Synthesis, characterization, and antimicrobial activities of nickel(II) and copper(II) Schiff-base complexes

Studies on Synthesis and Spectral Characterization of Some Transition Metal Complexes of Azo-Azomethine Derivative of Diaminomaleonitrile

New complexes of 2,3-bis(5-(4-chlorophenyl)diazenyl)-2-hydroxybenzylideneamino)maleonitrile (CDHBDMN) with VO(II), Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) were synthesized and characterized by analytical and physicochemical techniques, that is, elemental analyses, molar conductivity, UV, IR, EPR, 1H-NMR spectra, magnetic susceptibility and also by aid of scanning electron microscopy (SEM), nonlinear optical study (NLO), fluorescence spectral studies, and solvatochromic behaviors. Electronic and magnetic susceptibility measurements of the complexes indicate square pyramidal geometry for VO(II), octahedral for Ni(II), and square planar geometry for all the other complexes. The EPR spectral data provide information about their structures on the basis of Hamiltonian parameters and the degree of covalency. These metal complexes were also tested for their antibacterial and antifungal activities to assess their inhibiting potential. Metal-mediated fluorescence enhancement is observed on complexation of the azo Schiff base ligand. The synthesized compounds were investigated for nonlinear optical properties, and the surface morphology of the Cu(II) complex was studied by scanning electron microscopy.

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.

{N,N'-Bis[1-(pyridin-2-yl)ethyl-idene]-propane-1,3-diamine}-(thio-cyanato-κN)copper(II) tetra-fluoridoborate

In the title compound, [Cu(NCS)(C(17)H(20)N(4))]BF(4), the Cu(II) ion is five-coordinated by the four N atoms of the tetra-dentate Schiff base ligand and one N atom of a thio-cyanate ligand, thereby forming a square-pyramidal CuN(5) ccoordination geometry. The dihedral angle between the pyridine rings of the Schiff base is 55.58 (14)°. The F atoms of the tetra-fluoridoborate anion are disordered over two sets of sites with occupancies of 0.614 (3) and 0.386 (3). In the crystal, the components are linked by C-H⋯F inter-actions.

N-benzoylated 1,4,8,11-tetraazacyclotetradecane and their copper(II) and nickel(II) complexes: spectral, magnetic, electrochemical, crystal structure, catalytic and antimicrobial studies

A series of N-benzoylated cyclam ligands incorporating three different benzoyl groups 1,4,8,11-tetra-(benzoyl)-1,4,8,11-tetraazacyclotetradecane (L(1)), 1,4,8,11-tetra-(2-nitrobenzoyl)-1,4,8,11-tetraazacyclotetradecane (L(2)) and 1,4,8,11-tetra-(4-nitrobenzoyl)-1,4,8,11-tetraazacyclotetradecane (L(3)) and their nickel(II) and copper(II) complexes are described. Crystal structure of L(1) is also reported. The ligands and complexes were characterized by elemental analysis, electronic, IR, (1)H NMR and (13)C NMR spectral studies. N-benzoylation causes red shift in the lambda(max) values of the complexes. The cyclic voltammogram of the complexes of ligand L(1) show one-electron, quasi-reversible reduction wave in the region -1.00 to -1.04 V, whereas that of L(2) and L(3) show two quasi-reversible reduction peaks. Nickel complexes show one-electron quasi-reversible oxidation wave at a positive potential in the range +1.05 to +1.15 V. The ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry with nuclear hyperfine spin 3/2. All copper(II) complexes show a normal room temperature magnetic moment values mu(eff) 1.70-1.73 BM which is close to the spin-only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts and hydrolysis of 4-nitrophenylphosphate using the copper(II) and nickel(II) complexes as catalysts were carried out. All the ligands and their complexes were also screened for antimicrobial activity against Gram-positive, Gram-negative bacteria and human pathogenic fungi.

Structural, spectral and biological studies of binuclear tetradentate metal complexes of N3O Schiff base ligand synthesized from 4,6-diacetylresorcinol and diethylenetriamine

The binuclear Schiff base, H2L, ligand was synthesized by reaction of 4,6-diacetylresorcinol with diethylenetriamine in the molar ratio 1:2. The coordination behavior of the H2L towards Cu(II), Ni(II), Co(II), Zn(II), Fe(III), Cr(III), VO(IV) and UO2(VI) ions has been investigated. The elemental analyses, magnetic moments, thermal studies and IR, electronic, 1H NMR, ESR and mass spectra were used to characterize the isolated ligand and its metal complexes. The ligand acts as dibasic with two N3O-tetradentate sites and can coordinate with two metal ions to form binuclear complexes. The bonding sites are the nitrogen atoms of the azomethine and amine groups and the oxygen atoms of the phenolic groups. The metal complexes exhibit either square planar, tetrahedral, square pyramid or octahedral structures. The Schiff base ligand and its metal complexes were tested against four pathogenic bacteria (Staphylococcus aureus and Streptococcus pyogenes) as Gram-positive bacteria, and (Pseudomonas fluorescens and Pseudomonas phaseolicola) as Gram-negative bacteria and two pathogenic fungi (Fusarium oxysporum and Aspergillus fumigatus) to assess their antimicrobial properties. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms.

Bromido{N-methyl-N'-[1-(2-pyrid-yl)ethyl-idene]ethane-1,2-diamine-κN,N',N''}-(thio-cyanato-κN)-copper(II)

In the title mononuclear copper(II) compound, [CuBr(NCS)(C₁₀H₁₅N₃)], the Cu^II atom is five-coordinated by three N atoms of the Schiff base ligand, the N atom of a thio­cyanate ligand and by one bromide ion forming a distorted square-pyramidal geometry. In the crystal structure, mol­ecules are linked through inter­molecular N—H⋯Br hydrogen bonds into chains propagating along [101].

{2-[2-(Ethyl-amino)ethyl-imino-meth-yl]-5-methoxy-phenolato}(thio-cyanato-κN)-copper(II)

In the title mononuclear copper(II) complex, [Cu(C₁₂H₁₇N₂O₂)(NCS)], the Cu^II atom is four-coordinated by an NNO-donor set of the tridentate Schiff base ligand and the N atom of a terminal thio­cyanate ligand in a slightly distorted square-planar geometry.