Photophysical characterization of cinnamates
Journal article, 2009

The photophysical properties of five methoxy-substituted 2-ethylhexylcinnamates were studied with experimental and theoretical methods. It was found that the fluorescence quantum yields varied strongly with the substitution pattern of the phenyl ring. A methoxy substitution at the meta position gave strong fluorescence, whereas the para substituted compounds were strongly quenched. This observation could be correlated to corresponding changes in the UV absorption spectra; the two lowest pi pi* states were split for the meta-methoxy substituted cinnamate but almost degenerate for the para compound. Semi-empirical quantum mechanical calculations confirmed both the observed state order and the difference in the experimentally determined activation energies for non-radiative decay. This "meta-effect" was also preserved in the trimethoxy-substituted compounds, 2-ethylhexyl-2,4,5- and 2,4,6-trimethoxycinnamate, resulting in strong fluorescence and relatively high barrier for non-radiative decay in the former and weak fluorescence and relatively low barrier for non-radiative decay in the latter. The obtained information shows how the performance of the commercial sunscreen agent, 2-ethylhexyl-para-methoxycinnamate (OMC) might be improved.

meta

molecules

photoisomerization

esters

photochemistry

Author

T. M. Karpkird

Kasetsart University

S. Wanichweacharungruang

Chulalongkorn University

Bo Albinsson

Chalmers, Chemical and Biological Engineering, Physical Chemistry

Photochemical and Photobiological Sciences

1474-905X (ISSN) 1474-9092 (eISSN)

Vol. 8 10 1455-1460

Subject Categories

Physical Chemistry

Chemical Sciences

DOI

10.1039/b909695g

More information

Created

10/6/2017