Novel An Efficient Fluorescent Probe Based on Calix[4]triazacrown-5 With Naphthalimide Group for Co²⁺, Cd²⁺ and...

A novel naphthalimide-substituted calix[4]triazacrown-5 (Nap-Calix) at cone conformation was designed and synthesized to employ as a fluorescent probe, which enables the simultaneously detection of Co²⁺ and Cd²⁺ metal ions as well as dopamine (DA). ¹H-NMR, ¹³C-NMR, ESI-MS and elemental analysis techniques were carried out to characterize its structure. Cation binding property of Nap-Calix against various metal ions such as Ba²⁺, Co²⁺, Ni²⁺, Pb²⁺, Zn²⁺, and Cd²⁺ exhibited that the sensor selectively binds to Co²⁺ and Cd²⁺ metal ions with a remarkable affinity. Introduction of Co²⁺ and Cd²⁺ metal ions to a solution of Nap-Calix in DMF/water (1:1, v/v) resulted with a new emission band at 370 nm when excited at 283 nm. In addition, the fluorescence sensing affinity of the probe Nap-Calix against a catecholamine neurotransmitter (dopamine) was investigated in a wide range of concentration of DA (0-0.1 mmol L^-1) in 50% DMF/PBS (pH = 5.0). The fluorescence intensity of Nap-Calix, with excitation/emission peaks at 283/327 nm, is highly enhanced by DA. It was also observed that Nap-Calix exhibits excellent fluorescence behavior towards DA with a very low detection limit as 0.21 µmol L^-1.