A perspective on applications of ligand-field analysis: inspiration from electron paramagnetic resonance spectroscopy of coordination complexes of transition metal ions

Abstract

Este artigo descreve de maneira um tanto pessoal, o uso da espectroscopia de ressonância paramagnética eletrônica (EPR), incluindo EPR de alta freqüência e alto campo (HFEPR) para investigar a estrutura eletrônica de complexos de íons de metal de transição. Os parâmetros Hamiltonianos de spin, obtidos a partir de experimentos EPR, matriz g para sistemas com S =1/2 e matrizes g e D (zero-field splitting) para sistemas com S > 1/2 fornecem informações sobre os níveis de energia dos orbitais d. Esta informação pode ser combinada com a teoria do campo ligante (TCL) para fornecer informações a respeito da estrutura eletrônica global de complexos paramagnéticos de metal de transição. Como tem sido discutido por outros autores a TCL ainda se mostra útil para o entendimento quantitativo destes complexos, mesmo com a atual disponibilidade de métodos computacionais avançados, como a teoria do funcional de densidade (DFT). A discussão é ilustrada por exemplos ao longo da série de transição, com configurações d n . This paper describes in a somewhat personal way an overview of the use of electron paramagnetic resonance (EPR) spectroscopy, including high-frequency and -field EPR (HFEPR) to unravel the electronic structure of transition metal ion complexes. The spin Hamiltonian parameters obtained from EPR experiments, namely the g matrix for systems with S =1/2 and the g and D (zero-field splitting) matrices for systems with S > 1/2 provide information on d orbital energy levels. This information can be combined with ligand-field theory (LFT) to provide information on the overall electronic structure of the paramagnetic transition metal complex. As has been discussed by others, LFT is still useful in providing such a quantitative understanding of these complexes, even in the day of advanced computational methods, such as density functional theory (DFT). The discussion is illustrated by examples across the d n configuration.

Magnetostructural relations from a combined ab initio and ligand field analysis for the nonintuitive zero-field splitting in Mn(III) complexes

“…30 Since fourth-order interactions may also be present in monometallic complexes, the method can also be used here to evaluate them. Hence, the theoretical tools are available to revisit the ligand field treatment of ZFS, as noticed by Telser in a recent review, 31 and this work aims to analyze and better understand theoretical and experimental results.…”

The Origin of Magnetic Anisotropy and Single-Molecule Magnet Behavior in Chromium(II)-Based Extended Metal Atom Chains

“…All these considerations are in agreement with the results obtained in AOM section and with previous work on other isoelectronic systems. 75 − 79 , 89 …”

Emission properties of Eu2+, Mn2+ in MAl2Si2O8 (M=Sr, Ba)

“…It was doubted whether Mn 2+ in M-SAS stayed at high-spin state, because such large g value was reported elsewhere [18] for the low-spin d 5 transition metal ion of Fe 3+ . To confirm the spin state of Mn 2+ in both M-SAS and H-BAS, the magnetic measurements were conducted for Mn 2+ singly doped both hosts, which are illustrated in Fig.…”

“…In some cases, the contribution of the orbital magnetic moments is mixed into the g value, which is related to the energy gap between the ground state and the lowest excitation state. The narrower the gap is, the more orbital magnetic moment is contributed, which results in larger g value [18,19]. The Mn 2+ site in M-SAS experiences stronger crystal field than that in H-BAS.…”

“…The deviation of g value from g e due to the contribution of the orbital magnetic moment can also be understood by the following equation [18,19]:…”