In this example two pyrene butyric acids are bound within a hexameric nanocapsule composed of six C-hexylpyrogallol[4]arenes held together by hydrogen bonds. The side chains of the pyrene butyric acids are omitted.[1]Circular helicate [(Fe5L5)Cl]9+, where L stands for s tris-bpy ligand strand; the central gray atom is Cl, while the smaller gray spheres are Fe.[2]
In
bottom-up
approach in far fewer steps than a single molecule of similar dimensions.
The process by which a supramolecular assembly forms is called
can be synthesized from using potassium ion as the template cationIllustrations of a. metal-organic frameworks and b. supramolecular coordination complexes
ions) exist in solution bound to ligands, In many cases, the coordination sphere defines geometries conducive to reactions either between ligands or involving ligands and other external reagents.
A well known metal-ion-templating was described by
18-crown-6 strongly coordinates potassium ion thus can be prepared through the Williamson ether synthesis
using potassium ion as the template metal.
Metal ions are frequently used for assembly of large supramolecular structures. Metal organic frameworks (MOFs) are one example.[4] MOFs are infinite structures where metal serve as nodes to connect organic ligands together. SCCs are discrete systems where selected metals and ligands undergo self-assembly to form finite supramolecular complexes,[5] usually the size and structure of the complex formed can be determined by the angularity of chosen metal-ligand bonds.
Hydrogen bond assisted supramolecular assembly
Hydrogen bonds in (a) DNA duplex formation and (b) protein β-sheet structure(a) Representative hydrogen bond patterns in supramolecular assembly. (b) Hydrogen bond network in cyanuric acid-melamine crystals.
amides
are commonly used to assemble higher order structures upon hydrogen bonding.
Hydrogen bond play an essential role in the assembly of secondary and tertiary structures of large biomolecules.
β-sheet
are formed through hydrogen bonding between the amide hydrogen and the amide carbonyl oxygen (Figure "Hydrogen bonds in (b) protein β-sheet structure").
In supramolecular chemistry, hydrogen bonds have been broadly applied to
synthons in bottom-up approach to engineering molecular interactions in crystals. Representative hydrogen bond patterns for supramolecular assembly is shown in Figure "Representative hydrogen bond patterns in supramolecular assembly".[8] A 1: 1 mixture of cyanuric acid and melamine forms crystal with a highly dense hydrogen-bonding network. This supramolecular aggregates has been used as templates to engineering other crystal structures.[9]
Applications
Supramolecular assemblies have no specific applications but are the subject of many intriguing reactions. A supramolecular assembly of
peptide amphiphiles in the form of nanofibers has been shown to promote the growth of neurons.[10] An advantage to this supramolecular approach is that the nanofibers will degrade back into the individual peptide molecules that can be broken down by the body. By self-assembling of dendritic dipeptides, hollow cylinders can be produced. The cylindrical assemblies possess internal helical order and self-organize into columnar liquid crystalline lattices. When inserted into vesicular membranes, the porous cylindrical assemblies mediate transport of protons across the membrane.[11]Self-assembly of dendrons generates arrays of nanowires.[12] Electron donor-acceptor complexes comprise the core of the cylindrical supramolecular assemblies, which further self-organize into two-dimensional columnar liquid crystalline
lattices. Each cylindrical supramolecular assembly functions as an individual wire. High charge carrier mobilities for holes and electrons were obtained.
_DNA_duplex_formation_and_(b)_protein_%CE%B2-sheet_structure.png)
_Representative_hydrogen_bond_patterns_in_supramolecular_assembly._(b)_Hydrogen_bond_network_in_cyanuric_acid-melamine_crystals.png)
