Simple Substituents Make Big Differences in Photophysical Performances of 2,1,3-Benzothiadizole-conjugated Spiropyrans

Developing multifunctional spiropyran dyes is of particular importance in diverse applications. In the present study, we synthesized two 2,1,3-benzothiadiazole-conjugated spiropyrans (BT-SP-NO 2 and BTSP-NMe 2 ) with distinct substituents. These donor-acceptor-structured spiropyrans exhibited typical twisted intramolecular charge transfer features and strong emissions in low-polarity solvents with fluorescence quantum yields (QYs) of up to 90.7%. Like traditional spiropyrans, the electron-acceptorsubstituted BT-SP-NO 2 exhibited excellent photochromic behavior under multiple alternating UV-Vis irradiation, while the electron-donor-substituted BT-SP-NMe 2 was an acidochromic dye. In addition, the substituent groups distinctly affected the packing modes of these spiropyrans in the solid state. BTSP-NMe 2 showed a much stronger solid-state emission (QY of 59.0%) than BT-SP-NO 2 . Moreover, these two dyes were utilized as biocompatible probes for the speci fic light-up imaging of lipid droplets. (c) 2024 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.