100 μs Luminescence Lifetime Boosts the Excited State Reactivity of a Ruthenium(II)-Anthracene Complex in Photon Upconversion and Photocatalytic Polymerizations with Red Light.

The triplet excited state lifetime of a photosensitizer is an essential parameter for diffusion-controlled energy- and electron-transfer, which occurs usually in a competitive manner to the intrinsic decay of a triplet excited state. Here we show the decisive role of luminescence lifetime in the triplet excited state reactivity toward energy- and electron transfer. Anchoring two phenyl anthracene chromophores to a ruthenium(II) polypyridyl complex (Ru ref) leads to a Ru triad with a luminescence lifetime above 100 μs, which is more than 40 times longer than that of the prototypical complex. The obtained Ru triad sensitizes energy transfer to anthracene-based annihilators more efficiently than Ru ref and enables red-to-blue photon upconversion with a pseudo anti-Stokes shift of 0.94 eV and a moderate upconversion efficiency near 1 % in aerated solution. Particularly, Ru triad allows rapid photoredox catalytic polymerizations of acrylate and acrylamide monomers under aerobic condition with red light, which are kinetically hindered for Ru ref. Our work shows that excited state lifetime of a photosensitizer governs the dynamics of the excited state reactions, which seems an overlooked but important aspect for photochemistry.