NEXAFS spectra of metallotetraphenylporphyrins with adsorbed nitrogen monoxide

Near edge X-ray absorption fine structure (NEXAFS) spectra of nitrogen K-edge region were obtained using total electron yield detection for four metallotetraphenylporphyrins (M-TPPs) (M=Cr, Co, Zn and Ru) before and after nitrogen monoxide (NO) adsorption. The observed spectra of all M-TPPs were drastically changed by NO adsorption. The difference spectra showed new intense peaks appearing around 404 eV for all M-TPPs. Furthermore, small peaks below 400 eV corresponding to pi* transitions were observed for ZnTPP and CrTPP. Comparison of these results and oxidation potentials for M-TPPs revealed that NO is adsorbed only at ligand for ZnTPP, at only central metal for CoTPP and RuTPP, and at both ligand and the central metal for CrTPP. (C) 2001 Elsevier Science B.V. All rights reserved.