Insulator–metal transition induced by band-filling modulation in molecular Mott insulators†

Abstract

Metallic x-Li(Pc)Br_x and x-Li(tbp)I_x were fabricated via halogen doping of the Mott insulators x-Li(Pc) and x-Li(tbp), where Pc and tbp denote the phthalocyaninato and tetrabenzoporphyrinato ligands, respectively. Crystal structure analyses revealed that halogen atoms in x-Li(Pc)Br_x and x-Li(tbp)I_x penetrated the channels of the pristine x-Li(Pc) and x-Li(tbp) during the chemical oxidation of the ligands. Raman spectroscopy indicated that bromine and iodine exist as Br₃⁻ and I₃⁻, whereas iodine in the previously reported x-Li(Pc)I exists as I₅⁻. These findings suggest that band-filling modulation by halogen doping depends on both the halogen species and the π-ligand. Although x-Li(Pc)Br_x was unstable during heat treatment, the dedoping process was successfully achieved using a reductant, demonstrating that the electronic states between the Mott insulating and metallic states can be chemically controlled.