Department of Basic Science, Graduate School of Arts and Sciences , The University of Tokyo , 3-8-1 Komaba , Meguro-ku , Tokyo 153-8902 , Japan.
EaStCHEM School of Chemistry , University of Edinburgh , Joseph Black Building, David Brewster Road , Edinburgh EH9 3FJ , Scotland, United Kingdom.
J Am Chem Soc. 2019 Dec 18;141(50):19669-19676. doi: 10.1021/jacs.9b07779. Epub 2019 Dec 9.
Kinetic control of molecular self-assembly remains difficult because of insufficient understanding of molecular self-assembly mechanisms. Here we report the formation of a metastable [PdL] cage structure composed of naphthalene-based ditopic ligands (L) and Pd(II) ions in very high yield (99%) under kinetic control by modulating the energy landscape. When self-assembly occurs with anionic guests in weakly cooordinating solvent then suitable intermedites and the metastable cage is formed. These conditions also prevent further transformation into the thermodynamically decomposed state. The cage formation pathways under kinetic control and the effect of the anions encapsulated on the self-assembly processes were investigated by QASAP (quantitative analysis of self-assembly process) and NASAP (numerical analysis of self-assembly process). It was found that the self-assembly with a preferred guest (BF) proceeds through intermediates composed of no more components than the cage ([PdLX] ( ≤ 2, ≤ 4, X indicates a leaving ligand)) and that the final intramolecular cage-closure step is the rate-determining step. In contrast, a weaker guest (OTf) causes the transient formation of intermediates composed of more components than the cage ([PdLX] ( > 2, > 4)), which are finally converted into the cage.
由于对分子自组装机制的了解不足，分子自组装的动力学控制仍然具有挑战性。在这里，我们报告了在动力学控制下通过调节能量景观，以非常高的产率（99%）形成由基于萘的双齿配体（L）和 Pd（II）离子组成的亚稳[PdL]笼状结构。当与阴离子客体在弱配位溶剂中发生自组装时，合适的中间体和亚稳笼就会形成。这些条件还可以防止进一步转化为热力学分解状态。通过 QASAP（自组装过程的定量分析）和 NASAP（自组装过程的数值分析）研究了动力学控制下的笼形成途径以及被包裹的阴离子对自组装过程的影响。结果发现，具有优先客体（BF）的自组装通过比笼状结构（[PdLX]（≤2，≤4，X 表示离去配体））组成的中间体进行，并且最终的分子内笼闭合步骤是速率决定步骤。相比之下，较弱的客体（OTf）会导致比笼状结构（[PdLX]（>2，>4））组成的中间体的瞬态形成，这些中间体最终转化为笼状结构。
