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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical study on the singlet excited state of pterin and its deactivation pathway
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Theoretical study on the singlet excited state of pterin and its deactivation pathway

机译：蝶呤单线态激发态及其失活途径的理论研究

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摘要

The excited-state properties and related photophysical processes of the acidic and basic forms of pterin have been investigated by the density functional theory and ab initio methodologies. The solvent effects on the low-lying states have been estimated by the polarized continuum model and combined QM/MM calculations. Calculations reveal that the observed two strong absorptions arise from the strong pi -> pi* transitions to (1)(pi pi*L-a) and (1)(pi pi*L-b) in the acidic and basic forms of pterin. The first excited state is exclusively responsible for the experimental emission band. The vertical (1)(n(N)pi*) state with a small oscillator strength, slightly higher in energy than the (1)(pi pi*L-a) state, is less accessible by the direct electronic transition. The (1)(n(N)pi*) state may be involved in the photophysical process of the excited pterin via the (1)(pi pi*L-a(N)pi*) conical intersection. The radiationless decay of the excited PT to the ground state experiences a barrier of 13.8 kcal/ mol for the acidic form to reach the (S-1/S-0) conical intersection. Such internal conversion can be enhanced with the increase in excitation energy, which will reduce the fluorescence intensity as observed experimentally.
机译：通过密度泛函理论和从头算方法研究了蝶呤的酸性和碱性形式的激发态性质和相关的光物理过程。极化连续体模型和QM / MM组合计算已评估了溶剂对低洼状态的影响。计算表明，观察到的两个强烈吸收来自于在蝶呤的酸性和碱性形式下向（1）（pi pi * L-a）和（1）（pi pi * L-b）的强pi-> pi *跃迁。第一激发态专门负责实验发射带。垂直（1）（n（N）pi *）状态具有较小的振荡器强度，能量比（1）（pi pi * L-a）状态稍高，因此直接电子跃迁较难访问。 （1）（n（N）pi *）状态可能通过（1）（pi pi * L-a / n（N）pi *）锥形交点参与激发的蝶呤的光物理过程。激发的PT到基态的无辐射衰减经历了13.8 kcal / mol的势垒，从而使酸性形式到达（S-1 / S-0）圆锥形相交点。这种内部转化可以随着激发能的增加而增强，这将降低实验观察到的荧光强度。

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