Search

The synthesis of 1,3,6,8-tetraaryl substituted pyrenes is described. The substituents on the aryl groups influence the optoelectronic properties of the pyrene core indicating a strong coupling between the aryl groups and the pyrene core. Electronic absroption spectra of the cation radicals generated in solution by the single electron oxidation of pyrenes reaffirmed the coupling of the aryl rings with the pyrene. The aryl groups at 1,3,6,8-positions completely inhibit the π-stacking of pyrene core in solution. Crystal structure of the cation radical salt of tetraphenyl shows charge delocalization between neutral pyrene unit and two cationic pyrene cores. Complete inhibition of the pyrene core stacking is observed in the solid state of cation radical when the dendritic pentaphenyl groups surround the pyrene core.

A simple synthesis of soluble tetrakis (poly -p- phenylene ) ethylenes (TPEs), where poly- p -phenylene units contain up to 4 phenylene moieties, is accomplished using an easily available tetrakis (4-bromophenyl)ethylene and phenyl, biphenyl, and p- terphenylboronic acids, containing solubilizing iso -alkyl groups as the end-capping substituents. Electrochemical oxidation of TPEs (i.e., T1–T4 ) showed that they undergo reversible electrochemical oxidations and form stable cation-radical salts in solution. The evaluation of absorption and emissions characteristics of T1 – T4 in solution indicated that unlike parent tetratolylethylene ( T1 ), the higher homologues (i.e., T2 – T4 ) show emission centered at 520 nm and the quantum efficiency of emission increases with the increasing number of phenylene moieties in poly- p -phenylene units in various TPEs.