A New Series of D 1 -A-D 2 -type ESIPT-TICT-AIE Active Orange-to-red Emissive Unsymmetrical Azines: Their All-throughout Mechanochemical Synthesis and Exploration of Photophysical Properties

• Published in: Chemistry, an Asian journal Vol. 18; no. 10; p. e202300048
• Main Authors: Bhosle, Akhil A, Banerjee, Mainak, Hiremath, Sharanabasava D, Bhasikuttan, Achikanath C, Chatterjee, Amrita
• Format: Journal Article
• Language: English
• Published: Germany 16.05.2023
• Subjects: Twisted intramolecular charge transfer (TICT); Aggregation-induced emission (AIE); Mechanochemical synthesis; Excited-state intramolecular proton transfer (ESIPT); Fluorescence; Donor-acceptor systems; Unsymmetrical azines
• ISSN: 1861-4728; 1861-471X
• DOI: 10.1002/asia.202300048

Azines are interesting compounds exhibiting aggregation-induced-emission (AIE) and twisted-intramolecular-charge-transfer (TICT) properties that have exciting prospects in chemosensing and bioimaging applications. They commonly have symmetrical structures and there is no report on red-emissive unsymmetrical azines. Herein, we report a novel class of orange-to-red emissive hydroxybenzothiazole(HBT)-based unsymmetrical azines (BTDPA) with triple photophysical characteristics of ESIPT-TICT-AIE. The dyes were synthesized by an all-throughout mechanochemical route in a sustainable way. They displayed D -A-D character and fluoresce strongly both in organic solvents due to ESIPT and in the solid state by AIE via TICT. The incorporation of different electron-withdrawing groups (EWGs) and electron-donating groups (EDGs) at either HBT or diphenyl-methylene moiety resulted in tunable fluorescence properties. The red-emissive character was achieved by keeping EDG both at HBT (-OMe) and the diphenyl-methylene moiety (-NMe ) (λ 680 nm). The dyes exhibited good quantum yields, large Stoke shifts (upto 293 nm) and were utilized in nitroaromatics and Cu sensing.