Structure of Organic Crystals with Molecules Lying on Twofold Crystallographic Axes. Structural Class C2, Z = 2(2)

Abstract

A comparative analysis is performed for 44 structures from the rare structural class C2, Z = 2(2) with molecules lying on the twofold crystallographic axes. The overwhelming majority of these structures (42 of 44) have distinct chains (or rods) where molecules are “strung” on the 2 axis forming very effective (according to their contribution to crystal energy) intermolecular contacts. The chains form layers grouped into two structural subclasses: 1) layers with a primitive lattice (12 structures) and 2) layers with a centered lattice (30 structures). Detailed crystal-chemical analysis has been performed for six structures from each subclass. Specific intermolecular contacts leading to formation of the given structural class and dictating the choice of the subclass are discussed.