Molecular Recognition in an Organic Host–Guest Complex: CH···O and CH···π Interactions Completely Control the Crystal Packing and the Host–Guest Complexation

Abstract

The synthesis, crystal structure analysis, theoretical modeling at DFT and semiempirical PM3 levels, and molecular electrostatic potential analysis of an organic host–guest system containing an azapolycyclic system 3 and ethyl acetate are presented. The structure of 3 was charaterized by the presence of seven-connected five-membered rings. Though 3 contained six-saturated nitrogen atoms capable of CH···N interactions, its crystal structure and the host–guest complexation were completely governed by CH···O and CH···π interactions. Further, an aromatic pocket consisting of four phenyl rings from four molecules of 3 existed located in the crystal structure. The guest molecule ethyl acetate trapped inside this aromatic pocket was found to interact with it via three CH···π and two CH···O interactions. A model structure for this host–guest complex was also optimized at DFT level, which showed good agreement with the experimental structure.