Unoccupied electronic states of 3d-transition metal phthalocyanines (MPc: M=Mn, Fe, Co, Ni, Cu and Zn) studied by inverse photoemission spectroscopy

Abstract

Unoccupied electronic states of thin films of 3d-metal phthalocyanines (MPc: M=Mn, Fe, Co, Ni, Cu and Zn) and metal-free phthalocyanine (H 2Pc) were investigated by inverse photoemission spectroscopy. The experimental results were analyzed with emphasis on the contribution of the 3d-metal orbitals to the lower unoccupied electronic states of MPc. The difference spectra between the sample MPc (M=Mn, Fe, Ni and Cu) and the reference ZnPc were found to be in fair agreement with the previously reported X-ray absorption spectra in the energy regions corresponding to the core excitation of the central metals. This shows that the difference spectra exhibit the partial density of states attributed to the central metals. A comparison of the 3d-metal orbital contributions was also made between the experimental difference spectra and reported results from extended Hückel and density functional calculations.