Browsing by Author "Shalini Upadhyay"

Now showing 1 - 9 of 9

4-[2-(1-Acetyl-2-oxopropyl-idene)-hydrazino]-N-(pyrimidin-2-yl) benzene-sulfonamide
(2009) Priyanka Rai; Shalini Upadhyay; M. Nethaji; K.K. Upadhyay
In the title compound, C15H15N5O 4S, the dihedral angle between the pyrimidine and benzene rings is 84.56 (2)°. Intra-molecular hydrazine-carbonyl N - H⋯O and inter-molecular sulfonamide-pyridimine N - H⋯N hydrogen bonds stabilize the mol-ecular and crystal structures, respectively.
Ethyl 3-oxo-2-[(4-sulfamoylphen-yl)hydra-zono]butyrate
(2009) K.K. Upadhyay; Priyanka Rai; Shalini Upadhyay; M. Nethaji
In the title compound, C12H15N3O5S, an intra-molecular N- H⋯O hydrogen bond between the hydrazine unit and one of the carbonyl groups may influence the mol-ecular conformation. In the crystal structure, inter-molecular N- H⋯O hydrogen bonds, including one which is bifurcated, link the mol-ecules into a two-dimensional network.
p-Nitrophenyl triazenyl purine: First adenine-based colorimetric anion sensor
(2008) K.K. Upadhyay; Ajit Kumar; Shalini Upadhyay; Rakesh K. Mishra; P.K. Roychoudhuary
6-[(2E)-3-(4-Nitrophenyl)triaz-2-en-1 -yl]-9H-purine (p-nitrophenyl triazenyl purine, PNTP) has been synthesized and evaluated for sensing the anions PF6-, HSO4-, ClO 4-, and BF4- as their tetrabutylammonium salts in DMSO. This is the first example of any adenine-based anion sensor. The addition of 2 equivalents of PF6- HSO4-, ClO4-, and BF 4- to the 2 × 10-5 mol dm-3 DMSO solution of PNTP at room temperature produced visible color changes and perturbation of UV-vis spectral pattern of PNTP in terms of absorbance at 398 and 575 nm in reciprocal patterns. The sensing ability of PNTP was found to be best for PF6- among all the chosen anions. Copyright © 2008 The Chemical Society of Japan.
Reversible colorimetric switching of thiophene hydrazone based on complementary IMP/INH logic functions
(Royal Society of Chemistry, 2010) K.K. Upadhyay; Ajit Kumar; Rakesh K. Mishra; Thomas M. Fyles; Shalini Upadhyay; Kamlesh Thapliyal
We have synthesized a thiophene hydrazone (receptor 1) that acts as a colorimetric receptor showing a reversible color switching (ON and OFF) function induced by anion and cation recognition. This remarkable color switching is based on two-input complementary IMP/INH logic functions. The (ON and OFF) process of this molecular switch is triggered by an anion (CH 3COO-, C6H5COO-, HCOO-, H2PO4- or F-), while it is quenched by any one MII ion of 3d (d5-d 10) as well as CdII and HgII. A DMSO solution of receptor 1 underwent a bathochromic shift from 407 to 505 nm upon adding any one of the above-mentioned anions, while switch OFF was achieved by the addition of any one of the above-mentioned cations to regenerate a band at 407 nm. © 2010 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Solvent-assisted naked eye sensing of Hg2+ by a chemoreceptor derived from diazocoupling of sulfathiazole with diethyl malonate
(2011) K.K. Upadhyay; Shalini Upadhyay; Ajit Kumar; Kamlesh Thapliyal; Santosh K. Srivastava
2-{[4-(Thiazol-2-ylsulfamoyl)-phenyl]-hydrazono}-malonic acid diethyl ester (R1) and 2-{[4-(5-methyl-isoxazol-3-ylsulfamoyl)-phenyl]-hydrazono}-malonic acid diethyl ester (R2) were synthesized through diazocoupling of sulfathiazole and sulfamethoxazole, respectively, with diethyl malonate. They were characterized through various spectroscopic and mass spectral studies. R2 was also characterized through a single crystal X-ray diffraction (XRD) study. Only R1 selectively recognized Hg2+ from a wide range of metal ions through naked-eye change. A color change from orange to olive green was observed upon addition of 1.0 equivalent of Hg2+ as its chloride salt to the 1×10-3 M DMSO solution of R1. The role of DMSO in the sensing process appears to be the crucial one, because the solvent-assisted band of R1 at 482 nm observed in its UV-Vis spectrum in DMSO did not appear in its spectra recorded in nujol or in a polar aprotic solvent. The UV-Vis and 1H NMR titrations revealed that the formation of six-membered 1:1 chelate between R1 and Hg2+ triggering the desolvation of R1 as the key step towards its sensing activity. The determination of binding stoichiometry between R1 and Hg2+ along with binding constant has also been discussed. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright © Taylor &Francis Group, LLC.
Synthesis, characterization, structural optimization using density functional theory and superoxide ion scavenging activity of some Schiff bases
(2008) K.K. Upadhyay; Ajit Kumar; Shalini Upadhyay; P.C. Mishra
Four Schiff bases, 2-[(4-nitro-phenylimino)-methyl]-phenol (NPIMP-2), 4-[(4-nitro-phenylimino)-methyl]-phenol (NPIMP-4), (1H-indol-3-ylmethylene)-(4-nitro-phenyl)-amine (IYNPA), (3-nitro-benzylidene)-(4-nitro-phenyl)-amine (NBNPA) with experimental clue of binding with superoxide ion have been synthesized by the condensation of p-nitroaniline with o-hydroxy benzaldehyde, p-hydroxybenzaldehyde, indole-3-carboxaldehyde and m-nitrobenzaldehyde respectively. These were characterized by IR, 1H NMR, CHN, mass spectroscopy and UV-visible spectroscopy. The Schiff bases thus synthesized exhibited evidence for their binding with superoxide ion in the form of a high intensity charge transfer band beyond 500 nm in their respective UV-vis spectra on the addition of two drops of N/10 NaOH to their respective 10-2 M solutions in DMSO. On further addition of two drops of N/10 HCl solution, the charge transfer band vanished and the original spectral pattern of the Schiff bases in DMSO was observed. Out of the four Schiff bases, the binding of NPIMP-4 with O2- was observed to be reversible throughout both the cycles of measurements, but the remaining Schiff bases, namely NPIMP-2, IYNPA and NBNPA were found to show reversibility in only one cycle. The variable temperature 1H NMR (RT-175 °C) in DMSO-d6 revealed reversible intramolecular proton transfer in NPIMP-2 and NPIMP-4 leading to existence of several tautomeric structures. Besides these synthetic and spectroscopic studies, the density functional theory (DFT) calculations were performed for two Schiff bases i.e., NPIMP-2 and NPIMP-4. These calculations provided some important information about the relative stability of various tautomeric forms of NPIMP-2 and NPIMP-4. © 2007 Elsevier B.V. All rights reserved.
Synthesis, crystal structures and studies on Hg2+ sensing by the diazo derivatives of sulfathiazole and sulfamethoxazole
(Taylor and Francis Ltd., 2012) K.K. Upadhyay; Shalini Upadhyay; Ajit Kumar; Kamlesh Thapliyal
Diazocoupling of sulfathiazole and sulfamethoxazole with 2,4-pentanedione led to the syntheses of compounds R1 and R2. These were fully characterized by single crystal X-ray diffraction studies in conjunction with UV-visible, IR, 1H NMR, and mass spectral studies. Both the compounds were further screened for their possible use in metal ion recognition. Interestingly, compound R1 showed a selective naked-eye response for Hg2+, while R2 did not give a color change for any metal ions. These results can be understood in terms of a solvent-assisted low-energy absorption band in R1 that disappeared upon interaction with Hg2+. This absorption band was not observed in the case of compound R2 that consequently failed to show any naked-eye color change in the presence of metal ions. © 2012 Taylor and Francis Group.
Synthetic and spectroscopic studies of some new 2-[1-aryl-4{4- methoxyphenyl}-6-thioxo-1,6-dihydro-1,3,5-triazinyl]amino/hydrazonothiazolidin- 4-ones
(2008) P.K. Roychowdhuary; K.K. Upadhay; Rakesh K. Mishra; Ajit Kumar; Sangeeta Mehrotra; Sugandh Srivastava; Shalini Upadhyay
(Chemical Equation Presented) A series of 4-thiazolidinones having triazinethione moieties have been synthesized by the systematic chemical modification of S-benzylmercapto-1-aryl-4-(4-methoxyphenyl)-1,6-dihydro-1,3,5- triazine-6-thione.
X-ray crystallographic study of 3-Oxo-2-{[4-(thiazol-2-ylsulfamoyl)-phenyl]-hydrazono}-butyric acid ethyl ester and its application in the solvent assisted naked eye sensing of Hg(II)
(2009) K.K. Upadhyay; Shalini Upadhyay; Kamlesh Kumar; Rajendra Prasad
The 3-Oxo-2-{[4-(thiazol-2-ylsulfamoyl)-phenyl]-hydrazono}-butyric acid ethyl ester (OSPBE) was studied through single crystal structure analysis revealing some interesting supramolecular architectural patterns. The N(3)-N(4) bond length of OSPBE was found to be 1.36 Å matching well with reported N-N bond length in the literature and hence clearly proved that it is the keto form of OSPBE which is stable. Full structural optimization of OSPBE using density functional theory (DFT) at the HCTH407/6-31G** level also proved that the keto form of OSPBE is stable. The UV-Vis absorption peaks for OSPBE predicted by the time dependent DFT at B3LYP/6-311G** level matched quite well with the experimentally observed UV-Vis bands for OSPBE. The OSPBE was successfully tested as the naked eye sensor for Hg(II) as its chloride salt at the millimolar level in dimethylsulfoxide. A color change from red orange to olive green was observed on addition of 1.0 equiv. of Hg(II) to the 1.0 × 10-3 M DMSO solution of the chemosensor. The role of DMSO in the sensing process appears to be the crucial one because the intramolecular charge transfer (ICT) band of OSPBE in DMSO observed at 489 nm did not appear in the UV-Vis spectrum of OSPBE in nujol. The UV-Vis and 1H NMR titrations revealed that formation of six membered 1:1 chelate between OSPBE and Hg(II) along with reversible supramolecular association of DMSO with NH at N-2 position in OSPBE may be responsible for its Hg(II) sensing. No sensing for other d10 metal ions like Zn(II) and Cd(II) were observed with OSPBE under similar conditions. Besides DMSO, some other polar aprotic solvents like DMF and acetone having X{double bond, long}O (where X = C) also produced similar type of color change on the addition of 1.0 equiv. of Hg(II) to their respective 1.0 × 10-3 M OSPBE solutions. Nevertheless, polar aprotic solvent like acetonitrile not having X{double bond, long}O or non-polar aprotic solvent like chloroform no color change was observed under similar conditions. © 2009 Elsevier B.V. All rights reserved.