Light emitting oligomers containing 2,3,4,5-tetraphenylthiophenyl moiety and silyl linkage

Abstract

Light emitting oligomers of high photoluminescence (PL) quantum efficiency were prepared and emphasized in this study. Thereby, four light emitting oligomers containing 2,3,4,5-tetraphenylthiophene (TP) moiety were prepared by Heck coupling between 2,5-bis(4-bromophenyl)-3,4-diphenylthiophene and four diene monomers. Certain diene monomers containing silyl unit were especially used in an attempt to introduce π–σ conjugation into the oligomeric products. Four products exhibited similar UV-Vis absorption and emission properties, with their absorption maxima ( λ max) ranged from 338 to 391 nm and emission maxima (PL max) from 487 to 505 nm. Quantum efficiency for the photoluminescent process was enhanced due to the inherently alternative phenylene–thiophene ring structure in the TP moiety and the silyl units introduced. Quantum efficiency was particularly increased from 28% to a value of 61–74%, if products were prepared from silyl-containing dienes instead of simple aliphatic diene monomer. With the incorporation of bulky TP moiety, four products were basically amorphous in nature and exhibited thermal stability at elevated temperatures.