Examination of Halogen Bonding Interactions in Electronically Distinct but Structurally Related Tris(haloarenes)

Solid-state halogen bonding interactions present in four families of structurally similar tritopic haloarenes were examined in an effort to identify molecular features that promote halogen···carbonyl, halogen···halogen, and/or halogen···π interactions. The substrates used in this study all featured three haloarene substituents attached to a central 1,3,5-substituted arene ring with conformationally flexible linkers (ketone or ester groups) in order to systematically vary the polarization of the aryl halogen groups. Within each individual substrate type, however, there was found to be little correlation in the halogen bonding motifs exhibited as a function of halogen present (I, Br, and Cl). In general, the iodoarene derivatives examined exhibited a greater degree of halogen bonding interactions than the bromo and chloro analogues, and a unique bifurcated I···I/I···OC halogen bonding synthon was identified in two substrates. Halogen bonding contacts observed in tritopic iodoarenes correlated nicely with electrostatic potentials of simpler model compounds determined using computational methods. This study highlights the difficulty in attempting to empirically correlate halogen bonding with molecular structure.