Metal-to-Metal Charge Transfer in Ethynylferrocene Appended Titanocenes
Dye sensitized solar cells (DSSCs) have shown promise in transforming solar energy into stored chemical energy. However, before DSSCs can be used on a global scale, the charge transfer dyes containing rare and expensive transition metals need to be replaced with cheaper materials. Recently, our lab has studied a bimetallic complex with an ethynyl linkage between Ti(IV) and ferrocene (Fc), Cp2Ti(C2Fc)2. This complex exhibits an absorbance at 585 nm ascribed to an Fe(II) to Ti(IV) metal-to-metal charge-transfer (MMCT). In support of this assignment, UV-Vis absorption spectra show that the bands attributed to the MMCT depend on solvent polarity. Cyclic voltammetry suggests that 1.65eV is stored in the charge-separated state. Time resolved transient absorption spectroscopy is being used to characterize the lifetime of the charge-separated state. We have also prepared the complex with a butadiynyl linkage, Cp2Ti(C4Fc)2, and are comparing the excited state lifetime with the ethynyl complex.