Effect of chlorine substitution on triplet state structure of thioxanthone: A time‐resolved resonance Raman study

Abstract

Substitution plays an important role in determining the triplet state reactivity. In this paper, we have studied the effect of chlorine substitution on the triplet state structure and the reactivity of thioxanthone (TX). We have employed time‐resolved resonance Raman technique to understand the structure of the lowest triplet excited state of 2‐chlorothioxanthone (CTX). The experimental findings have been corroborated with the computational results using density functional theory. Akin to the parent compound (TX), coexistence of two lowest triplet states has been observed in case of CTX, which has been substantiated using resonant probe wavelength dependence study. The relative contribution of 3n–π* to 3π–π* to the equilibrated triplet state has been found to be more for CTX compared to TX suggesting increase in the triplet state reactivity after the substitution. The above observation has been further supported by the flash photolysis experiments. Copyright © 2013 John Wiley & Sons, Ltd.

Recent advances in linear and nonlinear Raman spectroscopy. Part VIII

“…Pandey and coworkers used time‐resolved resonance Raman to study the effect of chlorine substitution on the triplet state structure of thioxanthone (TX). To accomplish this, the authors employed TRRR to understand the structure of the lowest triplet excited state of 2‐chlorothioxanthone (CTX) . Reigue et al .…”

“…To accomplish this, the authors employed TRRR to understand the structure of the lowest triplet excited state of 2-chlorothioxanthone (CTX). [165] Reigue et al reported CW measurements of resonance Raman profiles, line-widths, and cross sections of fluorescent dyes with application to Nile Blue A in water and ethanol. This study demonstrates the possibility of routine RRS measurements using standard Raman spectrometers, as opposed to more complicated time-resolved techniques.…”

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“…This enables Raman spectroscopy a highly specific probe providing unique chemical fingerprinting information. In other words two different molecules have two different Raman spectra; even an atomic substitution is known to affect the Raman spectrum of the parent molecule (13). The high specificity of the technique could be understood with the fact that same molecule in the different chemical environments (14) and even two polymorphic forms have different Raman signatures.…”

Solvent effects on the structure of the triplet excited state of xanthone: a time-resolved resonance Raman study

“…In this work, conventional Raman and time‐resolved resonance Raman spectroscopy (TR 3 ) techniques were used to examine the ground and the triplet excited states structure, respectively. TR 3 spectroscopy is a powerful technique to elucidate the vibrational structure of the transient species . When the Raman excitation wavelength is in resonance with an allowed electronic transition of the molecule, the Raman peaks coupled to the chromophore become enhanced, accounting for the high sensitivity and selectivity of the technique .…”

“…TR 3 spectroscopy is a powerful technique to elucidate the vibrational structure of the transient species. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] When the Raman excitation wavelength is in resonance with an allowed electronic transition of the molecule, the Raman peaks coupled to the chromophore become enhanced, accounting for the high sensitivity and selectivity of the technique. [49][50][51][52][53][54] Resonance Raman spectroscopy generally involves measurement of the Raman intensities of different modes as a function of wavelength, known as Raman excitation profiles (REPs).…”