Non-innocent behavior of 1-(2′-pyridylazo)-2-naphtholate coordinated to polypyridine ruthenium(II) complexes

Abstract

The study of non-innocent redox behavior of ligands is important for the development of new catalysts and to comprehend the function of bioinorganic molecules in biochemical processes. In this work, we present a description of the non-innocent behavior of 1-(2′-pyridylazo)-2-naphtholate (pan) coordinated to ruthenium complexes. The synthesis and characterization of a series of [Ru(pan)(PPh₃)(L)]PF₆ complexes [where L = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (dmbpy), and 1,10-phenanthroline (phen)] are presented. UV–vis analyses of the studied ruthenium complexes show intense absorptions from intraligand π–π* and metal-to-ligand charge-transfer transitions bands in the visible region. This observation shows a significant contribution of the pan ligand in all electronic transitions and is the indicative of non-innocent behavior. Theoretical calculations were carried out to support the UV–vis spectral assignments. Non-innocent behavior of pan was observed and confirmed using the electrochemical parameter E_L(L) and by electrochemical studies. The pan ligand is non-innocent and can be modulated by donor and acceptor character of the other ligands present in the coordination sphere of the complex.

Graphical Abstract

Keywords:

• Ruthenium
• Non-innocent ligand
• Pan
• Electrochemical parameter
• Theoretical calculation

Acknowledgements

This work was supported by the Coordination for the Improvement of Higher Education Personnel (CAPES) for the scholarships to K.C.F. Toledo. The authors would like to thank the Brazilian Council for Scientific and Technological Development (CNPq), Fundação Araucária/Paraná and National Center of High Performance Computing in São Paulo (CENAPAD Project 557/2013).