The same molecule but different molecular conformation making the different room temperature phosphorescence in phenothiazine derivatives

Room temperature phosphorescence (RTP) luminogens have attracted much attention because of their wide range of applications in chemical sensors, bio-imaging, anti-counterfeiting technology, etc. However, these luminogens are still very scarce, especially those with a stimulus response effect, partly due to the unclear mechanism and the lack of design guidance. Here, in phenothiazine (PTZ) derivatives with different numbers of chlorine atoms, exciting conformation-dependent RTP emission was observed, that is, the luminogens with quasi-axial (ax) conformation showed an obvious RTP effect, while the quasi-equatorial (eq) ones did not. In particular, both conformers (ax and eq) were obtained for PTZ-3Cl in polymorphisms, demonstrating their mutual transformation under external stimulus with a unique stimulus-responsive RTP effect.