Study on Microscopic Solvation Effects on Nonradiative Processes

本研究旨在通过对含有芳香族生色团的溶剂化簇合物的实验研究，阐明芳香族分子中的非辐射过程如何以及为什么会受到其周围溶剂的影响。通过应用多种光谱方法，即多重激光共振、质量选择光电离和超快激光光谱，我们取得了以下结果：1.研究了吖啶和9-吖啶酮的水合簇合物，探讨了氢键网络中的结构基序和生色团中的非辐射过程之间的分子水平上的关联。通过比较实验数据(电子跃迁和荧光红外光谱)和密度泛函理论计算，确定了水合物的几何构型。皮秒时间分辨测量表明，荧光寿命在很大程度上取决于团簇大小和氢键位置。Microsco…更多的PIC溶剂化效应被解释为与(n，π^*)和(π，π^*)态密切相关的能量学，这两个态被氢键移动。2.重新研究了单体S_1-S_0区苯团簇的电子跃迁。根据对不同同位素物种的二聚体和三聚体离子通道记录的质量选择烧孔光谱的详细检查，已经发现20年来被接受的以前的大小分配需要修正。对苯三聚体和四聚体提出了新的指认，解决了迄今报道的实验结果和理论结果之间的矛盾。这些数据还提供了团簇的几何和激发交换相互作用的信息。3.用皮秒时间分辨泵浦-探测耗尽的旋转相干谱确定了含9-氰基菲的溶剂化团簇的几何结构。特别是首次建立了二氧化碳、乙腈、氟仿等非质子型溶剂分子的结构基元，为进一步探讨氰基芳烃簇合物的反应动力学与溶剂化结构之间的关系奠定了坚实的基础。较少

The present research project aims to clarifying how and why nonradiative processes in aromatic molecules are influenced by solvents surrounding them through experimental investigations on solvated clusters containing aromatic chromophores. By applying various spectroscopic methods, i.e., multiple laser resonances, massselective photoionization, and ultrafast laser spectroscopy, the following results have been achieved.1.Hydrated clusters of acridine and 9-acridone have been studied to explore molecular-level correlation between structural motifs in hydrogen-bonding networks and nonradiative processes in the chromophores. Geometries of the hydrates have been determined by comparison of experimental data(band shifts in electronic transitions and fluorescence-detected infrared spectra)with density-functional-theory calculations. Pico-second time-resolved measurements have shown that fluorescence lifetimes depend substantially on cluster sizes as well as hydrogenbonding sites. The microsco … More pic solvation effects have been explained in terms of energetics relating to closely lying(n, π^*)and(π, π^*)states, which are characteristically shifted by hydrogen bonds.2.Electronic transitions of benzene clusters in the monomer S_1-S_0 region have been reinvestigated. It has been found that previous size-assignments accepted for two decades need to be corrected, based on detailed examination of mass-selective holeburing spectra recorded for various isotopic species of dimer and trimer ion channels. New assignments have been proposed for the benzene trimer and tetramer, which resolve contradictions between experimental and theoretical results reported so far. The present data also provide information on geometry and excitation exchange interactions of the clusters.3.Geometrical structure of solvated clusters containing 9-cyanoanthracene has been determined by rotational coherence spectroscopy implemented with pico-second time-resolved pump-probe depletion. In particular, structral motif for aprotic solvent molecules, e.g., carbon dioxide, acetonitrile, and fluoroform, has been established for the first time, which will be a solid foundation for discussing the relationship between reaction dynamics and solvation structure in clusters of related cyano-aromatics. Less