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Anionic complex of antamanide with the nitrate anion has been proven by electrospray ionization mass spectrometry (ESI-MS) method. Further, applying quantum chemical DFT calculations, the most probable structure of this complex was derived. The nitrate anion is embedded in the molecule of antamanide and its oxygens atoms are bonded by seven bonds to the hydrogen atoms of the ligand. Finally, the interaction energy, E(int), of the antamanide-NO3- complex was calculated as E(int) = -175.9 kJ/mol

From extraction experiments, the exchange extraction constants corresponding to the general equilibriums M+ (aq) + NaL+ (org) ⇔ ML+ (org) + Na+ (aq) or M+ (aq) + CsL+ (org) ⇔ ML+ (org) + Cs+ (aq), which take place in the two-phase water–nitrobenzene extraction system (M+ = Li+, H3O+, Ag+, K+, NH4 +, Tl+, Rb+; L = calix[4]arene-bis crown5(1,3-alternate), 26,28-dipropoxycalix[4]arene-crown-5(1,3-alternate), 11,23-dibromo-25,28-dipropoxycalix[4]arene-crown-5 (1,3-alternate) and 1,3-alternate-25,27-dihydroxycalix[4]arene-crown-5; aq = aqueous phase, org = organic phase), were evaluated. The stability constants of the NaL+ and CsL+ complexes were calculated from the extraction of the respective picrates in the system of water–nitrobenzene solution of L. Further, the stability constants of the ML+ complexes in nitrobenzene saturated with water were determined. High selectivities were found in some systems under study.

Electrospray ionisation mass spectrometry was used to investigate the cation–π interaction of Tl+ with [7]helicene. Further, applying quantum mechanical calculations in the frame of the density functional theory, applying B3LYP functional with Def2TZVP basis set, the most probable structure of the [7]helicene–Tl+ complex was derived. In the resulting complex, the ‘central’ cation Tl+ is bounded between two terminal benzene rings of the parent [7]helicene ligand via cation–π interaction. In such conformation, the [7]helicene creates a tweezer for Tl+ ion. The interaction energy, E(int), of this cation–π complex was calculated to be –160 kJ/mol, which is consistent with the formation of the considered cationic complex species. Other structures were also found and generally lie energetically about 19–24 kJ/mol above the tweezer complex. HIGHLIGHTSCation Tl+–[7]helicene complex has been observed using the ESI-MS methodThe structure of the resulting complex has been determined by applying quantum chemical DFT calculationsHelicene functions as a chiral molecular tweezer for Tl+. Cation Tl+–[7]helicene complex has been observed using the ESI-MS method The structure of the resulting complex has been determined by applying quantum chemical DFT calculations Helicene functions as a chiral molecular tweezer for Tl+.

The exchange extraction constants corresponding to the general equilibria M+(aq) + NaL+(org) ⇌ ML+(org) + Na+(aq) and the respective M+(aq) + CsL+(org) ⇌ ML+(org) + Cs+(aq), taking place in the two-phase water–nitrobenzene and water–phenyltrifluoromethyl sulfone (abbrev. FS 13) systems (M+ = Li+, H3O+, Ag+, K+, $${\text{NH}}_{4}^{ + }$$ , Tl+, Rb+; L = calix[4]arene-bis(t-octylbenzo-18-crown-6), 1,3-alternate-25,27-bis(1-octyloxy)calix[4]arene-crown-6 and 1,3-alternate-25,27-bis(3,7-dimethyloctyl-1-oxy)calix[4]arene-benzocrown-6; aq = aqueous phase, org = organic phase) were evaluated. Stability constants of NaL+ and CsL+ were determined from the extraction of picrates and iodides by the solutions of L. Further, the stability constants of the ML+ complexes in nitrobenzene and FS 13 saturated with water were calculated. Enormously high selectivities were found in the systems under study.

Applying quantum chemical calculations, the most likely conformations of the anionic complex species dodecabenzylbambus[6]uril–PF6−, dodecabenzylbambus[6]uril–AsF6−, and dodecabenzylbambus[6]uril–SbF6− were found. In all these complexes, the considered anions, incorporated in the ligand cavity, are bound by hydrogen bonds between methine hydrogen atoms on the convex face of glycoluril units of the dodecabenzylbambus[6]uril ligand and fluorine atoms of the respective “central” anion. Moreover, the interaction energies of the investigated three anionic complexes were calculated. The absolute values of these calculated energies increase in the series of SbF6−

We investigated the extraction of microamounts of Eu3+ and Am3+ from aqueous nitric acid solutions using nitrobenzene solutions of hydrogen dicarbollylcobaltate (H+B−) in the presence of some commercially available dioxa alkyl diamides. The significant synergistic effect was found for some structures of ligand. We suppose that the complexes $${\text{HL}}^{ + }$$, $$\text{ML}^{{\text{3} + }}$$, $$\text{ML}_{\text{2}}^{{\text{3} + }}$$ and $${\text{ML}}_{ 3}^{ 3+ }$$ (M3+ = Eu3+, Am3+) are present in the equilibrium organic phase. Extraction and stability constants of these complex species in water-saturated nitrobenzene have been determined and discussed. Lithium ionophore I and lithium ionophore IV receptors for Eu3+ and Am3+ can be used as efficient extraction agents for nuclear waste treatment.

On the basis of extraction experiments and $$\gamma$$ -activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq) + CsL+(nb) ⇌ ML+(nb) + Cs+(aq) occurring in the two-phase water–nitrobenzene system (M+ = K+, Rb+, Ag+, Tl+; L = bis(crown-6) ether derivatives of calix[4]arene, where aq = aqueous phase and nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the proven ML+ complexes in water-saturated nitrobenzene were calculated and are discussed.

The solvent extraction of microamounts of Eu 3+ and Am 3+ from water into nitrobenzene by means of a mixture of hydrogen dicarbollylcobaltate (H + B - ) and calcium ionophore I (marked as the ligand L) was investigated. The equi­librium data have been explained assuming that the species HL + , HL 2 + ,ML 2 3+ and ML 3 3+ (M 3+ : Eu 3+ or Am 3+ ) are extracted into the organic phase. The extraction and stability constants of the cationic complex species in nitrobenzene saturated with water have been determined and discussed. It was proven experimentally that the ligand L could be considered as a very strong receptor for Eu 3+ and Am 3+ .

The extraction of trivalent europium and americium in the system water—HNO3—3-nitro-α,α,α-trifluorotoluene (F-3)—bis-1,2-dicarbollylcobaltate—N,N,N′,N′-tetraoctyl diglycolamide (L) has been investigated. The experimental data were treated by curve-fitting method using the LETAGROP program. It has been found that the complexes $${\text{HL}}_{{}}^{ + }$$ , $${\text{HL}}_{2}^{ + }$$ , $${\text{ML}}_{ 2}^{3 + }$$ , $${\text{ML}}_{ 3}^{3 + }$$ and $${\text{ML}}_{ 4}^{3 + }$$ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species in F-3 saturated with water have been determined. Extraction in this system can be used for separation of lanthanides and minor actinides from PUREX process raffinate.

By means of electrospray ionization mass spectrometry (ESI-MS), it was evidenced experimentally that the univalent silver cation (Ag+) reacts with the electroneutral pyrene ligand (C16H10) to form especially the cationic complexes [Ag(C16H10)]+ and [Ag(C16H10)2]+. Moreover, applying quantum chemical calculations, five different conformations of these two Ag(I) complexes were derived. Finally, in the solid state, the polymeric complex structure [Ag(pyrene)0.5(CF3SO3)]n·[Ag(toluene)(CF3SO3)]n, crystallizing in the monoclinic system with the centrosymmetric space group P2/c, was prepared and analyzed by X-ray crystallography.

Solvent extraction of microamounts of Eu3+ and Am3+ from water into nitrobenzene by means of a mixture of hydrogen dicarbollylcobaltate and 3,3′-bis(diisopropoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea (L) was studied. The equilibrium data were explained by assuming that the species HL+, $$ {\text{ML}}_{2}^{3 + } $$ , and $$ {\text{ML}}_{3}^{3 + } $$ {M3+ = Eu3+, Am3+; L = 3,3′-bis(diisopropoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea} are extracted into the organic phase. Extraction and stability constants of the cationic complex species in nitrobenzene saturated with water were determined and discussed. From the experimental results it is apparent that this very effective receptor for the Eu3+ and Am3+ cations could be considered as a potential extraction agent for nuclear waste treatment.

On the basis of extraction experiments and gamma-activity measurements, the extraction constant corresponding to the equilibrium Ag+(aq) + 1 center dot Na+(nb) reversible arrow 1 center dot Ag+ (nb) + Na+(aq) occurring in the two phase water nitrobenzene system (1 = [Gly(6)]-antamanide; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (Ag+,1 center dot Na+) = 1.5 +/- 0.1. Further, the stability constant of the 1 center dot Ag+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 degrees C: log beta(nb) (1 center dot Ag+) = 4.5 +/- 0.2. Finally, by using quantum chemical OFF calculations, the most probable structure of the cationic complex species 1 center dot Ag+ was derived. In the resulting complex, the "central" cation Ag+ is coordinated by four noncovalent interactions to the corresponding four carbonyl oxygen atoms of the parent ligand 1. Besides, the whole l center dot Ag+ complex structure is stabilized by two intramolecular hydrogen bonds. The interaction energy of the considered 1 center dot Ag+ complex was found to be -465.5 kJ/mol, confirming also the formation of this cationic species. (C) 2017 Elsevier B.V. All rights reserved.

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent thallium cation (Tl+) forms with meso-octamethylcalix[4]pyrrole (1) the cationic complex species 1 Tl+. When this kinetically stable cation-π complex 1 Tl+ is collisionally activated, it decomposes by elimination of the whole ligand 1 or small meso-octamethylcalix[4]pyrrole fragments. Further, applying quantum chemical DFT calculations, four different conformations of the resulting complex 1 Tl+ were derived. It means that under the present experimental conditions, this ligand 1 can be considered as a very effective macrocyclic receptor for the thallium cation.

By employing electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent sodium cation (Na+) forms with [2.2.2]paracyclophane (C24H24) the cationic complex [Na(C24H24)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [Na(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C3, the “central” cation Na+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is bound to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction. Finally, the interaction energy, E(int), of the considered cation-π complex [Na(C24H24)]+ was found to be −267.3 kJ/mol, confirming the formation of this fascinating complex species as well.

Solvent extraction of micro-amounts of Eu3+ and Am3+ from water into nitrobenzene by means of a mixture of hydrogen dicarbollylcobaltate (H+B-) and tetraisopropyl[oxybis(2,1-ethanediyliminocarbonyl)]-bisphosphoramidate (L) was studied. The equilibrium data were explained assuming that the species HL+, ML2 3+ and ML3 3+ (M3+ = Eu3+ or Am3+) are extracted into the organic phase. Extraction and stability constants of the cationic complex species in nitrobenzene saturated with water were determined and discussed. From the experimental results, it is obvious that this effective ligand L for the Eu3+ and Am3+ could be considered as a potential extraction agent for nuclear waste treatment.

The extraction constant corresponding to the equilibrium Eu3+(aq) + 3A-(aq) + 1(nb) ⇌ 1 Eu3+(nb) + 3A–(nb) occurring in the two-phase water–nitrobenzene system ( A - = CF 3 SO 3 - ; 1 = [2.2.2]paracyclophane; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (Eu3+,3A–) = -5.7 ± 0.1. Further, the stability constant of the 1 Eu3+ complex in nitrobenzene saturated with water was calculated as log Knb (1 Eu3+) = 7.4 ± 0.1. Finally, by using quantum chemical calculations, the most probable conformation of the cationic complex species 1 Eu3+ was derived. In the resulting complex, the “central” cation Eu3+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is bound to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction.

The stability constants of the cationic complexes ML+, where M+= Li+, Na+, H3O+, Ag+, K+, NH4+, Tl+, Rb+, Cs+; and L = calix[4]crown ethers in nitrobenzene saturated with water were determined on the basis of the experimental distribution ratios of these cations. The organic phases of the studied solvent extraction systems were nitrobenzene solutions of the calix[4]crown ether ligands and the lipophilic dicarbollylcobaltate anion. Very high selectivities of the separation of the K/Na, Rb/Na and Cs/Na pairs are anticipated in these systems.

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the silver cation Ag+ forms with corannulene (C20H10) the cationic complex [Ag(C20H10)2]+. Further, applying quantum chemical DFT calculations, the most probable structures of the [Ag(C20H10)2]+ complex were derived. In the resulting complex the “central” cation Ag+, is located between two molecules of the corannulene ligand. Finally, the interaction energy, E(int), of the considered cation-π complex [Ag(C20H10)2]+ was found to be −335.0 to −306.9 kJ/mol.

By using electrospray ionization mass spectrometry, it was proven experimentally that the univalent potassium cation (K+) forms with [2.2.2]paracyclophane (C24H24) the cationic cluster [K(C24H24)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [K(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C 3, the “central” cation K+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is coordinated to all three benzene rings of [2.2.2]paracyclophane via cation–π interaction. Finally, the interaction energy, E(int), of the considered cation–π complex [K(C24H24)]+ was found to be − 614.8 kJ mol−1, confirming the formation of this fascinating complex species as well. It means that the [2.2.2]paracyclophane ligand can be considered as an effective receptor for the potassium cation in the gas phase.

Solvent extraction of microamounts of Eu3+ and Am3+ from water into nitrobenzene by means of a mixture of hydrogen dicarbollylcobaltate (H+B−) and N,N′-diethyl-N,N′-bis(4-ethylphenyl)-1,10-phenanthroline-2,9-dicarboxamide (L) was studied. The equilibrium data were explained assuming that the species HL+, $$ \text{HL}_{\text{2}}^{ + } $$ , $$ \text{ML}_{2}^{3 + } $$ , and $$ \text{ML}_{\text{3}}^{{\text{3} + }} $$ (M3+ = Eu3+, Am3+; L = N,N′-diethyl-N,N′-bis(4-ethylphenyl)-1,10-phenanthroline-2,9-dicarboxamide) are extracted into the organic phase. Extraction and stability constants of the cationic complex species in nitrobenzene saturated with water were determined and are discussed. The reached separation factors SFAm/Eu in this two-phase system are in the range of 19–99. From the experimental results it is apparent that this very effective N,N′-diethyl-N,N′-bis(4-ethylphenyl)-1,10-phenanthroline-2,9-dicarboxamide receptor for the Eu3+ and Am3+ cations could be considered as a potential extraction agent for nuclear waste treatment.

Solvent extraction of microamounts of Eu3 + and Am3 + from water into nitrobenzene by means of a mixture of hydrogen dicarbollylcobaltate (H+ B−) and N,N′-diethyl-N,N′-diphenyl-1,10-phenanthroline-2,9-dicarboxamide (L) was studied. The equilibrium data were explained assuming that the species HL+, H2L2 +, HL2+, ML23 +, and ML33 + (M3 + = Eu3 +, Am3 +; L = N,N′-diethyl-N,N′-diphenyl-1,10-phenanthroline-2,9-dicarboxamide) are extracted into the organic phase. Extraction and stability constants of the cationic complex species in nitrobenzene saturated with water were determined and discussed. From the experimental results it is evident that this very efficient N,N′-diethyl-N,N′-diphenyl-1,10-phenanthroline-2,9-dicarboxamide receptor for the Eu3 + and Am3 + cations could be considered as a potential extraction agent for nuclear waste treatment.

On the basis of extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq) + 1·Na+(nb) $$ \rightleftharpoons $$ 1·M+(nb) + Na+(aq) taking place in the two–phase water–nitrobenzene system (M+ = Li+, H3O+, $$ \text{NH}_{\text{4}}^{ + } $$ , Ag+, K+, Rb+, Tl+, Cs+; 1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the 1·M+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the cation series Cs+

On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H3O+ (aq) + 1·Na+ (nb) ⇄ 1·H3O+ (nb) + Na+ (aq) occurring in the two–phase water–nitrobenzene system (1 = calix[4]arene-(2,3-naphthylene-crown-6,crown-6); aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex(H3O+,1·Na+) = −0.2 ± 0.1. Further, the stability constant of the 1·H3O+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb(1·H3O+) = 5.9 ± 0.2. Finally, applying quantum chemical DFT calculations, the most probable structure of the cationic complex species 1·H3O+ was derived. In the resulting complex, the “central” cation H3O+ is bound by three strong hydrogen bonds to two phenoxy oxygen atoms and to one ethereal oxygen from the crown-6 moiety of the parent ligand 1. The interaction energy, E(int), of the considered 1·H3O+ complex was found to be −416.0 kJ/mol, confirming the formation of this cationic species as well.

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent silver cation Ag + forms with meso -octamethylcalix[4]pyrrole (abbrev. 1 ) the cationic complex species 1 ·Ag + . Further, applying quantum chemical DFT calculations, four different conformations of the resulting complex 1 ·Ag + were derived. It means that under the present experimental conditions, this ligand 1 can be considered as a macrocyclic receptor for the silver cation.

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent lithium cation (Li+) forms with [2.2.2]paracyclophane (C24H24) the cationic complex [Li(C24H24)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [Li(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C3, the “central” cation Li+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is coordinated to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction. Finally, the interaction energy, E(int), of the considered cation-π complex [Li(C24H24)]+ was found to be –324.7 kJ/mol, confirming the formation of this fascinating complex species as well.

Solvent extraction of micro amounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of 3,3′-bis(diphenoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea (L) was investigated. The equilibrium data were explained assuming that the species HL+, ML3+, and $$ {\text{ML}}_{2}^{3 + } $$ (M3+ = Eu3+, Am3+; L = 3,3′-bis(diphenoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species were determined in nitrobenzene saturated with water. It was found that the values of the stability constants of the corresponding complexes $$ \text{EuL}_{n}^{{\text{3} + }} $$ and $$ \text{AmL}_{n}^{{\text{3} + }} $$ , where n = 1, 2 and L is 3,3′-bis(diphenoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea, in water-saturated nitrobenzene are comparable. Finally, it was proven experimentally that in the nitrobenzene medium, the 3,3′-bis(diphenoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea ligand is a very effective receptor for the Eu3+ and Am3+ cations.

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the lithium cation (Li + ) forms with racemic [6]helicene (C 26 H 16 ) the cationic complex species [Li(C 26 H 16 )] + . Further, applying quantum chemical DFT calculations, the most probable structure of the [Li(C 26 H 16 )] + complex was derived. In the resulting “asymmetrical” complex, the “central” cation Li + is bound by six bonds to six carbon atoms from the two terminal benzene rings of the parent [6]helicene ligand via cation-π interaction. Finally, the interaction energy, E (int), of the considered cation-π complex [Li(C 26 H 16 )] + was found to be −248.0 kJ/mol, confirming the formation of this cationic complex species as well.

Employing electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the [6]helicene – Ag+ complex (i.e., [Ag(C26H16)]+) exists in the gas phase. Further, applying quantum mechanical DFT calculations, the most probable structure of this cationic complex [Ag(C26H16)]+ was derived. Finally, in the solid state, the complex [6]helicene – silver hexafluoroantimonate – monohydrate (i.e., C26H16 – AgSbF6 – H2O), crystallizing in the monoclinic system with the centrosymmetric space group P21/c, was prepared and analyzed by X-ray crystallography.

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+ B−) in the presence of bis(diphenylphosphino)acetylene dioxide (DPPADO, L) was investigated. The equilibrium data were explained assuming that the species HL+, ML3 +, ML23 +, and ML33 + (M3 + = Eu3 +, Am3 +) are extracted into the organic phase. The values of extraction and stability constants of the complex species in nitrobenzene saturated with water were determined. It was found that the stability constants of the corresponding complexes EuLn3 + and AmLn3 +, where n = 1, 2, 3 and L is DPPADO, in water-saturated nitrobenzene are comparable or the same, respectively.

Extraction experiments in the two-phase water-nitrobenzene system and γ-activity measurements were used to determine the stability constant of the enniatin B–K+ complex dissolved in nitrobenzene saturated with water as 105.5±0.2. Quantum mechanical calculations were applied to predict the most probable structure of this cationic complex species.

On the basis of extraction experiments in the two-phase water–nitrobenzene system and γ-activity measurements, we determined the stability constant of the cyclosporin A–Ba2+ cationic complex dissolved in nitrobenzene saturated with water as 109.1 ± 0.2. Using quantum mechanical calculations, the most probable structure of this complex species was derived. In the resulting complex, the “central” cation Ba2+ is bound by six bonds to the respective six carbonyl oxygen atoms of the parent cyclosporin A ligand. The interaction energy of this proven cationic complex was found to be −769.5 kJ mol−1, confirming also the formation of the mentioned complex species.

On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Ag+(aq) + 1·Cs+ (nb) 1·Ag+(nb) + Cs+ (aq) occurring in the two-phase water–nitrobenzene system (1 = calix[4]arene-(1,2-phenylene-crown-6,crown-6); aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex(Ag+, 1·Cs+) = −1.3 ± 0.1. Further, the very high stability constant of the 1·Ag+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb(1·Ag +) = 9.3 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structures A and B of this cationic complex species, which are obviously in a dynamic equilibrium, were derived.

On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Tl+ (aq) + 1·Cs+ (nb) ⇄ 1·Tl+ (nb) + Cs+ (aq) occurring in the two-phase water–nitrobenzene system (1 = calix[4]arene-(1,2-phenylene-crown-6,crown-6); aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex(Tl+,1·Cs+) = 0.4 ± 0.1. Further, the very high stability constant of the 1·Tl+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β(1·Tl+) = 9.9 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structures A and B of this cationic complex species, which are obviously in a dynamic equilibrium, were derived.

Solvent extraction of microamounts of trivalent europium and americium into nitrobenzene by using a mixture of hydrogen dicarbollylcobaltate (H+B−) and magnesium ionophore II (L) was studied. The equilibrium data were explained assuming that the species HL+, H L 2 + ${\rm{HL}}_2^ + $ , M L 2 3 + ${\rm{ML}}_2^{3 + }$ , and M L 3 3 + ${\rm{ML}}_3^{3 + }$ (M3+ = Eu3+, Am3+; L=magnesium, ionophore II) are extracted into the nitrobenzene phase. Extraction and stability constants of the cationic complex species in nitrobenzene saturated with water were determined and discussed. From the experimental results it is evident that this effective magnesium ionophore II receptor for the Eu3+ and Am3+ cations could be considered as a potential extraction agent for nuclear waste treatment.

Solvent extraction of micro amounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of Sodium ionophore III (L) was investigated. The equilibrium data were explained assuming that the species HL+, $$ \text{HL}_{2}^{ + } $$ , ML3+, $$ \text{ML}_{\text{2}}^{{\text{3} + }} $$ , and $$ \text{ML}_{\text{3}}^{{\text{3} + }} $$ (M3+ = Eu3+, Am3+; L = Sodium ionophore III) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species were determined in nitrobenzene saturated with water. It was found that the values of the stability constants of the corresponding complexes $$ {\text{EuL}}_{n}^{ 3+ } $$ and $$ {\text{AmL}}_{n}^{ 3+ } $$ , where n = 1, 2, 3 and L is Sodium ionophore III, in water-saturated nitrobenzene are comparable. Finally, it was proven experimentally that in the considered nitrobenzene medium, the investigated Sodium ionophore III ligand is a very effective receptor for the Eu3+ and Am3+ cations. It means that this receptor can be considered as a potential extraction agent for nuclear waste treatment.

On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Sr2 +(aq) + 2A−(aq) + 1(nb) ⇄ 1·Sr2 +(nb) + 2A−(nb) occurring in the two-phase water–nitrobenzene system (A− = picrate, 1 = macrocyclic lactam receptor — see Scheme 1 ; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (1·Sr2 +, 2A−) = − 4.0 ± 0.1. Further, the stability constant of the 1·Sr2 + cationic complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Sr2 +) = 5.1 ± 0.1. Finally, applying quantum mechanical DFT calculations, the most probable structure of the cationic complex species 1·Sr2 + was derived. In the resulting complex, which is most energetically favored, the “central” cation Sr2 + is bound by five bonding interactions to two ethereal oxygen atoms and two carbonyl oxygens, as well as to one carbon atom of the corresponding benzene ring of the parent macrocyclic lactam receptor 1 via cation–π interaction.

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+ (aq) + 1·Cs+(org) ⇄ 1·M+ (org) + Cs+ (aq) taking place in the two–phase water–phenyltrifluoromethyl sulfone (abbrev. FS-13) system (M+ = Ag+, Tl+, K+, Rb+; 1 = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, org = FS-13 phase) were determined. Further, the stability constants of the 1·M+ complexes in FS-13 saturated with water were calculated; they were found to increase in the series of K+

By means of electrospray ionization mass spectrometry (ESI-MS), it was evidenced experimentally that the rubidium cation (Rb + ) reacts with the electroneutral [2.2.2]paracyclophane ligand (C 24 H 24 ) to form the cationic complex [Rb(C 24 H 24 )] + . Moreover, applying quantum chemical calculations, the most probable conformation of the proven [Rb(C 24 H 24 )] + complex was solved. In the complex [Rb(C 24 H 24 )] + having a symmetry very close to C 3 , the “central” cation Rb + , fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is coordinated to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction. Finally, the binding energy, E (int), of the considered cation-π complex [Rb(C 24 H 24 )] + was evaluated as –99.3 kJ/mol, confirming the formation of this fascinating complex species as well. This means that the [2.2.2]paracyclophane ligand can be considered as a receptor for the rubidium cation in the gas phase.

Using quantum mechanical calculations, the most probable structures of the anionic complex species dodecabenzylbambus[6]uril–Cl−, dodecabenzylbambus[6]uril–Br−, and dodecabenzylbambus[6]uril–I− were derived. In these three complexes, each of the considered univalent halide anions, included in the center of the macrocyclic cavity, is bound by 12 weak C–H···X− (X− = Cl−, Br−, I−) hydrogen bonds between methine hydrogen atoms on the convex face of glycoluril units and the respective anion. The lengths of these C–H···X− hydrogen bonds increase in the series of Cl−