Gj. Smith et Ij. Miller, THE EFFECT OF MOLECULAR ENVIRONMENT ON THE PHOTOCHEMISTRY OF P-METHOXYCINNAMIC ACID AND ITS ESTERS, Journal of photochemistry and photobiology. A, Chemistry, 118(2), 1998, pp. 93-97
In addition to rapid, reversible trans-cis photoisomerisation, air-sat
urated solutions of p-methoxycinnamic acid and 2-ethylhexyl-p-methoxyc
innamate in polar solvents undergo a slower, irreversible photoreactio
n when exposed to ultraviolet radiation. However, no such reaction is
evident in polar solvents that are deoxygenated or in air-saturated, n
on-polar solvents. The fluorescence spectra were also dependent on the
solvent polarity with a shift to longer wavelengths in polar solvents
. This behaviour suggests a degree of charge transfer character in the
lowest excited singlet state responsible for fluorescence in a polar
molecular environment. The fluorescence yields of solutions of these c
innamoyl molecules were low, less than or equal to 1.6 x 10(-3), indic
ating that there are very efficient non-radiative pathway/s for nonrad
iative relaxation of the excited singlet states of these molecules. (C
) 1998 Elsevier Science S.A. All rights reserved.