[Spectroscopy of alpha-isoxazoleazoxyl-beta-diketone derivatives and their tautomers].

In this paper, the IR and UV-Vis spectroscopy of five novel alpha-isoxazoleazoxyl-beta-diketone derivatives with different structures have been studied, and their keto-enol and azo-hydrazone tautomeric phenomena have been discussed. It was found that all compounds, which are in the solid or in the solution, exist in the form of hydrazodiketo and azoenol isomers. The authors can also see that there are two absorption bands which are in the range 246-262 nm and 326-339 nm, respectively, for all compounds in the UV spectra, and the intensities of long wavelength absorption bands which are attributed to azoenol forms are stronger than short wavelength absorption bands which are attributed to hydrazodiketo forms. This shows that the quantities of azoenol forms in the compounds are more than hydrazodiketo forms, and it may be due to that the varieties of the azoenol isomers can easily form six-membered rings structure in the form of intramolecular hydrogen bonding, and make chemical structures more stable.