title: Photoprotolytic Processes of Lumazine.
abstract: Steady-state and time-resolved UV-vis spectroscopies were used to study the photoprotolytic properties of lumazine, which belongs to a class of biologically important compounds-the petridines. We found that in water an excited-state proton transfer occurs with a time constant of ∼70 ps and competes with a nonradiative rate of about the same value. The nonradiative rate of the protonated form of lumazine in polar and nonpolar solvents is large knr≥ 1.5 × 1010s-1. The fluorescence properties indicate that in water, the ground-state neutral form of lumazine is already stable in two tautomeric forms. The fluorescence of the deprotonated form is quenched by protons in acidic solutions with a diffusion-controlled reaction rate. We conclude that the neutral form of lumazine is an irreversible mild photoacid.
authors.affiliation: Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University , Tel Aviv 69978, Israel.
authors.forename: Ron
authors.initials: R
authors.lastname: Simkovitch
authors.affiliation: Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University , Tel Aviv 69978, Israel.
authors.forename: Dan
authors.identifier: 0000-0002-0292-4106
authors.initials: D
authors.lastname: Huppert
mesh_terms: D015394:Molecular Structure; D010782:Photolysis; D011621:Pteridines / Q000737:chemistry*
chemical_list: D011621:Pteridines; C008297:lumazine