Molecular Paneling by Coordination:An M_15L_6 Hexahedral Molecular Capsule having Clefts for Reversible Guest Inclusion

摘要

The construction of three-dimensional (3D) molecular -uctures by linking two-dimensional (2D), planar organic mponents through metal coordination provides anew ncept that is termed molecular panelingJ1] A family of 2D mponents are coordinated by transition metals to give rise various hollow 3D polyhedral structures.[2-8] The triangular o-hexadentate ligand 2 has been recently shown to give 18L6 hexahedral coordination capsule 4 by linking together th Pdll building block V4b] This coordination capsule has a very stable closed-shell structure which makes it difficult to encapsulate guest molecules.We have designed another molecular panel 3,which is similar to 2 but misses one binding site,to prepare a hexahedral capsule with more flexibility that would allow guest encapsulation and release. We show that, despite the lack of one binding site, ligand 3 is assembled into a unique M1SL6 hexahedral structure 5 without the formation of any other positional isomers. An important finding is that capsule 5 can encapsulate/exchange guest molecules reversibly through the clefts at the nonbinding sites of the capsule.