Simultaneous encapsulation

Rebek, J., Jr. Simultaneous encapsulation Molecnles held at close range. Angew. Chem. Int. Ed. 2005, 44, 2068-2078. 

The respective association constants of the latter anion to free 376 is only 10 M 1 while for the self-assembled complex it is equal to 2.5 104 M 1 [39]. Kubik and Goddard obtained a cyclic pseudopeptide ditopic receptor 378 for the simultaneous complexation of cations and anions [40]. Simultaneous encapsulation of N03 and PF6 ions by a highly charged (+12) anion receptor 379 was achieved by Schnebeck and coworkers [41]. By coordinating of 2,4,6-tris[(4-pyridyl)methylsulfa nyl]-l,3,5-triazine 380 with Ag, Hong and coworkers obtained nanosized tubes (Fig.7.8.1) that could host solvent and anionic molecules [42]. 

The encapsulated nanotubes produced in dichloroethane are shown in Fig. 9. Their morphology and the volume structure completely correspond to the mechanism of the fast formation of a nanotube and its simultaneous encapsulation proposed in paper [6],... 

Rebek J (2005) Simultaneous encapsulation molecules held at close range. Angew Chem Int Ed 44 2068... 

The procedure of freeze-drying in the presence of mannitol has proven to be a superior method for simultaneous encapsulation... 

Molecular capsules are structurally elaborated receptors that completely surround the hosted molecule(s). Encapsulation based on covalent bonds yields permanent arrangements of molecules-within-molecules. Reversible encapsulation, on the other hand, is based on self-assembling through formation of weak supramolecular bonds and offers possibilities for a dynamic in out exchange of encapsulated molecules. Most of the dimeric capsules developed by Rebek and his group are obtained through reversible self-assembly of resorcinarene subunits. When simultaneously encapsulated in the cylindri-cally shaped inner space of these capsules, two reactant molecules are temporarily isolated from others in solution and display reactivity features different from those in bulk solution. The matter has been extensively reviewed,and will not be discussed here. 

J. Rebek Jr., Simultaneous encapsulation molecules held at close range, Angew. Chem. Int. Ed., 2005, 44, 2068-2078 b) R. CacciapagUa, S. Di Stefano, L. Mandohni, Effective molarity in supramolecular catalysis of two-substrate reactions, Acc. Chem. Res., 2004, 37, 113-122. 

Variations in monomer and catalyst stoichiometry, reaction time or temperature all proved unsuccessful in triggering the formation of the dipolar cycloaddition product. The use of excess cucurbituril led only to quantitative isolation of the pseudorotaxanes derived from 1 and 2 (Fig. 1.38). We speculated that our initial monomer design must have been flawed. The choice of a six-carbon spacer to maximize recognition of the monomer by cucurbituril may be the cause of the catalytic inhibition. We hypothesized that the pseudorotaxanes derived from cucurbituril and monomers 1 and 2 must form much faster than any possible ternary complex and that the essentially perfect fit of each monomer inside cucurbituril would prevent the simultaneous encapsulation of alkyne and azide moieties by a third cucurbituril with the correct conformation required for catalysis. 

In a different approach, the [Mn(salhd)Cl] complex was immobilised onto an Al-WYO PILC by simultaneous encapsulation of the complex and pillaring of the clay with aluminium polyoxocations. Two distinct routes were followed method A - simultaneous pillaring/encapsulation, with addition of the [Mn (saZen)X] complex after the oligomeric species formation, and method B - simultaneous pillaring/encapsulation, with addition of the complex to the initial clay dispersion. The heterogeneous catalysts... 

A farther step was veiy recently realized through the design of triggered nanoreactors, which were able to start in situ enzymatic reactions in the presence of stimuli in their environment. Such nanoreactors were based on the simultaneous encapsulation of an enzyme and insertion in the polymer-some membrane of a chemically engineered channel porin, which had a pH-sensitive cap. Upon a pH change in the environment of the nanoreactor, the molecular cap was released, and the membrane allowed transport of sub-strates/products, which then started the in situ enzymatic reaction (Figure 6.6). 

One involves the simultaneous encapsulation of the diene and dienophile components within the cyclodextrin cavity, overcoming the intrinsic entropic barrier associated with bringing these two reactive centers together. This was, in fact, the same argument put forth by Breslow to explain the effect of cyclodextrins on analogous intermolecular Diels-Alder reactions. Alternatively, one could also imagine encapsulation of the dithiane moiety by the cyclodextrin. Such complexation might also accelerate the reaction by... 

Gindy, M.E., Panagiotopoulos, A.Z., and Prud homme, R. (2008) Composite block copolymer stabilized nanoparticles simultaneous encapsulation of organic actives and inorganic nanostructures. Langmuir, 24,83 90. 

The capsules 483 and 488 are reported in [11] to simultaneously encapsulate ortto-quinones 253 and 254 and an adamantane derivative 255, thus giving heteroguest 1 1 1 cage complexes by... 

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