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ESR analyses of picket fence MnII and 6th ligand coordinated FeIII porphyrins (S = 5/2) and a CoII(hfac) complex (S = 3/2) with sizable ZFS parameters revisited: A full spin Hamiltonian approach and quantum chemical calculations

Abstract

The fictitious spin-1/2 (effective spin-1/2) spin Hamiltonian approach is the putative method to analyze the conventional fine-structure/hyperfine ESR spectra of high spin metallocomplexes with sizable zero-field splitting (ZFS) tensors since early in 1950’s, and the approach gives salient principal geff-values far from g = 2 without explicitly affording their ZFS values in most cases. The experimental geff-values thus determined, however, never agree with those (gtrue-values) of the true principal g-tensors, which are obtainable form reliable quantum chemical calculations. We have recently derived exact or extremely accurate analytical expressions for the geff/gtrue relationships for the spin quantum number S’s up to S = 7/2: T. Yamane, et al., Phys. Chem. Chem. Phys., 2017, 19, 24769–24791. In this work, we have removed the limitation of the collinearity between g- and ZFS tensors and derived the generalized geff/gtrue relationships. To illustrate the usefulness of the present approach, we have revisited important typical high spin systems with large ZFS values such as picket fence metalloporphyrins with MnII (S = 5/2) (Q. Yu, et al., Dalton Trans., 2015, 44, 9382–9390), a 6th ligand coordinated porphyrin with FeIII (S = 5/2) (Y. Ide, et al., Dalton Trans., 2017, 46, 242–249) and a pseudo-octahedral CoII (S = 3/2)(hfac)2 complex (D. V. Korchagin, et al., Dalton Trans., 2017, 46, 7540–7548), completing the ESR spectral and magnetic susceptibility analyses and gaining significant physical insights into their electronic structures. The off-principal axis extra peaks overlooked in the documented spectra of the picket fence MnII porphyrins have fully been assigned, affording to derive their accurate true g-, hyperfine and ZFS tensors, for the first time. For the CoII complex, the occurrence of the non-collinearity between the g- and ZFS tensors has been discussed by using the generalized geff/gtrue relationships. We have attempted to carry out reliable DFT-based and ab initio quantum chemical calculations of their magnetic tensors, in which spin–orbit couplings are incorporated, reproducing the experimental true tensors. We emphasize that the incorporation of multi-reference nature in the electron configuration is important to interpret the magnetic tensors for the CoII complex.

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Supplementary files

Publication details

The article was received on 22 Jul 2018, accepted on 02 Oct 2018 and first published on 05 Oct 2018


Article type: Paper
DOI: 10.1039/C8DT02988A
Citation: Dalton Trans., 2018, Accepted Manuscript
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    ESR analyses of picket fence MnII and 6th ligand coordinated FeIII porphyrins (S = 5/2) and a CoII(hfac) complex (S = 3/2) with sizable ZFS parameters revisited: A full spin Hamiltonian approach and quantum chemical calculations

    T. Yamane, K. Sugisaki, H. Matsuoka, K. Sato, K. Toyota, D. Shiomi and T. Takui, Dalton Trans., 2018, Accepted Manuscript , DOI: 10.1039/C8DT02988A

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