L-Edge X-ray Absorption Spectroscopic Investigation of {FeNO}6: Delocalization vs Antiferromagnetic Coupling

Year: 2016

Type: article

Abstract: NO is a classic non-innocent ligand, and iron nitrosyls can have different electronic structure descriptions depending on their spin state and coordination environment. These highly covalent ligands are found in metalloproteins and are also used as models for Fe–O 2 systems. This study utilizes iron L-edge X-ray absorption spectroscopy (XAS), interpreted using a valence bond configuration interaction multiplet model, to directly experimentally probe the electronic structure of the S = 0 {FeNO} 6 compound [Fe(PaPy 3 )NO] 2+ (PaPy 3 = N,N -bis(2-pyridylmethyl)amine- N -ethyl-2-pyridine-2-carboxamide) and the S = 0 [Fe(PaPy 3 )CO] + reference compound. This method allows separation of the σ-donation and π-acceptor interactions of the ligand through ligand-to-metal and metal-to-ligand charge-transfer mixing pathways. The analysis shows that the {FeNO} 6 electronic structure is best described as Fe III –NO(neutral), with no localized electron in an NO π* orbital or electron hole in an Fe dπ orbital. This delocalization comes from the large energy gap between the Fe–NO π-bonding and antibonding molecular orbitals relative to the exchange interactions between electrons in these orbitals. This study demonstrates the utility of L-edge XAS in experimentally defining highly delocalized electronic structures.

Source: Journal of the American Chemical Society

DOI: 10.1021/jacs.6b11260

Authors: James J. Yan, Margarita A. Gonzales, Pradip K. Mascharak, Britt Hedman, Keith O. Hodgson, Edward I. Solomon

Institutions: Stanford University, Foothill College, University of California, Santa Cruz, SLAC National Accelerator Laboratory, Stanford Synchrotron Radiation Lightsource

Language: English

Topic: X-ray Spectroscopy and Fluorescence Analysis

Subfield: Radiation

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, U.S. Department of Energy, National Institutes of Health, Office of Science, National Institute of General Medical Sciences, Division of Chemistry, Basic Energy Sciences, Biological and Environmental Research, SLAC National Accelerator Laboratory

OpenAlex ID: W2563972270