Real-time probing of Energy Dissipation Processes in Solvated Clusters

本研究旨在通过超快时间分辨测量对溶剂化团簇中的能量耗散过程进行微观理解。由于对实验装置的改进，如真空室和激光系统的改进，得到了以下结果.第一：本文研究了9，9 ′-联蒽（BA）与水分子簇合物的扭转分子内电荷转移（TICT）反应，用激光诱导荧光法测定了BA在该簇合物中的扭转势。在集群中的电位是很大的不同，在单体中，表明相当大的修改在BA的电子特性的络合，以及BA和水之间的空间排斥。ps时间分辨荧光测量表明，TICT率没有明显的依赖于激发能或溶剂同位素取代。这个OB 关于我们 实验证实了TICT反应是通过“顺序”机制进行的;最初制备的能级主要耦合到具有扭转运动的高振动激发的中间能级，其进一步弛豫到电荷分离态的最终能级。这一结果表明了扭转运动在TICT反应动力学中的重要性.研究了9-吖啶酮（AD）水溶剂化簇合物的微观溶剂化效应，发现随着溶剂化级数的增加，体系间交叉（ISC）的荧光量子产率显著增加。通过JR-UV双共振光谱结合从头算分子轨道计算对AD的结构进行了表征，结果表明水分子与AD的C=O形成了1：1的氢键簇合物。这些结果验证了微溶剂化对ISC的位点选择性影响。少

The present research project aims to microscopic understanding on the energy dissipation processes in solvated clusters through ultrafast time-resolved measurements. Owing to the improvement in the experimental setup, such as the vacuum chambers and laser systems, the following results have been achieved.1. The 1 : 1 cluster of 9,9'-bianthryl (BA) with water has been studied for detailed characterization of the twisted intramolecular charge transfer (TICT) reaction in BA.The torsional potential of BA in the cluster has been determined form the laser-induced-fluorescence observation of the torsional progressions. The potential in the cluster is much different from that in the monomer, indicating considerable modification in the electronic character of BA by complexation, as well as steric repulsion between BA and water. The ps time-resolved fluorescence measurements have shown that the TICT rate has no appreciable dependence on excitation energy or solvent isotopic substitution. This ob … More servation confirms that the TICT reaction proceeds via "sequential" mechanism ; the initially prepared level is predominately coupled to intermediate levels with high vibrational excitation of torsional motion, which further relax to the final levels in the charge-separated state. This result demonstrates the importance of the torsional motion in the dynamics of TICT reactions.2. The water-solvated clusters of 9-acridone (AD) have been studied to explore the microscopic solvation effect on inter-system crossing (ISC) in AD.The fluorescence quantum yield is greatly enhanced with increasing order of solvation. Especially, drastic change with>200-fold increase caused by addition of only one water to the monomer indicates the crossover of the reaction mechanism form the direct ISC to the second-order ISC.Structural characterization by JR-UV double resonance spectroscopy combined with ab initio MO calculation has shown that water is hydrogen-bonded to C=O of AD in the 1 : 1 cluster. These results validates the site-selective microsolvation effect on ISC. Less