beta-cyclodextrin nonanoic acid 1:1 complex

The structure of the complex of cyclomaltoheptaose (beta-CD) with nonanoic acid, beta-cyclodextrin-nonanoic acid (1/1) water solvate, 2C(42)H(70)0(35).1.6C(9)H(18)O(2).23.9H(2)O, has been determined at room temperature. Two independent molecules of beta-CD form a dimer which encloses two molecules of nonanoic acid. The guest molecules penetrate the beta-CD cavities to different depths. Their carboxylic groups point towards the primary hydroxyl region of beta-CDs forming direct dimers through hydrogen bonds with the carboxylic groups of adjacent guests along the a axis and interact with water molecules and disordered primary hydroxyl O atoms.