Field-Induced Slow Magnetic Relaxation in the Ni(I) Complexes [NiCl(PPh3)2]·C4H8O and [Ni(N(SiMe3)2)(PPh3)2]

Direct current (dc) and alternating current (ac) magnetic measurements have been performed on the three Ni­(I) complexes: [NiCl­(PPh3)3], [NiCl­(PPh3)2]·C4H8O, and [Ni­(N­(SiMe3)2)­(PPh3)2]. Fits of the dc magnetic data suggest an almost similar behavior of the three compounds, which display only moderate deviations from the spin-only values. The ac magnetic investigations reveal that the two complexes with trigonal planar coordination[NiCl­(PPh3)2]·C4H8O and [Ni­(N­(SiMe3)2)­(PPh3)2]display slow magnetic relaxation at low temperatures under applied dc fields, whereas tetrahedral [NiCl­(PPh3)3] does not. Ground and excited states as well as magnetic data were calculated by ab initio wave function based multi-configurational methods, including dynamic correlation as well as spin–orbit coupling. The two trigonal planar complexes comprise well-isolated S = 1/2 ground states, whereas two S = 1/2 states with a splitting of less than 100 cm–1 were found in the tetrahedral compound.已对三种镍(I)配合物开展了直流（direct current, dc）与交流（alternating current, ac）磁学测量，涉及的配合物分别为[NiCl(PPh₃)₃]、[NiCl(PPh₃)₂]·C₄H₈O以及[Ni(N(SiMe₃)₂)(PPh₃)₂]。对直流磁数据的拟合结果表明，三种配合物的磁学行为近乎一致，其磁矩仅与纯自旋磁矩值存在小幅偏差。交流磁学研究显示，两种具有平面三角配位构型的配合物——即[NiCl(PPh₃)₂]·C₄H₈O与[Ni(N(SiMe₃)₂)(PPh₃)₂]——在低温外加直流场条件下呈现慢磁弛豫现象，而四面体构型的[NiCl(PPh₃)₃]则无此现象。研究人员采用基于从头算波函数的多组态方法（包含动态相关与自旋轨道耦合）计算了三种配合物的基态、激发态以及磁学数据。两种平面三角配位配合物拥有孤立的S=1/2基态，而四面体构型的配合物则存在两个能级差小于100 cm⁻¹的S=1/2态。