Abstract The orbital electronegativities in the nine aromatic hydrocarbons were estimated on the basis of the ionization potentials and the appearance potentials of the doubly-charged ions. Then, by applying the principle of electronegativity equalization to molecular complexes, the orbital electronegativities in typical electron acceptors were evaluated. The ionic character in single and crystal complexes were discussed in terms of the electronegativities of the component molecules. Consideration of neither the ionization potential of the donor molecule, the electron affinity of the acceptor molecule, nor the orbital electronegativities appeared to be enough to define the ionic character in a complex.