Tube-like compounds

Carbon-based nanotubes (CNTs) have attracted a great deal of attention in the fields of chemistry, physics, and materials science and have been extensively studied since their initial discovery in 1991.36 Much of the excitement in this area of research stems from their unique structures, fundamental electronic and physical properties, and potential applications.37 Inspired by these carbon nanotube studies, coordination chemists have undertaken significant efforts toward the construction of tube-like complexes through metal-ligand coordination.38 1 Examples of silver(I) tubular complexes obtained via assembly reactions of predesigned organic ligands with silver salts are described here.42-44 

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As all the oxygen atoms are already boimd and no water molecule belongs to the ion coordination sphere, there is no structural rearrangement upon heating and the crystal structure remains unchanged upon 500 °C. At last, the optical emissions of doped isostructural compounds (Yi c Rx (btc) with / = Eu, Tb or Dy and x 2%) have been studied. Very efficient red, green and blue emission respectively have been observed. As a concluding remark, one should notice that this anhydrous phase is different from the one obtained by de-hydration of the tube-like compound previously described. 

Curved structures are not only limited to carbon and the dichalcogenides of Mo and W. Perhaps the most well-known example of a tube-like structure with diameters in the nm range is formed by the asbestos mineral (chrysotil) whose fibrous characteristics are determined by the tubular structure of the fused tetrahedral and octahedral layers. The synthesis of meso-porous silica with well-defined pores in the 2-20 nm range was reported by Beck and Kresge.6 The synthetic strategy involved the self-assembly of liquid crystalline templates. The pore size in zeolitic and other inorganic porous solids is varied by a suitable choice of the template. However, in contrast to the synthesis of porous compounds, the synthesis of nanotubes is somewhat more difficult. 

Harada linked the threaded a-cyclodextrines of poly(ethyleneoxide)/a-cyclodex-trine-rotaxanes with epichlorhydrin. After removing the poly(ethyleneoxide)-template, he obtained tube-like carbohydrate compounds [376], Similar attempts have also been reported with P- and y-CD [378,384]. 

Pyrogenic reactions result from contamination of antivenom by endotoxin-like compounds. High fever develops 1-2 hours after treatment and is associated with rigors, followed by vasodilatation and a fall in blood pressure. Febrile convulsions can occur in children. Patients should be cooled and given antipyretic drugs by mouth, powdered and washed down a nasogastric tube, or by suppository. 

The two kidneys are situated at the back of the abdomen on either side of the vertebral column. They carry out many functions in the body, the most important of which is the production of urine and the excretion from the body of low-molecular-weight (relative molecular mass less than 68 000 daltons) water-soluble compounds, including many drugs. Each kidney contains approximately one million urine-producing structures called nephrons. The nephron in turn consists of a bundle of blood capillaries termed a glomerulus, which functions as a very efficient filter to remove waste products and impurities from the blood, and a long tube-like structure called a tubule (see Figure 2.10). 

Noncovalent interactions with belt- or tube-like host molecules might also be suitable to a separation of carbon nanotubes by diameter. Cyclodextrines or beltshaped aromatic compounds could be named as examples here. They may not have proven their applicability as selective complexing agent yet, but considering their geometry reveals favorable dispositions for a discriminative interaction with certain nanotubes. Supramolecular arrangements with carbon nanotubes are also discussed in Section 3.5.7. 

It can also be noticed that the third componnd described, namely Er(btc)(H20)s-3.5(H20), presents a psendo 3D stracture via hydrogen bonds. However it is not a microporous solid precursor. Indeed, when dehydrated this compound reversibly rearrange leading successively to the honeycomb-like compound and then to the hexagonal-tube like structure. This last compound finally leads to an anhydrons compound which unfortunately has not yet... 

Carbon is the atom of the periodic table that forms the greatest number of compounds. Pure carbon may also form large molecules and crystallize into a number of allotropic forms, such as 35, C o, and C70 from the large fullerene family, nano tubes (a tube-like form of a fullerene), graphite, and diamond. These substances have widely different conductivity properties. 

Hydrothermal or solvothermal reactions are also an important method for the synthesis of unconventional zeolite-like compounds. The reagents are usually dissolved or dispersed in water and then heat-treated at elevated temperatures in an autoclave. For reactions at moderate temperatures up to about 250 °C the autoclaves are normally lined with Teflon. If higher reaction temperatures are desired, the reactions are, for instance, carried out in stainless steel or gold tubes. However, in favorable cases, the use of higher temperatures might not even be necessary. The products sometimes just precipitate from solution at room temperature. 

Complex compounds of lithium and heavy metal oxides as nickel oxide and cobalt oxide are working more effectively than the lithium/manganese oxide spinel which incorporates lithium ions into its tube like voids whereas the former with their layered structure take up and release lithium ions more easily. 

Fig. 5 Evolving self-assembly of compound 3 (10 M, wateriTHF = 4 1). Cryo-TEM images of (a) short curved fibers (b) longer curved fibers and (c) long thicker tube-like fibers, where the molecular helical 3-nm-thick fibers (a, b) are converted into straight tubular4.5-nm fibers. In good agreement with the molecular models (3.2 and 4.7 nm fiber widths). The assembly development can be stopped by the addition of water ( wateriTHF = 95 5, v/v) [38]...

The synthesis of quaternary thiospinels, like Ag2FeSn3Sg [5], Ag2MnSn3Sg [6], and Cu2NiSn3Sg [7], has been achieved by reacting metals along with sulfur powder in an evacuated silica tube. Pure phases of these compounds were obtained at 750 °C, 670 °C and 750 °C respectively. 

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