Nanosized polyphenylene dendrimers based upon pentaphenylbenzene units

Abstract

A facile divergent synthesis of monodisperse polyphenylene dendrimers having diameters of 21–55 Å is presented. These nanoparticles have been preparedvia a [2+4]cycloaddition–deprotection sequence using an excess of tetraphenylcyclopentadienone 1a as monomer and the tetraethynylbiphenyl 2 as core. Due to the dense packing of 22, 62 or 142 benzene rings in generations G ₁ , G ₂ and G ₃ , respectively, the conformational freedom of the higher generations G ₂ and G ₃ is limited. Molecular mechanics calculations as well as molecular dynamics simulations are included in a discussion of the structure and the shape-persistence of G ₂ . The calculations revealed that selected inner distances of the molecule varied only 5–10% during the molecular dynamics simulations, thus indicating that the overall shape of the molecule essentially did not change throughout the simulation time.