Recently, Brutschy and co-workers have reported the spectra of (substituted benzene)⋯(H2O)n systems. To investigate the possibility of these systems exhibiting a π-H kind of bonding interaction as observed in benzene⋯(H2O)n systems, we have carried out extensive ab initio calculations on different conformations of the fluorobenzene⋯(H2O) and p-difluorobenzene⋯(H2O) systems using various basis sets. Our results indicate that unlike the π interaction observed in benzene⋯(H2O)n, the O-H of the water molecule is involved in the formation of a six-membered ring system with the F-C-C-H of the aromatic ring. This six-membered ring which results from the formation of two H-bonds (water hydrogen and fluorine, water oxygen and benzene hydrogen), is extensively stabilized by electrostatic interactions. The strength of this σ-bonding interaction of water to fluorobenzene in C6H5F⋯H2O is nearly equal to the corresponding π-bonding interaction of water to benzene in C6H6⋯H2O. However the σ interaction of water to difluorobenzene in p-C6H4F2⋯H2O is somewhat higher than the π interaction in C6H6⋯H2O and slightly higher than the corresponding interaction in C6H5F⋯H2O. The frequency shifts of the predicted OH stretching modes are in reasonable agreement with the experimental vibrational frequency shifts for both C6H5F⋯H2O and p-C6H4F2⋯H2O.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry