Dynamics simulations of excited-state triple proton transfer in 7-azaindole complexes with water, water–methanol and methanol

• We model excited-state triple proton transfer (ESTPT) of 7-azaindole with solvents.
• The PT from pyrrole to the solvent is the rate determining step of the ESTPT.
• The pathway is most likely a PT with no crossing between ππ* and πσ* states.
• The ESTPT is ultrafast within 85 fs.

Excited-state triple proton transfer (ESTPT) reactions in 7-azaindole (7AI) complexed with two water, with one water and one methanol, and with two methanol molecules were investigated by dynamics simulations in the first excited state computed with the second order algebraic-diagrammatic construction (ADC (2)) method. The results show that photoexcitation may trigger ultrafast an asynchronous concerted proton transfer via two solvent molecules along an intermolecular hydrogen-bonded network. The probability of occurrence of ESTPT ranges from 32% for 7AI(H2O–MeOH) to 64% for 7AI(MeOH)2. The average time for completing the ESTPT varies between 58 and 85 fs depending on the complex. The proton transfer (rather than hydrogen transfer) nature of the reaction was suggested by the nonexistence of crossings between the ππ* and πσ* states.

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