Ladder oligo(p-phenylenevinylene)s with silicon and carbon bridges.

A general and versatile synthetic method for ladder oligo(p-phenylenevinylene)s (LOPVs) and related pi-electron systems, having annelated pi-conjugated structures with silicon and carbon bridges, has been developed on the basis of the combination of two cyclization reactions, i.e. the intramolecular reductive cyclization of (o-silylphenyl)acetylene derivatives and the Friedel-Crafts-type cyclization. This methodology allows us to synthesize a homologous series of the ladder molecules up to a 13-ring-fused system. The crystal structural analysis of the longest 13-ring-fused LOPV proves its nearly flat pi-conjugated framework with a length of ca. 2.9 nm. All the produced ladder pi-electron systems show intense fluorescence in the visible region with high quantum yields as well as relatively small Stokes shifts.