Interpenetrated Three-Dimensional Networks of Hydrogen-Bonded Organic Species: A Systematic Analysis of the Cambridge Structural Database

Interpenetration in extended three-dimensional (3D) arrays has been investigated by a systematic analysis of the crystallographic structural databases, using an ad hoc version of the program package TOPOS. In this paper we describe the comprehensive results of our investigation of interpenetration in organic hydrogen-bonded 3D arrays from the Cambridge Structural Database. The great interest in the self-assembly of organic molecules into hydrogen-bonded supramolecular arrays has prompted us to investigate these systems at a rather unusual level; that is, beyond the formation of synthons, we have examined the topologies of the resulting networks and looked for their entanglements. Within 3D architectures we have extracted a complete list including 122 different motifs showing the phenomenon of interpenetration (76 unseen by the original authors). These organic networks include species assembled by a single or by different building blocks; they are discussed and classified according to the previously introduced classes of interpenetration and to other criteria peculiar of hydrogen-bonded organic species. Considerations of the possible relations of the building organic species and their network topology and on the factors determining interpenetration are here presented. The paper is also intended as a contribution to the study of the phenomena of polymorphism and supramolecular isomerism and of the crystal engineering of these complex architectures.