Françoise Arnaud-Neu

Calixarenes with diphenylphosphoryl acetamide functions at the upper rim. A new class of highly efficient extractants for lanthanides and actinides

Various calix[4]arene tetraalkyl ethers and a calix[5]arene pentaalkyl ether substituted at the upper rim by the CMPO-like functional group –NH–C(O)–CH2–P(O)Ph2 as well as some linear model compounds have been synthesized for the first time. Their ability to extract europium, thorium, neptunium, plutonium and americium from 1 mol dm–3 aqueous HNO3 into methylene chloride or o-nitrophenyl hexyl ether was studied under various conditions. All the new oligomeric ligands, but especially the calixarene derivatives, are tremendously strong extractants compared with the commonly used CMPO [(N,N-diisobutylcarbamoylmethyl)octylphenylphosphine oxide]. Also in transport studies through supported liquid membranes their efficiency is higher than that of CMPO which shows lower transport rates even at a 10-fold concentration.

EXTRACTION AND COMPLEXATION OF ALKALI, ALKALINE EARTH, AND F-ELEMENT CATIONS BY CALIXARYL PHOSPHINE OXIDES

The selective extraction behaviour and the stability constants of a series of calixarenes bearing phosphine oxides on their lower rims (see figure) have been studied with alkali and alkaline earth cations, as well as EuIII and ThIV as models of tri- and tetravalent actinides. The calixaryl phosphine oxides are much more efficient in extraction than the classical extractants used in nuclear waste treatment.

A PC compatible computer program for the calculation of equilibrium constants by the simultaneous processing of different sets of experimental results

A new PC compatible computer program SIRKO for the calculation of the equilibrium constants by means of the simultaneous processing of different experimental data from various techniques is given. This program is characterized by the application of a universal response function, which allows many different physicochemical methods to be used to study equilibria without any modification of the program. It is also possible to refine additional parameters (electrode parameters, initial analytic concentration, etc). We have used the least-squares method with the weightings calculated according to the error propagation rule taking into account all independent variables. To minimize the function, singular Jacobian decomposition is applied. This allows control of its range and forms a set of parameters, determined from the experimental data.

Calixarenes, new selective molecular receptors

Calixarenes are easily amenable to chemical modifications, e.g. derivatization of the phenolic hydrogen atoms or substitution at the para-positions, which can be operated separately or combined. They thus assume the role of platforms supporting arrays of functional groups able to act as ligating sites and resulting in a great variety of receptors displaying specific complexing abilities. A selection of examples are presented with the aim of illustrating the different factors of their ionic recognition properties and their already existing applications in the field of chemical sensors.

Calix[5]arene‐Based Molecular Vessels for Alkylammonium Ions

Calix[5]arenes locked in a C5v-symmetric cone conformation (depicted schematically on the right as a truncated pyramid) provide highly preorganized cavities for the formation of strong 1:1 inclusion complexes with linear alkylammonium ions; the nBuNH3+/tBuNH3+ selectivity is up to 103. These calixarenes also act as biomimetic host systems towards specific amino acid methyl esters and display an enzymelike selectivity. R is, for example, Me, CO2Me.

Solution thermodynamics of amino acid–18-crown-6 and amino acid–cryptand 222 complexes in methanol and ethanol. Linear enthalpy–entropy compensation effect

Stability constants, free energies, enthalpies and entropies of complexation of amino acids with synthetic macrocyclic ligands (18-crown-6 and cryptand 222) in methanol and ethanol are reported. No significant variations are found in the free energies of complexation of the various amino acids with these two ligands as a result of a remarkable enthalpy–entropy compensation effect. Free energies of transfer of amino acids and recently isolated amino acid–18-crown-6 and amino acid–cryptand 222 complexes have been mostly obtained from solution thermodynamic data of the free and complexed amino acids in the appropriate solvents. Analysis of transfer-free-energy data indicates that in the amino acid–macrocyclic complex, most of the amino acid molecule is fully exposed to the reaction medium. Previous suggestions on the linear enthalpy–entropy relationship for complexation reactions involving crown ethers and cryptands with metal and organic cations in different reaction media are discussed. The implications of the results obtained for amino acid–macrocyclic complexation reactions to processes of biological importance are considered.

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 tetramer 6d among the linear compounds. Extraction of americium(III) in comparison to curium(III) and various lanthanides(LaIII), Ce(III), Nd(III), Sm(III), Eu(III)) from 0.1– 3M HNO3 to NPHE (o-nitrophenyl hexyl ether) was most effective again for 2c. Among these cations, the highest distribution coefficients were found for Am(III) and the lowest for Ce(III) with a maximum generally in the range of 1–2M HNO3.

New organophosphorus calix[4]arene ionophores for trivalent lanthanide and actinide cations

New calix[4]arene phosphoryl derivatives have been synthesized, starting from a calix[4]arene (cone conformer) bearing four P(O)–H functional groups at the wide rim as synthon. Their binding properties towards trivalent lanthanide and actinide cations are investigated by complexation studies in methanol, and liquid–liquid extraction studies. The carbamoylmethylphosphine oxide and diphosphine dioxide derivatives display the ‘calixarene effect’, i.e., they are more efficient than their constitutive binding sites. The studies also reveal the importance of the attachment mode of CMPO-functions to the calixarene platform for the cation binding properties.

EXTRACTION OF TRIVALENT LANTHANIDES AND ACTINIDES BY “CMPO-LIKE” CALIXARENES

ABSTRACT Extractive properties of calix[4]arenes bearing carhamoylmethylphosphine oxide moieties on their upper rim toward trivalent lanthanide and actinide cations were investigated. The study revealed that these molecules selectively extract light lanthanides and actinides from heavy lanthanides. All parameters present in the extraction system were varied to determine the origin of the selectivity. It was found that this selectivity requires a calix[4]arene platform and acetamidophosphine oxide groups containing phenyl substituents on the four phosphorus atoms.

Complexation and transport of alkali, alkaline earth, transition and heavy metal cations by p-tert-butyldihomooxacalix[4]arene tetra(diethyl)amide

The binding properties of the tetra(diethyl)amide (2) derived from p-tert-butyldihomooxacalix[4]arene, in the cone conformation, towards alkali, alkaline earth, transition (Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) and heavy (Ag+, Cd2+, Hg2+ and Pb2+) metal cations have been established by extraction studies of metal picrates from an aqueous solution into dichloromethane, transport experiments with the same salts through a dichloromethane membrane and stability constant measurements in methanol. Results concerning the calorimetric study of Na+ and K+ complexes in methanol are presented. The affinity of 2 for some cations (Na+, K+, Ba2+, Ag+ and Zn2+) has been investigated by 1H NMR spectrometry, as well. The results are compared to those obtained with the analogous calix[4]arene tetraamide derivative 3. Amide 2 displays a preference for the alkali cations (mainly Na+ and K+) in contrast to amide 3 that prefers the alkaline earth cations. Ag+ and Cd2+ soft Lewis acids are also strongly bound by both amides. 1H NMR titrations confirm the formation of 1∶1 complexes between 2 and all cations studied, also suggesting that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. 2 shows transport rates that do not follow the same trends as the stability constants or extraction percentages; it can therefore be characterized as a selective receptor.