Unusual aggregation of nanosized six-arm star oligofluorenes

A series of monodisperse six-arm benzene-cored star oligofluorenes are prepared by a divergent/convergent strategy, starting from the repetitive divergent synthesis of symmetrical ethynyl-bridged oligofluorenes to the convergent Co-catalyzed alkyne cyclotrimerization. The structures of these six-arm molecules are fully characterized. The diameter of the largest molecule SF3 reaches ca. 3 nm. These highly substituted star-shaped oligomers exhibit extremely high fluorescent quantum yields in solution and unexpected red-shifted and broadened emission with fine structure in the film as a result of the formation of stable aggregates.