Synthesis, crystal structure and spectrothermal characterization of zinc(II) salicylato complex with 2,2′-azobispyridine, [Zn(Hsal)2(H2O)(abpy)]·H2O

The novel aqua(azobispyridine)bis(salicylato)zinc(II) monohydrate complex (1) was synthesized and characterized by means of elemental analysis, IR and UV-vis spectroscopy, thermal analysis and X-ray diffraction techniques. The crystal structure analysis indicates that the mononuclear 1 shows an s-cis/E/s-cis configured azobispyridine ligand, with the distortion from square pyramidal toward trigonal bipyramidal Zn(II) ion coordinated to one pyridyl and one azo N atom together with two carboxylate oxygen atoms and one aqua ligand. The crystal packing involves both hydrogen-bonding and π–π interactions. The title complex undergoes a thermochromic phase transition at ca. 189 °C, changing from 1 (brown complex) to 2 (purple complex) and the thermal decomposition of 1 proceeds in four stages.