Mixed ligand complexes of Cu(II)/Zn(II) ions containing (m-)/(p-) carboxylato phenyl azo pentane 2,4-dione and 2,2'-bipyridine/1,10 phenanthroline: Synthesis, characterization, DNA binding, nuclease and topoisomerase I inhibitory activity.

Metal complexes of type [Cu(L1H)2(bpy)] (1), [Zn(L1H)2(bpy)] (2), [Cu(L2H)2(bpy)] (3) and [Cu(L2H)2(Phen)] (4) (L1H2=3-[N'-(1-acetyl-2-oxo-propylidene)-hydrazino]-benzoic acid, L2H2=4-[N'-(1-acetyl-2-oxo-propylidene)-hydrazino]-benzoic acid, bpy=2,2'-bipyridine, Phen=1,10 phenanthroline) are synthesized and characterized using spectroscopic techniques (FT-IR, (1)H NMR, (13)C NMR, electronic absorption and emission) and elemental analysis data. The assembly of the complexes involving intramolecular H-bonding is displayed using corresponding crystal structure. Binding of the complexes separately with Calf Thymus DNA is monitored using UV-vis spectral titrations. The displacement of ethidium bromide (EB) bound to DNA by the complexes, in phosphate buffer solution (pH∼7.2) is monitored using fluorescence spectral titrations. Nuclease activity of the complexes follow the order 4>3>1>2. The gel electrophoretic mobility assay measurement in presence of minor groove binder 4',6-diamidino-2-phenylindole (DAPI), suggests that complexes preferably bind with the minor groove of DNA. Topoisomerase I inhibitory activity of the complexes 3 and 4 inhibit topoisomerase I activity with IC50 values of 112 and 87µM respectively.

Complementary hydrogen bonding of a carboxylato-barbiturate with urea and acetamide: experimental and theoretical approach.

A barbiturate derivative, 4-(2,4,6-trioxo-tetrahydro-pyrimidine-5-ylidenemethyl)-benzoic acid (L1) possessing functional complementarity to amides has been synthesized and characterized. Its binding separately with urea and acetamide was monitored using UV-vis, fluorescence and (1)H-NMR spectroscopic titrations. Experiments suggested stronger binding of L1 with urea as compared to acetamide. The solid adducts of L1 prepared separately with urea and acetamide were also characterized using IR, (1)H-NMR spectral and PXRD techniques. Theoretical studies on hydrogen bonded complexes of L1-urea and L1-acetamide in the gas phase, aqueous, and DMSO medium were carried out using density functional theory (DFT) at the B3LYP/6-31G** level. The theoretical calculations agreed to the experimental results.