Is σ-hole an electronic exchange channel in YX⋯CO interactions?

DUARTE, D. J. R.; BURALLI, GABRIEL J; PERUCHENA, N. M.

SANTIAGO

Congreso; QUITEL2018- XLIV International Congress of Theoretical Chemists of Latin Expression; 2018

ASOCIACION DE QUIMICOS TEORICOS DE EXPRESION LATINA

The σ-hole concept (electrostatic model) explains many features of the halogen bonds (XB), such as its directionality and the ability of the halogen atoms to interact favorably with Lewis base. However, recently Stone shows that the geometries of the XBs are not always determined by electrostatics component. In particular, the strong tendency to linearity of these interactions is a consequence of exchange-repulsion component, not electrostatics [1]. In addition, Syzgantseva et al show that in FBr∙∙∙NH3 complex at long-range, the electrostatic interactions are the dominant ones (as expected from the σ-hole model) and the exchange component is very important for the stabilization of the complex [2]. In this same sense, we have shown that as the σ-hole magnitude increases the exchange term of the XBs X∙∙∙N in the complexes [(FX)n/NH3 with n=1-5 and X= Cl, Br] increases accordingly [3]. These findings lead us to thinking that the σ-hole magnitude could not be just an indicator of the electrostatic part of the interaction, but also a channel that facilitates the rest of the stabilizing factors, especially the electronic exchange between interacting atoms. In the present work, a theoretical study of linear YX∙∙∙CO XBs (in which YX are diatomic interhalogens or hydrogen halide) has been performed to high-level quantum chemical calculations. These show that at the equilibrium geometry, the stabilizing effect that arises from the Pauli exclusion principle is more important than the electrostatic interactions. In addition, the stabilizing terms of the LMOEDA scheme increase with the σ-hole magnitude, being the exchange term the most affected one, followed by electrostatics, polarization and dispersion components. The PAEM function measured on the X∙∙∙C interatomic interaction line gives a measure of the covalence of these interactions.Acknowledgements: G. J. Buralli, D. J. R. Duarte and N. M. Peruchena acknowledge SEGCYT-UNNE and CONICET for financial support.References:[1] A. J. Stone, J. Am. Chem. Soc. 135 (2013) 7005.[2] O. A. Syzgantseva, V. Tognetti, L. Joubert, J. Phys. Chem. A 117 (2013) 8969.[3] G. J. Buralli, A. N. Petelski, N. M. Peruchena, G. L. Sosa, J. R. Duarte, Molecules 22 (2017) 1.