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Two copper(II) complexes, [Cu2(L1)2]·2H2O (1) and [Cu3(L1)2(NCS)2] (2), and two nickel(II) complexes, [NiL2(NCS)] (3) and [Ni(L2)2(NCS)]·CH3OH (4), were prepared from the fluorine substituted Schiff bases N,N'-bis(4-fluorosalicylidene)-1,2-diaminopropane (H2L1) and 4-fluoro-2-[(2-isopropylaminoethylimino)methyl]phenol (HL2), respectively. The compounds were characterized by physico-chemical methods. Structures of the complexes were further confirmed by single crystal X-ray diffraction. The Cu ions in 1 are square pyramidal, and in 2 are square planar and octahedral. The Ni ion in 3 is square planar, and in 4 is octahedral. All the complexes have effective Jack bean urease inhibitory activities. Complex 1 has the most effective activity, with an IC50 value of 2.1 ± 1.3 μmol L−1. [ABSTRACT FROM AUTHOR]

Urease catalyzes the decomposition of urea into ammonia, which has harmful effects on both human health and fertile soil. Aiming at exploring novel urease inhibitors, a series of hydrazone compounds and their CoIII, CuII, NiII, and ZnII complexes were prepared from 4-methoxy-N'-(pyridin-2-ylmethylene)benzohydrazide (HL). They are [CoClL(NCS)] (1), [CoL2]·Cl·CH3OH·H2O (2), [CuL(NCNCN)]n·nCH3OH (3), [NiL(HL)]·ClO4·CH3OH (4) and [ZnClL(OH2)]·CH3OH (5). The compounds were characterized by physico-chemical methods. Structures of the complexes were further confirmed by single crystal X-ray diffraction. The metal ions in 1, 3, and 5 display square pyramidal coordination and 2 and 4 display octahedral coordination. The inhibitory effects of the compounds on Jack bean urease were evaluated. The results showed that 3 has effective urease inhibitory activity, with IC50 value of (7.3 ± 1.0) μmol L−1. [ABSTRACT FROM AUTHOR]

Five new Ni(II) Schiff base complexes [NiLx(Solv)2] denoted by NiLx,x = 1–5, were synthesized and characterized. The Schiff base ligands were synthesized from the condensation of 5-bromo-2-hydroxy-3-nitrobenzaldehyde with different aliphatic and aromatic diamines. The X-ray crystal structure of NiL3was determined. The ligands and complexes were tested as antibacterial agents against two gram(+) and two gram(−) human pathogenic bacteria. The complexes showed moderate antibacterial activity against both gram type bacteria. The new Ni(II) complexes showed enhanced antibacterial activity compared to the previously reported Cu(II) complexes of the same ligands. [ABSTRACT FROM PUBLISHER]

Density functional theory (B3LYP/6-31G(d)) has been applied for optimization and calculation of the vibrational spectra of the compartmental hexadentate Schiff base derived from 3-formylsalicylic acid and 4,5-dichloro-1,2-phenylenediamine and 12 of its mononuclear complexes with Co(II), Ni(II), and Cu(II). Six of these complexes have the metal ion occupying the inner, N2O2, or the outer, O2O2, coordination sites in square planar geometry. The other six complexes possess octahedral geometry, occupying the inner or the outer coordination sites coordinating, additionally, to two waters. Significant changes in the ligand geometry have been observed in all complexes to permit efficient complexation with the metal. Assignments of the infrared bands are proposed based on calculations. Vibrational frequencies that are important for assignment and confirmation of the coordination sites are reported. Comparison of the total energies of the complexes reveals that inner complexes are more stable than corresponding outer complexes. Selectivity of metal ions to the coordination sites is also discussed. [ABSTRACT FROM AUTHOR]

Ni(II) and Cu(II) metal complexes of simple unsymmetrical Schiff-base ligands derived from salicylaldehyde/5-methylsalicylaldehyde and ethylenediamine or diaminomaleonitrile (DMN) were synthesized. The ligands and their complexes were characterized by elemental analysis, 1H NMR, FT IR, and mass spectroscopy. The electronic spectra of the complexes show d-d transitions in the region at 450-600 nm. Electrochemical studies of the complexes reveal that all mononuclear complexes show a one-electron quasi-reversible reduction wave in the cathodic region. ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry, with nuclear hyperfine spin 3/2. The copper(II) complexes show a normal room temperature magnetic moment value μeff = 1.70-1.74 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 were also carried out. The in vitro antimicrobial activity of the investigated compounds was tested against human pathogenic bacterias such as Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumonia, Pseudomonas aeruginosa and Escherichia coli. The antifungal activity was tested against Candida albicans. Generally, the metal complexes have higher antimicrobial activity than the free ligands. [ABSTRACT FROM AUTHOR]

A series of metal(II) unsymmetrical Schiff-base complexes, {M(C10H6OCH:N(CH2)2N : C(CH3)CH : C(CH3)O), where M=Ni(II), Cu(II) and Zn(II)}, and their 2,2'-dipyridine (bipy) and 1,10-phenanthroline (phen) adducts are synthesized and characterized by microanalysis, magnetic susceptibility, conductance, IR and UV-Vis spectra. The ligand coordinates using the N2O2 chromophore to give a two-metal-center four-coordinate square-planar geometry. IR and UV-Vis spectra are consistent with octahedral adducts. The compounds are non-electrolytes in nitromethane and magnetic moments indicate that the complexes are magnetically dilute. The antimicrobial activity of the compounds against ten bacteria and one fungus are reported. The Cu(II) and Zn(II) complexes showed good activity against many of the organisms while their adducts are generally not sensitive. The minimum inhibitory concentrations (MICs) of the sensitive compounds are between 3.0-13.0 mg mL-1. [ABSTRACT FROM AUTHOR]