Computational chemical studies of chiral stationary-phase models: The nature of the Pi interaction in complexes of methyl N-(2-naphthyl) alaninate with N-(3,5-dinitrobenzoyl)leucine n-propylamide

The pi interaction in complexes of (S)-methyl N-(2-naphthyl)alaninate with (S)- and (R)-N-(3,5-dinitrobenzoyl)leucine n-propylamide was investigated with Hartree–Fock and second-order Møller–Plesset perturbation theory calculations using the STO -3G basis set. For each complex, the geometry of the model of the pi interaction (i.e., naphthalene and 1,3-dinitrobenzene) was derived directly from the complex geometry which was relaxed by the semiempirical quantum-mechanical AM 1 method. At the level of treatment used herein, our results are in agreement with our earlier AM 1 interaction energy calculations in which the pi interaction, one of the three primary interactions proposed in models of the aforementioned complexes, is attractive and of equal strength (ca. 0.8 kcal/mol) in both complexes.