Self-Assembled Polyhedral Oligosilsesquioxane Dendrimers for Circularly Polarized Luminescence Energy Transfer

Polyhedral oligosilsesquioxanes (POSSs), as the smallest possible particle of silica, have rarely been incorporated into chiral nanostructures due to their shape-persistent structure and nanoscale size. In this work, we show the construction of two chiral organic building units containing POSS segments and the fabrication of chiral coassemblies as a matrix for circularly polarized luminescence (CPL) harvesting and color conversion. POSSs were separately conjugated to N-terminal aromatic glutamic dendrons appended with pyrene and naphthalimide luminophores, respectively, through an alkyl spacer (PGP and NGP). The structural similarity allows for the molecular intercalation between the species to afford chiral coassembled arrays, where energy transfer occurred due to the spectra overlap between the appended chromophores. Although PGP and NGP feature left- and right-CPL, their coassembly exhibited exclusive left-CPL identical to that of the energy transfer donor PGP. The energy transfer underwent a CPL light-harvesting modality to achieve specific chiroptical responses. This work illustrates an application of POSS moieties in controlling supramolecular chirality and CPL in functional nanoassemblies.