Oxatub[4]arene: a smart macrocyclic receptor with multiple interconvertible cavities†

Abstract

We report a smart macrocycle with four interconvertible cavities, which can select the best-fit cavity for a given guest.

Abstract

There are a large number of synthetic macrocyclic receptors in the literature. No particular one is suitable for all guests or purposes. For a broader guest binding scope or multiple purposes, a macrocycle with multiple interconvertible cavities will be advantageous. Here, we report a naphthalene-based macrocyclic receptor with an adaptable cavity, namely oxatub[4]arene. It has four representative conformations resulting from the flipping of naphthalene rings, each with a deep and well-defined cavity. Different guests select one host conformer or a combination of conformers. All the four conformers have been detected and characterized based on 2D NMR spectra and X-ray single crystal structures. Thermodynamically, these conformers constitute a reservoir, that responds to the structural changes of guests, and thus maximizes the association free energies. This smart macrocycle may provide a new platform for the construction of molecular machines and devices or stimuli-responsive materials.

Notes

†Electronic supplementary information (ESI) available: Experimental conditions and procedures, syntheses and compound characterizations, ¹H, ¹³C and 2D NMR spectroscopic analyses, mass spectra, ITC titration data and analyses, and X-ray single-crystal structure data and analyses. CCDC 1D1 ²⁺@TA4-IV , 1043635; MeV ²⁺@TA4-III , 1043636. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc03251b