Structure and reaction dynamics in gas phase solute-solvent heteroclusters

我们进行了以下两个项目，并获得了一些有趣的结果。(1)研究了与乙腈（ACN）， BA-(ACN)_n（n=1-5）气相团簇中9,9′-双苯基（BA）的电子激发态动力学。测量了大量选择双色共振增强多光子电离（REMPI）光谱，以确定BA簇的吸收带与乙腈分子的特定数量。测定了BA-(ACN)_n簇中BA的分散荧光（DF）光谱和寿命，研究了BA-(ACN)_n簇中BA的激发态动力学。与未聚集的BA相比，所有研究的星团的DF光谱都很宽，而且红移很大。BA在团簇中的荧光寿命明显长于非团簇BA。这些结果表明，BA在团簇中的光激发态转变为极性激发态，类似于BA在乙腈溶液中的扭曲分子内电荷转移（TICT）态。BA-(ACN)_1的Stokes位移和寿命表明，加入一个乙腈就可以发生电荷转移反应。然而，在乙腈溶液中，大团簇的这两种性质并没有表现出单调的变化。这些结果表明团簇的结构和动力学在电荷转移反应中起着重要的作用。(2)将激光诱导荧光技术应用于电喷涂细胞色素c （cyt-c）。中性pH溶液的电喷雾未观察到荧光，醋酸酸化溶液的电喷雾则观察到色氨酸残留的荧光。观察到酸化的cyt-c荧光的相对强度随着距离喷射针末端的距离而增加。这一结果表明，色氨酸残留物在电喷雾中由于溶剂分子的损失而变得更具荧光性。这表明，在电喷雾中，高电荷的cyt-c离子在溶液中保持非荧光致密形式，使其在溶剂的损失下发生构象变化而变成荧光。少

We have carried out the following two projects and obtained some interesting results.(1)Dynamics of the electronically excited state of 9,9'-bianthryl(BA) was studied in gas-phase clusters with acetonitrile (ACN), BA-(ACN)_n(n=1-5). The mass-selected two-color resonance-enhanced multiphoton ionization (REMPI) spectra were measured to determine the absorption band for the cluster of BA with the specific number of the acetonitrile molecules. The dispersed fluorescence (DF) spectra and lifetimes were measured for these absorption bands to study the dynamics of the excited state of BA in the clusters, BA-(ACN)_n. For all clusters studied, the DF spectra were broad and largely red shifted compared with that of unclustered BA. The fluorescence lifetimes of BA in the clusters were considerably longer than that of unclustered BA. These results suggested that the photoexcited state of BA in the clusters change to the polar excited state which is analogous to the twisted intramolecular charge tr … More ansfer (TICT) state of BA in the acetonitrile solution. Stokes shift and lifetime of the BA-(ACN)_1 suggested that the charge-transfer reaction becomes possible by adding one acetonitrile. However, these two properties of the larger clusters did not show monotonic change toward those of BA in acetonitrile solution. These results implied that the structure and dynamics of the clusters play some important roles in the charge-transfer reaction.(2)The laser-induced fluorescence technique is applied to electrosprayed cytochrome c (cyt-c). While no fluorescence was observed for the electrospray of the solution of neutral pH, the fluorescence ascribed to the tryptophane residue was observed for the spray of the acidified solution by acetic acid. The relative intensity of the fluorescence from the acidified cyt-c is observed to increase with the distance from the end of the spray needle. This result indicates that the tryptophane residue becomes more fluorescent by the loss of solvent molecules in the electrospray. It is suggested that the highly charged cyt-c ions which preserve the nonfluorescent compact forms in solution make a conformational change by the loss of solvent in the electrospray and become fluorescent. Less