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Issue 34, 2009
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Four new dinuclear Cu(ii) hydrazone complexes using various organic spacers: syntheses, crystal structures, DNA binding and cleavage studies and selective cell inhibitory effect towards leukemic and normal lymphocytes

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Abstract

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 1 and 3 form strong intermolecular H-bonding to form sheets of interconnected ions, whereas 2 forms 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 1 and 3 show antiferromagnetic coupling between the Cu(II) centers at lower temperatures. The binding ability of 1 with calf thymus DNA [CT-DNA] is reported using various spectroscopic studies (UV-Vis titration, circular dichroism and fluorescence). The binding constants of 1 with CT-DNA, as calculated by different methodologies, are of the order of 105 M−1. The mode of interaction between 1 and CT-DNA has been predicted using circular dichroic (CD) spectroscopy, where it has been shown that 1 most probably interacts with DNA via intercalation between the base pairs leading to a change in B-DNA conformation. 1 is 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 via both 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, 1 could selectively induce apoptosis in leukemic cells without affecting normal lymphocytes.

Graphical abstract: Four new dinuclear Cu(ii) hydrazone complexes using various organic spacers: syntheses, crystal structures, DNA binding and cleavage studies and selective cell inhibitory effect towards leukemic and normal lymphocytes

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Supplementary files

Article information


Submitted
13 Feb 2009
Accepted
04 Jun 2009
First published
21 Jul 2009

Dalton Trans., 2009, 6849-6860
Article type
Paper

Four new dinuclear Cu(II) hydrazone complexes using various organic spacers: syntheses, crystal structures, DNA binding and cleavage studies and selective cell inhibitory effect towards leukemic and normal lymphocytes

S. Banerjee, S. Mondal, S. Sen, S. Das, D. L. Hughes, C. Rizzoli, C. Desplanches, C. Mandal and S. Mitra, Dalton Trans., 2009, 6849
DOI: 10.1039/B903072G

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