Excited‐State Intramolecular Proton Transfer Parent Core Engineering for Six‐Level System Lasing Toward 900 nm

• Published in: Angewandte Chemie 2022-11, Vol.134 (48), p.n/a
• Main Authors: Yan, Chang‐Cun, Liu, Yan‐Ping, Yang, Wan‐Ying, Wu, Jun‐Jie, Wang, Xue‐Dong, Liao, Liang‐Sheng
• Format: Article
• Language: English
• Subjects: Chemistry; Excited-State Intramolecular Proton Transfer; Infrared lasers; Lasers; Lasing; Molecular Design; Near-Infrared Emission; Organic chemistry; Organic lasers; Organic Solid-State Laser; Protons; Six-Level System; System effectiveness
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202210422

Organic molecules which can undergo excited‐state intramolecular proton transfer (ESIPT) process have been considered as ideal gain materials for near‐infrared 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−2. A six‐level system lasing toward 900 nm was achieved with a low lasing threshold of 27.4 μJ cm−2 through engineering of the excited‐state intramolecular proton transfer (ESIPT) of the parent core. This work demonstrates that extending the π‐conjugated system of the ESIPT parent core can effectively enhance the second proton transfer process in a cascaded double ESIPT system.