2-Hydroxytryptanthrin and 1-Formyl-2-hydroxytryptanthrin as Fluorescent Metal-ion Sensors and Near-infrared Fluorescent Labeling Reagents

Abstract

2-Hydroxy-1-tryptanthrin (T2OH) and 1-formyl-2-hydroxytryptanthrin (T2OH1CHO) were synthesized as fluorescent metal-ion sensors and near-infrared fluorescent labeling reagents. T2OH was well suited for use as a fluorescent chemosensor for Cu²⁺ and Al³⁺ in an acetonitrile solution, and as a near-infrared fluorescent (λ_{f, max} > 650 nm) labeling reagent. However, it was unable to detect changes in a surrounding aqueous environment (DMSO/H₂O = 1/9, v/v). Meanwhile, T2OH1CHO was well suited for use as a fluorescent chemosensor for Al³⁺ in acetonitrile and aqueous solutions.