G. Arena

Thermodynamic study on the formation of the cupric ion hydrolytic species

Abstract The formation constants of Cu(OH), Cu2(OH)2 and Cu3(OH)4 were determined by potentiometric measurements. The enthalpy changes were obtained by direct calorimetry. The species were individualized by statistic tests. The calculated entropy changes were correlated with the assumed structure of the species present in the solution.

Water-soluble calix[6]arenes. Characterization of 5,11,17,23,29,35-hexasulphonate-37,38,39,40,41,42-hexahydroxycalix[6]arene and thermodynamic study of proton complex formation

Abstract The title compound, synthesized by modifying the procedure described in literature, was characterized by NMR, IR, TG, LSIMS, ICP-AES and potentiometry, and found to be an octasodium salt. Its protonation constants were determined in aqueous solution at 25°C and I = 0.1 mol dm −3 (NaNO 3 ) and compared with literature data determined under similar conditions. Enthalpy and entropy values, determined calorimetrically under the same experimental conditions employed for the potentiometric measurements, together with NMR results, provide a detailed picture of the processes taking place in aqueous solution.

Coordination properties of dialkyltin (IV) in aqueous solution. Thermodynamic study of dimethyltin (IV) complexes with l-amino acids

Abstract The complex formation of dimethyltin (IV) ([SnMe2]2+) with alanine, phenylalanine, triptophane and valine has been investigated by means of potentiometry at 25 °C and I = 0.1 mol dm−3 (KNO3). The selection of the models and the calculation of stability constants have been performed collecting a large amount of data points and using three different computer programs. This procedure has made it possible to detect the species forming in low percentages. A comparison with monodentate and bidentate systems previously studied gives an indication as to the number and the nature of the donor atoms involved in the coordination.

Thermodynamics of copper(II) 2,2′-dipyridyl complexes in aqueous solution

Abstract The thermodynamic parameters for the chelation of cupric ion with 2,2′-dipyridyl have been redetermined at 25°C and I =0.1 M. Δ G values were obtained by potentiometry with a selective ion electrode and Δ H values by direct calorimetry. Similar studies have been made on the relative hydroxocomplexes. The data obtained are compared with those in the literature and the chelate effect of the heterocyclic diimine is described.

Mixed metal complexes in solution. Part 4. Formation and stability of heterobinuclear complexes of cadmium(II)-citrate with some bivalent metal ions in aqueous solution

SummaryThe systems, Cd-Ni-citrate, Cd-Mn-citrate and Cd-Zn citrate have been investigated pH-metrically at 25°C and I = 0.1 mol dm−3 (KNO3).As previously found for analogous citrate systems (namely for Cu-Ni-, Cu-Zn- and Ni-Zn-citrate) the existence of mixed metal complexes of the type [MM′(cit)2H−2]4− has been shown. In addition, the species [MM′(cit)2H−1]3− was also found to be present for Cd-Ni- and Cd-Zn-citrate systems The significance of the formation of such species is discussed.The existence of mixed metal complexes is also discussed in connection with the transport and the absorption of metal ions in biological systems.

Co-ordination properties of dialkyltin(IV) in aqueous solution. Thermodynamics of complex formation with carboxylic acids

The complex formation of [SnMe2]2+ ion with acetate, malonate, and succinate ligands has been investigated by means of potentiometric measurements at 25 °C and I= 0.1 mol dm–3(KNO3). Values of ΔH⊖ and ΔS⊖ have been obtained by means of calorimetric titrations. On the basis of these values, bonding details have been inferred for the major species. The thermodynamic data are also discussed in view of the cis-trans disposition of the alkyl groups.

Potentiometric investigation of simple and mixed complexes of cupric ion in aqueous solution

Abstract Simple and mixed complexes of copper(II) with 2,2′-dipyridyl and oxydiacetic or thiodiacetic acid have been tnvestigated at 25 δC in 0.1 M (NaClO 4 ) by potentiometric measurements Stabiliy constants for the systems CuL, CuL 2 , CuHL, Cu(dip)L, Cu- (dip)HL (where L is oxydiacetic or thiodiacetic acid and dip is 2,2′-dipyridyl) have been determined. Some considerations about the stability of these complexes are reported.

Copper(II) complexes with 2,2′-dipyridyl, 1,10-phenanthroline or 2,2′,2″-terpyridyl and bidentate or tridentate dicarboxylic acids

Abstract Mixed complexes of copper(II) with 2,2′-dipyridyl, 1,10-phenanthroline or 2,2′,2″-terpyridyl and some dicarboxylic acids having heteroatoms in their chains have been prepared and characterized. Infrared and electronic spectra are also presented and discussed.

Thermodynamic and spectroscopic investigation on Ni(II)pyridine mixed complexes with iminodiacetic, oxydiacetic and thiodiacetic acids in aqueous solution

The stability constants (I = 0.1 mol dm−3 K[NO3] and T = 25°C) of the ternary complexes of Ni(II) and pyridine (py) with iminodiacetic (IDA), oxydiacetic (ODA) and thiodiacetic (TDA) acids have been determined pH metrically in aqueous solution. Electronic and PMR spectra have been carried out. In every investigated complex, the Ni(II) ion reaches the hexacoordination. A general agreement between thermodynamic and PMR data has been observed in the evaluation of the effect of the formation of pyridine mixed complexes from the simple complexes of the three investigated chelating ligands.

Mixed complex formation of copper(II) with 2,2′, 2″-terpyridine and some tridentate ligands in aqueous solution

SummaryThe formation of copper(II) ternary complexes [Cu(tpy)(L)]∘ (tpy = 2,2′,2″-terpyridine; L = oxydiacetate, thiodiacetate, iminodiacetate or dipicolinate) has been studied by potentiometric measurements in aqueous solution at 25° and I = 0.1 mol dm−3 (NaNO3 or NaClO4). All the systems investigated also form protonated species of the [Cu(tpy)(L)H]+ type. The effect of the different heteroatoms (donor atoms) in the ligands L (i.e. O, S or N), other than oxygens of the carboxylic groups, on the stability of the mixed complexes has been evaluated and compared with the trends observed for the analogous complexes of copper(II) with 2,2′-bipyridine (bpy).The stabilization of ternary complexes of copper(II) with respect to the different coordination levels is also discussed.