Gold(III) complexes with phenazine and quinoxaline: The role of molecular symmetry in intra- and intermolecular interactions

Regardless of different stoichiometric ratio of the starting [AuCl4]− complex and phenazine (phz) or quinoxaline (qx), only gold(III) complexes with monodentate coordinated diazaaromatic ligands have been isolated and characterized by NMR and X-ray diffraction techniques. In crystals, [AuCl3(phz)] (1) and [AuCl3(qx)] (2) complexes are engaged in columnar π⋯π stacking interactions, but the degree of the ring overlap is higher in C1 symmetrical 2 than in C2 symmetrical 1. It was found that the nature of the ligand had a significant impact on the involvement of the uncoordinated nitrogen atom in intermolecular interactions. Thus, in 2 this nitrogen is an acceptor of C–H⋯N hydrogen bond formed around inversion centers, while in 1 it is engaged in an exceptionally short N⋯Cl (metal coordinated) intermolecular contact. The two complexes also differ in the relative orientation of the heteroaromatic ring with respect to the coordination plane (perpendicular in 1 versus inclined in 2). This in turn influences the degree and mode of molecular overlap in stacks and appearance of intramolecular Au⋯H short contacts in crystals of complex 1.

Two gold(III) complexes with monodentatly coordinated phenazine and quinoxaline ligands, [AuCl3(phenazine)] and [AuCl3(quinoxaline)], have been synthesized and fully structurally characterized. Crystallographic study of these complexes revealed that their molecular symmetry had an evident influence on the type of intra- and intermolecular interactions.Figure optionsDownload as PowerPoint slide