π–π Interaction energies in monosubstituted-benzene dimers in parallel- and antiparallel-displaced conformations

Theoretical studies of the π–π interaction energies of a few experimentally important monosubstituted-benzene dimers in both parallel- and antiparallel-displaced forms were performed, selecting the OH group as an electron donor (D) and F, CN and NO2 groups as acceptors (A) according to their importance in organic nonlinear optical materials. The MP2, SCS-MP2, DFT-D and DF-DFT-SAPT methods were employed to calculate and compare the interaction energies. For all dimers (A–A, D–D and D–A), antiparallel-displaced dimers are more stable than the parallel displaced ones. The SAPT analysis indicates that the total interaction energy closely follows the electrostatic interaction energy for all dimers.