ProBox: A Rigid yet Dynamic Cyclophane Capable of Adaptive and Redox-Switchable Host-Guest Binding.

A pyrrolodithiin-derived box-like cyclophane (ProBox), featuring an adaptive geometry with stimuli-responsiveness, was designed and successfully constructed. The dynamic and foldable dithiin subunit endowed the cyclophane with a compressible cavity which can transform from a hex-nut geometry to a nearly rectangular box upon complexing guests with various sizes and shapes. The resulting pseudorotaxane complexes could be dethreaded via electrochemical oxidation. Such an adaptive cavity along with redox-switchable host-guest binding of ProBox could enable further applications in complex molecular switches and machines.