A structural and optical study of curcumin and curcumin analogs

Curcumin dye was extracted from turmeric and purified. Also, some curcumin analogous which have similar structures with different functional groups, and pi electrons length extension were synthesized. The chemical structure of these molecules was investigated and characterized by UV-Vis, H-1 NMR, and IR spectroscopies. The obtained UV-Vis spectra indicated that the strong electron-donating groups on aryl rings of these molecules enhance the intensity of lambda(max) and shift it toward the lower absorption energy. The conformation and structure of these molecules were investigated in solution and on the TiO2 anatase surfaces. Accordingly, three conformations could be existed in the solution including Cis-Enol, Keto, and twisted (in nanoparticles). Also, these molecules anchor on the TiO2 surface in a monodentate and bidentate chelating mode, depending on the TiO2 surface sites. Furthermore, the application of these molecules as dye in the dye-sensitized solar cell was studied. The observed data indicated that the best efficiency belongs to the 1,7-bis(4-dimethylaminophenyl)-1,6-heptadiene-3,5-dione dye (A3) which has strong electron-donating group (dimethylamine) on the para phenyl ring of the compound. Also, the appropriate IPCE of the A3 dye in the 460 nm (90%electron injection efficiency), demonstrate that the beta-dicarbonyl group is suitable anchoring group for DSSC application.

Automated summary

In this study, curcumin dye was extracted and purified from turmeric, and curcumin analogues with similar structures but different functional groups and extended pi electrons were synthesized. The chemical structures of these molecules were investigated and characterized using UV-Vis, H-1 NMR, and IR spectroscopies. The results showed that the electron-donating groups on the aryl rings of these molecules enhanced the absorption intensity and shifted lambda(max) towards lower energies. The conformation and structure of these molecules were found to vary in solution and on TiO2 anatase surfaces, and they could anchor on the TiO2 surface in different modes depending on the surface sites. The application of these molecules as dyes in dye-sensitized solar cells was also studied, and the best efficiency was observed for the dye A3, which had a strong electron-donating group on the para phenyl ring. The appropriate IPCE of the A3 dye at 460 nm demonstrated that the beta-dicarbonyl group is a suitable anchoring group for DSSC application.