Z to E light-activated isomerization of α-pyridyl-N-arylnitrone ligands sensitized by rhenium(I) polypyridyl complexes

[Display omitted] •Rhenium polypyridyl compounds were prepared with α-pyridyl-N-arylnitrone ligands.•Z-E isomerization of the coordinated nitrones was done by 3ILZ-Nit photosensitization.•The 3MLCT lowest-lying excited state of the E-isomer formed enhances the emission. A series of rhenium(I) polypyridyl compounds, bearing photoisomerizable nitrones as ligands, was synthesized and characterized by several techniques. The photochemical and photophysical behaviors of the compounds were investigated. Upon irradiation, acetonitrile solutions of the nitrones, or their respective complexes, exhibit changes in absorption, emission, and FTIR spectra. FTIR revealed the formation of the respective anilide as the photoproducts of irradiation of the uncoordinated nitrones, while irradiation of the complexes resulted in Z → E due to the photosensitized isomerization of the coordinated ligand, also confirmed by HPLC-MS and 1H NMR. The photoisomerization quantum yields are dependent on the nature of the nitrone substituent, which changes the energy of the 3ILZ-NitX excited state, which is populated by photosensitization. 3MLCT becomes the lowest-lying excited state in the E-product and results in an increase in emission intensity. The changes in spectroscopic properties of the Z or E coordinated nitrones can be exploited for molecular devices such as photosensors.