Bimetallic M^V₂Cu^II₃ (M = Mo, W) Coordination Complexes Based on Octacyanometalates: Structures and Magnetic Variations Tuned by Chelated Tetradentate Macrocyclic Ligands

Four octacyanometalate-based bimetallic Cu−M (M = Mo, W) assemblies coordinated by tetradentate macrocyclic ligands were prepared via self-assembly process in a stoichiometric ratio of [M(CN)8]3- and Cu(macrocycle)2+ and characterized in terms of structures and magnetic properties. The crystal structures are varied depending on the macrocycles used. The employment of cyclam with no pendant groups produced a one-dimensional chain (1) with a rope-ladder pattern, whereas macrocycles with side groups allowed for the formation of two-dimensional honeycomb-like architectures (2−4). From the crystal structures, the variations in apical Cu−Nax lengths and Cu−Nax−Cax angles on the bridging pathways are observed, which arises from the existence of side groups on macrocyclic ligands. The magnetic results reveal that all of the prepared compounds show ferromagnetic couplings between magnetic centers transimitted through CN bridges under the present structural parameters. Comparing the magnetic strength of the Cu−Mo (3d−4d; 2) and Cu−W (3d−5d; 3) complexes supports that 3d−5d magnetic coupling is stronger than 3d−4d because the 5d orbital is more diffuse than 4d. The magnetic analyses for 1−4 and related complexes tentatively suggest that, when the Cu−Nax distances are long enough, the axial Cu−Nax bond length in the bridging route may be one of the major structural parameters to determine the magnitude of the ferromagnetic exchange coupling.四类由四齿大环配体配位的八氰合金属基双金属Cu−M（M = Mo、W）组装体，通过[M(CN)8]3-与Cu(大环)2+按化学计量比的自组装过程制备，并对其晶体结构与磁学性能进行了系统表征。其晶体结构因所选用的大环配体不同而呈现多样性。采用无侧基的1,4,8,11-四氮杂环十四烷（cyclam）时，得到了绳梯型一维链状结构（1）；而带有侧基的大环配体则可构筑二维类蜂窝状骨架结构（2−4）。通过晶体结构分析发现，桥联路径中的轴向Cu−Nax键长与Cu−Nax−Cax键角存在差异，该差异源于大环配体上侧基的存在。磁学测试结果表明，在所考察的结构参数下，所有制备的化合物均呈现出通过氰桥传递的磁中心间铁磁耦合作用。对比Cu−Mo（3d−4d；2）与Cu−W（3d−5d；3）配合物的磁学强度可知，3d−5d体系的磁耦合作用强于3d−4d体系，这是因为5d轨道比4d轨道更弥散。对1−4及其相关配合物的磁学分析初步表明，当Cu−Nax距离足够长时，桥联路径中的轴向Cu−Nax键长或许是决定铁磁交换耦合强度的主要结构参数之一。