The compounds [Zn^II{C₆H₄(NH₂)₂}₂(NO₃)₂], (1) and [Cd^II{C₆H₄(NH₂)₂}₂(NO₃)₂] (2) have been prepared (C₆H₄(NH₂)₂ = orthophenylenediammine = opda) and characterized by routine spectroscopic methods and single crystal X-ray diffraction analysis. Compound 1 crystallizes in orthorhombic space group $Pcab$, where as compound 2 crystallizes in monoclinic space $P2_1/n$. In the crystal structure of 1 an extended hydrogen bonding network is formed involving zinc coordinated amines and nitrato ligands. The compound 2 consists of molecules in which the cadmium ion is eight coordinated, with two bidentate nitrate groups and two bidentate opda ligands. The geometry around the cadmium described as a distorted dodecahedron. The crystal structure of 2 shows an intricate hydrogen bonding network, formed by amine and nitro groups coordinated to cadmium.

The violet-coloured compound [Ni^II(opda)₂(NCS)₂] (1) undergoes colour change to strawyellow colour retaining its molecular composition on standing over long period of time at room temperature in the solid state. Compound 1 (violet form) and its yellow-form [Ni^II(opda)₂(NCS)₂] (2) (opda = orthophenylenediammine) have been characterized by routine spectroscopic methods and single crystal X-ray diffraction analysis. Compound 1 crystallizes in monoclinic space group $P2_1/c$ and its yellow form (compound 2) retains same space group. Their crystal structures show an intricate supramolecular network based on N-H$\cdots$S hydrogen bonds, that involve amine and thiocyanate groups coordinated to nickel(II).