Heavy mass effect on excited-state double-proton transfer in the 7-azaindole dimer by Cl substitution

The measurement of the electronic spectra of jet-cooled 4-chloro-7-azaindole dimer (4CAI2) revealed that the Cl substitution substantially suppresses the excited-state double-proton transfer (ESDPT). Quantum chemistry calculation at the CIS level suggested that the change in the intermolecular stretching mode, which promotes ESDPT, is important for the suppression of ESDPT.

The Cl substitution substantially suppresses the excited-state double-proton transfer in the 7-azaindole dimer. The heavy atom substitution significantly changes the displacements of the intermolecular stretching mode.