First-principle computation of zero-field splittings: Application to a high valent Fe(IV)-oxo model of nonheme iron proteins

Abstract

We report the computational implementation of a combined spin-density-functional theory and perturbation theory ͑SDFT-PT͒ methodology for the accurate calculation of zero-field splittings ͑ZFS͒ in complexes of the most diverse nature including metal centers in proteins. We have applied the SDFT-PT methodology to study the cation of the recently synthesized complex ͓Fe IV ͑O͒-͑TMC͒͑NCCH 3 ͔͒͑OTf͒ 2 , ͓J. Rohde et al., Science 299, 1037 ͑2003͔͒ which is an important structural and functional analog of high-valent intermediates in catalytic cycles of nonheme iron enzymes. The calculated value ͑D Theory = 28.67 cm −1 ͒ is in excellent agreement with the unusually large ZFS reported by experiment ͑D Exp =29±3 cm −1 ͒. The principal component D zz of the ZFS tensor is oriented along the Fe IV = oxo bond indicating that the oxo ligand dominates the electronic structure of the complex.

Zero-field splitting in nickel(II) complexes: A comparison of DFT and multi-configurational wavefunction calculations

“…15,16 The development of the theoretical tools to calculate the ZFS parameters by quantum chemistry technique over the last decade has been quite impressive, with Frank Neese and his group as the leading team, 10,11,[17][18][19][20][21][22][23][24][25][26][27][28][29][30] but also with important contributions from other authors. [31][32][33][34][35][36][37] The development has followed two routes, making use of either efficient density functional theory (DFT) techniques or of high-end wavefunction methods based on multi-configurational SCF techniques (such as complete active space self-consistent field (CASSCF) and related extensions). Many of these options are provided in the ORCA program package.…”

Theoretical determination of spin Hamiltonians with isotropic and anisotropic magnetic interactions in transition metal and lanthanide complexes

“…123 First a spin unrestricted calculation of a given spin configuration is performed, followed by a perturbative treatment of the spin-orbit coupling to obtain a second-rank symmetric ZFS tensor. Similar approaches appeared over the years, for instance by Aquino and Rodriguez 124 and by Neese. 96 These approaches were recently reviewed by van Wu ¨llen and coworkers, 125,126 clarifying the discrepancy between the prefactors associated with the spin-flip approaches of Pederson and Neese.…”

On the Control of Magnetic Anisotropy through an External Electric Field

“…This methodology, under unrestricted Kohn–Sham formalism, as adopted herein, is being widely used to compute ZFS parameters 22a. 25 Although there are several methods available for the computation of the ZFS parameter, the Pederson and Khanna (PK) method is known to produce the correct sign of the ZFS parameter;22a, 26 therefore, we use this methodology20 to calculate the ZFS parameters. The ZFS contributions predicted by this method show fair agreement with accurate ab initio and experimental results.…”