Synthesis and Characterization of some Unsymmetrical Schiff Base Ligands and their Nickel(II) Complexes Incorporating o‐Phenylenediimine Units

Six new nickel(II) complexes of the unsymmetrical Schiff base ligands derived from o‐phenylenediamine were synthesized. These complexes were prepared by template and non‐template reactions of the precursor 3‐acetyl‐4‐[N‐(2'‐aminophenyl)‐amino]‐3‐buten‐2‐one ( HL °) with appropriate o‐hydroxycarbonyl aromatic compounds, aromatic 1, 3‐oxo aldehydes and 1, 3‐diketones. The nickel(II) compounds were characterized by analytical and spectroscopic methods. Crystal structure of complex [3‐acetyl‐(6, 7)‐benzo‐8‐salicylidene‐5, 8‐diazahepta‐3‐ene‐2‐onato(2‐)]nickel(II) ( NiL ¹) has been determined by X‐ray powder diffraction method, revealed that the molecules are almost flat, and there are no forces other than van der Waals interactions between molecules. The structure was solved by global optimisation technique and refined by the Rietveld method, obtained R_F and R_wp are 11.6 and 17.4%, respectively. The synthesis of a new unsymmetrical nickel(II) tetraazamacrocyclic complex is also described.