Issue 36, 2024

Metal–ligand delocalization of iron and cobalt porphyrin complexes in aqueous solutions probed by soft X-ray absorption spectroscopy

Abstract

Metal–ligand delocalization of metal porphyrin complexes in aqueous solutions was investigated by analyzing the electronic structure of both the metal and ligand sides using soft X-ray absorption spectroscopy (XAS) at the metal L2,3-edges and nitrogen K-edge, respectively. In the N K-edge XAS spectra of the ligands, the energies of the C[double bond, length as m-dash]N π* peaks of cobalt protoporphyrin IX (CoPPIX) are higher than iron protoporphyrin IX (FePPIX). The energy difference between the two lowest peaks in the XAS spectrum of CoPPIX is also larger than that of FePPIX. Nitrogen K-edge inner-shell calculations of metalloporphyrins with different central metals indicate that the energy differences between these peaks reflect the electronic configurations and spin multiplicities of metalloporphyrins. We also investigated the hydration structure of CoPPIX in aqueous solution by analyzing the electronic structure of the ligand and revealed that CoPPIX maintains its five-coordination geometry in aqueous solution. The present study shows high performance of N K-edge XAS of ligands for studying the coordination structures of metalloporphyrins in solutions rather than the metal L2,3-edges of central metals.

Graphical abstract: Metal–ligand delocalization of iron and cobalt porphyrin complexes in aqueous solutions probed by soft X-ray absorption spectroscopy

Supplementary files

Article information

Article type
Paper
Submitted
24 May 2024
Accepted
27 Aug 2024
First published
27 Aug 2024
This article is Open Access
Creative Commons BY-NC license

Phys. Chem. Chem. Phys., 2024,26, 23636-23645

Metal–ligand delocalization of iron and cobalt porphyrin complexes in aqueous solutions probed by soft X-ray absorption spectroscopy

M. Nagasaka, S. Tsuru and Y. Yamada, Phys. Chem. Chem. Phys., 2024, 26, 23636 DOI: 10.1039/D4CP02140A

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