title: Conformational analysis of alkali metal complexes of aspartate dianion and their interactions in gas phase.
abstract: The gas-phase geometry optimizations of mono and dinuclear complexes of dianionic species of aspartic acid, asp(2-) with lithium, sodium and potassium cations were carried out using density functional calculation at the B3LYP/6-311++G(d,p) level. The metal ion affinities (MIAs) of asp(2-) species and its complexes [asp-M](-), M=Li(+), Na(+) and K(+) were determined using the vibrational frequency calculations at the same level of theory. The most stable complex conformer for aspartate complexes with Li(+), Na(+) and K(+) alkali cations were found as a tri-coordinated form. All complexations of [asp-M](-) and [asp-M(2)] complexes were found to be exothermic reactions. Relative bond distances between the alkali metal cation M(+) and the binding atoms of aspartate ion in [asp-M](-) and [asp-M(2)] complexes are in decreasing order: K(+)>Na(+)>Li(+).
authors.affiliation: Supramolecular Chemistry Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Wichien
authors.initials: W
authors.lastname: Sang-Aroon
authors.forename: Vithaya
authors.initials: V
authors.lastname: Ruangpornvisuti
mesh_terms: D000838:Anions; D001224:Aspartic Acid / Q000737:chemistry*; D001665:Binding Sites; D008024:Ligands; D008672:Metals, Alkali / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D013816:Thermodynamics
chemical_list: D000838:Anions; D008024:Ligands; D008672:Metals, Alkali; D001224:Aspartic Acid