MOLECULAR-DYNAMICS OF NOVEL ALPHA-CYCLODEXTRIN ADDUCTS STUDIED BY C-13-NMR RELAXATION

In the presence of poly(ethylene glycol) (PEG), alpha-cyclodextrin for ms a molecular adduct called ''molecular necklace'' that belongs to th e class of polyrotaxanes. The condensation of alpha-cyclodextrin with epichlorohydrin results in the formation of the so-called ''molecular tube'' (MT), a rodlike rigid molecule with an empty hydrophobic cavity that can behave as a host for ions or small organic molecules, MT has been obtained from PEG(3350), considerably longer than the chain used in previous works, This paper reports an NMR investigation of the dyn amic properties, via carbon spin-lattice relaxation technique, of alph a-cyclodextrin, the molecular necklace, and the molecular tube. The re sults show that the molecular tube is really formed by a linear thread of condensed alpha-cyclodextrin molecules and that MT possesses a fas ter reorientational motion than all the other compounds. UV spectrosco py shows that the molecular tube forms a host-guest system with iodine (I-3(-)) in aqueous solution.