Density Functional Theory Calculations of the Electron Paramagnetic Resonance Parameters for VO²⁺ Complexes

Abstract

Density functional theory calculations of electron paramagnetic resonance (EPR) parameters, such as electronic g tensors and metal hyperfine interaction (A) tensors, have been completed for a series of VO2+ complexes. g tensors were calculated with the zeroth-order regular approximation (ZORA) for relativistic effects as incorporated into the Amsterdam Density Functional (ADF) program. The A tensors were calculated by relativistic and nonrelativistic methods as implemented in ADF and Gaussian98 programs, respectively. The best overall agreement with experimental A values was obtained with the nonrelativistic method and the half-and-half hybrid functionals, such as BHPW91, BHP86, and BHLYP. The isotropic A values (A iso) calculated nonrelativistically with the BHPW91 functional deviated by about 10% from the experimental A iso values. The A iso values calculated with the relativistic effects and pure generalized gradient correction (GGA) functionals, such as BP86, deviated systematically by approximately 40% compared to the experimental A iso values. The difference in performance of the two methods for these complexes is attributed to the improved performance of hybrid functionals for treating core shell spin polarization. The calculation of the anisotropic or dipolar hyperfine interactions, A D, was less sensitive to the choice of functional, and therefore, the relativistic and nonrelativistic calculations of A D exhibited comparable accuracy.

Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

“…With DFT methods it is possible to calculate EPR parameters of transition metal complexes [22,64], and more particularly of a VO 2? species [44][45][46][47][48]. In particular, it has recently been demonstrated that it is possible to predict A z for a VO 2?…”

“…As recently pointed out, the better performance of BHandHLYP than the other functionals is related to the prediction of the Fermi contact term, which depends on the indirect core level spin polarization arising from the unpaired spin density in the metal d orbitals. The spin polarization is difficult to simulate with high accuracy, and most of the functionals underestimate it significantly [45,68]. The higher fraction of Hartree-Fock exchange in half-and-half functionals such as BHandHLYP, which is available in Gaussian 03, improves considerably the prediction of the Fermi contact and, thus, of A z (see ''DFT calculations'').…”

“…As demonstrated in the literature, DFT simulations are a valid tool for predicting EPR parameters of VO 2? complexes [44][45][46]. Using the half-and-half hybrid BHandHLYP functional and the 6-311g(d,p) basis set, one can calculate the 51 V hyperfine coupling constant along the z-axis (A z ) with a mean deviation from the experimental value lower than 3 % [47,48].…”

An experimental and theoretical study of the Cp2VO2CO: use of 13CO32− for structure investigation of d1‐metallocene complexes

“…Recently this method was used successfully for HFC tensor calculations of some vanadocene(IV) 12 and vanadyl(IV) complexes. 13,14 Calculations of HFC tensor and geometry optimizations were performed at the electron unrestricted DFT level using B3PW91 functional 23,24 with DZ basis set 25 for vanadium and pVDZ basis sets 25 for the main group atoms, according to our previous study. 12 The carbon S-HFC tensors of compounds 2 and 3 were calculated with DZ basis set for carbon of carbonate ligand and vanadium and pVDZ for the other atoms.…”

Preface: Recent Advances and Highlights of the 5th International Vanadium Symposium

“…Several reviews have been published on vanadium coordination chemistry, but here we emphasize those in Comprehensive Coordination Chemistry I, 1987 Since 2003 fundamental coordination chemistry continued to be developed in several fronts and theoretical studies have also improved significantly the last few years to model the structure of vanadium compounds, as well as to calculate relevant spectroscopic parameters, namely, for EPR (166,167) and NMR spectroscopies (168)(169)(170). In Chapter 22 Buhl discusses the application of DFT and QM/MM studies to models of peroxidases; already in Chapter 13 Plass and coworkers have applied DFT methods to investigate the structure of the resting state of the prosthetic group in the enzyme pocket and to elucidate the mechanism of the formation of its peroxo complex.…”