Affinity capillary electrophoresis employed for determination of stability constants of antamanide complexes with univalent and divalent cations in methanol.

Affinity capillary electrophoresis (ACE) and pressure-assisted ACE were employed to study the noncovalent molecular interactions of antamanide (AA), cyclic decapeptide from the deadly poisonous fungus Amanita phalloides, with univalent (Li+ , Na+ , K+ , and NH4+ ) and divalent (Mg2+ and Ca2+ ) cations in methanol. The strength of these interactions was quantified by the apparent stability constants of the appropriate AA-cation complexes. The stability constants were calculated using the nonlinear regression analysis of the dependence of the effective electrophoretic mobility of AA on the concentration of the above ions in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, pHMeOH 7.8, containing 0-50 mM concentrations of the above ions added in the form of chlorides). Prior to stability constant calculation, the AA effective mobilities measured at actual temperature inside the capillary and at variable ionic strength of the BGEs were corrected to the values corresponding to the reference temperature of 25°C and to the constant ionic strength of 10 mM. From the above ions, sodium cation interacted with AA moderately strong with the stability constant 362 ± 16 L/mol. K+ , Mg2+ , and Ca2+ cations formed with AA weak complexes with stability constants in the range 37-31 L/mol decreasing in the order K+ > Ca2+ > Mg2+ . No interactions were observed between AA and small Li+ and large NH4+ cations.

Interaction Between the Rubidium Cation and [2.2.2]Paracyclophane: Experimental and Theoretical Study.

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 (C24H24) to form the cationic complex [Rb(C24H24)]+. Moreover, applying quantum chemical calculations, the most probable conformation of the proven [Rb(C24H24)]+ complex was solved. In the complex [Rb(C24H24)]+ having a symmetry very close to C3, 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(C24H24)]+ 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.

Affinity capillary electrophoresis and density functional theory study of noncovalent interactions of cyclic peptide [Gly6 ]-antamanide with small cations.

ACE and density functional theory were employed to study the noncovalent interactions of cyclic decapeptide glycine-6-antamanide ([Gly6 ]AA), synthetic derivative of native antamanide (AA) peptide from the deadly poisonous fungus Amanita phalloides, with small cations (Li+ , Rb+ , Cs+ , NH4+ , and Ca2+ ) in methanol. The strength of these interactions was quantified by the apparent stability constants of the appropriate complexes determined by ACE. The stability constants were calculated using the nonlinear regression analysis of the dependence of the effective electrophoretic mobility of [Gly6 ]AA on the concentration of the above ions in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, pHMeOH 7.8, containing 0-70 mM concentrations of the above ions added in the form of chlorides). Prior to stability constant calculation, the effective mobilities measured at actual temperature inside the capillary and at variable ionic strength of the BGEs were corrected to the values corresponding to the reference temperature of 25°C and to the constant ionic strength of 10 mM. From the above ions, Rb+ and Cs+ cations interacted weakly with [Gly6 ]AA but no interactions of [Gly6 ]AA with univalent Li+ and NH4+ ions and divalent Ca2+ ion were observed. The apparent stability constants of [Gly6 ]AA-Rb+ and [Gly6 ]AA-Cs+ complexes were found to be equal to 13 ± 4 and 22 ± 3 L/mol, respectively. The structural characteristics of these complexes, such as position of the Rb+ and Cs+ ions in the cavity of the [Gly6 ]AA molecule and the interatomic distances within these complexes, were obtained by the density functional theory calculations.

Affinity capillary electrophoresis and quantum mechanical calculations applied to investigation of [Gly6 ]-antamanide binding with sodium and potassium ions.

ACE in a free solution and quantum mechanical density functional theory have been applied to the investigation of interactions of glycine-6-antamanide ([Gly6 ]AA), a synthetic derivative of cyclic decapeptide antamanide isolated from the highly poisonous mushroom Amanita phalloides, with sodium or potassium ions in methanol. First, from the dependence of effective electrophoretic mobility of [Gly6 ]AA on Na+ or K+ ions concentration in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, pHMeOH 7.8, containing 0-50 mM NaCl or 0-40 mM KCl), the apparent binding (stability) constants of [Gly6 ]AA-Na+ and [Gly6 ]AA-K+ complexes were evaluated as 26 ± 1 and 14 ± 1 L/mol, respectively. The employed ACE method included correction of the effective mobilities measured at ambient temperature and at variable ionic strength of the BGEs to the mobilities related to the reference temperature 25°C and to the constant ionic strength 10 mM. Second, the interaction energies of the [Gly6 ]AA-Na+ and [Gly6 ]AA-K+ complexes (-466.3 and -345.2 kJ/mol, respectively) and the structural details of these complexes, such as position of the Na+ and K+ ions in the cavity of the [Gly6 ]AA molecule and the interatomic distances within these complexes, were determined by the density functional theory calculations.

N,N,N',N'-Tetrabutyl-1,10-phenanthroline-2,9-dicarboxamide as Very Effective Extraction Agent for Trivalent Europium and Americium.

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,N',N'-tetrabutyl-1,10-phenanthroline-2,9-dicarboxamide (L) was studied. The equilibrium data were explained assuming that the species HL+, H2L2+, HL+2, ML3+2, and ML3+3 (M3+ = Eu3+, Am3+; L = N,N,N',N'-tetrabutyl-1,10-phenanthroline-2,9-dicarboxamide) 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 N,N,N',N'-tetrabutyl-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.

Theoretical study on the protonation of cucurbit[7]uril.

By using quantum mechanical DFT calculations, the most probable structures of the cucurbit[7]urilH3O+ and cucur-bit[7]uril'(H3O+)2 cationic complex species were derived. In these two complexes having a plane symmetry, each of the considered H3O+ cations is bound by relatively strong hydrogen bonds to the corresponding carbonyl oxygens of the parent cucurbit[7]uril macrocycle.

Bambus[6]uril as a novel macrocyclic receptor for the nitrate anion.

By using quantum mechanical DFT calculations, the most probable structure of the bambus[6]uril x NO3(-) anionic complex species was derived. In this complex having C3 symmetry, the nitrate anion NO3(-), included in the macrocyclic cavity, is bound by twelve weak hydrogen bonds between methine hydrogen atoms on the convex face of glycoluril units and the considered NO3(-) ion.

Complexation of the ammonium cation with dibenzo-18-crown-6: extraction and DFT study.

From extraction experiments and gamma-activity measurements, the extraction constan corresponding to the equilibrium NH4(+)(aq) + 1*Na(+)(nb) <=> 1*NH4(+)(nb) + Na(+)(aq) taking place in the two-phase water - nitrobenzene system (1 = dibenzo-18-crown-6, aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K(ex) (NH4(+),1*Na(+)) = -0.1 +/- 0.1. Further, the stability constant of the 1*NH4(+) complex species in water-saturated nitrobenzene was calculated for a temperature 25 degrees C as log beta (1*NH4(+)) = 5.7 +/- 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structure of the 1*NH4(+) cationic complex was derived. In this complex, the "central" cation NH4(+) is bound by three strong linear hydrogen bonds to the three corresponding ethereal oxygen atoms of the parent crown ligand 1. The interaction energy of the resulting complex 1*NH4(+) was found to be -796.1 kJ/mol, confirming the formation of the considered complex species.

Extraction and DFT study on the complexation of Zn(2+) with beauvericin.

From extraction experiments and g-activity measurements, the exchange extraction constant corresponding to the equilibrium Zn2+(aq) + 1 . Sr2+(nb) <-> 1 . Zn2+(nb) + Sr2+(aq) taking place in the two-phase water-nitrobenzene system (1 = beauvericin; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (Zn2+, 1 . Sr2+) = -0.3 ± 0.1. Further, the stability constant of the beauvericin - zinc complex (abbrev. 1 . Zn2+) in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log ßnb (1 . Zn2+) = 9.1 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structure of the 1 . Zn2+ complex species was predicted.

Synergistic extraction of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate and dodecaethylene glycol.

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B-) in the presence of dodecaethylene glycol (DDEG, L) has been investigated. The equilibrium data have been explained assuming that the species HL+, H2L2+, ML3+ and MH-1L2+ (M3+ = Eu3+, Am3+; L = DDEG) are extracted into the organic phase. The values of extraction and stability constants of the complex species in nitrobenzene saturated with water have been determined. It was found that in this nitrobenzene medium, the stability constant of the EuL3+ complex is comparable with that of AmL3+.

Solvent extraction of calcium and strontium into nitrobenzene by using a synergistic mixture of hydrogen dicarbollylcobaltate and bis(diphenylphosphino)methane dioxide.

Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B-) in the presence of bis(diphenylphosphino)methane dioxide (DPPMDO, L) has been investigated. The equilibrium data have been explained assuming that the species HL+, HL2+, ML2(2+), ML3(2+) and ML4(2+) (M2+ = Ca2+, Sr2+) are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined. In the considered nitrobenzene medium, it was found that the stability constants of the complexes CaL2(2+), CaL3(2+) and CaL4(2+), where L is DPPMDO, are somewhat higher than those of the corresponding complex species SrL2(2+), SrL3(2+) and SrL4(2+) with the same ligand L.

Synergistic Extraction of Some Univalent Cations into Nitrobenzene by Using Sodium Dicarbollylcobaltate and Dibenzo-21-crown-7.

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+ (aq) + 1•Na+ (nb) <-> 1•M+ (nb) + Na+ (aq) taking place in the two-phase water-nitrobenzene system (M+ = Li+, H+, NH+4, Ag+, K+, Rb+, Tl+, Cs+; 1 = dibenzo-21-crown-7; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the 1•M+ complexes in water - saturated nitrobenzene were calculated; they were found to increase in the series of H+ < Ag+ < Li+ < Cs+ < K+, Rb+ < NH+4 < Tl+.

Synergistic Extraction of Strontium into Nitrobenzene by Using Hydrogen Dicarbollylcobaltate and N,N,N´,N´-Tetracyclohexyl-oxybis(o-phenyleneoxy) diacetamide.

Extraction of microamounts of strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B-) in the presence of N,N,N´,N´-tetracyclohexyl-oxybis(o-phenyleneoxy)diacetamide (abbrev. barium ionophore I, L) has been investigated. The equilibrium date have been explained assuming that the species HL+, SrL2+ and SrL2+2 are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined.

Experimental and Theoretical Study on the Complexation of the Thallium Cation with Dibenzo-18-crown-6.

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Tl+(aq) + 1.Na+(nb) <-> 1.Tl+(nb) + Na+(aq) taking place in the two-phase water-nitrobenzene system (1 = dibenzo-18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex(Tl+, 1.Na+) = 2.1. Further, the stability constant of the complex 1.Tl+ in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log ßnb (1.Tl+) = 6.6. Finally, by using quantum mechanical DFT calculations, the most probable structure of the resulting complex 1.Tl+ was solved.

Experimental and theoretical study on the complexation of beauvericin with the ammonium cation.

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium NH4+(aq) + NaL+ (nb) <-> NH4L+(nb) + Na+ (aq) taking place in the two-phase water-nitrobenzene system (L = beauvericin; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (NH4+, NaL+) = 1.5 ± 0.1. Further, the stability constant of the NH4L+ complex in water-saturated nitrobenzene was calculated for a temperature of 25 °C as log ßnb (NH4L+) = 4.6 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structure of the NH4L+ cationic complex species was derived. In this complex having C3 symmetry, the ammonium cation NH4+ is bound by three strong linear hydrogen bonds to the three corresponding oxygen atoms of the parent beauvericin ligand L. The interaction energy of the resulting complex NH4L+ was found to be -828.8 kJ/mol, confirming the formation of the considered complex NH4L+.

Solvent Extraction of Calcium into Nitrobenzene by Using an Anionic Ligand Based on Cobalt Bis(Dicarbollide) Anion with Covalently Bonded CMPO Function.

From extraction experiments and γ-activity measurements, the exchange extraction constantcorresponding to the general equilibrium Ca2+(aq) + 2HL(nb) <-> CaL2(nb) + 2H+(aq) taking place in the two-phase water-nitrobenzene (L- = anionic ligand based on cobalt bis(dicarbollide) anion with covalently bonded CMPO function; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (Ca2+, 2HL) = 0.0 ± 0.1. Further, the stability constant of the electroneutral complex species CaL2 in water-saturated nitrobenzene was calculated for a temperature of 25 °C : log ßnb (CaL2) = 11.0 ± 0.2.

Complexation of the Silver Cation with Dibenzo-30-crown-10: Extraction and DFT Study.

From extraction experiments and γ-activity measurements, the exchange extraction constant corresponding to the equilibrium Ag+(aq) + 1.Cs+(nb) <-> 1.Ag+ (nb) + Cs+(aq) taking place in the two-phase water-nitrobenzene system (1 = dibenzo-30-crown-10; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (Ag+, 1.Cs+) = -1.7 ± 0.1. Further, the stability constant of the complex 1.Ag+ in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log ßnb (1.Ag+) = 6.0 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structure of the resulting complex 1.Ag+ was solved.

Solvent Extraction of Some Divalent Metal Cations into Nitrobenzene by Using a Synergistic Mixture of Strontium Dicarbollylcobaltate and p-tert-Butylcalix[4]arene-tetrakis (N,N-Diethylacetamide).

From extraction experiments and g-activity measurements, the exchange extraction constants corresponding to the general equilibrium M2+(aq) + 1•Sr2+(nb) <-> 1•M2+(nb) + Sr2+(aq) taking place in the two-phase water-nitrobenzene system (M2+ = Ca2+, Ba2+, Cu2+, Zn2+, Cd2+, Pb2+, UO22+, Mn2+, Co2+, Ni2+; 1 = p-tert-butylcalix[4]arene-tetrakis(N,N-diethylacetamide); aq = aqueous phase, nb = nitrobenzene phase) were determined. Further, the stability constants of the 1•M2+ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the series of Cu2+ < Ba2+ < Zn2+ < Ni2+ < UO22+ < Co2+ < Mn2+ < Cd2+ < Ca2+ < Pb2+.

Extraction and DFT Study on the Complexation of the TRIS+ Cation with a Hexaarylbenzene-Based Receptor.

From extraction experiments and -activity measurements, the exchange extraction constant corresponding to the equilibrium TRIS+(aq) + 1.Cs+(nb) <-> 1.TRIS+(nb) + Cs+(aq) taking place in the two-phase water-nitrobenzene system (TRIS+ = (HOCH2)3C-NH3+, 1 = hexaarylbenzene - based receptor; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (TRIS+, 1.Cs+) = -2.0 ± 0.1. Further, the stability constant of the hexaarylbenzene - based receptor .TRIS+ complex (abbrev. 1.TRIS+) in nitrobenzene saturated with water was calculated for a temperature of 25 °C : log ßnb (1.TRIS+) = 6.0 ± 0.2. By using quantum mechanical calculations, the most probable structure of the 1.TRIS+ complex species was solved. In this complex having C3 symmetry, the cation TRIS+ synergistically interacts with the polar ethereal oxygen fence and with the central hydrophobic benzene bottom via cation - π interaction.

Synergistic extraction of calcium and strontium into nitrobenzene by using hydrogen dicarbollylcobaltate and 1,2-bis(diphenylphosphino)ethane dioxide.

Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B-) in the presence of 1,2-bis(diphenylphosphino)ethane dioxide (DPPEtDO, L) has been investigated. The equilibrium data have been explained assuming that the species HL+, HL+2, ML2+2 and ML2+3 (M2+ = Ca2+, Sr2+) are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined. In the considered nitrobenzene medium, it was found that the stability constants of the complexes CaL2+2 and CaL2+3 , where L is DPPEtDO, are somewhat higher than those of the corresponding complex species SrL2+2 and SrL2+3 with the same ligand L.