WEAK BONDS IN THE TOPOLOGICAL THEORY OF ATOMS IN MOLECULES

Ab initio calculations of the electron density in the benzene-tetracyanoethylene (TCNE) complex (three conformations), the guanidinium cyanoformide ionic pair, the kekulene molecule, the trinitromethanide anion, and the C60-Ne complex reveal the existence of unusual weak bonds as defined within the framework of Bader's theory of atoms in molecules. These bonds challenge the traditional ideas about bonding in organic molecules. The features that allow for distinguishing between two classes of weak bonds are discussed.