The Thermodynamics of Copper (II) and Nickel (II)- Diamine Complex Formation in Aqueous Solution

This work describes the accurate measurement of the thermodynamic functions Delta G degree and Delta H degree for the step-wise coordination equilibria between each of the ions H+, Ni2+, Cu2+, and, a series of C1-substituted 1,2-diaminoethanes in aqueous solution. The study Involved. (a) The construction of a sensitive constant temperature environment calorimeter for measuring the enthalpy changes in the complex-formation reactions, (b) The rigorous calibration of an electrode system, incorporating a glass electrode, for the direct potentiometric measurement of equilibrium hydrogen ion concentrations in the solutions containing complex ions. The thermodynamic functions Delta G degree and Delta H degree led to accurate Delta S degree values for the step-wise complex-formation reactions. The thesis considers the contribution of the entropy of ligation to the stability of complex ions. The molar entropies of the complex ions have been calculated and their values considered with respect to the coordination number and the possible structure, degree of hydration and steric properties of the ions

The Thermodynamics of Copper (II) and Nickel (II)- Diamine Complex Formation in Aqueous Solution

This work describes the accurate measurement of the thermodynamic functions Delta G degree and Delta H degree for the step-wise coordination equilibria between each of the ions H+, Ni2+, Cu2+, and, a series of C1-substituted 1,2-diaminoethanes in aqueous solution. The study Involved. (a) The construction of a sensitive constant temperature environment calorimeter for measuring the enthalpy changes in the complex-formation reactions, (b) The rigorous calibration of an electrode system, incorporating a glass electrode, for the direct potentiometric measurement of equilibrium hydrogen ion concentrations in the solutions containing complex ions. The thermodynamic functions Delta G degree and Delta H degree led to accurate Delta S degree values for the step-wise complex-formation reactions. The thesis considers the contribution of the entropy of ligation to the stability of complex ions. The molar entropies of the complex ions have been calculated and their values considered with respect to the coordination number and the possible structure, degree of hydration and steric properties of the ions

Magnetic Properties of Iron(II) Near the ⁵T₂-₁A₁ Crossover

A series of iron(II) complexes which lie near the high spin-low spin crossover (FeL2X2,nH2O, where X is NCS or NCSe and L is a ring-substituted analogue of 1,10-phenanthroline or 2,2′-bipyridyl) have been prepared and their magnetic and spectroscopic properties investigated. Small modifications in the molecules are found to produce starting effects on the properties, and the various members of the series illustrate many kinds of “crossover” behaviour. Some of the complexes have nearly equienergetic high spin and low spin states, both of which are thermally populated while some exhibit complete transitions between the two spin states within very narrow temperature ranges; the behaviour of some of the complexes falls in between these two extremes, while others have temperature independent moments, intermediate between high and low spin values, attributable to a triplet ground state

Chemical Speciation of Environmentally Significant Metals with Inorganic Ligands Part 2: The Cu\u3csup\u3e2+\u3c/sup\u3e-OH\u3csup\u3e-\u3c/sup\u3e, Cl\u3csup\u3e-\u3c/sup\u3e, CO\u3csub\u3e3\u3c/sub\u3e\u3csup\u3e2-\u3c/sup\u3e, SO\u3csub\u3e4\u3c/sub\u3e\u3csup\u3e2-\u3c/sup\u3e, and PO\u3csub\u3e4\u3c/sub\u3e\u3csup\u3e3-\u3c/sup\u3e Systems (IUPAC Technical Report)

Complex formation between CuIIand the common environmental lig-ands Cl–, OH–, CO32–, SO42–, and PO43–can have a significant effect on CuIIspe-ciation in natural waters with low concentrations of organic matter. Copper(II)complexes are labile, so the CuIIdistribution amongst these inorganic ligands canbe estimated by numerical modeling if reliable values for the relevant stability(formation) constants are available. This paper provides a critical review of suchconstants and related thermodynamic data. It recommends values of log10βp,q,r°valid at Im= 0 mol kg–1and 25 °C (298.15 K), along with the equations and spe-cific ion interaction coefficients required to calculate log10βp,q,rvalues at higherionic strengths. Some values for reaction enthalpies, ∆rHm, are also reported whereavailable.In weakly acidic fresh water systems, in the absence of organic ligands, CuIIspeciation is dominated by the species Cu2+(aq), with CuSO4(aq) as a minorspecies. In seawater, it is dominated by CuCO3(aq), with Cu(OH)+, Cu2+(aq),CuCl+, Cu(CO3)OH–, Cu(OH)2(aq), and Cu(CO3)22–as minor species. In weaklyacidic saline systems, it is dominated by Cu2+(aq) and CuCl+, with CuSO4(aq) andCuCl2(aq) as minor species

Chemical Speciation of Environmentally Significant Metals: An IUPAC Contribution to Reliable and Rigorous Computer Modelling

The mobility and bioavailability of metal ions in natural waters depend on their chemical speciation, which involves a distribution of the metal ions between different complex (metal-ligand) species, colloid-adsorbed species and insoluble phases, each of which may be kinetically labile or inert. For example, in fresh water the metal ions are distributed among organic complexes (e.g., humates), colloids (e.g., as surface-adsorbed species on colloidal phases such as FeOOH), solid phases (e.g., hydroxide, oxide, carbonate mineral phases), and labile complexes with the simple inorganic anionic ligands commonly present in natural waters (e.g., for ZnII, the aqueous species, Zn2+, ZnOH+, Zn(OH)2(aq), Zn2OH3+, ZnSO4(aq), ZnCO3(aq)…)

Chemical Speciation of Environmentally Significant Metals with Inorganic Ligands. Part 3: The Pb\u3csup\u3e2+\u3c/sup\u3e + OH\u3csup\u3e–\u3c/sup\u3e, Cl\u3csup\u3e–\u3c/sup\u3e, CO\u3csub\u3e3\u3c/sub\u3e\u3csup\u3e2–\u3c/sup\u3e, SO\u3csub\u3e4\u3c/sub\u3e\u3csup\u3e2–\u3c/sup\u3e, and PO\u3csub\u3e4\u3c/sub\u3e\u3csup\u3e3–\u3c/sup\u3e Systems (IUPAC Technical Report)

Complex formation between PbII and the common environmental inorganic ligands, Cl–, OH–, CO32–, SO42–, and PO43–, can be significant in natural waters with low concentrations of organic matter. Numerical modeling of the speciation of PbII amongst these inorganic ligands requires reliable values for the relevant stability (formation) constants. This paper provides a critical review of such constants and related thermodynamic data. It recommends values of log10 βp,q,r° valid at Im = 0 mol kg–1 and 25 °C (298.15 K), along with the equations and empirical coefficients required to calculate log10 βp,q,r values at higher ionic strengths using the Brønsted–Guggenheim–Scatchard specific ion interaction theory (SIT). Some values for reaction enthalpies, ΔrH, are also reported. In weakly acidic fresh water systems (–log10 {[H+]/c°} < 6), the speciation of PbII is similar to that of CuII. In the absence of organic ligands, PbII speciation is dominated by Pb2+(aq), with PbSO4(aq) as a minor species. In weakly alkaline solutions, 8.0 < –log10 {[H+]/c°} < 9.0, the speciation is dominated by the carbonato species PbCO3(aq) and Pb(CO3)2 2–. In weakly acidic saline systems (–log10 {[H+]/c°} < 6), the speciation is dominated by PbCln (2–n)+ complexes, (n = 0–3), with Pb2+(aq) as a minor species. In this medium (and in seawater), the speciation contrasts with that of CuII because of the higher stability of the Pb2+-chlorido- complexes. In seawater at –log10 {[H+]/c°} = 8.2, the calculated speciation is less well defined, although it is clearly dominated by the uncharged species PbCO3(aq) (41 % of [Pb]T) with a significant contribution (16 %) from Pb(CO3)Cl– and minor contributions (5–10 %) from PbCln (2–n)+ , (n = 0–3) and Pb(CO3)2 2–. The uncertainty in calculations of PbII speciation in seawater arises from (a) the large uncertainty in the stability constant for the apparently dominant species PbCO3(aq), (b) the reliance on statistical predictions for stability constants of the ternary species Pb(CO3)Cl– and Pb(CO3)OH–, and (c) the uncertainty in the stability constant for PbCl4 2–, the available value being considered “indicative” only. There is scope for additional detailed high-quality measurements in the Pb2+ + CO3 2– + Cl– system

Chemical speciation of environmentally significant metals with inorganic ligands. Part 4: The Cd2+ + OH–, Cl–, CO32–, SO42–, and PO43– systems (IUPAC Technical Report)

The numerical modeling of Cd-II speciation amongst the environmental inorganic ligands Cl-, OH-, CO32-, SO42-, and PO43- requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log(10) beta(p,q,r) valid at I-m = 0 mol kg(-1) and 25 degrees C (298.15 K), along with the equations and empirical reaction ion interaction coefficients, Delta epsilon, required to calculate log(10)beta(p),(,q,r) values at higher ionic strengths using the Bronsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, Delta H-r, are reported where available. Unfortunately, with the exception of the Cd-II-chlorido system and (at low ionic strengths) the Cd-II-sulfato system, the equilibrium reactions for the title systems are relatively poorly characterized. In weakly acidic fresh water systems (-log(10){[H+]/c degrees} < 6), in the absence of organic ligands (e. g., humic substances), Cd-II speciation is dominated by Cd2+(aq), with CdSO4(aq) as a minor species. In this respect, Cd-II is similar to Cu-II [2007PBa] and Pb-II [2009PBa]. However, in weakly alkaline fresh water solutions, 7.5 < -log(10) {[H+]/c degrees} < 8.6, the speciation of Cd-II is still dominated by Cd2+(aq), whereas for Cu-II [2007PBa] and Pb-II [2009PBa] the carbonato-species MCO3(aq) dominates. In weakly acidic saline systems (-log(10) {[H+]/c degrees} < 6; -log(10) {[Cl-]/c degrees} < 2.0) the speciation is dominated by CdCln(2-n)+ complexes, (n = 1-3), with Cd2+(aq) as a minor species. This is qualitatively similar to the situation for Cu-II and Pb-II. However, in weakly alkaline saline solutions, including seawater, the chlorido-complexes still dominate the speciation of Cd-II because of the relatively low stability of CdCO3(aq). In contrast, the speciation of Cu-II [2007PBa] and Pb-II [2009PBa] in seawater is dominated by the respective species MCO3(aq). There is scope for additional high-quality measurements in the Cd2+ + H+ + CO32- system as the large uncertainties in the stability constants for the Cd2+-carbonato complexes significantly affect the speciation calculations