Ultraviolet Photoelectron Spectra of α- and β-Polymorphs of Copper Phthalocyanine

Abstract

Abstract The ultraviolet photoelectron spectra have been measured for α- and β-forms of copper phthalocyanine at 183 °C, to investigate the correlation of photoemissive behavior with crystal structure. Their threshold ionization potentials were 4.88 and 4.62 eV, with polarization energy of 1.27 and 1.53 eV, respectively. This difference could not be explained by calculation with point charge-point dipole approximation, but calculation with distributed charge on the cation and distributed induced dipoles on the nearest neighbor two molecules gave semi-quantitative agreement with the experimental findings.