Structure Formation and Annealing of Isophthalic Acid at the Electrochemical Au(111)-Electrolyte Interface

Using in situ scanning tunneling microscopy (STM) and electrochemical and thermal annealing procedures, we achieve for the first time long-range ordered chemisorbed adlayers of isophthalic acid (IA) at electrified Au(111)/0.1 M HClO4 inter-faces. At room temperature, IA chemisorbs in a highly disordered manner at a positively charged surface due to the formation of strong bonds between one carboxylate group per molecule and the gold substrate. Upon electrochemical and thermal annealing, molecular rearrangement in the chemisorbed adlayer is promoted and a highly two-dimensional (2D) order is achieved. We present a comprehensive structural analysis of the chemisorbed and physisorbed adlayers of IA on Au(111), revealing the structure-determining role of substrate-adsorbate coordination and of intermolecular hydrogen bonds in forming distinct 2D adlayer motifs. The annealing strategies are expected to have general value in generating thermodynamically equilibrated molecular-scale architectures on electrified surfaces or at interfaces.