The dimeric complex of beta-cyclodextrin with 1,13-tridecanedioic acid

The structure of the complex of beta cyclodextrin (PCD) with 1,13-tridecane dioic acid has been determined at low temperature. The compound crystallize s in P1, a = 18.207(6), b = 15.510(5), c = 15.280(6) Angstrom, alpha = 103. 02(3), beta = 113.13(3), gamma = 99.79(3)degrees and D-c = 1.339 gcm(-3) fo r Z = 1. Refinement based on 13134 observed MoK alpha reflections led to a final R = 0.076. The diacid molecules thread through two PCD arranged in di mers thus, forming [g]pseudorotaxanes. The aliphatic chain of the guest has a few weak, non-bonded interactions with the host inside the long hydropho bic cavity. However, the end carboxyl groups form several strong H-bonds wi th the solvent in a fashion similar to other beta CD/carboxylic acid comple xes that have similar building blocks as the present one: beta CD dimers an d carboxylic groups of the guest emerging from their two primary faces. Con versely, in the corresponding complexes with aliphatic monocarboxylic acids the carboxyl groups form carboxylic dimers because they are isolated from the environment inside hydrophobic channels.