Triphosphates anion, structure

Proof for the structure of the triphosphate anion comes from its composition and the cryoscopic molecular weight in molten Glauber s salt [values found, 372 (19) and 364 (317) calculated, 367.9]. Assuming that phosphorus has a coordination number of four with respect to oxygen, the anion structure can only be represented by the formula... 

Fig. 4. Structure of triphosphate anion in the two crystalline forms of Na6P30i( (I and II), according to Corbridge 66).

On the other hand, linear polyphosphates give a series of P resonance peaks, each one associated with P atoms in different environments. The triphosphate anion (14.24b) will, for example, produce two such peaks, one due to end P atoms and one dne to the middle P atom (additional fine structure arising from spin-spin conpling may also be observed). Adenosine triphosphate, ATP (10.102) produces three resonance peaks corresponding to a, P and yP atoms, each of which has a different environment. 

In addition, Pauling and Sherman (222) had proposed a ring structure for the anion of aluminium tetrametaphosphate on the basis of a crystal structure determination. The triphosphate NaBP3Oi0 must, then, have the chain structure already proposed by Schwarz (263), for Rudy and Schloesser (250) showed that the acid corresponding to the triphosphate has three strongly and two weakly acidic OH groups with the weakly acidic groups... 

The tetrametaphosphate anion is transformed into the amidotetraphos-phate, (P4O12NH2)5 , by concentrated ammonia solution just as the anion ring of trimetaphosphate is cleaved by ammonia to amidotriphosphate. Acidification of the solution results in partial reconversion to the tetrametaphosphate anion, but there is also partial hydrolysis to NH4+ and tetraphosphate ions as well as to amidomonophosphate and triphosphate ions, with simultaneous formation of trimetaphosphate (800). A complete structure determination has been made for ammonium tetrametaphosphate (1) from which the cyclic structure of the anion is evident (245). The diacid salt Na2H2(P40i2) (108) (see Section V,A) is also undoubtedly a tetrametaphosphate (150) (for structural data, see Section IV,E,3). 

This formula also corresponds with the fact that dissociation is strong in three and weak in two of the five H+ ions in triphosphoric acid (250). The correctness of the structural formula is also supported by the quantitative formation of triphosphate from trimetaphosphate on cleaving the anion ring with strong alkali (90, 311). Final proof for the structure of the tri-... 

Fitting the macrocyclic polyamine 38 with a side chain bearing a 9-aminoacridine group yields a coreceptor capable of both anion binding, via the polyammonium subunit, and stacking interaction via the intercalating dye. It interacts with both the triphosphate and the adenine groups of ATP and provides in addition a catalytic site for its hydrolysis (see structure 82 and Section 5.2) [4.27]. 

Sodium triphosphate exists as a hexahydrate, Na5P30io-6H20, and in two anhydrous forms, known often as phase F and phase IF. The crystal structures of these anhydrous forms (with which the author was involved) [34,35] are shown in Figure 5.16 and the dimensions of the anion, as found in phase II, are indicated below. 

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