Reaction‐Based Europium Complex for Specific Detection of Cysteine Over Homocysteine and Glutathione with Variable‐Temperature Kinetic Studies

A water‐soluble europium(III)‐based probe, EuL, has been designed and synthesized for selective recognition of cysteine (Cys) over other structurally similar thiols and amino derivatives due to formation of a more stable and preferable seven‐membered ring. Addition of Cys shows a significant response with quenching of over 90 % of the initial signal (Hcys: 10.5 %, GSH: 3.6 % respectively). A good linear correlation between the emission intensities and concentrations of Cys has been established. Water‐soluble EuL is highly selective for detection of cysteine (Cys) over other thiol and amino derivatives with a linear relationship correlating the luminescence intensity and the concentration of Cys (5 µm to 80 µm). EuL is stable from pH 4 to 8. Kinetic studies showed that EuL has a higher quenching rate with Cys than both Hcys and GSH.