Piezochromic materials, which exhibit a fluorescence response with large emission spectral shifts and high sensitivity, may be useful in important applications, but there have been few reports of such organic luminophores. Herein, we report a new high-sensitivity piezochromic material based on the incorporation of an o-carborane unit, which exhibits aggregation-induced emission properties. In a high-pressure experiment, compared to carborane-free MTY, which exhibits an emission spectral shift of 75 nm and a sensitivity of 19.1 nm ⋅ GPa-1 , the o-carborane dyad MTCb shows a larger emission wavelength difference of 131 nm and a higher sensitivity of 32.8 nm ⋅ GPa-1 , demonstrating a performance that ranks among the best of organic piezochromic materials reported thus far. MTCb molecules adopt a J-aggregated pattern and have relatively loose molecular packing in the crystalline state. Interestingly, nonconjugated spherical carborane can disrupt the π-π interactions between adjacent molecules during compression, which results in excellent piezochromic performance.
Keywords: hydrostatic pressure; o-carborane; piezochromism; sensitivity.
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