Department of Chemistry, University of California, Berkeley, CA 94720, USA.
Max-Planck-Insitut für Kohlenforschung, Mülheim an der Ruhr D-45470, Germany.
Science. 2018 Dec 21;362(6421). doi: 10.1126/science.aat7319. Epub 2018 Nov 15.
Orbital angular momentum is a prerequisite for magnetic anisotropy, although in transition metal complexes it is typically quenched by the ligand field. By reducing the basicity of the carbon donor atoms in a pair of alkyl ligands, we synthesized a cobalt(II) dialkyl complex, Co(C(SiMeONaph)) (where Me is methyl and Naph is a naphthyl group), wherein the ligand field is sufficiently weak that interelectron repulsion and spin-orbit coupling play a dominant role in determining the electronic ground state. Assignment of a non-Aufbau (d , d )(d , d )(d ) electron configuration is supported by dc magnetic susceptibility data, experimental charge density maps, and ab initio calculations. Variable-field far-infrared spectroscopy and ac magnetic susceptibility measurements further reveal slow magnetic relaxation via a 450-wave number magnetic excited state.
轨道角动量是磁各向异性的前提条件，尽管在过渡金属配合物中，它通常会被配体场猝灭。通过降低一对烷基配体中碳供体原子的碱性，我们合成了一个钴(II)二烷基配合物，Co(C(SiMeONaph))（其中 Me 是甲基，Naph 是萘基），其中配体场足够弱，使得电子间排斥和自旋轨道耦合在确定电子基态中起主导作用。非 Aufbau（d , d ）（d , d ）（d ）电子构型的分配得到了直流磁化率数据、实验电荷密度图和从头算计算的支持。变场远红外光谱和交流磁化率测量进一步揭示了通过 450 波数磁激发态的缓慢磁弛豫。
