Selahattin Serin

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.

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 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 Complex Formation of the Structural Isomers of 2,3-Bis(Hydroxyimino)-2,3-Dihydro-4H-1,4-Benzothiazine

Abstract 2,3-Bis(hydroxyimino)-2,3-dihydro-4H-1,4-benzothiazine (BTIH2) has been synthesized from 0-aminothiophenol and cyanogen-di-N-oxide which was obtained by treating anti-dichloroglyoxime with 1N Na2CO3 at - 10°C. The amphi-isomer was prepared by crystallizing the crude product in pyridine/water (1:5). The conversion of the crude product to anti-BTIH2 was accomplished by the effect of HC1 and neutralizing afterwards, anti-BTIH2 formed square planar, H-bridged complexes with Ni(II), Cu(II), and Co(II). The N,0-chelated tetrahedral Ni(II) complex of amphi-BTIH2 was yellow-green. 1H-NMR, IR, and UV-VIS data are presented.

Preparation, Spectroscopic Characterisation and Thermal Analyses Studies of the Cu(II), Pd(II) and Vo(IV) Complexes of Some Schiff Base Ligands

Abstract New Schiff base ligands. N-(3-methoxysalicylidene)-3, 5-di(tert-butyl)-4-hydroxy aniline (HL1), N-(3-hydroxysalicylidene)-3, 5-di(tert-butyl)-4-hydroxyaniline (HL2) and N-(4-hydroxysalicylidene)-3, 5-di(rert-butyl)-4-hydroxyaniline (HL3) with their Cu(II), Pd(II) and VO(IV) coinplexes were synthesized and characterized by elemental analyses, IR, electronic absorption spectral data, magnetic moment and molar conductance For the ligands and their Pd(II) complexes. 1H and 13C NMR spectra were obtained 1H and 13C NMR spectra suygest that the ligands in the Pd(II) complexes coordinate through the nitrogen atom of the azomethine group and the oxysen atom of the phenolic (C-OH) group All the compounds were found to be non-electrolytes in DMSO However, the Pd(II) complexes exhibit low conductance m DMF due to solvolysis Thermal studies show that the complexes decompose with the loss of water. followed by the orsanic ligand to give the corresponding metal oxides

Synthesis, characterization, and biological properties of Ni(II), Co(II), and Cu(II) complexes of Schiff bases derived from 4-aminobenzylamine

New Schiff bases, N,N′-bis(salicylidene)-4-aminobenzylamine (H2L1), N,N′-bis(3-methoxysalicylidene)-4-aminobenzylamine (H2L2), and N,N′-bis(4-hydroxysalicylidene)-4-aminobenzylamine (H2L3), with their nickel(II), cobalt(II), and copper(II) complexes have been synthesized and characterized by elemental analyses, electronic absorption, FT-IR, magnetic susceptibility, and conductance measurements. For the ligands, 1H and 13C NMR and mass spectra were obtained. The tetradentate ligands coordinate to the metal ions through the phenolic oxygen and azomethine nitrogens. The keto-enol tautomeric forms of the Schiff bases H2L1, H2L2, and H2L3 have been investigated in polar and apolar solvents. All compounds were non-electrolytes in DMSO (∼10−3 M) according to the conductance measurements. Antimicrobial activities of the Schiff bases and their complexes have been tested against Acinobacter baumannii, Pseudomonas aeruginosa, Micrococcus luteus, Bacillus megaterium, Corynebacterium xerosis, Staphylococcus aureus, Escherichia coli, Candida albicans, Rhodotorula rubra, and Kluyveromyces marxianus by the disc diffusion method; biological activity increases on complexation.