Browsing by Author "P.K. Roychowdhury"

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A water compatible turn 'on' optical probe for Cu2+ based on a fluorescein-sugar conjugate
(2014) Uzra Diwan; Ajit Kumar; Virendra Kumar; K.K. Upadhyay; P.K. Roychowdhury
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.
Inculcating total selectivity for fluoride in pyrene based chromogenic receptors: An experimental and theoretical study
(2013) Ajit Kumar; Virendra Kumar; Neeraj; K.K. Upadhyay; P.K. Roychowdhury
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.
Synthesis of 1-aryl-2-mercapto-4-aryl-1,6-dihydro-1,3,5-triazine-6-thione and their latentiation products as antithyroidal agent
(1995) S. Mehrotra; P.K. Roychowdhury; K.K. Pandey; P.K. Srivastava
Two new 1-aryl-2-benzylmercapto-4-aryl-1,6-dihydro-1,3,5-triazine-6-thiones have been synthesized by known methods (Goerdeler et al., 1967). These triazines on treatment with thiourea as dealkylating agent, in acidic medium afforded the corresponding 1-aryl-2-mercapto-4-aryl-1,6-dihydro-1,3,5-triazine-6-thione whch on further reaction with different α, β-unsaturated carbonyl compounds and aryl-cyanamide hydrochloride afforded the related adducts. Some of these compounds show appreciable antithyroidal activity. © 1995 The Pharmaceutical Society of Korea.
Synthesis of some new 1,3,5-triazinyl barbiturates
(2003) P.K. Roychowdhury; Sangeeta Mehrotra; Sugandh Srivastava; P.K. Srivastava
N-Aryl-N′-aryltriazinyl carbamides 3a-d were prepared by treating aminotriazines 2a-d with aryl isocyanates. 3a-d on being heated with malonic acid in the presence of acetyl chloride furnished desired 1,3,5-triazinylbarbiturates (4a-h).