Self-recognition and self-selection in multicomponent supramolecular coordination networks on surfaces

Abstract

Self-recognition, self-selection, and dynamic self-organization are of fundamental importance for the assembly of all supramolecular systems, but molecular-level information is not generally accessible. We present direct examples of these critical steps by using scanning tunneling microscopy to study mixtures of complementary organic ligands on a copper substrate. The ligands coordinate cooperatively with iron atoms to form well ordered arrays of rectangular multicomponent compartments whose size and shape can be deliberately tuned by selecting ligands of desired length from complementary ligand families. We demonstrate explicitly that highly ordered supramolecular arrays can be produced from redundant ligand mixtures by molecular self-recognition and -selection, enabled by efficient error correction and cooperativity, and show an example of failed self-selection due to error tolerance in the ligand mixture, leading to a disordered structure.nanostructure ͉ scanning tunneling microscopy ͉ self-assembly ͉ surface chemistry ͉ organic molecule ligands S upramolecular self-organization, directed by information stored in molecular components and read out through their specific interactions, represents the pivotal operation in the spontaneous but controlled build-up of structurally organized and functionally integrated molecular systems (1). Metal-ligand coordination bonding is an effective strategy for strong, directional bonding to stabilize designed, self-assembled supramolecular architectures (2-5). Substrate-supported, 2D supramolecular coordination for efficient nanometer-scale patterning of solid surfaces has been demonstrated (6, 7). By selecting organic ligands with appropriate size, geometry, and binding moieties, specific tailored architectures can be produced across a substrate completely by self-assembly of the molecules. Such patterning of surfaces is of great interest for potential applications in surface nanofunctionalization, templated growth, and controlling 2D molecular nanoarrays. Molecular level insight has provided structural details of these systems, and here we explore multicomponent systems at that level to illustrate critical assembly requirements for these systems and (bio-)molecular systems in general.Self-selection occurs when the involved molecular components are sufficiently instructed to allow self-recognition and -assembly into discrete supramolecular architectures (8). Processes of modular self-assembly, dynamic self-organization, and self-selection are of fundamental importance for the assembly of all supramolecular systems, but molecular-level information is not generally accessible. Using scanning tunneling microscopy (STM), we address these issues by studying mixtures of complementary organic molecule ligands on a copper substrate that coordinate cooperatively with iron atoms to form regular arrays of rectangular multicomponent compartments. Ensembles of these complementary components serve as model systems to investigate the dynamic bottom-up self-organization process of modular ...

Substrate effect on supramolecular self-assembly: from semiconductors to metals

“…[16][17][18][19][20][21][22][23] These frameworks are characterized by a high degree of perfection since their assembly is based on reversible interactions which allow self-selection, -recognition and -correction processes to occur. 22 It has been recently demonstrated that, similarly to their 3D counterparts, 2D MOFs are also stabilized by genuine charge-transfer coordination bonding and that the metallic centers are characterized by well-defined oxidation states. 23 Such systems might be interesting not only as ordered 2D patterns with possible applications in host-guest reactions, nano reactors, etc.…”

“…Furthermore, two-dimensional (2D) MOFs could be formed by co-adsorption of d-transition metal atoms such as Fe, Co and Cu. [16][17][18][19][20][21][22][23] Due to its double-ended functionality, when TPA is absorbed in an upright geometry, it can be used for the organic passivation of inorganic surfaces such as Cu(110) 24 and TiO 2 . 25 A perpendicular binding geometry has also been reported for the adsorption of a similar molecule, 2-(trifluoromethyl)-terephthalic acid (C 6 H 3 CF 3 (COOH) 2 ), from solution onto fluorine-terminated Si(111).…”

Bicomponent Supramolecular Architectures at the Vacuum–Solid Interface

“…327 This dramatic difference can be understood by comparing the different thermodynamic stabilities of the systems and-in particular-the stability induced by the presence of the pyrimidine chelate. While PBP forms a relatively stable coordination network on its own, the phenyl and biphenyl analogues (BPB and BPBP) show only metastable homoleptic coordination on Cu(100).…”

Function Follows Form: Exploring Two-Dimensional Supramolecular Assembly at Surfaces

“…This will allow greater insight into application of these methods for the development and optimization of functional systems. For example, Langner et al 17 studied multipleligand mixtures in controlled ratios that exhibit local self-selection and error correction in a complementary binary metalϪorganic coordination, demonstrating fundamental steps for molecular selforganization using very simple organic species.…”