title: Halogen Bonding versus Hydrogen Bonding: A Molecular Orbital Perspective.
abstract: We have carried out extensive computational analyses of the structure and bonding mechanism in trihalides DX⋅⋅⋅A(-) and the analogous hydrogen-bonded complexes DH⋅⋅⋅A(-) (D, X, A=F, Cl, Br, I) using relativistic density functional theory (DFT) at zeroth-order regular approximation ZORA-BP86/TZ2P. One purpose was to obtain a set of consistent data from which reliable trends in structure and stability can be inferred over a large range of systems. The main objective was to achieve a detailed understanding of the nature of halogen bonds, how they resemble, and also how they differ from, the better understood hydrogen bonds. Thus, we present an accurate physical model of the halogen bond based on quantitative Kohn-Sham molecular orbital (MO) theory, energy decomposition analyses (EDA) and Voronoi deformation density (VDD) analyses of the charge distribution. It appears that the halogen bond in DX⋅⋅⋅A(-) arises not only from classical electrostatic attraction but also receives substantial stabilization from HOMO-LUMO interactions between the lone pair of A(-) and the σ* orbital of D-X.
authors.affiliation: Department of Theoretical Chemistry, Amsterdam Center for Multiscale Modeling, Vrije Universiteit Amsterdam De Boelelaan 1083, 1081 HV Amsterdam (The Netherlands) E-mail: F.M.Bickelhaupt@vu.nl.
authors.forename: Lando P
authors.initials: LP
authors.lastname: Wolters
authors.affiliation: Department of Theoretical Chemistry, Amsterdam Center for Multiscale Modeling, Vrije Universiteit Amsterdam De Boelelaan 1083, 1081 HV Amsterdam (The Netherlands) E-mail: F.M.Bickelhaupt@vu.nl.
authors.forename: F Matthias
authors.initials: FM
authors.lastname: Bickelhaupt
keywords: activation strain models; bond theories; density functional calculations; halogen bonds; hydrogen bonds