Halogen bond tunability II: the varying roles of electrostatic and dispersion contributions to attraction in halogen bonds
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In a previous study we investigated the effects of aromatic fluorine substitution on the strengths of the halogen bonds in halobenzene…acetone complexes (halo = chloro, bromo, and iodo). In this work, we have examined the origins of these halogen bonds (excluding the iodo systems), more specifically, the relative contributions of electrostatic and dispersion forces in these interactions and how these contributions change when halogen σ-holes are modified. These studies have been carried out using density functional symmetry adapted perturbation theory (DFT-SAPT) and through analyses of intermolecular correlation energies and molecular electrostatic potentials. It is found that electrostatic and dispersion contributions to attraction in halogen bonds vary from complex to complex, but are generally quite similar in magnitude. Not surprisingly, increasing the size and positive nature of a halogen’s σ-hole dramatically enhances the strength of the electrostatic component of the halogen bonding interaction. Not so obviously, halogens with larger, more positive σ-holes tend to exhibit weaker dispersion interactions, which is attributable to the lower local polarizabilities of the larger σ-holes.
KeywordsDispersion Electrostatics Halogen bonding Noncovalent interactions
This work was a part of research Project No. Z40550506 of the Institute of Organic Chemistry and Biochemistry, ASCR and was supported by the Operational Program Research and Development for Innovations - European Regional Development Fund (Project CZ.1.05/2.1.00/03.0058 of the MEYS of the CR). The support of Praemium Academiae, ASCR, awarded to P.H. in 2007 is acknowledged. This work was also supported by the Czech Science Foundation (P208/12/G016).
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