title: Anion-pi interactions in bisadenine derivatives: a combined crystallographic and theoretical study.
abstract: In this manuscript we report a high-level ab initio study of anion-pi interactions involving N9-methyl-adenine, N6-methyl-adenine, N9-methyl-hypoxanthine, a dimer of N9-methyl-adenine, and N9,N9'-trimethylene-bisadenine. DNA bases like adenine are electron-deficient arenes that are well suited for interacting favorably with anions. We demonstrate that these compounds are able to interact favorably with anions. N9-Methyl-adenine, N6-methyl-adenine, and the dimer of N9-methyl-adenine interact with the anion via the six-membered ring more strongly than adenine due to cooperativity effects between the noncovalent pi-pi and anion-pi interactions. This pattern, i.e., coexistence of pi-pi and anion-pi bonding, is observed experimentally in the solid state. Finally, we report the solid-state characterization of two new compounds N6,N6'-dimethylene-bisadenine hydrochloride and an outer-sphere complex of protonated N9,N9'-trimethylene-bishypoxanthine with zinc tetrachloride anion, that exhibit interesting anion-pi interactions. They are in strong agreement with high-level theoretical calculations.
authors.affiliation: Department of Chemistry, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, E-07122 Palma de Mallorca, Spain.
authors.forename: Angel
authors.initials: A
authors.lastname: Garcia-Raso
authors.forename: Francisca M
authors.initials: FM
authors.lastname: Albertí
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Fiol
authors.forename: Andres
authors.initials: A
authors.lastname: Tasada
authors.forename: Miquel
authors.initials: M
authors.lastname: Barceló-Oliver
authors.forename: Elies
authors.initials: E
authors.lastname: Molins
authors.forename: Daniel
authors.initials: D
authors.lastname: Escudero
authors.forename: Antonio
authors.initials: A
authors.lastname: Frontera
authors.forename: David
authors.initials: D
authors.lastname: Quiñonero
authors.forename: Pere M
authors.initials: PM
authors.lastname: Deyà