On-Surface Synthesis of Self-Assembled Covalently Linked Wavy Chains with Site-Selective Conformational Switching

Abstract

Conformational arrangements in polymers on surfaces determine the overall shape as well as the potential properties. It is generally believed that conformational diversity leads to uncontrollable or disordered structures in on-surface synthesis. However, in this study, we obtain two well-ordered self-assembled covalently linked wavy chains with site-selective conformational switching via the Ullmann reaction of 1,2-bis(3-bromophenyl)ethane with multiple conformations on Ag(111). Two kinds of wavy chains exhibit distinct conformational arrangements, where chain I contains one repeating unit conformation of -cis-trans1-cis-trans1-cis-cis-trans1-, while the adjacent parallel parts in wavy chain II have two different conformational arrangements of -cis-cis-trans1- and -cis-cis-trans2-. Wavy chains coassemble with dissociated bromine atoms, suggesting that the Br···H–C interactions between Br atoms and molecular chains are crucial for the construction of ordered wavy chains. High-resolution scanning tunneling microscopy is employed to reveal the surface reaction process at the molecular scale. In depth growth mechanism analysis combined with density functional theory calculations unveils that the substrate also plays an important role in the fabrication of well-ordered wavy chains. The present work extends the surface reaction of conformational flexible precursors.

On‐Surface Isomerization of Indigo within 1D Coordination Polymers

“…[33] This is in line with reports of brominated organic molecule monomers that undergo CÀ Br bond scission on Ag(111). [34] The activated C atom may engage in CÀ C homocoupling, [34a] CÀ Ag [34b] bonds with the native adatoms of the surface or be passivated by H atoms. [34c] On neither Ag(111) nor Ag(100), there is evidence of reactive C atoms resulting from the CÀ Br bond cleavage in the STM images (as e.g.…”

Materials Nanoarchitectonics: Collaboration between Chem, Nano and Mat

“…Zhang and co‐workers synthesized the polymer by the Ullmann reaction of 1,2‐bis(3‐bromophenyl)ethane with multiple conformations on Ag(111) (Figure 6). [37] In this system, the sample was gradually annealed on Ag(111) at 483 K for 30 min. High‐resolution STM was used to reveal the surface reaction process on a molecular scale.…”

“… Synthesis of the polymer by the Ullmann reaction of 1,2‐bis(3‐bromophenyl)ethane with multiple conformations on Ag(111) where two types of self‐assembled covalent wavy chains with site‐selective conformational switching were nanoarchitectonized. Reproduced with permission [37] . 2023, American Chemical Society.…”

Steering the Surface-Confined Self-Assembly of Multifunctional Star-Shaped Molecules

“…The two-dimensional (2D) packing of flat objects is a fascinating area of study that spans across multiple disciplines, including mathematics, optical art, and supramolecular chemistry. − In the on-surface chemistry, this topic is particularly intriguing, as it allows for the controlled synthesis of sophisticated low-dimensional patterns comprising simple functional molecular building blocks. Using the bottom-up strategy, the nanopatterned solid surfaces can be rationally fabricated, allowing for the spontaneous formation of open porous networks, − planar tessellations, , fractal crystals, , nanoribbons, chains, rings, macrocycles, and others, which are inaccessible by other synthetic means. The key to achieving such precise control over the synthesis of these patterns lies in the exploitation of non-covalent molecular interactions, such as R 2 2 (8) cyclic H-bonding and twofold coordination bonds (ligand → metal), , due to their high directionality, strength, and reversibility.…”

“…These alveolate sectors, known as pores or cavities, can be fine-tuned to serve as well-defined matrices for the positioning and spatial organization of guest atoms/molecules. They can also act as 2D sieves, allowing size/shape segregation of mixed chemical entities, or as nanometer-sized reactors. − Additionally, due to the confinement of the molecules in a plane and their vertical interaction with the substrate, the flat-lying admolecules lose conformational freedom and may exist in the form of one, two, , or few surface conformers. , This fact is of great importance as the final outcome of the surface-supported SA is usually much more predictable and controllable than the analogous processes occurring in the bulk. Furthermore, the supramolecular architectures comprising laterally interconnected admolecules can be visually inspected by means of high-resolution scanning tunneling microscopy (STM) and other advanced non-destructive techniques, which strongly facilitates their structural analysis .…”