Synthesis, characterization and molecular structure of a zinc(II) formate-2,2′-bipyridine mono-dimensional coordination polymer. Comparison with other 2,2-bipyridine coordination compounds

Hydrated zinc(II) formate reacts with 2,2'-bipyridine (2,2'-bpy) to form a novel zig-zag mono-dimensional coordination polymer (1D CP) [{Zn(mu-OCHO)(OCHO)(2,2'-bpy)(H2O)}center dot H2O](n), 1, which was structurally characterized by a single-crystal X-ray diffraction study. Title compound crystallizes in the orthorhombic system, Pbca space group, [a = 6.7651(8), b = 17.4876(19), c = 23.180(3)]. Each zinc ion displays a distorted octahedral geometry due to the coordination of a monotopic formate, one molecule of water and the two nitrogen atoms of 2,2'-bpy, while the octahedral scheme is completed by the coordination of a ditopic formate connecting two zinc ions according to a syn-anti configuration, thus generating the polymeric structure. Moreover, a crystallization water molecule acts as a supramolecular bridge connecting formate ions belonging to neighboring, symmetry equivalent, 1D CPs through quite strong H-bonds, thus leading to an overall waved 2D open framework. Thermal analyses show significant weight losses corresponding to the elimination of water molecules followed by the decomposition of both formate groups and 2,2'-bipyridine.