Substituted Polyacenes as Prospective Modifiers of TiO2 Surface

Acenes, especially rubrene and pentacene are bricks-and-mortar of modern organic electronics, while smaller members of the family (anthracene derivatives) are common components of luminescent sensors and molecular logic gates. Recent development in semiconductor-based molecular scale devices has turned our attention towards acenes as modifiers of semiconducting surfaces. This review presents some recent achievements in the field of surface-modified titanium dioxide and provides basic tools and data towards understanding acene-titanium dioxide system at molecular level. A review of experimental data is supplemented with some DFT calculations of geometries, electronic structures and spectral properties of acene derivatives equipped with anchoring groups suitable for TiO2 modification. Surprisingly, higher acenes cannot support optical electron transfer with TiO2 surfaces on excitation of the lowest electronic transitions, as it was observed in the case of catechol and naphthalenediol. These systems, however can be still involved in photoinduced electron transfer, which altogether makes them useful surface dopants of wide band gap semiconductors.