Tailoring the Reaction Path in the On-Surface Chemistry of Thienoacenes

Abstract

Oligothiophenes provide rich opportunities for surface confined reactions that can lead to two-dimensional materials. We have performed systematic studies of tetrathieno-anthracene (TTA) based molecules on different transition metal surfaces to reveal the details of their on-surface chemistry. On the (111) surfaces of Ni, Pd, and Cu, we observe the sulfur abstraction from the monomer following thermal activation, whose yield varies with the type of metal surface. On Ni(111) and Pd(111) the internal design of the 2TTA isomer promotes intramolecular rebonding to produce pentacene, whereas geometrical constraints prevent the 3TTA isomer from intramolecular rebonding, promoting oligomerization. On Cu(111), desulfurization is preceded by dehydrogenation, which introduces metal-mediated intermolecular coupling in 2TTA. This organometallic phase is stable up to 200 °C. On all surfaces, the desulfurization and dehydrogenation of the molecules are important reaction pathways which define the bonding geometries of the products.