Faculty Publications
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Item Electrooptical characteristics and anion binding behaviour of organic receptors: Effect of substitution on colorimetric response(Elsevier B.V., 2017) Pangannaya, S.; Trivedi, D.R.A series of four organic receptors, R1, R2, R3 and R4 possessing [sbnd]NH unit as binding site with varied positional substitution of [sbnd]OH and [sbnd]NO2functionalities have been synthesized and studied for their anion binding ability. Significant changes were observed in the UV–vis spectra of receptors with the addition of AcO?ion justifying the observed color changes visible to naked eye. Receptors R1, R2 and R3 showed mild color changes in the presence of F?and H2PO4 ?ions whereas R4 exhibited selective response towards AcO?ion. UV–vis titration and cyclic voltammetric studies performed with the incremental addition of AcO?ion to the receptors confirmed the anion binding process. The band gap value derived from the experimental results of UV–vis spectroscopic and cyclic voltammetric studies support the formation of AcO?ion-receptor complex. 1H NMR titration studies performed with the addition of AcO?ion to receptor R3 confirms the deprotonation of the [sbnd]NH proton involved in the binding mechanism. © 2017 Elsevier B.V.Item Design and synthesis of a new organic receptor and evaluation of colorimetric anion sensing ability in organo-aqueous medium(Elsevier B.V., 2017) Pangannaya, S.; Tarafder, K.; Trivedi, D.R.A new organic receptor has been designed and synthesized by the combination of aromatic dialdehyde with nitro-substituted aminophenol resulting in a Schiff base compound. The receptor exhibited a colorimetric response for F? and AcO? ion with a distinct color change from pale yellow to red and pink respectively in dry DMSO solvent and yellow to pale greenish yellow in DMSO:H2O (9:1, v/v). UV–Vis titration studies displayed a significant shift in absorption maxima in comparison with the free receptor. The shift could be attributed to the hydrogen bonding interactions between the active anions and the hydroxyl functionality aided by the electron withdrawing nitro substituent on the receptor. 1H NMR titration and density functionality studies have been performed to understand the nature of interaction of receptor and anions. The lower detection limit of 1.12 ppm was obtained in organic media for F? ion confirming the real time application of the receptor. © 2016Item Spectral and DFT studies of anion bound organic receptors: Time dependent studies and logic gate applications(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften info@beilstein-institut.de, 2017) Pangannaya, S.; Purayil, N.P.; Dabhi, S.; Mankad, V.; Jha, P.K.; Shinde, S.; Trivedi, D.R.New colorimetric receptors R1 and R2 with varied positional substitution of a cyano and nitro signaling unit having a hydroxy functionality as the hydrogen bond donor site have been designed, synthesized and characterized by FTIR, 1H NMR spectroscopy and mass spectrometry. The receptors R1 and R2 exhibit prominent visual response for F- and AcO- ions allowing the real time analysis of these ions in aqueous media. The formation of the receptor-anion complexes has been supported by UV-vis titration studies and confirmed through binding constant calculations. The anion binding process follows a first order rate equation and the calculated rate constants reveal a higher order of reactivity for AcO- ions. The 1H NMR titration and TDDFT studies provide full support of the binding mechanism. The Hg2+ and F- ion sensing property of receptor R1 has been utilized to arrive at "AND" and "INHIBIT" molecular logic gate applications. © 2017 Pangannaya et al.; licensee Beilstein-Institut.Item Synthesis and spectral investigation of colorimetric receptors for the dual detection of copper and acetate ions: application in molecular logic gates(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2017) Pangannaya, S.; Kaur, A.; Mohan, M.; Raval, K.; Chand, D.K.; Trivedi, D.R.Colorimetric receptors L1, L2 and L3 possessing –OH functionality as binding site and –NO2 as signalling unit with varied positional substitution of –OMe functionality has been designed and synthesised by simple Schiff base condensation reaction. Receptors L1, L2 and L3 showed selective response towards AcO?ion among other interfering monovalent anions viz., F?, Cl?, Br?, I?, NO3 ?, HSO? 4 and H2PO? 4. L2 imparts high selectivity towards AcO? ion assisted by push-pull effect of –NO2 and –OMe functionality in conjugation with imine linkage. The binding constant for L2–OAc complex was found to be 9.04 × 104 M?2. L2 exhibited a detection limit of 0.61 ppm towards NaOAc. The selectivity of L1 towards Cu2+ ions with a lower detection limit of 1.81 ppm implies the role of electron donating –OMe in favouring the coordinative interaction of hetero atoms of L1 with Cu2+ ions. The selective detection of AcO? and Cu2+ ions is further established with OR and INHIBIT logic gate application of receptors L1, L2 and L3 correspondingly. The colorimetric studies reveal the role of OMe functionality in the selective detection of AcO? and Cu 2+ ions in aqueous media. © 2017 Informa UK Limited, trading as Taylor & Francis Group.Item Colorimetric and fluorometric turn-on sensor for selective detection of fluoride ions: Sol-gel transition studies and theoretical insights(Royal Society of Chemistry, 2018) Pangannaya, S.; Mohan, M.; Trivedi, D.R.A new organic receptor R1 based on a naphthyl unit covalently linked to a long alkyl chain has been designed, synthesized and characterized by standard spectroscopic techniques. The colorimetric response of receptor R1 from colorless to a pale yellow color and blue fluorescence emission in the presence of F- ions revealed its selective sensing ability in the solution phase. UV-Vis titration, fluorescence titration and 1H NMR titration studies confirmed the formation of the R1-F- complex. Receptor R1 formed a stable gel in DMSO and was confirmed through the standard heating-and-cooling method. Addition of F- ions resulted in disruption of the gel forming a solution that exhibited blue fluorescence emission. The binding constant of the R1-F- complex was found to be of the order of 5.9 × 105 M-1. DFT studies revealed the formation of the receptor-anion complex agreeing well with the experimental results. The detection limit was calculated and found to be 0.8 ppm, implying the potential for application of receptor R1 in environmental applications. © 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item Electroanalytical and spectral investigation of organic receptors as colorimetric and absorption ratiometric anion chemosensor(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2018) Pangannaya, S.; Thimaradka, V.; Trivedi, D.R.Colorimetric receptors R1 and R2 have been designed and synthesized by Schiff base condensation and characterised by standard spectroscopic techniques. Anion binding ability of the receptors have been investigated quantitatively through optical, electrochemical and 1HNMR titration studies. UV-vis spectra of receptor R1 and R2 exhibited a significant red shift for F? and AcO? ions with a visual color response. Receptor R1 exhibited selective response towards AcO? ion in the presence of HEPES buffer media. Incremental color change of receptor R2 with the higher equivalence of AcO? ions clearly represent the ratiometric response. Cyclic voltammetric studies of R1 and R2 exhibits shift in oxidation and reduction peak with successive addition of AcO? ions indicating the anion induced oxidation of -NH and reduction of the keto group and nitro species. Electrooptical and 1H NMR titration studies of R2 collectively reflects the anion induced change of chromophore from C=N to N=N indicative of azo-hydrazone tautomeric signaling in the presence of AcO? ions. Lower detection limit of 2.1 and 0.41 ppm achieved with sodium salt of AcO? ion with R1 and R2 reflects their utility as colorimetric chemosensor. © 2017 Informa UK Limited, trading as Taylor & Francis Group.Item Photophysical and electrochemical properties of organic molecules: Solvatochromic effect and DFT studies(Elsevier B.V., 2018) Mohan, M.; Pangannaya, S.; Satyanarayan, M.N.; Trivedi, D.R.A series of five Schiff base molecules M1, M2, M3, M4 and M5 have been designed and synthesized by aldol condensation reaction. Synthesized molecules have been characterized by standard spectroscopic techniques in order to confirm their structural traits. The solvatochromic behavior of molecules M1 to M5 in solvents of varying polarity were investigated by UV–Vis, fluorescence spectroscopy and supported by TD-DFT calculations. DFT studies performed in the gas phase confirmed the energy stabilized structure of the molecules M1 to M5. Structural characteristics of molecule M2 favored higher fluorescence emission with a quantum yield of 0.35 and a solid-state emission of 512 nm. Fluorescence lifetime measurement of the molecules M1 to M5 exhibited a lifetime of order 2–5 ns. Overall, molecule M2 can find its application in organic light emitting diodes as a non-dopant emitter material. © 2018 Elsevier B.V.Item Hydrazinylpyridine based highly selective optical sensor for aqueous source of carbonate ions: Electrochemical and DFT studies(Elsevier B.V., 2018) Thimaradka, V.; Pangannaya, S.; Mohan, M.; Trivedi, D.R.A series of new receptors PDZ1–3 based on 2-(arylidenehydrazinyl)pyridines have been designed and synthesized for the detection of biologically and environmentally important ions. The colorimetric detection of CO32 ? using neutral organic receptor PDZ-1 has been achieved with characteristic visual colour change from yellow to green accompanied by a large redshift of 215 nm in absorption maxima. UV–Vis spectroscopic and cyclic voltammetric studies reveal the stoichiometry of binding and electrochemistry of host-guest complex formation. The binding constant was found to be 0.77 × 104 M? 2. In addition, electrochemical studies provide an insight into the stability of the complex. DFT studies performed on the PDZ-1 and PDZ-1 ? CO32 ? complex reveal the binding mechanism involved in the anion detection process. PDZ-1 is highly selective for carbonate and does not show any colorimetric response towards any other anions or cations, while PDZ-2 and PDZ-3 remain inactive in the ion detection process. The limit of detection (LOD) and limit of quantification (LOQ) of PDZ-1 for carbonate was found to be 0.11 mM and 0.36 mM respectively. Considerable binding constant and limit of detection make PDZ-1 to be used as a real time sensor for the detection of carbonate in environmental and biological samples. © 2017 Elsevier B.V.Item Multicoloured Thiophene Based AIEgens: Single Crystal Structure Elucidation, Spectral Behaviour and DFT Studies(Wiley-Blackwell info@wiley.com, 2018) Mohan, M.; Pangannaya, S.; Satyanarayan, M.N.; Trivedi, D.R.A series of Schiff base thiophene derivatives, D1 to D9, which exhibits a phenomenon of aggregation-induced emission enhancement (AIEE) have been synthesised and characterized by standard spectroscopic techniques. Multicoloured emission enhancement has been achieved just by introduction of electron donating and withdrawing substituent on the thiophene moiety. Few of the molecules in the series exhibited enhanced fluorescence emission intensity in solvent mixture in comparison with that observed in pure solvent supportive of AIE. Single crystal x-ray diffraction (SCXRD) studies on selected molecules, D6 and D7 of the series revealed the existence of planar structure and a herringbone type of crystal packing arrangement. In specific, molecules D6 and D7, possesses a larger ?-? stacking distance of around 4.866 Å and 4.636 Å, which curbs all the non-radiative pathways, in turn leading to AIEE. DFT and TDDFT calculations confirm the structural planarity supportive of SCXRD analysis and the nature of electronic transition correlating well with the experimental results. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem Screening of chitin deacetylase producing microbes from marine source using a novel receptor on agar plate(Elsevier B.V., 2019) Pawaskar, G.-M.; Pangannaya, S.; Raval, K.; Trivedi, D.; Raval, R.Chitosan is a deacetylated form of naturally occurring polymer; chitin. On an industrial scale, the deacetylation of chitin to chitosan is performed using harsh chemicals like sodium hydroxide. This not only adds to the environmental pollution but the product is also random in terms of its deacetylation. This shortcoming can be addressed by using enzymes like chitin deacetylase (CDA). The screening of these organisms would require a reliable, fast and sensitive screening method. The deacetylation of chitin into chitosan, releases acetate as the byproduct of the reaction. A receptor which specifically binds to the acetate ion was synthesized chemically. The receptor upon binding with the acetate ion emitted a fluorescence which could be viewed using the gel documentation unit. The receptor was optimized for the screening of CDA producing microbes with the positive fungal control as Penicillium sp. and bacterial control as Bacillus megaterium. A parallel study with the 4-Nitroacetanilide, the reported screening indicator for CDA was performed. The results obtained with the receptor in the present study were concordant with the 4-Nitroacetanilide. Upon standardization, the protocol was extended for the screening of CDA producing microbes from the marine crustacean dumped soil and water samples. The CDA activity of these microbes was further confirmed using spectrophotometric MBTH assay. This is the first report using this receptor for the screening of CDA producers. The method is not only sensitive but also reproducible and can be extended for a high throughput screening of CDA producers. © 2019 Elsevier B.V.