Molecular Transmission: Visible and Rate-Controllable Photoreactivity and Synergy of Aggregation-Induced Emission and Host-Guest Assembly

The ability to modulate reaction rates like controlling speeds by the transmission of vehicles is highly desirable and challenging. Herein, a regio- and stereoselective photodimerization with four tunable and visible rates were realized at the molecular level via the synergy of host-guest chemistry and AIE technology: (i) normal rate without adding macrocycles (nu(1)), (ii) greatly accelerated rate by the formation of 2:2 complex between gamma-cyclodextrin (gamma-CD) and an AIE luminogen (AlEgen) (nu(2)), (iii) deactivated reaction by 1:1 binding of beta-cyclodextrin (beta-CD) with the AlEgen (nu(3)), and (iv) completely inhibited photoreaction in the beta-CD-based hydrogel (nu(4)). The restriction of intramolecular motions of AlEgen activates the fluorescence of the transmission with the rate of nu(2) > nu(1) > nu(3) > nu(4) approximate to 0 and enhances the fluorescent contrast before and after photoirradiation, which not only provides in situ trackability to the microscopic process, but also endows intuitive mechanistic insights. The synergy of AIE and host-guest chemistry can also amplify the signal of the reversible reaction and visualize tiny ring-opening product. Microscopic mechanism was further applied to the construction of a porous hydrogel-based microreactor which exhibited enhanced microscopic visualization and excellent recyclability. The present approach demonstrated a powerful platform for the understanding, monitoring and controlling reaction kinetics. Meanwhile, the porous hydrogel reactor based on precise molecular design serves as a new inspiration for heterogeneous catalysis.