Nickel Cobalt(II) Complexes Complexes Coordination Behaviour Copper(II) Complexes Dibasic Heterocyclic Heterocyclic Amines IR spectra Infrared spectra Ir spectra Ligand Metal ion Mixed Ligand Complexes Physicochemical Polymers Schiff's Base Derived Synthesis Tridentate antituberculous interaction ligand metal chelates model