Browsing by Author "Vinod Prasad Singh"

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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 coumarin-derived multi-faceted optical material with molecular logic gate for bioimaging
(Royal Society of Chemistry, 2025) Amit Kumar Singh; Pranjalee Yadav; Aayoosh Singh; Avanish Kumar Singh; Shashi Kant Sharma; Vijay Kumar Sonkar; Vinod Prasad Singh
The development of stimuli-responsive, multi-faceted chromic materials has gained the interest of the material science community recently, owing to their vast range of applications in several areas simultaneously, such as viscosity, temperature, and pressure detectors. In this context, a coumarin-derived organic luminophore, HCFH, has been designed and extensively investigated for its characteristics, such as aggregation-induced emission (AIE), viscochromism, piezochromism, thermochromism, and distinguishable fluorometric detection of Zn2+ and Cu2+ ions in water. The emission intensity of HCFH amplifies 111-fold with the addition of water in tetrahydrofuran (THF), validating its aggregation-induced emission (AIE) nature. Multi-colored piezochromism is observed in the ‘crystalline’, ‘pristine’, and ‘ground’ forms of HCFH as non-emissive, weakly cyan-emissive, and bright green-emissive, respectively. Further, powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) analyses indicate a crystalline-to-amorphous phase transition during grinding. HCFH exhibits remarkable photophysical properties, including viscosity, polarity, and temperature-dependent emissions. The probe selectively detects Zn2+ and Cu2+ ions with limits of detection (LOD) of 1.14 and 1.54 nM, respectively, employing chelation-enhanced fluorescence (CHEF) and inhibition of photo-induced electron transfer (PET) for Zn2+ and paramagnetic fluorescence quenching for Cu2+. The Job's plots indicate 1 : 2 and 1 : 1 (M : L) binding stoichiometries for Zn2+ and Cu2+, respectively, which are confirmed by their single-crystal structures. Molecular logic gates and paper strip kits are also developed utilizing their sensing capabilities. HCFH has been found highly effective in bio-imaging of Zn2+ and Cu2+ in HeLa cells. Microscopic examination of the cells indicates that the probe is localized in both the cytosol and mitochondria of the cells. © 2025 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 Stimuli Responsive Multifunctional Smart Luminophore with Aggregation-Induced Enhanced Emission
(John Wiley and Sons Inc, 2025) Aayoosh Singh; Amit Kumar Singh; Pranjalee Yadav; Avanish Kumar Singh; Pradeep Kumar; Saripella Srikrishna; Vinod Prasad Singh
The development of multifunctional luminophores with tunable and stimuli-responsive optical properties is critical for the advancement of sensing, bioimaging, and optoelectronic technologies. Herein, a novel coumarin-based smart luminogen, (E)-N'-(1-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)ethylidene)thiophene-2-carbohydrazide (ETH) is developed that exhibits pronounced multistimuli responsive behavior including aggregation-induced enhanced emission (AIEE), solvatochromism, viscochromism, reversible mechanochromism, and acidochromism. ETH shows solid-state fluorescence modulation on applying mechanical stress and exposing in acid/base vapor, with reversible redshifted emission. The ETH coated paper enables its practical applications in pressure-sensitive devices and portable acid vapor detection kits. In a mixed CH3CN–H2O system, ETH functions as a solvent-controlled dual-mode fluorescent probe, showing a turn-on response to Zn2+ and a turn-off response to Cu2+ with high sensitivity. Job's plot revealed 2:1 ligand-to-metal stoichiometry for Zn2+ and 1:1 for Cu2+. The fluorescent aggregates of ETH enable selective detection of Cu2+ through a disaggregation-induced fluorescence quenching mechanism. A portable cotton-swab-based test kit is developed for practical and on-site detection of Cu2+. ETH demonstrates excellent biocompatibility, as predicted by in vivo fluorescence imaging in Drosophila larval gut tissues. The combination of reversible optical switching, high fluorescence quantum yield and structural adaptability establish ETH as a novel multifunctional material for sensing, live-cell imaging, and smart optoelectronic devices. © 2025 Wiley-VCH GmbH.
Anthracene appended AIEgen as a reversible fluorescence sensor for hazardous cyanide ion in environmental samples and fabrication of portable test kit for on spot detection
(Elsevier B.V., 2025) Pranjalee Yadav; Aayoosh Singh; Gautam Kumar; Saumya Singh; Vinod Prasad Singh
CN− is a frequently encountered pollutant in water and soil. Due to its extreme lethal effect on mammals, serious consideration and efforts are needed for monitoring this hazardous anion. To address this challenge, herein, an anthracene-appended AIEgen (ACFH) has been synthesized and developed for selective fluorometric detection of CN− ion. The detection limit of the probe has been found to be 3.42 × 10−7 M (8.89 ppb), which is much lower than WHO standard (2.7 × 10−6 M). The interaction with CN− causes deprotonation of the probe and subsequent loss of planarity, which has been thoroughly confirmed from 1H NMR titrations and DFT calculations. The reversibility and reusability of ACFH and corresponding logic gates enhance its sensing performance and efficacy. Notably, it has been utilized to meritoriously quantify CN− in various water samples and the fabrication of a portable test kit for monitoring CN− in real time. In addition, the aggregation induced emission (AIE) property has been precisely explored with the aid of fluorescence spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), fluorescence quantum yield and lifetime analysis. © 2024 Elsevier B.V.
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) Romi Dwivedi; Saumya Singh; Brijesh Singh Chauhan; S. Srikrishna; Anoop Kumar Panday; Lokman H. Choudhury; Vinod Prasad Singh
An 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.
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.
Carbazole-quinoline based ultrasensitive fluorometric sensor for detection of Hg2+ in aqueous medium: Crystal structure, DFT and real sample application
(Elsevier B.V., 2025) Avanish Kumar Singh; Aayoosh Singh; Pranjalee Yadav; Amit Kumar Singh; Vinod Prasad Singh
A novel carbazole-quinoline tagged fluorophore, (E)-9-ethyl-3-((2-(quinolin-2-yl)hydrazineylidene)methyl)-9H-carbazole (QHC), has been synthesized with an excellent yield using the simple one-pot synthesis and its molecular structure is determined by single crystal X-ray diffraction, FT-IR, NMR and mass spectroscopic techniques. QHC has been developed as an ultrasensitive fluorometric sensor for detection of Hg2+ in the presence of competing metal ions in aqueous medium. It exhibited remarkable sensitivity and selectivity towards Hg2+ with limit of detection (LOD) of 2.59 × 10−8 M and a remarkable Stern-Volmer constant (Ksv) of 1.17 × 105 M−1. The Job's plot displayed 1:1 stoichiometry between QHC and Hg2+, with a binding constant (Ka) of 1.01 × 105 M−1. The binding mechanism has been demonstrated by FT-IR, mass spectrometry, 1H NMR titration and density functional theory (DFT) analysis. Upon interaction with Hg2+, the photo-induced electron transfer (PET) from quinoline-carbazole framework to Hg2+ is activated, thereby, completely quenching the fluorescence. The practical applicability of QHC was demonstrated through the development of test kits. Additionally, QHC was successfully employed to detect Hg2+ ions in real water samples, including lake water and Ganga river water, showing its significance in environmental monitoring. © 2025 Elsevier B.V.
Enhanced corrosion resistance of low alloy steel in NaCl environment using 3-substituted chromone derivatives in epoxy coatings
(Elsevier B.V., 2025) Meenakshi Sharma; Meenakshi Thakran; Rakesh Kumar Tiwari; Gautam Kumar; Vinod Prasad Singh; Suman Lata; Sumit Kumar
This study investigates the corrosion-controlling impact of newly synthesized 3-substituted chromone derivatives incorporated as eco-friendly additives in epoxy coatings to improve the corrosion resistance of low alloy steel (LAS) exposed to a corrosive 3.5 % NaCl solution. This is the first time, as far as we know, that such a chromone-based compound has been investigated for use in coatings, marking a significant advancement from traditional toxic corrosion inhibitors to environmentally benign alternatives. The novel chromone derivates were characterized by 1H NMR, 13C NMR, and FT-IR. 3-substituted chromone derivates were applied to LAS substrates and evaluated for their corrosion protection using electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization techniques(PDP) at 298 K at various concentrations (0.25 %, 0.50 %, and 1.00 %), where 0.25 wt% were identified as an optimized concentration for all compounds. Furthermore, EIS and potentiodynamic polarization studies of the various formed coatings also revealed that 0.25 % of (E)‑prop-2-yn-1-yl 3-(7‑hydroxy-4-oxo-4H-chromen-3-yl) acrylate (MSC-5) was the most optimized coating, with an outstanding protection efficacy of 96.91 % even after 336 h of immersion in a 3.5 % NaCl solution. An improvement attributed to the presence of phenolic -OH in MSC-5 enhanced the adhesion and barrier properties of the coating. Contact angle measurements demonstrated the hydrophobicity order of the BS < Epoxy < MSC < MSC-4 < MSC-5-containing coating and highlighted their efficacy as a moisture-resistant barrier. Atomic Force Microscopy (AFM) and FESEM analyses further illustrated the homogeneous dispersion of MSC-5 within the epoxy matrix, with minimal pores or microcracks, thus contributing to the coating's integrity and corrosion resistance. Furthermore, the protective properties of the coating were reinforced by the donor-acceptor interaction using density functional theory. © 2024 Elsevier B.V.
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.
Metal-free graphitic carbon nitride nanosheet for dual mode fluorescence and electrochemical detection of para-nitrophenol
(Royal Society of Chemistry, 2025) Ankush Kumar Kumar Singh; Aayoosh Singh; Mithilesh Patel; Vinod Prasad Singh; n. Rosy
para-Nitrophenol (p-NP) contamination poses significant risks to both environmental and human health, highlighting the urgent need for sensitive and selective methods for its detection. In this study, a graphitic carbon nitride sheet (g-CNS) synthesized via a one-step hydrothermal method is proposed as a bi-functional probe for p-NP sensing. The fluorescence activity of the g-CNS was first optimized, and its quenching on the addition of p-NP was used for the fluorometric detection of p-NP. A broad linear response to p-NP concentrations ranging from 1 to 100 μM was observed, with a detection limit of 36.76 nM. The sensor exhibited excellent performance in the presence of potential interferences and was successfully applied to real sample analysis. To enhance on-site detection applicability, a g-CNS modified voltammetric sensor was developed. The g-CNS was electrodeposited on a glassy carbon electrode (GCE) using cyclic voltammetry and characterized using a range of techniques to confirm the successful modification. When applied to p-NP detection, the modified GCE demonstrated high sensitivity, with a limit of detection (LOD) of 218 nM. Furthermore, the stability, reusability, and reproducibility of the modified electrode were thoroughly evaluated, confirming its reliability for long-term use in electrochemical sensing applications. © 2025 The Royal Society of Chemistry.
Synthesis, characterization and physicochemical studies of some Copper(II) tetrathiocyanato dithallate(I) complexes with hydrazides and hydrazones
(1994) Krishan Kumar Narang; Jagdamba Prasad Pandey; Vinod Prasad Singh
Copper(II) complexes of the type Cu[Tl(SCN2]2·L [where L = benzoic hydrazide (BH), isonicotinic hydrazide (INH), salicyclic hdyrazide (SH), anthranilic hydrazide (AH), p-hydroxybenzoic hydrazide (PHBH), p-aminobenzoic hydrazide (PABH) and their isopropanone derivatives, i.e. isopropanone benzoylhdyrazone (IBH), isopropanone isonicotinoyl hydrazone (IINH), isopropanone salicyloylhydrazone (ISH) and isopropanone anthranoylhydrazone (IAH)] were synthesized and characterized. All the complexes are non-electrolytes, and dissociate in H2O, C2H5OH, CH3CN and CH3COCH3. They are either coordinated through CO and NH2 groups of the hydrazide or CO and CN of the hydrazone ligands. The electronic and ESR spectra suggest a planar geometry for Cu[Tl(SCN2]2 and a tetragonally distorted octahedral structure for all other complexes. The X-ray diffraction parameters for some of the complexes correspond to a tetragonal crystal lattice. © 1994.
Synthesis, spectral characterization and antimicrobial activity of some transition metal(II) complexes with acetone p-amino acetophenone benzoylhydrazone
(2008) Vinod Prasad Singh; Anshu Katiyar
Complexes 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.
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.
Ultrasound defect sensitive mechanochromic material with blue-shifted emission for the detection of Cu2+ in Alzheimer's disease cells
(Royal Society of Chemistry, 2025) Aayoosh Singh; Pranjalee Yadav; Amit Kumar Singh; Rupen Tamang; Biplob Koch; Vinod Prasad Singh
The mechanistic investigation and design of ultra-sensitive smart materials with multi-stimuli responsive properties are attracting much interest due to their utilization in several areas concurrently, such as mechanochromic and acidochromic materials, defect sensors, and chemosensors for analytes. Herein, the tailoring of an external stimuli-responsive novel coumarin-based luminogen (CFH) exhibiting green emission (λem = 515 nm) in the liquid state and red emission (λem = 698 nm) in the solid state opens up new avenues for the design of near-infrared emitting coumarin-based materials. CFH is an aggregation-induced enhanced emission (AIEE)-active material exhibiting solvatochromism and viscochromism. The weakly emissive crystals of CFH showed a relatively rare blue-shifted (48 nm) enhanced emission (3-fold) upon grinding. Fluorescence microscopy demonstrated that defect areas on the crystal surface become extremely emissive, indicating a “turn-on” defect-sensitive mechanochromism, susceptible to impact, friction, sculpting and ultrasonic vibrations. Solid CFH displayed acidochromic properties with extraordinary reversibility when exposed to trifluoroacetic acid (TFA)/triethylamine (TEA) vapour, displaying an on-off-on emission. Furthermore, CFH demonstrated “on-off” fluorescence responses to Cu2+ in water, exhibiting a detection limit (LOD) of 1.1 nM and Stern-Volmer constant (Ksv) of 2.84 × 106 M−1. The Job's plot and SC-XRD demonstrated a 1 : 1 binding stoichiometry for the CFH-Cu2+ complex. Leveraging this fluorescence response, portable test kit devices were developed for the detection of Cu2+. Bioimaging was carried out to examine the quenching of the probe with accumulated Cu2+ in SH-SY5Y model cells for neurodegenerative disorders compared to HEK-293 cells, suggesting that CFH can also be used for the intracellular sensing of Cu2+ in Alzheimer's disease (AD) cells. © 2025 The Royal Society of Chemistry.