Re-evaluating the Cu K pre-edge XAS transition in complexes with covalent metal–ligand interactions

Tomson, N. C., Williams, K. D., Dai, X., Sproules, S. , DeBeer, S., Warren, T. H. and Wieghardt, K. (2015) Re-evaluating the Cu K pre-edge XAS transition in complexes with covalent metal–ligand interactions. Chemical Science, 6, pp. 2474-2487. (doi: 10.1039/C4SC03294B)

Abstract

Three [Me2NN]Cu(h2 -L2) complexes (Me2NN ¼ HC[C(Me)NAr]2; L2 ¼ PhNO (2), ArF 2N2 (3), PhCH]CH2 (4); Ar ¼ 2,6-Me2-C6H3; ArF ¼ 3,5-(CF3)2-C6H3) have been studied by Cu K-edge X-ray absorption spectroscopy, as well as single- and multi-reference computational methods (DFT, TD-DFT, CASSCF, MRCI, and OVB). The study was extended to a range of both known and theoretical compounds bearing 2p-element donors as a means of deriving a consistent view of how the pre-edge transition energy responds in systems with significant ground state covalency. The ground state electronic structures of many of the compounds under investigation were found to be strongly influenced by correlation effects, resulting in ground state descriptions with majority contributions from a configuration comprised of a Cu(II) metal center anti-ferromagentically coupled to radical anion O2, PhNO, and ArF 2N2 ligands. In contrast, the styrene complex 4, which displays a Cu K pre-edge transition despite its formal d10 electron configuration, exhibits what can best be described as a Cu(I):(styrene)0 ground state with strong pbackbonding. The Cu K pre-edge features for these complexes increase in energy from 1 to 4, a trend that was tracked to the percent Cu(II)-character in the ground state. The unexpected shift to higher preedge transition energies with decreasing charge on copper (QCu) contributed to an assignment of the pre-edge features for these species as arising from metal-to-ligand charge transfer instead of the traditional Cu1s / Cu3d designation.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Sproules, Dr Stephen
• Authors: Tomson, N. C., Williams, K. D., Dai, X., Sproules, S., DeBeer, S., Warren, T. H., and Wieghardt, K.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Chemical Science
• Publisher: Royal Society of Chemistry
• ISSN: 2041-6520
• ISSN (Online): 2041-6539
• Copyright Holders: Copyright © 2015 The Royal Society of Chemistry
• First Published: First published in Chemical Science
• Publisher Policy: Reproduced under a Creative Commons License