Calixarene phosphonates

This review groups the information published on degradation of the main families of extractants studied in the frame of long-lived minor-actinide and fission-product recovery (1-4) (see Chapter 1) alkyl-phosphorus compounds (phosphates, phosphonic acids, bifunctional compounds like CMPO), amide compounds (dialkyl-amides, malonamides, and diglycolamides), N-donor compounds, and macrocycles like crown ethers and calixarenes (Table 8.1). The multicomponent systems based on the chlorinated cobalt dicarbollide process have not been considered. 

The extractant s stability can be improved if the selected diluent has a lower ionization potential than the extractant, like aromatic compounds (183). This protective effect has been observed for numerous extractants alkyl phosphates, alkyl phosphonates, amides, and calixarenes (25, 39, 68, 84,... 

Phosphine Chalcogenides as Ligands. - The complexation of lanthanide and actinide ions by phosphine oxide ligands remains an active area, and a theoretical assessment of the coordination of phosphine oxides (and phosphate esters) by trivalent lanthanide ions has appeared." Trivalent lanthanide complexes of the functionalised enol phosphine oxide (265), (and a related phosphonate), have been describedComplexes of thorium(iv) with bis(di-phenylphosphino) ethane dioxide and bis(diphenylphosphinoyl)amide have also been characterised." Calixarene systems which bear phosphine oxide... 

A number of other types of calixarene esters are known, including the aryl-sulfonates (often used to establish the calix[4]arenes in the cone conforma-tion ), phosphates (often used as intermediates in the replacement of the OH groups with and phosphonates. ... 

In the phosphorus(V) acids area, there has been continued interest in the preparation of phosphates from elemental phosphorus, and also of compounds derived from the calixarenes. Apart from these, there has been little of real significance in the phosphate field. A much greater interest has been shown in enantio- or diastereo-selectivity in synthesis and reactivity of phosphonates and... 

In more recent times, many structures based on substituted tetrahedra such as phosphonate RPO3 or phosphinate R2PO2 have been explored. This structural world is now merging with that of phosphate-containing calixarenes, cavitands, cyclodextrins, rotaxanes and other large organic ring compounds. 

Phosphonito (5.390a), phosphinito (5.390b) and phosphonate (5.390c) calixarene-[4] derivatives and other P-containing cavitands have been prepared [190-195]. Some of these compounds are useful as catalysts and others are possible metal extractants [196]. 

Phosphorus-containing calixarenes (5,390c) andresorcinarenes (5.390d) have recently been reviewed [197]. Phosphonated calixarenes have recently been utilised to obtain Ag nanoparticles [198]. Phosphorylated calix[8] arenes have been prepared [170]. 

Are calixarenes useful nucleating agents for NP synthesis This hypothesis has been explored and partially validated select examples include CdS nanocrystals within Langmuir-Blodgett layers of amphiphilic calix[8]arenes (d y = 2 nm) [10] colloidal Ag using thiolated cavitands in DMF (d y = 83 nm) [11], smaller Ag NPs by reductiOTi in aqueous solutions of phosphonated calix[n]arenes (d = 2-5 nm)... 

Several reports in the literature show that calixarene derivatives play a crucial role in controlling the size and stability of MNPs [106-108]. For example, Raston reported on the synthesis of p-phosphonic acid calix[8]arene-modified Ru, Pt and Pd nanoparticles in aqueous solution (Fig. 37.16) [109]. The macrocycle was demonstrated to exert a control over the shape and size of the produced nanoparticles by acting as stabilizing agent. Molecular modeling revealed that 12 molecules of the macrocycle surround 2-nm Ru particles, where a H-bonding network among calix[8]arenes contribute to the interfacial self-assembly. 

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