Department of Molecular Engineering, Kyoto University, Kyoto Daigaku Katsura, Kyoto 615-8510, Japan.
J Phys Chem B. 2013 Jun 6;117(22):6759-67. doi: 10.1021/jp311883f. Epub 2013 May 22.
An excited-state intramolecular proton transfer (ESIPT) reaction of 4'-N,N-dimethylamino-3-hydroxyflavone in room temperature ionic liquid is theoretically investigated using RISM-SCF-SEDD, which is a hybrid method of molecular liquid theory and ab initio molecular orbital theory. The photo-excitation and proton-transfer processes are computed by considering the solvent fluctuation. The calculated absorption and emission energy are in good agreement with the experiments. The changes in the dipole moment indicate that the drastic solvation relaxation is accompanied by the excitation and an ESIPT process, which is consistent with the remarkable dynamic Stokes shift observed in the experiments. We calculated the nonequilibrium free-energy contour as a function of the proton coordinate and the solvation coordinate. We conclude that although immediately after the excitation the barrier height of the ESIPT process is relatively small, the barrier becomes larger as the solvation relaxation to the excited normal state proceeds. The solvation relaxation process is also investigated on the basis of microscopic solvation structure obtained by RISM calculations.
室温离子液体中 4'-N,N-二甲基氨基-3-羟基黄酮的激发态分子内质子转移 (ESIPT) 反应，使用 RISM-SCF-SEDD 进行了理论研究，该方法是分子液体理论和从头算分子轨道理论的混合方法。通过考虑溶剂波动，计算了光激发和质子转移过程。计算的吸收和发射能量与实验很好地吻合。偶极矩的变化表明，剧烈的溶剂弛豫伴随着激发和 ESIPT 过程，这与实验中观察到的显著动态斯托克斯位移一致。我们计算了质子坐标和溶剂坐标的非平衡自由能轮廓。我们得出的结论是，尽管在激发后，ESIPT 过程的势垒高度相对较小，但随着溶剂弛豫到激发的正常状态的进行，势垒会变大。还根据通过 RISM 计算获得的微观溶剂结构研究了溶剂弛豫过程。
