New Criterion for Conformational Polymorphism

An analysis of nonvalent interactions in 29 crystal structures of compounds that have the CaHbNcOd composition (salicylaldoxime, glycine, and 2,4,6,8,10,12-hexaazaisowurzitane) and form polymorphic modifications is performed using molecular Voronoi-Dirichlet polyhedra. It is found that each conformational polymorph is characterized by a unique combination of the types of intramolecular and intermolecular nonvalent interactions. It is shown that a criterion which takes into account the total number of intramolecular nonvalent contacts and their distribution depending on the nature of neighboring atoms and the rank of faces of molecular Voronoi-Dirichlet polyhedra can be used to reveal conformational polymorphs.