Molecular Recognition Process in Resorcinarene-based Coordination Capsules

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 the 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 the partial dissociation to take up the probe in [D1]chloroform and [D8]THF. The 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 pi/pi 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 the partial dissociation. Cu and Ag capsules accommodate various organic molecules. We investigated the processes by which these capsules perform molecular recognition utilizing a molecular probe. It was found that partial dissociation is a major molecular recognition process, while in some cases, slippage also contributes to host-guest complexation.+image

Automated summary

Cu and Ag capsules were found to have the ability to take up various organic molecules through partial dissociation and slippage, as revealed by CD and 1H NMR spectroscopy. The study also demonstrated that partial dissociation is the major molecular recognition process, while slippage can also contribute to host-guest complexation in certain cases.