iClick-Mediated Au(I) Functionalization of Polystyrene: Lighting Up Polystyrene with Phosphorescence

Abstract

A series of polystyrene-based polymers that are randomly functionalized with Au(I) chromophores that exhibit phosphorescence and electrophosphorescence are reported. The polymers feature side-chain conjugated moieties that are based on R₃P–Au(I)–C≡C–Ar (where Ar = phenyl or 1-naphthyl and R = ethyl or phenyl) and a novel digold triazole functionality that is derived from an iClick reaction between R₃P–Au(I)–N₃ and the R₃P–Au(I)–C≡C–Ar units. The R₃P–Au(I)-C≡C–Ar substituted polymers are prepared by the reaction of R₃P–AuCl with the ethynyl-functionalized polystyrenes (10 mol % ethynyl groups). Subsequently, an iClick reaction is carried out on the R₃P–Au(I)–C≡C–Ar functionalized polymers to afford the digold triazole functionalized polymers. The iClick reactions are monitored by in situ ¹H and ³¹P NMR spectroscopy. Molecular dynamics (MD) simulations of the monogold R₃P–Au(I)–C≡C–Ar polymers reveal that there are significant attractive interactions between the metalated repeat units, especially in the polymers featuring triethylphosphine ligands at the Au(I) centers (e.g., Et₃P–Au(I)–C≡C–Ar). The photophysical study of the polymers reveals that the emission is dominated by phosphorescence from ³π,π* excited states localized on the metalated units. The phenyl-based polymers exhibit phosphorescence in the blue region (λ_max ∼ 435 nm), whereas the naphthyl-based polymers exhibit yellow-red phosphorescence (λ_max ∼ 600 nm). Preliminary studies demonstrate the application of side-chain functionalized polymers in electroluminescent devices.