Supramolecular assembly

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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. Host Guest Complex Nanocapsule Science Year2005 Vol309 Page2037.jpg
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.
Circular helicate .mw-parser-output .template-chem2-su{display:inline-block;font-size:80%;line-height:1;vertical-align:-0.35em}.mw-parser-output .template-chem2-su>span{display:block;text-align:left}.mw-parser-output sub.template-chem2-sub{font-size:80%;vertical-align:-0.35em}.mw-parser-output sup.template-chem2-sup{font-size:80%;vertical-align:0.65em} [(Fe5L5)Cl], where L stands for s tris-bpy ligand strand; the central gray atom is Cl, while the smaller gray spheres are Fe. Supramolecular Assembly Lehn.jpg
Circular helicate [(Fe5L5)Cl], where L stands for s tris-bpy ligand strand; the central gray atom is Cl, while the smaller gray spheres are Fe.

In chemistry, a supramolecular assembly is a complex of molecules held together by noncovalent bonds. While a supramolecular assembly can be simply composed of two molecules (e.g., a DNA double helix or an inclusion compound), or a defined number of stoichiometrically interacting molecules within a quaternary complex, it is more often used to denote larger complexes composed of indefinite numbers of molecules that form sphere-, rod-, or sheet-like species. Colloids, liquid crystals, biomolecular condensates, micelles, liposomes and biological membranes are examples of supramolecular assemblies, [3] and their realm of study is known as supramolecular chemistry. The dimensions of supramolecular assemblies can range from nanometers to micrometers. Thus they allow access to nanoscale objects using a bottom-up approach in far fewer steps than a single molecule of similar dimensions.

Contents

The process by which a supramolecular assembly forms is called molecular self-assembly. Some try to distinguish self-assembly as the process by which individual molecules form the defined aggregate. Self-organization, then, is the process by which those aggregates create higher-order structures. This can become useful when talking about liquid crystals and block copolymers.

Templating reactions

18-crown-6 can be synthesized from using potassium ion as the template cation 18-crown-6 was synthesized using potassium ion as the template cation.png
18-crown-6 can be synthesized from using potassium ion as the template cation
Illustrations of a. metal-organic frameworks and b. supramolecular coordination complexes Illustrations of a. metal-organic frameworks and b. supramolecular coordination complexes.png
Illustrations of a. metal-organic frameworks and b. supramolecular coordination complexes

As studied in coordination chemistry, metal ions (usually transition metal 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 Charles Pedersen in his synthesis of various crown ethers using metal cations as template. For example, 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 b-sheet structure Hydrogen bonds in (a) DNA duplex formation and (b) protein b-sheet structure.png
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. (a) Representative hydrogen bond patterns in supramolecular assembly. (b) Hydrogen bond network in cyanuric acid-melamine crystals.png
(a) Representative hydrogen bond patterns in supramolecular assembly. (b) Hydrogen bond network in cyanuric acid-melamine crystals.

Hydrogen bond-assisted supramolecular assembly is the process of assembling small organic molecules to form large supramolecular structures by non-covalent hydrogen bonding interactions. The directionality, reversibility, and strong bonding nature of hydrogen bond make it an attractive and useful approach in supramolecular assembly. Functional groups such as carboxylic acids, ureas, amines, and 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. DNA double helix is formed by hydrogen bonding between nucleobases: adenine and thymine forms two hydrogen bonds, while guanine and cytosine forms three hydrogen bonds (Figure "Hydrogen bonds in (a) DNA duplex formation"). Another prominent example of hydrogen bond-assisted assembly in nature is the formation of protein secondary structures. Both the α-helix and 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 crystal engineering, molecular recognition, and catalysis. [6] [7] Hydrogen bonds are among the mostly used 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.

See also

Related Research Articles

<span class="mw-page-title-main">Hydrogen bond</span> Intermolecular attraction between a hydrogen-donor pair and an acceptor

In chemistry, a hydrogen bond is primarily an electrostatic force of attraction between a hydrogen (H) atom which is covalently bonded to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac). Such an interacting system is generally denoted Dn−H···Ac, where the solid line denotes a polar covalent bond, and the dotted or dashed line indicates the hydrogen bond. The most frequent donor and acceptor atoms are the period 2 elements nitrogen (N), oxygen (O), and fluorine (F).

<span class="mw-page-title-main">Molecule</span> Electrically neutral group of two or more atoms

A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and molecule is often used when referring to polyatomic ions.

<span class="mw-page-title-main">Catenation</span> Bonding of atoms of the same element into chains or rings

In chemistry, catenation is the bonding of atoms of the same element into a series, called a chain. A chain or a ring shape may be open if its ends are not bonded to each other, or closed if they are bonded in a ring. The words to catenate and catenation reflect the Latin root catena, "chain".

Supramolecular chemistry refers to the branch of chemistry concerning chemical systems composed of a discrete number of molecules. The strength of the forces responsible for spatial organization of the system range from weak intermolecular forces, electrostatic charge, or hydrogen bonding to strong covalent bonding, provided that the electronic coupling strength remains small relative to the energy parameters of the component. While traditional chemistry concentrates on the covalent bond, supramolecular chemistry examines the weaker and reversible non-covalent interactions between molecules. These forces include hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi–pi interactions and electrostatic effects.

<span class="mw-page-title-main">Host–guest chemistry</span> Supramolecular structures held together other than by covalent bonds

In supramolecular chemistry, host–guest chemistry describes complexes that are composed of two or more molecules or ions that are held together in unique structural relationships by forces other than those of full covalent bonds. Host–guest chemistry encompasses the idea of molecular recognition and interactions through non-covalent bonding. Non-covalent bonding is critical in maintaining the 3D structure of large molecules, such as proteins and is involved in many biological processes in which large molecules bind specifically but transiently to one another.

In chemistry, a non-covalent interaction differs from a covalent bond in that it does not involve the sharing of electrons, but rather involves more dispersed variations of electromagnetic interactions between molecules or within a molecule. The chemical energy released in the formation of non-covalent interactions is typically on the order of 1–5 kcal/mol. Non-covalent interactions can be classified into different categories, such as electrostatic, π-effects, van der Waals forces, and hydrophobic effects.

<span class="mw-page-title-main">Tetrahedral molecular geometry</span> Central atom with four substituents located at the corners of a tetrahedron

In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron. The bond angles are cos−1(−1⁄3) = 109.4712206...° ≈ 109.5° when all four substituents are the same, as in methane as well as its heavier analogues. Methane and other perfectly symmetrical tetrahedral molecules belong to point group Td, but most tetrahedral molecules have lower symmetry. Tetrahedral molecules can be chiral.

In chemistry, mechanically interlocked molecular architectures (MIMAs) are molecules that are connected as a consequence of their topology. This connection of molecules is analogous to keys on a keychain loop. The keys are not directly connected to the keychain loop but they cannot be separated without breaking the loop. On the molecular level, the interlocked molecules cannot be separated without the breaking of the covalent bonds that comprise the conjoined molecules; this is referred to as a mechanical bond. Examples of mechanically interlocked molecular architectures include catenanes, rotaxanes, molecular knots, and molecular Borromean rings. Work in this area was recognized with the 2016 Nobel Prize in Chemistry to Bernard L. Feringa, Jean-Pierre Sauvage, and J. Fraser Stoddart.

<span class="mw-page-title-main">Coordination polymer</span> Polymer consisting of repeating units of a coordination complex

A coordination polymer is an inorganic or organometallic polymer structure containing metal cation centers linked by ligands. More formally a coordination polymer is a coordination compound with repeating coordination entities extending in 1, 2, or 3 dimensions.

<span class="mw-page-title-main">Cation–π interaction</span>

Cation–π interaction is a noncovalent molecular interaction between the face of an electron-rich π system (e.g. benzene, ethylene, acetylene) and an adjacent cation (e.g. Li+, Na+). This interaction is an example of noncovalent bonding between a monopole (cation) and a quadrupole (π system). Bonding energies are significant, with solution-phase values falling within the same order of magnitude as hydrogen bonds and salt bridges. Similar to these other non-covalent bonds, cation–π interactions play an important role in nature, particularly in protein structure, molecular recognition and enzyme catalysis. The effect has also been observed and put to use in synthetic systems.

<span class="mw-page-title-main">Crystal engineering</span> Designing solid structures with tailored properties

Crystal engineering studies the design and synthesis of solid-state structures with desired properties through deliberate control of intermolecular interactions. It is an interdisciplinary academic field, bridging solid-state and supramolecular chemistry.

In polymer chemistry and materials science, the term "polymer" refers to large molecules whose structure is composed of multiple repeating units. Supramolecular polymers are a new category of polymers that can potentially be used for material applications beyond the limits of conventional polymers. By definition, supramolecular polymers are polymeric arrays of monomeric units that are connected by reversible and highly directional secondary interactions–that is, non-covalent bonds. These non-covalent interactions include van der Waals interactions, hydrogen bonding, Coulomb or ionic interactions, π-π stacking, metal coordination, halogen bonding, chalcogen bonding, and host–guest interaction. The direction and strength of the interactions are precisely tuned so that the array of molecules behaves as a polymer in dilute and concentrated solution, as well as in the bulk.

<span class="mw-page-title-main">Molecular self-assembly</span> Movement of molecules into a defined arrangement without outside influence

In chemistry and materials science, molecular self-assembly is the process by which molecules adopt a defined arrangement without guidance or management from an outside source. There are two types of self-assembly: intermolecular and intramolecular. Commonly, the term molecular self-assembly refers to the former, while the latter is more commonly called folding.

In chemistry, a halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. Like a hydrogen bond, the result is not a formal chemical bond, but rather a strong electrostatic attraction. Mathematically, the interaction can be decomposed in two terms: one describing an electrostatic, orbital-mixing charge-transfer and another describing electron-cloud dispersion. Halogen bonds find application in supramolecular chemistry; drug design and biochemistry; crystal engineering and liquid crystals; and organic catalysis.

In chemistry, π-effects or π-interactions are a type of non-covalent interaction that involves π systems. Just like in an electrostatic interaction where a region of negative charge interacts with a positive charge, the electron-rich π system can interact with a metal, an anion, another molecule and even another π system. Non-covalent interactions involving π systems are pivotal to biological events such as protein-ligand recognition.

<span class="mw-page-title-main">Croconic acid</span> Chemical compound

Croconic acid is a chemical compound with formula C5H2O5 or (C=O)3(COH)2. It has a cyclopentene backbone with two hydroxyl groups adjacent to the double bond and three ketone groups on the remaining carbon atoms. It is sensitive to light, soluble in water and ethanol and forms yellow crystals that decompose at 212 °C.

Coordination cages are three-dimensional ordered structures in solution that act as hosts in host–guest chemistry. They are self-assembled in solution from organometallic precursors, and often rely solely on noncovalent interactions rather than covalent bonds. Coordinate bonds are useful in such supramolecular self-assembly because of their versatile geometries. However, there is controversy over calling coordinate bonds noncovalent, as they are typically strong bonds and have covalent character. The combination of a coordination cage and a guest is a type of inclusion compound. Coordination complexes can be used as "nano-laboratories" for synthesis, and to isolate interesting intermediates. The inclusion complexes of a guest inside a coordination cage show intriguing chemistry as well; often, the properties of the cage will change depending on the guest. Coordination complexes are molecular moieties, so they are distinct from clathrates and metal-organic frameworks.

<span class="mw-page-title-main">Two-dimensional polymer</span>

A two-dimensional polymer (2DP) is a sheet-like monomolecular macromolecule consisting of laterally connected repeat units with end groups along all edges. This recent definition of 2DP is based on Hermann Staudinger's polymer concept from the 1920s. According to this, covalent long chain molecules ("Makromoleküle") do exist and are composed of a sequence of linearly connected repeat units and end groups at both termini.

Cyclobis(paraquat-<i>p</i>-phenylene) Chemical compound

Cyclobis(paraquat-p-phenylene) belongs to the class of cyclophanes, and consists of aromatic units connected by methylene bridges. It is able to incorporate small guest molecule and has played an important role in host–guest chemistry and supramolecular chemistry.

Metallogels are one-dimensional nanostructured materials, which constitute a growing class in the Supramolecular chemistry field. Non-covalent interactions, such as hydrophobic interactions, π-π interactions, and hydrogen bonding, are among the responsible forces for the formation of those gels from small molecules. However, the main driving force for the formation of a metallogel is the metal-ligand coordination. Once the structure has been established, it resists gravitational force when inverted.

References

  1. ↑ Dalgarno, S. J.; Tucker, S. A.; Bassil, D. B.; Atwood, J. L. (2005). "Fluorescent Guest Molecules Report Ordered Inner Phase of Host Capsules in Solution". Science. 309 (5743): 2037–9. Bibcode:2005Sci...309.2037D. doi:10.1126/science.1116579. PMID   16179474. S2CID   41468421.
  2. ↑ Hasenknopf, Bernold; Lehn, Jean-Marie; Kneisel, Boris O.; Baum, Gerhard; Fenske, Dieter (1996). "Self-Assembly of a Circular Double Helicate". Angewandte Chemie International Edition in English. 35 (16): 1838. doi:10.1002/anie.199618381.
  3. ↑ Ariga, Katsuhiko; Hill, Jonathan P; Lee, Michael V; Vinu, Ajayan; Charvet, Richard; Acharya, Somobrata (2008). "Challenges and breakthroughs in recent research on self-assembly". Science and Technology of Advanced Materials. 9 (1): 014109. Bibcode:2008STAdM...9a4109A. doi:10.1088/1468-6996/9/1/014109. PMC   5099804 . PMID   27877935.
  4. ↑ Cook, T. R.; Zheng, Y.; Stang, P. J. (2013). "Metal-organic frameworks and self-assembled supramolecular coordination complexes: Comparing and contrasting the design, synthesis, and functionality of metal-organic materials". Chem. Rev. 113 (1): 734–77. doi:10.1021/cr3002824. PMC   3764682 . PMID   23121121.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ↑ Paul, R. L.; Bell, Z. R.; Jeffery, J. C.; McCleverty, J. A.; Ward, M. D. (2002). "Anion-templated self-assembly of tetrahedral cage complexes of cobalt(II) with bridging ligands containing two bidentate pyrazolyl-pyridine binding sites". Proc. Natl. Acad. Sci. 99 (8): 4883–8. Bibcode:2002PNAS...99.4883P. doi: 10.1073/pnas.052575199 . PMC   122688 . PMID   11929962.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ↑ Lehn, J. M. (1985). "Supramolecular chemistry: Receptors, catalysts, and carriers". Science. 227 (4689): 849–56. Bibcode:1985Sci...227..849L. doi:10.1126/science.227.4689.849. PMID   17821215. S2CID   44733755.
  7. ↑ Meeuwissen, J.; Reek, J. N. H. (2010). "Supramolecular catalysis beyond enzyme mimics". Nat. Chem. 2 (8): 615–21. Bibcode:2010NatCh...2..615M. doi:10.1038/nchem.744. PMID   20651721.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ↑ Desiraju, G. R. (2013). "Crystal engineering: From molecule to crystal". J. Am. Chem. Soc. 135 (27): 9952–67. doi:10.1021/ja403264c. PMID   23750552.
  9. ↑ Seto, C. T.; Whitesides, G. M. (1993). "Molecular self-assembly through hydrogen bonding: Supramolecular aggregates based on the cyanuric acid-melamine lattice". J. Am. Chem. Soc. 115 (3): 905–916. doi:10.1021/ja00056a014.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ↑ Silva, G. A.; Czeisler, C; Niece, K. L.; Beniash, E; Harrington, D. A.; Kessler, J. A.; Stupp, S. I. (2004). "Selective Differentiation of Neural Progenitor Cells by High-Epitope Density Nanofibers" (PDF). Science. 303 (5662): 1352–5. Bibcode:2004Sci...303.1352S. doi:10.1126/science.1093783. PMID   14739465. S2CID   6713941.
  11. ↑ Percec, Virgil; Dulcey, Andrés E.; Balagurusamy, Venkatachalapathy S. K.; Miura, Yoshiko; Smidrkal, Jan; Peterca, Mihai; Nummelin, Sami; Edlund, Ulrica; Hudson, Steven D.; Heiney, Paul A.; Duan, Hu; Magonov, Sergei N.; Vinogradov, Sergei A. (2004). "Self-assembly of amphiphilic dendritic dipeptides into helical pores". Nature. 430 (7001): 764–8. Bibcode:2004Natur.430..764P. doi:10.1038/nature02770. PMID   15306805. S2CID   4405030.
  12. ↑ Percec, V.; Glodde, M.; Bera, T. K.; Miura, Y.; Shiyanovskaya, I.; Singer, K. D.; Balagurusamy, V. S. K.; Heiney, P. A.; Schnell, I.; Rapp, A.; Spiess, H.-W.; Hudson, S. D.; Duan, H. (2002). "Self-organization of supramolecular helical dendrimers into complex electronic materials". Nature. 417 (6905): 384–7. Bibcode:2002Natur.417..384P. doi:10.1038/nature01072. PMID   12352988. S2CID   1708646.
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