Group hydroxides

The mass losses for all samples are in a good agreement with values of water and hydroxide group content obtained by chemical analysis (Table 1). Thus, for electrochemical testing of Li- intercalation activity each sample was heated at 350°C to remove all types of bound water. 

ScF3 and LaF3. Both separate and multilayer scandium and lanthanum fluoride films have been grown from nitrates and lanthanum chloride and sodium and ammonium fluorides. XPS analysis revealed that the films were stoichiometric and that the films contained both hydroxide groups and water.129... 

Fig. 11. Thermodynamic functions for the formation of hydroxospecies as a function of the number of contained hydroxide groups (—) least-squares regression. Reproduced with permission from Ref. (85). Copyright 1998, Wiley-VCH Veriag GmbH.

The hammerhead ribozyme and leadzyme belong to the second class of ribozymes. The short extra sequences of the ribozymes form the so-called catalytic loop which acts as the enzyme. There are two likely functions for metal ions in the mechanism of action of hammerhead ribozymes formation of metal hydroxide groups or direct coordination to phosphoryl oxygens. 

The Stober method can be used to form core-shell silica nanoparticles when a presynthesized core is suspended in a water-alcohol mixture. The core can be a silica nanoparticle or other types of nanomaterials [46, 47]. If the core is a silica nanoparticle, before adding silicon alkoxide precursors, the hydroxysilicates hydrolyzed from precursors condense by the hydroxide groups on the surface of the silica cores to form additional layers. If the core is a colloid, surface modification of the core might be necessary. For example, a gold colloid core was modified by poly (vinylpyrrolidone) prior to a silica layer coating [46]. 

A dinuclear Fe(II) centre is bridged by two carboxylate and one hydroxide group. It is thought that the activation of molecular oxygen is a consequence of the ability of the active site to shuttle the FeuFen/ FeIIFeIII/FeIIIFeIn redox changes. 

An unusual and complicated array of heterocycles results from the inclusion of hydroxide moieties into a similar ferf-butylaluminium oxide system to [(f-Bu)A10]8 [50]. In this context, the product which results from the hydrolysis of [(f-Bu)Al(/T3-0)]6 [24] - [(f-Bu)Al]6(/T3-0)4(/r3-0H)4 - is best viewed as comprising an octahedron of aluminium centres each face of which is /X3-capped by either an oxide or a hydroxide group (Fig. 11) [63]. This species was the first to exhibit penta-coordinate Al-centres in an alumoxane context. Moreover, the polyhedral architecture incorporated an interstitial void which, it was suggested, might facilitate the formation of inclusion complexes. The predilection for (AlO) (n = 2) metallocycles does not hold for the tetracyclic array of n = 3 rings displayed by the mixed oxide-hydroxide... 

Replacement of an equatorially bound carboxylate group by a hydroxide group -0.07... 

Mltsulshi et al. described (20) that 4-OH was in the hydrazo form in polar solvents, and azo form in nonpolar solvents. It was suggested that one hydrogen atom of the hydroxide group at the 4-positlon of the naphthalene ring transferred to the 3-positlon of the azo group, and the tautomerism was established between hydrazo form of the keto type and the azo form of the enol type. In this study, we consider that the spectrum with a peak at the 480 nm... 

The oxidation of olefins to carbonyl compounds by palladium (II) ion can be regarded as an addition of a palladium hydroxide group to the olefin followed by a hydrogen shift. Kinetic evidence suggests the following mechanism for the oxidation of ethylene by palladium chloride in aqueous solution containing excess chloride ion 21, 49, 99). 

Finally, even if these criteria are satisfied, there remains the question of whether the product will adhere to form a film or just precipitate homogeneously in the solution. This is the most difficult criterion to answer a priori. The hydroxide and/or oxy groups present on many substrates in aqueous solutions are likely to be quite different in a nonaqueous solvent (depending on whether hydroxide groups are present or not). Another factor that could conceivably explain the general lack of film formation in many organic solvents is the lower Hamaker constant of water compared with many other liquids this means that the interaction between a particle in the solvent and a solid surface will be somewhat more in water than in most other liquids (see Chapter 1, van der Waals forces). From the author s own experience, although slow precipitation can be readily accomplished from nonaqueous solutions, film formation appears to be the exception rather than the rule. The few examples described in the literature are confined to carboxylic acid solvents (see later). 

A number of mixed sulphide/hydroxides have been deposited, mainly in the search for improved window layers for photovoltaic cells (Chap. 9). These are mostly probably mixed-phase films, although in one case, ln(OH)S, experimental evidence suggests true compound formation [46]. Most of these films have been dealt with in previous chapters (see Chap. 4 under ZnS and Chap. 6 under In and Sn sulphides). One study (described from the viewpoint of its properties in photovoltaic cells in Chap. 9) has not been described previously and will be mentioned briefly here. This deals with Zn(0,0H) and Zn(0,0H,S) deposited from Zn-ammine solutions, the latter film from solutions also containing thiourea [47]. It is of interest to note that the Zn(0,0H) films did not deposit on glass but did on both ZnO- and CulnSe2-type substrates. Even after annealing at 300°C, hydroxide groups were still present in those films. 

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