Compounds inner-cavity

One of the exciting results to come out of heterogeneous catalysis research since the early 1980s is the discovery and development of catalysts that employ hydrogen peroxide to selectively oxidize organic compounds at low temperatures in the liquid phase. These catalysts are based on titanium, and the important discovery was a way to isolate titanium in framework locations of the inner cavities of zeolites (molecular sieves). Thus, mild oxidations may be run in water or water-soluble solvents. Practicing organic chemists now have a way to catalytically oxidize benzene to phenols alkanes to alcohols and ketones primary alcohols to aldehydes, acids, esters, and acetals secondary alcohols to ketones primary amines to oximes secondary amines to hydroxyl-amines and tertiary amines to amine oxides. 

Bicyclic structures of cell type 435, named by J.M. Lehn as kryptandform extremely stable complexes, known as kryptates, with various metal ions, hiding them in an inner cavity. Such compounds have an important role in modern supra-molecular chemistry [268,581],... 

Fullerenes may incorporate guests in their inner cavity, these compounds are called endofullerenes. 

As a new type of electron relay, which is able to penetrate lipid membranes, we tested menaquinone (MQ, Fig. 7). Compounds of this type were not utilized earlier for artificial vesicle-based systems. However, these mimick the functioning of the Z-scheme of natural plant photosynthesis (see Figs 9 and 12). Indeed, the activity of MQ in the redox processes in a lipid bilayer membrane was revealed. However, the quantum yield of the transmembrane electron transfer from a CdS nanoparticle in the inner cavity to a CdS nanoparticle on the outer membrane surface with the participation of MQ appeared to be very low and did not exceed 0.2-0.4%. 

Sanders and coworkers have developed syntheses of rather rigid cyclic oligoporphyrins (porphyrin-linker), (n = 2 4) by catalytic-coupling reactions of acetylene derivatives with copper salts. In particular, incorporation of metal ions into cyclic porphyrin oligomers provides the multi-interaction sites necessary to tightly bind heterocyclic compounds in the inner cavity (see section IV).Rigidity of host molecules is controlled by the structure of the linkage moieties. 

The ability of cyclodextrins to give inclusion or "host-guest" complexes by insertion of various organic and inorganic molecules into their hydrophobic cavity is well-known. But these cavities are remarkably rigid. We have produced a crown ether-like compound starting from beta-cyclodextrin, in which the inner cavity is enlarged and more flexible. 

Dendrimers have an architecture which is intrinsically accessible, because their branched structure allows the passage of substfates and products. In the case of PICsomes, the use of polyelectrolytes, which self-assemble into intrinsically porous systems, favors accessibility to the inner cavity where the active compounds are located [25]. Their membranes are permeable to small molecules, such as Tokyo-Green- 3-galactoside, while encapsulated active biomacromolecules, such as trypsin, cannot escape from the vesicular assemblies [25]. In the case of LbL capsules, permeabiUzation of the shell is tuned by its polymer composition, thickness, solvent, pH, or ionic strength [88,89]. 

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