A C‑Pyrenyl Poly(methylenephosphine): Oxidation “Turns On” Blue Photoluminescence in Solution and the Solid State

A C-pyrenyl poly­(methylenephosphine) (<i>M</i>_n = 4800, <i>Đ</i> = 1.56) was synthesized from the anionic polymerization of a P-mesityl phosphaalkene. The phosphine oxide polymer exhibits blue fluorescence in solution (λ_max 379, 400 nm, λ_onset 560 nm; Φ = 0.05) and blue-green fluorescence in the solid state at room temperature (λ_max 460 nm, Φ = 0.07). In contrast, unoxidized polymer displays only a weak emission in solution and no emission in the solid state. Fluorescence studies of partially oxidized polymers (50, 75, 83% oxidation) indicate that “turn on” emission occurs only at very high degrees of oxidation (near 100%). We conclude that even a small number of unoxidized phosphine moieties within the partially oxidized polymer intramolecularly quench the fluorescence