Time-resolved spectroscopic measurements on microscopic solvation dynamics

V. Nagarajan, Ann M Brearley, Tai Jong Kang, Paul F. Barbara

Research output: Contribution to journalArticlepeer-review

191 Scopus citations

Abstract

This paper reinvestigates the use of transient fluorescence spectroscopy of polar aromatics in solution as a method to determine microscopic solvation dynamics. It is shown that the compounds previously employed as polar fluorescent probes tend to fall into three photophysical classes depending upon: (i) whether the photon induced change in μ occurs simultaneously with photon absorption (ii) whether solvent motion subsequent to photon absorption is required to induce the change in μ; or (iii) whether two excited-state isomers with different μ's are present simultaneously. The consequence of the different classes on microscopic solvation dynamic measurements is discussed with a molecular example for each class: (i) 4-aminophthalimide, (ii) 4-(9-anthryl)-N,N-dimethylaniline, and (iii) bianthryl, respectively. In addition, we introduce a new transient fluorescence procedure for the determination of solvation dynamics that has advantages over the traditional transient Stokes-shift method. Finally, for the first time, extensive measurements on the solvation dynamics of a polar aprotic solvent have been made. The observed dynamics of the solvent (glycerol triacetate) are highly nonexponential; this has important implications for chemical reactions in similar solvents. Interestingly, the experimentally observed microscopic dynamics are in qualitative agreement with predictions of the dielectric continuum model.

Original languageEnglish (US)
Pages (from-to)3183-3196
Number of pages14
JournalThe Journal of chemical physics
Volume86
Issue number6
DOIs
StatePublished - 1987

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