Ultrafast dynamics of dithienylethenes differently linked to the surface of TiO2 nanoparticles

Abstract

The photoinduced dynamics of a dithienylethene chromophore coupled to the surface of TiO2 by either a tripodal linker or a carboxyl group was investigated with ultrafast transient absorption spectroscopy. The absence of electron transfer from the photoexcited tripodal dithienylethene chromophore demonstrates that the tripod efficiently uncouples the electronic systems of dithienylethene and TiO2. Contrary to this situation, photoinduced electron transfer can compete with ultrafast intramolecular relaxation in the COOH–dithienylethene/TiO2 coupled system. An electron transfer rate of 1.1 × 1012 s−1 can be extracted, which is considerably slower than the intramolecular relaxation rate of the dithienylethene (3.7 × 1012 s−1). Consequently, the electron transfer reaction exhibits a low efficiency.