Group IV Phosphates

Acid salts of Group IV phosphates and arsenates have layered structures with interlayer distances large enough to accommodate a number of ions. The size of the opening to the cavities of the acid salts with the same layered structure is dependent upon the particular composition. Table 5 lists the correlation between ion sieve effects and the interlayer distance of various acid salts [l40j. 

MELS (molecularly engineered layers) (see also organically pillared group IV phosphates ) 293... 

Group (IV) metal phosphates and phosphonates, transition metal oxides (titanates, silicates, niobates, etc.), layered oxides, and double hydroxides (aluminum, magnesium, iron, etc.) are some of the inorganic compounds used as layered host ma-... 

A linear relationship has been demonstrated by Clayden and Pugh (1998) between the quadrupole coupling constant Xq and the ionic radius r (in nm) of the M ions in the small group of sodium metal(IV) phosphates NaM2(P04)3 where M = Sn, Ge, Ti and Zr. The two resolvable Na sites of NaSn2(P04)3 straddle the line for these compounds, defined by ... 

Mesoporous titanium(IV) phosphates with cationic framework topologies obtained by using both cationic and anionic surfactants are reported.[243] They show anion-exchange capacity due to the framework phosphonium cation, and cation-exchange capacity due to defective P-OH groups. 

We thank the Organic Chemistry Group at Widnes R D. We also wish to thank our university collaborators, particularly Professor Bob Johnstone, and Dr. Preciosa Pires (Liverpool University, metal(IV) phosphates), Professor Bill Griffith, and Dr. Melanie Gresley (Imperial College, immobilized polyoxometalates). Professor Roger Sheldon, and Dr. Jihad Dakka (Delft University, chromium silicalite). 

Amino-5-iodo-2, 5 -dideoxyuridine [56045-73-9] (13) C9H12IN304, was synthesized in 1975 (27) and was found effective against herpes keratitis in rabbits (28). This compound is markedly less cytotoxic than IdU, indicating that it may have a safer and more specific mode of antiviral activity. A potential limitation of this group of nucleosides is their specificity, for they fail to inhibit all strains of herpes viruses. The specific antiviral activity of (13) is considered to be a result of the incorporation of the 5 -IV-phosphate into both viral and host DNA in infected cells, but not into the DNA of normal cells. Phosphorylation of (13) occurs only in herpes virus-infected cells, brought about by a virus-induced thymidine kinase (29). 

Tetravalent metals may also be bonded by XO4 and/or to R—XO3 groups so as to build up a layered structure different from the a-structure. These compounds are usually called y-layered M(IV) phosphates. Unfortunately, single crystals large enough for X-ray determination have not been obtained and the structure of y-compounds is still unknown. Recent... 

Clearfield, A. (1988) Recent Advances in Pillared Clap and Group IV Metal Phosphates. NATOASl Ser., Sen C 231, 271. 

The filtrate obtained after the Group III metal ions have precipitated contains the alkali metal ions and the alkaline earth ions. The Analytical Group IV ions, Ba, Ca, Mg, and Sr, are precipitated as carbonates or phosphates by adding (NH4)2C03 or (NH4)2HP04. The filtrate from this separation contains the Analytical Group V ions, and Na. ... 

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