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A valence bond description of the bromine halogen bond
Author(s) -
Franchini Davide,
Gei Alessandro,
Dapiaggi Federico,
Pieraccini Stefano,
Sironi Maurizio
Publication year - 2019
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.25946
Subject(s) - substituent , chemistry , halogen , halogen bond , valence bond theory , bromine , valence (chemistry) , modern valence bond theory , atom (system on chip) , atomic orbital , computational chemistry , acceptor , valence electron , bond order , bond strength , chemical physics , molecular orbital , electron , crystallography , bond length , molecule , stereochemistry , crystal structure , physics , quantum mechanics , organic chemistry , alkyl , adhesive , layer (electronics) , computer science , embedded system
Abstract A theoretical investigation on the nature of the halogen bond through a valence‐bond approach has been carried out with two main goals: (a) finding further confirmations of already existing explanations on the physical origins of the halogen bond and (b) possibly enriching the current models with new details. To achieve these goals we have exploited the spin‐coupled method and we have performed computations on RBr⋯NH 3 dimers characterized by a different electron withdrawing power of substituent R to the bromine atom. The analysis of typical spin‐coupled descriptors (eg, shapes and overlaps of the spin‐coupled orbitals, weights of the spin‐coupled structures) in the different cases and in function of the distance between the monomers allowed us to draw qualitative conclusions about the formation and the strength of the halogen bonds. In particular, the investigation not only confirmed the validity of already existing models (ie, σ‐hole and lump‐hole models) but also highlighted interesting new features, such as the fact that the depletion of electron density around the bromine atom does not extend only toward the acceptor of the halogen bond, but also in the opposite direction (toward the substituent of the halogen), thus forming a sort of σ‐tunnel, rather than a simple σ‐hole.