Development of a new type of multi-functional mechanochromic luminescence material by infusing a phenyl rotator into the structure of 3,4-diphenylmaleic anhydride

Abstract

Mechanochromic luminescence (MCL) materials have attracted increasing attention due to their versatile functions in many fields. In this study, based on the structure of 3,4-diphenylmaleic anhydride (BPMA), we designed and synthesized a new class of fluorophore (compounds W1–W7) with red emission by integrating a new substituted phenyl group and a donor–acceptor unit into the structure of BPMA. The introduction of 2-morpholine, 4-(N,N-diphenylamino) and 2-piperidin-1-yl groups into the new phenyl group resulted in W1, W4 and W6, respectively. Among the compounds synthesized, W1, W4 and W6 exhibited prominent AIE phenomenon, which was elucidated by analyzing their crystal data. Interestingly, compound W6 exhibited polymorphic property; two crystals named W6R (red color, λ_em = 610 nm) and W6Y (yellow color, λ_em = 562 nm) were simultaneously obtained in acetone. Their single crystal X-ray data clearly explained their different emission behaviors. In addition, W1, W4 and W6 showed reversible mechanochromic luminescent properties under external multiple stimuli. Powder X-ray diffraction and differential scanning calorimetry curves revealed that the initial crystalline states were transformed to amorphous states under various external stimuli. Further investigation revealed that W6 showed acidochromic property. Collectively, this study provides an efficient strategy to design simple MCL materials and expands the potential applications of W4 and W6 in various areas.