Zirconium phosphate binding

An example of the modular preparation of the cyclophane 3 from the substituted bipyridine 2 and a general tripeptide 1 is shown in Scheme 3-3. The host molecule 3 contains a pre-organized binding pocket. The overall basicity of such molecules also facilitates their intercalation within the lamellas of acidic zirconium phosphate, thus making this chemistry well suited for the desired application. 

The Lewis acid of zirconia can be blocked by other than fluoride. The effectiveness of the blocking of the Lewis acid sites should be related to the strength of the interaction between the Lewis base used and the zirconium ion coordination site. Blackwell and Carr have developed the relative eluotropic strength of a number of Lewis bases in terms of their ability to elute a wide variety of benzoic acid derivatives. Phosphate ranks at the top of the elution series. It brought about elution of the benzoic acid derivatives in the column dead volume. This proves that phosphate binds strongly to the surface of zirconia. The strong affinity of zirconia for phosphate suggested that a phosphate modification of the surface should be a reasonable approach. 

Adsorption and binding behavior of 9-anthracenemethylammonium ions (abbreviated as AMAC) and P4N on zirconium phosphate in the presence of butylamine hydrochloride has been studied (117,118). AMAC tends to aggregate while P4N + gives monomer emission at low surface covCTage. Excimer formation of P4N+ depends on phosphate concentration, additives, and the type of probe. However, the reason for differences in the binding behavior of AMAC and P4N+ has not been clarified. 

Prompt administration of polymeric phosphates have also been successful in increasing plutonium excretion from laboratory animals73). Hexametaphosphate was found to reduce bone absorption of plutonium by a factor of three, but this was accompanied by an increase in the liver burden of plutonium74). Thus, it seems likely that plutonium and polymeric phosphates form colloids that behave similarly to those formed with zirconium, except that the phosphates are more toxic. Alternatively, phosphate groups may bind to bone. Pretreatment with ethane-1-hydroxy-1,1-diphosphoric acid or dichloromethylenediphosphoric acid inhibited the mineralization and growth of bone as well as the skeletal uptake of plutonium75). 

Binding of tetracationic porphyrins on layered antimony hydrogen phosphate and zirconium hydrogen phosphate (a-ZrP) have been reported by Thompson and coworkers. Both monolayer and bilayer guest structures have been pre-... 

---