Fluorobenzene⋯water and difluorobenzene⋯water systems: An ab initio investigation

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 diflu...