chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, a resorcinarene (also resorcarene or calix esorcinarene) is a

macrocycle Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry. ...

, or a

cyclic Cycle, cycles, or cyclic may refer to: Anthropology and social sciences * Cyclic history, a theory of history * Cyclical theory, a theory of American political history associated with Arthur Schlesinger, Sr. * Social cycle, various cycles in s ...

oligomer In chemistry and biochemistry, an oligomer () is a molecule that consists of a few repeating units which could be derived, actually or conceptually, from smaller molecules, monomers.Quote: ''Oligomer molecule: A molecule of intermediate relativ ...

, based on the condensation of

resorcinol Resorcinol (or resorcin) is a phenolic compound. It is an organic compound with the formula C6H4(OH)2. It is one of three isomeric benzenediols, the 1,3-isomer (or ''meta- (chemistry), meta''-isomer). Resorcinol crystallizes from benzene as co ...

(1,3-dihydroxybenzene) and an

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

. Resorcinarenes are a type of

calixarene A calixarene is a macrocycle or cyclic oligomer based on a methylene-linked phenols. With hydrophobic cavities that can hold smaller molecules or ions, calixarenes belong to the class of cavitands known in host–guest chemistry. Nomenclature ...

. Other types of resorcinarenes include the related

pyrogallolarenes A pyrogallolarene (also calix yrogallolarene) is a macrocycle, or a cyclic oligomer, based on the condensation of pyrogallol (1,2,3-trihydroxybenzene) and an aldehyde. Pyrogallolarenes are a type of calixarene, and a subset of resorcinarenes that a ...

and octahydroxypyridines, derived from

pyrogallol Pyrogallol is an organic compound with the formula C6H3(OH)3. It is a water-soluble, white solid although samples are typically brownish because of its sensitivity toward oxygen. It is one of three isomers of benzenetriols. Production and reac ...

and 2,6-dihydroxypyridine, respectively. Resorcinarenes interact with other molecules forming a host–guest complex. Resorcinarenes and pyrogallolarenes

self-assemble Self-assembly is a process in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction. When the ...

into larger supramolecular structures. Both in the crystalline state and in

organic solvent A solvent (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for p ...

s, six resorcinarene molecules are known to form hexamers with an internal volume of around one cubic

nanometer 330px, Different lengths as in respect to the Molecule">molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling Despite the va ...

(nanocapsules) and shapes similar to the

Archimedean solid The Archimedean solids are a set of thirteen convex polyhedra whose faces are regular polygon and are vertex-transitive, although they aren't face-transitive. The solids were named after Archimedes, although he did not claim credit for them. They ...

Hydrogen bond In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...

s appear to hold the assembly together. A number of solvent or other molecules reside inside. The resorcinarene is also the basic structural unit for other molecular recognition scaffolds, typically formed by bridging the phenolic oxygens with alkyl or aromatic spacers. A number of molecular structures are based on this macrocycle, namely

cavitand In chemistry, a cavitand is a container-shaped molecule. The cavity of the cavitand allows it to engage in host–guest chemistry with guest molecules of a complementary shape and size. The original definition proposed by Cram includes many clas ...

s and

carcerand In host–guest chemistry, a carcerand () is a host molecule that completely entraps its guest (which can be an ion, atom or other chemical species) so that it will not escape even at high temperatures. This type of molecule was first described ...

Synthesis

The resorcinarenes are typically prepared by condensation of

and an

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

solution. This reaction was first described by

Adolf von Baeyer Johann Friedrich Wilhelm Adolf von Baeyer (; 31 October 1835 – 20 August 1917) was a German chemist who synthesised indigo dye, indigo and developed a Von Baeyer nomenclature, nomenclature for cyclic compounds (that was subsequently extended a ...

who described the condensation of

and

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is among the simplest aromatic aldehydes and one of the most industrially useful. It is a colorless liquid with a characteristic almond-li ...

but was unable to elucidate the nature of the product(s). The methods have since been refined. Recrystallization typically gives the desired isomer in quite pure form. However, for certain aldehydes, the reaction conditions lead to significant

by-product A by-product or byproduct is a secondary product derived from a production process, manufacturing process or chemical reaction; it is not the primary product or service being produced. A by-product can be useful and marketable or it can be cons ...

s. Alternative condensation conditions have been developed, including the use of

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...

catalysts. center, Preparation of resorcin renes from resorcinol and an aldehyde A

green chemistry Green chemistry, similar to sustainable chemistry or circular chemistry, is an area of chemistry and chemical engineering focused on the design of products and processes that minimize or eliminate the use and generation of hazardous substances. Wh ...

procedure uses solvent-free conditions: resorcinol, an aldehyde, and ''p''-toluenesulfonic acid are ground together in a

mortar and pestle A mortar and pestle is a set of two simple tools used to prepare ingredients or substances by compression (physics), crushing and shear force, grinding them into a fine Paste (rheology), paste or powder in the kitchen, laboratory, and pharmacy. ...

at low temperature.

Structure

Resorcinarenes can be characterized by a wide upper rim and a narrow lower rim. The upper rim includes eight

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

groups that can participate in

hydrogen bonding In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...

interactions. Depending on the aldehyde starting material, the lower rim includes four appending groups, usually chosen to give optimal solubility. The resorcin rene

nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. (The theoretical field studying nomenclature is sometimes referred to as ''onymology'' or ''taxonymy'' ). The principl ...

is analogous to that of calix renes, in which 'n' represents the number of repeating units in the ring.

Pyrogallolarenes A pyrogallolarene (also calix yrogallolarene) is a macrocycle, or a cyclic oligomer, based on the condensation of pyrogallol (1,2,3-trihydroxybenzene) and an aldehyde. Pyrogallolarenes are a type of calixarene, and a subset of resorcinarenes that a ...

are related macrocycles derived from the condensation of

(1,2,3-trihydroxybenzene) with an aldehyde. Resorcinarenes and pyrogallolarenes

to give

supramolecular assemblies 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, ...

. Both in the crystalline state and in solution, they are known to form hexamers that are akin to certain

s with an internal volume of around one cubic

(nanocapsules). (Isobutylpyrogallol rene)₆ is held together by 48

intermolecular An intermolecular force (IMF; also secondary force) is the force that mediates interaction between molecules, including the electromagnetic forces of attraction or repulsion which act between atoms and other types of neighbouring particles (e.g. ...

hydrogen bonds. The remaining 24 hydrogen bonds are intramolecular. The cavity is filled by solvent.

Catalysis

The resorcinarene hexamer has been described as a yoctolitre reaction vessel. Within the confines of the container,

terpene Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n ≥ 2. Terpenes are major biosynthetic building blocks. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predomi ...

cyclizations and

iminium In organic chemistry, an iminium cation is a polyatomic ion with the general structure . They are common in synthetic chemistry and biology. Structure Iminium cations adopt alkene-like geometries: the central C=N unit is nearly coplanar with a ...

catalyzed reactions have been observed.

References

*{{cite journal , author=Palmer LC, Shivanyuk A, Yamanaka M, Rebek J , title=Resorcinarene assemblies as synthetic receptors , journal=

Chemical Communications ''ChemComm'' (or ''Chemical Communications''), formerly known as ''Journal of the Chemical Society D: Chemical Communications'' (1969–1971), ''Journal of the Chemical Society, Chemical Communications'' (1972–1995), is a peer-reviewed scientific ...

, volume=2005 , issue=7 , year=2005 , pages=857–858 , doi=10.1039/b414252g , pmid=15700060 , last4=Rebek Supramolecular chemistry Macrocycles Cyclophanes