Two-step mechanoresponsive luminescence and mechanical stimuli-induced release of small molecules exhibited by a luminescent cyclophane

Achieving multiple mechanoresponsive luminescence-related functions from a single molecule remains challenging. Here, we demonstrate that both two-step mechanoresponsive luminescence and the release of small guest molecules are achieved by a 9,10-bis(phenylethynyl)anthracene-based cyclophane. When gently crushed, the yellow-emissive crystal of the cyclophane exhibits a hypsochromic shift of the emission band, because of alterations in molecular packing at the surface. Subsequent grinding results in a bathochromic shift of the emission band due to excimer formation accompanying the transition from the crystalline state to an amorphous state. Another pseudopolymorph of the cyclophane exhibits the release of chloroform from its crystal structure in response to mechanical stimuli, accompanied by a photoluminescent color change from yellow-green to yellow. These results reveal that luminescent cyclophanes are promising candidates for creating sophisticated mechanoresponsive luminescent materials.

Automated summary

This study demonstrates that a cyclophane based on 9,10-bis(phenylethynyl)anthracene can achieve both two-step mechanoresponsive luminescence and the release of small guest molecules. The manipulation of the emission band by gentle crushing and subsequent grinding, as well as the release of chloroform accompanied by a color change in another polymorph, highlight the potential of luminescent cyclophanes for creating sophisticated mechanoresponsive luminescent materials.