Methoxyquinoline-diethylenetriamine conjugate as a fluorescent zinc sensor

Abstract

A 6-methoxyquinoline conjugated diethylenetriamine derivative, N,N′′-bis(6-methoxy-2-quinolylmethyl)diethylenetriamine (6-MeOBQDIEN) has been synthesized and its fluorescent response toward zinc ion was investigated. In the presence of zinc ion, 6-MeOBQDIEN exhibits fluorescence (λ_ex = 329 nm, λ_em = 418 nm, ϕ = 0.039). The fluorescent intensity of the zinc complex of the compound is two times higher than the parent BQDIEN (ϕ = 0.021) under the same conditions. The crystal structure of 6-MeOBQDIEN-Zn complex shows that all five nitrogen atoms participate to the metal coordination in a distorted square-pyramidal geometry (τ = 0.145) with the aliphatic nitrogen in an apical position. Fluorescent microscopic analysis using 6-MeOBQDIEN reveals the zinc ion concentration change in living cells.