IQUIR   05412
INSTITUTO DE QUIMICA ROSARIO
Unidad Ejecutora - UE
artículos
Título:
Preferential Formation of the Different Hydrogen Bonds and Their Effects in Tetrahydrofuran and Tetrahydropyran Microhydrated Complexes
Autor/es:
VALLEJOS, MARGARITA; PERUCHENA, NÉLIDA M.
Revista:
JOURNAL OF PHYSICAL CHEMISTRY A
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 2012 vol. 116 p. 4199 - 4210
ISSN:
1089-5639
Resumen:
The role of cycloether-water (c-w) and
water-water (w-w) hydrogen bonds (H-bonds) on the stability of the
tetrahydrofuran (THF)/(H2O)n and the
tetrahydropyran (THP)/(H2O)n complexes with n
=1-4 was investigated herein using the density functional and ab initio methods
and the atoms in molecules theory. Geometry optimizations for these complexes
were carried out with various possible initial guess structures. It was
revealed that the major contributions of the mono and dihydrated complexes came
from c-w H-bonds. A competition between c-w and w-w H-bonds contribution was
observed for trihydrated complexes. For most of tetrahydrated complexes, the
inter-water H-bonds provided the greatest contribution, whereas the c-w
contributions were small but not negligible. It was confirmed that to produce a hydrophobichydration of cycloethers, the C-H···Ow H-bond shouldbe
associated witha network of H-bonds that connects both portionsof the solute, throughthe formation of a bifunctional
H-bond. A linear correlation is obtained for the sum of electron density at the
bond critical points (rb) with the interaction energy (DE) and with the solute-solvent
interaction energy (DEs-w) of the microhydrated complexes. In
addition, a new way to estimate the energetic contribution as well as the
preferential formation of the different H-bonds based completely on rb
was found. Even more, it allows to differentiate the contribution from c?w
interactions in both hydrophilic and hydrophobic contributions, it is therefore
a useful tool for studying the hydration of large biomolecules. The
analysis of the modifications in the atomic and group properties brought about
by successive addition of H2O molecules allowed
to pinpoint the atoms or molecular groups that undergo the greatest changes in
electron population and energetic stabilization. It was identified that the remarkable stabilization of the water oxygen atoms is crucial for
the stabilization of the complexes.