Characterization of two types of intermolecular interactions on halogen monoxide monohydrates

Abstract

Monohydrates of halogen monoxides ClO.H2O and BrO.H2O have been studied by means of DFT (B3LYP) and ab initio (MP2) correlated calculations with aug-cc-pVnZ basis sets ranging from triple- up to quintuple-zeta. These complexes might be formed in the troposphere and stratosphere and participate in chemical reactions involved in ozone depletion. Two stable structures are found that differ in the intermolecular interaction which takes place, namely: conventional XO...HOH hydrogen bond and OX...OH2 halogen bond. We demonstrate that both types of interactions participate in the formation of these complexes yet all the computational methods tested predict a slightly greater stability for the latter OX...O link. Both intermolecular interactions are characterized upon analyzing electron density distribution, charge transfer effects, and electron localization domains. These analyses reveal the central role played by electron redistribution. Because of this, the greater spatial extent of the electron density in Cl or Br as compared to H could be the main cause to yield a slightly greater stability for the O-X...O halogen bond with respect to the O...H-O hydrogen bond.

Communication: Interaction of BrO radical with the surface of water

“…Figure 2(a) shows the radial distribution functions (RDFs) for (BrO)Br· · ·O(water) and (BrO)O· · ·H(water). Interestingly, the results show that the RDF for (BrO)Br· · · O(water) exhibits a peak at the distance of r = 2.4 Å and a valley is at r = 2.8 Å, which is close to the (BrO)Br· · ·O(water) bond distance (2.8 Å) in the global-minimum configuration of the BrO·H 2 O complex at 0 K. 10,15,16 This result indicates that the interaction of (BrO)Br· · ·O(water) at the surface of a water slab is much weaker than that in the gas phase, due to the competitive interactions between (water)H· · ·O(water) and (BrO)Br· · ·O(water) in the water slab. On the other hand, the peak of the RDF for (BrO)O· · ·H(water) appears at r = 2.0 Å, consistent with the (BrO)O· · ·H(water) distance (2.0 Å) in the global-minimum configuration of the BrO·H 2 O complex at 0 K. 10,15,16 This result can be explained by the fact that water molecules tend to expose their H site at the air/water interface, which would favor the hydrogen bonding formation of (BrO)O· · ·H(water).…”

“…[5][6][7][8][9][10][11][12][13][14] The key species involved in the chemistry is the BrO·H 2 O complex. 10,15,16 Gálvez et al 15 have studied the equilibrium geometries, energies, and properties of the BrO hydrates by means of ab initio calculations. Upon analyzing electron density distribution, the intermolecular interactions for the formation of halogen oxide and water molecule complexes are characterized.…”

“…Upon analyzing electron density distribution, the intermolecular interactions for the formation of halogen oxide and water molecule complexes are characterized. 16 In another study, Hoehn et al employed RCCSD(T)/aug-cc-pVQZ level electronic structure calculations to derive an analytic potential energy function for the interaction between a BrO radical and a water molecule. 10 Most studies of the BrO radical have been focused on the gas-phase interaction.…”

Analytic ab initio-based molecular interaction potential for the BrO⋅H2O complex

“…[11][12][13][14][23][24][25][26][27][28][29][30][31] However, bromine and its monoxide radical have been the subject of very few of such investigations. 33,34 Gálvez et al 33 have reported the equilibrium structures, the energetics, and the properties of the BrO-hydrates using density functional theory coupled with second order Moller-Plesset perturbation theory. In an additional study, Gálvez et al 34 employ stationary state methods to characterize the interactions involved in the formation of halogen oxides and water molecule complexes by electron density analysis.…”

“…33,34 Gálvez et al 33 have reported the equilibrium structures, the energetics, and the properties of the BrO-hydrates using density functional theory coupled with second order Moller-Plesset perturbation theory. In an additional study, Gálvez et al 34 employ stationary state methods to characterize the interactions involved in the formation of halogen oxides and water molecule complexes by electron density analysis. 34 These previous works concentrate on stationary point calculations, yet it is essential to generate an effective map of the PES of this complex both to model chemical processes and to facilitate dynamic molecular simulations.…”