Surface Confined Synthesis of Hydroxy Functionalized Two-Dimensional Polymer: The Effect of the Position of Hydroxy Groups

We report on the on-surface synthesis of a series of two-dimensional polymers (2DPs) and macrocycles containing hydroxyl groups on a highly oriented pyrolytic graphite surface. The formed 2DPs and macrocycles were visualized through scanning tunneling microscopy. By varying the solvent and reaction temperature, structural evolution from oligomers to well-ordered 2DPs or discrete macrocycles was directly followed. In addition, we discovered that the reaction outcome can be steered from extended 2DPs to discrete macrocycles or catenular structures by exchanging the position of the hydroxyl and aldehyde group. These results indicate that the relative positions of hydroxyl and aldehyde groups on the biphenyl ring play a determining role in the control and selection of the final products of the surface-confined Schiff base coupling reaction.