Femtosecond dynamics of excited-state intramolecular proton transfer in o-tosylaminobenzoic and o-acetylaminobenzoic acids

The dynamics of excited-state intramolecular proton transfer (ESIPT) and of relaxation processes in o-tosylaminobenzoic acid (TAC) and o-acetylaminobenzoic acid (AAC) have been studied by femtosecond absorption spectroscopy with a time resolution of 30 fs. The ESIPT characteristic time in the TAC dimer and monomer and in AAC monomer is 50 fs. The excited product of photoinduced proton transfer in the monomer undergoes effective radiationless deactivation with a characteristic time of 30 ps, one of the channels of which is internal rotation followed by intersystem crossing and internal conversion. The product of ESIPT in the TAC dimer deactivates preferentially into the ground state via radiative transition with a time of 291 ps. ESIPT in the AAC dimer is thermodynamically unfavorable and occurs with a low yield.