10.1021/ja206042k.s002
Neil C. Tomson
Neil C.
Tomson
Mark R. Crimmin
Mark R.
Crimmin
Taras Petrenko
Taras
Petrenko
Lauren E. Rosebrugh
Lauren E.
Rosebrugh
Stephen Sproules
Stephen
Sproules
W. Christopher Boyd
W. Christopher
Boyd
Robert G. Bergman
Robert G.
Bergman
Serena DeBeer
Serena
DeBeer
F. Dean Toste
F. Dean
Toste
Karl Wieghardt
Karl
Wieghardt
A Step beyond the Feltham–Enemark Notation: Spectroscopic and Correlated <i>ab Initio</i> Computational Support for an Antiferromagnetically Coupled M(II)–(NO)<sup>−</sup> Description of Tp*M(NO) (M = Co, Ni)
American Chemical Society
2016
0 formulation
EPR
Cu analogues
SNO
CASSCF
Correlated ab Initio Computational Support
Ni complexes contrasts
ab initio multireference methods
DFT
Tp
diamagnetic Ni analogue
ab initio
metal center
2016-02-22 13:40:23
Journal contribution
https://acs.figshare.com/articles/journal_contribution/A_Step_beyond_the_Feltham_Enemark_Notation_Spectroscopic_and_Correlated_i_ab_Initio_i_Computational_Support_for_an_Antiferromagnetically_Coupled_M_II_NO_sup_sup_Description_of_Tp_M_NO_M_Co_Ni_/2580547
Multiple spectroscopic and computational methods were used to characterize the ground-state electronic structure of the novel {CoNO}<sup>9</sup> species Tp*Co(NO) (Tp* = hydro-tris(3,5-Me<sub>2</sub>-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) (<i>S</i><sub>Co</sub> = <sup>3</sup>/<sub>2</sub>) metal center, antiferromagnetically coupled to a triplet NO<sup>–</sup> anion (<i>S</i><sub>NO</sub> = 1), an interpretation of the electronic structure that was validated by <i>ab initio</i> multireference methods (CASSCF/MRCI). Electron paramagnetic resonance (EPR) spectroscopy revealed significant <i>g</i>-anisotropy in the <i>S</i> = <sup>1</sup>/<sub>2</sub> ground state, but the linear-response DFT performed poorly at calculating the <i>g</i>-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 <i>g</i>-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) (<i>S</i><sub>Ni</sub> = 1) metal center antiferromagnetically coupled to an <i>S</i><sub>NO</sub> = 1 NO<sup>–</sup>. The similarity between the Co and Ni complexes contrasts with the previously studied Cu analogues, for which a Cu(I) bound to NO<sup>0</sup> formulation has been described. This discrepancy will be discussed along with a comparison of the DFT and <i>ab initio</i> computational methods for their ability to predict various spectroscopic and molecular features.