Photoinduced Electron Transfer in Perylene‐TiO 2 Nanoassemblies

The photosensitization effect of three perylene dye derivatives on titanium dioxide nanoparticles (TiO 2 NPs) has been investigated. The dyes used, 1,7‐dibromoperylene‐3,4,9,10‐tetracarboxy dianhydride (1), 1,7‐dipyrrolidinylperylene‐3,4,9,10‐tetracarboxy dianhydride (2) and 1,7‐bis(4‐tert‐butylphenyloxy)perylene‐3,4,9,10‐tetracarboxy dianhydride (3) have in common bisanhydride groups that convert into TiO 2 binding groups upon hydrolysis. The different substituents on the bay position of the dyes enable tuning of their redox properties to yield significantly different driving forces for photoinduced electron transfer (P eT ). Recently developed TiO 2 NPs having a small average size and a narrow distribution (4 ± 1 nm) are used in this work to prepare the dye‐TiO 2 systems under study. Whereas successful sensitization was obtained with 1 and 2 as evidenced by steady‐state spectral shifts and transient absorption results, no evidence for the attachment of 3 to TiO 2 was observed. The comparison of the rates of P eT ( k PeT ) for 1‐ and 2‐TiO 2 systems studied in this work with those obtained for previously reported analogous systems, having TiO 2 NPs covered by a surfactant layer (Hernandez et al . [2012] J. Phys. Chem. B ., 117, 4568–4581), indicates that k PeT for the former systems is slower than that for the later. These results are interpreted in terms of the different energy values of the conduction band edge in each system.