Investigation of oxygen-free Sonogashira step growth synthesis of mono-terminated di-tert-butyl-substituted oligo(phenylene ethynylene)s (OPEs)

A series of oligomers, the hetero-coupled mono-terminated di-tert-butyl-substituted phenylene ethynylene dimer, trimer, tetramer, and pentamer have been successfully synthesized in a stepwise process and characterized. Their electronic properties have been studied by UV–vis and fluorescence spectroscopy. Both UV absorption and FL emission maxima have red shift trends with increasing conjugation length of the oligomers. In addition, homo-coupling products inevitably complicate the hetero-coupling reaction. With increasing substituent group size on the terminal alkyne, the amount of homo-coupling product is increased.