An intermolecular hydrogen bond plays a determining role in product selection of a surface confined Schiff-base reaction

Herein, we illustrate how the cooperation of intermolecular hydrogen bonds and conformation flexibility leads to the formation of diverse complex covalent nanostructures on the surface, while the relative abundance of the final products can be further tuned by adjusting the molar ratio and concentration of monomers.

Two-dimensional co-crystallization of two carboxylic acid derivatives having dissimilar symmetries at the liquid/solid interface

By the co-assembly of two carboxylic acids with distinct symmetries and different numbers of carboxyl groups, we obtained two novel cocrystal structures at the n-octanoic acid/HOPG interface, one of which was sustained by unoptimized R22(8) hydrogen bonding. Benefiting from the bias-sensitivity of the BTB (1,3,5-tris(4-carboxyphenyl)benzene) molecule, a structure transition between the cocrystal network and a denser BTB lamella is achieved.

Surface-Confined Macrocyclization via Dynamic Covalent Chemistry

Surface-confined synthesis is a promising approach to build complex molecular nanostructures including macrocycles. However, despite the recent advances in on-surface macrocyclization under ultrahigh vacuum, selective synthesis of monodisperse and multicomponent macrocycles remains a challenge. Here, we report on an on-surface formation of [6 + 6] Schiff-base macrocycles via dynamic covalent chemistry. The macrocycles form two-dimensional crystalline domains on the micrometer scale, enabled by dynamic conversion of open-chain oligomers into well-defined ∼3.0 nm hexagonal macrocycles. We further show that by tailoring the length of the alkyl substituents, it is possible to control which of three possible products-oligomers, macrocycles, or polymers-will form at the surface. In situ scanning tunneling microscopy imaging combined with density functional theory calculations and molecular dynamics simulations unravel the synergistic effect of surface confinement and solvent in leading to preferential on-surface macrocyclization.