Sulfoxides are shown to be viable reporting groups for fluorescent chemosensor development. Metal coordination of sulfixdde-appended fluorophores suppresses excited-state pyramidal inversion of the sulfoxide, leading to enhanced fluorescence emission. This new structural motif allows the construction of fluorescent chemosensors that do not require nitrogen coordination as part of the signaling process, that have a range of selectivities and affinities for oxophilic metal ions, and that can function in water.