Divalent samarium compounds are important reagents for reductive transformations in organic chemistry. However, currently, a high amount of this reagent is required in most reactions, and it also necessitates the use of harmful chemicals. To address this issue, researchers have developed a visible-light-antenna ligand that coordinates with stable trivalent samarium compounds, which, upon exposure to visible light, are reduced to divalent samarium, enabling milder conditions and smaller amounts of samarium for reactions.