A fluorescence sensor for Zn²⁺ that also acts as a visible sensor for Co²⁺ and Cu²⁺

Monitoring Zn²⁺ levels in biological environments with fluorescent sensors is important. This paper gives the synthesis and properties of a new Zn²⁺ sensor based on quinoline and pyridylaminophenol. The sensor is selective for Zn²⁺ and remains fluorescent when bound to Zn² even in the presence of other metal ions. Along with fluorescing when bound to Zn²⁺, the sensor becomes colored when Cu²⁺ or Co²⁺ is added to it. These two metal ions result in the sensor becoming yellow. The crystal structure of the Cu-sensor complex shows that all of the sensor's nitrogens are bound to the metal ion. In studies with living cells, the fluorescence intensity of the sensor correlates to the concentration of Zn²⁺.