Functional Myoglobin Model Composed of a Strapped Porphyrin/Cyclodextrin Supramolecular Complex with an Overhanging COOH That Increases O₂/CO Binding Selectivity in Aqueous Solution

A water-soluble strapped iron(III)tetraarylporphyrin (FeIIIPor-1) bearing two propylpyridinium groups at the side chains and a carboxylic acid group overhanging position of strap was synthesized to mimic function myoglobin with distal polar functionality in aqueous solution. FeIIIPor-1 forms stable 1:1 inclusion complex per-O-methylated β-cyclodextrin dimer having pyridine linker (Py3OCD), providing hydrophobic environment proximal fifth ligand stabilize O2-complex. The ferrous (FeIIPorCD-1) binds both O2 CO binding affinities (P1/2O2 P1/2CO) half-life time (t1/2) FeIIPorCD-1 are 6.3 0.021 Torr, 7 h, respectively, pH 25 °C. control compound without structure (FeIIPorCD-2) has similar oxygen characteristics = 8.0 Torr), but much higher affinity (P1/2CO 3.8 × 10–4 longer t1/2 (30 h). kinetics indicate that inhibits entrance these gaseous ligands into iron(II) center, as evidenced by lower konO2 konCO values. Interestingly, is significantly destabilized (relatively larger koffCO), while koffO2 value smaller than FeIIPorCD-2, resulting increased O2/CO selectivity (reduced M value, where P1/2O2/P1/2CO 320) compared FeIIPorCD-2 (M 21000).