Complexation of Imidazopyridine-Based Cations with a 24-Crown-8 Ether Host: [2]Pseudorotaxane and Partially Threaded Structures

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• 作者：Surisadai I. Moreno-Olivares ; Ruy Cervantes ; Jorge Tiburcio
• 刊名：Journal of Organic Chemistry
• 出版年：2013
• 出版时间：November 1, 2013
• 年：2013
• 卷：78
• 期：21
• 页码：10724-10731
• 全文大小：440K
• 年卷期：v.78,no.21(November 1, 2013)
• ISSN：1520-6904

文摘

A new series of linear molecules derived from 1,2-bis(imidazopyridin-2-yl)ethane can fully or partially penetrate the cavity of the dibenzo-24-crown-8 macrocycle to produce a new family of host鈥揼uest complexes. Protonation or alkylation of the nitrogen atoms on the pyridine rings led to an increase in the guest total positive charge up to 4+ and simultaneously generated two new recognition sites (pyridinium motifs) that are in competition with the 1,2-bis(benzimidazole)ethane motif for the crown ether. The relative position of the pyridine ring and the chemical nature of the N-substituent determined the preferred motif and the host鈥揼uest complex geometry: (i) for linear guests with relatively bulky groups (i.e., a benzyl substituent), the 1,2-bis(benzimidazole)ethane motif is favored, leading to a fully threaded complex with a [2]pseudorotaxane geometry; (ii) for small substituents, such as 鈭扝 and 鈭扖H₃ groups, regardless of the guest shape, the pyridinium motifs are preferred, leading to external partially threaded complexes in a 2:1 host to guest stoichiometry.