The stability constants for M n+ -tricine binary complexes (1:1 and 1:2), where M n+ ) Th 4+ , Ce 3+ , La 3+ , and UO 2 2+ , have been determined pH-metrically in aqueous media at 25 °C and in the presence of 0.10 mol dm -3 (KNO 3 ). The binary Th-tricine (1:1) complex was studied in the presence of different organic solvents as well as in the presence of different ratios of dioxane and at different temperatures. The calculated stability constants have been discussed in terms of the nature of both the metal ion and tricine. It is suggested that tricine may act as a tridentate as well as a bidentate ligand. Solvent basicity and proportion in addition to the differences in stabilization of the free base by hydrogen bonding with solvent molecules as well as the electrostatic effect are the major factors responsible for the observed high stability of the Th-tricine binary complex. The thermodynamic parameters (∆H, ∆G, and ∆S) for the formation of 1:1 Th-tricine complex in the presence of 40% (w/w) dioxane at different temperatures (5-45 °C) were calculated.
Mixed-ligand complexes of CoII, NiII, and
CuII with dicarboxylic amino acids (aspartic and glutamic
or
H2ADA) as primary ligands and 8-hydroxyquinoline as a
secondary ligand were prepared and characterized. Formation constants of the different complexes were
determined acidimetrically at 25 °C and at
ionic strength I = 0.1 mol dm-3
(KNO3) and were discussed in terms of the nature of both
the metal ion
and the ligand used. The thermodynamic functions (ΔH,
ΔG°, and ΔS°) associated with the
formation of
[MII + (HADA)1- +
8-hydroxyquinoline] complexes were also calculated and
discussed.
ABSTRACT:Preoriented poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (Nodax™) films were obtained via the drawing of films to prestretching ratios ranging from 200 to 1000%. As expected, preorientation resulted in substantial improvements in the mechanical properties of the films from the corresponding increases in the amount and nature of the crystallinity present. Stress-strain curves in elongation showed a yield peak, which was relatively broad for the unoriented samples but became sharper, with a well-defined neck, as the extent of preorientation was increased. In addition, the preoriented films had higher modulus, toughness, yield stress, and tensile strength values. The attribution of these changes in the mechanical properties to changes in the crystallinity was supported by X-ray diffraction measurements.
The stability constants of complexes of N- [(tris-hydroxymethyl)methyl]glycine (Tricine) with the transition metal ions Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ were studied potentiometrically in the presence of (0.02, 0.05, 0.10, and 0.15) mol dm -3
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