Novotný Jan, Munzarová Markéta, Marek Radek
CEITEC - Central European Institute of Technology, Masaryk University, Kamenice 5, Brno CZ-62500, Czechia.
Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, Brno CZ-62500, Czechia.
Inorg Chem. 2024 May 13;63(19):8580-8592. doi: 10.1021/acs.inorgchem.3c04425. Epub 2024 May 1.
Theoretical interpretation of hyperfine interactions was pioneered in the 1950s-1960s by the seminal works of McConnell, Karplus, and others for organic radicals and by Watson and Freeman for transition-metal (TM) complexes. In this work, we investigate a series of octahedral Ru(III) complexes with aromatic ligands to understand the mechanism of transmission of the spin density from the d-orbital of the metal to the s-orbitals of the ligand atoms. Spin densities and spin populations underlying ligand hyperfine couplings are analyzed in terms of π-conjugative or σ-hyperconjugative delocalization vs spin polarization based on symmetry considerations and restricted open-shell vs unrestricted wave function analysis. The transmission of spin density is shown to be most efficient in the case of symmetry-allowed π-conjugative delocalization, but when the π-conjugation is partially or fully symmetry-forbidden, it can be surpassed by σ-hyperconjugative delocalization. Despite a lower spin population of the ligand in σ-hyperconjugative transmission, the hyperfine couplings can be larger because of the direct involvement of the ligand s-orbitals in this delocalization pathway. We demonstrate a quantitative correlation between the hyperfine couplings of aromatic ligand atoms and the characteristics of the metal-ligand bond modulated by the substituent, a hyperfine .
超精细相互作用的理论解释是在20世纪50年代至60年代由麦康奈尔、卡尔普斯等人关于有机自由基的开创性工作以及沃森和弗里曼关于过渡金属(TM)配合物的工作率先开展的。在这项工作中,我们研究了一系列带有芳香配体的八面体Ru(III)配合物,以了解自旋密度从金属的d轨道传递到配体原子的s轨道的机制。基于对称性考虑以及受限开壳层与非受限波函数分析,根据π共轭或σ超共轭离域与自旋极化来分析配体超精细耦合背后的自旋密度和自旋布居。结果表明,在对称性允许的π共轭离域情况下,自旋密度的传递最为有效,但当π共轭部分或完全被对称性禁阻时,它可能会被σ超共轭离域超越。尽管在σ超共轭传递中配体的自旋布居较低,但由于配体s轨道直接参与了这种离域途径,超精细耦合可能会更大。我们证明了芳香配体原子的超精细耦合与由取代基调制的金属 - 配体键的特性之间的定量相关性,即一种超精细…… (原文此处似乎不完整)