The experimental electron density distribution in the complex of (E)-1,2-bis(4-pyridyl)ethylene with 1,4-diiodotetrafluorobenzene at 90 K.

The experimental electron density of the donor-acceptor complex of (E)-1,2-bis(4-pyridyl)ethylene (bpe) with 1,4-diiodotetrafluorobenzene (F(4)DIB) at 90 K has been determined with the aspherical atom formalism and analyzed by means of the topological theory of molecular structure. The bpe and F(4)DIB molecules are connected by intermolecular I.N bonds into infinite 1D chains. F.H bonds link these chains together to form the crystal assembly. The topological analysis reveals that the Cbond;I bond is of the "closed shell" type. Its bond-critical properties run parallel to those found in metal-metal and metal-ligand bonds of organometallic compounds. The integrated net charges show that the I.N halogen bond has an essentially electrostatic nature. F.F, F.C, and C.C intermolecular interactions, for which a bond path was found, contribute to reinforce the crystal structure.