1,8-Naphthyridine modified rhodamine B derivative and Cu2+ complex: colorimetric sensing of thiols in aqueous media

A 1,8-naphthyridine modified rhodamine B derivative (1) has been designed and synthesized. Compound 1 is the first 1,8-naphthyridine-modified rhodamine B sensor that can detect Cu2+ selectively with a dramatic color change from colorless to pink. The complex of 1 and Cu2+ was utilized as a chemosensing ensemble for cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) detection, which showed highly sensitive and selective colorimetric response to Cys, Hcy, and GSH among the tested naturally occurring α-amino acids in EtOH-HEPES (0.02 M, pH 7.4) (3:7, v/v) buffer solution.