Theoretical Chemistry Accounts

, Volume 124, Issue 3–4, pp 251–259 | Cite as

A multiconfigurational perturbation theory study of the electronic structure and EPR g values of an oxomolybdenum enzyme model complex

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Abstract

We have studied the electronic structure (ground and excited states) and g matrix of a model compound for oxomolybdenum enzymes featuring the MoO–dithiolate moiety in C s symmetry, by means of multiconfigurational second-order perturbation theory (CASPT2) for a range of fold angles (5–29°), i.e. the angle between the S–Mo–S and S–C–C–S planes of the dithiolate ligand. We found no evidence of a suggested 3-center pseudo-σ bonding interaction between the singly occupied orbital of the ground state and the symmetric in-plane dithiolate orbital (Inscore et al. in Inorg Chem 38:1401–1410, 1999). This is complemented with our alternative assignment of band 4 in the electronic spectrum as the transition out of the a″ instead of the a′ dithiolate in-plane orbital into the singly occupied ground-state orbital, believed to probe the dominant hole superexchange pathway (Inscore et al. in Inorg Chem 38:1401–1410, 1999; Burgmayer et al. in J Inorg Biochem 101:1601–1616, 2007). Principal g values of 1.9652, 1.9090, 2.0003 were obtained at a fold angle of 21°. The latter value is so close to the free electron g e factor is due to an important positive contribution from the LMCT transition corresponding to band 4, counteracting the negative contributions from the ligand field transitions.

Keywords

Multiconfigurational methods Electronic structure EPR Molybdenum enzymes 
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Notes

Acknowledgments

This investigation was supported by grants from the Concerted Research Action of the Flemish Government (GOA) and the Flemish Science Foundation (FWO) of which S. V. is a fellow.

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  1. 1.K.U.LeuvenHeverleeBelgium

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