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

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 Hg²⁺, Pb²⁺, Cd²⁺, and Cu²⁺ 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 Hg²⁺, Pb²⁺, and Cd²⁺ ions coexisting in a water sample. Porphyrin 1 in an aqueous solution provides a unique UV-vis sensing system for the determination of Cd²⁺ in the presence of larger metal ions such as Hg²⁺, or Pb²⁺. Finally, the examination of the sensing properties of 1 demonstrated that it can operate as a Cu²⁺ ion selective sensor via metal displacement from the 1-Hg2+, 1-Pb2+, and 1-Cd2+. [ABSTRACT FROM AUTHOR]