Water Soluble Cationic Porphyrin Sensor for Detection of Hg²⁺, Pb²⁺, Cd²⁺, and Cu²⁺

Abstract

Here we report the sensing properties of the aqueous solution of meso -tetra(N-methyl-4-pyridyl)porphine tetrachloride ( 1 ) for simultaneous detection of toxic metal ions by using UV-vis spectroscopy. Cationic porphyrin 1 displayed different electronic absorptions in UV-vis region upon interacting with Hg 2+ , Pb 2+ , Cd 2+ , and Cu 2+ ions in neutral water solution at room temperature. Quite interestingly, the porphyrin 1 showed that it can function as a single optical chemical sensor and/or metal ion receptor capable of detecting two or more toxic metal ions, particularly Hg 2+ , Pb 2+ , and Cd 2+ ions coexisting in a water sample. Porphyrin 1 in an aqueous solution provides a unique UV-vis sensing system for the determination of Cd 2+ in the presence of larger metal ions such as Hg 2+ , or Pb 2+ . Finally, the examination of the sensing properties of 1 demonstrated that it can operate as a Cu 2+ ion selective sensor via metal displacement from the 1-Hg 2+ , 1-Pb 2+ , and 1-Cd 2+ .