Copper(II) Complexes with cis-Epoxysuccinate Ligand: Syntheses, Crystal Structures, and Magnetic Properties

Three CuII complexes with cis-epoxysuccinate ligand were synthesized and structurally characterized: [Cu(ces)(phen)]2 (1), [Cu(ces)(bpy)]2 (2), and {[Cu2(ces)(pp)2(CH3OH)]}∞ (3), (ces = cis-epoxysuccinate, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine, and pp = 3-(2-pyridyl)pyrazole with pyrazolyl N-donor deprotonated). Structural analysis reveals that both 1 and 2 have the very similar dinuclear units that are extended by the intermolecular supramolecular interactions, such as C–H⋯O, C–H⋯π, and aromatic π⋯π stacking interactions, to give rise to the higher-dimensional frameworks. Complex 3 has a two-dimensional (2D) layered structure that is further assembled to form a three-dimensional framework by the inter-layer C–H⋯O hydrogen-bonding and C–H⋯π interactions. A structural comparison with those of our previous work in the absence of auxiliary co-ligand suggests that the introduction of 2,2′-bipyridyl-like molecules plays an important role in constructing the final structures of 1–3. Magnetic measurements demonstrate that 1 and 2 exhibit ferromagnetic coupling with the corresponding J values of 1.8 cm–1 for 1 and 1.5 cm–1 for 2, whereas 3 shows more complicated magnetic coupling.