Molecular Recognition Process in Resorcinarene‐based Coordination Capsules

Abstract

Cu and Ag capsules can take up various organic molecules. Their molecular recognition possibly involves partial dissociation and slippage. We investigated molecular recognition processes in Cu and Ag capsules by CD and 1H NMR spectroscopy and employed 4,4’‐diacetoxy biphenyl carrying two benzothiadiazole groups as a probe. CD and 1H NMR measurements reveal that the host‐guest complexation proceeds under second‐order reactions and that these capsules undergo partial dissociation to take up the probe in [D1]chloroform and [D8]THF. Slippage also contributes to host‐guest complexation for a Cu capsule that carries p‐methoxyphenyl groups on the 2,2’‐bipyridiyl arms. DFT calculations suggest that π/π stacking interactions between the electron‐rich p‐methoxyphenyl group and the electron‐poor 2,2’‐bipyridyl arm elongate the capsule, allowing the guest to access the cavity without partial dissociation.

Supramolecular Handshakes: Characterization of Urea‐Carboxylate Interactions Within Calixarene Frameworks

“…Namely, the role of molecular capsule as a nanoreactor or a drug delivery device implies two basic criteria with respect to the design of a capsular host: a larger cavity and the possibility of reversible opening and closing, followed by the release or capture of a desired cargo. [2][3][4][5][6] A tool that enables these prerequisites is provided by non-covalent synthesis, where self-assembly or hetero-assembly of molecular monomers into a capsule is realized via intermolecular interactions such as metal-ligand coordination bonds, [7][8][9][10][11] hydrogen bonds, [12][13][14] ionic interactions, [15] halogen [16] or chalcogen [17] bonds. The control over the association can be imposed by adjusting the physico-chemical properties of the solution (e. g. pH, [18,19] temperature, ionic strength).…”