Entropically driven binding in a self-assembling molecular capsule.
The encapsulation of molecules within larger molecular or supramolecular cages (see ref. 1 for examples) brings about many interesting phenomena, among them the stabilization of reactive intermediates, new forms of stereoisomerism, and templating of the cage itself. Here we describe a self-assembling hydrogen-bonded molecular capsule that encapsulates guest molecules in a reversible, apparently entropy-driven process, giving rise to unusual temperature dependence of the formation process. The positive entropy of formation--at first sight unexpected--seems to be the result of the fact that more than one solvent molecule is included in the 'bare' cage, making their replacement by a single large molecule (here adamantane or ferrocene) entropically favourable.
Kang
J
J
Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139, USA.
Rebek
J
J
D000218:Adamantane / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D019281:Dimerization; D019277:Entropy; D005296:Ferrous Compounds / Q000737:chemistry; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D000075163:Metallocenes; D012996:Solutions; D013696:Temperature
D005296:Ferrous Compounds; D000075163:Metallocenes; D012996:Solutions; D000218:Adamantane; C004998:ferrocene