Dimerization of Tri(4-bromophenyl)benzene by Aryl-Aryl Coupling from Solution on a Gold Surface

摘要

Monolayers of monomer l,3,5-tri(4-bromo-phenyl)benzene (TBPB) and the dimerized product 3,3'",5,5'"-tetra(4-bromophenyl)quaterphenyl (TBPQ) on a gold surface have been studied using ambient scanning tunneling microscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Molecular layers are prepared by allowing sessile drops of solution to dry on a gold substrate. For room-temperature deposition we observe ordered arrays of TBPB in three distinct packing arrangements. Deposition on a heated substrate leads to the formation of the dimerized product, TBPQ, through a surface-induced aryl-aryl coupling. Regions of TBPQ coexist with regions of disordered multiply linked molecules. The conversion of monomer TPBP to dimers is confirmed using ToF-SIMS. Our results demonstrate an alternative, solution-phase approach to the formation of large molecules and nano-structures by coupling reactions.