Browsing by Author "Md. Amin Hasan"

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Complementary hydrogen bonding of a carboxylato-barbiturate with urea and acetamide: Experimental and theoretical approach
(2011) Md. Amin Hasan; A. Seshaditya; Stanislav Záliš; Lallan Mishra
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 1H-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, 1H-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. © 2011 Elsevier B.V.
Complexes of Zn(II) containing (o-)/(p-) carboxylato phenyl azo pentane 2,4-dione and 2,2′ bipyridine as ligands: Synthesis, characterization, colorimetric and fluorometric modulation in the presence of Ag+ ions
(Elsevier Ltd, 2013) Md. Amin Hasan; Niraj Kumari; Pankaj Kumar; Brajesh Pathak; Lallan Mishra
Azo-enol based ligands 2-[N′-(1-acetyl-2-oxo-propylidene) hydrazino]-benzoic acid (L1H2) and 4-[N′-(1 acetyl-2 oxo-propylidene)-hydrazino]-benzoic acid (L2H2) and their complexes [Zn(L1H)2(bpy)] (1) and [Zn(L 2H)2(bpy)] (2) (where bpy = 2, 2′-bipyridine) have been synthesized and characterized using elemental analyses, spectral (FT-IR, 1H NMR, 13C NMR, electronic absorption), emission and single-crystal X-ray diffraction studies. Complexes 1 and 2 display selective chromogenic and fluorogenic responses with Ag+ ions in the presence of several other metal ions. The binding is monitored separately using UV-Vis, fluorescence and 1H NMR spectral titrations. Job's plot supports a 1:2 stoichiometry for 1 and 2 with Ag+ ions. The pH dependent "on-off" switching of fluorescence from complexes 1 and 2 have been studied. The fluorescence intensity quenches (turns-off) upon addition of OH- ions, while it enhances (turns-on) in the presence of H + ions. © 2012 Elsevier Ltd. All rights reserved.
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
(Elsevier, 2016) Md. Amin Hasan; Niraj Kumari; Kanhaiya Singh; Kiran Singh; Lallan Mishra
Abstract 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, 1H NMR, 13C 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 87 μM respectively. © 2015 Elsevier B.V.
Reactivity of tetrabutylammonium iodide with a heteronuclear 6Copper(II)-4Na(I) complex: Selective recognition of iodide ion
(2013) Niraj Kumari; Md. Amin Hasan; Benzamin D. Ward; Lallan Mishra
A complex of type [Cu6Na4(μ-O)4(NTA) 2(bpy)6(H2O)4(NO3) 2]·3H2O 1 was allowed to react separately with tetrabutylammonium salts (TBAX), X = F-, Cl-, Br -, I-, AcO-, NO3-, and H2PO4-. The color of complex 1 changed immediately on the addition of TBAI (tetrabutylammonium iodide) only. However, keeping the corresponding solution for 2 months at room temperature, four complexes of compositions [Cu6(μ-OH)4(NTA) 2(bpy)6]2I-·5H2O 2, [Cu 2(bpy)2(OH)2(I)]2(NO 3)2(H2O) 3, [Cu(bpy)2I]I 3- 4, and [Cu(bpy)2I]I·TBAI 5 (bpy = 2,2′-bipyridyl, H3NTA = nitrilotriacetic acid) together with some residues of TBAI and complex 1 were isolated in one-pot synthesis. These complexes were characterized using elemental analysis, spectroscopic (IR, UV-vis) and single crystal X-ray diffraction techniques. Colorimetric response of complex 1 with iodide anions was further supported by the changes in its UV-vis spectra recorded in methanol. The results indicated that 1 exhibits a strong affinity for iodide anions. © 2013 American Chemical Society.