The design of functional organic materials for current and future applications such as sensing, catalysis, separation, and pharmacological applications commonly relies on surface-supported receptors binding reversibly with exogenous ligands. It is imperative to understand the interaction of the surface-supported receptors, the surface, and the ligands in order to improve on current designs. In this study, we compare, quantitatively, the affinity of Co(II)octaethylporphyrin for 4-methoxypyridine when the porphyrin is in solution and at the HOPG/solution interface. The reaction was found to be reversible in both environments with results indicating that binding in solution phase is slightly more stable. UV-Visible spectroscopy was used to determine the free energy for the reaction in solution, ΔG<sub>soln</sub> =-16.8±0.2 kJ/mol, and scanning tunneling microscopy (STM) was used to determine the value at the solution/HOPG interface, ΔG<sub>surf</sub> =-13.0±0.3 kJ/mol. STM images were also used for nearest neighbor analysis and showed a positive cooperative ligand binding behavior. This study uses single molecules and ensemble level techniques to gain insights into the general principles of reversible ligand binding at the solution/solid interface. We believe these insights are important for the growth of the functional materials design field.

Affinity and cooperativity of reversible ligand binding to Co(II) porphyrin receptors at the solution/solid interface

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.