Gold() complexes with redox active BIAN and MIAN ligands: synthesis, structure and electrochemistry

A series of cationic Au( i )-BIAN/MIAN complexes, namely [(PPh 3 )Au(L)]OTf, where L = dpp-bian ( 1 ), dpp-mian ( 2 ), 2-Me-Ph-bian ( 3 ) and 4-Me-Ph-bian ( 4 ), has been prepared. All complexes were characterized by analytical and spectroscopic methods and their crystal structures were determined by X-ray diffraction analysis. In all structures, an asymmetric mode of coordination of the di- or monoimine ligand (one shortened Au-N bond and the second elongated Au-N(O) bond) was found, which is a consequence of the so-called antichelate effect. The analysis of the bonding in the coordination environment of gold( i ) and the coordination geometry in cations 1-4 was carried out using DFT calculations. The cyclic voltammograms of 1-4 in dichloromethane featured a series of ligand-centered redox processes in the cathodic region. Preliminary bioactivity tests for complexes 1-4 and respective imine ligands have been performed. This article reports on the synthesis and structure of novel cationic gold( i ) complexes with BIAN/MIAN ligands, displaying redox activity and the antichelate effect.