Synthesis of star-shaped monodisperse oligo(9,9-di-n-octylfluorene-2,7-vinylene)s functionalized truxenes with two-photon absorption properties.

A series of new star-shaped monodisperse conjugated truxene derivatives bearing oligo(fluorene-vinylene) arms (Tr-OFVn, n = 1, 2, 3, 4) have been synthesized. It is found that the conjugation of the oligomers can be extended with prolonging the arms. Notably, the branched oligomers Tr-OFVn without strong donor and acceptor units exhibit two-photon absorption properties, and the two-photon absorption cross sections (δ(max)) increase with increasing the number of fluorene-vinylene units in the arms. The maximum value of δ(max) reaches 8073 GM for compound Tr-OFV4, which made it one of the most competitive compounds with enhanced TPA cross section. It provides a new platform for exploiting strong TPA compounds, in which the extended π-conjugated systems are involved in the absence of strong donor and acceptor units.