Date: 2009. 6. 16, 5:00 PM Place: Rm. 404, Bldg 503 -Abstract- Hydrogen-bonded networks are important in biological systems. For example, it is known that the binding of water molecules in enzymes remarkably lowers prton/hydrogen transfer potential barrier, where the water molecules play a catalytic role to generate biological functions. However, proton/hydrogen transfer reactions in biomolecules are too complicated to clarify the dynamics. The investigation of proton/hydrogen transfer reactions in a good model system is important to understand the nature and the dynamics occuring in the hydrogen-bonded networks. Recently, we have invesitgated multiple-proton/hydrogen transfer reaction in the 7-azaindole(methanol)n clusters in the gas phase. We have derived new characteristic features of the dynamics: (i) The reaction is cluster-size selective (Excited-state triple-proton/hydrogen transfer reacion preferentialy occurs in the 1:2 cluster), (ii) The reaction is vibrational-mode selective in the lower internal energy region (<600 cm-1) in the S1 state, but it occurs statistically in the higer energy region (>800 cm-1), (ii) The reaction depends on the natue of the excited electronic state, 1La or 1Lb. Qunatum chemistry calculations suggest that the concerted proton transfer is the major reaction channel, while the hydrogen transfer is a minor one. We also investigated cooperative nature of hydrogen-bonded networks, which strenghtens the intermolecular hydrogen bonds, by combining IR spectroscopy with natural bond orbital (NBO) analysis.