Charge ordering in the one dimensional half-filled band system, (TTM-TTP)I-3

C-13-NMR measurements have been carried out to investigate the nature of th e electronic properties of the one-dimensional half-filled band system, (TT M-TTP)I-3. It is known that this compound is metallic down to 160K. The met al-insulator transition into a non-magnetic ground state was confirmed from the temperature dependence of NMR relaxation rate. In addition, it was fou nd that C-13-NMR spectra split into two in the insulating state. This is a evidence of charge disproportionation among the organic molecules. It may b e considered as a typical CDW formation in a 1D half-filled system with lar ge intersite Coulomb repulsion.