Substrate‐Selective Temperature‐Controlled Synthesis of Thiophene Derivatives at Interfaces

Abstract The temperature‐controlled transformation of organic molecules at interfaces is an incipient yet powerful strategy for tailoring their structural and physico‐chemical properties. In this study, we investigate the substrate‐ and thermal‐selective reactions of bis(3,4‐thiophene‐fused)tetrabromo‐ p ‐benzoquinodimethane molecule ( 1 ), focusing on its behavior at distinct coinage metal interfaces, namely Au(111) and Ag(111). Combining scanning probe microscopy and theory, we demonstrate that its sequential transformations are highly dependent on the substrate material and the specific reaction temperatures. When a benzodithiophene precursor, endowed with = CBr 2 units, is deposited under ultra‐high vacuum (UHV) conditions on both substrates held at room temperature (RT), or annealed to 100 °C in the case of Au(111), a self‐assembly is formed comprising 1D covalent polymers achieved through debromination and homocoupling, which are aligned in a parallel fashion thanks to supramolecular interactions, giving rise to a 2D supramolecular polymer. However, when the substrate is held at or above 175 °C during deposition, the molecular precursors ( 1 ) undergo substrate‐specific intramolecular reactions. On Au(111), a major transformation into pentalenodithiophene species is observed, concomitant with the formation of benzotrithiophene. On Ag(111), instead, pentalenodithiophene species are precluded. These findings highlight the importance of substrate selection and temperature control in enabling precise molecular transformations at the nanoscale.