Counterparts of the Hydrogen Bond

Abstract

Various Lewis acid–Lewis base interactions are described here, mainly those that are comparative to hydrogen bonds. Especially in crystal structures, not only are hydrogen bonds responsible for the arrangement of molecules and ions but also other interactions, for example the halogen bond or the chalcogen bond. The lithium bond was among the first interactions which were compared with the hydrogen bond. Unexpectedly it possesses several features different than those known for the hydrogen bond. In the halogen bond the halogen atom, known as an electronegative centre, plays the role of the Lewis acid; thus, this interaction was a subject of controversies and disputes. The concept of the σ-hole and π-hole regions, which are often characterized by positive electrostatic potential, is also presented here. This concept explains mechanisms of formation of the halogen bond and of other interactions such as tetrel, pnicogen, chalcogen and aerogen bonds. The trials to classify so-called non-covalent interactions are presented.