Kinetically Protected Carbon-Bridged Oligo(p-phenylenevinylene) Derivatives for Blue Color Amplified Spontaneous Emission

Carbon-bridged oligo(p-phenylenevinylene)s (COPVn with repeating unit n = 1-6) have demonstrated great success as laser dyes for thin-film organic lasers. The excellent photostability observed in the longer homologues is, however, not present in the blue-emitting shorter compounds COPV1 and COPV2, attributed to the unprotected terminal positions that can degrade by photoreaction in the excited state. Here we report the synthesis of various COPV1 and COPV2 derivatives functionalized at the terminal positions with two types of sterically bulky protecting substituents: Tip (2,4,6-triisopropylphenyl) and tertbutyl (t-Bu) groups. Such molecular designs aim at preventing such photodegradation processes and thus to improve their stability. The efficacy of kinetic isotope effect for stabilization is also examined for COPV2, by the addition at terminal positions of deuterium atoms. Absorption, photoluminescence (PL), including PL quantum yield, and amplified spontaneous emission (ASE) studies have been conducted in polystyrene films doped with each of the derivatives. Significant and slight improvements of the ASE photostability are observed for the compounds with Tip groups and deuterium, respectively. Installation of substituents slightly affects the ASE wavelength within the blue spectral region, that is 385-413 nm and 462-474 nm, for COPV1 and COPV2, respectively.