Study on cooperativity ofmetal-OH2 and H2O...H2O bonds in H2O…H2O−M (M= Li+, Na+, K+, Rb+, Ca2+, Sr2+, Ba2+ and La3+) systems

The role and importance of non-covalent interactions especially hydrogen bond,have generally been detected in recent decades.Theseinteractions play an important role in chemistry and physics, and furthermore, they have a key importance in the arrangement of biological structures such as DNA [1].In this work,we try to investigate the cooperativity between a Mn+−OH2 bond and a H2O...H2O hydrogen bond. In fact, the nature and strength of each metal-OH2 bondand H2O...H2O hydrogen bondin a triad system is compared with primary dyad systems.Herein we investigate the H2O…H2O−M(M= Li+, Na+, K+, Rb+, Ca2+, Sr2+, Ba2+ and La3+)compounds, theoretically. The geometries of all compounds in the gas-phase were fully optimized with def2-TZVPD basis set at MP2 and M06 levels of theory using the Gaussian 09 set of programs. The different types of interaction and stabilization energies [2]were calculated and corrected for the basis set superposition error (BSSE) [3].In order to study the cooperativity in these systems, a newly presented method was used[2].The data showed that the total cooperativity of triad correlateswell with the sum of the changes in values of Mn+-OH2andH2O...H2O interactions,upon the formation of H2O...H2O−Mn+ triad.