title: A Schiff base lateral macrobicycle derived from 4,13-diaza-18-crown-6 in its protonated form.
abstract: In the structure of the title compound, 28,31,36,39-tetraoxa-9,17,42-triaza-1,25-diazoniapentacyclo[23.8.5.1(11,15).0(3,8).0(18,23)]nonatriaconta-3,5,7,9,11,13,15,16,18,20,22-undecene bis(perchlorate), C33H43N5O(4)2+.2ClO4- or (H2L)(ClO4)2, the cation and one of the two independent anions lie on crystallographic twofold axes, while the second perchlorate anion is disordered about a centre of inversion. The conformation of the macrobicycle L is conditioned by two strong intramolecular hydrogen-bonding interactions involving the pivot and imine N atoms, and is quite different from that observed when a metal ion is placed inside its cavity. The two imine groups are not coplanar with the pyridine moiety, and the deviation from planarity is considerably larger than that found in the corresponding Ba complex. Moreover, the fold of the macrobicycle in H2L2+ causes a significant approach of the two pivot N atoms compared with their disposition in the Ba complex. This is the first X-ray crystal structure analysis of an uncoordinated Schiff base lateral macrobicycle.
authors.affiliation: Departamento de Química Fundamental, Universidade da Coruña, Campus da Zapateira s/n, E-15071 A Coruña, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Avecilla
authors.forename: David
authors.initials: D
authors.lastname: Esteban
authors.forename: Carlos
authors.initials: C
authors.lastname: Platas-Iglesias
authors.forename: Susana
authors.initials: S
authors.lastname: Fernández-Martínez
authors.forename: Andres
authors.initials: A
authors.lastname: De Blas
authors.forename: Teresa
authors.initials: T
authors.lastname: Rodríguez-Blas