Experimental and theoretical study of aromatic-aromatic interactions.: Association enthalpies and central and distributed multipole electric moments analysis

Aromatic-aromatic interactions are studied experimentally through heat capacity measurements that, with the aid of an association model, provide an estimate of the association enthalpy of the aromatic-aromatic complexes formed in solution. These enthalpies are empirically correlated with the product of the quadrupole moments of the molecules involved. The compounds used in this work are hexafluorobenzene (HFB), pentafluorobenzene (PFB), triflourobenzene (TFB), flourobenzene, (FB), benzene (BEN), toluene (TOL), naphthalene (NAP), and 1-methylnaphthalene (MEN). The 10 pairs studied are HFB-MEN, HFB-BEN, HFB-TOL, NAP-HFB, PFB-MEN, PFB-BEN, HFB-FB, BEN-MEN, FB-MEN, and TFB-MEN. The electrostatic interaction between the molecules forming the 10 aromatic-aromatic pairs is calculated expressing their charge distributions in terms of both central and distributed multipole electric moments. It is concluded that the changes in association enthalpies of aromatic-aromatic complexes can be explained by the electrostatic contribution to the interaction energy.