Complexes aquatic

Whereas ligand exchange reactions in aquated complexes of Li+ have been studied extensively, the corresponding ammine complexes have so far received very little attention. The interaction of an ammonia molecule (belonging to the second coordination sphere) with [Li(NH3)4]+ is weaker than in the... 

Zirconium is the principal FP to arise in oxidation state (IV). Where Zircaloy clad fuel is involved, nonradioactive zirconium isotopes may also be present from fuel can residues. As with ruthenium, there may be a variety of nitrato complexes present in the solution including the aquated complexes Zr(N03)s where x = 1-6, and hydroxy nitrato complexes. However, species containing ZrO " " are not expected to be present since this ion is unstable in aqueous media and is rapidly hydrated to Zr(OH)2. The extraction chemistry is further complicated by the formation of inextractable polymeric species when the Zr" concentration exceeds ca. 10 M. An example of such oligomerization is afforded by the [Zr(0H)2(H20)4]4 ion which contains four Zr ions in a square arrangement linked by two /u-OH ligands on each square edge. Four water molecules complete the Zr coordination sphere in an approximately D2d dodecahedral geometry. 

The second type is typical of interaction between H O and ions. When they meet, water dipoles orient in the electrostatic field of ions, pulled in by the end with the opposite charge and become less mobile. This way form super-molecule associations of the aquatic complex type - [ionCH O) ]. Such process is called hydration, and formed complexes - hydrates. Diluted solutions are dominated by saturated aquatic complexes where each ion is surrounded by water molecules, for instance, Cu[H20]g, Ni[H20]g. Even ions of hydrogen and hydroxyl OH" do not exist in water... 

There are two ways to approach the hydration nature the thermodynamic and kinetic. The thermodynamic approach treats hydration as a reversible process of joining H O dipoles with the formation of peculiar aquatic complexes with a set coordination number. Such an approach is handy when studying the thermodynamics of chemical processes, in particular complex formation, and will be used in the sections dealing with these processes. The kinetic approach was introduced by O.Ya. Samoylov (1921-1980), who proposed a first model of clathrate type of water structure as early as 1946. 

Polar components are mostly ions and cannot be separated from the solution in pine form. They have an electrical field whose influence is not limited by specific boundaries. Even in diluted solutions dissociated ions are capable of forming aquatic complexes and participate in the formation and subsequent disordered hydration. In contrast, in brines they create complexes, which are so close to one another that it is difficult to separate one from the other. 

As noted above, cw-DDP enters cells by diffusion where it is converted to an active form. This is due to the lower intracellular chloride concentration, which promotes ligand exchange of chloride for water and thus formation of the active aquated complex. Thus, the platinum-containing complex should be neutral to enter the cell and labile chloride groups need to be present to form the active species widiin the cell. The antineoplastic activity of cw-DDP appears to be related to its interaction with DNA nucleotides, as a monoaquo species. The monohydrated complex reacts with the DNA nucleotide, forming intra/interstrand crosslinks. Of the four nucleic acid bases, cw-DDP has been shown to preferentially associate with guanine. The most common are intrastrand crosslinks between adjacent guanines. ... 

Other Aqueous Systems. Several reports have appeared where bidentate ligands have been attached to aluminum either as tris complexes or as partially aquated complexes. Of particular interest is the use of Al to study the macrocyclic... 

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