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

Abstract

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.

Substituent Effects on Non‐Covalent Interactions with Aromatic Rings: Insights from Computational Chemistry

“…A strong linear correlation between the value of the electrostatic Figure 9. a) Global minimum C 6 H 5 F···H 2 O complex, featuring H···F and CH···O interactions, rather than OH/p interactions, as reported by Brutschy et al [60] b) Low-lying conformer of reported by Neusser and coworkers. [61] potential minimum and the cation/p binding energy was found.…”

“…The effect of aryl fluorine substitution on OH/p interactions have also been discussed. [60,62] For example, Brutschy et al showed [60] that the global minimum complexes of water with fluorobenzene and p-difluorobenzene do not actually exhibit an OH/p interaction, but instead feature a cyclic arrangement of OH···F and CH···O interactions (see Figure 9 a). For the C 6 F 6 -H 2 O complex, the global minimum structure also does not exhibit an OH/p interaction, but instead has both H atoms pointing away from the ring (i.e.…”

The ν19a band of fluorobenzene

“…The fluorobenzene molecule has received considerable attention from quite different fields of research, ranging from its interest in cation-p interactions in biological molecules [1], as environmentally relevant species among other aromatic molecules [2], or in the study of van der Waals systems, formed by aromatic molecules linked to a rare gas atom [3][4][5] or to other species like methanol, N 2 or water [6][7][8]. On the other hand, the vibrotational spectroscopy of this molecule has been scarcely studied, mainly because the large moment of inertia of the molecule induces a crowded rovibrational spectrum, and makes the analysis complicated.…”

A velocity map ion imaging study of difluorobenzene-water complexes: Binding energies and recoil distributions

“…7 This is consistent with earlier calculations. 8,9 The remaining H atom appears to lie out of the plane. This change in the nature of the aromatic-water interaction has led us to explore the complexes of water with the series of difluorobenzenes ͑DFBs͒, viz.…”

“…A number of studies of the pDFB-H 2 O complex have been reported, [7][8][9]14,15 however, studies of the ortho and meta isomers appear restricted to a Ph.D thesis. 10 The S 1 ← S 0 transition of the pDFB-H 2 O complex has been studied using both one and two-color 1 + 1 REMPI.…”