Novel porphyrin anion receptors: Synthesis, uses in sensors and modeling of binding

The synthesis of a series of novel porphyrin anion receptors was carried out based upon the previously reported synthesis of meso-tetrakis[(2-arylphenylurea)phenyl]porphyrins; these novel porphyrins serve as good nitrate ionophores when constructed into a suitable solvent polymeric ion selective sensor membrane. These novel receptors exhibited an improved detection limit and linear measurement range for analytical determination of nitrate. A better selectivity over the common interference chloride was achieved and greater stability for the novel ionophores was observed. Initial computational explorations into the binding modes of these porphyrin anion receptors revealed that the thiourea derivatives offered better conformations for good non-bonding weak thiourea hydrogen anion interactions that better stabilize the nitrate versus chloride bound form. A tractable model of binding was achieved that may offer a good scheme to assist in the design of improved anion receptors in the future, based upon preliminary correlation of DFT calculations with experimental selectivity coefficients.