Switching excitons between the emissive and photochromic pathways in the triphenylethylene system

Abstract

Photoluminescence and photochromic pathways are competitive during the exciton-decay processes. To rationally control molecular photoluminescence and photochromic properties, triarylethylene derivatives combining ethynyl and ethynyltrimethylsilane groups, namely TrPEF₂H and TrPEF₂TMS, were designed and synthesized in this work. By simply attaching and removing the TMS protecting group, these two molecules can be mutually converted. Detailed photophysical and photochromic investigations revealed that molecules TrPEF₂H and TrPEF₂TMS exhibit distinct emissive and photochromic behaviors in the crystalline state: TrPEF₂H features a pronounced photochromic property and a low photoluminescence quantum yield (PLQY) of 1.5%, whereas a weak photochromic response and a high PLQY of 14.2% were obtained in crystalline TrPEF₂TMS. The distinguished difference is proposed as due to the introduction of the bulky trimethylsilane moiety in TrPEF₂TMS, which effectively suppressed the molecular vibrations and photocyclization reactions. Single crystal analyses and theoretical calculations were further carried out to interpret the distinction of the photophysical and photochromic properties in molecules TrPEF₂H and TrPEF₂TMS. Furthermore, TrPEF₂H and TrPEF₂TMS were applied in a photo-controlled pattern showing reversible on–off switching emission. This design strategy gives the two molecules incomparable advantages in dual-mode signal and surface-involved photoresponsive applications, such as data encryption and information storage.