Spectroscopic properties and stabilities of metal complexes using coumarin derivatives substituted with methyl, chloro, and nitro groups

New coumarin derivatives C1, C2, and C3 with different substituents (methylphenyl, chlorophenyl, and nitrophenyl) were prepared and characterized using various spectroscopic techniques. C1 and C2 display luminescence when excited at 325 nm, while C3 has weak emission at 335 nm. The binding properties of these derivatives toward transition metals and lanthanum cations were studied using UV-visible absorption spectroscopy, and the former cations were found to form ML₂ complexes by titration method. The chelation of each ligand with metal cations induced changes in their luminescence properties.