Jump to content

Host–guest chemistry

From Wikipedia, the free encyclopedia
(Redirected from Cage compound)

In supramolecular chemistry,[1] 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.

Although non-covalent interactions could be roughly divided into those with more electrostatic or dispersive contributions, there are few commonly mentioned types of non-covalent interactions: ionic bonding, hydrogen bonding, van der Waals forces and hydrophobic interactions.[2]

Host-guest interaction has raised dramatical attention since it was discovered. It is an important field, because many biological processes require the host-guest interaction, and it can be useful in some material designs. There are several typical host molecules, such as, cyclodextrin, crown ether, et al.

Crystal structure of a host–guest complex with a p-xylylenediammonium bound within a cucurbituril [3]
A guest N2 is bound within a host hydrogen-bonded capsule [4]

"Host molecules" usually have "pore-like" structure that is able to capture a "guest molecules". Although called molecules, hosts and guests are often ions. The driving forces of the interaction might vary, such as hydrophobic effect and van der Waals forces[5][5][6][7][8]

Binding between host and guest can be highly selective, in which case the interaction is called molecular recognition. Often, a dynamic equilibrium exist between the unbound and the bound states:

H ="host", G ="guest", HG ="host–guest complex"

The "host" component is often the larger molecule, and it encloses the smaller, "guest", molecule. In biological systems, the analogous terms of host and guest are commonly referred to as enzyme and substrate respectively.[9]

Inclusion and clathrate compounds

[edit]
Cd(CN)2·CCl4: Cadmium cyanide clathrate framework (in blue) containing carbon tetrachloride (C atoms in gray and disordered Cl positions in green).

Closely related to host–guest chemistry, are inclusion compounds (also known as an inclusion complexes). Here, a chemical complex in which one chemical compound (the "host") has a cavity into which a "guest" compound can be accommodated. The interaction between the host and guest involves purely van der Waals bonding. The definition of inclusion compounds is very broad, extending to channels formed between molecules in a crystal lattice in which guest molecules can fit.

IUPAC definition

Inclusion Compound: A complex in which one component (the host) forms a cavity or, in the case of a crystal, a crystal lattice containing spaces in the shape of long tunnels or channels in which molecular entities of a second chemical species (the guest) are located. There is no covalent bonding between guest and host, the attraction being generally due to van der Waals forces.[10]

Yet another related class of compounds are clathrates, which often consisting of a lattice that traps or contains molecules.[11] The word clathrate is derived from the Latin clathratus (clatratus), meaning 'with bars, latticed'.[12]

Molecular encapsulation

[edit]

Molecular encapsulation concerns the confinement of a guest within a larger host. In some cases, true host-guest reversibility is observed, in other cases, the encapsulated guest cannot escape.[13]

Molecular encapsulation of a nitrobenzene bound within a hemicarcerand.[14]

An important implication of encapsulation (and host-guest chemistry in general) is that the guest behaves differently from the way it would when in solution. Guest molecules that would react by bimolecular pathways are often stabilized because they cannot combine with other reactants. The spectroscopic signatures of trapped guests are of fundamental interest. Compounds normally highly unstable in solution have been isolated at room temperature when molecularly encapsulated. Examples include cyclobutadiene,[15] arynes or cycloheptatetraene.[16][17] Large metalla-assemblies, known as metallaprisms, contain a conformationally flexible cavity that allows them to host a variety of guest molecules. These assemblies have shown promise as agents of drug delivery to cancer cells.

Encapsulation can control reactivity. For instance, excited state reactivity of free 1-phenyl-3-tolyl-2-proponanone (abbreviated A-CO-B) yields products A-A, B-B, and AB, which result from decarbonylation followed by random recombination of radicals A• and B•. Whereas, the same substrate upon encapsulation reacts to yield the controlled recombination product A-B, and rearranged products (isomers of A-CO-B).[18]

Macrocyclic hosts

[edit]

Organic hosts are occasionally called cavitands. The original definition proposed by Cram includes many classes of molecules: cyclodextrins, calixarenes, pillararenes and cucurbiturils.[19]

Calixarenes

[edit]

Calixarenes and related formaldehyde-arene condensates (resorcinarenes and pyrogallolarenes) form a class of hosts that form inclusion compounds.[5][20] A related family of formaldehyde-derived oligomeric rings are pillararenes (pillered arenes). One famous illustration of the stabilizing effect of host-guest complexation is the stabilization of cyclobutadiene by such an organic host.[21]

Cyclodextrins and cucurbiturils

[edit]
Chemical structure of pillar[5]arene

Cyclodextrin (CD) are tubular molecules composed of several glucose units connected by ether bonds. The three kinds of CDs, α-CD (6 units), β-CD (7 units), and γ-CD (8 units) differ in their cavity sizes: 5, 6, and 8 Å, respectively. α-CD can thread onto one PEG chain, while γ-CD can thread onto 2 PEG chains. β-CD can bind with thiophene-based molecule.[5] Cyclodextrins are well established hosts for the formation of inclusion compounds.[1][2][3] Illustrative is the case of ferrocene which is inserted into the cyclodextrin at 100 °C under hydrothermal conditions.[22]

Cucurbiturils are macrocyclic molecules made of glycoluril (=C4H2N4O2=) monomers linked by methylene bridges (−CH2). The oxygen atoms are located along the edges of the band and are tilted inwards, forming a partly enclosed cavity (cavitand). . Cucurbit[n]urils have similar size of γ-CD, which also behave similarly (e.g., 1 cucurbit[n]uril can thread onto 2 PEG chains).[5]

Cryptophanes

[edit]
a) Structure of Cryptophanes. b) Structure of Resorcinarenes and Pyrogallolarenes. c) Structure of cucurbit[n]urils. Redrawn from.[5]

The structure of cryptophanes contain 6 phenyl rings, mainly connected in 4 ways . Due to the phenyl groups and aliphatic chains, the cages inside cryptophanes are highly hydrophobic, suggesting the capability of capturing non-polar molecules. Based on this, cryptophanes can be employed to capture xenon in aqueous solution, which could be helpful in biological studies.[5]

Crown ethers and cryptands

[edit]
a) Structure of 18-crown-6. b) Threading of crown ether and 1,2,3-triazole (rotaxane). Redrawn from [3]. c) Inclusion of a-CD and polyethylene glycol (PEG) d) Threading of b-cyclodextrin and thiophene-based molecule. Redrawn from.[5]

Crown ethers bind cations. Small crown ethers, e.g. 12-crown-4 bind well to small ions such as Li+ and large crowns, such as 24-crown-8 bind better to larger ions.[5] Beyond binding ionic guests, crown ethers also bind to some neutral molecules, e.g., 1, 2, 3- triazole. Crown ethers can also be threaded with slender linear molecules and/or polymers, giving rise to supramolecular structures called rotaxanes. Given that the crown ethers are not bound to the chains, they can move up and down the threading molecule.[8] Crown ether complexes of metal cations (and the corresponding complexes of Cryptands) are not considered to be inclusion complexes since the guest is bound by forces stronger than van der Waals bonding.

Polymeric hosts

[edit]

Zeolites have open framework structures with cavities in which guest species can reside. Aluminosilicates being their composition, zeolites are rigid. Many structures are known, some of which are considerably useful as catalysts and for separations.[11]

Silica clathrasil are compounds structurally similar to clathrate hydrates with a SiO2 framework and can be found in a range of marine sediment.[23]

Clathrate compounds with formula A8B16X30, where A is an alkaline earth metal, B is a group III element, and X is an element from group IV have been explored for thermoelectric devices. Thermoelectric materials follow a design strategy called the phonon glass electron crystal concept.[24][25] Low thermal conductivity and high electrical conductivity is desired to produce the Seebeck Effect. When the guest and host framework are appropriately tuned, clathrates can exhibit low thermal conductivity, i.e., phonon glass behavior, while electrical conductivity through the host framework is undisturbed allowing clathrates to exhibit electron crystal.

Hofmann clathrates are coordination polymers with the formula Ni(CN)4·Ni(NH3)2(arene). These materials crystallize with small aromatic guests (benzene, certain xylenes), and this selectivity has been exploited commercially for the separation of these hydrocarbons.[11] Metal organic frameworks (MOFs) form clathrates.

MOF-5, an example of a metal organic framework: the yellow sphere represents the guest cavity.

Urea, a small molecule with the formula O=C(NH2)2, has the peculiar property of crystallizing in open but rigid networks. The cost of efficient molecular packing is compensated by hydroge-bonding. Ribbons of hydrogen-bonded urea molecules form tunnel-like host into which many organic guests bind. Urea-clathrates have been well investigated for separations.[26] Beyond urea, several other organic molecules form clathrates: [[[thiourea]], hydroquinone, and Dianin's compound.[11]

Thermodynamics of host-guest interactions

[edit]

When the host and guest molecules combine to form a single complex, the equilibrium is represented as

and the equilibrium constant, K, is defined as

where [X] denotes the concentration of a chemical species X (all activity coefficients are assumed to have a numerical values of 1). The mass-balance equations, at any data point,

where and represent the total concentrations, of host and guest, can be reduced to a single quadratic equation in, say, [G] and so can be solved analytically for any given value of K. The concentrations [H] and [HG] can then derived.

The next step in the calculation is to calculate the value, , of a quantity corresponding to the quantity observed . Then, a sum of squares, U, over all data points, np, can be defined as

and this can be minimized with respect to the stability constant value, K, and a parameter such the chemical shift of the species HG (nmr data) or its molar absorbency (uv/vis data). This procedure is applicable to 1:1 adducts.

Experimental techniques

[edit]
Set of NMR spectra from a host–guest titration
Typical ultraviolet–visible spectra for a host–guest system

With nuclear magnetic resonance (NMR) spectra the observed chemical shift value, δ, arising from a given atom contained in a reagent molecule and one or more complexes of that reagent, will be the concentration-weighted average of all shifts of those chemical species. Chemical exchange is assumed to be rapid on the NMR time-scale.

Using UV-vis spectroscopy, the absorbance of each species is proportional to the concentration of that species, according to the Beer–Lambert law.

where λ is a wavelength, is the optical path length of the cuvette which contains the solution of the N compounds (chromophores), is the molar absorbance (also known as the extinction coefficient) of the ith chemical species at the wavelength λ, ci is its concentration. When the concentrations have been calculated as above and absorbance has been measured for samples with various concentrations of host and guest, the Beer–Lambert law provides a set of equations, at a given wavelength, that which can be solved by a linear least-squares process for the unknown extinction coefficient values at that wavelength.

Host-guest structures can be probed by their luminescence. A rigid matrix protects emitters from being quenched, extending the lifetime of phosphoresce.[27] In this circumstance, α-CD and CB could be used,[28][29] in which the phosphor is served as a guest to interact with the host. For example, 4-phenylpyridium derivatives interacted with CB, and copolymerize with acrylamide. The resulting polymer yielded ~2 s of phosphorescence lifetime. Additionally, Zhu et al used crown ether and potassium ion to modify the polymer, and enhance the emission of phosphorescence.[30]

Another technique for evaluating host-guest interactions is calorimetry.

Aspiration applications

[edit]

Host guest complexation is pervasive in biochemistry. Many protein hosts recognize and hence selectively bind other biomolecules. When the protein host is an enzyme, the guests are called substrates. While these concepts are well established in biological systems, the applications of synthetic host-guest chemistry remains mostly in the realm of aspiration. One major exception, being zeolites where host-guest chemistry is their raison d'etre.

Self-healing

[edit]
Self-healing mechanism of host-guest interaction by a) using host-small guest molecule and b) host-polymer. Redrawn from [31][32]

A self-healing hydrogel constructed from modified cyclodextrin and adamantane .[31][33] Another strategy is to use the interaction between the polymer backbone and host molecule (host molecule threading onto the polymer). If the threading process is fast enough, self-healing can also be achieved.[32]

Encapsulation and release: fragrances and drugs

[edit]

Cyclodextrin forms inclusion compounds with fragrances which are more stable towards exposure to light and air. When incorporated into textiles the fragrance lasts much longer due to the slow-release action.[34]

Photolytically-sensitive caged compounds have been examined as containers for releasing a drug or reagent.[35][36]

Encryption

[edit]

An encryption system constructed by pillar[5]arene, spiropyran and pentanenitrile (free state and grafted to polymer) was constructed by Wang et al. After UV irradiation, spiropyran would transform into merocyanine. When the visible light was shined on the material, the merocyanine close to the pillar[5]arene-free pentanenitrile complex had faster transformation to spiropyran; on the contrary, the one close to pillar[5]arene-grafted pentanenitrile complex has much slower transformation rate. This spiropyran-merocyanine transformation can be used for message encryption.[37] Another strategy is based on the metallacages and polycyclic aromatic hydrocarbons.[38] Because of the fluorescnece emission differences between the complex and the cages, the information could be encrypted.

Mechanical property

[edit]

Although some host-guest interactions are not strong, increasing the amount of the host-guest interaction can improve the mechanical properties of the materials. As an example, threading the host molecules onto the polymer is one of the commonly used strategies for increasing the mechanical properties of the polymer. It takes time for the host molecules to de-thread from the polymer, which can be a way of energy dissipation.[33][39][40] Another method is to use the slow exchange host-guest interaction. Though the slow exchange improves the mechanical properties, simultaneously, self-healing properties will be sacrificed.[41]

Sensing

[edit]

Silicon surfaces functionalized with tetraphosphonate cavitands have been used to singularly detect sarcosine in water and urine solutions.[42]

Traditionally, chemical sensing has been approached with a system that contains a covalently bound indicator to a receptor though a linker. Once the analyte binds, the indicator changes color or fluoresces. This technique is called the indicator-spacer-receptor approach (ISR).[43] In contrast to ISR, indicator-displacement assay (IDA) utilizes a non-covalent interaction between a receptor (the host), indicator, and an analyte (the guest). Similar to ISR, IDA also utilizes colorimetric (C-IDA) and fluorescence (F-IDA) indicators. In an IDA assay, a receptor is incubated with the indicator. When the analyte is added to the mixture, the indicator is released to the environment. Once the indicator is released it either changes color (C-IDA) or fluoresces (F-IDA).[44]

Types of Chemosensors. (1.) Indicator-spacer-receptor (ISR) (2.) Indicator-Displacement Assay (IDA)

IDA offers several advantages versus the traditional ISR chemical sensing approach. First, it does not require the indicator to be covalently bound to the receptor. Secondly, since there is no covalent bond, various indicators can be used with the same receptor. Lastly, the media in which the assay may be used is diverse.[45]

Indicator-Displacement Assay Indicators. (1.) Azure A (2.) thiazole orange

Chemical sensing techniques such as C-IDA have biological implications. For example, protamine is a coagulant that is routinely administered after cardiopulmonary surgery that counter acts the anti-coagulant activity of herapin. In order to quantify the protamine in plasma samples, a colorimetric displacement assay is used. Azure A dye is blue when it is unbound, but when it is bound to herapin, it shows a purple color. The binding between Azure A and heparin is weak and reversible. This allows protamine to displace Azure A. Once the dye is liberated it displays a purple color. The degree to which the dye is displaced is proportional to the amount of protamine in the plasma.[46]

F-IDA has been used by Kwalczykowski and co-workers to monitor the activities of helicase in E.coli. In this study they used thiazole orange as the indicator. The helicase unwinds the dsDNA to make ssDNA. The fluorescence intensity of thiazole orange has a greater affinity for dsDNA than ssDNA and its fluorescence intensity increases when it is bound to dsDNA than when it is unbound.[47][48]

Conformational switching

[edit]

A crystalline solid has been traditionally viewed as a static entity where the movements of its atomic components are limited to its vibrational equilibrium. As seen by the transformation of graphite to diamond, solid to solid transformation can occur under physical or chemical pressure. It has been proposed that the transformation from one crystal arrangement to another occurs in a cooperative manner.[49][50] Most of these studies have been focused in studying an organic or metal-organic framework.[51][52] In addition to studies of macromolecular crystalline transformation, there are also studies of single-crystal molecules that can change their conformation in the presence of organic solvents. An organometallic complex has been shown to morph into various orientations depending on whether it is exposed to solvent vapors or not.[53]

Environmental applications

[edit]

Host guest systems have been proposed to remove hazardous materials. Certain calix[4]arenes bind cesium-137 ions, which could in principle be applied to clean up radioactive wastes. Some receptors binds carcinogens.[54][55]

Alcohol

[edit]

According to food chemist Udo Pollmer of the European Institute of Food and Nutrition Sciences in Munich, alcohol can be molecularly encapsulated in cyclodextrines, a sugar derivate. In this way, encapsuled in small capsules, the fluid can be handled as a powder. The cyclodextrines can absorb an estimated 60 percent of their own weight in alcohol.[56] A US patent has been registered for the process as early as 1974.[57]

See also

[edit]

Further reading

[edit]
  • Dsouza, Roy N.; Pischel, Uwe; Nau, Werner M. (2011). "Fluorescent Dyes and Their Supramolecular Host/Guest Complexes with Macrocycles in Aqueous Solution". Chemical Reviews. 111 (12): 7941–7980. doi:10.1021/cr200213s. PMID 21981343.
  • Yu, Guocan; Jie, Kecheng; Huang, Feihe (2015). "Supramolecular Amphiphiles Based on Host–Guest Molecular Recognition Motifs". Chemical Reviews. 115 (15): 7240–7303. doi:10.1021/cr5005315. PMID 25716119.
  • Hu, Jingjing; Xu, Tongwen; Cheng, Yiyun (2012). "NMR Insights into Dendrimer-Based Host–Guest Systems". Chemical Reviews. 112 (7): 3856–3891. doi:10.1021/cr200333h. PMID 22486250.
  • Xia, Danyu; Wang, Pi; Ji, Xiaofan; Khashab, Niveen M.; Sessler, Jonathan L.; Huang, Feihe (2020). "Functional Supramolecular Polymeric Networks: The Marriage of Covalent Polymers and Macrocycle-Based Host–Guest Interactions". Chemical Reviews. 120 (13): 6070–6123. doi:10.1021/acs.chemrev.9b00839. PMID 32426970.
  • Qu, Da-Hui; Wang, Qiao-Chun; Zhang, Qi-Wei; Ma, Xiang; Tian, He (2015). "Photoresponsive Host–Guest Functional Systems". Chemical Reviews. 115 (15): 7543–7588. doi:10.1021/cr5006342.

References

[edit]
  1. ^ Steed, Jonathan W.; Atwood, Jerry L. (2009). Supramolecular Chemistry (2nd. ed.). Wiley. p. 1002. ISBN 978-0-470-51234-0.
  2. ^ Lodish, H.; Berk, A.; Kaiser, C. (2008). Molecular Cell Biology. Macmillan. ISBN 978-0-7167-7601-7.
  3. ^ Freeman, Wade A. (1984). "Structures of the p-xylylenediammonium chloride and calcium hydrogensulfate adducts of the cavitand 'cucurbituril', C36H36N24O12". Acta Crystallographica B. 40 (4): 382–387. doi:10.1107/S0108768184002354.
  4. ^ Valdés, Carlos; Toledo, Leticia M.; Spitz, Urs; Rebek, Julius (1996). "Structure and Selectivity of a Small Dimeric Encapsulating Assembly". Chem. Eur. J. 2 (8): 989–991. doi:10.1002/chem.19960020814.
  5. ^ a b c d e f g h i Comprehensive supramolecular chemistry II. J. L. Atwood, George W. Gokel, Leonard J. Barbour. Amsterdam, Netherlands. 2017. ISBN 978-0-12-803199-5. OCLC 992802408.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
  6. ^ Stoddart, J. F. (1988). "Chapter 12. Host–guest chemistry". Annu. Rep. Prog. Chem., Sect. B: Org. Chem. 85: 353–386. doi:10.1039/OC9888500353. ISSN 0069-3030.
  7. ^ Harada, Akira (2013), "Supramolecular Polymers (Host-Guest Interactions)", in Kobayashi, Shiro; Müllen, Klaus (eds.), Encyclopedia of Polymeric Nanomaterials, Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 1–5, doi:10.1007/978-3-642-36199-9_54-1, ISBN 978-3-642-36199-9, retrieved 2023-02-15
  8. ^ a b Seale, James S. W.; Feng, Yuanning; Feng, Liang; Astumian, R. Dean; Stoddart, J. Fraser (2022). "Polyrotaxanes and the pump paradigm". Chemical Society Reviews. 51 (20): 8450–8475. doi:10.1039/D2CS00194B. ISSN 0306-0012. PMID 36189715. S2CID 252682455.
  9. ^ Anslyn, Eric V.; Dougherty, Dennis A. (2005). Modern Physical Organic Chemistry. MacMillan. ISBN 978-1-891389-31-3.
  10. ^ "inclusion compound (inclusion complex)".
  11. ^ a b c d Atwood, J. L. (2012) "Inclusion Compounds" in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim. doi:10.1002/14356007.a14_119
  12. ^ Latin dictionary Archived 2012-04-14 at the Wayback Machine
  13. ^ Yan Voloshin, Irina Belaya, Roland Krämer (2016). The Encapsulation Phenomenon Synthesis, Reactivity and Applications of Caged Ions and Molecules. Springer. ISBN 9783319277387.{{cite book}}: CS1 maint: multiple names: authors list (link)
  14. ^ Donald J. Cram and coworkers (1997). Chem. Commun.: 1303-1304. {{cite journal}}: Missing or empty |title= (help)
  15. ^ Cram, D. J.; Tanner, M. E.; Thomas, R., The Taming of Cyclobutadiene Angewandte Chemie International Edition Volume 30, Issue 8, Pages 1024 - 1027 1991
  16. ^ Dorothea Fiedler, Robert G. Bergman, Kenneth N. Raymond (2006). "Stabilization of Reactive Organometallic Intermediates Inside a Self-Assembled Nanoscale Host". Angewandte Chemie International Edition. 45: 745. doi:10.1002/anie.200501938.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ^ Fraser Hof; Stephen L. Craig; Colin Nuckolls; Julius Rebek Jr. (May 3, 2002). "Molecular Encapsulation". Angewandte Chemie International Edition. 41 (9): 1488–1508. doi:10.1002/1521-3773(20020503)41:9<1488::AID-ANIE1488>3.0.CO;2-G. PMID 19750648.
  18. ^ Kaanumalle, Lakshmi S (Oct 20, 2004). "Controlling Photochemistry with Distinct Hydrophobic Nanoenvironments". J. Am. Chem. Soc. 126 (44): 14366–14367. doi:10.1021/la203419y. PMID 15521751.
  19. ^ Cai, X.; Gibb, B. C. (2017). "6.04 - Deep-Cavity Cavitands in Self-Assembly". In Atwood, Jerry (ed.). Comprehensive Supramolecular Chemistry II. Elsevier. pp. 75–82. ISBN 9780128031995.
  20. ^ Wishard, A.; Gibb, B.C. (2016). "A chronology of cavitands". Calixarenes and beyond. Springer. pp. 195–234. doi:10.1007/978-3-319-31867-7_9. ISBN 978-3-319-31867-7.
  21. ^ Cram, Donald J.; Tanner, Martin E.; Thomas, Robert (1991). "The Taming of Cyclobutadiene Donald J. Cram, Martin E. Tanner, Robert Thomas". Angewandte Chemie International Edition in English. 30 (8): 1024–1027. doi:10.1002/anie.199110241.
  22. ^ Yu Liu; Rui-Qin Zhong; Heng-Yi Zhang; Hai-Bin Song (2010). "A unique tetramer of 4:5 -cyclodextrin–ferrocene in the solid state". Chemical Communications (17): 2211–2213. doi:10.1039/B418220K. PMID 15856099.
  23. ^ Momma, Koichi; Ikeda, Takuji; Nishikubo, Katsumi; Takahashi, Naoki; Honma, Chibune; Takada, Masayuki; Furukawa, Yoshihiro; Nagase, Toshiro; Kudoh, Yasuhiro (September 2011). "New silica clathrate minerals that are isostructural with natural gas hydrates". Nature Communications. 2 (1): 196. Bibcode:2011NatCo...2..196M. doi:10.1038/ncomms1196. ISSN 2041-1723. PMID 21326228.
  24. ^ Nolas, G. S.; Cohn, J. L.; Slack, G. A.; Schujman, S. B. (1998-07-13). "Semiconducting Ge clathrates: Promising candidates for thermoelectric applications". Applied Physics Letters. 73 (2): 178–180. Bibcode:1998ApPhL..73..178N. doi:10.1063/1.121747. ISSN 0003-6951.
  25. ^ Beekman, M., Morelli, D. T., Nolas, G. S. (2015). "Better thermoelectrics through glass-like crystals". Nature Materials. 14 (12): 1182–1185. Bibcode:2015NatMa..14.1182B. doi:10.1038/nmat4461. ISSN 1476-4660. PMID 26585077.
  26. ^ Worsch, Detlev; Vögtle, Fritz (2002). "Separation of enantiomers by clathrate formation". Topics in Current Chemistry. Springer-Verlag. pp. 21–41. doi:10.1007/bfb0003835. ISBN 3-540-17307-2.
  27. ^ Dai, Wenbo; Niu, Xiaowei; Wu, Xinghui; Ren, Yue; Zhang, Yongfeng; Li, Gengchen; Su, Han; Lei, Yunxiang; Xiao, Jiawen; Shi, Jianbing; Tong, Bin; Cai, Zhengxu; Dong, Yuping (2022-03-21). "Halogen Bonding: A New Platform for Achieving Multi‐Stimuli‐Responsive Persistent Phosphorescence". Angewandte Chemie International Edition. 61 (13): e202200236. doi:10.1002/anie.202200236. ISSN 1433-7851. PMID 35102661. S2CID 246443916.
  28. ^ Yan, Xi; Peng, Hao; Xiang, Yuan; Wang, Juan; Yu, Lan; Tao, Ye; Li, Huanhuan; Huang, Wei; Chen, Runfeng (January 2022). "Recent Advances on Host–Guest Material Systems toward Organic Room Temperature Phosphorescence". Small. 18 (1): 2104073. doi:10.1002/smll.202104073. ISSN 1613-6810. PMID 34725921. S2CID 240421091.
  29. ^ Xu, Wen‐Wen; Chen, Yong; Lu, Yi‐Lin; Qin, Yue‐Xiu; Zhang, Hui; Xu, Xiufang; Liu, Yu (February 2022). "Tunable Second‐Level Room‐Temperature Phosphorescence of Solid Supramolecules between Acrylamide–Phenylpyridium Copolymers and Cucurbit[7]uril". Angewandte Chemie International Edition. 61 (6): e202115265. doi:10.1002/anie.202115265. ISSN 1433-7851. PMID 34874598. S2CID 244922727.
  30. ^ Zhu, Weijie; Xing, Hao; Li, Errui; Zhu, Huangtianzhi; Huang, Feihe (2022-11-08). "Room-Temperature Phosphorescence in the Amorphous State Enhanced by Copolymerization and Host–Guest Complexation". Macromolecules. 55 (21): 9802–9809. Bibcode:2022MaMol..55.9802Z. doi:10.1021/acs.macromol.2c00680. ISSN 0024-9297. S2CID 253051272.
  31. ^ a b Ikura, Ryohei; Park, Junsu; Osaki, Motofumi; Yamaguchi, Hiroyasu; Harada, Akira; Takashima, Yoshinori (December 2022). "Design of self-healing and self-restoring materials utilizing reversible and movable crosslinks". NPG Asia Materials. 14 (1): 10. Bibcode:2022npjAM..14...10I. doi:10.1038/s41427-021-00349-1. ISSN 1884-4049.
  32. ^ a b Xie, Jing; Yu, Peng; Wang, Zhanhua; Li, Jianshu (2022-03-14). "Recent Advances of Self-Healing Polymer Materials via Supramolecular Forces for Biomedical Applications". Biomacromolecules. 23 (3): 641–660. doi:10.1021/acs.biomac.1c01647. ISSN 1525-7797. PMID 35199999. S2CID 247082155.
  33. ^ a b Park, Junsu; Murayama, Shunsuke; Osaki, Motofumi; Yamaguchi, Hiroyasu; Harada, Akira; Matsuba, Go; Takashima, Yoshinori (October 2020). "Extremely Rapid Self‐Healable and Recyclable Supramolecular Materials through Planetary Ball Milling and Host–Guest Interactions". Advanced Materials. 32 (39): 2002008. doi:10.1002/adma.202002008. ISSN 0935-9648. PMID 32844527. S2CID 221326154.
  34. ^ Wang, C. X.; Chen, Sh. L. (2005). "Fragrance-release Property of β-Cyclodextrin Inclusion Compounds and their Application in Aromatherapy". Journal of Industrial Textiles. 34 (3): 157–166. doi:10.1177/1528083705049050. S2CID 95538902.
  35. ^ Ellis-Davies, Graham C. R. (2007). "Caged compounds: Photorelease technology for control of cellular chemistry and physiology". Nature Methods. 4 (8): 619–628. doi:10.1038/nmeth1072. PMC 4207253. PMID 17664946.
  36. ^ Blanco-Gómez, Arturo; Cortón, Pablo; Barravecchia, Liliana; Neira, Iago; Pazos, Elena; Peinador, Carlos; García, Marcos D. (2020). "Controlled binding of organic guests by stimuli-responsive macrocycles". Chemical Society Reviews. 49 (12): 3834–3862. doi:10.1039/D0CS00109K. hdl:2183/31671. ISSN 0306-0012. PMID 32395726. S2CID 218599759.
  37. ^ Ju, Huaqiang; Zhu, Chao Nan; Wang, Hu; Page, Zachariah A.; Wu, Zi Liang; Sessler, Jonathan L.; Huang, Feihe (February 2022). "Paper without a Trail: Time‐Dependent Encryption using Pillar[5]arene‐Based Host–Guest Invisible Ink". Advanced Materials. 34 (6): 2108163. Bibcode:2022AdM....3408163J. doi:10.1002/adma.202108163. ISSN 0935-9648. PMID 34802162. S2CID 244482426.
  38. ^ Hou, Yali; Zhang, Zeyuan; Lu, Shuai; Yuan, Jun; Zhu, Qiangyu; Chen, Wei-Peng; Ling, Sanliang; Li, Xiaopeng; Zheng, Yan-Zhen; Zhu, Kelong; Zhang, Mingming (2020-11-04). "Highly Emissive Perylene Diimide-Based Metallacages and Their Host–Guest Chemistry for Information Encryption". Journal of the American Chemical Society. 142 (44): 18763–18768. doi:10.1021/jacs.0c09904. ISSN 0002-7863. PMID 33085462. S2CID 224824066.
  39. ^ Jin, Jia‐Ni; Yang, Xi‐Ran; Wang, Yan‐Fang; Zhao, Lei‐Min; Yang, Liu‐Pan; Huang, Liping; Jiang, Wei (2023-01-18). "Mechanical Training Enabled Reinforcement of Polyrotaxane‐Containing Hydrogel". Angewandte Chemie. 135 (8). doi:10.1002/ange.202218313. ISSN 0044-8249.
  40. ^ Wang, Shuaipeng; Chen, Yong; Sun, Yonghui; Qin, Yuexiu; Zhang, Hui; Yu, Xiaoyong; Liu, Yu (2022-01-20). "Stretchable slide-ring supramolecular hydrogel for flexible electronic devices". Communications Materials. 3 (1): 2. Bibcode:2022CoMat...3....2W. doi:10.1038/s43246-022-00225-7. ISSN 2662-4443.
  41. ^ Huang, Zehuan; Chen, Xiaoyi; O’Neill, Stephen J. K.; Wu, Guanglu; Whitaker, Daniel J.; Li, Jiaxuan; McCune, Jade A.; Scherman, Oren A. (January 2022). "Highly compressible glass-like supramolecular polymer networks". Nature Materials. 21 (1): 103–109. Bibcode:2022NatMa..21..103H. doi:10.1038/s41563-021-01124-x. ISSN 1476-1122. PMID 34819661. S2CID 244532641.
  42. ^ Biavardi, Elisa (February 14, 2011). "Exclusive recognition of sarcosine in water and urine by a cavitand-functionalized silicon surface". Proceedings of the National Academy of Sciences of the United States of America. 109 (7): 2263–2268. Bibcode:2012PNAS..109.2263B. doi:10.1073/pnas.1112264109. PMC 3289311. PMID 22308349.
  43. ^ de Silva, A.P.; McCaughan, B; McKinney, B.O. F.; Querol, M. (2003). "Newer optical-based molecular devices from older coordination chemistry". Dalton Transactions. 10 (10): 1902–1913. doi:10.1039/b212447p.
  44. ^ Anslyn, E. (2007). "Supramolecular Analytical Chemistry". Journal of Organic Chemistry. 72 (3): 687–699. doi:10.1021/jo0617971. PMID 17253783.
  45. ^ Nguyen, B.; Anslyn, E. (2006). "Indicator-displacement assays". Coord. Chem. Rev. 250 (23–24): 3118–3127. doi:10.1016/j.ccr.2006.04.009.
  46. ^ Yang, V.; Fu, Y.; Teng, C.; Ma, S.; Shanberge, J. (1994). "A method for the quantitation of protamine in plasma" (PDF). Thrombosis Research. 74 (4): 427–434. doi:10.1016/0049-3848(94)90158-9. hdl:2027.42/31577. PMID 7521974.
  47. ^ Eggleston, A.; Rahim, N.; Kowalczykowski, S; Ma, S.; Shanberge, J. (1996). "A method for the quantitation of protamine in plasma". Nucleic Acids Research. 24 (7): 1179–1186. doi:10.1093/nar/24.7.1179. PMC 145774. PMID 8614617.
  48. ^ Biancardi, Alessandro; Tarita, Biver; Alberto, Marini; Benedetta, Mennucci; Fernando, Secco (2011). "Thiazole orange (TO) as a light-switch probe: a combined quantum-mechanical and spectroscopic study". Physical Chemistry Chemical Physics. 13 (27): 12595–12602. Bibcode:2011PCCP...1312595B. doi:10.1039/C1CP20812H. PMID 21660321.
  49. ^ Atwood, J; Barbour, L; Jerga, A; Schottel, L (2002). "Guest Transport in a nonporous Organic Solid via Dynamic van der Waals Cooperativity". Science. 298 (5595): 1000–1002. Bibcode:2002Sci...298.1000A. doi:10.1126/science.1077591. PMID 12411698. S2CID 17584598.
  50. ^ Kitagawa, S; Uemura, K (2005). "Dynamic porous properties of coordination polymers inspired by hydrogen bonds". Chemical Society Reviews. 34 (2): 109–119. doi:10.1039/b313997m. PMID 15672175.
  51. ^ Sozzani, P; Bracco, S; Commoti, A; Ferretti, R; Simonutti, R (2005). "Methane and Carbon Dioxide Storage in a Porous van der Waals Crystal". Angewandte Chemie. 44 (12): 1816–1820. doi:10.1002/anie.200461704. PMID 15662674.
  52. ^ Uemura, K; Kitagawa, S; Fukui, K; Saito, K (2004). "A Contrivance for a Dynamic Porous Framework: Cooperative Guest Adsorption Based on Square Grids Connected by Amide−Amide Hydrogen Bonds". J. Am. Chem. Soc. 126 (12): 3817–3828. doi:10.1021/ja039914m. PMID 15038736.
  53. ^ Dobrzanska, L; Lloyd, G; Esterhuysen, C; Barbour, L (2006). "Guest-Induced Conformational Switching in a Single Crystal". Angewandte Chemie. 45 (35): 5856–5859. doi:10.1002/anie.200602057. PMID 16871642.
  54. ^ Eric Hughes; Jason Jordan; Terry Gullion (2001). "Structural Characterization of the [Cs(p-tert-butylcalix[4]arene -H) (MeCN)] Guest–Host System by 13C-133Cs REDOR NMR". Journal of Physical Chemistry B. 105 (25): 5887–5891. doi:10.1021/jp004559x.
  55. ^ Serkan Erdemir; Mufit Bahadir; Mustafa Yilmaz (2009). "Extraction of Carcinogenic Aromatic Amines from Aqueous Solution Using Calix[n]arene Derivatives as Carriers". Journal of Hazardous Materials. 168 (2–3): 1170–1176. doi:10.1016/j.jhazmat.2009.02.150. PMID 19345489.
  56. ^ Alcohol powder: Alcopops from a bag Archived 2007-09-27 at the Wayback Machine, Westdeutsche Zeitung, 28 October 2004 (German)
  57. ^ Preparation of an Alcohol Containing Powder, General Foods Corporation March 31, 1972