2101 Scm1). Furthermore, the conductivity increases as a function of the external pressure, and the sigma;rt of a 5 iodine-doped sample increased three-fold at 1.0GPa. The enhanced conductivity of iodine-doped samples may be ascribed to the increase in the overlap between the donor moieties based on the shrinkage of the hydrogen bond of the carbamoylmethyl group.