Mixed-Ligand Complexation of Zinc and Cobalt(II) Complexonates with Amino Acids in an Aqueous Solution

The formation of mixed-ligand complexes in the M(II)–Nta and Ida–L systems (M = Co, Zn; L = His, Orn, Lys, Gly, Im, en), where Ida and Nta are the residues of iminodiacetic and nitrilotriacetic acids, was studied by pH-metry, calorimetry, and NMR spectroscopy. The thermodynamic parameters (logK, Δ _r G⁰, Δ _r H, Δ _r S) of formation for these complexes were determined at 298.15 K and an ionic strength I = 0.5 (KNO3). The most probable pattern of coordination between a complexone and an amino acid in mixed-ligand complexes was revealed.     

Thermochemical study of the complex formation of copper(II) and nickel(II) iminodiacetates with amino acids in aqueous solutions

The formation of mixed-ligand complexes in the M(II)–Ida–L systems (M = Cu, Ni, L = His, Orn, Lys), where Ida is the iminodiacetic acid residue, was studied by pH-metry, calorimetry, and spectrophotometry. The thermodynamic parameters (logK, Δ_rG⁰, Δ_rH, Δ_rS) of formation of the complexes were determined at 298.15 K and the ionic strength I = 0.5 (KNO₃). The most probable mode of coordination of the chelating agent and the amino acid in the mixed-ligand complexes was elucidated.     

Thermodynamic characteristics of the formation of complexes of nickel(II) with L-homoserine

The formation of complexes of nickel(II) with L-homoserine at 298.15 K and ionic strengths I = 0.5, 1.0, and 1.5 (KNO₃) are investigated by potentiometry and calorimetry. Standard characteristics of studied equilibria (log K°, Δ_rG°, Δ_rH°, and Δ_rS°) are determined.     

Thermodynamic characteristics of complexation between Ho<Superscript>3+</Superscript> and ethylenediamine-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-disuccinic acid in aqueous solutions at 298.15 K

The thermodynamic characteristics of complexation between ethylenediamine-N,N'-disuccinic acid (H₄Y; EDDA) and Ho³⁺ ion were determined calorimetrically and potentiometrically at 298.15 K and ionic strengths of 0.1, 0.5, 1.0, and 1.5 (KNO₃). The logK, Δ_rG, Δ_rH, and Δ_rS values for the formation of HoY^– and HOHY complexes were calculated at the studied and zero ionic strength values. The changes in thermodynamic parameters of the reactions are discussed.     

Thermodynamic parameters of the formation of deprotonated single-ligand complexes in the Cu(II)−triglycine system in aqueous solutions

Heat effects arising from interactions between triglycine solutions and Cu(NO₃)₂ solutions are studied at 298.15 K and ionic strengths of 0.2 to 1.0 (KNO₃) via isothermal calorimetry. Using experimental data, enthalpies of formation are calculated for species CuH_?1L, CuH_?2L^?, and CuH_?3L^2?, along with Δ_rH°, Δ_rG°, and Δ_rS° of the complexation process. A relationship is revealed between the structures of deprotonated single-ligand triglycine complexes of Cu(II) and the thermodynamic parameters of their formation.     

Thermodynamic Parameters of the Complex Formation of Copper(II) Ions with L-Serine and L-Homoserine

Complex formation of copper(II) ions with L-serine and L-homoserine at 298.15 K and ionic strength I 0.5, 1.0, and 1.5 (KNO₃) has been studied by means of potentiometry and calorimetry. Standard thermodynamic parameters (log K⁰, Δ_rG⁰, Δ_rH⁰, Δ_rS⁰) of the studied coordination equilibriums have been calculated.     

Thermodynamic Characteristics of Reactions of the Formation of Complexes between Triglycine and Ni2<Superscript>+</Superscript> Ions in Aqueous Solution

Thermal effects of reactions of the formation of complexes between Ni(II) and triglycine are determined via direct calorimetry in aqueous solutions at 298.15 K and ionic strengths of 0.2, 0.5, and 1.0 (KNO₃). Standard thermodynamic characteristics (Δ_rH°, Δ_rG°, Δ_rS°) of complexing processes in the investigated systems are calculated. The structures of triglycinate complexes NiL⁺, NiH_?1L, NiL₂, NiH_?2L^2?₂, NiL^-₃, and NiH_?3L^4?₃ are introduced to compare the obtained values and data on the thermodynamics of triglycinate complexes of Ni(II).     

Homo- and heteroleptic mercury(II) complexes with monoamino complexones in aqueous solution

Reactions of mercury(II) with iminodiacetic (H₂Ida), 2-hydroxyethyliminodiacetic (H₂Heida), and nitrilotriacetic acids (H₃Nta) were studied by spectrophotometry and pH potentiometry. The resulting complexes included [HgIda], [Hg(OH)Ida]^?, [HgIda₂]^2?, [HgHeida], [Hg(OH)Heida]^?, [Hg(Heida)₂]^2?, [HgNta]^?, [HgNta₂]^4?, [Hg(Ida)Heida]^2?, [Hg(Ida)Nta]^3?, and [Hg(Heida)Nta]^3?. The logarithms of their stability constants calculated for I = 0.1 (NaClO₄) and T = 20 ± 2°C were 11.14 ± 0.07, 20.33 ± 0.08, 19.40 ± 0.10, 11.42 ± 0.04, 19.68 ± 0.11, 18.48 ± 0.09, 13.42 ± 0.05, 20.80 ± 0.08, 19.05 ± 0.06, 20.64 ± 0.11, and 20.53 ± 0.16, respectively. The experimental data were analyzed in terms of the mathematical models that predict the existence of a wide spectrum of complex species in solution and allow one to consider only those species that are sufficient for accurate reproduction of the observed pattern.     

Complex formation of magnesium and calcium ions with trimethylenediamine-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>’,<Emphasis Type="Italic">N</Emphasis>’-tetraacetic acid

Stability constants and heat effects of the formation reactions of magnesium and calcium trimethylenediaminetetraacetates at 298.15 K and ionic strength of 0.1, 0.5, and 1.0 (mol/L KNO₃) have been determined by means of potentiometry and calorimetry. Standard thermodynamic parameters (log K⁰, Δ_rG⁰, Δ_rH⁰, and Δ_rS⁰) of the studied equilibriums have been determined.     

Standard thermodynamic functions of complexation between copper(II) and glycine and L-histidine in aqueous solutions

The Cu²⁺–glycine–L-histidine system is studied calorimetrically at 298.15 K and an ionic strength of 0.2, 0.5, and 1.0 in aqueous solutions containing potassium nitrate. The standard thermodynamic parameters (Δ_rH°, Δ_rG°, Δ_rS°) of complexation processes are determined.     

Thermodynamics of the complex formation between Cu<Superscript>2+</Superscript> and triglycine in water–ethanol solutions at 298 K

Thermodynamic functions Δ_r H, Δ_r G, and TΔ_r S of the complex formation between Cu²⁺ and triglycine in water–ethanol solutions are calculated on the basis of calorimetric data. It is found that raising the concentration of EtOH results in a monotonic increase in the exothermic effect of [CuHL]²⁺ complex formation due to the weakening of triglycine solvation with the mutual compensation of ion solvation contributions. The enthalpy of [CuL]⁺ complex formation has an exothermic maximum at 0.1?0.3 molar fractions of EtOH due to competition between the solvation contributions from ions and ligands.     

Structure and energy study of β-diketonates. XV. Composition of superheated vapors and structure of monomeric molecules of <Emphasis Type="Italic">tris</Emphasis>-hexafluoroacetylacetonates of dysprosium,holmium, erbium,and ytterbium

The molecular structure of tris-hexafluoroacetylacetonates of dysprosium, holmium, erbium, and ytterbium (M(hfa)₃, M = Dy, Ho, Er, Yb) is studied in the framework of synchronous electron diffraction and massspectrometric experiment and also quantum-chemically. For all M(hfa)₃ complexes structural parameters r _a , r _g , and r _h1 are found. It is established that the coordination polyhedron LnO₆ has a configuration of D ₃ symmetry. In experiments on superheated vapors of Dy(hfa)₃, Ho(hfa)₃, and Yb(hfa)₃ the molecular forms present in the vapor at different degrees of superheat are determined.     

Co(II) and Ni(II) complexes incorporating <Emphasis Type="Italic">N</Emphasis>-acetimidoylacetamidine ligand: Synthesis and structures

Two new square planar complexes with the formula Co(L)₂ · CH₃OH (1) and Ni(L)₂ · CH₃OH (2) (HL = HN{C(Me)=NH}₂ = N-acetimidoylacetamidine) have been synthesized by solvothermal reactions in methanol/acetonitrile. N-acetimidoylacetamidine ligand was derived from the self-condensation reaction of acetonitrile, and the reaction was promoted by the cooperation of M(II) (M = Co in 1 and M = Ni in 2) with diphenylcarbazide. 1 and 2 are characterized by single crystal X-ray diffraction, elemental analysis and infrared spectrum. Both complexes crystallize in the monoclinic space group P2₁/c with a = 9.329(6) Å, b = 11.494(7) Å, c = 13.040(8) Å, β = 92.945(11)°, V = 1396.3(16) ų and Z = 4 for 1, and a = 9.323(4)Å, b = 11.512(5) Å, c = 13.020(6)Å, β = 92.819(7)°, V = 1395.7(10)ų and Z = 4 for 2.     

Thermochemical study of the complex formation of mercury(II) with nitrilotriacetic acid in an aqueous solution

The formation constant of the Hg(Nta) ₂ ^4? complex, where Nta^3? is the nitrilotriacetate ion, is determined by pH-metric titration at 298.15 K and ionic strength I = 0.5 (KNO₃) (logβ = 21.49 ± 0.10). The thermal effects for the formation of the Hg(NTa) _i2?3i complexes (i = 1, 2) are determined by a direct calorimetric method (?56.69 ± 1.04 and ?85.88 ± 1.32 kJ/mol for i = 1 and 2, respectively).     

Synthesis,properties, and crystal and molecular structure of potassium nitrilotriacetatodihydroxogermanate(IV) K[Ge(Nta)(OH)<Subscript>2</Subscript>] · H<Subscript>2</Subscript>O

The complex K[Ge(Nta)(OH)₂] · H₂O(H₃Nta is nitrilotriacetic acid) was obtained and studied by IR spectroscopy, thermogravimetry, X-ray powder diffraction, and X-ray crystallography. Crystals of the complex are monoclinic: a = 9.195(3) Å, b = 10.9805(19) Å, c = 10.661(3) Å, β = 95.53(3)°, V = 1071.3(5) ų, Z = 4, space group Cc, R = 0.0560 based on 1335 reflections with I > 2σ(I). The compound is composed of complex anions [Ge(Nta)(OH)₂]^?, K⁺ cations, and water molecules of crystallization. The coordination polyhedron of the germanium atom of the anion is a distorted octahedron composed of the nitrogen atom (Ge-N, 2.080(7) Å) and three carboxylic oxygen atoms (av. Ge-O, 1.931(7) Å) of three acetate branches of the completely deprotonated tetradentate ligand Nta^3? and two hydroxyl oxygen atoms (av. Ge-O, 1.791(8) Å). In the crystals, complex anions, cations, and crystallization water molecules are linked by hydrogen bonds to form a framework.     

Crystal structure of barium bis(nitrilotriacetato)cobaltate(III), Ba<Subscript>3</Subscript>[Co(Nta)<Subscript>2</Subscript>]<Subscript>2</Subscript> · 10H<Subscript>2</Subscript>O

Crystals of Ba₃[Co(Nta)₂]₂ · 10H₂O (Nta^3? is the ion of nitrilotriacetic acid) are obtained (monoclinic crystal system, a = 17.094(3), b = 13.1873(13), c = 21.490(3) Å, β = 98.457(18)°, Z = 4, space group I2/c). The crystal structure of the compound is determined by X-ray diffraction analysis. The crystals consist of the Ba²⁺ cations, water molecules, and [Co(Nta)₂]^3? anions in which the donor N and 2O atoms of each Nta^3? ion are located at opposite faces of the coordination octahedron. The Co(1, 2) atoms are arranged in the inversion centers. The Ba atoms of the complexes form an intricate three-dimensional framework. One of the two crystallographically nonequivalent complexes binds eight Ba atoms, and another one binds six Ba atoms. The coordination number of the Ba(1) atoms (in the general position) is nine (three O atoms of water molecules and six O atoms of the carboxyl groups of five complexes), and that of the Ba(2) atoms (on the 2 axis) is 6 (two O atoms of water molecules and four O atoms of the carboxyl groups of four complexes).     

Structure and properties of the volatile isomers of bis(1,1,1-trifluoro-5,5-dimethylhexane-2,4-dionato) of platinum(II)

In the work, isomeric complexes of platinum(II) with the (ptac)^–1 pivaloyltrifluoroacetonate ion (Pt((CH₃)₃–CO–CH–CO–CF₃)₂) are studied. The synthesis and chromatographic separation of Pt(ptac)₂ isomers are described, TGA data for the separated isomers are given, and the crystal structures of the solid phases are studied. The cis-Pt(ptac)₂ complex crystallizes in the space group P-1, a = 10.7091(4) Å, b = 12.7787(6) Å, c = 16.0154(8) Å, α = 92.389(2)°, β = 90.868(2)°, γ = 112.1260(10)°, V = 2027.39(16) ų, Z = 4, d _calc = 1.918 g/cm³. The trans-Pt(ptac)₂ complex crystallizes in the space group C2/m, a = 13.3235(5) Å, b = 8.5515(3) Å, c = 9.6694(3) Å, β = 118.5880(10)°, V = 967.38(6) Å3, Z = 2, d _calc = 2.010 g/cm3. The structures of the complexes are molecular, the Pt atom has a square coordination of four oxygen atoms of two ligands; for cis-Pt(ptac)2, the Pt–Oav distance is 1.968 Å, for trans-Pt(ptac)2 it is 1.980 Å.     

Micromechanism of Cu and Fe alloying process on the martensitic phase transformation of NiTi-based alloys: First-principles calculation

Using first-principles pseudo-potential plane wave method, the formation enthalpy ΔH, binding energy ΔE, elastic constants, and electronic structure were calculated and analyzed carefully for NiTiX (X = Cu, Fe) shape memory alloy. The results show that the Cu or Fe element prefers to occupy the Ni site in the NiTi matrix phase respectively. Compared with the NiTi matrix phase, the ΔH, ΔE, c ₄₄ and c′ of NiTi (Cu) are similar to each other. However, the structural stability of the NiTi phase is improved obviously by the Fe alloying process. Simultaneously, the shear modulus c ₄₄ and c′ of NiTi (Fe) are larger than those of the NiTi matrix phase. Furthermore, Milliken population results indicate that Q _Cu–Ti is smaller than Q _Ni–Ti after the Cu alloying process, but Q _Fe–Ti is larger than Q _Ni–Ti. The electron density difference shows that some covalent bonding exists between Fe and Ti elements. Based on the upward analysis, the difference in the phase stability and elastic constants of NiTiX (X = Cu, Fe) is the substantial mechanism for the different M _s of NiTiX (X = Cu, Fe) although Cu or Fe substitutes for the same atom Ni elements in the NiTi matrix phase.     

A comparison of energy changes accompanying growth processes by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Calculations are made using the equations Δ_r G = Δ_r H ? TΔ_r S and Δ_r X = Δ_r H ? Δ_r Q where Δ_r X represents the free energy change when the exchange of absorbed thermal energy with the environment is represented by Δ_r Q. The symbol Q has traditionally represented absorbed heat. However, here it is used specifically to represent the enthalpy listed in tabulations of thermodynamic properties as (H _T  ? H ₀) at T = 298.15 K, the reason being that for a given substance TS equals 2.0 Q for solid substances, with the difference being greater for liquids, and especially gases. Since Δ_r H can be measured, and is tangibly the same no matter what thermodynamics are used to describe a reaction equation, a change in the absorbed heat of a biochemical growth process system as represented by either Δ_r Q or TΔ_r S would be expected to result in a different calculated value for the free energy change. Calculations of changes in thermodynamic properties are made which accompany anabolism; the formation of anabolic, organic by-products; catabolism; metabolism; and their respective non-conservative reactions; for the growth of Saccharomyces cerevisiae using four growth process systems. The result is that there is only about a 1% difference in the average quantity of free energy conserved during growth using either Eq. 1 or 2. This is because although values of TΔ_r S and Δ_r Q can be markedly different when compared to one another, these differences are small when compared to the value for Δ_r G or Δ_r X.     

Synthesis and crystal structures of the zinc(II) complexes with a tridentate Schiff base (1-pyridin-2-ylethylidene)pyridin-2-ylmethylamine

Two new isostructural zinc(II) complexes, [ZnCl₂(L)] (I) and [ZnBr₂(L)] (II), derived from the Schiff base ligand (1-pyridin-2-ylethylidene)pyridin-2-ylmethylamine (L), have been prepared and characterized by physicochemical methods and single-crystal X-ray crystallography. The crystal of I is monoclinic: space group P2₁/c, a = 11.699(3) Å, b = 8.460(2) Å, c = 14.766(3) Å, β = 99.686(3)°, V = 1440.6(6) ų, Z = 4. The crystal of II is monoclinic: space group P2₁/n, a = 8.166(2) Å, b = 15.153(3) Å, c = 11.966(2) Å, β = 96.964(2)°, V = 1469.7(5) ų, Z = 4. The geometry of the pentacoordinated zinc atoms in both complexes is best described as a square pyramid.