Effect of Host and Guest Structures on Hydrogen Bonding Association

The study of the electrochemical reduction of several quinones, Q, in the presence of alcohols, and diols, with different chemical structures is reported. From the stoichiometry and the formation constants of the different association complexes, obtained from voltammetric results, mole-fraction distribution and average-number-of-ligand diagrams were constructed to analyze structural effects on hydrogen bonding association between the quinone dianion species and the alcohols. It was demonstrated that the association process can be determined by the quinone basicity, steric effects, and by the α-hydrogens in the quinone nucleus. The quinone basicity determines the strength of the association process when no α-hydrogens are present. Meanwhile, the strength of this interaction is intensified when the number of α-hydrogens is increased in the quinone nucleus. The passage from a situation of an association sterically controlled to a situation controlled by the basicity of the quinone can be modulated with the structure and the amount of the hydrogen-bonding donor present in the medium.