Arene ruthenium(II) complexes with 3-acetyl coumarin derivatives bearing a 3-hydroxy-2-naphthoic hydrazide moiety: Synthesis, DFT calculations and antioxidant studies

The reaction of [(arene)RuCl2]2 with coumarin hydrazone ligands in methanol yielded neutral chelating mononuclear NnO metal complexes having the general formula [(arene)Ru(L)Cl] where arene = p-cymene, benzene; and L = 3-hydroxy-N'-(1-(2-oxo-2H-chromen-3-yl)ethylidene)-2-naphthohydrazide (L1), 3-hydroxyN'-(1-(7-methoxy-2-oxo-2H-chromen-3-yl)ethylidene)-2-naphthohydrazide (L2), (E)-N'-(1-(6-bromo-2-oxo-2Hchromen-3-yl)ethylidene)-3-hydroxy-2-naphthohydrazide (L3) and 3-hydroxy-N'-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene)-2-naphthohydrazide (L4)}. All complexes (1-8) were fully characterized by spectroscopic techniques like IR, UV-Vis, NMR and ESI-MS spectral methods. The solid-state molecular structures of the three complexes were determined using a single-crystal X-ray diffraction study. The studies revealed that the ligands binding mode to the ruthenium metal centers is through the azomethine nitrogen and the imidolate oxygen forming a five-membered chelating ring. All the complexes and the ligands were screened for antibacterial and antioxidant activity studies. Some of the complexes exhibited antioxidant activity that is more prominent than their respective ligands.