Investigation of pyrromethene dyes in the presence of quinones by transient absorption spectroscopy

CHED 995

Nathaniel C. Brandt, ncbrandt@stthomas.edu and Joseph M. Brom, jmbrom@stthomas.edu. Department of Chemistry, University of St. Thomas, 2115 Summit Avenue, St. Paul, MN 55105
Pyrromethene (PM) dyes enjoy important applications in dye lasers and luminescent materials and are suspected to undergo a variety of photoinduced electron transfer processes due to their ability to undergo both oxidative and reductive processes from the excited state. For additional evidence of oxidative quenching mechanisms systems of PM dyes in the presence of electron accepting quinones were studied via transient absorption spectroscopy in order to characterize the radical ion products expected for these mechanisms. Spectroscopic investigations of PM567 dye in the presence of benzoquinone, naphthoquinone, anthraquinone, chloranil, and duroquinone yielded consistent spectroscopic evidence of the PM567 radical cation at 410nm as well as photobleaching of the PM567 ground state above 470nm. Absorptions corresponding to quinone radical anions and possibly semiquinone radicals were also observed concomitantly with PM567 radical species.