1H- and 13C-NMR in the organic conductor DMTM(TCNQ)2

Abstract

The electronic and dynamic changes at the phase transition at Tc = 272 K in the quasi one-dimensional organic conductor DMTM(TCNQ)2 have been investigated with 1H- and 13C-NMR on powder samples and single crystals. The TCNQ hyperfine coupling constants were calculated from the observed 1H- and 13C-Knight shift, and the charge redistribution at Tc is determined by the 13C single crystal measurements. The DMTM cation dynamics have been studied with broadline 1H-NMR which indicates a slowing down of cation motion at Tc as evidenced by the temperature dependence of the relaxation rates. The results support a tentative explanation of the unusual phase transition, an “inverted Peierls” transition, given by Visser et al. [1,2].