Theoretical Study of a Conformational Change Occurring with Lithium Complexation to a Tetra-aza Macrocycle Containing 2,2′-Bipyridines

Abstract

Abstract Ab initio Hartree–Fock theory was used to determine the structures of model molecules of a dibutyl dicyano tetra-aza macrocycle (1) containing 2,2′-bipyridines and their lithium complexes. Energy profiles for the conformational inversion, which is closely related to the complexation process of a lithium cation, were also studied. Macrocycles having cyano groups on the bridge methylene carbons were found to be good macrocyclic models related to the macrocycle (1). The energy profiles of stationary points and the vibrational frequencies of macrocycles and their lithium complexes reveal that conformational inversion in the lithium complexes is plausible after lithium complexation. The difference in the vibrational frequencies corresponding to the movement of the lithium cation suggests that C2v-like skeletons in the macrocyclic moiety have a stronger interaction between the lithium cation and coordinating nitrogens than the C2h structure.