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Photophysical characterization of cinnamates

T. M. Karpkird ; S. Wanichweacharungruang ; Bo Albinsson (Institutionen för kemi- och bioteknik, Fysikalisk kemi)
Photochemical & Photobiological Sciences (1474-905X). Vol. 8 (2009), 10, p. 1455-1460.
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: photoisomerization, photochemistry, molecules, esters, meta



Denna post skapades 2010-01-13. Senast ändrad 2010-04-27.
CPL Pubid: 107186

 

Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Fysikalisk kemi (2005-2014)

Ämnesområden

Kemi
Fysikalisk kemi

Chalmers infrastruktur