Giancarlo Franchini

Electronic Properties and Crystal Structure of Aqua(1,10‐phenanthroline)(oxalato‐ O1O2)copper(II) monohydrate

Abstract The compound aqua(1,10-phenanthroline)(oxalato-O1O2) copper(II)monohydrate was synthesized and characterized by spectroscopy, thermal analysis, EPR and structural measurements. The crystal and molecular structure, refined to the final R = 4.28% (Rw = 4.52%) value, shows a monomeric nature. Copper coordination is 4 + 1 in a slight distorted square pyramidal geometry, with a water oxygen atom in the apical position, at 2.237(4) A from the metal atom. At 4.44 A from copper lies a lattice water molecule, linked to the former by a hydrogen bond.

Interaction between aqueous chromium solutions and layer silicates

Abstract The interactions between Cr in aqueous solutions and phyllosilicates were studied to determine: (a) the amount of Cr(VI) to Cr(III) reduction in aqueous solutions by Fe(II)-bearing phyllosilicates; (b) the removal of the Cr species from solution by interaction with phyllosilicates, as a function of Cr(III) concentration and anionic environment. Chlorite, corrensite and montmorillonite were reacted with solutions containing Cr(VI) (1.62×10 −3 N, 5.77×10 −3 N and 1.32×10 −1 N, respectively). The sorption/desorption of Cr(III) by saponite was investigated in different anionic environments (Cl − , NO − 3 and CH 3 COO − ) and at different initial Cr(III) concentrations (3.21×10 −3 N, 5.49×10 −3 N and 8.49×10 −3 N). The extent of Cr(VI) reduction and the amount of Cr removed by phyllosilicates were measured by analysis of the liquid portion separated by centrifugation after controled periods of exposure. The minerals were studied by chemical, thermal and X-ray powder diffraction analyses. The results show that: (i) Fe(II)-bearing phyllosilicates sorb Cr and reduce Cr(VI) to Cr(III); (ii) the extent of reduction depends on the solution concentration and on mineral crystal chemistry; (iii) Cr(III) sorption isotherms show that the degree of uptake depends both on the initial concentration of metal in solution and on the anionic environment, the order of effectiveness being Cl − ≅NO − 3 >CH 3 COO − ; (iii) Cr(III) is retained in the mineral substrate and its release is difficult.

Dithio-oxamides as ligands: crystal structures and vibrational analyses of bis(N,N′-dicyclohexyldithio-oxamidato)palladium(II), bis(N,N′-dibenzyldithio-oxamide) copper(II) diperchlorate, and dichloro(N,N′-dimethyldithio-oxamide) zinc(II) and the carbon-13 nuclear magnetic resonance spectra of related compounds

Three N,N′-disubstituted dithio-oxamide metal complexes [Pd(Hdcdto)2], [Cu(H2dbzdto)2][ClO4]2, and [Zn(H2dmdto)Cl2](H2dcdto, H2dbzdto, and H2dmdto =N,N′-dicyclohexyl-, N,N′-dibenzyl-, and N,N′-dimethyl-dithio-oxamide respectively) have been prepared and their crystal and molecular structures determined for the first time. In all cases the N,N′-disubstituted dithio-oxamides act as S,S′-chelating ligands. The PdII and CuII ions show nearly idealized square-planar S4 co-ordination, and the ZnII ion a distorted tetrahedral S2Cl2 co-ordination geometry. The co-ordination ability of the organic ligands and the conformations of their chelate rings are discussed. The i.r. spectra of the complexes are discussed and compared with analogous compounds. The 13C n.m.r. spectra of related complexes have been recorded in the solid state and in solution. E.s.r. spectra of a series of copper(II) complexes are also discussed in the light of the covalent strength of the ligands.

Refractive Properties of Binary Mixtures Containing N,N- Dimethylformamide + 2-Methoxyethanol or 1,2-Dimethoxyethane

Abstract Refractive index (n) and related properties such as molar refraction (R) have been investigated for DMF + ME and DMF+DME binary mixtures over the entire composition range, at 15 different temperatures in the range 0 ≤ t/°C ≤ 70. Some relationships have been applied to study the dependence of the measured and derived quantities by temperature and composition. Furthermore, the excess functions n E, R E and the excess Kirkwood correlation parameters Δg have been examined, in order to identify the presence of solvent-cosolvent adducts in these binary mixtures. The results obtained have been interpreted on the basis of specific intermolecular interactions between different species.

Interaction of exchanged Zn2+-montmorillonite with alkaline and earth alkaline cations

Abstract Desorption of Zn2+ by montmorillonite in alkaline and earth alkaline environments was carried out at room temperature and at pH 6.0 using the following techniques: a combination of analytical methods to determine the variation of montmorillonite chemical composition, X-ray powder diffraction (at controlled relative humidity and at controlled temperature in the range 50°C≤T≤400°C) and thermal analysis. The desorption isotherms clearly show that some of the Zn2+ cations are retained in the layers, the proportion being greater when the montmorillonite is treated with Na+ and smaller when treated with Mg2+. The d(001) basal spacing, for samples teated with Na+-K+ and Na+-Ca2+ mixed solutions, appears to be mainly affected by the first appearance of K+ and Ca2+. Differential thermal analyses of Zn2+-exchanged samples shows two dehydroxylation reactions at about 380 and 650°C which emphasized that Zn2+ is differently bonded in the layers and hence differently released.

Conductivity of tetraphenylphosphonium bromide in 2-methoxyethanol–water

Thermodynamic properties from conductance data are reported for solutions of Ph4PBr in 2-methoxyethanol–water binary solvent mixtures, at 19 temperatures in the range –10 to +80 °C and for six mixtures in the composition range 0.1865 ⩽X1⩽ 1. The experimental conductivity values were analysed by the Fuoss–Hsia equation, and the salt was found to be associated to some extent in these mixtures. The experimental dissociation constant (K) of the ion pair for this electrolyte has been used to test some empirical equations representing the functions K=K(T), K=K(X1) and K=K(T, X1).

Viscosities of 1,2-Ethanediol-2-Methoxyethanol solvent mixtures at various temperatures

Viscosities were measured for binary solvent mixtures of 1,2-ethanediol-2-methoxyethanol at 19 temperatures ranging from −10 to 80°C. Several different equations, such as those of Arrhenius, Waterton, and Williams et al., have been applied in order to establish the best regression fit for η as a function of temperature. For this binary solvent system, the viscometric properties are continuous but not a linear function of the mixture composition. The deviations of the excess viscosities from ideality were found to be useful in detecting the formation of solvent-cosolvent complex species and to evaluate their stoichiometrical composition.

An approach to the problem of the dependence of the dissociation constant of weak electrolytes on the temperature and on the solvent composition in the ethane-1,2-diol–2-methoxyethanol solvent system

This empirical approach to clarify the problem of the dependence of the dissociation constants of weak electrolytes on temperature and composition of mixed solvents systems (X) is applied to the dissociation constant of picric acid in ethane-1,2-diol, in 2-methoxyethanol and in their binary mixtures. The data utilized here are those of previous work (recalculated by means of the more accurate Fuoss–Hsia equation) integrated by the experimental data relative to three new mixtures. Two equations of the dependence of K on T and of K on X, respectively, are suggested and good accordance between experimental and calculated values is shown. Starting from the two above-mentioned equations, general empirical equations for the surface K(T, X) are proposed; the average difference between calculated and experimental K values is ca. 8 %. A three-dimensional plot of the function K=K(T, X) is presented. The proposed empirical models are compared to that obtained for the previously studied ethane-1,2-diol–water solvent system and advantages and limitations of the models are discussed.