Polyammoniums

Other types of complexons for polyanions (e.g. polycarboxylates and phosphates) are linear ligands with polyguanidinium cations or polyammonium cations as functional groups 33). 

Macrocyclic polyammonium cations containing more than one proton within the macrocyclic cavity have several unique features ... 

If electrostatic interactions play a major role in the strength of anion binding, then it is natural to expect that the higher the polyammonium cation charge is the stronger the affinity for anions will be. This was found to be case with [24]aneN6 and [32]aneNg which possess 6 and 8 protons, respectively, at pH 7 (see Table 4)46). 

Polyammonium-containing ligands, 24 44 Polyammonium macropolycycles, 76 780 Polyampholytes, 20 475 479 solution properties of, 20 479 synthesis of, 20 477- 478 Poly(anhydrides), bioresorbable polymers, 3 740... 

Notes. (1)Tpypor = tetrapyridlporphyrin pipz = piperazine H5hpdta = 2-hydroxypropane-1,3-di-amine-A/,A/,A/, /V"-tetraaceticacid organic polyammonium cation = tris[2-(trimethylammonium)ethyl]-1,3,5-benzenetricar-boxylate 1,3,5-tris[4-(A/,A/,A/-trimethylammoniumethylcarboxyl)phenyl]benzene DODA = dimethyl dioctade-cylammonium. 

For an excellent overview of the great variation achievable in the design of polyammonium receptors, seeF. P. Schmidtchen, Nachr. Chem., Tech. Lab. 8, 10(1988). 

Anotlier example of dendritic POM complexes used as recoverable oxidation catalysts was reported by Plault et al. (SS). A series of ionic polyammonium dend-rimers containing between 1 and 6 POM units were prepared and used to catalyze the epoxidation of cyclooctene in a biphasic water/CDCls system. A comparison of the homogeneous mono-, bis-, tris-, and tetra(POM) catalysts indicated that there was no dendritic effect on the reaction kinetics within this series. However, a dendritic effect was found in the recovery of the catalysts. The dendritic catalysts were precipitated from the organic phase by addition of pentane. The recovery of the tri-and tetra-(POM) catalysts was easier (80—85% and 96%, respectively) than that of the mono(POM) catalyst. 

Crystalline polyammonium catena-polyphosphate, (NH4) H2P 03 + 1, has been prepared by heating urea and monoammonium orthophosphate under ammonia vapor for 16 hours,1 by ammoniation of superphosphoric acid,2 by thermal condensation of urea phosphate,3 and by heating various ammonium phosphates in a current of ammonia.4,5 The procedure given below, in which crude ammonium tetrametaphosphate is reorganized and condensed to a long-chain polymer in a stream of ammonia, is straightforward and permits the use of common laboratory equipment and supplies. 

The charge is conveniently heated in a 1-L resin reaction vessel equipped with a heating mantle or in a small oven a larger oven may be used if the ammonia is passed directly over the charge. The product should be cooled below 150° under ammonia to avoid deammoniation in handling. The product weighs 32.3 g and is a crystalline solid with the optical, X-ray powder diffraction pattern, and infrared absorption pattern reported for form I polyammonium catena-polyphosphate.2,6 Anal. Calcd. for (NH4) H2P 03 +i with n = 50 N, 14.38 P, 31.81. Found N, 14.4 P, 31.8. 

Form I polyammonium catena-polyphosphate contains the shortest long-chain anions of several polymorphic forms having the same chemical composition.1 It is slightly soluble in water and gives a cloudy, viscous solution. The solubility increases with the quantity of solid phase present the apparent solubility of the pure compound at 25° has been estimated to be 0.15 g per 100 g of water.1 The compound is more soluble in hot water or in the presence of other dissolved... 

The pH dependence of many anions may cause problems in designing an appropriate host. For example, a receptor based upon polyammonium moieties may not be sufficiently protonated in the pH region where the anion is present in the desired form (vide infra). 

In a related study (78CC934,79HCA2763) Lehn and coworkers incorporated guanidinium groups into macrocycles (e.g. 29). The resulting polyguanidium salts form stable complexes in water with phosphate and carboxylate anions. Unlike polyammonium anion receptors, these species remain protonated over a wide pH range and hold considerable potential in the development of anion-selective electrodes. 

As in Sect. 2, the early works in this field will only be briefly summarized. Highly charged polyazoniamacro(oligo)cycles and guanidinium crowns bind phosphates and nucleotides via electrostatic interactions [1,65], and polyammonium cations, like spermine, are generally known to associate with the phosphate backbone of RNA and DNA strands [66]. 

Figure 11 Stability constants for complexes of polyammonium macrocycles with dicarboxylate substrates 02C(CH2)m-C02-. a = [24]N6 6HC1 (72a) O = [32]N6 6HC1 (72b) - [38]N6 6HC1 (72c)...

Metal ion complexes ([M(CN)6]"- M = Fe, Ru, n = 3,4) can also be incorporated into certain macromonocyclic polyammonium ligands forming complexes of complexes , i.e. supercom-... 

Multidentate polyaza and mixed polyaza-polyoxa macrocycles in their polyammonium form complex a variety of anions. Complexation ability is, as anticipated, related to macrocyclic ring size, macrocyclic topology and the relation of these factors to the substrate to be complexed. Polyammonium macromonocydes of various ring sizes and binding subunits complex polycarboxylate... 

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