title: Rationalizing the structural variability of the exocyclic amino groups in nucleobases and their metal complexes: cytosine and adenine.
abstract: The exocyclic amino groups of cytosine and adenine nucleobases are normally almost flat, with the N atoms essentially sp(2) hybridized and the lone pair largely delocalized into the heterocyclic rings. However, a change to marked pyramidality of the amino group (N then sp(3) hybridized, lone pair essentially localized at N) occurs during i) involvement of an amino proton in strong hydrogen bonding donor conditions or ii) with monofunctional metal coordination following removal of one of the two protons.
authors.affiliation: Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, 1081 HV Amsterdam (The Netherlands). C.FonsecaGuerra@vu.nl.
authors.forename: Célia
authors.initials: C
authors.lastname: Fonseca Guerra
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Sanz Miguel
authors.forename: Andrea
authors.initials: A
authors.lastname: Cebollada
authors.forename: F Matthias
authors.initials: FM
authors.lastname: Bickelhaupt
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lippert
mesh_terms: D000225:Adenine / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003596:Cytosine / Q000737:chemistry*; D006860:Hydrogen Bonding; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D000588:Amines; D008670:Metals; D003596:Cytosine; D000225:Adenine
keywords: DFT calculations; cytosine; hybridization state; metal coordination; nucleobase amino groups