A cucurbituril-based molecular switch

Mock, William L.; Pierpont, John

doi:10.1039/c39900001509

Cited by 132 publications

(99 citation statements)

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“…Mock 75 e seu grupo mostraram, pela primeira vez em 1990, que era possível sintetizar compostos deste tipo, capazes de interconverter-se em uma forma ou outra, simplesmente alterando o pH do meio. Utilizando triaminas lineares e assimétricas (Figura 4) é possível protonar os grupos amina seletivamente, contando com as diferenças de pK a existentes entres os diferentes íons de amônio da molécula.…”

Section: Rotaxanos Pseudo-rotaxanos Rolamentos E Chaveadores Molecuunclassified

“…Este é um chaveador molecular bastante simples, mas que deu origem a diversos outros, como os chaveadores contendo fluoróforos, que permitem a leitura de seus estados lógicos, que podem ser revertidos por controle de pH ou ação da temperatura. Estes são chamados de "molecular shuttles" que são como vagões moleculares percorrendo um trilho, no caso o eixo do hóspede 75,76 .…”

Section: Rotaxanos Pseudo-rotaxanos Rolamentos E Chaveadores Molecuunclassified

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Cucurbiturilas

Demets¹

2007

Quím. Nova

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Recebido em 7/8/06; aceito em 9/11/06; publicado na web em 17/7/07 CUCURBITURILS. This review article describes the properties and the main applications of the glicol[n]urils. These compounds are cavitands made of n glycolurilic units arranged in circles, giving rise to extremely symmetric toroidal molecules. The cucurbit [n]urils create this way variable-sized hydrophobic cavities and the glycolurilic carbonyles delimit two portals on these cavities, slightly narrower than their internal radii. Their structure, physical and chemical properties favor the formation of inclusion compounds, and turn them into important building blocks for supramolecular chemistry and nanotechnology.Keywords: cucurbiturils; cucurbitands; inclusion compounds. INTRODUÇÃOAs cucurbiturilas foram sintetizadas pela primeira vez por Behrend e colaboradores 1 em 1905, como resultado da condensação da uréia e do glioxal, formando glicolurila e análogos poliméricos na presença de formaldeído. A tecnologia da época não permitiu uma caracterização inequívoca e a estrutura peculiar destes polímeros só foi elucidada pelo grupo de Mock, 80 anos mais tarde 2 . Pela primeira vez demonstrou-se que os cucurbitandos, outra designação desta família de compostos (abreviados também por CB[n]), eram estruturas cíclicas toroidais, compostas por 6 unidades de glicolurila, ligadas por grupos -CH 2 -em suas aminas de simetria D 6H (Figura 1).A nomenclatura oficial deste composto é complexa* e a sua forma de abóbora deu origem a seu nome, de cucurbita em latim (* segundo a IUPAC, o nome da cucurbit[6]urila ou CB[6] seria: dodecaidro-1H, 4H, 14H, 17H-2, 16:3, 15-dimetano-5H, 6H, 7H, 8H, 9H, 10H, 11H, 12H, 13H, 18H, 19H, 20H, 21H, 22H, 23H, 24H, 25H, 26H-2, 3-4a, 5a, 6a, 7a, 8a, 9a, 10a, 11a, 12a, 13a, 15, 16, 17a, 18a, 19a, 20a, 21a, 22a, 23a, 24a, 2 -3 -5a, 26a -tetracosaazabispentaleno[1''',6''':5'',6'',7'']cicloocta[1'', 2'', 3'':3', 4']pentaleno(1',6':5,6,7)cicloocta(1,2,3-gh:1',2',3'-g'h')cicloocta(1, 2, 3-cd:5, 6, 7-c'd')dipentaleno-1, 4, 6, 8, 10, 12, 14, 17, 19, 21, 23, 25-dodecona).Esta estrutura, além de ser simétrica, possui uma cavidade central hidrofóbica relativamente grande, que é capaz de acomodar espécies variadas para a formação de compostos de inclusão, também chamados de caviplexos, como o fazem outras famílias de cavitandos como as ciclodextrinas ou calixarenos. Na cucurbit[6]urila, existem 12 carbonilas orientadas para fora das cavidades, 6 de cada lado, formando assim dois portais para as cavidades, e conferindo à molé-cula um caráter básico de Lewis. Os métodos mais modernos de análise constataram que não eram formados apenas anéis de 6 membros nas sínteses de cucurbiturilas, mas que outros análogos cíclicos com 5 a 11 unidades glicolurílicas também eram formados durante as sínteses. Os recentes avanços em química orgânica sintética permitiram a elaboração de novas rotas, resultando em rendimentos diferenciados na produção destes homólogos. O maior controle sobre a distribuição dos produtos síntese tornou viável a síntese de CB [7] e ...

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Section: Rotaxanos Pseudo-rotaxanos Rolamentos E Chaveadores Molecuunclassified

Cucurbiturilas

Demets¹

2007

Quím. Nova

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“…[43] An early reported example is the shuttling of CB [6] along a triamine chain. [44] Shuttling of CB [6] was a consequence of changes in pH to deprotonate and protonate the amine groups, which causes CB [6] to unbind and rebind. [44] Pioneering work by Kim and coworkers shows results of applying control over recognition processes by means of photo-and/or electrochemistry.…”

Section: Host-guest Chemistry Of Cucurbit[n]urilsmentioning

confidence: 99%

“…[44] Shuttling of CB [6] was a consequence of changes in pH to deprotonate and protonate the amine groups, which causes CB [6] to unbind and rebind. [44] Pioneering work by Kim and coworkers shows results of applying control over recognition processes by means of photo-and/or electrochemistry. CB [8] has been frequently used for different purposes, such as vesicle formation, stoichiometry control or CB [8]-mediated chemical reactions.…”

Section: Host-guest Chemistry Of Cucurbit[n]urilsmentioning

confidence: 99%

Stimuli‐Responsive Cucurbit[n]uril‐Mediated Host‐Guest Complexes on Surfaces

Wiemann

Jonkheijm

2017

Israel Journal of Chemistry

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Supramolecular functional surfaces are at the heart of many materials and medical applications. Increasing interest can be seen for devising new supramolecular functionalization strategies of surfaces. In this review we place particular emphasis on the use of cucurbit[n]urilmediated host-guest complexation as surface functionalization strategy. The state of the art of cucurbit[n]uril-mediated host-guest complexes on surfaces is reviewed. Cucurbit [n] urils (CB[n]) are able to form strong host-guest complexes with affinities that span several orders of magnitudes up to the regime of the biotin-streptavidin pair and that can be modulated by applying remote stimuli provided suitably sensitive guests were selected. Strategies to fabricate stimuliresponsive surfaces creates versatile supramolecular systems and several applications of these types of surfaces are outlined.

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“…It was Mock and coworkers who also laid the foundation for many lines of applications of cucurbiturils, which are currently intensively pursued. These include pH-responsive fluorescent switches [18] and their use in catalysis. [19][20][21] Examples of rotaxane architectures and polymeric assemblies followed.…”

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The World of Cucurbiturils — From Peculiarity to Commodity

2011

Israel Journal of Chemistry

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More than a century ago, while Robert Behrend ( Figure 1) and his coworkers were investigating acid-catalyzed condensation reactions between glycoluril and formaldehyde, [1] a mysterious white material was the result. The German chemist had unknowingly synthesized the parent cucurbituril, yet recognized that this as-yet-unnamed material could be dissolved in water in the presence of either protons or alkali ions, and easily formed complexes with metal salts and organic dyes.[2] This peculiarity has now matured into an internationally well-recognized area of supramolecular chemistry that is intensively being pursued. While the first synthesis of cucurbituril is, unarguably but in retrospect, Behrends biggest achievement, he was known during his lifetime for the first synthesis of uric acid, [3] for carrying out the first potentiometric titration, [4] and even for an organic name reaction, the Behrend rearrangement. [5] After 75 years of dormancy, investigations by Mock and coworkers in the 1980 s led to the structural elucidation of the white solid as being a discrete macrocyclic pumpkin-shaped hexamer [8] as opposed to an open-chain ladder polymer. They coined the name "cucurbituril" in reflection of the botanical name for pumpkin. Recognition of the structure immediately led to comprehensive investigations of its host-guest inclusion behavior, which also revealed a particularly high affinity towards organic ammonium cations.[9] At present, unique applications of cucurbiturils in diverse areas are rapidly unfolding that will soon render these macrocycles a commodity.Homologues of different sizes, ranging from cucurbit[5]uril to cucurbit[10]uril (Figure 2), as well as equatorially alkylated and hydroxylated derivatives, were isolated and characterized, [10][11][12] showing marked differences in water solubility, guest affinity as well as guest size selectivity, and binding stoichiometry. In particular, the possibility to study these fascinating macrocycles in neutral aqueous solution has attracted much attention since applications in many areas, including biology, are now in sight. Moreover, it has become possible to contrast the inclusion properties and binding strengths of this new class of synthetic host molecules with established macrocyclic receptors, such as cyclodextrins and water-soluble calixarenes. In fact, cucurbiturils are competitive in several respects, such as their low toxicity, [13,14] and far superior in many others, particularly their high chemical stability, large complexation-induced pK a shifts, as well as their tight, selective binding (see articles in this special issue).Initial investigations on cucurbit[6]uril focused on its binding preferences and the determination of the binding constants of its host-guest complexes. [15][16][17] These studies have continued to attract attention also for the larger homologues, driven, among other things, by the exceptional kinetics and thermodynamics of binding. It was Mock and coworkers who also laid the foundation for many lines of applications of cu...

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A cucurbituril-based molecular switch

Abstract: Upon encapsulating the I iga nd PhN H( CH2)6N H( CH&N HP, the nonadecacycl ic molecular receptor cucu rbitu ri I (C36H36N24012) exhibits a bimodal binding pattern contingent upon pH.

Cited by 132 publications

References 11 publications

Cucurbiturilas

Cucurbiturilas

Stimuli‐Responsive Cucurbit[n]uril‐Mediated Host‐Guest Complexes on Surfaces

The World of Cucurbiturils — From Peculiarity to Commodity

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