Photochemistry of Hypervalent Iodo-azide Derivatives

The photochemical properties and reaction mechanisms were studied for a series of hypervalent iodo-azide compounds (R-IN₃), with substituents (-CH₃, -H, -CF₃) modulating electronic density in the phenyl ring. With the help of UV irradiation, ultrafast time-resolved spectroscopy, and density functional theory (DFT) calculations, we elucidate the mechanisms of azide radical (N₃•) release and its subsequent reactivity. UV/Vis spectroscopy reveals that the photo-conversion rates follow the trend CH₃ > H > CF₃, aligning with DFT-calculated ΔG values for ring-opening transitions. Homolytic cleavage of the I-N bond is identified as the dominant pathway for N₃• generation, occurring within 400 ps. The released azide radical reacts with the solvent, and the iodo radical RIC• undergoes an uphill ring opening reaction controlling the rate of the reaction and subsequent downhill hydrogen atom abstraction from the solvent, helping to form R-I-COOH, as validated by NMR and IR spectroscopy. The study also highlights the role of substituents in influencing reaction kinetics and intermediate stability, with electron-donating groups accelerating N₃• release. This work bridges experimental observations with computational predictions, offering a foundation for future advancements in azide-based reactions and materials.