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

A C-pyrenyl poly­(methylenephosphine)
(Mn = 4800, Đ =
1.56) was synthesized from the
anionic polymerization of a P-mesityl phosphaalkene. The phosphine
oxide polymer exhibits blue fluorescence in solution (λmax 379, 400 nm, λonset 560 nm; Φ =
0.05) and blue-green fluorescence in the solid state at room temperature
(λmax 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.