Nadia E.A. El-Gamel

PREPARATION, CHEMICAL CHARACTERIZATION, AND ELECTRONIC SPECTRA OF 6-(2-PYRIDYLAZO)-3-ACETAMIDOPHENOL AND ITS METAL COMPLEXES

The stereochemistry of new iron(III), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes of 6-(2-pyridylazo)-3-acetamidophenol (H2L) is studied on the basis of their analytical, spectroscopic, magnetic, thermal and conductance data. The dissociation constant of the ligand as well as the stability constants of its metal complexes have been determined spectrophotometrically. On the basis of the infrared spectra the coordination behaviour of the ligand to the metal ions is investigated. Magnetic susceptibility and solid reflectance spectral measurements are used to infer the structure. The prepared complexes are found to have the general formulae [M(HL)(H2O)x](A) · yH2O (M = Cu(II), Zn(II), Cd(II) and Fe(III); HL = 6-(2-pyridylazo)-3-acetamidophenolate; A = acetate in case of Cu(II) and Zn(II) or chloride in case of Cd(II) and Fe(III), x = 1–3 and y = 0–5) or [M(H2L)(H2O) x ]Cl2 · yH2O (M = Ni(II) and Co(II); H2L = 6-(2-pyridylazo)-3-acetamidophenol, x = 3 and y = 5–6).

Complexes of 2-(2-benzimidazolylazo)-4-acetamidophenol, a phenoldiazenyl-containing ligand. Could this be a moiety suitable for Zn and Cd extraction?

Abstract The preparation and structural identification of new Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of 2-(2-benzimidazolylazo)-4-acetamidophenol (BIAAP) are studied on the basis of their analytical, spectroscopic, magnetic and conductance data. The dissociation constant of the BIAAP as well as the stability constant of its metal complexes have been determined by spectrophotometric methods. The stability of the complexes follows the sequence: Zn(II)>Cd(II)≫Co(II)>Cu(II)∼Fe(III)>Ni(II). The high stability of BIAAP towards Zn(II) and Cd(II) over the other ions is remarkable, in particular over Cu(II), a fact that may be of technological interest. The isolated complexes are found to have the general formulae [M(BIAAP)2].xH2O (M=Co(II), Ni(II), Cu(II) (x=4), M=Zn(II), Cd(II) (x=2)) or [Fe(BIAAP)2]Cl.2H2O. Structural information has been taken from spectroscopic, magnetic and conductance measurements. The coordination number of the metal ions is found to be six (Fe(III), Co(II), Ni(II) and Cu(II)) and four (Zn(II) and Cd(II)) with binding through the phenolate O, azo N and, if necessary with the imidazole N3 atom. For Zn(II) and Cd(II) the phenoldiazenyl moiety seems to be the relevant one. Considering the higher stability of the Zn(II) versus Cu(II) complex, it is proposed that this moiety may be of interest to design Zn selective complexing and/or extracting agents.

Thermal Behaviour of Metal Complexes of 6-(2-Pyridylazo)-3-acetamidophenol

The present work aims chiefly to study the thermal behaviour of complex compounds with general formula: [M(HL)⋅xH2O](A)⋅yH2O (where HL=C13H11N4O2=6-(2-pyridylazo)-3-acetamidophenol (PAAP), M=Cu(II), Zn(II), Cd(II) and Fe(III) x=1, 3; y=2, 5) while A=CH3COO− (Ac), Cl2. The second formula is [M(H2L)⋅xH2O]Cl2⋅yH2O, (where H2L=C13H12N4O2 (PAAP), M=Ni(II), Co(II) x=3; y=4, 6). The compounds were identified by elemental analysis, FT-IR spectra and TG/DTG,DTA methods. It was found that during the thermal decomposition of complex compounds water molecules of crystallization are released in the first step. In the next step the pyrolysis of organic ligand takes place. Metal oxide remained as a solid product of the thermal decomposition. Mass spectroscopy has been used for the determination of the thermal decomposition on the intermediate products. It was found that the thermal stability of the studied compounds increases as the ionic radii decreases. The activation energy E, the entropy change ΔS*, the enthalpy ΔH* change and Gibbs free energy change ΔG* were calculated from TG curve.

Synthesis, structural characterization and antimicrobial activity evaluation of metal complexes of sparfloxacin

The synthesis and characterization of binary Cu(II)- (1), Co(II)- (2), Ni(II)- (3), Mn(II)- (4), Cr(III)- (5), Fe(III)- (6), La(III)- (7), UO(2)(VI)- (8) complexes with sparfloxacin (HL(1)) and ternary Cu(II)- (9), Co(II)- (10), Ni(II)- (11), Mn(II)- (12), Cr(III)- (13), Fe(III)- (14), La(III)- (15), UO(2)(VI)- (16) complexes with sparfloxacin (HL(1)) and DL-alanine (H(2)L(2)) complexes are reported using elemental analysis, molar conductance, magnetic susceptibility, IR, UV-Vis, thermal analysis and (1)H-NMR spectral studies. The molar conductance measurements of all the complexes in DMF solution correspond to non-electrolytic nature. All complexes were of the high-spin type and found to have six-coordinate octahedral geometry except the Cu(II) complexes which were four coordinate, square planar and U- and La-atoms in the uranyl and lanthanide have a pentagonal bipyramidal coordination sphere. The antimicrobial activity of these complexes has been screened against two gram-positive and two gram-negative bacteria. Antifungal activity against two different fungi has been evaluated and compared with reference drug sparfloxacin. All the binary and ternary complexes showed remarkable potential antimicrobial activity higher than the recommended standard agents. Ni(II)- and Mn(II) complexes exhibited higher potency as compared to the parent drug against gram-negative bacteria.

Thermal and kinetic studies on solid complexes of 2-(2-benzimidazolylazo)-4-acetamidophenol with some transition metals

The preparation and characterization of 2-(2-benzimidazolylazo)-4-acetamidophenol (BIAAP) complexes are reported. Different physico-chemical methods like IR, Magnetic, solid reflectance spectra and molar conductance, were used to investigate the structure of BIAAP complexes. In particular, the thermal decomposition of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of BIAAP is studied in nitrogen atmosphere. All the complexes do not contain coordinated water molecules but contain (2-4) water molecules of crystallization. The water molecules were removed in a single step. The complexes of Co(II) and Ni(II) ions exhibited a phase transition and the decomposition or combustion of BIAAP occurred in the second and subsequent steps. The final decomposition products were identified by mass spectrometry as the corresponding metal oxides or carbonate. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes were evaluated and the stabilities of the thermal decomposition of the complexes are discussed. From the kinetic point of view, it is found that the thermal stability of the complexes follows the order Ni(II) > Cu(II) > Zn(II) > Fe(III) > Co(II) > Cd(II).

Metal chelates of ampicillin versus amoxicillin: synthesis, structural investigation, and biological studies

Solid chelates derived from some alkaline earth and transition metal complexes with ampicillin (Hamp, a) and amoxicillin (Hamox, b) were synthesized and characterized using elemental analysis, molar conductivity, IR, magnetic susceptibility, and thermogravimetric studies. Both drugs behave as tetradentate ligands coordinating to metal through amino, imino, and carboxylate as well as through β-lactamic carbonyl. All chelates have octahedral geometry except Cu(II) complexes which have square planar structure and uranium has pentagonal bipyramidal coordination. 1H- and 13C-NMR of the Zn(II) and UO2(VI) chelates are compared with the free ligands. The antimicrobial activity of the prepared chelates was determined.

The interactions of metal ions with nonsteroidal anti-inflammatory drugs (oxicams)

Much work has been focused on interactions of metal ions with nonsteroidal anti-inflammatory drugs (oxicams). Numerous attempts to synthesize several metal complexes have been published. This review highlights the synthesis and properties of the synthesized metal complexes. Different physico-chemical methods (IR, UV–Vis, measurement, thermal analysis, and NMR spectroscopy) as well as the bioactivity of the metal compounds are mentioned.

s-Triazine and tri-s-triazine based organic-inorganic hybrid gels prepared from chlorosilanes by exchange reactions

Hybrid polymers [(DeltaO3)4Si3]n and [(DeltaO3)SiMe]n (where Delta = C6N7 or C3N3) have been prepared by a novel sol-gel process based on exchange reactions of MeSiCl3 or SiCl4 with C6N7(OSiMe3)3 and C3N3(OSiMe3)3.

Coordination behaviour and biopotency of metal NN salen complexes

Coordination of Co(II) (1), Fe(III) (2) and UO2(IV) (3) with N,N′-bis(2-methoxybenzylidene)ethylenediamine Schiff base is structurally characterized using different spectroscopic and thermal studies. The reported compounds are examined as antimicrobial agents by screening their biological interactions; they showed enhanced antimicrobial activity compared with that of the free ligand. The cytotoxicity of the prepared compounds against L929 mouse fibroblasts and HEK 293 cells is determined by the MTT assay. The cytotoxic behavior is investigated for their possible use in tracking of cells and tissues. As observed in the in vitro assay, the complexes exhibited a low extent of cytotoxicity on the selected cells; they displayed remarkable potential viability compared with the same cells treated with the salen Schiff base. The cytotoxicity of the uranyl complex is lower than that of the other prepared complexes at a defined concentration, which indicates a synergistic effect upon coordination to the uranium ion. This study reveals that metal ions have quite an important role in the cytotoxicity. The results revealed that coordination may be considered as an interesting strategy to significantly reduce the cytotoxic dose, which may help to overcome the limitations of use of any metal and to understand their metabolism in living beings. In this work, the variation in chemical and coordination behaviour that has successfully enabled the integration of the target candidates into biological environments, which allows further in vivo developments in therapeutical and medical fields is discussed.

Uranyl and transition metal chelates of tenoxicam. Crystal structures of trans,trans -[Co(II)(Hten)2(dmso)2], trans , trans -[Zn(II)(Hten)2(dmso)2] and cis , cis -[UO2(VI)(Hten)2(H2O)] · 2C2H5OH

The synthesis and characterization of ternary Fe(III)- (1), Co(II)- (2), Ni(II)- (3), Cu(II)- (4), Zn(II)- (5) and UO2(VI)- (6) chelates with the potent anti-inflammatory drug tenoxicam (H2ten) and (dl-alanine, Hala) are reported. All complexes are octahedral except Cu(II) and Zn(II) chelates, which are tetrahedral, and U-atoms in the uranyl chelates have a pentagonal-bipyramidal coordination sphere. The ternary Co(II) and Zn(II) complexes dissociate in dmso where orange and yellow crystals of trans,trans-[Co(II)(Hten)2(dmso)2] (8) and trans,trans-[Zn(II)(Hten)2(dmso)2] (9), respectively, were obtained. Crystallization of the binary uranyl chelate (7) from ethanol afforded the ethanol solvate cis,cis-[UO2(VI)(Hten)2(H2O)] · 2C2H5OH (7a). trans,trans-[Co(II)(Hten)2(dmso)2] (8) and trans,trans-[Zn(II)(Hten)2(dmso)2] (9) crystallize in the monoclinic space group P21/n while 7a crystallizes in the triclinic space group . The kinetics of the thermal decompositions for 1, 3, 4, 6 and 7 were studied and the thermodynamic parameters E*, ΔH*, ΔS* and ΔG* evaluated.