Versatile manganese porphyrin, capable of detecting iodide anions by spectrophotometric and electrochemical methods

The versatility of metalloporphyrins, particularly Mn(III) porphyrins, as sensitive compounds for the spectrophotometric and electrochemical detection of various analytes, including iodide anions [1], arises from the extended aromaticity of the porphyrin macrocycle, the nature of its peripheral functional groups, and the properties of the central metal ion.

Electrochemical studies have demonstrated the applicability of manganese-based metalloporphyrins in the detection of hydrogen peroxide, the analysis of protein interactions, salicylate sensing, and the development of glucose biosensors [2–5].

In the present study, Mn(III)-5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-21H,23H-porphyrin chloride (Mn-3,4-diMeOPP) was investigated as a promising candidate for the selective and sensitive detection of iodide anions. Iodide detection was successfully achieved using both UV–Vis spectrophotometry and electrochemical techniques, including cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results indicate that, at low iodide concentrations, the detection process is diffusion-controlled, whereas at higher concentrations, iodide adsorption becomes the dominant mechanism.

The UV–Vis method enables the quantification of iodide ions over the concentration range of 7.9 × 10⁻⁸ M to 1.49 × 10⁻⁶ M, with a limit of detection (LOD) of 2.5 × 10⁻⁸ M. Electroanalytical quantification using a graphite electrode modified with Mn-3,4-diMeOPP gives also a proper detection of iodide ions. The graphite electrode contains 1.2749 mg·cm^‒2 porphyrin (E3) give the best results in the range of 7.812 × 10^‒8 ‒ 1 × 10^‒5 M (correlation coefficient = 0.9941; calibration slope = 26,336).