Abstract: We investigated the competition mechanism of intramolecular and intermolecular proton transfer of 2-amino-3-(2′-benzoxazolyl)quinolineH₂O (ABO-H₂O) water complex in the excited states by means of the density functional theory and timedependent density functional theory. The results show that there is an intramolecular hydrogen bond and two intermolecular hydrogen bonds in the ABO-H₂O complex. When the complex in the ground state is excited to the first electron excited state, only a 34157 kJ/mol energy barrier is needed for the ABOH2O complex to occur intramolecular proton transfer reaction. There is a 63585 kJ/mol energy barrier in the intermolecular double proton transfer process of the ABO-H₂O complex in the excited state. There is a competitive mechanism for intramolecular and intermolecular proton transfer processesof the ABO-H₂O complex in the first electron excited state. The excited state intramolecular proton transfer process is more likely to take place for the ABO-H₂O complex.

Key words: hydrogen bond, excited state, intramolecular proton transfer, intermolecular proton transfer