Abstract: Using AM1 and INDO/CImethods, the potential energy surface and mechanism of double proton transfer of excited state of 7-azaindole dimer have been studied.In ground state, the energy of normal dimer is lower than that of the tautomer, although the stronger intramolec-.ular hydrogen-bonds exist in the tautomer.Under the condition of photo-emission, the normal dimer can be turned into the tautomer through two proton transfer of excited state, which causes the abnormal stokes shift of the fluorescence.

Key words: 7-Azaindole dimer, Excited state proton transfer, AM1 and INDO/CI methods