BITS Faculty Publications
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Item Solvent effect on absorption and fluorescence spectra of cinchonine and cinchonidine dications: Estimation of ground and excited state dipole moments by experimental and numerical studies(Elsevier, 2015-06) Pant, Debi D.Absorption and fluorescence spectra of dications of cinchonine (C2 +) and cinchonidine (Cd2 +) have been measured at room temperature in solvents of different polarities. Ground and excited state electric dipole moments are determined experimentally using solvatochromic shift method based on bulk solvent properties. Theoretical calculations are done using B3LYP/6-31G(D) and CIS/6-31G(D) levels of theory for ground and excited states, respectively. Both experimental and theoretical studies reveal that excited state dipole moment (μe) values are higher than corresponding ground state dipole moment (μg) value of C2 + and Cd2 +, which is attributed to the higher polarity of excited states compared to the ground state polarity of these molecules.Item Solvatochromatic shift of absorption and fluorescence spectra of 6-methoxyquinoline: Estimation of ground and excited state dipole moments(Elsevier, 2013-03) Pant, Debi D.Electronic absorption and fluorescence spectra of protonated 6-methoxyquinoline (6MQ+) and neutral 6-methoxyquinoline (6MQ) have been recorded at room temperature in wide range of solvents of different polarities. The absorption maximum remains almost unchanged with the increase in solvent polarity, whereas a red shift in fluorescence emission maximum was observed. The ground-state dipole moment and the first excited singlet state dipole moment of 6MQ+ and 6MQ were obtained from Bakhshiev's and Bilot–Kawski's equations by means of solvatochromic shift method. High values of dipole moment are observed for excited state as compared to the corresponding ground state dipole moment values of 6MQ+ and 6MQ and this is attributed to the more polar excited states of 6MQ+ and 6MQ.Item Estimation of ground and excited state dipole moments of quinidine and quinidine dication: Experimental and numerical methods(Elsevier, 2013-03) Pant, Debi D.Absorption and fluorescence spectra of quinidine (QD) and quinidine dication (QD2 +) have been measured at room temperature in solvents of different polarities. Ground and excited state electric dipole moments are determined experimentally using solvatochromic shift method based on bulk solvent properties. Numerical calculations are also performed using B3LYP/6-31G(D) level of theory for ground state and CIS/6-31G(D) level of theory for first excited singlet state. From both experimental and numerical studies it has been observed that dipole moment values of excited states (μe) are higher than corresponding ground state value (μg), of QD and QD2 +, which is attributed to the higher polarity of excited states of QD and QD2 + molecules.Item Steady state and time-resolved fluorescence spectroscopy of quinine sulfate dication bound to sodium dodecylsulfate micelles: Fluorescent complex formation(Elsevier, 2014-01) Pant, Debi D.Interaction of quinine sulfate dication (QSD) with anionic, sodium dodecylsulphate (SDS) surfactant has been studied at different premicellar, micellar and postmicellar concentrations in aqueous phase using steady state, time-resolved fluorescence and fluorescence anisotropy techniques. At premicellar concentrations of SDS, the decrease in absorbance, appearance of an extra fluorescence band at lower wavelengths and tri-exponential decay behavior of fluorescence, are attributed to complex formation between QSD molecules and surfactant monomers. At postmicellar concentrations the red shift in fluorescence spectrum, increase in quantum yield and increase in fluorescence lifetimes are attributed to incorporation of solute molecules to micelles. At lower concentrations of SDS, a large shift in fluorescence is observed on excitation at the red edge of absorption spectrum and this is explained in terms of distribution of ion pairs of different energies in the ground state and the observed fluorescence lifetime behavior corroborates with this model. The temporal fluorescence anisotropy decay of QSD in SDS micelles allowed determination of restriction on the motion of the fluorophore. All the different techniques used in this study reveal that the photophysics of QSD is very sensitive to the microenvironments of SDS micelles and QSD molecules reside at the water-micelle interface.Item Estimation of ground and excited state dipole moments of synthesized coumarin derivative [N-(2-oxo-2H-chromen-4-yl)imino]triphenyl-phosphorane(Elsevier, 2014-12) Pant, Debi D.Electronic absorption and fluorescence spectra of coumarin derivative [N-(2-oxo-2H-chromen-4-yl)imino] triphenyl phosphorane have been recorded at room temperature in wide range of solvents of different polarities. The absorption maximum remains almost unchanged with the increase in solvent polarity, whereas, a red shift in fluorescence emission maximum was observed. Synthesized compound [N-(2-oxo-2H-chromen-4-yl)imino] triphenyl phosphorane was characterized by 1H and 13C NMR, and FT-IR spectral studies. The ground and excited state dipole moments of molecule were obtained from Bakhshiev's and Bilot–Kawski's equations by means of the solvatochromic shift method. Very high value of dipole moment is observed for excited state as compared to ground state value and this is attributed to more polar excited state of the molecule. Numerical calculations are performed using B3LYP/6-31G+(d) and B3LYP/6-31G(d) level of theory for ground state in Gaussian 03. Studies in different solvents are also done using the CPCM method and UA0 radii with the same level of theory. A critical analysis between the values of dipole moment in gas phase and various solvents is also carried out for ground state.Item Solvatochromic shift and estimation of dipole moment of quinine sulfate(Elsevier, 2012-02) Pant, Debi D.The absorption and fluorescence spectra of quinine sulfate (QS) have been recorded at room temperature in wide range of solvents of different polarities. The ground-state dipole moment of QS was obtained from quantum mechanical calculations and the excited state dipole moment of QS was estimated from Bakhshiev's and Bilot–Kawski's equations by means of solvatochromic shift method. Higher value of dipole moment has been observed for excited state as compared to the corresponding ground state value and this is attributed to the more polar excited state of QS.Item Ground and excited state dipole moments of quinine sulfate dication: Solvatochromic shift of absorption and fluorescence spectra(Elsevier, 2012-08) Pant, Debi D.Electronic absorption and fluorescence spectra of quinine sulfate dication (QSD) have been recorded at room temperature in a wide range of solvents of different polarities. The absorption maximum remains almost unchanged with the increase in solvent polarity, whereas a red shift in fluorescence emission maximum was observed. The ground-state dipole moment of QSD was obtained from quantum mechanical calculations and the first excited singlet state dipole moment of QSD was obtained from Bakhshiev's and Bilot–Kawski's equations by means of solvatochromic shift method. Very high value of dipole moment is observed for excited state as compared to the corresponding ground state value and this is attributed to the more polar excited state of QSD. Compared to the dipole moment of quinine sulfate, both the ground and excited state dipole moments of QSD are lower.Item Synthesis, Absorption, and Fluorescence Studies of Coumaryl-Labelled Amino Acids and Dipeptides Linked Via Triazole Ring(CSIRO, 2015-04-07) Sakhuja, Rajeev; Pant, Debi D.Fluorophores based on 4-triazolyl, 7-hydroxy-4-triazolylmethyl, 4-O-triazolylmethyl, and 7-O-triazolylmethyl coumaryl-tagged amino acids and dipeptides were synthesized by copper-catalyzed [3 + 2] cycloaddition reaction between azido- or alkynyl-functionalized coumarins with alkynyl- or azido-functionalized amino acid and dipeptides in good-to-excellent yields. Steady-state absorption and the fluorescence properties of the synthesized conjugates were studied. The chemical applicability of these amino acid and peptide-based fluorophores was successfully demonstrated by their linear elongation by further tagging them with appropriate C- or N-terminus amino acid.Item Estimation of ground and excited-state dipole moments of synthesized coumarin derivative, (S)-(1-((7-hydroxy-2-oxo-2H-chromen-4-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl 2-(((9H-fluoren-9-yl)methoxy)cabonylamino)-3-phenylpropanoate from a solvatochromic shift and theoretical methods(Elsiever, 2015-09) Sakhuja, Rajeev; Pant, Debi D.The electronic absorption and fluorescence spectra of coumarin derivative, (S)-(1-((7-hydroxy-2-oxo-2H-chromen-4-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl2-(((9H-fluoren-9-yl)methoxy)cabonylamino)-3-phenylpropanoate have been studied in solvents of different polarities, and the data were used to study the solvatochromic properties. The absorption maximum remains almost unchanged with the increase in solvent polarity, whereas a red shift in fluorescence emission maximum was observed. Synthesized compound (S)-(1-((7-hydroxy-2-oxo-2H-chromen-4-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl2-(((9H-fluoren-9-yl)methoxy)cabonylamino)-3-phenylpropanoate was characterized by 1H and 13C NMR, and FT-IR spectral studies. The ground and excited state dipole moments of molecule were obtained from Bakshiev's and Bilot–Kawski's equations by means of solvatochromic shift method. High value of dipole moment is observed for excited state as compared to ground state value and this is attributed to more polar excited state of molecule. Also, fluorescence emission peak undergoes a bathochromic shift with increase in the polarity of the solvent, confirming π → π* transition. Numerical calculations are performed using B3LYP/6-31G(d) level of theory for the ground state using Gaussian 03. Studies in different solvents are also done using IEF-PCM method and UA0 radii. A comparative analysis between the values of dipole moment in gas phase and various solvents is also done for the ground state.Item Experimental and theoretical study: Determination of dipole moment of synthesized coumarin–triazole derivatives and application as turn off fluorescence sensor: High sensitivity for iron(III) ions(Elsiever, 2015-12) Sakhuja, Rajeev; Pant, Debi D.Electronic absorption and fluorescence spectra of two synthesized coumarin–triazole based probes (S)-(1-((7-hydroxy-2-oxo-2H-chromen-4-yl) methyl)-1H-1,2,3-triazol-4-yl)methyl 2-(tert-butoxycabonylamino)-3-phenylpropanoate and (S)-(1-((7-hydroxy-2-oxo-2H-chromen-4-yl)methyl)-1H-1,2,3-triazol-4-yl) methyl 2-(benzyloxycabonylamino)-3-phenylpropanoate have been recorded at room temperature in wide range of solvents of different polarities. Synthesized compounds were characterized by 1H and 13C NMR, and FT-IR spectral studies. The ground and excited state dipole moments of molecules were obtained from Bakshiev's and Bilot–Kawski's equations by means of solvatochromic shift method. A DFT based studies in different solvents are also performed using IEF-PCM method and UA0 radii. A comparative analysis between the values of dipole moment in gas phase and various solvents is also performed for the ground state. The potential sensor behaviors of these compounds to metal ions have also been examined by fluorescence spectroscopy and these compounds exhibited as fluorescence sensor for the determination of Fe3+ ions in solution. Effect of various metal ions on fluorescent behavior was also studied. Both the synthesized compounds act as selective and sensitive sensor for micromolar detection of Fe3+ ions. Binding stoichiometry of Fe3+ ion detection was also investigated. Conventional binding energy calculations are performed to determine the relative stability of Fe(III) complexes.