Dinuclear copper(II) complexes hold by crab-shaped pincer ligands: Syntheses, structures, luminescent and magnetic properties

Two Cu(II) complexes with N,N′-(2-hydroxy-5-R-1,3-xylylene)bis(N-(carboxymethyl)glycine (R-H5XTA, R = Cl and Br) ligands have been synthesized and their crystal structures have been analyzed by X-ray diffraction methods. The ligands provide a convenient dinucleating feature with the phenolate oxygen providing the bridging function. The complexes consist of dinuclear copper units, hexahydrate copper ion and solvent water molecules. Thereinto, dimer copper ions show two different geometries as Cu1 distorted octahedron and Cu2 square-based pyramid respectively, which has been confirmed by the solid-state electronic absorption spectrum. The thermal decomposition process consists of the loss of corresponding water molecules below 473 K and follow-up decomposition of the main structures. Under the excitation of 360 nm light, luminescence of ligands is quenched by the coordinated Cu(II) ions and heavy Br atom, respectively. Magnetic study shows that coupling of dinuclear copper ions displays ferromagnetic behavior with the J = +9.03 cm−1.