Author
Sneh K. Dogra
Bio: Sneh K. Dogra is an academic researcher from Indian Institute of Technology Kanpur. The author has contributed to research in topics: Excited state & Solvent effects. The author has an hindex of 28, co-authored 129 publications receiving 2357 citations.
Topics: Excited state, Solvent effects, Protonation, Dication, Deprotonation
Papers published on a yearly basis
Papers
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01 Mar 1986
TL;DR: A solvent dependence study of the steady state absorption, excitation and fluorescence spectra of 2-( o -hydroxyphenyl) benzimidazole has indicated the presence of different tautomers in the S 1 state which have the same precursor in S 0 state.
Abstract: A solvent dependence study of the steady state absorption, excitation and fluorescence spectra of 2-( o -hydroxyphenyl) benzimidazole has indicated the presence of different tautomers in the S 1 state which have the same precursor in the S 0 state. A similar study as a function of hydrogen ion concentration has identified the presence of dication, monocation, zwitterion, phototautomer and monoanion species. The respective pK a and pK * a values have been determined with fluorimetric titrations and Forster cycle methods and compared.
129 citations
TL;DR: Les spectres de fluorescence and absorption d'amino-5 indazole montrent que le groupe amino agit comme accepteur de liaison hydrogene dans l'etat S 0 and comme donneur dans L 1 as discussed by the authors.
Abstract: Les spectres de fluorescence et d'absorption d'amino-5 indazole montrent que le groupe amino agit comme accepteur de liaison hydrogene dans l'etat S 0 et comme donneur dans l'etat S 1 . Les etudes du PH montrent que le monocation et le monoanion sont differents dans S 0 et S 1
83 citations
TL;DR: In this article, the absorption and fluorescence spectra of 2-(4'-N,N-dimethylamino)phenyl)benzothiazole (DMAPBT) and 2-( 4'-(N, N-dimethylphenyl)-benzimidazole(DMAPBI) have been recorded in solvents of different polarity and hydrogen-bonding nature.
Abstract: The absorption and fluorescence spectra of 2-(4'-(N,N-dimethylamino)phenyl)benzothiazole (DMAPBT) and 2-(4'-(N,N-dimethylamino)phenyl)benzimidazole (DMAPBI) have been recorded in solvents of different polarity and hydrogen-bonding nature. In all the solvents, a dual fluorescence is observed for both the compounds. The normal Stokes-shifted emission (B) originates from a locally excited π * electronic state, and the large Stokes-shifted band (A) is due to emission from a twisted intramolecular charge-transfer (TICT) state. The dual fluorescence observed, even in nonpolar solvents, indicates that the energy of the TICT state is always lower than that of the locally excited state
74 citations
TL;DR: The absorption and fluorescence spectra of 2-(2-aminophenyl)-, 2-(3-amino-polyethylene)-, and 2-(4-amphenyl)benzothiazoles (o-APBT, m-APB, and p-APBP, respectively) have been studied in different solvents and at various acid/base concentrations as mentioned in this paper.
Abstract: The absorption and fluorescence spectra of 2-(2-aminophenyl)-, 2-(3-aminophenyl)-, and 2-(4-aminophenyl)benzothiazoles (o-APBT, m-APBT, and p-APBT, respectively) have been studied in different solvents and at various acid/base concentrations. The ultraviolet and fluorescence spectra and the low pKa value for the monocation–neutral equilibrium have indicated the presence of an intramolecular hydrogen bond (IHB) in o-APBT in the S0 state. Excited state intra-molecular proton transfer (ESIPT) in o-APBT, gives rise to a non-fluorescent phototautomer. Large solvatochromic shifts in polar solvents have indicated the increase in the dipolemoment of m-APBT in S1 state. It has been observed that in protic solvents, m-APBT forms a complex with solvent molecule in the S1 state. The equilibrium constants for different prototropic equilibria of the molecules have been determined in both S0 and S1 states. The absorption and fluorescence spectra of the prototropic species have been explained and compared with those of 2...
72 citations
TL;DR: The solvent and pH dependence of the absorption and fluorescence of 2-(2′-hydroxyphenyl)benzoxazole was studied in this paper, where four different species were observed in both ground and excited states: the anion, the neutral molecule with intramolecular hydrogen bonding, the monocation and the dication.
Abstract: The solvent and pH dependence of the absorption and fluorescence of 2-(2′-hydroxyphenyl)benzoxazole was studied. Four different species were observed in both ground and excited states: the anion, the neutral molecule with intramolecular hydrogen bonding, the monocation and the dication. The PKa and PKa* were calculated by absorptiometric and fluorometic titrations respectively.
66 citations
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TL;DR: Recent studies on advanced ESIPT molecules and their optoelectronic applications are surveyed, particularly focusing on chemical sensors, fluorescence imaging, proton transfer lasers, and organic light-emitting diodes (OLEDs).
Abstract: Recently, organic fluorescent molecules harnessing the excited-state intramolecular proton transfer (ESIPT) process are drawing great attention due to their unique photophysical properties which facilitate novel optoelectronic applications. After a brief introduction to the ESIPT process and related photo-physical properties, molecular design strategies towards tailored emission are discussed in relation to their theoretical aspects. Subsequently, recent studies on advanced ESIPT molecules and their optoelectronic applications are surveyed, particularly focusing on chemical sensors, fluorescence imaging, proton transfer lasers, and organic light-emitting diodes (OLEDs).
931 citations
TL;DR: Fluorescent Dyes and Their Supramolecular Host/Guest Complexes with Macrocycles in Aqueous Solution and how these complexes interact with each other and with solvent-free substrates is studied.
Abstract: Fluorescent Dyes and Their Supramolecular Host/Guest Complexes with Macrocycles in Aqueous Solution Roy N. Dsouza, Uwe Pischel,* and Werner M. Nau* School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany Centro de Investigaci on en Química Sostenible (CIQSO) and Departamento de Ingeniería Química, Química Física y Química Org anica, Universidad de Huelva, Campus de El Carmen s/n, E-21071 Huelva, Spain
897 citations
TL;DR: In this paper, the intrinsic processes and mechanisms of proton transfer in relation to the nature of the intramolecular hydrogen bond ring are reviewed. But the authors focus on the intrinsic process and not the mechanisms of transfer.
Abstract: Excited-state intramolecular proton transfer reactions are reviewed. Special emphasis is given to the intrinsic processes and to the mechanisms of proton transfers in relation to the nature of the intramolecular hydrogen bond ring.
647 citations
TL;DR: Theoretical models that have been proposed and applied to proton transfer reactions are reviewed in this paper, where simple models, like the Eigen model, Marcus theory and the intersecting state model, are applied to excited-state intermolecular proton transfers.
Abstract: Theoretical models that have been proposed and applied to proton transfer reactions are reviewed in this work. Simple models, like the Eigen model, Marcus theory and the intersecting state model, are applied to excited-state intermolecular proton transfers. The kinetics and thermodynamics of proton transfers occuring in the singlet states of aromatic molecules with OH, NH3+, NH2 and CO substituents are reviewed.
507 citations
01 Jan 1991
TL;DR: In this article, a review on vibrational and vibronic relaxation of large molecules in liquids is presented, where femtoand picosecond spectroscopy of the intramolecular redistribution and the intermolecular energy transfer from vibrationally hot molecules to their (cold) surrounding is discussed.
Abstract: Vibrational and vibronic relaxation and related energy redistribution play an important role in many photoinduced processes of molecules. In the condensed phase, in which collision-induced relaxation is of particular relevance, these phenomena occur on a very rapid time scale between several tens of femtoseconds and 100 ps (1, 2). Spectroscopy with ultrashort laser pulses has been widely applied to elucidate the dynamics and physical mechanisms of intraand intermolecular energy redistribution (3, 4). Indeed, time resolved experiments have provided extensive information not accessible by other experimental techniques. In this article, we present a review on vibrational and vibronic relaxation of large molecules in liquids. Photoinduced redistribution processes of molecules, which consist typically of 20 or more atoms, are considered. We discuss. femtoand picosecond spectroscopy of the intramolecular redistribution and the intermolecular energy transfer from vibrationally hot molecules to their (cold) surrounding. We focus on measurements of vibrational and vibronic lifetimes, as well as on studies of energy redis tribution and transport. However, we will not consider dephasing of vibranic or vibrational states, relaxation processes connected to the
424 citations