Synthesis, crystal structure, photoisomerization, and DFT studies of novel azo compounds based on imidazole

New azo imidazole compounds 1-3 were synthesized by condensation of 2-hydroxy-3-methoxy-5-([aryl]diazenyl)benzaldehyde derivatives with o-vanillin and characterized. The crystal structure of 1 crystallizes in the monoclinic system with space group P21/c and adopts an E configuration for the azo and azomethine double bonds. The photoisomerization experiments have been performed in DMSO as a function of time in order to investigate the photodynamical trans-cis-trans conversion of the azo (-N=N-) chromophore of the imidazoles 1-3. The compounds exhibited strong photoisomerization in solution and their trans to cis isomerization took about 40 min whereas the reverse process took 120 min. The experimental studies are rationalized with theoretical DFT and TD-DFT studies successfully.