BITS Faculty Publications

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    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.
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    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.
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    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.
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    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.
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    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.
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    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.
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    Vapor phase self-assembly of metal-porphyrins for controllable work function tuning
    (IEEE, 2017) Rao, V. Ramgopal
    A novel process for self-assembly of metal-porphyrins on oxide dielectrics is developed and utilized for continuous work function tuning. Simply by changing the central metal atom present at the core of porphyrin helps change the dipole moment at the metal-dielectric interface leading to change in work function. Further the development of vapor phase process makes the process of the self-assembly easy to integrate with the CMOS processes. The highly selective and pattern enabled process shows great potential for controllable work function tuning for metal gate nano-scale technologies. The fine tuning is done by using zinc, nickel and copper porphyrin self-assembled monolayers formed at the metal-dielectric interface using a vapor phase approach.
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    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.
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    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.
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    Solvatochromic shift and estimation of dipole moment of synthesized coumarin derivative: Application as sensor for fluorogenic recognition of Fe3 + and Cu2 + ions in aqueous solution
    (Elsiever, 2016-10) Sakhuja, Rajeev; Pant, Debi D.
    (S)-4-((4-((3-amino-2-oxo-4-phenylbutoxy)methyl)-1H-1,2,3-triazol-1-yl)methyl)-7 hydroxy-2H-chromen-2-one hydrochloride was synthesized and characterized by detailed spectroscopic studies such as 1H, 13C NMR and HRMS. Excited state dipole moment of synthesized compound was obtained using different solvatochromic shift methods. 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. The potential sensor behavior of the compound to metal ions has also been examined. Chemosensor shows the sensitivity for Fe3 + and Cu2 + over other metal cations in aqueous solution. The detection limits of Fe3 + and Cu2 + were calculated to be 143 nM and 71.31 μM, respectively. The LC–mass analysis indicated that 1:1 complex was formed between Fe3 + (or) Cu2 + and compound. Binding energy values for the complexation of the compound with metal ions are theoretically computed at M06/6–31 + G(d,p) level. The DFT based binding energy values show good correlation with the experimental observations.