Excited‐state intramolecular proton transfer (ESIPT)‐active organic semiconductor materials, characterized by a or several resonance‐assisted hydrogen bonds (RAHBs), are supposed to be ideal candidates for achieving high‐performance near‐infrared (NIR) lasers. However, according to the energy gap law, the development of ESIPT‐active gain materials is still limited by the serious nonradiative decays. Herein, it is demonstrated that RAHBs can activate ESIPT lasing by inhibiting nonradiative decays. A new ESIPT‐active material 1,5‐dihydroxy‐2,6‐diphenylanthraquinone (DP‐DHAQ) containing two centrosymmetric RAHBs is developed, which exhibits a ≈100‐fold higher radiative decay rate (kr = 1.1 × 1010 s–1) in doped polystyrene (PS) film than that of 1‐hydroxy‐5‐methoxy‐2,6‐diphenylanthraquinone (DP‐HMAQ) and 1,5‐dimethoxy‐2,6‐diphenylanthraquinone (DP‐DMAQ), in which one and two RAHBs are broken, respectively, by introducing methyl groups. Both DP‐DHAQ and DP‐HMAQ can form four‐level systems based on the ESIPT processes, but only DP‐DHAQ doped PS microspheres exhibit laser emission at 710 nm under the test conditions. It is worth mentioning that single‐crystal microplates of DP‐DHAQ can realize NIR laser emission at 725 nm. The results suggest that RAHBs can effectively activate the gain property of ESIPT‐active materials, which deepens insights into NIR ESIPT lasing and provides a new proposal for the design of organic laser‐active molecules.

In contrast to the widely reported excited-state single proton-transfer, excited-state multiple proton transfer (ESMPT) containing two or more intra-or inter-molecular proton transfers has greatly expanded the research scope of the excited-state proton transfers. In recent decades, ESMPT-active organic molecules have attracted much attention owing to their unique photophysical properties, such as large magnitude Stokes shifts and dual emission. These photophysical properties facilitate the application of the organic molecules in organic solid-state lasers, fluorescent probes and sensors, and molecular switches. Herein, we introduce the fundamentals of the ESMPT and review the recent advances in different types of ESMPTs in organic molecules. Finally, we present our conclusions and the future development prospects of the ESMPT in organic molecules. excited-state multiple proton transfer, hydrogen bond, photoisomerization, organic molecules, photophysical properties

Triplet excitons can be utilized upon introduction of phosphors into exciplexes, and such a scenario has been studied in the development of high-performance near-infrared (NIR) organic light-emitting diodes (OLEDs). To generate exciplexes in an emitting layer (EML) in the device, commercially available phosphors bis­(2-phenylpyridinato-N,C2′)­iridium­(acetylacetonate) [Ir­(ppy)2acac] and iridium­(III) bis­(4-phenylthieno­[3,2-c]­pyridinato-N,C2′)­acetylacetonate (PO-01) were selected as donor components; in addition, a new designed fluorescent molecule, 3-([1,1′:3′,1″-terphenyl]-5′-yl)­acenaphtho­[1,2-b]­quinoxaline-9,10-dicarbonitrile (AQDC-tPh), and recently reported 3-([1,1′:3′,1″-terphenyl]-5′-yl)­acenaphtho­[1,2-b]­pyrazine-8,9-dicarbonitrile (APDC-tPh) were selected as acceptor components. An OLED with PO-01:AQDC-tPh blends as the EML has realized NIR emission at 750 nm and a maximum external quantum efficiency (EQE) of >0.23%. Furthermore, an OLED containing a PO-01:APDC-tPh blend realizes a maximum EQE of 0.16% at 824 nm. The high performance of these devices underlying phosphor-based exciplexes proves the potential and feasibility of our strategy for the construction of efficient NIR OLEDs.

Organic molecules which can undergo excitedstate intramolecular proton transfer (ESIPT) process have been considered as ideal gain materials for nearinfrared organic lasers owing to their effective four-level systems. However, extending lasing wavelength beyond 800 nm with present ESIPT-active gain materials is still in challenge. Herein, we established a molecular design strategy that operates via extending the π-conjugated system of the ESIPT parent core to enhance the cascaded double ESIPT process and thus to achieve the red-shifted six-level system lasing. Concretely, a model molecule with 1,9-dihydroxyanthracene as the ESIPT parent core was designed and synthesized, which was proved to undergo twice cascaded ESIPT processes while the 1,8-dihydroxynaphthalene-based analogue can only undergo once ESIPT process based on DFT calculations and ultrafast dynamics analyses. Finally, a six-level system lasing toward 900 nm was achieved with a low threshold of 27.4 μJ cm À 2 .

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