Carbohydrate‐Appended TQNPEN [N,N,N′,N′‐Tetrakis(2‐quinolylmethyl)‐3‐aza‐1,5‐pentanediamine] Derivatives for Fluorescence Detection of Intracellular Cd2+

Abstract

Carbohydrate‐appended TQNPEN [N,N,N′,N′‐tetrakis(2‐quinolylmethyl)‐3‐aza‐1,5‐pentanediamine] derivatives were developed as intracellular fluorescent Cd2+ sensors. Glucose (L1), galactose (L2), and maltose (L3) were utilized as sugar moieties. All glycosylated derivatives exhibit a fluorescence increase (ICd/I0 = 11–25) at 415 nm upon addition of 1 equiv. of Cd2+; however, 1 equiv. of Zn2+ induces negligible fluorescence change due to weak metal–ligand interaction (IZn/I0 = 3, IZn/ICd = 11–31 %). The properties of the Cd2+ complex with parent TQNPEN, including maximum fluorescence wavelength and lifetime, Cd2+ specificity of the fluorescence, and strong metal binding affinity, were well preserved in L1–L3. The intracellular Cd2+ detection was successfully achieved by glucose‐ and galactose‐appended derivatives L1 and L2, likely due to enhanced cell membrane permeability and intracellular distribution in HeLa cells.