Model of peptide bond-aromatic ring interaction:: Correlated ab initio quantum chemical study

Aromatic ring-peptide bond interactions (modeled as benzene and formamide, N-methylformamide and N-methylacetamide) are studied by means of advanced computational chemistry methods: second-order Moller-Plesset (MP2), coupled-cluster single and double excitation model [CCSD(T)], and density functional theory with dispersion (DFT-D). The geometrical preferences of these interactions as well as their interaction energy content, in both parallel and T-shaped arrangements, are investigated. The stabilization energy reaches a value of over 5 kcal/mol for the N-methylformamide-benzene complex at the CCSD(T)/complete basis set (CBS) level. Decomposition of interaction energy by the DFT-symmetry-adapted perturbation treatment (SAPT) technique shows that the parallel and T-shaped arrangements, although similar in their total interaction energies, differ significantly in the proportion of electrostatic and dispersion terms.