The Structure and Reactions of Large Clusters Studies by The Rotational Coherence Method

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Knowledge of structure of solvated cluster is essentially important to understand its intramolecular reaction in microscopic level. However, the difficulty of spectroscopic determination of big molecules like solvated clusters prevents us from relating intramolecular reactions of solvated clusters with their structure. The bigger a molecule is, the less advantageous is traditional high-resolution frequency spectroscopy to determine molecular structure. How the number and location of solvent molecules affect the rate of intramolecular charge transfer reaction is our main interest. We adopted rotational coherence spectroscopy as a tool to determine the structure of such clusters.Complexes between bianthryl and other solvent molecules have lower symmetry than the monomer. In addition, intramolecular charge transfer reaction involves large structural change causing the rotation of the principal axis. These facts prevent observing rotational coherence signals with time-correlated single-pho … More ton counting method, which measures the rotational level structure of electronically excited state. Therefore, the pump-probe method was applied to obtain structural information of evectronically ground state of water complex, which shows non-adiabatic transition to a charge transfer state via photoexcitation. After some efforts to obtain good stability of the amplification system of short pulse laser, we finally observed the rotational coherence signal of water complex with this method. Loss of the rotational coherence signal in electronically excited state and observation of the rotational coherence in the electronically ground state suggest a large structural change following intramolecular charge transfer. To perform this research, Prof.Kajimoto visited Oxford and Dr.Langford visited Kyoto.Other molecules cousing intramolecular charge transfer reaction even without clustering with polar solvent molecules, 4- (N,N-dimethylamino) ethylbenzoate (Oxford) and 4- (N,N-dimethylamino) -3,5-dimethylbenzonitrile (Kyoto) were also investigated. From the analysis of their structure, close relation between torsional potential and formation of charge transfer reaction is established. To perform this research, Prof.Simons visited Kyoto and Ms.Lee visited Oxford. Less