Characterization of a trihydrogen bond on the basis of the topology of the electron density

Recent DFT calculations have predicted unexpected molecular structures for the ion induced dipole clusters H(n)(-) (3 ≤ n-odd ≤ 13). Analysis of these calculations suggests the definition of a new bond, called the trihydogen bond (THB). This is placed in context by a review and classification of multihydrogen interactions as usually discussed in the literature. The results of analysis related to the trihydrogen bond are presented. These include a series of linear relations exhibited by the H(n)(-) clusters involving the charge carried by the central H(-) ion, the binding energy of the clusters, and the relative stabilization of the central anion H(-) with respect to the energy of a free H(-) atom.