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Two Competing Excited-State Intramolecular Proton Transfer Pathways in AHMD.

Jiahui Wu1, Yanling Liu1, Haoran Ma1

  • 1School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.

The Journal of Physical Chemistry. A
|November 18, 2025
PubMed
Summary
This summary is machine-generated.

Excited-state intramolecular proton transfer (ESIPT) in AHMD involves two pathways. A near-barrierless route (ESIPT-2) dominates relaxation, leading to high fluorescence efficiency and guiding the design of stable fluorescent materials.

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Area of Science:

  • Photophysics and Photochemistry
  • Theoretical Chemistry
  • Materials Science

Background:

  • Excited-state intramolecular proton transfer (ESIPT) is crucial for hydrogen-bonded chromophores.
  • Understanding ESIPT mechanisms is key to designing efficient fluorescent dyes.

Purpose of the Study:

  • Investigate two competitive ESIPT mechanisms in 4-amino-7-hydroxy-2-methylisoindoline-1,3-dione (AHMD).
  • Elucidate the coupling between proton transfer and nonradiative decay.
  • Provide insights for designing photostable ESIPT materials.

Main Methods:

  • Multiconfigurational electronic structure calculations (CASSCF/MS-CASPT2).
  • Nonadiabatic surface-hopping dynamics simulations.
  • Atomistic resolution of proton transfer pathways.

Main Results:

  • Identified two ESIPT routes: a higher-barrier ESIPT-1 and a dominant near-barrierless ESIPT-2.
  • ESIPT-2 governs ultrafast excited-state relaxation and nonradiative decay via conical intersection.
  • 33.8% of molecules decay nonradiatively within 779 fs, explaining high fluorescence.

Conclusions:

  • The near-barrierless ESIPT-2 pathway is crucial for AHMD's photophysical properties.
  • Nonradiative decay is strongly coupled to the ESIPT-2 channel.
  • Findings offer principles for designing advanced photostable ESIPT materials.