The effect of a mild base on curcumin in methanol and ethanol.
Steady-state and time-resolved emission techniques were employed to study the effect of acetate, a mild base, on the luminescence of curcumin in methanol and ethanol. We found that the steady-state emission intensity as well as the average fluorescence decay time are reduced by a factor of 5 when the acetate concentration is raised to about 1.8 M. We attribute this large effect to an excited-state proton transfer (ESPT) from the acidic groups of curcumin to the acetate anion. We analyze the experimental data in terms of an ESPT reaction occurring between a photoacid and a base.
Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv, Israel.
Yuval
Y
Erez
Itay
I
Presiado
Rinat
R
Gepshtein
Dan
D
Huppert
D003474:Curcumin / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D000432:Methanol / Q000737:chemistry*; D015394:Molecular Structure; D019347:Potassium Acetate / Q000737:chemistry
D000431:Ethanol; D003474:Curcumin; D019347:Potassium Acetate; D000432:Methanol