Synthesis of an Adaptable Molecular Barrel and Guest Mediated Stabilization of Its Metastable Higher Homologue.

Structural and functional modulation of three-dimensional artificial macromolecular systems is of immense importance. Designing supramolecular cages that can show stimuli mediated reversible switching between higher-order structures is quite challenging. We report here construction of a Pd trifacial barrel () by coordination self-assembly. Surprisingly, barrel was found to exhibit guest-responsive behavior. In presence of fullerenes C and C, unprecedentedly transformed to its metastable higher homologue Pd tetrafacial barrel (), forming stable host-guest complexes (C)⊂ and (C)⊂, respectively. Again, encapsulated fullerenes could be extracted from the cavity of using 1,2-dichlorobenzene, leading to its facile conversion to the parent trifacial barrel . Such reversible structural interconversion between an adaptable molecular barrel and its guest stabilized higher homologue is an uncommon observation.