A step beyond the Feltham-Enemark notation: spectroscopic and correlated ab initio computational support for an antiferromagnetically coupled M(II)-(NO)- description of Tp*M(NO) (M = Co, Ni)

Tomson, N. C., Crimmin, M. R., Petrenko, T., Rosebrugh, L. E., Sproules, S. , Boyd, W. C., Bergman, R. G., DeBeer, S., Toste, F. D. and Wieghardt, K. (2011) A step beyond the Feltham-Enemark notation: spectroscopic and correlated ab initio computational support for an antiferromagnetically coupled M(II)-(NO)- description of Tp*M(NO) (M = Co, Ni). Journal of the American Chemical Society, 133(46), pp. 18785-18801. (doi:10.1021/ja206042k)

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Abstract

Multiple spectroscopic and computational methods were used to characterize the ground-state electronic structure of the novel {CoNO}9 species Tp*Co(NO) (Tp* = hydro-tris(3,5-Me2-pyrazolyl)borate). The metric parameters about the metal center and the pre-edge region of the Co K-edge X-ray absorption spectrum were reproduced by density functional theory (DFT), providing a qualitative description of the Co–NO bonding interaction as a Co(II) (SCo = 3/2) metal center, antiferromagnetically coupled to a triplet NO– anion (SNO = 1), an interpretation of the electronic structure that was validated by ab initio multireference methods (CASSCF/MRCI). Electron paramagnetic resonance (EPR) spectroscopy revealed significant g-anisotropy in the S = 1/2 ground state, but the linear-response DFT performed poorly at calculating the g-values. Instead, CASSCF/MRCI computational studies in conjunction with quasi-degenerate perturbation theory with respect to spin–orbit coupling were required for obtaining accurate modeling of the molecular g-tensor. The computational portion of this work was extended to the diamagnetic Ni analogue of the Co complex, Tp*Ni(NO), which was found to consist of a Ni(II) (SNi = 1) metal center antiferromagnetically coupled to an SNO = 1 NO–. The similarity between the Co and Ni complexes contrasts with the previously studied Cu analogues, for which a Cu(I) bound to NO0 formulation has been described. This discrepancy will be discussed along with a comparison of the DFT and ab initio computational methods for their ability to predict various spectroscopic and molecular features.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Sproules, Dr Stephen
Authors: Tomson, N. C., Crimmin, M. R., Petrenko, T., Rosebrugh, L. E., Sproules, S., Boyd, W. C., Bergman, R. G., DeBeer, S., Toste, F. D., and Wieghardt, K.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of the American Chemical Society
Publisher:American Chemical Society
ISSN:0002-7863
ISSN (Online):1520-5126

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