A single molecule that acts as a fluorescence sensor for zinc and cadmium and a colorimetric sensor for cobalt

A new metal ion sensor that contains quinoline and pyridylaminophenol has been synthesized. In acetonitrile and in the presence of Zn²⁺, the sensor fluoresces. In contrast, in aqueous solutions the sensor fluoresces in the presence of Cd²⁺. The fluorescence of the molecule is selective for Zn²⁺ or Cd²⁺ and shows no fluorescence with other metal ions. The crystal structure of the Cd²⁺ complex shows coordination through the amide and phenol oxygens, as well as the amine nitrogen of the sensor. The sensor also acts as a colorimetric sensor for Co ²⁺ by changing color from colorless to yellow. The color change is selective for Co²⁺ and is not observed with other metal ions. The unique combination of pyridine and phenol groups with quinoline results in the properties of this sensor.