Magdy Shebl

Synthesis, spectroscopic characterization and antimicrobial activity of binuclear metal complexes of a new asymmetrical Schiff base ligand: DNA binding affinity of copper(II) complexes

The 1:1 condensation of o-acetoacetylphenol and 1,2-diaminopropane under condition of high dilution gives the mono-condensed Schiff base, (E)-3-(1-aminopropan-2-ylimino)-1-(2-hydroxyphenyl)butan-1-one. The mono-condensed Schiff base has been used for further condensation with isatin to obtain the new asymmetrical dicompartmental Schiff base ligand, (E)-3-(2-((E)-4-(2-hydroxyphenyl)-4-oxobutan-2-ylideneamino) propylimino)indolin-2-one (H3L) with a N2O3 donor set. Reactions of the ligand with metal salts give a series of new binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, (1)H and (13)C NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. The analytical and spectroscopic tools showed that the complexes can be formulated as: [(HL)(VO)2(SO4)(H2O)]·4H2O, [(HL)Fe2Cl4(H2O)3]·EtOH, [(HL)Fe2(ox)Cl2(H2O)3]·2H2O, [(L)M2(OAc)(H2O)m]·nH2O; M=Co, Ni or Cu, m=4, 0 and n=2, 3, [(HL)Cu2Cl]Cl·6H2O and [(L)(UO2)2(OAc)(H2O)3]·6H2O. The metal complexes exhibited octahedral geometrical arrangements except copper complexes that exhibited tetrahedral geometries and uranyl complex in which the metal ion is octa-coordinated. The Schiff base and its metal complexes were evaluated for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus), Gram negative bacteria (Escherichia coli) and fungi (Candida albicans and Aspergillus flavus). The ligand and some of its complexes were found to be biologically active. The DNA-binding properties of the copper complexes (6 and 7) have been investigated by electronic absorption, fluorescence and viscosity measurements. The results obtained indicate that these complexes bind to DNA via an intercalation binding mode with an intrinsic binding constant, Kb of 1.34×10(4) and 2.5×10(4) M(-1), respectively.

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.

Synthesis, spectral and magnetic studies of mono- and bi-nuclear metal complexes of a new bis(tridentate NO2) Schiff base ligand derived from 4,6-diacetylresorcinol and ethanolamine.

A new bis(tridentate NO2) Schiff base ligand, H(4)L, was prepared by the reaction of the bifunctional carbonyl compound; 4,6-diacetylresorcinol (DAR) with ethanolamine. The ligand reacted with iron(III), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), cerium(III) and uranyl(VI) ions, in absence and in presence of LiOH, to yield mono- and bi-nuclear complexes with different coordinating sites. The ligand and its metal complexes were characterized by elemental analyses, IR, (1)H NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. In absence of LiOH, mononuclear complexes (2, 3 and 5-9) as well as binuclear complexes (1 and 4) were obtained. In mononuclear complexes, the ligand acted as a neutral, mono- and di-basic/bi- and tetra-dentate ligand while in binuclear complexes (1 and 4), the ligand acted as a bis(mono- or di-basic/tridentate) ligand. On the other hand, in presence of LiOH, only binuclear complexes (10-15) were obtained in which the ligand acted as a bis(dibasic tridentate) ligand. The metal complexes exhibited different geometrical arrangements such as octahedral, tetrahedral, square planar, square pyramidal and pentagonal bipyramidal arrangements.

Synthesis, spectral studies, and antimicrobial activity of binary and ternary Cu(II), Ni(II), and Fe(III) complexes of new hexadentate Schiff bases derived from 4,6-diacetylresorcinol and amino acids

Two new hexadentate N2O4 donor Schiff bases, H4L1 and H4L2, were synthesized by condensation of 4,6-diacetylresorcinol with glycine and alanine, respectively. The structures of the ligands were elucidated by elemental analyses, IR, 1H NMR, electronic, and mass spectra. Reactions of the Schiff bases with copper(II), nickel(II), and iron(III) nitrates in 1 : 2 molar ratio gave binuclear metal complexes and, in the presence of 8-hydroxyquinoline (8-HQ) or 1,10-phenanthroline (Phen) as secondary ligands (L′), mixed-ligand complexes in two molar ratios 1 : 2 : 2 and 1 : 2 : 1 (L1/L2 : M : L′). The complexes were characterized by elemental and thermal analyses, IR, electronic, mass, and ESR spectral studies, as well as conductivity and magnetic susceptibility measurements. The spectroscopic data reveal that the Schiff-base ligands were dibasic or tetrabasic hexadentate ligands. The coordination sites with the metal ions are two azomethine nitrogens, two oxygens of phenolic groups, and two oxygens of carboxylic groups. Copper(II) complexes were octahedral and square planar while nickel(II) and iron(III) complexes were octahedral. The Schiff bases, H4L1 and H4L2, and some of their metal complexes showed antibacterial activity towards Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative (Pseudomonas fluorescens and Pseudomonas phaseolicola) bacteria and antifungal activity towards the fungi Fusarium oxysporium and Aspergillus fumigatus.

Ligational behavior of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands towards VO(IV), Ce(III), Th(IV) and UO2(VI) ions: synthesis, structural characterization and biological studies.

Mono- and binuclear VO(IV), Ce(III), Th(IV) and UO(2)(VI) complexes of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands derived from 4,6-diacetylresorcinol were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, UV-vis, ESR, (1)H NMR and mass spectra as well as conductivity and magnetic susceptibility measurements and thermal analyses. The thiosemicarbazone (H(4)L(1)) and the semicarbazone (H(4)L(2)) ligands behave as dibasic pentadentate ligands in case of VO(IV) and UO(2)(VI) complexes, tribasic pentadentate in case of Ce(III) complexes and monobasic pentadentate in case of Th(IV) complexes. However, the thiocarbohydrazone ligand (H(3)L(3)) acts as a monobasic tridentate ligand in all complexes except the VO(IV) complex in which it acts as a dibasic tridentate ligand. The antibacterial and antifungal activities were also tested against Rhizobium bacteria and Fusarium-Oxysporium fungus. The metal complexes of H(4)L(1) ligand showed a higher antibacterial effect than the free ligand while the other ligands (H(4)L(2) and H(3)L(3)) showed a higher effect than their metal complexes. The antifungal effect of all metal complexes is lower than the free ligands.

Mononuclear, homo- and hetero-binuclear complexes of 1-(5-(1-(2-aminophenylimino)ethyl)-2,4-dihydroxyphenyl)ethanone: synthesis, magnetic, spectral, antimicrobial, antioxidant, and antitumor studies

Abstract A new Schiff base, H2L, was prepared by condensation of 4,6-diacetylresorcinol with o-phenylenediamine in molar ratio 1 : 1. The ligand reacted with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), oxovanadium(IV), and dioxouranium(VI) ions in the absence and presence of LiOH to yield mononuclear and homobinuclear complexes. The mononuclear dioxouranium(VI) complex [(HL)-(UO2)(OAc)(H2O)]·5H2O was used to synthesize heterobinuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H-, and 13C-NMR, electronic, ESR and mass spectra, conductivity, and magnetic susceptibility measurements as well as thermal analysis. In the absence of LiOH, mononuclear complexes (1, 4, and 9) were obtained; in the presence of LiOH, binuclear complexes (3, 5, 7, and 10) as well as mononuclear complexes (2, 6, and 8) were obtained. In the mononuclear complexes, the coordinating sites are the phenolic oxygen, azomethine nitrogen, and amino nitrogen. In addition to these coordinating sites, the free carbonyl and phenolic OH are involved in coordination in binuclear complexes. The metal complexes exhibited octahedral, tetrahedral, and square planar geometries while the uranium is seven-coordinate. The antimicrobial and antioxidant activities of the ligand and its complexes were investigated. The ligand and the metal complexes showed antitumor activity against Ehrlich Acites Carcinoma. Graphical abstract

Synthesis, molecular orbital, optical and device characterization of mononuclear mixed ligand nickel(II) complex of phthalate with N,N,N′,N′-tetramethylethylenediamine for photodiode applications

In this work, a new synthesized mononuclear mixed ligand nickel(II) complex was characterized by various techniques. Crystalline characteristics of [Ni(Phth)(Me4en)(H2O)2]·4H2O were studied by using transmission electron microscope(TEM). Well crystalline structure corresponds to the hexagonal crystal system and identified by selected area electron diffraction (SAED) were achieved. Coordination of the nickel(II) ion with the functional groups of the ligands was established from the IR spectrum. Molar conductance of the current complex in DMF (10(-3)mol/L) indicated a non-electrolytic nature of the complex. Electronic spectra showed a strong band in the region 661-684nm; MeCN (661nm), CHCl3 (663nm), MeOH (667nm), Me2CO (675nm), DMSO (682nm) and DMF (684nm) which can be assigned to (3)A2g(F)→(3)T1g(F) transition of an octahedral structure around nickel(II). Multiple peaks were easily resolved from the spectral dependence of the absorption coefficient (α) measurements and the analysis near the fundamental absorption edge showed two direct allowed transition with energy gaps of 1.18 and 2.53eV. Dark current-voltage and capacitance-voltage characteristics of [Ni(Phth)(Me4en)(H2O)2]·4H2O/n-Si heterojunctions were studied to extract the main important parameters of the heterojunction device. The electrical characteristics of the heterojunction device under illumination hold the suitability of the device for optoelectronic applications.

Synthesis and characterization of N3S2 donors macrocyclic copper(II) complexes. Catechol oxidase and phenoxazinone synthase biomimetic catalytic activity

ABSTRACTA new series of copper(II) complexes have been synthesized with macrocyclic ligands L1 and L2 having N3S2-donating atoms in the 12-membered macrocyclic ring. The structure characterization of these newly synthesized copper(II) complexes was achieved by various physicochemical techniques. It has been shown that the stereochemistry of complexes is dependent on the type of counter anions incorporated in the complex molecule. Mimicking copper oxidase enzymes, namely catechol oxidase and phenoxazinone synthase, was investigated and the results obtained demonstrated that there is a correlation between the structural properties of these copper(II) complexes and the oxidase biomimetic catalytic activities. Kinetic measurements revealed second-order dependence on the catalyst concentration for 3,5-DTBCH2 and first order in the case of OAPH. On the other hand, for the substrate concentration dependence, a saturation-type behavior was detected for both 3,5-DTBCH2 and OAPH. Addition of Lewis base, triethylami...