Prediction of Redox Potentials of Adrenaline and Its Supramolecular Complex with Glycine: Theoretical and Experimental Studies

Protonated adrenaline (PAd) can be oxidized to protonated adrenaline quinone (PAdquinone) through a one-step, two-electron redox reaction. The electron-transfer property of PAd and its supramolecular complex with glycine has been investigated by cyclic voltammetry (CV) experiment and theoretical calculations. From CV curves, the conditional formal redox potential E degrees' of PAd/PAdquinone couple at the pH value of 0.29 is determined to be 0.540 V. The calculated E degrees' using the G3MP2//B3LYP method and the B3LYP method with 6-31G(d,p), 6-31+G(d,p), 6-311G(d,p), and B3LYP/6-311+G-(d,p) basis sets are in reasonable agreement with the experimental value. PAd can form supramolecular complex (PAd-Gly) with glycine (Gly) through hydrogen bond (H-bond), and the calculated E degrees' values of PAd-Gly/PAdquinone-Gly redox couple are larger than those of PAd/PAdquinone couple. The theoretical results are in good agreement with the experimental finding that the formation of H-bonds weaken the electron-donating ability of PAd.