Transformation of the coordination nanostructures of 4,4',4''-(1,3,5-triazine-2,4,6-triyl) tribenzoic acid molecules on HOPG triggered by the change in the concentration of metal ions.

The modulation effects of Cu 2+ /Fe 3+ ions on the hydrogen-bonded structure of 4,4',4''-(1,3,5-triazine-2,4,6-triyl) tribenzoic acid (TATB) on a HOPG surface have been investigated at the liquid-solid interface by scanning tunneling microscopy (STM). STM observations directly demonstrated that the self-assembled honeycomb network of TATB has been dramatically transformed after introducing CuCl 2 /FeCl 3 with different concentrations. The metal-organic coordination structures are formed due to the incorporation of the Cu 2+ /Fe 3+ ions. Interestingly, a Cu 2+ ion remains coordinated to two COOH groups and only the number of COOH groups involved in coordination doubles when the concentration of Cu 2+ ions doubled. A Fe 3+ ion changes from coordination to three COOH groups to two COOH groups after increasing the concentration of Fe 3+ ions in a mixed solution. Such results suggest that the self-assembled structures of TATB molecules formed by metal-ligand coordination bonds can be effectively adjusted by regulating the concentration of metal ions in a mixed solution, which has rarely been reported before. It explains that the regulatory effect of concentration leads to the diversity of molecular architectures dominated by coordination bonds.