1,720,986 research outputs found
Interaction of MO2++ ( M = U and Pu ) Ions with 5-Sulphosalicylic Acid in Aqueous Solution.
No full textIn aq. solns. with ionic strength of 1M (Na+, H+, ClO4-) at 20°, the stability consts. were log β = 11.30, 2.32, 10.30, and 9.24 for H+ + L3- ↔ HL2- (H3L = 5-sulfosalicylic acid), H+ + HL2- ↔ H2L-, UO22+ + L3- ↔ UO2L-, and PuO22+ + L3- ↔ PuO2L-, resp
Uranyl(VI) Complexes of 3-Aminopropanoic Acid and 4-Aminobutanoic Acid in Aqueous Solution: a Potentiometric and Calorimetric Study.
No full textActinide Complexes in Aqueous Solution.
No full textStability consts. and thermodn. of coordination of actinides in aq. soln. are reviewed with 25 refs
Complexation of Eu(III) with alkyl-substituted malonamides in acetonitrile.
No full textThe complexation of Eu(III) with a series of alkyl-substituted malonamide ligands was studied in organic solvents using calorimetry, FT-IR and luminescence spectroscopy. The formation constants were determined in acetonitrile containing small amounts of dimethyl sulfoxide. The effects of substitution on the nitrogen atoms as well as on the central carbon atom were evaluated. For the substitution on the nitrogen atoms, the formation constants decrease in the order: N,N,N',N'-tetramethylmalonamide (TMMA) > N,N'-dibutyl-N,N'-dimethylmalonamide (DMDBMA) > N,N,N',N'-tetrahexylmalonamide (THMA) > N,N,N',N'-tetraisopropylmalonamide (TiPMA). For substitution on the central carbon atom, the formation constants decrease in the order: N,N,N',N'-tetrahexyl-2-methylmalonamide (MeTHMA) > N,N,N',N'-tetrahexylmalonamide (THMA) > N,N,N',N'-tetrahexyl-2,2-dimethylmalonamide (DMeTHMA). These orders are discussed in terms of the steric effect and the ligand basicity
Thermodynamic Properties of Actinide Complexes. Uranyl(VI)- and Thorium(IV)- Glycine Systems. P. Di Bernardo, A. Cassol, G. Tomat, A. Bismondo, and L. Magon. Thermodynamics of the Complex Formation between Thorium(IV) and some Polydentate Ligands in Aqueous Solution. J. Chem. Soc. Dalton Trans., 733-735 (1983).
No full textPotentiometric and calorimetric investigations of uranyl(VI) and Th(IV) complexes with glycine were carried out in 1.00 M aq. NaClO4 at 25 °C. The treatment of the exptl. data has shown that in the examd. systems the glycine acts as unidentate ligand through the carboxylate group, while the amino group is not involved in coordination. The values obtained for the stability consts. and for the heat and entropy changes are discussed
Complexation of uranium(VI) with acetate at variable temperatures
No full textThe complexation between uranium(VI) and acetate in 1.05 mol kg(-1) NaClO4 was studied at variable temperatures (25, 35, 45, 55 and 70 degreesC). The formation constants of three successive complexes, UO2 (OOCCH3)(+), UO2 (OOCCH3)(2) and UO2 (OOCCH3)(3)(-), and the molar enthalpies of complexation were determined by potentiometry and calorimetry. Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) provided structural information to identify the coordination modes of the acetate in the complexes in solution, which helped to interpret the trends in the enthalpy and entropy of the complexation. The effect of temperature on the stability of the complexes is discussed in terms of the electrostatic model
Complexation of thorium(IV) by tris((2,3-dihydroxybenzylamino)ethyl)amine—a new strong chelating agent
No full textThe interaction of thorium(IV) with tris((2,3-dihydroxybenzylamino)ethyl)amine (TRENCAT) has been investigated by means of potentiometric measurements in an aqueous solution of 0.1 mol dm(-3) sodium perchlorate at 25 degrees C. The formation of a chelate structure, as well as of protonated compounds has been observed. The values of the formation constants of these complexes are reported
Complexation of uranium(VI) and samarium(III) with oxydiacetic acid: Temperature effect and coordination modes
No full texthe complexation of uranium(VI) and samarium(III) with oxydiacetate (ODA) in 1.05 mol kg(-1) NaClO4 is studied at variable temperatures (25-70 degreesC). Three U(VI)/ODA complexes (UO2L, UO2L22-, and UO2HL2-) and three Sm(III)/ ODA complexes (SmLj(3-2j)+ with j = 1, 2, 3) are identified in this temperature range. The formation constants and the molar enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) and samarium(111) with oxydiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropy of complexation at higher temperatures that exceeds the increase in the enthalpy of complexation. The values of the heat capacity of complexation (DeltaC(p)degrees in J K-1 mol(-1)) are 95 +/- 6, 297 +/- 14, and 162 +/- 19 for UO2L, UO2L22-, and UO2HL2-, and 142 +/- 6, 198 +/- 14, and 157 +/- 19 for SmL+, SmL2-, and SmL33-, respectively. The thermodynamic parameters, in conjunction with the structural information from spectroscopy, help to identify the coordination modes in the uranium oxydiacetate complexes. The effect of temperature on the thermodynamics of the complexation is discussed in terms of the electrostatic model and the change in the solvent structure
Thermodynamic Studies of the Complexation between Neodymium and Acetate at Elevated Temperatures
No full textComplexation of neodymium (III) with acetate in 2.2 mol-kg(-1) NaClO4 solution was studied at elevated temperatures (45 and 70 degreesC) by potentiometry, calorimetry, and optical spectroscopy. The formation constants of the consecutive complexes, Nd(OOCCH3),(2+) Nd(OOCCH3)(2)(+), and Nd(OOCCH3)(3), and the molar enthalpies of complexation at these temperatures were determined. The stability of the three complexes increases with increased temperatures, because of increased positive entropy change at higher temperatures, which exceeds the increased values of the positive (endothermic) enthalpy, The molar heat capacity changes of complexation DeltaC(p,m(MLj)) (J-K-1 -mol(-1)) for Nd(OOCCH3)(j)((3-j)+) in the temperature range from 25 to 70 degreesC were calculated to be: 102 +/- 13 (j = 1); 122 +/- 19 (j = 2); and 239 +/- 27 (j = 3). The effect of temperature on the complexation is discussed in terms of the electrostatic model
Calorimetric and spectroscopic studies of Eu(III) complexation with tetramethylmalonamide and tetramethylsuccinamide in acetonitrile and dimethylsulfoxide
No full textThe complexation of Eu(III) with two N,N,N',N'-alkyl-substituted diamide ligands, tetramethylmalonamide (TMMA) and tetramethylsuccinamide (TMSA), was studied in organic solvents using titration calorimetry, FT IR and luminescence spectroscopy. The formation constants and enthalpy changes of the complexation were determined in pure acetonitrile and in acetonitrile containing small amounts of dimethyl sulfoxide (DMSO). It was observed that TMMA forms stronger complexes with Eu(III) than TMSA in the latter systems, which is attributed to the structural difference between TMMA and TMSA and an entropy effect. The effect of Eu(III) solvation by DMSO on the formation of the Eu(III)-diamide complexes is also discussed
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