The C–Cl⋯π interactions inside supramolecular nanotubes of hexaethynylhexamethoxy[6]pericyclyne

Abstract

Model complexes of hexaethynylhexamethoxy[6]pericyclyne (HM6P) molecules, with or without dichloromethane (DCM) guests, have been calculated at the M05-2X/6-311G(d,p) DFT level. Analysis of nonbonding interactions shows that the cohesion of the supramolecular tubular assemblies previously observed in the crystal state, relies mainly on C–H⋯O hydrogen bonds between axial ethynyl and equatorial methoxy substituents of stacked HM6P C₁₈ macrocycles in a cyclohexane-like chair conformation. The intrinsic binding energy of one HM6P molecule with two neighbors is calculated to be more than 40 kcal mol⁻¹. The inner channel of the stacks (of ca. 8 Å diameter) are suitable for hosting DCM molecules. Using the Atoms In Molecules (AIM) theory, the interaction between DCM molecules and surrounding triple bonds is analyzed in terms of σ-hole-directed C–Cl⋯π halogen bonds. A σ-hole-directed Cl⋯Cl interaction between two chlorine atoms of different DCM molecules is also evidenced.