ChemInform Abstract: Conformationally Mobile Wide Rim Carbamoylmethylphosphine Oxide (CMPO)-Calixarenes.

Selective N-Protection of a Tetraamino Calix[4]arene Tetraether.

Conformationally Mobile Wide Rim Carbamoylmethylphosphine Oxide (CMPO)-Calixarenes

Six new calix[4]arene derivatives 2a–f have been synthesised, bearing CMPO-like functions (-NH–C(O)–CH2–P(O)Ph2) at their wide rim. They differ by their alkoxy groups at the narrow rim, comprising all possible combinations of methoxy and syn-propoxy groups including the conformationally mobile tetramethyl ether 2e and the tetrapropyl ether 2f fixed in the cone conformation. Their extraction behaviour for thorium(IV) and several lanthanides(III) from 1M HNO3 to dichloromethane has been studied and compared also to non cyclic calixarene analogues 6a–e. Surprisingly the best extraction results were found for the 1,2-dimethoxy-3,4-dipropoxy derivative 2c among the calixarenes and for the tetram…

Sterically and guest-controlled self-assembly of calix[4]arene derivatives.

In solvents such as chloroform or benzene, tetraurea calix[4]arenes 1 form dimeric capsules in which one solvent molecule is usually included as guest. To explore the structural requirements for the formation of such hydrogen-bonded dimers we replaced one p-tolylurea residue by a simple acetamide function. The resulting calix[4]arene 2 a, substituted at its wide rim with one acetamide and three p-tolylurea functions, assumes a C(1)-symmetrical conformation in apolar solvents as shown by (1)H NMR, which is not compatible with the usual capsule. In the crystalline state, four molecules of 2 a, adopting a pinched cone conformation, assemble into a quasi S(4)-symmetrical tetramer stabilized by …

ChemInform Abstract: Double- and Multicalixarenes

Separation of lanthanides and actinides using magnetic silica particles bearing covalently attached tetra-CMPO-calix[4]arenes

Calix[4]arene tetraethers in the cone conformation bearing four –NH–CO–CH2–P(O)Ph2 (= CMPO) residues on their wide rim and one, two or four ω-amino alkyl residues of various lengths at the narrow rim were synthesized. Reaction with dichlorotriazinyl (DCT) functionalized magnetic particles led to complete coverage of the available surface by covalently linked CMPO-calix[4]arenes in all cases. Magnetically assisted removal of Eu(III) and Am(III) from acidic solutions was distinctly more efficient with these particles in comparison to analogous particles bearing the same amount of analogous single-chain CMPO-functions. The best result, an increase of the extraction efficiency by a factor of 14…

Lanthanide complexation with CMPO and CMPO-calix[4]arenes in solution: spectrophotometric and electrospray mass spectrometric approaches.

The binding of lanthanide(III) cations with organophosphorous ligands like CMPO and related calix[4]arene-based derivatives have been investigated using two experimental methods. The stability constants of the lanthanum, europium and ytterbium complexes were first determined in methanol by UV absorption spectrophotometry in the presence of nitrate or chloride anions. The results showed that the stoichiometry and the stability of the complexes formed depend on the position of the CMPO moieties either on the wide or the narrow rim of the calixarene scaffold, the nature of the medium, the conformational mobility of the ligands. Complexation of lanthanum was also followed by ESI-mass spectromet…

Modification of calix[4]arenes with CMPO-functions at the wide rim. Synthesis, solution behavior, and separation of actinides from lanthanides

Two calix[4]arene tetraethers (Y = C5H11, C14H29) bearing on their wide rim four –N(Me)–CO–CH2–P(O)Ph2 residues were synthesized for the first time. Their ability to extract lanthanides and actinides from an acidic aqueous phase to organic phases (CH2Cl2, NPHE) was studied. In comparison to the corresponding –NH-analogs, they are less efficient extractants, the selectivity for the light over the heavy lanthanides is less pronounced, while there is still an interesting selectivity of Am3+ over Eu3+. Stability constants for selected lanthanide salts were determined also in homogenous phase (methanol, acetonitrile) but do not account for the different extraction results. The complexation of Gd…

CMPO-substituted calix[6]- and calix[8]arene extractants for the separation of An3+/Ln3+ from radioactive waste

Abstract Three calix[6]arene derivatives ( 1a – c ) and two calix[8]arene derivatives ( 2a , b ), with six and eight CMPO residues, respectively, attached to the narrow/lower rim via ether links, were synthesised. Preliminary liquid–liquid extraction studies for Eu(III) and Am(III) from aqueous nitric acid to o -nitrophenylhexyl ether reveal remarkable properties with respect to efficiency and selectivity, especially for the tert -butylcalix[6]arene derivative with a –(CH 2 ) 3 – spacer.

Self-assembled dimers with supramolecular chirality

The possibilities to form dimeric capsules with supramolecular chirality from tetraurea calix[4]arenes composed of two different phenolic urea units are discussed in general and demonstrated experimentally for various selected examples.

Dendritic octa-CMPO derivatives of calix[4]arenes

Abstract Calix[4]arenes substituted at the narrow or wide rim by eight carbamoylmethyl-phosphine oxide (CMPO) functions in a dendritic manner were synthesised and studied in extraction of Eu 3+ and Am 3+ from aqueous nitric acid into o -nitrophenylhexyl ether. 1 H NMR relaxivity titrations for a wide rim octa-CMPO reveal the clear formation of a solvent-free 1:2 ligand/metal complex, while the wide rim tetra-CMPO formed oligomeric complexes under similar conditions.

Double- and Multi-Calixarentes

Calixarenes are easily (and often selectively) functionalized and therefore they can be combined in various ways to larger molecules containing more than one calixarene substructure. In the following chapter we will try to give an overview on such multicalixarenes held together by "conventional" covalent links. Self-assembled structures are treated separately in Chapter 8. The earliest examples for double calixarenes of importance are the carcerands and hemicarcerands of D. Cram in which two resorcarene derived cavitands are combined. Due to their unique properties to include (more or less permanently) smaller molecules, they are treated separately in Chapter 10. Further combinations of cav…