Sonochemical synthesis and characterization of new seven coordinated zinc, cadmium and mercury nitrate complexes: New precursors for nanostructure metal oxides.

•The nitrate complexes of group 12 elements with a tridentate ligand were synthesized.•X-ray diffraction analysis shows that the central metal is seven-coordinated.•The geometry around metal center is a distorted pentagonal bipyramid.•Hirshfeld surfaces (HS) analysis was used for further investigation of the structure.•The direct thermolysis of zinc and cadmium nitrate complexes led to metal oxide nanoparticles.