title: Complexation behavior of a highly preorganized 7,7-diphenylnorbornane-derived macrocycle: towards the design of molecular clocks.
abstract: The syntheses of two new cyclophane hosts, 4 and 6, are described. The main difference between them is the higher degree of preorganization of 4 as a consequence of the inclusion of the 7,7-diphenylnorbornane (DPN) subunit. The inner cavity of 4 adopts a belt-shaped structure, while 6 has a twisted geometry. In the solid state, the molecules of macrocycle 6 are stacked along an axis to form nanotubular structures. Compounds 4 and 6 form two of the strongest complexes between arene cyclophanes and Ag(+) reported up to date. The silver cation is located inside the cavity of the macrocycles. The stability of 4.Ag(+) is considerably higher than that of 6.Ag(+). The additional stabilization of 4.Ag(+) is attributed to higher preorganization of macrocycle 4. DNMR experiments as well as theoretical calculations carried out with 4.Ag(+) show evidence of Ag(+)-hopping between two different binding sites inside the macrocycle. This phenomenon could be the basis for the design of molecular clocks.
authors.affiliation: Departamento de Química Orgánica Facultad de Ciencias Químicas, Universidad Complutense Ciudad Universitaria, 28040 Madrid, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: García Martínez
authors.forename: José
authors.initials: J
authors.lastname: Osío Barcina
authors.forename: María del Rosario
authors.initials: Mdel R
authors.lastname: Colorado Heras
authors.forename: Alvaro de Fresno
authors.initials: Ade F
authors.lastname: Cerezo
authors.forename: María del Rosario
authors.initials: Mdel R
authors.lastname: Torres Salvador