A new route to functional polymers: atom-economical synthesis of poly(pyrazolylnaphthalene)s by rhodium-catalyzed oxidative polycoupling of phenylpyrazole and internal diynes

Abstract

A new route for atom-economical synthesis of functional polymers was developed. Oxidative polycoupling of 3,5-dimethyl-1-phenylpyrazole with 4,4′-(α,ω-alkylenedioxy) bis(diphenylacetylene)s and 1,2-diphenyl-1,2-bis[4-(phenylethynyl)phenyl]ethene, respectively, were catalyzed by [Cp*RhCl₂]₂, 1,2,3,4-tetraphenylcyclopenta-1,3-diene and copper(II) acetate in dimethylformamide under stoichiometric imbalance conditions, affording soluble poly(pyrazolylnaphthalene)s in satisfactory yields (isolation yield up to 82%) with high molecular weights (M_w up to 35 700). All the polymers were thermally stable, losing little of their weight at high temperatures of 323–422 °C. They possessed good film-forming property and their thin solid films showed high refractive indices (RI = 1.747 − 1.593) in a wide wavelength region of 400–1000 nm. The polymer carrying tetraphenylethene units displayed a phenomenon of aggregation-induced emission and showed enhanced light emission in the aggregated state. The emission of its nanoaggregates could be quenched efficiently by picric acid in both solution and solid states, suggesting that it is a promising sensitive chemosensor for detecting explosives for real-world applications.