Features of metal atom 2p excitations and electronic structure of 3d-metal phthalocyanines studied by X-ray absorption and resonant photoemission

The metal atom 2p core excitations in 3d-metal phthalocyanines (MPcʹs, M = Ni, Co, Fe) have been studied via a combination of near edge X-ray absorption fine structure (NEXAFS) and resonant photoemission (ResPE) spectroscopy. On the basis of comparison of the corresponding spectra of NiPc, CoPc and FePc it has been shown that the presence of a partly filled molecular orbital (MO) dramatically affects the formation and decay processes of the M 2p core excitation in CoPc and, to a greater extend, in FePc due to the significant 3d–3d exchange interaction. It has been found that the low-lying unoccupied electronic states of NiPc, CoPc and FePc are strongly localized within the MN4 quasi-molecule and have nearly pure 3d character. Moreover, mainly 3d metallic character of the high-lying occupied MOs of NiPc, CoPc and FePc has been proved.