Inclusion of Azulene and Alcohol by β-Cyclodextrin in Aqueous Solution

β-Cyclodextrin (β-CD) has been found to form a ternary inclusion complex with alcohol and azulene, with a stoichiometry of 2:2:1. By means of a fluorescence method, equilibrium constants for the formation of the ternary inclusion complex have been evaluated for alcohols from ethanol to 1-pentanol. Induced circular dichroism studies suggest that in the ternary inclusion complex azulene slightly extrudes from the β-CD cavity compared with a 1:1 inclusion complex between β-CD and azulene. From an analysis of a ¹H-NMR spectrum for azulene in D₂O containing both β-CD and 1-propanol, 1-propanol incorporated into the β-CD cavity is deduced to be in close proximity to H-2 and H-6 of azulene in the ternary inclusion complex.