Organic near-infrared (NIR) luminescent materials have captured intense research interest owing to their potential applications in optical communication, data storage, bioimaging, sensing and night vision. Excited state intramolecular proton transfer (ESIPT) process with absorption in normal form while emission in tautomer form can lead to a distinct redshift emission, based on which, a lot of organic NIR luminescent materials were designed. Because of attractive features such as ultrahigh sensitivity to the surroundings, large Stokes shift, and inherent four level system, ESIPT based NIR luminescent materials are supposed to be ideal fluorescent probes and gain materials. In this review, first, organic near-infrared luminescent materials based on ESIPT process are summarized according to the core structures. Second, recent advances of ESIPT-based organic near-infrared fluorescent probes and organic NIR lasers are reviewed. Finally, the current challenges and prospects of ESIPT-based organic NIR luminescent materials are introduced.

Organic lasers that emit light in the deep-red and near-infrared (NIR) region are of essential importance in laser communication, night vision, bioimaging, and information-secured displays but are still challenging because of the lack of proper gain materials. Herein, a new molecular design strategy that operates by merging two excited-state intramolecular proton transfer-active molecules into one excited-state double proton transfer (ESDPT)-active molecule was demonstrated. Based on this new strategy, three new materials were designed and synthesized with two groups of intramolecular resonance-assisted hydrogen bonds, in which the ESDPT process was proven to proceed smoothly based on theoretical calculations and experimental results of steady-state and transient spectra. Benefiting from the effective six-level system constructed by the ESDPT process, all newly designed materials showed low threshold laser emissions at approximately 720 nm when doped in PS microspheres, which in turn proved the existence of the second proton transfer process. More importantly, our well-developed NIR organic lasers showed high laser stability, which can maintain high laser intensity after 12000 pulse lasing, which is essential in practical applications. This work provides a simple and effective method for the development of NIR organic gain materials and demonstrates the ESDPT mechanism for NIR lasing.