Supramolecular chemistry is a field of science that goes beyond particles that focuses on scientific systems made up of a discrete number of assembled subunits or components. The forces responsible for spatial organization can range from weak (electrostatic or hydrogen bonds) to strong (covalent bonds) provided that the degree of electronic relationship between the molecular components remains small in relation to the corresponding energy parameters of the substance.
Important concepts
While conventional chemistry focuses on the covalent bond, supramolecular chemistry explores the weaker and reversible non-covalent interactions between molecules. These forces include hydrogen bonding, metal coordination, hydrophobic van der Waals sets, and electrostatic effects.
Important concepts that were demonstrated using thisdisciplines include partial self-assembly, folding, recognition, host-guest, mechanically coupled architecture, and dynamic covalent science. The study of non-covalent types of interactions in supramolecular chemistry is critical to understanding the many biological processes from cellular structure to vision that rely on these forces. Biological systems are often a source of inspiration for research. Supermolecules are to molecules and intermolecular bonds, as particles are to atoms, and covalent tangency.
History
The existence of intermolecular forces was first postulated by Johannes Diederik van der Waals in 1873. However, the Nobel laureate Hermann Emil Fischer developed the philosophical roots of supramolecular chemistry. In 1894, Fisher proposed that the enzyme-substrate interaction takes the form of "lock and key", the fundamental principles of molecular recognition and host-guest chemistry. In the early 20th century, non-covalent bonds were studied in more detail, with the hydrogen bond being described by Latimer and Rodebush in 1920.
The use of these principles has led to a deeper understanding of protein structure and other biological processes. For example, an important breakthrough that enabled the elucidation of the double helix structure from DNA occurred when it became clear that there were two separate strands of nucleotides connected via hydrogen bonds. The use of non-covalent relationships is essential for replication because they allow strands to be separated and used as a template for a new one.double stranded DNA. Simultaneously, chemists began to recognize and study synthetic structures based on non-covalent interactions such as micelles and microemulsions.
Eventually, chemists were able to take these concepts and apply them to synthetic systems. A breakthrough occurred in the 1960s - the synthesis of crowns (ethers according to Charles Pedersen). Following this work, other researchers such as Donald J. Crum, Jean-Marie Lehn, and Fritz Vogtl became active in the synthesis of form-ion-selective receptors, and during the 1980s, research in this area gained momentum. Scientists worked with concepts such as the mechanical interlocking of molecular architecture.
In the 90s, supramolecular chemistry became even more problematic. Researchers such as James Fraser Stoddart developed molecular mechanisms and highly complex self-organizing structures, while Itamar Wilner studied and created sensors and methods for electronic and biological interaction. During this period, photochemical motifs were integrated into supramolecular systems to increase functionality, research began on synthetic self-replicating communication, and work continued on devices for processing molecular information. The evolving science of nanotechnology has also had a strong impact on this topic, creating building blocks such as fullerenes (supramolecular chemistry), nanoparticles, and dendrimers. They participate in synthetic systems.
Control
Supramolecular chemistry deals with subtle interactions, and therefore control over the processes involvedmay require great precision. In particular, non-covalent bonds have low energies, and often there is not enough energy for activation, for formation. As the Arrhenius equation shows, this means that, unlike covalent bond forming chemistry, the rate of creation does not increase at higher temperatures. In fact, chemical equilibrium equations show that low energy leads to a shift towards the destruction of supramolecular complexes at higher temperatures.
However, low degrees can also create problems for such processes. Supramolecular chemistry (UDC 541–544) may require molecules to be distorted into thermodynamically unfavorable conformations (for example, during the "synthesis" of rotaxanes with slip). And it may include some covalent science that is consistent with the above. In addition, the dynamic nature of supramolecular chemistry is used in many mechanics. And only cooling will slow down these processes.
Thus, thermodynamics is an important tool for designing, controlling and studying supramolecular chemistry in living systems. Perhaps the most striking example is warm-blooded biological organisms, which completely stop working outside a very narrow temperature range.
Environmental sphere
The molecular environment around a supramolecular system is also of paramount importance for its operation and stability. Many solvents have strong hydrogen bonds, electrostaticproperties and the ability to transfer charge, and therefore they can enter into complex equilibria with the system, even completely destroying the complexes. For this reason, the choice of solvent can be critical.
Molecular self-assembly
This is building systems without guidance or control from an outside source (other than to provide the right environment). Molecules are directed to collection through non-covalent interactions. Self-assembly can be subdivided into intermolecular and intramolecular. This action also allows the construction of larger structures such as micelles, membranes, vesicles, liquid crystals. This is important for crystal engineering.
MP and complexation
Molecular recognition is the specific binding of a guest particle to a complementary host. Often the definition of which species is it and which is the "guest" seems to be arbitrary. Molecules can identify each other using non-covalent interactions. Key applications in this area are sensor design and catalysis.
Template Directed Synthesis
Molecular recognition and self-assembly can be used with reactive substances to pre-arrange a chemical reaction system (to form one or more covalent bonds). This can be considered a special case of supramolecular catalysis.
Non-covalent bonds between the reactants and the "matrix" keep the reaction sites close together, promoting the desired chemistry. This methodis particularly useful in situations where the desired reaction conformation is thermodynamically or kinetically unlikely, such as in the production of large macrocycles. This pre-self-organization in supramolecular chemistry also serves purposes such as minimizing side reactions, lowering the activation energy, and obtaining the desired stereochemistry.
After the process has passed, the pattern may remain in place, be forcefully removed, or "automatically" decomplexed due to various product recognition properties. The pattern can be as simple as a single metal ion or extremely complex.
Mechanically interconnected molecular architectures
They are made up of particles that are only connected as a consequence of their topology. Some non-covalent interactions may exist between different components (often those used in the construction of the system), but covalent bonds do not exist. Science - supramolecular chemistry, in particular matrix-directed synthesis, is the key to efficient compounding. Examples of mechanically interconnected molecular architectures include catenanes, rotaxanes, knots, Borromean rings, and ravels.
Dynamic Covalent Chemistry
In it bonds are destroyed and formed in a reversible reaction under thermodynamic control. While covalent bonds are the key to the process, the system is driven by non-covalent forces to form the lowest energy structures.
Biomimetics
Many synthetic supramolecularsystems are designed to copy the functions of biological spheres. These biomimetic architectures can be used to study both the model and the synthetic implementation. Examples include photoelectrochemical, catalytic systems, protein engineering, and self-replication.
Molecular Engineering
These are partial assemblies that can perform functions such as linear or rotational movement, switching and gripping. These devices exist on the frontier between supramolecular chemistry and nanotechnology, and prototypes have been demonstrated using similar concepts. Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa shared the 2016 Nobel Prize in Chemistry for the design and synthesis of molecular machines.
Macrocycles
Macrocycles are very useful in supramolecular chemistry as they provide entire cavities that can completely surround guest molecules and be chemically modified to fine-tune their properties.
Cyclodextrins, calixarenes, cucurbiturils and crown ethers are easily synthesized in large quantities and are therefore convenient for use in supramolecular systems. More complex cyclophanes and cryptands can be synthesized to provide individual recognition properties.
Supramolecular metallocycles are macrocyclic aggregates with metal ions in the ring, often formed from angular and linear modules. Common metallocycle shapes in these types of applications include triangles, squares, andpentagons, each with functional groups that connect parts through "self-assembly".
Metallacrowns are metallomacrocycles generated using a similar approach with fused chelate rings.
Supramolecular chemistry: objects
Many such systems require their components to have suitable spacing and conformations relative to each other, and thus easily usable structural units are required.
Typically, spacers and connecting groups include polyester, biphenyls and triphenyls and simple alkyl chains. The chemistry to create and combine these devices is very well understood.
Surfaces can be used as scaffolding to order complex systems, as well as to interface electrochemicals with electrodes. Regular surfaces can be used to create monolayers and multilayer self-assemblies.
The understanding of intermolecular interactions in solids has undergone a significant renaissance due to the contributions of various experimental and computational techniques in the last decade. This includes high pressure studies in solids and in situ crystallization of compounds that are liquids at room temperature, along with the use of electron density analysis, crystal structure prediction, and solid state DFT calculations to enable quantitative understanding of nature, energetics, and topology.
Photo-electrochemically active units
Porphyrins and phthalocyanines have a highly regulatedphotochemical energy, as well as the potential for complex formation.
Photochromic and photoisomerizable groups have the ability to change their shape and properties when exposed to light.
TTF and quinones have more than one stable oxidation state and can therefore be switched using reduction chemistry or electron science. Other units such as benzidine derivatives, viologen groups, and fullerenes have also been used in supramolecular devices.
Biologically derived units
Extremely strong complexation between avidin and biotin promotes blood clotting and is used as a recognition motif to create synthetic systems.
The binding of enzymes to their cofactors has been used as a route to obtain modified, electrically contacting and even photoswitchable particles. DNA is used as a structural and functional unit in synthetic supramolecular systems.
Material Technology
Supramolecular chemistry has found many applications, in particular, molecular self-assembly processes have been created to develop new materials. Large structures can be easily accessed using a bottom-up process, as they are made up of small molecules that require fewer steps to synthesize. Thus, most approaches to nanotechnology are based on supramolecular chemistry.
Catalysis
It is their development and understanding that is the main application of supramolecular chemistry. Non-covalent interactions are extremely important incatalysis, binding the reactants in conformations suitable for the reaction and lowering the energy in the transition state. Template directed synthesis is a particular case of a supramolecular process. Encapsulation systems such as micelles, dendrimers, and cavitands are also used in catalysis to create a microenvironment suitable for reactions to take place that cannot be used on a macroscopic scale.
Medicine
The method based on supramolecular chemistry has led to numerous applications in the creation of functional biomaterials and therapeutics. They provide a range of modular and generalizable platforms with customizable mechanical, chemical and biological properties. These include systems based on peptide assembly, host macrocycles, high affinity hydrogen bonds, and metal-ligand interactions.
The supramolecular approach has been widely used to create artificial ion channels to transport sodium and potassium in and out of cells.
Such chemistry is also important for the development of new pharmaceutical therapies by understanding drug binding site interactions. The field of drug delivery has also made critical strides as a result of supramolecular chemistry. It provides encapsulation and targeted release mechanisms. In addition, such systems have been designed to disrupt protein-to-protein interactions that are important for cellular function.
Template effect and supramolecular chemistry
In science, a template reaction is any of a class of ligand based actions. They occur between two or more adjacent coordination sites on the metal center. The terms "template effect" and "self-assembly" in supramolecular chemistry are mainly used in coordination science. But in the absence of an ion, the same organic reagents give different products. This is the template effect in supramolecular chemistry.
