Synthesis and characterization of pentacene derivative by Wittig–Horner reagent and its composite with nano-sized TiO2

Wittig–Horner reagent was firstly used to prepare a pentacene derivative which was designated as 6-phenylidene-13,13-dihydropentacene (PHP). The newly prepared derivative was more soluble than pentacene due to the introduction of substituted group. UV–vis spectra showed that it displayed a wide absorption in the range of 470–650 nm in CHCl3, and with a maximum absorption at 555 nm. In cyclic voltammetry (CV) test, it was found that its forbidden band gap was as small as 1.34 eV. During the photo-oxidation test, the as-prepared pentacene was sensitive to ambient light but sluggish to air in solution. Moreover, a composite of PHP–TiO2 was also constructed. A series of characterizations proved that an interaction between PHP and TiO2 most probably had occurred, leading to generation of some novel properties which were different from both PHP and TiO2. The most interesting result is that the band gap of the composite material is smaller than that of PHP and TiO2, with the value of 1.18 eV.