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Updated: Sep 9, 2025

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Switchable NIR emission enabled by phase-driven barrierless ESIPT in 1-NH2
Abstract:
In this Letter, we report phase-dependent excited-state relaxation pathways and fluorescence mechanisms of the 1-NH2 molecule using quantum chemical simulations. In the liquid phase, the synergistic coupling between excited-state intramolecular proton transfer (ESIPT) and twisted intramolecular charge transfer (TICT) facilitates nonradiative decay through a conical intersection (CI) channel, leading to the quenching of Keto* fluorescence. Conversely, in the solid phase, restricted molecular rotation blocks the CI channel and promotes barrierless ESIPT, yielding strong Keto* emission in the near-infrared (NIR) region. Reorganization energy analysis further elucidates the origin of redshifted emission. This work reveals a novel, to the best of our knowledge, phase-dependent fluorescence switching mechanism in 1-NH2, offering valuable theoretical guidance for developing smart luminescent materials.
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