Through-Space Conjugated Supramolecular Polymer Radicals from Spatial Organization of Cucurbit[8]uril: An Efficient Approach for Electron Transfer and Smart Photochromism Materials

Electron transfer-based long-lived radicals are highly challenging because of the limited control over relative orientation, distance, electronic coupling, and nonradiative recombination channels of the donor and acceptor on a molecular level. Herein, the cavity of macrocyclic cucurbit[8]uril (Q[8]) was found to exhibit excellent advantages in controlling the relative orientation and distance of the donor and acceptor moieties via the spatial organization, i.e., the 4-carboxylphenyl appended viologen-derived guest (BcpV2+) was elegantly rearranged as a rigid linear J-type supramolecular polymer by the Q[8] host via noncovalent interactions. Thus, an unprecedented photoinduced electron transfer (PET) triggered through-space conjugated organic radical with distinct photochromism and a NIR-II photothermal effect was observed. Further studies have indicated that the Q[8] encapsulation-triggered PET cycle exhibited good repeatability without significant loss of its efficiency and had potential application in the fabrication of smart windows and erasable printing under photoirradiation or sunlight. These results suggest that the Q[8] host can be used as a new tool in light-energy conversion and photochromism materials science.