The hydrogen bond (HB) is the subject of various studies since it is important in numerous chemical, physical and biological processes.i,ii,iii,iv One of first definitions of the hydrogen bond was given by Pauling v who stated that “under certain conditions an atom of hydrogen is attracted by rather strong forces to two atoms, instead of only one, so that it may be considered to be acting as a bond between them. This is called the hydrogen bond”. This interaction may be designated as X-H…Y, where X-H is the proton donating bond while Y is the proton acceptor. Pauling pointed out that X and Y atoms should be characterized by the high electronegativity, that the Y proton acceptor should posses at least one free electron pair and that the hydrogen bond is the electrostatic interaction. (more…)

In recent years the σ-hole concept was introduced and developed and it was applied to the halogen bond and to the other non-bonding interactions.i According to this concept the halogen bond is the electrostatic attraction between the positive potential of the halogen and the negative Lewis base center. This is because the half-filled p orbital of halogen participates in the covalent bond and there is an electron deficiency in the outer lobe of this p orbital; it is called the σ-hole. Hence the halogen atom electron deficient side may act as the Lewis acid. Such a situation may occur not only for halogen atoms and the σ-hole bond concept was introduced to discuss more extended class of non-bonding interactions. There are also the other examples of studies on non-bonding interactions; for example, the N…P attractive interaction was analyzed recently.ii (more…)

There are various non-bonding interactions which are important in numerous chemical processes and phenomena.i These interactions may be treated as counterparts or competitors of hydrogen bond. It was found that the common characteristic for them, including hydrogen bond, is the electron charge transfer from the Lewis base to the Lewis acid and that the amount of this transfer corresponds roughly to the strength of the interaction.ii The following non-bonding interactions may be mentioned; the dihydrogen bond, the halogen bond, the agnostic bond, the hydride bond and others. In recent years the σ-hole concept was introduced and developed and it was applied to non-bonding interactions.24f (more…)

Contact person: Sławomir J. Grabowski. email: s.grabowski@ikerbasque.org