Structural comparison of self-organized adlayers of ligands and their metal-coordinated complexes on a Au(III) surface: An STM study

Scanning tunneling microscopy (STM) was employed to investigate the adsorption of the linear-spacer-bridged ligands bis(pyrrol-2-yl-methyl-eneamine) (BPMB and BPMmB), and their Zn-II-coordinated complexes, BPMB/Zn-II and BPMmB/Zn-II, onto a Au(III) surface in 0.1 m HClO4 solution. Both the ligands, with different spacer bridges, and their Zn-II complexes adsorb onto the Au(III) surface and self-organize into highly ordered two-dimensional arrays. The complexes BPMB/Zn-II and BPMmB/Zn-II appear in helical and triangular conformations, respectively, consistent with their chemical structures. Although the metal complexes include ligands, the assembled structures and adlayer symmetries of the ligands and complexes are totally different. The structures and intramolecular features obtained by high-resolution STM imaging are discussed. The results should be important in fabricating surface supramolecular structures.