Self-Assembly of Supramolecular Architectures Driven by σ-Hole Interactions: A Halogen-Bonded 2D Network Based on a Diiminedibromido Gold(III) Complex and Tribromide Building Blocks

The reaction of the complex [Au(phen)Br-2](PF6) (phen = 1,10-phenanthroline) with molecular dibromine afforded {[Au(phen)Br-2](Br-3)}(infinity) (1). Single crystal diffraction analysis showed that the [Au(phen)Br-2](+) complex cations were bridged by asymmetric tribromide anions to form infinite zig-zag chains featuring the motif center dot center dot center dot Au-Br center dot center dot center dot Br-Br-Br center dot center dot center dot Au-Br center dot center dot center dot Br-Br-Br center dot center dot center dot. The complex cation played an unprecedented halogen bonding (XB) donor role engaging type-I and type-II XB noncovalent interactions of comparable strength with symmetry related [Br-3](-) anions. A network of hydrogen bonds connects parallel chains in an infinite 2D network, contributing to the layered supramolecular architecture. DFT calculations allowed clarification of the nature of the XB interactions, showing the interplay between orbital mixing, analyzed at the NBO level, and electrostatic contribution, explored based on the molecular potential energy (MEP) maps of the interacting synthons.