Polymorphism in an 18-membered macrocycle: an energetic and topological approach to understand the supramolecular structure

Abstract

The synthesis, crystallization, and theoretical calculations (energetic dimers and QTAIM analyses) of three polymorphs of 3,12-dihydrotetrabenzo[d,h,m,q]-[1–3, 10–12]hexaazacyclooctadeca-1,10-dien-5,14-diyne are reported. The supramolecular cluster approach is proposed for understanding the formation and stabilization of crystal arrangements of the polymorphs. The results show that the π⋯π-interactions were responsible for the crystal packing of the three polymorphs and that they are in a determined energetic region. The energetic difference between the more stable and less stable polymorphs is around 8 kcal mol⁻¹, indicating that if, probably other polymorphs will be formed, all of them will be in the same energetic region. The results confirmed that the first molecular coordination sphere (supramolecular cluster) is the smallest portion of the crystal that represents all necessary energy information for understanding the intermolecular interactions in the entire crystal.