Maryam Shayesteh

Synthesis, characterization, and X-ray crystal structures of metal complexes with new Schiff-base ligands and their antibacterial activities

Two new potentially hexadentate Schiff bases, [H2L1] and [H2L2], were prepared by condensation of 2-(3-(2-aminophenoxy)naphthalen-2-yloxy)benzenamine with 3,5-di-tert-butyl-2-hydroxy benzaldehyde and o-vanillin, respectively. Reaction of these ligands with cobalt(II) chloride, copper(II) perchlorate, and zinc(II) nitrate gave complexes ML. The ligands and their complexes have been characterized by a variety of physico-chemical techniques. The solid and solution state investigations show that the complexes are neutral. Molecular structures of [CuL1], [CoL1] · C7H8, and [ZnL2] · CH3CN, which have been determined by single-crystal X-ray diffraction, indicate that [CuL1] and [ZnL2] · CH3CN display distorted square planar and distorted trigonal-bipyramidal geometry, respectively; the geometry around cobalt in [CoL1] · C7H8 is almost exactly between trigonal bipyramidal and square pyramidal. The synthesized ligands and their complexes were screened for their antibacterial activities against eight bacterial strains and the ligands and complexes have antibacterial effects. The most effective ones are [CuL2] against Proteus vulgaris, Serratia marcescens, Staphylococcus subtilis, [H2L1] against S. subtilis, and [H2L2] against S. subtilis.

Synthesis and characterization of a series of transition metal complexes with a new symmetrical polyoxaaza macroacyclic Schiff base ligand: X-ray crystal structure of cobalt(II) and nickel(II) complexes and their antibacterial properties

A new symmetrical [N4O2] hexadentate Schiff base ligand, (E)-N-(pyridin-2-ylmethylene)-2-(3-(2-((E)-pyridin-2-lmethyleneamino)phenoxy)naphthalen-2-yloxy)benzenamine, abbreviated to L, and its complexes of Ni(II), Cu(II), Zn(II), Co(II), Cd(II) and Mn(II) have been synthesized in the presence of metal ions. The complexes were structurally characterized by elemental analyses, IR, UV-Vis, NMR and molar conductivity. The crystal structures of two complexes, [NiL(ONO2)2]·2H2O and [CoLCl2]CH3OH·0.5H2O, have been determined by a single crystal X-ray diffraction study. In these complexes, the ligand is coordinated in a neutral form via pyridine and azomethine nitrogen atoms. The metal ions complete their six coordination with two coordinated nitrate or chloride ions, forming a distorted octahedral geometry. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Enterococcus faecalis, Bacillus cereus and Staphylococcus epid and also against the three Gram-negative bacteria: Citrobacter freundii, Enterobacter aerogenes and Salmonella typhi. The activity data show that the complexes are more potent antibacterials than the parent Schiff base.

Synthesis, characterization, and electrochemical study of two new macroacyclic Schiff bases and their copper(II) and zinc(II) complexes

Two new potentially octadentate N2O6 Schiff-base ligands 2-((E)-(2-(2-(2-((E)-2-hydroxy-3-methoxybenzylideneamino)phenoxy)phenoxy)phenylimino)methyl)-6-methoxyphenol H2L1 and 2-((E)-(2-(2-(2-((E)-2-hydroxy-3-methoxybenzylideneamino)phenoxy)-4-tert-butylphenoxy)phenylimino)methyl)-6-methoxyphenol H2L2 were prepared from the reaction of O-Vaniline with 1,2-bis(2′-aminophenoxy)benzene or 1,2-bis(2′-aminophenoxy)-4-t-butylbenzene, respectively. Reactions of H2L1 and H2L2 with copper(II) and zinc(II) salts in methanol in the presence of N(Et)3 gave neutral [CuL1] · 0.5CH2Cl2, [CuL2], [ZnL1] · 0.5CH2Cl2, and [ZnL2] complexes. The complexes were characterized by IR spectra, elemental analysis, magnetic susceptibility, ESI–MS spectra, molar conductance (Λm), UV-Vis spectra and, in the case of [ZnL1] · 0.5CH2Cl2 and [ZnL2], with 1H- and 13C-NMR. The crystal structure of [ZnL1] · 0.5CH2Cl2 has also been determined showing the metal ion in a highly distorted trigonal bipyramidal geometry. The electrochemical behavior of H2L2 and its Cu(II) complex, [CuL2], was studied and the formation constant of [CuL2] was evaluated using cyclic voltammetry. The logarithm value of formation constant of [CuL2] is 21.9.

Probing the effect of arm length and inter- and intramolecular interactions in the formation of Cu(II) complexes of Schiff base ligands derived from some unsymmetrical tripodal amines

The syntheses of two previously known, 2-((2-aminoethyl)(pyridin-2-ylmethyl)amino)ethanol (1) and 2-((3-aminopropyl)(pyridin-2-ylmethyl)amino)ethanol (2), and four new unsymmetrical N-capped tripodal amines, 2-((4-aminobutyl)(pyridin-2-ylmethyl)amino)ethanol (3), 3-((2-aminoethyl)(pyridin-2-ylmethyl)amino)propan-1-ol (4), 3-((3-aminopropyl)(pyridin-2-ylmethyl)amino)propan-1-ol (5) and 3-((4-aminobutyl)(pyridin-2-ylmethyl)amino)propan-1-ol (6), are reported. The ligands (3–4) feature a longer arm, 3-hydroxypropyl or butylamino, than in the analogues previously employed (2-hydroxyethyl arm, ethylamino-arm or propylamino-arm in 1 and 2). All six tripodal amines, 1–6, are equipped with a 2-methylpyridyl-arm and either an ethylamino-arm (1 and 4), propylamino-arm (2 and 5) or butylamino-arm (3 and 6). The new amines, 3–6, have been employed in one pot condensation reactions with 2-hydroxy-1-naphthaldehyde and salicylaldehyde (and its derivatives) in the presence of Cu(II) metal ions to generate a series of new mononuclear complexes, [MIILaldi](ClO4) as well as new dinuclear complexes [CuIILaldi]2(ClO4)2 of new ligands Laldi. Four monomeric complexes and one dimeric complex have been characterised by single crystal X-ray diffraction, revealing a distorted square-pyramidal copper(II) ion. A general comparison between these structures shows that the number and types of chelate ring sequences around the metal ions are important in the formation of structures. Theoretical studies show that the 3-hydroxypropyl arm in these complexes is a weak coordinating group and it can readily be removed from the coordination sphere of metal ions, resulting in a dimerised four coordinate complex. Calculations show that the interaction between the two monomeric fragments is very weak.

Synthesis and characterisation of macrocyclic copper(II) complexes containing N 3 O 4 donor sets

Two new macrocyclic Schiff-base complexes of Cu(II) have been prepared by the template reaction of 2,6-bis (2-formylphenoxymethyl)pyridine with 1,2-bis(2′-aminophenoxy)benzene [L1] or with 1,2-bis(2′-aminophenoxy)-4-tert-butylbenzene [L2] in the presence of Cu(II) perchlorate. The amines used have low flexibility and therefore the formation of complexes was very difficult. The synthesised 23-membered, heptadentate N3O4 complexes were characterised by elemental analysis, IR, and FAB-mass spectroscopy.