Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
J Phys Chem A. 2011 Oct 13;115(40):10962-71. doi: 10.1021/jp206176p. Epub 2011 Sep 21.
Steady-state and time-resolved techniques were employed to study the nonradiative process of curcumin dissolved in ethanol and 1-propanol in a wide range of temperatures. We found that the nonradiative rate constants at temperatures between 175-250 K qualitatively follow the same trend as the dielectric relaxation times of both neat solvents. We attribute the nonradiative process to solvent-controlled proton transfer. We also found a kinetic isotope effect on the nonradiative process rate constant of ~2. We propose a model in which the excited-state proton transfer breaks the planar hexagonal structure of the keto-enol center of the molecule. This, in turn, enhances the nonradiative process driven by the twist angle between the two phenol moieties.
稳态和时间分辨技术被用于研究在很宽的温度范围内溶解在乙醇和 1-丙醇中的姜黄素的非辐射过程。我们发现，在 175-250 K 温度范围内，非辐射速率常数定性上遵循与两种纯溶剂的介电弛豫时间相同的趋势。我们将非辐射过程归因于溶剂控制的质子转移。我们还发现非辐射过程速率常数的动力学同位素效应约为 2。我们提出了一个模型，其中激发态质子转移打破了分子中酮-烯醇中心的平面六方结构。反过来，这增强了由两个苯酚部分之间的扭转角驱动的非辐射过程。
