Structural properties and the effect of interaction of alkali (Li+, Na+, K+) and alkaline earth (Be2+, Mg2+, Ca2+) metal cations with G and SG-tetrads

The interaction between alkali (Li+, Na+, K+) and alkaline earth (Be2+, Mg2+, Ca2+) metal cations with G and SG-tetrads were studied using ab initio and density functional theory methods. The calculations reveal that cation-G and SG-tetrad complexes adopt normal four-stranded Hoogsteen bonded structures. The substitution of different cations on G and SG-tetrads, affect the geometries and charge distributions. The gas phase binding sequence between the cations-G and SG-tetrads follows the interaction energy and metal ion affinity stability order Li+>Na+>K+, Be2+>Mg2+>Ca2+. The smaller ions are tightly bonded to G and SG-tetrads suggest the domination of electrostatic interaction in the cation-tetraplexes systems. The solvent interaction with the molecular systems has increased the stability of the G, SG-tetrads and their complexes. The two and three-body interaction energies have been used to analyze the influence of a metal cation on the stability of tetrads. Electrostatic potential map of the tetrads have been plotted and the binding of cations have also been shown. Atoms in Molecules theory (AIM) have been performed to study the hydrogen bonds in the metal interacting complexes. (C) 2011 Elsevier B.V. All rights reserved.