Electron magnetic resonance data on high-spin Mn(III; S=2) ions in porphyrinic and salen complexes modeled by microscopic spin Hamiltonian approach

• Published in: Journal of inorganic biochemistry 2017-10, Vol.175, p.36-46
• Main Authors: Tadyszak, Krzysztof, Rudowicz, Czesław, Ohta, Hitoshi, Sakurai, Takahiro
• Format: Article
• Language: English
• Subjects: Crystal (ligand) field; Electron magnetic resonance (EMR); Electron Spin Resonance Spectroscopy; Ethylenediamines - chemistry; Manganese - chemistry; Microscopic spin Hamiltonian; Mn(III; S = 2) porphyrinic complexes; Mn(III; S = 2) salen analogues; Models, Chemical; Models, Molecular; Organometallic Compounds - chemistry; Porphyrins - chemistry; Semiempirical modeling
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2017.06.006

The spin Hamiltonian (SH) parameters experimentally determined by EMR (EPR) may be corroborated or otherwise using various theoretical modeling approaches. To this end semiempirical modeling is carried out for high-spin (S=2) manganese (III) 3d4 ions in complex of tetraphenylporphyrinato manganese (III) chloride (MnTPPCl). This modeling utilizes the microscopic spin Hamiltonians (MSH) approach developed for the 3d4 and 3d6 ions with spin S=2 at orthorhombic and tetragonal symmetry sites in crystals, which exhibit an orbital singlet ground state. Calculations of the zero-field splitting (ZFS) parameters and the Zeeman electronic (Ze) factors (g||=gz, g⊥=gx=gy) are carried out for wide ranges of values of the microscopic parameters using the MSH/VBA package. This enables to examine the dependence of the theoretically determined ZFS parameters bkq (in the Stevens notation) and the Zeeman factors gi on the spin-orbit (λ), spin-spin (ρ) coupling constant, and the ligand-field energy levels (Δi) within the 5D multiplet. The results are presented in suitable tables and graphs. The values of λ, ρ, and Δi best describing Mn(III) ions in MnTPPCl are determined by matching the theoretical second-rank ZFSP b20(D) parameter and the experimental one. The fourth-rank ZFS parameters (b40, b44) and the ρ (spin-spin)-related contributions, which have been omitted in previous studies, are considered for the first time here and are found important. Semiempirical modeling results are compared with those obtained recently by the density functional theory (DFT) and/or ab initio methods. Theoretical modeling of the dependence of the zero-field splitting parameters bkq (in Stevens notation) and Zeeman factors gi on the spin-orbit, spin-spin coupling constant, and ligand-field energy levels within the 5D multiplet was carried out for high-spin (S=2) manganese (III) 3d4 ions in complex of tetraphenylporphyrinato Mn(III) chloride. [Display omitted] •Electron magnetic resonance data on Mn(III; S=2) ions in porphyrinic complexes modeled.•Spin Hamiltonian (SH) parameters, bkq and gi, calculated using microscopic SH theory.•bkq (gi) dependence on parameters: λ-spin-orbit, ρ-spin-spin, Δi-energy levels studied.•Fourth-rank b4q and spin-spin contributions to bkq, previously omitted, found important.•Results compared with ab initio ones for Mn(III) in porphyrinic and salen complexes.