Structure, photophysics, electrochemistry, DFT calculation, and in-vitro antioxidant activity of coumarin Schiff base complexes of Group 6 metal carbonyls.

N-[(2-Pyridyl)methyliden]-6-coumarin (L) is synthesized by the condensation of 6-aminocoumarin and pyridine-2-carboxaldehyde. Group-6 tetracarbonyl complexes, [M(CO)(4)(L)] (M=Cr, Mo, and W) are synthesized and characterized by mass spectrometry and NMR, FT-IR and UV-visible spectroscopy. X-ray crystal structure of [Cr(CO)(4)(L)] shows N(pyridine), N(imine) chelation to chromium(0). A supramolecular chain is formed by C-H⋯O and π⋯π interactions. The ligand and the complexes are fluorescent. Cyclic voltammetry of the complexes exhibit quasireversible M(I)/M(0) redox couple. The complexes exhibit potential antioxidant property both in cell free and in-vitro studies and highest activity is observed to [W(CO)(4)(L)]. Density functional theory (DFT) computation has been performed to correlate with the electronic configuration, composition of wave functions with the UV-visible spectra and redox properties.