Zenno Hikaru, Kobayashi Fumiya, Nakamura Masaaki, Sekine Yoshihiro, Lindoy Leonard F, Hayami Shinya
Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
Department of Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
Dalton Trans. 2021 Jun 8;50(22):7843-7853. doi: 10.1039/d1dt01069g.
The magnetic properties and structural aspects of the 1-D cobalt(ii) complexes, [Co(pyterpy)Cl2]·2H2O (1·2H2O; pyterpy = 4'-(4'''-pyridyl)-2,2':6',2''-terpyridine) and [Co(pyethyterpy)Cl2]·2H2O (2·2H2O; pyethyterpy = 4'-((4'''-pyridyl)ethynyl)-2,2':6',2''-terpyridine) are reported. In each complex the central cobalt(ii) ion displays an octahedral coordination environment composed of three nitrogen donors from the terpyridine moiety, a nitrogen donor from a pyridyl group and two chloride ligands which occupy the axial sites. 1·2H2O exhibits abrupt spin-crossover (SCO) behaviour (T1/2↓ = 218 K; T1/2↑ = 227 K) along with a thermal hysteresis loop, while 2·2H2O and the dehydrated species 1 and 2 exhibit high-spin (HS) states at 2-300 K as well as field-induced single-molecule magnet (SMM) behaviour attributed to the presence of magnetic anisotropic HS cobalt(ii) species (S = 3/2). 1·2H2O exhibited reversible desorption/resorption of its two water molecules, revealing reversible switching between SCO and SMM behaviour triggered by the dehydration/rehydration processes. Single crystal X-ray structural analyses revealed that 1·2H2O crystalizes in the orthorhombic space group Pcca while 2 and 2·2H2O crystallize in the monoclinic space group P2/n. Each of the 1-D chains formed by 1·2H2O in the solid state are bridged by hydrogen bonds between water molecules and chloride groups to form a 2-D layered structure. The water molecules bridging 1-D chains in 1·2H2O interact with the chloride ligands occupying the axial positions, complementing the effect of Jahn-Teller distortion and contributing to the abrupt SCO behaviour and associated stabilization of the LS state.
报道了一维钴（II）配合物[Co(pyterpy)Cl₂]·2H₂O（1·2H₂O；pyterpy = 4'-(4'''-吡啶基)-2,2':6',2''-三联吡啶）和[Co(pyethyterpy)Cl₂]·2H₂O（2·2H₂O；pyethyterpy = 4'-((4'''-吡啶基)乙炔基)-2,2':6',2''-三联吡啶）的磁性和结构方面。在每个配合物中，中心钴（II）离子呈现八面体配位环境，由三联吡啶部分的三个氮供体、一个吡啶基的氮供体以及占据轴向位置的两个氯配体组成。1·2H₂O表现出突然的自旋交叉（SCO）行为（T₁/₂↓ = 218 K；T₁/₂↑ = 227 K）以及热滞回环，而2·2H₂O和脱水产物1和2在2 - 300 K表现出高自旋（HS）态以及归因于磁性各向异性HS钴（II）物种（S = 3/2）存在的场诱导单分子磁体（SMM）行为。1·2H₂O表现出其两个水分子的可逆解吸/再吸附，揭示了由脱水/再水化过程触发的SCO和SMM行为之间的可逆切换。单晶X射线结构分析表明，1·2H₂O结晶于正交空间群Pcca，而2和2·2H₂O结晶于单斜空间群P2/n。固态下由1·2H₂O形成的每条一维链通过水分子和氯基团之间的氢键桥连形成二维层状结构。1·2H₂O中桥连一维链的水分子与占据轴向位置的氯配体相互作用，补充了 Jahn - Teller 畸变的影响，并有助于突然的SCO行为以及低自旋（LS）态的相关稳定性。
