Bifunctional Hydrogen Bonds in Monohydrated Cycloether Complexes

VALLEJOS, MARGARITA M.; ANGELINA, EMILIO L.; PERUCHENA, NÉLIDA M.

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Año: 2010 vol. 114 p. 2855 - 2863

1089-5639

ABSTRACT In this work, the cooperative effects implicated in bifunctional hydrogen bonds were studied (in monohydrated cycloether) within the framework of the atoms in molecule (AIM) theory and of the Natural Bond Orbital (NBO) analysis. The study was carried out in complexes formed by cyclic ether compounds (tetrahydropyran, 1,4-dioxane and 1,3-dioxane) and a water molecule. These compounds were used as model systems instead of more complicated molecules of biological importance. All the results were obtained at MP2 level theory using 6-311++G(d,p) basis set. Attention was focused on the indicators of cooperative effects that arise when a water molecule interacts simultaneously with a polar and a non polar portion of a cycloether (via bifunctional H-bonds and compared with conventional H-bonds where the water molecule only interacts with the polar portion of the cycloether. Different indicators of H-bonds strength, such as structural and spectroscopic data, electron charge density, population analysis, hyperconjugation energy and charge transference, consistently showed significant cooperative effects in bifunctional hydrogen bonds. From the AIM, as well as from the NBO analysis, the obtained results allowed us to state that in the monohydrated cycloether, where the water molecule plays a dual role, as proton acceptor and proton donor, a mutual reinforcement of the two interactions occurs. Due to this feature, the complexes engaged by bifunctional H-bonds are more stabilized that the complexes linked by conventional H-bonds.