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Mishra R.K.,Banaras Hindu University | Kumar V.,Banaras Hindu University | Diwan U.,Banaras Hindu University | Upadhyay K.K.,Banaras Hindu University | Roy Chowdhury P.K.,Chembiotek Research International
Journal of Molecular Structure | Year: 2012

The stepwise substitution of appropriate groups over the 3-[(2,4-dinitro-phenyl)-hydrazono]-butyric acid ethyl ester (R3) lead receptor R1 which showed selectivity towards fluoride in DMSO. The UV-vis and 1H NMR titration studies revealed the details of the binding between receptor R1 and fluoride. The receptor R1 also recognized fluoride in a toothpaste solution to as low as 50 ppm. The theoretical simulations of recognition event at Density Functional Theory (DFT) level using B3LYP/6-31G basis set and polarizable continuum model (PCM) approach lead a semi-quantitative match with the experimental results. © 2012 Elsevier B.V. All rights reserved.


Kumar A.,Banaras Hindu University | Kumar V.,Banaras Hindu University | Neeraj,Banaras Hindu University | Upadhyay K.K.,Banaras Hindu University | Roychowdhury P.K.,Chembiotek Research International
Journal of Molecular Structure | Year: 2013

Three simple Schiff base receptors 1-3 containing pyrene skeletons have been designed and synthesized. The intramolecular hydrogen bonding between aldimine N-atom and phenolic OH of these Schiff bases were found to play a crucial role towards their sensing behavior against fluoride. The receptor 3 exhibited total selectivity towards fluoride in acetonitrile. The basis of the above designing at the molecular orbital level was studied through density functional theory (DFT) and time dependent density functional theory (TD-DFT). The observed structure dependence of the binding selectivity may provide guidelines for the development of new colorimetric/fluorescent sensors for F- of further high selectivity. © 2012 Elsevier B.V. All rights reserved.


Tripathi R.C.,Banaras Hindu University | Pandey M.B.,Purvanchal University | Pandey M.B.,Chembiotek Research International | Singh S.,Banaras Hindu University | Pandey V.B.,Banaras Hindu University
Journal of the Indian Chemical Society | Year: 2010

5,7-Dihydroxyflavone, apigenin, kaempferol and quercetin has been isolated from aerial parts of Melochia corchorifolia and their structures established by spectral evidences. These flavonoids exhibited significant antifungal activity. This is the first report of these flavonoids in M. corchorifolia and their antifungal activity.


Upadhyay K.K.,Banaras Hindu University | Mishra R.K.,Banaras Hindu University | Kumar V.,Banaras Hindu University | Chowdhury P.K.R.,Chembiotek Research International
Talanta | Year: 2010

A new coumarin based hydrazone (receptor 1) synthesized by modifying one of our earlier reported receptor detected fluoride ion selectively through naked eye in aq. DMSO (5:95, v/v). It was also able to detect fluoride through naked eye in a toothpaste sample. The addition of 1 equiv. of fluoride as its tetrabutylammonium salt to the 5 × 10-5 M aq. DMSO solution of the receptor 1 produced red color while the similar addition of acetate produced faint pink color. The dihydrogenphosphate and a variety of other anions were not able to produce any significant color change with receptor 1 under similar experimental conditions. The corresponding UV-vis measurements showed a bathochromic shifting of 455 nm band of receptor 1 to 514 and 484 nm for fluoride and acetate, respectively. The non-linear fittings of corresponding UV-vis titration data in 1:1 binding equation yielded association constants in 105:1 ratio for fluoride and acetate, respectively. The 1H NMR titrations studies shade further light on their mode of binding with receptor 1. The quantum mechanical calculations through time dependant density functional theory (TD-DFT) using basis set b3lyp/6-311g** supported our experimental findings nicely. © 2010 Elsevier B.V. All rights reserved.


Diwan U.,Banaras Hindu University | Kumar A.,Banaras Hindu University | Kumar V.,Banaras Hindu University | Upadhyay K.K.,Banaras Hindu University | Roychowdhury P.K.,Chembiotek Research International
Sensors and Actuators, B: Chemical | Year: 2014

A fluorescein-sugar conjugated chromo-fluorogenic turn 'on' probe (FG) has been synthesized for detection of Cu2+. The FG comprises of fluorescein as an efficient fluorophore and a sugar moiety, viz., galactose as the binding unit. The inclusion of galactose into FG led towards its good water compatibility. When Cu2+ was added in 70% aqueous HEPES buffered solution (pH 7.4) of FG, the absorbance and the fluorescence spectral pattern of the same were modulated dramatically with observation of absorption and emission bands at 632 and 515 nm, respectively. The detection limit from fluorescence titration was calculated as 6.32 nM which further establishes high sensitivity of FG towards Cu2+. The spectral studies for the interaction of FG with Cu2+ indicated towards metal ion triggered spirolactam ring opening of FG as the mechanistic pathway of the sensing phenomenon. © 2014 Elsevier B.V. All rights reserved.

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