Sulfonamides Are an Overlooked Class of Electron Donors in Luminogenic Luciferins and Fluorescent Dyes

Many fluorophores, and all bright light-emitting substrates for firefly luciferase, contain hydroxyl or amine electron donors. Here we show that sulfonamides can serve as replacements for these canonical groups. Unlike “caged” carboxamides, sulfonamide analogues enable bioluminescence, and sulfonamidyl luciferins, coumarins, rhodols, and rhodamines are fluorescent in water. Sulfonamide donors thus have previously unappreciated potential to expand the functional repertoire of luminescent molecules.