Parallel face-to-face arene-arene binding energies between benzene and multi-halo substituted aromatics and between tyrptophan and multi-halo substituted aromatics were calculated at the MP2( full)/6-311G** level of theory. A correlation was investigated between the binding energy and either the quadrupole moment (Theta(zz)) or the sum of the Hammett substituent constant sigma(p)(Sigma sigma(p)) of the substituted aromatic. For both benzene and tryptophan, an excellent correlation was found between the calculated binding energy with multi-halo substituted aromatics and the sum of the Sigma sigma(p) values of the substituted aromatics. (C) 2008 Elsevier B.V. All rights reserved.