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 (ν1), (ii) greatly accelerated
rate by the formation of 2:2 complex between γ-cyclodextrin
(γ-CD) and an AIE luminogen (AIEgen) (ν2),
(iii) deactivated reaction by 1:1 binding of β-cyclodextrin
(β-CD) with the AIEgen (ν3), and (iv) completely
inhibited photoreaction in the β-CD-based hydrogel (ν4). The restriction of intramolecular motions of AIEgen activates
the fluorescence of the transmission with the rate of ν2 > ν1 > ν3  >
ν4 ≈ 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.