Doubling up on optically driven catalysis: During photosynthesis, plants absorb light from the Sun four consecutive times before they accumulate enough energy to make oxygen from water. In contrast, when chemists harness light energy to promote reactivity, they tend to rely on single discrete absorption events. Ghosh et al. now show that a particular dye molecule can channel the combined energy from two absorbed photons to the reduction and subsequent coupling reactions of aryl halide molecules. The method expands the reach of photocatalysis to a broader range of compounds, such as chlorides, which are too stable to breach with a single photon. Science , this issue p. 725

Eosin Y, a long known dye molecule, has recently been widely applied as a photoredox catalyst in organic synthesis.