Unraveling the Dynamic Molecular Motions of a Twin-Cavity Cage with Slow Configurational but Rapid Conformational Interconversions

Angew Chem Int Ed Engl. 2024 Apr 11:e202405858. doi: 10.1002/anie.202405858. Online ahead of print.ABSTRACTFeaturing diverse structural motions/changes, dynamic molecular systems hold promise for executing complex tasks. However, their structural complexity presents formidable challenge in elucidating their kinetics, especially when multiple structural motions are intercorrelated. We herein introduce a twin-cavity cage that features interconvertible C3- and C1-configurations, each configuration exhibiting interchangeable P- and M-conformations. This molecule is therefore composed of four interconnected chiral species (P)-C3, (M)-C3, (P)-C1, (M)-C1. We showcase an effective methodology to decouple these sophisticated structural changes into two kinetically distinct pathways. Utilizing time-dependent 1H NMR spectroscopy at various temperatures, which disregards the transition between mirror-image conformations, we first determine the rate constant (kc) for C3- to C1-configuration interconversion; while time-dependent circular dichroism spectroscopy at different temperatures quantifies the observed rate constant (kobs) of ensemble of all structural changes. As kobs >> kc, it allows us to decouple the overall molecular motions into a slow configurational transformation and rapid conformational interconversions, the latter further dissected into two independent conformational interchanges, namely (P)-C3 ⇄ (M)-C3 and (P)-C1 ⇄ (M)-C1. This work therefore sheds light on com...

Source: Angewandte Chemie - April 11, 2024 Category: Chemistry Authors: Yong Zuo Zhenghong Chen Ziying Li Enguang Fu Yonghang Xin Chenhao Chen Chenfei Li Shaodong Zhang Source Type: research