International Tables for X-ray Crystallography. Errata

Abstract

The nitrogen Is binding energies of a series of porphyrins and several platinohematoporphyrin complexes obtained by x-ray photoelectron spectroscopy (XPS) are presented and discussed. The influence of different substituents at the periphery of the porphyrins has been studied; however, no significant change could be detected between the Njs binding energies of the porphyrins studied. A value of 2 eV has been found between aza and pyrrole type nitrogen binding energies. The nature of the sitting-atop (SAT) complex reported in the literature is discussed. XPS gives strong evidence for the existence of the SAT complex , cA-PtCl2H2(Hemato-IX). Two types of nitrogens located at 399.9 eV for N-H and at 398.6 eV for N-*Pt have been found in the SAT complex. Furthermore, the N]s region for the platinohematoporphyrin Pt(Hemato-IX) shows that the four nitrogens are equivalent. A value of 399.4 eV is found for the Njs binding energy of N-Pt where platinum is covalently bound to hematoporphyrin. The difference between the two types of nitrogen binding energies tends to zero in the series, H2(Hemato-IX) (£ = 2.3 eV)-* ris-PtCl2H2(Hemato-IX) (= 1.3 eV)-* Pt(Hemato-lX) (£ = 0 eV), indicating a tendency toward equivalency upon platinum insertion.