Excited-state intermolecular proton transfer of the firefly's chromophore D-luciferin. 2. Water-methanol mixtures.
Steady-state emission and time-resolved techniques were employed to study the photoprotolytic processes d-luciferin undergoes in water-methanol mixtures over a wide range of molar fractions (chi(MeOH)) of methanol. We found that in the concentration range of 0 < chi(MeOH) < 0.8 the rate constant of the excited-state proton transfer (ESPT) to the solvent decreases nearly exponentially with increasing chi(MeOH). At chi(MeOH) > 0.8 the proton transfer rate constant decreases with an even steeper slope. The kinetic isotope effect (KIE) maintains a constant value of 2.4 +/- 0.2 at all the mixture's compositions.
Presiado
Itay
I
Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
Erez
Yuval
Y
Huppert
Dan
D
D000818:Animals; D052160:Benzothiazoles / Q000737:chemistry*; D048888:Fireflies / Q000737:chemistry; D007700:Kinetics; D000432:Methanol / Q000737:chemistry*; D015394:Molecular Structure; D010777:Photochemistry; D011522:Protons; D011721:Pyrenes / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry; D013997:Time Factors; D014867:Water / Q000737:chemistry*
C538892:8-hydroxy-1,3,6-pyrenetrisulfonic acid; D052160:Benzothiazoles; C532924:D-luciferin; D011522:Protons; D011721:Pyrenes; D013451:Sulfonic Acids; D014867:Water; D000432:Methanol