New FluorescentChemodosimetric Mechanism for SelectiveRecognition of Selenocysteine by Dansyl-Appended Ruthenium NitrosylComplexes

Selenocysteine (Sec) is a biologically essential amino acid that serves as a crucial component in selenoproteins that play a key role in various cellular functions. Thus, developing a reliable and rapid method for detecting Sec in physiological media is of paramount importance. This report introduces for the first time a novel fluorescent chemodosimetric mechanism for the selective recognition of Sec using dansyl-appended ruthenium nitrosyl complexes. These complexes consist of a tetradentate ligand featuring a π-extended system (<b>L</b> = <i>N</i>,<i>N</i>′-bis(2-hydroxy-1-naphthylidene)-1,2-phenylenediamine) and a monodentate ligand derived from the conjugated dansyl group, which acts as a strong fluorescent signaling unit (<b>ID</b> = dansyl-imidazole, <b>BD</b> = dansyl-benzimidazole). The reaction between Sec and the complexes {RuNO}⁶ = <b>[RuL(NO)(ID)]Cl</b> or <b>[RuL(NO)(BD)]Cl</b> in an aqueous phase enhances fluorescence; as a result, it releases NO^• that has been demonstrated through fluorimetric titrations, UV–vis titrations, ⁷⁷Se NMR, EPR, IR, MS, and electronic density calculations. <b>[RuL(NO)(ID)]Cl</b> and <b>[RuL(NO)(BD)]Cl</b> quantitatively detect Sec within a micromolar concentration range, achieving the limit of detection as low as 0.31 and 0.12 μM, respectively, within just 5 min. Remarkably, these chemodosimeters can also be conveniently employed to detect Sec in living Saccharomyces cerevisiae cells.