Tungsten(0)-carbonyl complexes of naphthylazoimidazoles

[W(CO)5(α-NaiR-N)] are reported in this work. The complexes have been transformed to [W(CO)4(α-NaiR-N,N′)] at higher temperatures (where α-NaiR-N is a monodentate imidazole-N donor ligand and α-NaiR-N,N′ denotes a bidentate imidazole-N, azo-N donor ligand). The emission of [W(CO)4(α-NaiR-N,N′)] shows a higher quantum yield (ϕ = 0.05-0.07) than [W(CO)5(α-NaiR-N)] (ϕ = 0.01-0.02). Cyclic voltammetry exhibits metal oxidation and ligand reductions. The DFT calculations of [W(CO)5(α-NaiMe-N)] show contributions from the metal d-orbitals and π-orbitals of the CO ligands to the HOMO while the LUMOs are α-NaiMe dominated. The back bonding interaction thus originates from the W(CO)n moiety to the LUMO of α-NaiR.