Halogen Bonding Motifs in Polyhedral Phenylsilsesquioxanes: Effects of Systematic Variations in Geometry or Substitution

Herein we describe the halogen bonding coordination found in the crystal structures of two homologous series of hybrid silsesquioxane (Polyhedral Oligomeric SilsesquioxaneS, or POSS) molecules, with systematic variations in halogen substitution and cluster geometry. Each of these compounds presents highly coordinated three-dimensional motifs. The first examples are a series of three para-iodinated octa-, deca-, and dodecameric phenylsilsesquioxanes, which show a range of symmetry dependent coordination motifs. The second set of examples deal with the structures of the octa-, hexadeca-, and tetraicosa-brominated octaphenylsilsesquioxane, where again significant short contacts are found, which drive the formation different cluster packing motifs. These structures provide unique examples of the complexities of three-dimensional packing motifs and their relationship to the assembly of tunable materials from nanobuilding blocks.