Water-Soluble Redox-Active Cage Hosting Polyoxometalates for Selective Desulfurization Catalysis.

Transformations within container-molecules provide a good alternative between traditional homogeneous and heterogeneous catalysis, as the containers themselves can be regarded as single molecular nanomicelles. We report here the designed-synthesis of a water-soluble redox-active supramolecular PdL cage and its application in the encapsulation of aromatic molecules and polyoxometalates (POMs) catalysts. Compared to the previous known PdL cage, our results show that replacement of two cis-blocked palladium corners with p-xylene bridges through pyridinium bonds formation between the 2,4,6-tri-4-pyridyl-1,3,5-triazine (TPT) ligands not only provides reversible redox-activities for the new PdL cage, but also realizes the expansion and subdivision of its internal cavity. An increased number of guests, including polyaromatics and POMs, can be accommodated inside the PdL cage. Moreover, both conversion and product selectivity (sulfoxide over sulfone) have also been much enhanced in the desulfurization reactions catalyzed by the POMs@PdL host-guest complexes. We expect that further photochromic or photoredox functions are possible taking advantage of this new generation of organo-palladium cage.