Cucurbit[10]uril

Melamine diamine 1 is able to displace CB[5] from the CB[10].CB[5] complex resulting in CB[10].12 and precipitated CB[5].1. We were able to isolate free CB[10] by treatment of CB[10].1 with acetic anhydride followed by washing with MeOH, DMSO, and water. The spacious cavity of CB[10] is able to complex large guests, including a cationic calix[4]arene derivative in its 1,3-alternate form (CB[10].1,3-alt-3). The addition of adamantane carboxylic acid (4) to CB[10].3 triggers a conformational change during the formation of termolecular complex CB[10].cone-3.4.     

A clipped [3]rotaxane derived from bis-nor-seco-cucurbit[10]uril

This paper describes the synthesis of host 1 by the double bridging reaction of bis-ns-CB[10] with 2 under acidic conditions. Host 1 functions as a double cavity host for aliphatic and aromatic ammonium ions (3-17) in water. Conducting the bridging reaction in the presence of guest 4 delivers [3]rotaxane 1·4(2) by a clipping process.     

Sequential Formation of Heteroternary Cucurbit[10]uril (CB[10]) Complexes

The globular and monocationic guest molecule trimethyl-azaphosphatrane ( AZAP , a protonated Verkade superbase) was shown to form a host:guest 1 : 1 complex with the cucurbit[10]uril (CB[10]) macrocycle in water. Molecular dynamics calculations showed that CB[10] adopts an 8-shape with AZAP occupying the majority of the internal space, CB[10] contracting around AZAP and leaving a significant part of the cavity unoccupied. This residual space was used to co-include planar and monocationic co-guest ( CG ) molecules, affording heteroternary CB[10]⋅ AZAP ⋅ CG complexes potentially opening new perspectives in supramolecular chemistry.     

Photodimerization of azaanthracene derivatives mediated by cucurbit[10]uril

Challenges of achieving efficient photodimerization of azaanthracene derivatives remain due to the low selectivity and slow reaction rate. In this paper, cucurbit[10]uril (CB[10]), with the largest rigid and hydrophobic cavity among CB[n]s, was used to affect the photodimerization reaction of four water-soluble 1-(2-)substituted azaanthracene derivatives (1-4). It revealed that 1-4 could form 1:2 host-guest complexes with CB[10] in aqueous solution. Irradiation of 1 in the presence of 0.5 equiv. of CB[10] selectively produced a head-to-tail (anti-HT) photodimer product. As for 2-4, CB[10] acted as a nanoreactor accelerating their photodimerization reaction in water. Our results suggest that photodimerization of azaanthracene derivatives could be promoted by the CB[10]-based host-guest strategy with high efficiency and selectivity.     

An indolocarbazole-bridged macrocyclic porphyrin dimer having homotropic allosterism with inhibitory control

A macrocyclic host, a pair of zinc porphyrins bridged by two anion-acceptable indolocarbazole moieties, has shown strong positive homotropic allosterism upon anionic guest bindings with an inhibitory control mechanism by DABCO addition.     

Cucurbit[5]uril, Decamethylcucurbit[5]uril and Cucurbit[6]uril. Synthesis, Solubility and Amine Complex Formation

A simple way to prepare cucurbit[5]uril is described. The macrocycles of the cucurbituril type are nearly insoluble in water. The solubilities of cucurbit[5]uril, decamethylcucurbit[5]uril and cucurbit[6]uril in hydrochloric acid, formic acid and acetic acid of different concentrations have been investigated. Due to the formation of complexes between cucurbit[n]urils and protons the solubility increases in aqueous acids. The macrocyclic ligands are able to form complexes with several organic compounds. Thus, the complex formation of the cucurbituril macrocycles with different amines has beenstudied by means of calorimetric titrations. The reaction enthalpy gives noevidence of the formation of inclusion or exclusion complexes. ¹H-NMR measurements show that in the case of cucurbit[5]uril and cucurbit[6]uril the organic guest compound is included within the hydrophobic cavity. Decamethylcucurbit[5]uril forms only exclusion complexes with organicamines. This was confirmed by the crystal structure of the decamethylcucurbit[5]uril-1,6-diaminohexane complex.     

Cucurbit[8]uril rotaxanes

The synthesis of [2]rotaxanes, each comprising a viologen core threaded through a cucurbit[8]uril (Q8, Figure 1) macrocycle and stoppered by tetraphenylmethane groups, and their binding to second guests as inclusion complexes in organic and aqueous media are described. Stoppering was observed to have little effect on binding. Chemical modification of the threaded guest was used to control solubility and binding characteristics, thus demonstrating a novel approach to making artificial receptors with readily modifiable properties.     

A hemicyanine and cucurbit[n]uril inclusion complex: competitive guest binding of cucurbit[7]uril and cucurbit[8]uril

The interaction between the hemicyanine indole derivative H and the cucubit[n]urils Q[7] and Q[8] has been studied using ¹H NMR and UV spectroscopy as well as by fluorescence experiments. Competitive studies on the inclusion of H by Q[7] and Q[8] have also been conducted, and reveal that on changing the size of the Q[n] cavity, the binding behaviour can be very different.     

Cucurbit[n]uril analogues

[structure: see text] Cucurbits come in a variety of sizes, shapes, and colors. We present a building block approach that allows the tailor-made synthesis of CB[5], CB[6], and CB[7] analogues whose sizes, shapes, and colors differ from those of the known CB[n].     

Binding behaviors of para-dicyclohexanocucurbit[6]uril and meta-tricyclohexanocucurbit[6]uril with dialkyl viologens

The binding behaviours of para-dicyclohexanocucurbit[6]uril (Cy₂Q[6]) and meta-tricyclohexanocucurbit[6]uril (Cy₃Q[6]) with a series of dialkyl viologens (MV²⁺, EV²⁺, PV²⁺, BV²⁺, FV²⁺ and HV²⁺) have been investigated by various methods. In the aqueous solution, ¹H NMR spectra suggest that the alkyl chains are more favourably encapsulated into the hydrophobic cavities of both hosts than the aromatic rings. Cyclic voltammograms (CV) curves show that the Cy₂Q[6] or Cy₃Q[6] bind the charged viologens more strongly than the reduced viologens. Isothermal titration calorimetry (ITC) data reveal that the binding processes of both hosts with viologens are enthalpic driven. In the solid state, the PV²⁺, BV²⁺ guests and two Cy₃Q[6] hosts generated dumbbell-shaped structures, with two Cy₃Q[6] hosts residing over two terminal alkyl chains of the guests.     

Probing guest compounds enabling the facile isolation of cucurbit[10]uril

A large set of commercially available amino compounds were assessed toward binding with cucurbit[10]uril(CB[10]),with the purpose of facilitating the isolation of pure CB[10].We found that the addition of a specific guest into a relevant mixture of CB[n]allowed the displacement of CB[5]from CB[10]?CB[5].Subsequent washing of the resulting(G=guest)with dimethyl sulfoxide(DMSO),enabled to get pure CB[10]in a facile and highly efficient way.     

A study of binding interactions between terpyridine derivatives and cucurbit[10]uril

The binding interactions of a series of 2,2′:6′,2″-terpyridine (TPY) derivatives and their metal complexes with cucurbit[10]uril (CB[10]) were investigated by ¹H NMR, UV/Vis, emission spectroscopy, and ESI mass spectrometry. ¹H NMR titrations revealed CB[10] could encapsulate methylated TPY (MTPY), and the binding ratio between guest MTPY and host was 1:1 and 2:1 via ESI-MS characterization. For the transition metal complexes composed of Fe(II) or Ru(II) or Rh(III) and TPY derivatives, the octahedral TPY?metal?TPY core can be included in the cavity of CB[10]. Three binding modes (1:1, 1:2 and 1:3) have been detected for the binding of the metal?MPTY complexes with CB[10] by ESI-MS.