Bipyridyl Second Ligand Dependent Structural and Magnetic Properties of Cu(II) Complexes with Pyridine-2,6-dicarboxylate and Water Molecule as First Ligand

Three new mononuclear complexes [Cu(pdc)L(H2O)]·xH2O (L = 2,4′-bpy, x = 4 (1); L = 5-ph-2,4′-bpy, x = 2 (2); L = 5-Cl-2,4′-bpy, x = 0 (3)) were prepared in the reaction of pyridine-2,6-dicarboxylic acid (H2pdc) with divalent copper ions under hydrothermal conditions in the presence of three second bipyridyl ligands, respectively. The divalent copper ions adopted N2O3 five coordination with pyridine-2,6-dicarboxylate (pdc2−), one water, and 2,4′-bipyridine (2,4′-bpy) or its derivative such as 5-phenyl-2,4′-bipyridine (5-ph-2,4′-bpy) or 5-chloro-2,4′-bipyridine (5-Cl-2,4′-bpy), where lattice water clusters possessing different configuration are formed for 1 and 2. In 1, (H2O)8 molecules adopting a chairlike conformation stack along the a-axis to form a water tape. Hexameric water cluster self-assembles forming a highly ordered comblike infinite chain in 2. Unlike 1 and 2, no lattice water molecule was found in 3, except one coordination water molecule as found in 1 and 2. It was found that the antiferromagnetic interactions between the CuII ions can be tuned by the number of lattice water molecules for these three complexes.