Synthesis and Luminescence of Oligomers Containing Multiple Styrene Chromophores Regioselectively Separated by 2,2-Propylidene and 1,2-Isobutylidene Bridges

Abstract

Oligomers incorporating styrene chromophores, linked by 1,2-isobutylidene and 2,2-propylidene spacers in various proportions, are synthesized through the NiCl₂(PPh₃)₂-catalyzed olefination-oligomerization of benzene-bisdithioacetal under diverse conditions using excess MeMgI and ZnI₂. The method provides a convenient pathway for selectively synthesizing oligomers with distinct ratios of one-carbon and two-carbon linkers, strategically employed to spatially separate adjacent vinylarene chromophores. The emission profiles for these oligomers span from 380 to 450 nm, in addition to the intrinsic emission of styrene ≈315 nm. The intensity of the blue light emission varies depending on the ratio of the aliphatic linkers, attributed to through-space intrachain ground-state interactions among the styrene chromophores. Consequently, emission properties can be finely tuned; π-conjugated chromophores enriched with 2,2-propylidene linkers display higher luminescence intensity with discernible vibronic structure compared to those with higher percentages of 1,2-isobutylidene spacers. This difference underscores the folding behaviors of the oligomers, where even slight structural variations in the oligomer structure can markedly influence their 3D conformation. Importantly, these experimental findings are corroborated by molecular dynamic simulations.