Substituent Effect of Chiraldiphenyl Salen Metal (M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II)) Complexes for New Conceptual DSSC Dyes

The authors have designed and synthesized new chiral salen-type metal (M = Fe, Co, Ni, Cu, Zn) complexes (1-5) for new conceptual dyes (co-sensitizer or colorful multi-dyes) of DSSCs (dye-sensitized solar cells).The authors measured substituent effects on their absorption spectra and redox properties, and compared them with TD-DFT (time-dependent density functional theory) calculations.Electron withdrawing groups resulted in red-shift of ultraviolet-visible (UV-Vis) spectra.For the first time, the authors also proposed and confirmed the importance of substituent effects on their electric transition dipole moments, calculated by TD-DFT for designing dyes.Chemisorption for TiO 2 of the complex by carboxyl groups was confirmed by XPS measurement.In view of electronic properties, all compounds have the possibility to be dyes of DSSCs.