Complex formation of cyclomaltononaose δ-cyclodextrin (δ-CD) with macrocyclic compounds

Abstract

The complex forming ability of δ-cyclodextrin δ-CD with 7 kinds of macrocyclic compounds (MCCs) with 8-15 carbon atoms in the ring as models of large guest molecules was studied in aqueous solution and compared with the complexation properties of α-, β- and γ-CD. Both α- and β-CD formed relatively stable complexes with small MCCs, while γ- and δ-CD were more efficient in binding larger MCCs. The solid MCC/δ-CD complexes were precipitated with the larger MCCs with 11-15 carbon atoms in the ring, while no such precipitates were obtained with smaller MCCs with only 8-10 carbon atoms in the ring. The formation of the solid complexes was confirmed by powder X-ray diffractometry and differential scanning calorimetry. The cell dimensions of cycloundecanone (11 carbon atoms in the ring)/δ-CD complex were determined by X-ray crystallography. The preliminary crystal data were: Monoclinic, P21, a=32.50 (2) Å, b=19.02 (3) Å, c=16.60 (1) Å, β=98.37 (5)°, V=10148 (16) Å3.