Saied M. E. Khalil

Structural diversity in copper(II) complexes of bis(thiosemicarbazone) and bis(semicarbazone) ligands

Two symmetrical bis(carbazone) ligands, H4L1 and H4L2, were prepared by condensation of 4,6-diacetylresorcinol with thiosemicarbazide and semicarbazide, respectively. Their structures were elucidated by elemental analyses and IR, electronic and 1H NMR spectroscopy. Both ligands are tetrabasic and contain two sets of SNO (H4L1) or ONO (H4L2) coordinating sites. Binuclear, trinuclear and dimeric CuII complexes and also adducts with organic bases were prepared. Reactions of H4L1 with several CuII salts, including Cl−, AcO−, , and , in addition to CuI as CuI, afforded different binuclear complexes depending on the salt and the working conditions, except for CuCl2, where a trinuclear complex with a unique mode of bonding was obtained. These complexes reflect the strong coordinating power of Cl−, and AcO− compared to . The mode of bonding and the basicity of the H4L1 ligand are also influenced by the counteranion, the pH of the reaction medium, the working conditions and the oxidation state of copper. The reactivity of the binuclear CuII complexes of both H4L1 and H4L2 towards 1,10-phenanthroline (Phen), 2,2′-bipyridyl (Bpy), N,N,N′,N′-tetramethylethylenediamine (Tmen) and 8-hydroxyquinoline (Oxine; Ox) were investigated. Adducts with organic bases were obtained in the mole ratio 2 : 1 : 1 for H4L1 and 2 : 1 : 2 for H4L2 [CuII : ligand : base (base = Phen, Bpy or Ox)], which reflects the difference in size of S and O. With Tmen, dimeric complexes were obtained containing no Tmen molecules instead of the expected adducts for both H4L1 and H4L2. Evidently the presence of Tmen in the reaction mixture enhances the dimerization process. Characterization and structure elucidation of the complexes was achieved by elemental and thermal analyses, electronic, IR, mass and ESR spectroscopy, as well as conductance and magnetic susceptibility measurements. Finally, the antifungal and antibacterial activities of H4L1 and its metal complexes were investigated.

INTERMEDIATES IN THE THERMAL DECOMPOSITION OF NORMAL COPPER(II), NICKEL(II) AND COBALT(II) SELENITE DIHYDRATES

Abstract Thermal decomposition of normal transition metal selenite dihydrates, MSeO2.2H2O; M [dbnd] Cu(II), Ni(II), Co(II) was traced by TGA/DTA measurements from 50–700°C. The thermal products were obtained by heating the selenites in an air-oven to different temperatures, as determined from TGA/DTA curves, where different coloured products are obtained. The structures of the start selenites and the thermal intermediates were determined by chemical analyses and FT-IR spectral measurements. The start selenites proved to be equilibrium mixtures of the selenite, hydrogenselenite and/or pyroselenite anions. Gradual changes occurred in the FT-IR spectra of the nickel and cobalt selenites on thermal treatment till 225°C where, due to water loss, merely selenite anions are observed. In the case of the copper selenite, the selenito mixture persists till 250°C and the only change observed in the final product is the disappearance of one of the structurally non-equivalent water molecules present in the start selen...

Synthesis, Spectroscopic and Magnetic Studies on Metal Complexes of 5-Methyl-3-(2-Hydroxyphenyl)Pyrazole

A tridentate ONN donor ligand, 5-methyl-3-(2-hydroxyphenyl)pyrazole; H2L, was synthesized by reaction of 2-(3-ketobutanoyl)phenol with hydrazine hydrate. The ligand was characterized by IR, 1H NMR and mass spectra. 1H NMR spectra indicated the presence of the phenolic OH group and the imine NH group of the heterocyclic moiety. Different types of mononuclear metal complexes of the following formulae [(HL)2M]⋅xH2O (M=VO, Co, Ni, Cu, Zn and Cd), [(HL)2M(H2O)2] (M=Mn and UO2) and [(HL)LFe(H2O)2] were obtained. The Fe(III) complex, [(HL)LFe(H2O)2] undergoes solvatochromism. Elemental analyses, IR, electronic and ESR spectra as well as thermal, conductivity and magnetic susceptibility measurements were used to elucidate the structures of the newly prepared metal complexes. A square-pyramidal geometry is suggested for the VO(IV) complex, square-planar for the Cu(II), Co(II) and Ni(II) complexes, octahedral for the Fe(III) and Mn(II) complexes and tetrahedral for the Zn(II) and Cd(II) complexes, while the UO2(VI) complex is eight-coordinate. Transmetallation of the UO2(VI) ion in its mononuclear complex by Fe(III), Ni(II) or Cu(II) ions occurred and mononuclear Fe(III), Ni(II) and Cu(II) complexes were obtained. IR spectra of the products did not have the characteristic UO2 absorption band and the electronic spectra showed absorption bands similar to those obtained for the corresponding mononuclear complexes. Also, transmetallation of the Ni(II) ion in its mononuclear complex by Fe(III) has occurred. The antifungal activity of the ligand and the mononuclear complexes were investigated.

Copper(II), Nickel(II), Oxovanadium(IV) and Dioxouranium(VI) Complexes of Novel Asymmetric Tetradentate Schiff Base Ligands Derived from 6-Methyl-3-Formyl-4-Hydroxy-2-(1H)-Quinolone. Part V

Abstract The novel, half-unit ligand obtained by the single condensation of 6-methyl-3-formyl-4-hydroxy-2-(1H)-quinolone and p-phenylenediamine, was condensed with either acetylacetone or salicylaldehyde to yield novel, asymmetric tetradentate Schiff base ligands, H2La and H2Lb, respectively. The reactions of the ligands with Cu2+, Ni2+, VO2+ and UO2 2+ salts yielded complexes of the general formula [L2M2 nH2O, except that of the uranyl complex of the ligand H2La which has the formula [LaUO2)2(OAc)2(OH2)2]. The ligands and metal complexes were characterized by elemental analyses, IR, UV-visible, mass and ESR spectra and magnetic measurements. The Cu2+ complexes are distored tetrahedral, the Ni2+ complexes are octahedral, the VO2+ complexes are square pyramidal and the UOz z+ complexes are pentagonal bipyramidal The vanadyl and nickel complexes showed antiferromagnetic interaction between adjacent metal cations.

Synthesis, Spectral and Magnetic Studies of Mononuclear and Binuclear Mn(Ii), Co(Ii), Ni(Ii) and Cu(Ii) Complexes with Semicarbazone Ligands Derived from Sulfonamide

Mononuclear and binuclear Mn(II), Co(II), Ni(II) and Cu(II) complexes of new semicarbazone ligands derived from sulfonamide were synthesized and characterized by elemental analysis and IR spectra. In mononuclear complexes, the semicarbazone behaves as a monoanionic terdentate or neutral terdentate ligand towards the metal ion. However, in binuclear complexes, it behaves as a monoanionic terdentate towards one of the bivalent metal ions and monoanionic bidentate ligand towards the other metal ion in the same complex. Electronic spectra and magnetic susceptibility measurements of the solid complexes indicated octahedral geometry around Mn(II), Co(II) and Ni(II) and square planar around the Cu(II) ion. These geometries were confirmed by the results obtained from thermal analyses. The antifungus properties of the ligands and their complexes were investigated.

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.

ESR AND SPECTROSCOPI STUDIES OF METAL COMPLEXES OF NOVEL SCHIFF BASES DERIVED FROM 6-METHYL-3-FORMYL-4-HYDROXY-2-(lH) QUINOLONE AND 1, 3-DIAMINOPROPANE OR N-(2-AMINOETHYL)-l, 3-PROPANEDIAMINE, PART VI

Abstract 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...

Mono, bi- and trinuclear metal complexes derived from new benzene-1,4-bis(3-pyridin-2-ylurea) ligand. Spectral, magnetic, thermal and 3D molecular modeling studies

New bis (pyridylurea) ligand, H2L, was synthesized by the reaction of ethylpyridine-2-carbamate (EPC) and p-phenylenediamine. The ligand was characterized by elemental analysis, IR, (1)H NMR, electronic and mass spectra. Reaction of the prepared ligand with Co(2+), Ni(2+), Cu(2+), Fe(3+), VO(2+) and UO2(2+) ions afforded mono, bi- and trinuclear metal complexes. Also, new mixed ligand complexes of the ligand H2L and 8-hydroxyquinoline (8-HQ) with Co(2+), Ni(2+), Cu(2+) and Fe(3+) ions were synthesized. The ligand behaves as bi- and tetradentate toward the transition metal ions, coordination via the pyridine N, the carbonyl O and/or the amidic N atoms in a non, mono- and bis-deprotonated form. The complexes were characterized by elemental and thermal analyses, IR, electronic and mass spectra as well as conductance and magnetic susceptibility measurements. The results showed that the metal complexes exhibited different geometrical arrangements such as square planar, tetrahedral, octahedral and square pyramidal arrangements. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. 3D molecular modeling of the ligand, H2L and a representative complex were studied.

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

Abstract 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.

A Novel Type Half-Unit Schiff Base Ligand, 3-[o-Aminophenyliminomethyl]-4-Hydroxy-6-Methyl-2-(1H)-Quinolone and its Metal Complexes. Part IVa

Abstract A novel half-unit Schiff base ligand derived from 6-methyl-3-formyl-4-hydroxy-2-(1H)-quinolone and o-phenylenediamine was prepared. The Schiff base acts as a monobasic ligand. Metal complexes of the type [MLX]2, M = Cu(II), Ni(II) or Fe(III); X = Cl or OAc were obtained by the reaction of metal acetates or chlorides with the ligand, with the ligand behaving as a terdentate. However, the reaction of M(ClO4)2.6H2O, M = Cu(II) or Ni(II), VOSO4 and UO2(OAc)2.2H2O with the ligand, yielded complexes of the type [ML2], where the ligand behaves as a bidentate. The ligand and its metal complexes were characterized by elemental analyses, UV-visible, IR and mass spectra. Also, magnetic susceptibilities of the metal complexes were determined. Referee I: K. J. Takeuchi Referee II: R. F. Wilson a Part III: Ref. [1].