Regioselective Alkyne Polyhydrosilylation: Synthesis and Photonic Properties of Poly(silylenevinylene)s

Abstract

Alkyne polyhydrosilylations of 1,2-bis(4-dimethylsilanylphenyl)-1,2-diphenylethene with 4,4′-diethynylbiphenyl, bis(4-ethynyl-2-methylphenyl)dimethylsilane, 3,6-diethynyl-9-heptylcarbazole, 1,1-dimethyl-2,5-bis(4-ethynylphenyl)-3,4-diphenylsilole, and 2,5-bis(2-trimethylsilylethynyl)thiophene were mediated by Rh(PPh3)3Cl in THF in an regioselective fashion, furnishing poly(silylenevinylene)s with high molecular weights (Mw up to 36 500) and stereoregularities (E content up to 100%) in satisfactory yields. All the polymers were processable and thermally stable, losing little of their weights when heated to ≥330 °C. Whereas the polymers were weakly emissive in the solutions, they became strong emitters when aggregated in poor solvents or fabricated as thin films in the solid state, demonstrating a phenomenon of aggregation-enhanced emission. The emissions of the polymers were quenched exponentially by picric acid with quenching constant up to 8.48 × 105 L mol–1, making them as highly sensitive chemosensors for explosive detection. Thin films of the polymers exhibited high refractive indices (RI = 1.7180–1.6102) in the wavelength region of 400–1700 nm, high modified Abbé numbers (vD′ up to 2303.9), and low optical dispersion (D′ down to 0.0004). Their RI values could be tuned to a large extent (Δn = 0.09), and their emissions could be faded by UV irradiation, enabling ready generation of fluorescent patterns without development.