D-A-D' type phenothiazine modified bisarylic methanone derivatives exhibiting fluorescent response to mechanical force and reversible tricolor switching

Two D-A-D ' type bisarylic methanone derivatives PTZ-BZ-Cz and PTZ-BZ-TPA, which consisted of two different electron donors and the same electron acceptor were designed and synthesized. Theoretical calculations revealed that both possessed asymmetric donor-acceptor structures and highly distorted spatial conformations. Optical researches illustrated that both exhibited an evident intramolecular charge transfer (ICT) characteristics and effective emission in the solid state. Interestingly, the mechanochromic behaviors were found. The XRD indicated that the reason for the mechanochromic phenomenon was crystalline-to-amorphous transition. It should be noted that PTZ-BZ-Cz exhibited high contrast and tricolor switching mechanochromic properties under external force stimuli. This novel phenomenon is very interesting for the development of mechanochromic materials that can simultaneously achieve high-contrast and multicolor switching. The current work provided a basis for the design of organic molecules featuring both high contrast and multicolor switching.