Fluorescence quenching of pyrromethene 546

CHED 984

Amanda Hixon, amanda.k.hixon@gmail.com and Joseph M. Brom, jmbrom@stthomas.edu. Department of Chemistry, University of St. Thomas, 2115 Summit Ave, #5152, St. Paul, MN 55105

Pyrromethene 546 (PM546) is a laser dye that possesses a very high fluorescence quantum yield.  When a quencher is put into solution with the PM546, the fluorescence intensity is reduced.  These intensities are measured and compared at varying quencher concentrations in PM546 solutions.  Applying the Stern-Volmer equation to these intensities, the Stern-Volmer quenching constant, KSV, can be determined.  The larger the KSV value, the better the quencher. PM546 in its excited state can act as either an electron donor or an electron acceptor.  By using well known electron-donating or electron-accepting quenchers the KSV values can be determined and compared.  The KSV values for the electron-donating quenchers were extremely small when compared to the KSV values for the electron-accepting quenchers.  This shows that although PM546 can act as either an electron donor or an electron acceptor, it is more apt to act as an electron donor.