Database Investigation of Halogen Bonding and Halogen···Halogen Interactions between Porphyrins: Emergence of Robust Supramolecular Motifs and Frameworks

Abstract

We provide a Cambridge Structural Database (CSD) analysis of the role of halogen bonds and halogen···halogen interactions in the solid-state structures of porphyrins. This survey provides a detailed view of halogens in porphyrin self-assembly, highlighting interaction motifs beyond the often considered iodine-based halogen bonds. Particularly notable are the observations of self-assembly through β-positioned substituents, the role of the pyrrole π-system as a halogen bond acceptor, and an abundance of chlorine-based halogen···halogen and halogen-bonding motifs. This overview enabled the observation and systematic classification of complex, multipoint recognition motifs in halogen-based architectures. Similarly to synthons in hydrogen-bonded crystal engineering, these motifs appear in discrete molecular assemblies and can also underlie the formation of two- and three-dimensional frameworks. The systematic categorization of these robust motifs provides a foundation for the design of complex halogen-based supramolecular architectures.