Rational design of reversibly photochromic molecules with aggregation-induced emission by introducing photoactive thienyl and benzothienyl groups

Reversible photochromic molecules with solid-state fluorescence are of great value and perspective in various surface-involved practical applications. Herein, we propose a general strategy to design reversible photochromic molecules with solid-state fluorescence by introducing photoactive thienyl and benzothienyl groups into an AIE-active molecular skeleton. The combination of a thienyl or benzothienyl group and a triphenylethene in the right manner enables the molecules to possess unique aggregation-induced emission properties and reversible photo-controlled changes in color and fluorescence in solid state. Theoretical analysis reveals that photo-triggered cyclization and cycloreversion reactions are responsible for the reversible photochromism and photoinduced fluorescence switching, and the enlargement of the conjugation of the introduced photoactive units can significantly promote the cyclization reactions and the photochromic processes. The excellent performance of these photochromic molecules with aggregation-induced emission activity in a photoswitchable patterning paper and multiple encryption of anti-counterfeiting of a banknote demonstrates that they are perfectly suited for surface-involved photo-controlled applications such as information storage and data encryption.