Liquid crystalline solvents as mechanistic probes. 9. Dynamics of intramolecular fluorescence quenching processes of N,N-dimethyl-4-[3-(1-pyrenyl)propyl]aniline in the liquid crystalline and isotropic phases of a cholesteric solvent

V. C. Anderson, B. B. Craig, R. G. Weiss

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

The dynamics of the intramolecular quenching of pyrene singlet (1P) fluorescence by an aromatic amino group in N,N-dimethyl-4-[3-(1-pyrenyl)propyl]aniline (A) have been investigated in a nonpolar, cholesteric liquid crystalline solvent [59.5/15.6/24.9 (w/w/w) cholesteryl oleate/cholesteryl nonanoate/cholesteryl chloride]. The disappearance of the 1P fluorescence is shown to correlate kinetically with the formation of a fluorescent exciplex state. The monoexponential 1P emission decay disfavors the existence of energetically distinct ground-state conformers of A. Employing 1-ethylpyrene as a model compound allows determination of rate constants and activation parameters for the intramolecular 1P quenching process. The small differences in the activation parameters [E6′(cholesteric) = 9.7 ± 1.2 kcal mol-1 and E6′(isotropic) = 7.8 ± 0.3 kcal mol-1; ΔS(cholesteric) = 3 ± 3 eu and ΔS(isotropic) = -4 ± 1 eu] suggest that cholesteric order has little effect on the quenching efficiency. A mechanistic explanation is advanced.

Original languageEnglish (US)
Pages (from-to)4642-4648
Number of pages7
JournalJournal of Physical Chemistry
Volume86
Issue number23
DOIs
StatePublished - Jan 1 1982

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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