The roles of ligands proton affinity, π-back donation and metal fragment hardness on the Au-N bond in N-donor heterocycles gold(III) complexes

A DFT study on the Au-N interaction for some groups of N-donor heterocycles L in AuX3L complexes is reported. The π-acceptor ability of the 5-membered N-donor ligands resulted in all the cases greater than that of the 6-membered N-heterocycles. The minimum proton affinity average value for an interaction between the N-heterocycles and gold(III) has been estimated; this parameter does not depend on the electronic features of the coordinated ligands. The sensitivity of AuX3 towards ligands proton affinity has been related to the metal fragment relative hardness.