Structural and Thermodynamic Analysis of a Three-Component Assembly Forming ortho-Iminophenylboronate Esters

Structural studies of a three-component assembly a host and two distinct guests were carried out using a combination of B-11 and H-1 NMR. In aprotic solvent, the imino group that forms ortho to the boronic acid or boronate ester group can form a dative N-B bond. In protic solvent, a molecule of solvent inserts between the nitrogen and boron atoms, partially ionizing the solvent molecule. Additionally, B-11 NMR was used in combination with a seventh-order polynomial to calculate five binding constants for each of the individual steps in protic solvent. Comparison of these binding constants was used to establish positive cooperativity in the binding of the two guests.