CHROMOTROPIC CHANGES OF Cu(II) AND Ni(II) COMPLEXES WITH N2O2 AND N3O2 SCHIFF-BASE LIGANDS IN THE SOLID PHASE

Four new Schiff-base ligands have been prepared from the condensation of 3-formyl-4-hy-droxy-1,8-naphthyridin-2-one with different diamines and a triamine, H2La-H2Ld. Two series of Ni(II) and Cu(II) complexes with the four ligands were also prepared. The ligands and their metal complexes were characterized by chemical analyses, IR, Far-IR, electronic, ESR and mass spectra as well as magnetic measurements and X-ray diffraction patterns. Different products for Ni(II) and Cu(II) were obtained in similar reactions with the same metal salt, depending on the nature of the ligand. Different geometries were also obtained depending on the counter anion of metal salt. Thus, violet square-planar Cu(II) complexes were obtained with Cu(OAc)2. H2O and green octahedral ones with CuCl2. 2H2O, except the reaction with ligand H2Ld which gave only an octahedral product whether the anion was acetate, chloride or perchlorate. Electronic and ESR spectra were used to differentiate between the two geometries of the Cu(II) complexes. The green octahedral Cu(II) complexes undergo irreversible thermochromism to the violet square-planar complexes except the copper complex of the ligand H2Ld which did not not show any color change and retained its octahedral geometry. Based on the magnetic moments and thermal analyses, only one Ni(II) complex of the Schiffbase ligand H2Lc undergoes reversible thermochromism from green (octahedral) to red (squareplanar). The reverse change of the thermal product (red) to the parent complex (green) proceeded on exposure to atmospheric air for a few minutes. On the other hand, Ni(II) complexes of ligands H2La and H2Lb have stable square-planar geometry and all efforts to add other ligands such as H2O or pyridine to these complexes failed to yield other products. The corresponding Cu(II) complexes were easily transformed to their octahedral geometry by adding H2O or pyridine and heating.