Issue 22, 2015

Orbital entanglement and CASSCF analysis of the Ru–NO bond in a Ruthenium nitrosyl complex

Abstract

Complete active space self-consistent field (CASSCF) wavefunctions and an orbital entanglement analysis obtained from a density-matrix renormalisation group (DMRG) calculation are used to understand the electronic structure, and, in particular, the Ru–NO bond of a Ru nitrosyl complex. Based on the configurations and orbital occupation numbers obtained for the CASSCF wavefunction and on the orbital entropy measurements evaluated for the DMRG wavefunction, we unravel electron correlation effects in the Ru coordination sphere of the complex. It is shown that Ru–NO π bonds show static and dynamic correlation, while other Ru–ligand bonds feature predominantly dynamic correlation. The presence of static correlation requires the use of multiconfigurational methods to describe the Ru–NO bond. Subsequently, the CASSCF wavefunction is analysed in terms of configuration state functions based on localised orbitals. The analysis of the wavefunctions in the electronic singlet ground state and the first triplet state provides a picture of the Ru–NO moiety beyond the standard representation based on formal oxidation states. A distinct description of the Ru and NO fragments is advocated. The electron configuration of Ru is an equally weighted superposition of RuII and RuIII configurations, with the RuIII configuration originating from charge donation mostly from Cl ligands. However, and contrary to what is typically assumed, the electronic configuration of the NO ligand is best described as electroneutral.

Graphical abstract: Orbital entanglement and CASSCF analysis of the Ru–NO bond in a Ruthenium nitrosyl complex

Associated articles

Article information

Article type
Paper
Submitted
13 Nov 2014
Accepted
23 Feb 2015
First published
10 Mar 2015
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2015,17, 14383-14392

Author version available

Orbital entanglement and CASSCF analysis of the Ru–NO bond in a Ruthenium nitrosyl complex

L. Freitag, S. Knecht, S. F. Keller, M. G. Delcey, F. Aquilante, T. Bondo Pedersen, R. Lindh, M. Reiher and L. González, Phys. Chem. Chem. Phys., 2015, 17, 14383 DOI: 10.1039/C4CP05278A

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