Electronic state of a new organic conductor (TTM-TTP)I-3 with a one-dimensional half-filled band

C-13 NMR measurements have been carried out to investigate the nature of the electronic state of the one-dimensional half-filled band system, (TTM-TTP)I-3. Metal-insulator transition at around 120 K was observed through the temperature dependence of NMR relaxation rate, 1/T-1. From the analysis of NMR spectra in the insulating state, it is strongly suggested that charge disproportionation with the valences of the TTM-TTP molecules 2-0-2-0 exists along the stacking axis. (C) 2000 Elsevier Science Ltd. All rights reserved.