Lying or Standing of Thiophene on a Surface Determines the Reaction Difference.

Adsorption configurations of molecules on a surface play an important role in the on-surface reaction. In the on-surface synthesis reaction, most of the molecules prefer the lying adsorption configuration to maximize the interaction between the molecule and substrate. In this work, we report an on-surface study of 2,3,4,5-tetrabromothiophene by scanning tunneling microscopy, density functional theory, and X-ray photoelectron spectroscopy. Due to different interactions between thiophene and metal surfaces, lying or standing configurations of 2,3,4,5-tetrabromothiophene can be selected by the choice of metal substrates. Moreover, a catalytic role of the metal substrate in the molecular reaction with lying and standing adsorption configurations is demonstrated at the molecular level. This work broadens the understanding of thiophene's configurations in surface reactions and the product diversity driven by adsorption configurations. It also offers a guiding framework for synthesizing multifunctional materials by thiophene derivatives.