Distinct Piezochromic Properties of Cyanostilbene- and Cyanostyrene-Based Donor–Acceptor–Donor- and Donor–Acceptor-Structured Organic Luminogens

Organic luminogens (OLs) with piezochromic (PC) properties have attracted significant attention for their varied applications in chemical sensors, organic optoelectronic devices, biological imaging, etc. In this work, we designed and synthesized three donor–acceptor–donor- or donor–acceptor-structured OLs with different donor or acceptor moieties. Their photophysical properties in both dilute solution and aggregated states were studied through various spectroscopic analytical methods, and their PC properties were investigated under mechanical grinding (MG) conditions. The OLs containing cyanostilbene moiety exhibited a photoemission shift up to ~45 nm after simple grinding, while that was only ~10 nm for cyanostyrene-containing OL. Combined with the powder X-ray diffraction analysis, the incorporation of the cyanostilbene moiety is inferred to play an important role in inducing the apparent PC properties. Our study not only reports novel OLs with good PC properties, but also discusses the structure–property relationships in order to provide guidance for future rational design and the development of novel PC materials.