Dynamics of internal rotation related to the intramolecular charge-t transfer reactions

本项目的目的是确定能够形成分子内电荷转移(CT)态的化合物的内旋转势，然后在扭转反应坐标系下观察CT态形成的动力学。对以下主题进行了广泛的研究1。测定了9，9‘-联菲(BA)-稀有气体和BA-Ar络合物的内旋转势能面。在He络合物中，小的微扰使简并的扭曲能级轻微分裂，而在Ar和O络合物中，势能的形状发生了很大的变化，双势垒势中的一个势垒消失了。BA络合物的时间分辨荧光BA-Ar络合物只发出S_1激发态的荧光，而BA-H_2O络合物既有S_1激发态的荧光，又有CT激发态的荧光。BA-Ar荧光的时间分布与…无关观察到更多的波长，这可能表明IVR在检测系统的时间分辨率内是快速的。BA-H_2O络合物的时间分布具有波长依赖性，当激发波长为375 nm时，在10ps内衰减非常迅速，而在380 nm时，随着时间常数的增加，BA-H_2O络合物的时间分布先增大后减小。CT荧光强度随20ps上升时间的延长而增加。这一行为表明中间状态的存在，该中间状态可能可分配给振动热CT状态3。用时间分辨荧光耗尽(TRFD)方法观察了BA-Ar和BA-H_2O络合物激发态的快速脱相过程。在BA-Ar络合物中，观察到的10ps的退相对应于分子内振动能的重新分配，而在BA-H_2O络合物中，观察到的6ps的退相时间可以归因于IVR态和CT态的形成。根据PS激发产生的波函数的时间演化，模拟了BA-H2O络合物中同时发生的IVR和CT态形成的动态过程。观察到的行为得到了很好的重现。较少

The aim of this project is to determine the internal rotation potentials of the compounds capable of forming an intramolecular charge-transfer (CT) state and then to observe the dynamics of the CT state formation on the twisting reaction coordinate. The following topics have been extensively studied1. Determination of the potential energy surface of internal rotationThe potential energy surfaces for the internal rotation of 9,9'-bianthryl (BA) -rare gas and BA-Ar complexes were determined. In a He complex the small perturbation slightly splits the degenerate twisting levels whereas in Ar and O complexes the shape of the potential is drastically changed ; one well of the double well potential disappears.2. The time-resolved fluorescence of BA complexesThe BA-Ar complex only emits the fluorescence from the excited S_1 state whereas the BA-H_2 O complex gives the fluorescence from both the S_1 and the CT states. The time profile of the BA-Ar fluorescence was found to be independent of the … More wavelength observed, which probably indicated the rapid IVR within the time resolution of the detecting system. On the other hand, the time profile of the BA-H_2O complex showed the wavelength dependence ; at the excitation wavelength 375 nm), it decayd very rapidly within 10 ps whereas at 380nm it increased first and then decreased with the time constant of 20 ps. The CT fluorescence increased with 20 ps rise time. This behavior indicates the presence of the intermediate state which probably be assignable to the vibarationally hot CT state3. The observation of the relaxation processes with the time-resolved fluorescence depletion (TRFD) methodWith the TRFD method, the rapid dephasing processes of the excited state of BA-Ar and BA-H_2O complexes have been observed. In the BA-Ar complexes, the observed dephasing of 10 ps corresponded to the intramolecular vibrational energy redistribution whereas in BA-H_2O complexes the observed 6 ps dephasing time could be attributed to both the IVR and CT state formation.4. A simulation of the dynamic processesThe simultaneously occurring IVR and CT state formation in the BA-H2O complexes was simulated in terms of the time-evolution of the wavefunction prepared by the ps excitation. The observed behavior was well reproduced. Less