Two-dimensional self-assemblies of telechelic organic compounds: structure and surface host–guest chemistry

Abstract

Guiding the self-assembly of different types of functional molecules into well-defined structures on surfaces is beneficial for both fundamental surface and interface study and emerging application fields, especially molecular and organic electronics. This review focuses on understanding the two-dimensional self-assembly process of telechelic organics, which feature alkoxylene chains terminated with carboxyl groups. With the combined flexibility of alkyl chains and directionality of carboxyl groups, telechelic organics show unique assembly behaviour on two-dimensional surfaces. By increasing the length of the alkoxylene chains, the cavities in the nanoporous networks of telechelic trimesic acid (1,3,5-benzene tricarboxylic acid) derivatives change from hexagonal cavities to irregular cavities on a highly oriented pyrolytic graphite surface. The nanoporous networks provide a flexible host template for host–guest supramolecular chemistry because the cavities framed by the flexible alkoxylene chains can be changed in accordance with the sizes/shapes of the guest molecules. Furthermore, the terminal carboxylic group can form a hydrogen bond with another hydrogen bond partner, leading to multi-component structural motifs and hierarchical assemblies. The unique assembly behaviour of telechelic organics makes them promising structures as important building blocks for the design and construction of complex self-assembled nanoarchitectures.

Conformation Diversity of a Fused‐Ring Pyrazine Derivative on Au(111) and Highly Ordered Pyrolytic Graphite

“…It can be seen from Table that the van der Waals energy between molecules and substrates dominates the adsorption binding energy of DP′ molecules on substrates. It has been reported that stronger interactions between the molecule and substrate may decrease the mobility of molecules on the substrate and induce epitaxial structures on the substrate . The epitaxial structures of the DP molecules on Au(111) and HOPG disclosed by the STM images above illustrates clearly the strong interaction between the DP molecules and the substrate.…”

“…It is well known that two‐dimensional crystal structures are a balance of intermolecular interactions and molecule–substrate interactions . According to the obtained STM images, the densely packed lamellar structures formed by interdigitated alkyl chains of DP molecules on surfaces indicates that the chain–chain van der Waals interactions between long alkyl chains of DP molecules should contribute to the formation of the DP ordered adlayer on substrates . Hence, it is necessary to clarify the main driving force for the formation of DP adlayers on the Au(111) and HOPG surfaces.…”

“…found that a rectangular metal‐complexed macrocycle adsorbs with either a flat‐lying or an upright orientation on HOPG and Au(111) substrates, respectively . A series of trimesic acid derivatives are reported to form nanoporous structures and close‐packed structures without any cavities on HOPG and Au(111) surfaces, respectively . Kudernac et al.…”

Living on the edge: Tuning supramolecular interactions to design two-dimensional organic crystals near the boundary of two stable structural phases

“…18 For example, alkyl chains play an important role in self-assembly at the solution-solid interface in assisting adsorption and by directing assembly. [19][20][21][22] The role of dipolar functional groups positioned at the periphery of a molecule, [23][24][25][26][27][28] the anti-parallel alignment of zwitterions on surfaces, [29][30][31] and the impact of molecular dipoles 32,33 in supramolecular self-assembly at surfaces have been studied. While these types of contacts have been extensively examined in surface-adsorbed crystals, [34][35][36] the challenge now lies in balancing the weights of their relative contributions to generate bi-phasic systems.…”

Molecular nanostructure and nanotechnology

“…The outcome of the molecular selfassembly process depends upon a variety of factors including: the nature of the functional groups present on the assembling molecules, the temperature at which the molecules assemble, the environment in which the process occurs (e.g. ultra-high vacuum or solution) and the concentration of the building blocks (Mali & De Feyter [1], Yan et al [2]). Therefore, each of these parameters can have a significant influence on the nature of the nanomaterial produced and be critical for the extent of its practical utility owing to, for example, its magnetic (Wang et al [3]) or optical (Liu et al [4]) properties.…”