Browsing by Author "Singh, Vinod Prasad"
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PublicationArticle A binuclear Cu(i) complex as a novel catalyst towards the direct synthesis of N-2-aryl-substituted-1,2,3-triazoles from chalcones(Royal Society of Chemistry, 2016) Singh, Divya Pratap; Allam, Bharat Kumar; Singh, Rahul; Singh, Krishna Nand; Singh, Vinod PrasadA binuclear Cu(i) complex containing a N′,N′-bis{(1H-indol-3-yl)methylene}oxalohydrazide (H2bioh) ligand has been synthesized and characterized. The molecular structures of the synthesized compounds have been determined by single crystal X-ray diffraction. The crystal structures are stabilized by inter- and intra-molecular π-π stacking and C-H⋯π interactions. The Cu(i)-complex has successfully been employed as an efficient catalyst for one-pot operation involving the azide-chalcone click reaction and subsequent arylation has been developed. The complex exhibits excellent catalytic activity with significantly low catalyst loading. The overall process is insensitive to air and moisture and can be manipulated under ambient temperature with operational ease. © 2016 The Royal Society of Chemistry.PublicationArticle A binuclear Mn(ii) complex as an efficient catalyst for transamidation of carboxamides with amines(2014) Singh, Divya Pratap; Allam, Bharat Kumar; Singh, Krishna Nand; Singh, Vinod PrasadA binuclear Mn(ii) complex has been synthesized and characterized by different structural methods. The complex contains two unique oxo-bridged metal centres and has been explored as an excellent catalyst for transamidation of carboxamides with amines under solvent-free conditions. © 2014 The Royal Society of Chemistry.PublicationArticle A dihydrazone based “turn–on” fluorescent probe for selective determination of Al3+ ions in aqueous ethanol(Elsevier B.V., 2017) Singh, Divya Pratap; Dwivedi, Romi; Singh, Ashish Kumar; Koch, Biplob; Singh, Priya; Singh, Vinod PrasadAn efficient and highly selective dihydrazone based fluorescent probe N′,N′–bis((2–hydroxynaphthalen–1–yl)methylene)malonohydrazide (H2nmh), has been synthesized for selective detection of Al3+ ions and characterized by different physico–chemical and spectroscopic techniques. The probe shows an enhanced fluorescence in the presence of Al3+ ions in ethanol–water (2:3 v/v) solution which is not observed in the presence of other cations (Na+, K+, Mg2+, Ca2+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+ and Hg2+). The binding modes of H2nmh with Al3+ were studied by UV–vis, fluorescence and 1H NMR titrations. The probe act as dibasic hexa–dentate ligand and interacts with two Al3+ ions with a binding constant KB = 5.74 × 109 M−1 and detection limit 5.78 × 10−8 M. Detailed insights of probe–metal interaction mechanism were studied by mean of density functional theory (DFT) as well as time dependent–DFT calculation. MTT assay on live MCF–7 cells has been performed to evaluate the cytotoxicity of the probe which suggests viability of the probe to MCF–7 cells even at higher concentration (100 μM) with no serious cytotoxicity in cells. Live cell imaging study clearly indicates that the accumulation of Al3+ in the cytoplasm of cells can be detected by H2nmh. © 2016 Elsevier B.V.PublicationArticle Aroyl hydrazone with large Stokes shift as a fluorescent probe for detection of Cu2+ in pure aqueous medium and in vivo studies(Elsevier B.V., 2020) Dwivedi, Romi; Singh, Saumya; Chauhan, Brijesh Singh; Srikrishna, S.; Panday, Anoop Kumar; Choudhury, Lokman H.; Singh, Vinod PrasadAn aroyl hydrazone based fluorescent probe, hpsh, has been developed for the selective detection of Cu2+ ions in pure aqueous medium by static fluorescence quenching. The fluorescence quenching of hpsh in the presence of Cu2+ takes place as a result of ground state complex formation through intramolecular charge transfer (ICT). Addition of Cu2+ ions changes the color of the solution from colorless to yellow-green which is clearly visible by naked eye. Large Stokes shift of hpsh prevents the self-quenching of the probe in absence of metal ions. The observed stoichiometry between Cu2+ and probe has been found as 1:2 (M: L). MTT assay of hpsh on fruit flies confirms that the probe is non-toxic and biocompatible. The plausible in vivo bioimaging application of the probe to detect Cu2+ in Drosophila gut tissues as well as in adult fruit fly has been investigated with excellent results. © 2020 Elsevier B.V.PublicationArticle Binuclear Cu(I) complex of (N′1E,N′2E)-N′1,N′2-bis(phenyl(pyridin-2-yl)methylene)oxalohydrazide: Synthesis, crystal structure and catalytic activity for the synthesis of 1,2,3-triazoles(Elsevier, 2015) Singh, Divya Pratap; Allam, Bharat Kumar; Singh, Krishna Nand; Singh, Vinod PrasadA new binuclear 5-coordinate distorted trigonal bipyramidal Cu(I) complex with (N′1E,N′2E)-N′1,N′2-bis(phenyl(pyridin-2-yl) methylene) oxalohydrazide (H2bpoh) has been synthesized, and characterized by spectroscopic and single crystal X-ray diffraction techniques. In the complex, H2bpoh acts as a dibasic hexadentate ligand bonding with two Cu(I) each through a carbonylate-O, azomethine-N, and pyridyl-N atoms. The complex possess a CuN2OP2 core with a considerable delocalization of charge on the five-membered chelate rings which forms an unusual intra-molecular π-π stacking and CH⋯π interactions. The synthesized complex exhibits excellent catalytic efficiency for a click reaction at room temperature. © 2014 Elsevier B.V. All rights reserved.PublicationArticle Intracellular application and logic gate behavior of a ‘turn off-on-off’ type probe for selective detection of Al3+ and F− ions in pure aqueous medium(Elsevier B.V., 2018) Dwivedi, Romi; Singh, Divya Pratap; Chauhan, Brijesh Singh; Srikrishna, S.; Panday, Anoop Kumar; Choudhury, Lokman H.; Singh, Vinod PrasadA new Schiff base tcph, derived from 2-thiophene carboxylic acid hydrazide, has been synthesized and characterized by various spectroscopic techniques. The molecular structure of the compound has also been determined by X-ray crystallography. The tcph acts as a selective Al3+ and F− induced OFF-ON-OFF type of probe in aqueous media. The 1:1 binding stoichiometry between probe and Al3+ has been established from Job's plot and further supported by ESI–MS studies. The limit of detection of Al3+ ions is determined by 3σ methods, which is found to be 1.35 × 10−9 M. The coordination environment for the tcph-Al3+ complex is delineated by NMR titration and DFT calculations. Detailed insights of probe–metal interaction mechanism have been studied by density functional theory (DFT) as well as time dependent–DFT calculations. MTT assay of the probe on live SiHa cells suggests no serious cytotoxicity in cells even at higher concentration. The probe tcph and its tcph-Al3+ complex have also been successfully applied to detect Al3+ and F− ions in living cells (SiHa cells), respectively. © 2017 Elsevier B.V.PublicationArticle Synthesis, spectral characterization and antimicrobial activity of some transition metal(II) complexes with acetone p-amino acetophenone benzoylhydrazone(2008) Singh, Vinod Prasad; Katiyar, AnshuComplexes of the type [M(apabh)Cl] and [M(Hapabh)(H2O)SO4], where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hapabh = acetone p-amino acetophenone benzoylhydrazone have been synthesized and characterized. Electronic spectra and μeff values suggest a square planar geometry for Co(II), Ni(II) and Cu(II) chloride complexes, whereas, octahedral geometry for the sulfato complexes. ESR data show isotropic spectra for [Cu(apabh)Cl] and axial spectra for [Cu(Hapabh)(H2O)SO4] and dx2-y2 as the ground state for both Cu(II) complexes. The ligand acts as tridentate monobasic in all chloro complexes bonding through two >C{double bond, long}N{single bond} and a deprotonated enolate groups, whereas tridentate neutral in all sulfato complexes coordinating through two >C{double bond, long}N{single bond} and a >C{double bond, long}O groups. Thermal analysis (TGA & DTA) of [Ni(apabh)Cl] complex shows a multi-step exothermic decomposition pattern. The complexes show a significant antifungal activity against Rizoctonia sp., Aspergillus sp. and Penicillium sp. and a considerably fair antibacterial activity against Pseudomonas sp. and Clostridium sp. The activity increases at higher concentration of the compound. © 2008 Elsevier Inc. All rights reserved.PublicationArticle Synthesis, thermal studies and spectral characterization of Co(II), Ni(II), Cu(II), and Zn(II) complexes with some polymeric diacetyl acyldihydrazone ligands(2013) Singh, Vinod Prasad; Singh, Divya PratapTwo polymeric ligands, diacetyl oxaloyldihydrazone (DODH), diacetyl malonoylhydrazone (DMDH) and their Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized and characterized by elemental analyses, IR, mass, 1H & 13C NMR, ESR and electronic spectral studies. The ligands and their complexes are highly insoluble in water and common organic solvents and decompose at high temperature. The metal atoms are embedded between two polymeric chains of the organic ligands and the monomeric unit of the polymeric chain behaves as a neutral bidentate ligand and coordinate through two >C=N groups to different metals as indicated by 1H & 13C NMR and IR spectral studies. The molecular weights determined by 1H NMR and mass spectral studies suggest oligomeric nature of the ligands and their Zn(II) complexes. The magnetic susceptibility measurements and electronic spectral studies indicate a square planar geometry around the metal ion in Co(II) and Ni(II) complexes. Electronic and ESR spectral studies for Cu(II) complexes suggest a distorted octahedral stereochemistry around the metal atom and 2B1g as the ground state. Thermal studies (TGA and DTA) of some of the complexes in inert atmosphere show a multi-step exothermic decomposition of the bonded organic ligand at high temperature and metal (II) chloride as the end product. © 2013 The Polymer Society of Korea and Springer Sciene+Business Media Dordrecht.ItemProject Report Transition metal complexes with Heterocyclic Schiff bases: synthesis, characterization and applications(Department of Chemistry, 2017-01-31) Singh, Vinod PrasadThe aim of this work is to explore the ligational behavior of some heterocyclic Schiff bases derived from acylhydrazine system towards some transition metal ions and to arrive at the probable structures of the coordination complexes on the basis of spectroscopic studies. By carefully selecting the organic ligand one also aims to tune the physical properties and thus realizes various applications such as catalysis, electrical conductivity, luminescence, chemo sensing and anticorrosion behavior. Schiff bases are one of the most important and widely explored organic species. Their low-cost, synthetic ease and tremendous applications, inspired us to work on Schiff bases as chemical probes for selective detection of toxic metal ions.
