Novel supramolecular artificial light-harvesting systems based on AIE-active macrocycles for efficient white-light photocatalysis in water

Abstract

Constructing supramolecular artificial light-harvesting systems (ALHSs) based on the Förster resonance energy transfer (FRET) mechanism provides an optimal platform for understanding natural photosynthesis and simulating natural light-harvesting systems. In the present work, rigid macrocycle K-1 with a nonplanar conformation and aggregation-induced emission (AIE) properties was selected as an energy donor in ALHSs, while the non-cyclic AIEgen K-2 was used for a comparative study. In aqueous solution, an efficient one-step energy-transfer process was established between blue-emitting K-1 and an acceptor (namely PBTB) with orange fluorescence to afford a high energy-transfer efficiency (Φ_ET) of up to 82.6%. Notably, bright white light emission can be readily realized. Moreover, the triad FRET system was fabricated through energy transfer from the AIEgens to PBTB, then further transferring the captured energy to the final red-emitting acceptor (namely as Z1), achieving an efficient two-step sequential energy transfer. When the ratio of K-1/PBTB/Z1 assemblies reached 1000 : 40 : 14, the optimal Φ_ET was 66.4%. More importantly, it was found that the ALHS based on macrocycle K-1 showed much higher photocatalytic activity for the cross-dehydrogenative coupling (CDC) reaction. Therefore, the flexibility of this novel supramolecular strategy renders the macrocyclic AIEgen a promising candidate to construct efficient ALHSs for photocatalysis.