Bonding Features and Magnetic Ordering in Thiolate-Bridged Copper-Nickel Clusters Synthesized at Elevated Temperature.

Atomically-precise heterometallic nickel-based clusters are an emerging class of functional nanomaterials with intriguing optical and magnetic properties. However, synthetic challenges restrict their exploration in comparison to heterometallic coinage metal-based nanoclusters. This study presents a single-step synthesis of the two new thiolate-bridged copper-nickel cluster compounds [CuNiS(MCP)] (1) and [CuNi(MCP)I] (2) (MCPH = 2-mercaptopyridine; MCP = deprotonated 2-mercaptopyridine) at an elevated temperature. Single-crystal X-ray diffraction reveals that 1 is composed of polymeric strands of linked cluster units. Each of the units exhibit a bicapped trigonal prismatic {CuNi} core that is surrounded by three capping sulfide and six MCP ligands. Cluster 2 features individual clusters, each bearing a hexagonal bipyramidal {CuNi} core with twelve MCP units as well as two iodide ions as additional ligands. In spite of the different aggregation modes, both of these clusters exhibit molecule-like characteristic multiband optical absorption features. Temperature-dependent magnetic susceptibility measurements for 1 revealed dual antiferromagnetic and ferromagnetic coupling among six Ni(II) centers with an S = 2 ground state, while 2 exhibits strong ferromagnetic coupling, whereby the susceptibility increases with decreasing temperature to an S = 4 ground state. This study is an example of solvothermal synthesis of related ligand-supported copper-nickel cluster compounds with structure-specific optical and magnetic properties.