title: Complexation of imidazopyridine-based cations with a 24-crown-8 ether host: [2]pseudorotaxane and partially threaded structures.
abstract: 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-guest 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-guest 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 -H and -CH3 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.
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), Avenida IPN 2508, Zacatenco 07360, México D. F., México.
authors.forename: Surisadai I
authors.initials: SI
authors.lastname: Moreno-Olivares
authors.forename: Ruy
authors.initials: R
authors.lastname: Cervantes
authors.forename: Jorge
authors.initials: J
authors.lastname: Tiburcio