New insights on microscopic interpretation of adsorption isotherms of ionophores (manganese–porphyrin complexes) using statistical physics formalism

Equilibrium adsorbed amounts of manganese on porphyrins were determined at 288 K and 308 K using the quartz crystal microbalance strategy. The experimental measurements were achieved in order to compare the adsorption capacities of the tetratolylporphyrin and the tetraphenylporphyrin for ionophore investigation. The aim of this work is to examine these isotherms at the ionic scale in order to elucidate physical clarifications about the microscopic interactions between the manganese ions and the two complexing porphyrins (TTP and TPP). Indeed, statistical physics formalism is employed by the intermediate of the parameters contained in the expressions of the single-layer and the quadruple-layer models to evaluate the materials employed for ionophore fabrication. Results indicated that high attraction was shown between manganese ions and the sites of tetratolylporphyrins. Energetic investigation (through statistical physics approach and density functional theory method) revealed that the Mn–TTP complex was chemically bonded. The interpretation of the van der Waals parameters confirms the highest stability of the Mn(Cl)2–TTP among all complexes. This study contributes new tips on the theoretical and the experimental understanding of ionophore adsorption. The novel results of this research are the Mn(Cl)2 is the most useful adsorbate material because chlorine ions do not have any impact on the complexation mechanism and the tetratolylporphyrin is the finest complexing adsorbent in terms of stability.