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Assessment of scalar relativistic effects on halogen bonding and σ ‐hole properties
Author(s) -
Kolář Michal H.,
Suchá Denisa,
Pitoňák Michal
Publication year - 2020
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.26392
Subject(s) - halogen , relativistic quantum chemistry , scalar (mathematics) , halogen bond , coupled cluster , basis set , chemistry , atom (system on chip) , atomic physics , non covalent interactions , computational chemistry , chemical physics , quantum mechanics , physics , molecule , density functional theory , hydrogen bond , mathematics , organic chemistry , alkyl , geometry , computer science , embedded system
Halogen bond (X‐bond) is a noncovalent interaction between a halogen atom and an electron donor. It is often rationalized by a region of the positive electrostatic potential on the halogen atom, so‐called σ ‐hole. The X‐bond strength increases with the atomic number of the halogen involved; thus, for heavier halogens, relativistic effects become of concern. This poses a challenge for the quantum chemical description of X‐bonded complexes. To quantify scalar relativistic effects (SREs) on the interaction energies and σ ‐hole properties, we have performed highly accurate coupled‐cluster calculations at the complete basis set limit of several X‐bonded complexes and their halogenated monomers. We found that the SREs are comparable in magnitude to the effect of the basis set. The nonrelativistic calculations typically underestimate the attraction by up to 5% or 23% for brominated and iodinated complexes, respectively. Counterintuitively, the electron densities at the bond critical points are larger for SRE‐free calculations than for the relativistic ones. SREs yield smaller, flatter, and more positive σ ‐holes. Finally, we highlight the importance of diffuse functions in the basis sets and provide quantitative arguments for using basis sets with pseudopotentials as an affordable alternative to a more rigorous Douglas‐Kroll‐Hess relativistic theory.