Mechanochromic cyclodextrins

Mechanochromic cyclodextrins (MCDs) that can generate blue radical species, which are exceptionally stable toward atmospheric oxygen and can thus be quantitatively characterized via electron paramagnetic resonance (EPR) spectroscopy, were synthesized. MCDs have a defined structure that consists of a diarylbibenzofuranone skeleton mechanophore sandwiched between two CDs. Grinding tests and EPR measurements of the MCDs revealed their high mechanoresponsiveness, reflecting the inherent rigidity of the CDs and the formation of a supramolecular structure in the bulk.