Functionalized Supramolecular Nanoporous Arrays for Surface Templating (original) (raw)
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Nature Materials, 2004
nature materials | VOL 3 | APRIL 2004 | www.nature.com/naturematerials 229 M etal-organic coordination networks (MOCNs) have attracted wide interest because they provide a novel route towards porous materials that may find applications in molecular recognition, catalysis, gas storage and separation 1,2 . The so-called rational design principle-synthesis of materials with predictable structures and properties-has been explored using appropriate organic molecular linkers connecting to metal nodes to control pore size and functionality of open coordination networks 3-9 . Here we demonstrate the fabrication of surface-supported MOCNs comprising tailored pore sizes and chemical functionality by the modular assembly of polytopic organic carboxylate linker molecules and iron atoms on a Cu(100) surface under ultra-high-vacuum conditions. These arrays provide versatile templates for the handling and organization of functional species at the nanoscale, as is demonstrated by their use to accommodate C 60 guest molecules. Temperature-controlled studies reveal, at the single-molecule level, how pore size and chemical functionality determine the host-guest interactions.
Control and induction of surface-confined homochiral porous molecular networks
Nature Chemistry, 2011
Homochirality is essential to many biological systems, and plays a pivotal role in various technological applications. The generation of homochirality and an understanding of its mechanism from the single-molecule to supramolecular level have received much attention. Two-dimensional chirality is a subject of intense interest due to the unique possibilities and consequences of confining molecular self-assembly to surfaces or interfaces. Here, we report the perfect generation of twodimensional homochirality of porous molecular networks at the liquid-solid interface in two different ways: (i) by selfassembly of homochiral building blocks and (ii) by self-assembly of achiral building blocks in the presence of a chiral modifier via a hierarchical structural recognition process, as revealed by scanning tunnelling microscopy. The present results provide important impetus for the development of two-dimensional crystal engineering and may afford opportunities for the utilization of chiral nanowells in chiral recognition processes, as nanoreactors and as data storage systems.
Guest-induced growth of a surface-based supramolecular bilayer
Nature Chemistry, 2010
Self-assembly of planar molecules on a surface can result in the formation of a wide variety of close-packed or porous structures. Two-dimensional porous arrays provide host sites for trapping guest species of suitable size. Here we show that a non-planar guest species (C 60) can play a more complex role by promoting the growth of a second layer of host molecules (p-terphenyl-3,5,3 ′′ ,5 ′′-tetracarboxylic acid) above and parallel to the surface so that self-assembly is extended into the third dimension. The addition of guest molecules and the formation of the second layer are co-dependent. Adding a planar guest (coronene) can displace the C 60 and cause reversion to a monolayer arrangement. The system provides an example of a reversible transformation between a planar and a non-planar supramolecular network, an important step towards the controlled self-assembly of functional, three-dimensional, surface-based supramolecular architectures.
The Journal of Physical Chemistry C, 2008
An oligopyridine forms a well-ordered two-dimensional network at the graphite-liquid interface stabilized by weak hydrogen bonds. This network offers two types of geometrically different voids of similar size, oval and circular in shape, respectively. Hierarchical coadsorption of C 60 fullerene onto the oligopyridine monolayer leads to a host-guest network in which the fullerene molecules adsorb exclusively in the circularly shaped voids. This is attributed to the fit of the spherical molecules to the round void according to a geometric lock-and-key principle.
Supramolecular anion recognition in water: synthesis of hydrogen-bonded supramolecular frameworks
Chemical science, 2017
The interaction of tetratopic amidinium-containing receptors with terephthalate anions leads to porous framework materials assembled through charge-assisted hydrogen bonds. The frameworks form in good yield within minutes in water at room temperature, but no framework material is obtained if other anions (Cl(-), Br(-), NO3(-), SO4(2-) or isophthalate(2-)) are used in place of terephthalate. Two forms of the framework can be prepared: one with a connected pore network, and a more dense phase with discrete voids. We demonstrate that these are the kinetic and thermodynamic products, respectively. Either framework can be prepared independently and can be converted to the other form in response to stimuli. Furthermore, the frameworks can be controllably disassembled and reassembled in response to acid/base triggers suggesting that this new class of materials may have applications in the selective encapsulation and release of guests.
Formation Mechanism for a Hybrid Supramolecular Network Involving Cooperative Interactions
Physical Review Letters, 2012
A novel mechanism of hybrid assembly of molecules on surfaces is proposed stemming from interactions between molecules and on-surface metal atoms which eventually got trapped inside the network pores. Based on state-of-the-art theoretical calculations, we find that the new mechanism relies on formation of molecule-metal atom pairs which, together with molecules themselves, participate in the assembly growth. Most remarkably, the dissociation of pairs is facilitated by a cooperative interaction involving many molecules. This new mechanism is illustrated on a low coverage Melamine hexagonal network on the Au(111) surface where multiple events of gold atoms trapping via a set of so-called ''gate'' transitions are found by kinetic Monte Carlo simulations based on transition rates obtained using ab initio density functional theory calculations and the nudged elastic band method. Simulated STM images of gold atoms trapped in the pores of the Melamine network predict that the atoms should appear as bright spots inside Melamine hexagons. No trapping was found at large Melamine coverages, however. These predictions have been supported by preliminary STM experiments which show bright spots inside Melamine hexagons at low Melamine coverages, while empty pores are mostly observed at large coverages. Therefore, we suggest that bright spots sometimes observed in the pores of molecular assemblies on metal surfaces may be attributed to trapped substrate metal atoms. We believe that this type of mechanism could be used for delivering adatom species of desired functionality (e.g., magnetic) into the pores of hydrogen-bonded networks serving as templates for their capture.