Regiocontrolled Synthesis of Ethene-Bridged para-Phenylene Oligomers Based on Pt-II- and Ru-II-Catalyzed Aromatization

We report the regiocontrolled syntheses of ethene-bridged para-phenylene oligomers in three distinct classes by using Pt-II- and Ru-II-catalyzed aromatization. This synthetic approach has been developed based on twofold aromatization of the 1-aryl-2-alkynyl-benzene functionality, which proceeds by distinct regioselectivity for platinum and ruthenium catalysts. Variable-temperature NMR spectra provide evidence that large arrays of these oligomers are prone to twist from planarity. The UV/Vis and photoluminescence (PL) spectra as well as the band gaps of these regularly growing arrays show a pattern of extensive pi conjugation with increasing array sizes, except for in one instance.