Pressure and temperature dependence of the electrical resistivity of a one-dimensional phthalocyanine conductor, NiPc(AsF6)0.5

The high-pressure optical measurement of NiPc(AsF6)0.5 suggests that a metal-nonmetal phase transition accompanies the pressure-induced metal-ligand charge transfer which begins at 0.5 GPa. To confirm this forecast we examined the pressure and temperature dependence of the electrical resistivity of NiPc(AsF6)0.5 up to 1.0 GPa. We found a resistance increase at 0.5 GPa where the metal-ligand charge transfer occurs. This nonmetallic state may be ascribed to the Anderson localization due to the random potential created by the metal-ligand charge transfer.