Dimesitylboryl-functionalised cyanostilbene derivatives of phenothiazine: distinctive polymorphism-dependent emission and mechanofluorochromism

Organic -conjugated compounds showing polymorphic and mechanofluorochromic (MFC) behaviors are promising candidates for many potential applications in materials chemistry. Herein, we report two distinct molecular designs based on phenothiazine as a donor and triarylborane and cyanostilbene as acceptors, for example, an acceptor-donor-acceptor system (A-D-A; compound 3) and donor-acceptor (D-A; compound 4) moieties, in which 3 exhibits polymorphism with two distinct emissions (yellow and red). The single crystal X-ray diffraction analyses of 3 clearly show two conformational isomers. The color of the emission can be altered by a grinding or fuming process.