Mehmet Tümer

Antimicrobial activity studies of the binuclear metal complexes derived from tridentate Schiff base ligands

Three novel tridentate Schiff base ligands derived from␣the 3-hydroxysalicylaldehyde (H2L1), 4-hydroxysalicylaldehyde (H2L2) and 5-bromosalicylaldehyde (H2L3) with a new amine N-(pyridyl)-2-hydroxy-3-methoxy-5-aminobenzylamine (2) have been prepared. The ligands and their metal complexes have been characterized by elemental analyses, conductivity and magnetic susceptibility measurements, i.r., electronic absorption and 1H and 13C n.m.r. spectroscopy. All complexes are binuclear and, in some, the H2O molecules are coordinated to the metal ion. Antimicrobial activities of the ligands and their complexes have been tested against to the Bacillus subtilis IMG 22 (bacteria), Micrococcus luteus LA 2971 (bacteria) Saccharamyces cerevisiae WET 136 (yeast), and Candida albicans CCM 314 (yeast). Thermal properties of all complexes have been studied by t.g. and d.t.a techniques.

Antimicrobial activity studies of mononuclear and binuclear mixed-ligand copper(II) complexes derived from Schiff base ligands and 1,10-phenanthroline

Mixed-ligand complexes of copper(II) with 1,10-phenanthroline and various Schiff bases have been prepared and characterized by elemental analysis, electronic and i.r. spectra, magnetic moment and molar conductance data. The Schiff base behave as bidentate ligands, and the mixed-ligand copper(II) complexes of the ligands HL1′′, HL2′′ and HL4′′ are binuclear. The conductivity data for all the complexes are consistent with those expected for an electrolyte. Antimicrobial activities of some of the ligands and complexes have been tested against Bacillus megaterium and Candida tropicalis. 1H and 13C n.m.r. spectra have been recorded in order to solve the solution structure of the ligands. Thermal properties of all complexes have been studied by the d.t.a. and t.g.a. techniques.

Antioxidant, electrochemical, thermal, antimicrobial and alkane oxidation properties of tridentate Schiff base ligands and their metal complexes

In this study, two Schiff base ligands (HL(1) and HL(2)) and their Cu(II), Co(II), Ni(II), Pd(II) and Ru(III) metal complexes were synthesized and characterized by the analytical and spectroscopic methods. Alkane oxidation activities of the metal complexes were studied on cyclohexane as substrate. The ligands and their metal complexes were evaluated for their antimicrobial activity against Corynebacterium xerosis, Bacillus brevis, Bacillus megaterium, Bacillus cereus, Mycobacterium smegmatis, Staphylococcus aureus, Micrococcus luteus and Enterococcus faecalis (as gram-positive bacteria) and Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Yersinia enterocolitica, Klebsiella fragilis, Saccharomyces cerevisiae, and Candida albicans (as gram-negative bacteria). The antioxidant properties of the Schiff base ligands were evaluated in a series of in vitro tests: 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and reducing power activity of superoxide anion radical generated non-enzymatic systems. Electrochemical and thermal properties of the compounds were investigated.

COPPER(II), COBALT(III), NICKEL(II), PALLADIUM(II), AND ZINC(II) COMPLEXES OF THE SCHIFF BASE LIGANDS DERIVED FROM 2,6-DIACETYLPYRIDINE AND PHTHALDIALDEHYDE

Two new ligands, N,N′-bis[2-hydroxy-3-methoxy-N-(pyridyl) benzylamine]-2,6-di acetylidenepyridine (H2L′) and N, N′-bis [2-hydroxy-3-methoxy-N-(pyridyl)benzylamine]-1,2-phthaldialdimine (H2L″) and their Cu(II), Co(III), Ni(II), Pd(II) and Zn(II) complexes have been prepared and characterized by elemental analyses, IR, electronic spectra, magnetic moments, 1H and 13C NMR spectra, mass spectral and molar conductance data. The mononuclear Co(III) complexes of these ligands have been isolated with two molecules of DMF. While the Co(III) complex of H2L′ is a 1:1 electrolyte, the other complexes and ligands are non-electrolytes. The ligands H2L′ and H2L″ and some of their complexes show antimicrobial activity against bacteria and yeast.

Transition metal complexes of bidentate Schiff base ligands

New Schiff base ligands derived from vanillin (HL1), 4-dimethylaminobenzaldehyde (HL2) and 3,5-di-t-butyl-4-hydroxybenzaldehyde (HL3) with N-(pyridyl)-3-methoxy-4-hydroxy-5-aminobenzylamine (2) and their copper(II), cobalt(II), nickel(II), oxovanadium(IV) and zinc(II) transition metal complexes have been synthesized and characterized by elemental analyses, electronic and i.r. spectra, molar conductance data and by 1H and 13C n.m.r. spectra. The results indicate that the ligands coordinate through azomethine nitrogen and phenolic oxygen to the metal ions. In like manner, it was found that the pyridine and amine nitrogen atoms are not coordinated to the metal ions. The 1H and 13C n.m.r. spectral data confirmed the suggested structure for the Schiff base ligands, and the mass spectra results confirmed the proposed structure of the ligands. The antimicrobial activity properties of the ligands and their metal complexes have been studied.

Synthesis, Characterization and Stability Constants of Polynuclear Metal Complexes

Unsymmetric tridentate ligands, 4-methyl-2,6-di(4-methyliminomethyl)phenol (HL1), 4-(t-butyl)-2,6-di(4-methylphenyliminomethyl)phenol (HL2), 2,6-di(4-bromophenyliminomethyl)-4-methylphenol (HL3), 2,6-di(4-bromophenyliminomethyl)-4-(t-butyl)phenol (HL4), 2,6-di(4-hydroxyphenyliminomethyl)-4-methylphenol (HL5) and 4-(t-butyl)-2,6-di(4-hydroxyphenyliminomethyl)phenol (HL6), and their binuclear CuII, CoII and NiII complexes were synthesized and characterized by elemental analysis, FT-IR, u.v.-vis spectrometry magnetic moments, 1H(13C)-n.m.r. and mass spectral data. Also, the electrical conductivities of the complexes have been measured using 10-3 M solutions in MeCN. The complexes are weak electrolytes. In the electronic spectra of the complexes of the HL1-HL6 ligands, the 480-410 nm band has been determined as the charge-transfer band. While the HL5 and HL6 ligands have five potential donor atoms, other ligands have only three. Protonation constants of the ligands have been studied in dioxan-water mixtures. In addition, the antimicrobial properties of the ligands and their metal complexes have been studied:Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcus faecalis, bacteria and Saccoramyces cerevisia, yeast. The keto-enol tautomeric equilibria of the ligands have been investigated in polar and non-polar solvents.

Synthesis and Characterisation of Binuclear Cu(II), Ni(II) and Co(II) Chelates with Tetradentate Schiff Base Ligands Derived from 1,5-Diaminonaphthalene

Abstract A new series of copper(II), nickel(II) and cobalt(II) chelates containing the binucleating tetradentate Schiff base ligands N,N′-bis(salicylidene)-1,5-diaminonaphthalene (H2L), N,N′-bis(3-methoxysalicylidene)-1,5-diaminonaphthalene (H2L′) and N,N′-bis(4-hydroxysalicylidene)-1,5-diaminonaphthalene (H2L) have been synthesized. These compounds have been characterized by elemental analyses, conductivity measurements, magnetic susceptibility, thermoanalyses (TG-DTA), infrared and electronic spectral data. The results suggest that the Schiff bases function as tetradentate ligands coordinating through the ONNO donor system and indicate a binuclear structure for the Cu(II) complexes with pseudo-tetrahedral geometry and binuclear structures for the Co(II) and Ni(II) complexes with pseudo-octahedral geometry. All complexes are non-electrolytes.

Synthesis and Characterization of Mononuclear Copper(II), Cobalt(II) and Nickel(II) Chelates with New Bidentate Aromatic Schiff Bases

Abstract Copper(II), cobalt(II) and nickel(II) complexes of ligands such as N-(3-hydroxy salicylidene)-3, 5-di(tert-butyl)-4-hydroxyaniline (L 1H) and N-(3, 4-dihydroxysalicylidene)-3, 5-di(tert-butyl)-4-hydroxyaniline (L2H) have been prepared and characterized by elemental analyses, magnetic moment, infrared, electronic absorption spectral data and molar conductance. Thermal decomposition studies show that the copper, cobalt and nickel complexes decompose with the loss of hydrated water followed by loss of the organic ligand to give the metal oxides. The 1H and 13C NMR spectra of the Schiff base ligands have been recorded. Referee I: N. K. Kaushik Referee II: M. Athar

Synthesis, Characterization and Thermal Studies of Mononuclear and Binuclear Complexes of Copper(II) with Schiff Bases Derived from 1-Phenyl-2,3-dimethyl-4-amino-5-pyrazolone

Abstract A series of copper(II) complexes with ligands derived from the Schiff base reaction of 1-phenyl-2,3-dimethyl-4-amino-5-pyrazolone with 4-hydroxysalicylaldehyde (L1H), 3-methoxysalicylaldehyde (L2H) and 2-hydroxynaphtaldehyde (L3H) have been prepared. These complexes have been characterized by elemental analyses, magnetic susceptibility, infrared and electronic spectral data. Molar conductivities of the complexes at room temperature were measured. The conductivity values of the L1H and L2H complexes indicate weak electrolyte behaviour, whereas the L3H complex is a non-electrolyte. The thermal decomposition of the complexes has been studied by thermogravimetry and differential thermal analyses. These studies show that each copper compound decomposes to the metal halide and finally the metal oxide.

Synthesis and Spectral Characterization of Metal Complexes Containing Tetra- and Pentadentate Schiff Base Ligands

Abstract Two new Shiff base ligands, N,N′-bis[2-hydroxy-3-methoxy-N-(p-methyl phenylene)benzylamine]-2,6-diacetylpyridinimine (H2L1), N,N′-bis[2-hydroxy-3-methoxy-N-(p-methylphenylene)benzylamine]phtaldialdimine (H2L2) and their Cu(II), Co(III), Ni(II), Pd(II), VO(IV) and Zn(II) metal complexes have been prepared and characterized by elemental analyses, FT-IR, electronic spectra, magnetic moments, 1H and 13C NMR spectra, mass spectral and molar conductance data. The mononuclear Co(III) complexes of these ligands have diamagnetic character and octahedral geometry around the metal ion. The ketoimine-enolimine equilibria of the ligands were investigated by electronic spectra and showed that the ligands preferred the ketoimine form in nonpolar solvents. It has been found that the ligands and their complexes are non-electrolytic in nature. Spectral measurements showed that the ligands were coordinated to the metal ion through the azomethine nitrogen and phenolic oxygen atoms. The TG and DTA properties of the compounds have been studied.