Non-covalent surface modification of metal-macrocycle framework with mono-substituted benzenes

Abstract

Recently, we have reported a metal-macrocycle framework (MMF) with five enantiomerically paired molecular binding pockets that exhibit site-selective guest arrangement on the nano-channel surface in soaking experiments using a variety of guest molecules. The guest inclusion is based largely on molecular exchange between solvent molecules such as CH₃CN and guest molecules on the surface. Herein, we report that the molecular arrangement on the nano-channel surface varies with size, shape and/or chemical properties of functional groups of guests, mono-substituted benzene derivatives, such as benzonitrile, acetophenone and nitrobenzene. In their inclusion complexes, polar nitrile, acetyl and nitro groups serve as molecular anchors to a macrocyclic cavity through hydrogen bonding. Notably, benzonitrile and benzenesulphonic acid bind only to one pair of enantiomeric binding pockets. Such a highly site-selective binding would enable further multi-component surface modifications in the MMF.

Keywords:

• porous material
• nano-channel
• molecular recognition
• mono-substituted benzene
• surface modification

Acknowledgements

This research was supported, in part, by Global COE Program, Chemistry Innovation through Cooperation of Science and Engineering, and KAKENHI (23655117), the Japan Society for the Promotion of Science and MEXT, Japan.