Radiationless deactivation of 6-aminocoumarin from the S1-ICT state in nonspecifically interacting solvents

Photochem Photobiol Sci. 2012 Aug;11(8):1322-30. doi: 10.1039/c2pp25065a. Epub 2012 May 24.

Abstract

This paper presents the results of a spectral (absorption and emission) and photophysical study of 6-aminocoumarin (6AC) in the solvents with which this molecule interacts only nonspecifically (n-alkanes, tetrachloromethane and 1-chloro-n-alkanes) and in nitriles. The strong effects of the solvents on the emission spectra, fluorescence quantum yield and lifetime of 6AC were observed. The results of the steady-state and time-resolved photophysical study suggest the presence of very fast nonradiative deactivation processes. It is concluded that besides fluorescence, the efficient S(1)-ICT → S(0) internal conversion in nonpolar aprotic solvents arises from vibronic interactions between close-lying S(1)-ICT(π,π*) and S(2)(n,π*) states. Moreover, unexpectedly efficient triplet state formation occurs. In nitriles the intermolecular hydrogen-bonding interactions with solvent molecules also facilitate the nonradiative decay process involving the S(1)-exciplex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Absorption
  • Coumarins / chemistry*
  • Electron Transport
  • Solvents / chemistry*
  • Spectrometry, Fluorescence

Substances

  • Coumarins
  • Solvents
  • 6-amino-1,2-benzopyrone