Photolysis of a High-Spin Azidoiron(III) Complex Studied by Time-Resolved Fourier-Transform Infrared Spectroscopy

The laser-flash photolysis of the high-spin azidoiron(III) complex [Fe^III (Me₃ Cyclam-ac)(N₃ )]PF₆ ([1]PF₆ ) in liquid acetonitrile solution at room temperature was explored by time-resolved Fourier-transform infrared spectroscopy. Excitation of [1] at 480 and 266 nm induced a photoreduction of the metal center and generated [Fe^II (Me₃ Cyclam-ac)(NCCH₃ )]⁺ ([2]) and azidyl radicals. Both photoproducts were detected independently through scavenging experiments. The metal-containing fragment was quenched with carbon monoxide to generate an iron(II) carbonyl complex, whereas the nitrogen-containing fragment was quenched with iodide to form azide anions. In the presence of N₃^- , the photoreduction created the elusive hexanitrogen radical anion N₆^.- as a transient byproduct.