Consequences of strong coupling between solvation and electronic structure in the excited state of a betaine dye
Consequences of strong coupling between solvation and electronic structure in the excited state of a betaine dye
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DOI：
10.1021/jp801660b
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发表时间：
2008-09-11
影响因子：
3.3
通讯作者：
Rossky, Peter J.
中科院分区：
文献类型：
--
作者：
Ishida, Tateki;Rossky, Peter J.
在CASSCF框架下，采用参考相互作用位点模型自洽场（RISM-SCF）方法，研究了甜菜碱染料分子吡啶-N-苯酚盐[4-（1-吡啶基）苯酚盐]在气相和水溶液中的电子基态和激发态结构.我们得到的总自由能分布在基态和激发态相对于酚盐和吡啶环之间的扭转角的变化。分析了溶剂对溶质分子偶极矩变化的影响，以及激发态电荷转移的性质。在气相中，它示出的激发态的势能曲线单调地减少朝向垂直环取向和偶极矩沿着减少电荷本地化。在水中，扭曲的自由能表面更好地表征为对于空间可达角沿着沿着相同坐标的几乎平坦的。这些结果进行了分析的贡献的溶剂化自由能，溶质的电子能量，以及它们的耦合。相应地，电荷转移特性的溶质几何和溶剂化的依赖性进行了分析，甜菜碱染料的激发和随后的弛豫过程中的重要作用进行了讨论。结果发现，有相当大的溶质电子重组与溶剂化的激发态的演变，它是建议，这种重组可能有助于显着的瞬态光谱的早期演化光激发。
The electronic ground and excited-state structures of the betaine dye molecule pyridinium-N-phenoxide [4-(1-pyridinio)phenolate] are investigated both in the gas phase and in aqueous solution, using the reference interaction site model self-consistent-field (RISM-SCF) procedure within a CASSCF framework. We obtain the total free energy profiles in both the ground and excited states with respect to variation in the torsion angle between the phenoxide and pyridinium rings. We analyze the effect of solvent on the variation of the Solute dipole moment and oil the charge transfer character in the excited state. In the gas phase, it is shown that the potential energy profile in the excited-state decreases monotonically toward a perpendicular ring orientation and the dipole moment decreases along with decreasing charge localization. In water, the free energy surface for twisting is better characterized as nearly flat along the same coordinate for sterically accessible angles. These results are analyzed in terms of contributions of the solvation free energy, the solute electronic energy, and their coupling. Correspondingly, the dependence of the charge transfer character on Solute geometry and solvation are analyzed, and the important roles in the excitation and subsequent relaxation processes for the betaine dye are discussed. It is found that there is considerable solute electronic reorganization associated with the evolution of solvation in the excited state, and it is suggested that this reorganization may contribute significantly to the early time evolution of transient spectra following photoexcitation.