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Indian Institute of Science

1. Pandey, Rishikesh. Understanding Solvent Effect On Triplet State Structure Of Thioxanthone And Its Derivatives Using Time-Resolved Resonance Raman Spectroscopy.

Degree: PhD, Faculty of Science, 2014, Indian Institute of Science

It has long been recognized that course and efficiency of a chemical reaction is largely mediated by the short-lived transient species (excited state or radicals) which are formed as reactive intermediates during a chemical reaction. Subtle changes not only in the bonding and electronic distributions but also in the conformations and geometries of these intermediates have a dramatic influence on the reactivity. A detailed understanding of the structural and dynamical aspects of electronic excited states is therefore essential towards unraveling photoinduced natural processes and for designing novel photonic materials. Time-resolved techniques have been widely used to study the transient species (or intermediates) formed during photochemical and photophysical reactions for better understanding of the reaction mechanism and dynamics. Time-resolved absorption spectroscopy is a promising tool to study the temporal dynamics and the kinetics of photophysical processes. But the absorption spectra of species in solution usually consist of broad spectral band revealing little or no information about the structure of the transient species under investigation. Time-resolved resonance Raman (TR3) spectroscopy, on the other hand, is a potential sensitive modality, which not only allows one to study the dynamics but also provides the vibrational structure of the transient species of interest in microsecond to picosecond time scale. Moreover, by choosing the wavelength of excitation one can selectively probe the particular transient species from a complex molecular system especially a biological molecule. Thioxanthone (TX) is well known for its dramatic solvatochromic behavior and has drawn enormous attention in the recent years. The objective of present thesis has been to understand the solvent-induced structural changes on the lowest excited triplet state of TX and its derivatives. We have primarily employed nanosecond TR3 spectroscopy, a pump-probe technique, to investigate structure of the lowest excited triplet state. Transient absorption experiments have also been carried out to study the excited electronic states. In order to substantiate our experimental findings and also to get more insight into the triplet-state structure, we have performed density functional theory (DFT) calculations. The polarizable continuum solvation model has been employed to account for the solvent effect into the computation. Time dependent (TD) -DFT calculations have also been performed to get the energy and the structure of the excited states. The present thesis has been divided into eight chapters. Chapter 1 gives brief literature review on photochemistry and photophysics of TX and the introduction to the TR3 technique. In this chapter we have briefly introduced key concepts which form the basis of the thesis. Chapter 2 covers the experimental and theoretical methodologies used in the present thesis work. The major components of the TR3 spectrometer as well as the important technical aspect of the TR3 technique have been discussed in detail.… Advisors/Committee Members: Umapathy, Siva (advisor).

Subjects/Keywords: Solvent Polarity Scale; Thioxanthone (TX); Time-Resolved Resonance Raman Spectroscopy; Ketones; Thioxanthone - Triplet State Structure; Thioxanthone - Photochemistry and Photophysics; Triplet State Structure; 2-chlorothioxanthone (CTX); Time-Resolved Resonance Raman Study; Physical Chemistry

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APA (6th Edition):

Pandey, R. (2014). Understanding Solvent Effect On Triplet State Structure Of Thioxanthone And Its Derivatives Using Time-Resolved Resonance Raman Spectroscopy. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2307

Chicago Manual of Style (16th Edition):

Pandey, Rishikesh. “Understanding Solvent Effect On Triplet State Structure Of Thioxanthone And Its Derivatives Using Time-Resolved Resonance Raman Spectroscopy.” 2014. Doctoral Dissertation, Indian Institute of Science. Accessed May 09, 2021. http://etd.iisc.ac.in/handle/2005/2307.

MLA Handbook (7th Edition):

Pandey, Rishikesh. “Understanding Solvent Effect On Triplet State Structure Of Thioxanthone And Its Derivatives Using Time-Resolved Resonance Raman Spectroscopy.” 2014. Web. 09 May 2021.

Vancouver:

Pandey R. Understanding Solvent Effect On Triplet State Structure Of Thioxanthone And Its Derivatives Using Time-Resolved Resonance Raman Spectroscopy. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2014. [cited 2021 May 09]. Available from: http://etd.iisc.ac.in/handle/2005/2307.

Council of Science Editors:

Pandey R. Understanding Solvent Effect On Triplet State Structure Of Thioxanthone And Its Derivatives Using Time-Resolved Resonance Raman Spectroscopy. [Doctoral Dissertation]. Indian Institute of Science; 2014. Available from: http://etd.iisc.ac.in/handle/2005/2307

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