Browsing by Author "Divya Pratap Singh"

Now showing 1 - 13 of 13

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) Divya Pratap Singh; Bharat Kumar Allam; Rahul Singh; Krishna Nand Singh; Vinod Prasad Singh
A 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.
A binuclear Mn(ii) complex as an efficient catalyst for transamidation of carboxamides with amines
(2014) Divya Pratap Singh; Bharat Kumar Allam; Krishna Nand Singh; Vinod Prasad Singh
A 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.
A dihydrazone based “turn–on” fluorescent probe for selective determination of Al3+ ions in aqueous ethanol
(Elsevier B.V., 2017) Divya Pratap Singh; Romi Dwivedi; Ashish Kumar Singh; Biplob Koch; Priya Singh; Vinod Prasad Singh
An 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.
A dihydrazone based fluorescent probe for selective determination of Al3+ ions
(Elsevier, 2014) Divya Pratap Singh; Vinod P. Singh
A highly selective fluorescent sensor N,N′-bis((2-hydroxynaphthalen- 1-yl)methylene) oxalohydrazide (H2ohn) for the determination of Al3+ ions was synthesized and characterized by different physico-chemical and spectroscopic techniques. The single crystal structure of H2ohn receptor has also been reported. The H2ohn shows an enhanced fluorescence in the presence of Al3+ ions in ethanol-water (2:3 v/v) solution. Other cations viz. Na+, K+, Mg 2+, Ca2+, Mn2+, Fe3+, Co 2+, Ni2+, Cu2+, Zn2+, Pb 2+, Cd2+ and Hg2+ show no appreciable change in fluorescence intensity. The binding mode of H2ohn receptor with Al3+ was studied by UV-visible, fluorescence and 1H NMR titrations. The receptor acts as a dibasic hexadentate ligand and interacts with two Al3+ ions with a high binding constant KB=2. 62×1011 M-2. The lowest detection limit for Al 3+ complex of H2ohn was determined to be 8.56×10-10 M. The structures of H2ohn and its Al(III) complex were also optimized by DFT calculations. © 2014 Elsevier B.V. All rights reserved.
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) Divya Pratap Singh; Bharat Kumar Allam; Krishna Nand Singh; Vinod Prasad Singh
A 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.
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) Romi Dwivedi; Divya Pratap Singh; Brijesh Singh Chauhan; S. Srikrishna; Anoop Kumar Panday; Lokman H. Choudhury; Vinod Prasad Singh
A 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.
Lanthanide based double perovskites: Bifunctional catalysts for oxygen evolution/reduction reactions
(Elsevier Ltd, 2021) Sachin Kumar; Monika Singh; Raj Pal; Uday Pratap Azad; Ashish Kumar Singh; Divya Pratap Singh; Vellaichamy Ganesan; Akhilesh Kumar Singh; Rajiv Prakash
In this work, we are reporting the facile synthesis of double perovskite oxide materials LnBa0.5Sr0·5Co1·5Fe0·5O6 (LnBSCF, Ln = Pr, Nd, Sm, and Gd) using citrate-nitrate based sol-gel method. These double perovskite oxide materials exhibit bifunctional catalytic activity for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The phase formation and structure of the prepared oxides have been determined by powder X-ray diffraction, SEM analysis. Presence of various phases is analyzed and quantified by mean of Le-Bail refinement of XRD profiles. SEM analyses confirm the morphology and composition of prepared catalysts. Electrochemical measurements, e.g. Linear Sweep Voltammetry, Cyclic Voltammetry and Electrochemical Impedance spectroscopy were used to study catalytic performance of prepared catalyst towards both oxygen evolution and oxidation reduction reactions in alkaline solution. Better catalytic performance was obtained in case of double perovskites as compared to parent perovskite for both reactions. Best catalytic performance was observed for Gd based double perovskite. © 2021 Hydrogen Energy Publications LLC
Lanthanum-based double perovskite oxides as cobalt-free catalyst for bifunctional application in electrocatalytic oxygen reactions
(Elsevier Ltd, 2024) Divya Pratap Singh; Sanjukta Mukherjee; Sweta Bhagat; Nandita Singh; Monika Singh; Akhilesh Kumar Singh; Ashish Kumar Singh; Uday Pratap Azad; Suryabhan Singh; Lalrintluangi; Ved Prakash Singh
Electrochemical water splitting by use of suitable electrocatalysts is an important process to establish water as sustainable energy material. Similarly, the Oxygen reduction reaction is an important step involved in fuel cells. Hence, suitable catalysts are required for low-cost and high-performance activity towards both processes. In this work, we synthesized Cobalt-free Lanthanum-based double Perovskites oxides La0.5Sr0.5Fe0.8Cu0.2O3 and La0.5Sr0.5Fe0.8Zn0.2O3 by sol-gel method followed by calcination at different temperatures (800 °C, 900 °C and 1000 °C). Prepared double Perovskite oxide materials exhibit bifunctional catalytic activity towards both oxygen evolution reaction and oxygen reduction reaction. Calcination temperatures and composition have a significant impact on catalytic performance because of morphological control along with tuning of surface composition. Powder X-ray diffraction study has been performed to characterize the materials and phases/composition of materials was further analyzed by Rietveld refinement. The morphology of the best catalyst was analyzed by SEM, EDS mapping and XPS analysis. The catalytic performances of the catalysts were examined using electrochemical methods such as linear sweep voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy in 0.1 M KOH solution. Preparation of noble-metal/cobalt-free catalysts is important finding towards establishing water as potential source for hydrogen production. © 2023 Hydrogen Energy Publications LLC
Nanotechnology applications in pandemic prediction
(Elsevier, 2025) Nandita Singh; Kalyani Dewangan; Jitendra Sahu; Uday Pratap Azad; Divyanshu Singh; Sweta Bhagat; Ashish Kumar Singh; Suryabhan Singh; Sunil Kumar Singh; Ananya Srivastava; Divya Pratap Singh
The necessity for novel ways utilizing nanotechnology in antiviral tactics is demonstrated by the continuous fight against viral infections, which has been brought to light by the COVID-19 outbreak. With so many potential applications-biosensors, vaccines, disinfectants, and nanoparticles/functionalized nanoparticles have become increasingly attractive tool in the battle against viral epidemics. The function of nanoparticles in pandemic control is assessed in this book chapter, and their possible uses, advantages, and drawbacks are examined. The significance of nanotechnology in managing viral outbreaks, namely in vaccine development, is the first topic we cover. Although the use of metallic nanoparticles to functionalize protective face masks has become popular as a sustainable substitute for throwaway masks, improving virus filtering and cutting down on waste generation, incorrect disposal of these masks might pollute the environment and even cause ecological damage. In our second section, we will discuss various types of nanoparticles or functionalized nanoparticles-based sensors to detect the pandemic associated viruses at very early stage. For this purpose, along with various types of nanoparticle based-sensors, the selection of appropriate electrochemical techniques is also equally important for the better performance of the constructed biosensors. Along with COVID-19 we will discuss other pandemics such as swine flu, HIV/AIDS, and black death. We must reduce such possible dangers and environmental effects in order to properly control outbreaks. For this reason, it is essential to comprehend the benefits and drawbacks of using nanoparticles while creating efficient plans for controlling pandemics moving forward. © 2025 Elsevier Inc. All rights reserved.
Synthesis, characterization and catalytic application of some novel binuclear transition metal complexes of bis-(2-acetylthiophene) oxaloyldihydrazone for CN bond formation
(2013) Divya Pratap Singh; Dushyant S. Raghuvanshi; K.N. Singh; Vinod P. Singh
In the present work, synthesis, characterization and catalytic properties of some novel complexes derived from a Schiff base bis-(2-acetylthiophene) oxaloyldihydrazone with various transition metal ions and precursors have been reported. The complexes were characterized by IR, NMR, ESR, electronic and mass spectroscopy, magnetic moments and TGA studies. Molecular structures of the ligand and its Cu(I) complex are determined by single crystal X-ray diffraction. Electronic spectral studies exhibit a 6-coordinated geometry around metal centers for Co(II), Ni(II) and Cu(II) complexes, whereas 4-coordinated geometry for Cu(I) and Zn(II) complexes. ESR spectra indicate a distorted octahedral geometry for Cu(II) complex in DMSO frozen solution. The electro-chemical studies of Ni(II) and Cu(II) complexes reveal a metal based reversible redox behavior. The catalytic activity of the complexes has been demonstrated for the cross-coupling of arylboronic acids with various N-nucleophiles. Ni(II) complex exhibited the maximum impact on catalytic activity with the product yields ranging from 62% to 82%. © 2013 Elsevier Ltd. All rights reserved.
Synthesis, spectral and single crystal X-ray diffraction studies on Mn(II), Ni(II), Cu(II) and Zn(II) complexes with 2-hydroxy-benzoic acid (phenyl-pyridin-2-yl-methylene)-hydrazide
(Elsevier Ltd, 2014) Pooja Singh; Divya Pratap Singh; Vinod P. Singh
The ligand 2-hydroxy-benzoic acid (phenyl-pyridin-2-yl-methylene)-hydrazide (Hbpph) and its Mn(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized. The metal complexes are characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, electronic, IR and NMR spectral techniques. The molecular structures of the ligand and metal complexes have been determined by single crystal X-ray diffraction studies. Hbpph acts as monobasic tridentate ligand and coordinates through pyridyl-N, azomethine-N and enolate-O with metal ion. Magnetic moments and electronic spectral studies of Mn(II), Ni(II) and Cu(II) complexes suggest a high spin six-coordinate geometry around metal ion. Single crystal structure of the ligand molecule displays a Z molecular conformation about the >CN- bond, whereas, the metal complexes exhibit E-configuration. The molecular structures of the metal complexes are stabilized by various H-bonding and C-H⋯π interactions. © 2014 Elsevier Ltd. All rights reserved.
Synthesis, structural investigations and corrosion inhibition studies on Mn(ii), Co(ii), Ni(ii), Cu(ii) and Zn(ii) complexes with 2-amino-benzoic acid (phenyl-pyridin-2-yl-methylene)-hydrazide
(Royal Society of Chemistry, 2015) Pooja Singh; Divya Pratap Singh; Karishma Tiwari; Monika Mishra; Ashish K. Singh; Vinod P. Singh
Mn(ii), Co(ii), Ni(ii), Cu(ii) and Zn(ii) complexes with 2-amino-benzoic acid (phenyl-pyridin-2-yl-methylene)-hydrazide (Habph) have been synthesized. The complexes were characterized by different physico-chemical and spectral studies viz. molar conductance, magnetic susceptibility measurements, electronic, IR and NMR spectra. The molecular structures of the ligand Habph and its Mn(ii), Ni(ii), Cu(ii), Zn(ii) complexes were further confirmed by single crystal X-ray diffraction technique. The Habph acts as a monobasic tridentate ligand coordinating through pyridyl-N, azomethine-N and enolate-O atoms with metal ions. Magnetic moments and electronic spectral studies suggest a high spin octahedral geometry for all the complexes. The ligand molecule exhibits a Z molecular conformation about the >CN- bond, whereas the metal complexes show E-configuration in their single crystal structures. The presence of inter- and intra-molecular H-bonding and various C-H⋯π interactions stabilize the molecular structure of the metal complexes. The structure of the Co(ii) complex has been satisfactorily modeled by density functional theory (DFT) and time dependent-DFT (TD-DFT) calculations. The results of electrochemical impedance spectroscopy (EIS) and adsorption behavior of the ligand and metal complexes show appreciable corrosion inhibition efficiency for mild steel in a 1 M HCl medium. The metal complexes show a better inhibition effect than the ligand. © 2015 The Royal Society of Chemistry.
Synthesis, thermal studies and spectral characterization of Co(II), Ni(II), Cu(II), and Zn(II) complexes with some polymeric diacetyl acyldihydrazone ligands
(2013) Vinod Prasad Singh; Divya Pratap Singh
Two 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.