Molecular conformation and cyano regio-isomerization effects to the piezochromic properties of cyanostilbene-bridged donor-acceptor-donor structured organic luminogens

•A series of cyanostilbene-bridged donor-acceptor-donor structured dual-state emissive organic luminogens (OLs) are designed and synthesized.•Molecular conformation and cyano regio-isomerization of the OLs are selectively controlled.•Piezochromic properties of the OLs are systematically studied both upon mechanical grinding and under hydrostatic pressures.•Molecular conformation and cyano regio-isomerization effects to the piezochromic properties of the OLs are illustrated. Organic luminogens (OLs) with piezochromic (PC) properties have attracted much attention due to their great application potentials. In this work, we report the synthesis and PC properties of a series of cyanostilbene (CS)-bridged donor-acceptor-donor (D-A-D) structured dual-state emission OLs. Their molecular conformations are controlled into linear-shaped or curved-shaped, by adjusting the connecting positions of the phenyl rings (para or meta) of the CS moiety with the donor units. Moreover, the cyano groups within the CS moieties are regio-selectively altered. On these basis, the PC properties of the OLs are systematically studied upon mechanical grinding (MG) and under hydrostatic pressure (HP). Upon MG, only the linear-shaped compound shows obvious PC behavior, similar with its reported analogue. However, the curved-shaped compounds are almost unchangeable. Under HP, all these OLs exhibit typical PC responses, and the pressure coefficients of emission wavelengths and reversibility after HP releasing can be correlated with the differences in their molecular structures. This work well illustrates the significant impacts of molecular conformation and regio-position of cyano group in the PC properties of large D-A-D structured CS derivatives, providing valuable guidance for design of future PC OLs.