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A potentially tetradentate NOOO donor hydrazone ligand, LH2(condensation product of benzhydrazide with O-vanillin) generates a tetranuclear CuIIcomplex [Cu4(L)4]·4H2O (1), whose void spaces are occupied by water tetramers presenting a ‘butterfly' conformation with the highest dihedral angle reported to date, as revealed by its X-ray crystal structure. 1 has also been characterized using various spectroscopic techniques, including IR, UV-vis, and elemental analysis. Variable temperature magnetic susceptibility measurements reveal the presence of moderate antiferromagnetic intra-tetramer coupling between the four CuIIcentres connected through simple oxo groups of the hydrazone ligand with two different coupling constants (J1= –61.7(3) cm-1and J2= –92(1) cm-1) corresponding to the two different CuIItetramers identified in the X-ray structure. We also report a quantum chemical study (MP2(full)/6–311+G(3df,2p)//B3LYP/6–311+G(3df,2p)) to calculate the stability of the water tetramers. [ABSTRACT FROM AUTHOR]

Syntheses and crystal structures of four new hydrazone-based Cu(ii) complexes, [{Cu(L1)(H2O)}2(μ-pyraz)](ClO4)2(1), [{Cu(L1)(OClO3)}2(μ-4,4′-bipy)] (2), [{Cu(L2H)}(μ-pyraz){Cu(L2H)(OClO3)}].(ClO4) (3) and [{Cu(L2)}2(μ-bpe)] (4) [L1H = condensation product of benzhydrazide and pyridine-2-carbaldehyde and L2H2= condensation product of benzoyl acetone and benzhydrazide], bridged by various organic spacers [pyrazine (pyraz), 4,4′-bipyridine (4,4′-bipy) and 1,2-di(4-pyridyl)ethane (bpe)] are reported in this paper. The single-crystal X-ray crystallographic studies reveal that all are dinuclear units where 1and 3form strong intermolecular H-bonding to form sheets of interconnected ions, whereas 2forms sheets of dinuclear chains through π–π interactions; in 4, molecules are linked only through van der Waals interactions. The variable-temperature magnetic moment studies reveal that 1and 3show antiferromagnetic coupling between the Cu(ii) centers at lower temperatures. The binding ability of 1with calf thymus DNA [CT-DNA] is reported using various spectroscopic studies (UV-Vis titration, circular dichroism and fluorescence). The binding constants of 1with CT-DNA, as calculated by different methodologies, are of the order of 105M−1. The mode of interaction between 1and CT-DNA has been predicted using circular dichroic (CD) spectroscopy, where it has been shown that 1most probably interacts with DNA viaintercalation between the base pairs leading to a change in B-DNA conformation. 1is also able to cleave supercoiled (SC) plasmid DNA pUC19 in a time and dose dependent manner as demonstrated by agarose gel electrophoresis, and also demonstrates its potential to cleave the SC plasmid DNA viaboth oxidative and hydrolytic mechanisms. Approximately 50% of leukemic cells are found to be dead when two representative leukemic cell lines are exposed to 1(∼80 μM) even for 24 h as determined by different cell cytotoxicity assays. Preliminary results also showed that, at 20 μM, 1could selectively induce apoptosis in leukemic cells without affecting normal lymphocytes. [ABSTRACT FROM AUTHOR]

Abstract  A nickel(II) and a cobalt(III) complex of two different potentially tetradentate Schiff bases with different binding modes have been synthesised. The nickel(II) complex [NiL1] · CH3OH (1) was formed, on reacting the metal salt with a perfectly symmetrical N2O2 tetradentate Schiff base ligand H 2 L 1 , which is the 1:2 condensation product of 1,3-diamino propane and 2-hydroxyacetophenone. The cobalt(III) complex [Co(HL2)3] · (ClO4)3 · H2O (2) was synthesised using an asymmetric N2O2 tetradentate Schiff base ligand HL 2 on condensing N,N-dimethyl-1,3-diamino propane with o-vanillin in 1:1 mmol ratio. Although both Schiff bases are N2O2 functionalised, they showed variation in their coordinative property with nickel(II) and cobalt(III) ions. Both the complexes were characterised by IR spectroscopy and cyclic voltammetry and their single crystal structures clearly indicate that 1 is a mononuclear species whereas 2 is a hydrogen-bonded dimer. [ABSTRACT FROM AUTHOR]

Abstract  Three new coordination complexes of Zn(II) and Mn(II) have been synthesised using two different tridentate N,N,O donor hydrazone ligands, Hpbh and Hacpbh respectively. The complexes [Zn(pbh)2] (1) and [Zn(acpbh)2] (2) have been synthesized by the treatment of ZnSO4 · 7H2O with Hpbh and Hacpbh hydrazone ligands, respectively. The Mn(II) complex [Mn(acpbh)2] (3) was obtained on reacting Mn(NO3)2 · 4H2O with the ligand Hacpbh. The ligands Hpbh and Hacpbh were prepared by condensing pyridine-2-carboxaldehyde and 2-acetylpyridine with benzhydrazide respectively. Inspite of varying the carbonyl functionality attached to the pyridine moiety present in the hydrazone ligands in both the Schiff bases, we obtained three mononuclear complexes 1, 2, and 3 which were clearly characterized from single crystal X-ray diffraction studies. Spectroscopic investigations like IR and UV/Vis have been carried out for 1, 2, and 3. Fluorescence studies have been performed for 1 and 2. For 3 cyclic voltammetry, room temperature magnetic study and EPR measurements have been recorded. [ABSTRACT FROM AUTHOR]

The aerial oxidation of cobalt(ii) salt, in a methanolic solution, containing a hydrazone ligand, (E)-N′-(4-oxo-4-phenylbutan-2-ylidene)benzohydrazide (condensation product of benzoyl acetone and benzhydrazide, LH2) leads to the coupling of two such ligand units through the formation of a rather long C–C bond [1.601(6) Å] giving rise to a dinuclear Co (iii) hydrazone complex, [Co2(L)2(L′)2]·0.25H2O (L′ = C–C coupled hydrazone ligand). The structure of the complex has been determined by X-ray crystallography and IR, UV-Vis spectroscopy and elemental analysis have characterized the complex. [ABSTRACT FROM AUTHOR]