Multistimuli‐Responsive Luminescence of o‐Carborane Dyads via Restriction of Electron Transfer and Molecular Motion.

The striking change in the emission color/intensity of piezochromic luminescent materials in response to external mechanical stimuli (e.g., pressure, grinding, and stretching) has attracted attention due to potential applications in optical data storage devices, pressure sensors, and optoelectronic devices. The majority of organic materials show redshifted and quenched emission with increasing pressure. Herein, covalently linked donor/acceptor (D/A) o‐carborane dyads that exhibit dual luminescence peaks due to the occurrence of photoinduced electron transfer (PET) are reported. Interestingly, an anomalous phenomenon of pressure‐induced blueshifted and enhanced luminescence is clearly observed. From 1 atm to 1.09 GPa, the restriction of intramolecular motion increases the luminescence of o‐carborane dyads. At high pressures, the compressed o‐carborane unit suppresses PET and decreases the energy gap between the upper excited states. Since the rate of the internal conversion (IC) process is higher than that of PET, the charge transfer (CT) emission gradually disappears, causing the o‐carborane dyads to exhibit blueshifted luminescence. Therefore, a novel strategy for achieving the pressure‐induced enhanced and blueshifted luminescence characteristics of organic materials is reported in this work. [ABSTRACT FROM AUTHOR]