ESR and spectroscopic studies of metal complexes of novel Schiff bases derived from 6-methyl-3-formyl-4-hydroxy-2-(1H) quinolone and 1,3-diaminopropane or N-(2-aminoethyl)-1,3-propanediamine, part VI

Two novel dianionic tetradentate (N2O2) and pentadentate (N3O2) Schiff base ligands and their corresponding Cu(II), Ni(II), Co(II), Mn(II), VO(IV), Fe(III), UO2(VI), Th(IV), Zn(II) and Cd(II) complexes were prepared and characterized by elemental analyses, IR, visible and ESR spectra, magnetic susceptibility measurements as well as mass spectroscopy. Mononuclear and or dinuclear metal complexes were obtained. The Cu(II) complexes have either square-planar or octahedral geometries. The mononuclear Ni(II) complex show anomalous behavior where both square-planar and octahedral geometries coexist, while its dinuclear complex has an octahedral geometry. Co(II) complexes were either mononuclear or dinuclear and showed five-coordinate trigonal bipyramidal and/or octahedral geometry. These structural geometries were confirmed by the results obtained from the thermal analyses. VO(IV) complexes were octahedral and polymeric. The mononuclear Mn(II) complex of the tetradentate Ligand and the dinuclear Fe(III) complex of the pentadentate ligand were the only compounds obtained and showed octahedral geometry. The UO2(VI) and Cd(II) cations behaved similarly and coordinated to two tetradentate ligand molecules through their outer O-O coordinating sites, while they coordinated to only one molecule of the pentadentate ligand, through their N3O2 or N2O2 sites, respectively. This reflects the effect of the cavity size of both ligands towards accommodating large cations. Th(IV) cations were coordinated to two bidentate nitrate anions, thus aiding the ligands to accommodate large cations in their cavities and raising their coordination sphere to either eight or nine. Small Zn(II) cations are well accommodated in the cavities of both ligands.