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The x-ray photoelectron spectra of tetraphenylporphin, phthalocyanine and their copper complexes were measured. The copper complexes show a single nitrogen 1s photoline, whereas the metal free bases give rise to a doublet nitrogen 1s photoline. The central pyrrole and aza nitrogens in the metal free bases could be identified, whereas the central and meso-bridging aza nitrogens in phthalocyanine could not be discriminated. Each of the central two protons in the metal free bases is localized on one of the central four porphinato nitrogens. The shifts in N 1s binding energy observed in the present work could be reproduced by the shifts in the charge density on nitrogen obtained for the bonded structure by an extended Hückel molecular orbital calculation.
Niwa et al. (Fri,) studied this question.