Hoda F. El-Shafiy

Vo(IV), Fe(III), Co(II) and Cd(II) Complexes of Asymmetric Schiff Base Ligands (N2O3). Synthesis and Spectroscopic Studies

Abstract New series of mononuclear VO(IV), Co(II) and Cd(II) complexes of the formula [HLVO(OH2)]·nH2O, [HLCo]·xH2O and [HLCd]·xH2O and binuclear Fc(III) complexes of the formula [LFe2Cl2(H2O)3]Cl·H2O have been synthesized. L stands for one of the five asymmetrical pentadentate (N2O3) Schiff base ligands H3L1-H3L5 prepared by the condensation of acetoacetylphenol and ethylenediamine in the molar ratio 1:1 to prepare a half-unit Schiff base which is further condensed with one of the following aldehydes and ketones: ℴ-hydroxyacetohpenone, salicylaldehyde. naphthaldehyde, benzoylacetone or acetylacctone. These ligands possess two dissimilar coordination sites, an inner, four-coordinating N2O2 donor set and an outer, three-coordinating O2O set. The complexes were characterized by IR. electronic, ESR and mass spectra as well as conductivity and magnetic measurements. The magnetic moments of the VO(IV) complexes at room temperature are higher than expected for a single electron due to orbital contributions. while antiferromagnetic interaction is observed in the binuclear Fe(III) complexes due to interaction between two adjacent Fe(III) ions. The mass spectra of the complexes show base peaks with m/e values corresponding to the molecular weights of the complexes. The coordination numbers for the vanadium and iron ions are six with octahedral geometries and the coordination numbers for the cobalt and cadmium ions are four with tetrahedral geometries.

Preparation and Characterization of Novel Asymmetrical Schiff-Base Ligands Derived from 2-methyl-7-formyl-8-hydroxyquinoline and their Metal Complexes

Two novel asymmetrical Schiff-base ligands, H2L1 and H2L2, were prepared by reacting two half-unit Schiff-base compounds with 2-methyl-7-formyl-8-hydroxyquinoline. The two half-unit Schiff-base compounds were initially prepared by condensing dimedone with either ethylenediamine or p-phenylenediamine, respectively. Both ligands are dibasic and contain two sets of NO coordinating sites. Twelve metal complexes were obtained by reacting both ligands with Cu(II), Ni(II), Co(II), Mn(II), Fe(III), VO(IV) cations. The ligands and their metal complexes were characterized by elemental analysis, IR, UV-Vis, ESR and mass spectra, also magnetic moments of the complexes were determined. Visible spectra of the complexes indicated distorted octahedral geometries around the metal cations. ESR spectra indicated mononuclear and dinuclear structures of the complexes of ligands H2L1 and H2L2, respectively. Magnetic moments of the complexes were rather low compared with those expected for octahedral geometries and indicated polymeric linkage of the metal complex molecules within their crystal lattices. The insolubility of the metal complexes in most organic solvents support the polymeric structures.

METAL COMPLEXES OF NOVEL SYMMETRICAL SCHIFF BASE LIGANDS

Two novel symmetrical Schiff base ligands, H2L1 and H2L2, with tetradentate N2O2 and pentadentate N3O2 coordinating sites were prepared by the reaction of the aldehyde 2-methyl-7-formyl-8-hydroxy-quinoline with 1,3-diaminopropane or diethylenetriamine, respectively, in the molar ratio 2:1. Cu(II), Ni(II), Co(II), Mn(II), Fe(III) and VO(IV) complexes of both ligands were synthesized. The ligands and their metal complexes were characterized by elemental analyses, IR, UV-Vis, ESR, NMR and mass spectra and also by magnetic moment measurements. Both ligands behave as tetradentate ones when coordinating metal cations. The ligand H2L1 has a smaller cavity than the ligand H2L2, thus the former ligand yielded mononuclear products, through chelation of one ligand molecule to a metal cation, while the latter ligand yielded binuclear products, through the coordination of two metal cations to two ligand molecules. Each of the Fe(III) cations was coordinated to three halves of both ligand molecules yielding also a mononuclear product with ligand H2L1 and a binuclear product with ligand H2L2. Either mononuclear or binuclear complex molecules link together forming polymeric chains. The mononuclear and binuclear complex forms were well manifested in the ESR spectra of the vanadyl complexes. The polymeric structures of the metal complexes led to an enhanced decrease of their magnetic moments through antiferromagnetic exchange between neighbouring metal cations.