A Study on the Photoisomerization of (E)-Dehydrozingerone, Its (E)-(E)-C₂ Symmetric Dimer, and Their O-Methylated Derivatives

In this study, UV-induced (E)-to-(Z) geometrical isomerizations of the curcumin degradation product (E)-dehydrozingerone, along with curcumin-inspired (E)-O-methylated dehydrozingerone and their corresponding C₂-symmetric dimers, were investigated. All compounds produced corresponding (Z) isomers in varying yields upon UV irradiation in deuterated solvents. The efficiency of these photoisomerizations depended on the solvent and wavelength used. While (Z) dehydrozingerone and its corresponding (Z)-(Z) dimer proved to be highly unstable during purification, the O-methylated derivatives were successfully isolated, fully characterized by NMR spectroscopy, and further analyzed by UV-Vis spectroscopy and computational methods.