Solubility of some lanthanide sulfates in polycomponent systems containing H2SO4

Summary The paper presents data on the solubility of La, Ce, Pr, Nd sulfates in the polycomponent system La₂(SO₄)₃·8H₂O-Ce₂(SO₄)₃·8H₂O-Pr₂(SO₄)₃·8H₂O-Nd₂(SO₄)₃· 8H₂O-H₂SO₄-H₂O (at 25°C and 64°C) as well as in the same polycomponent system but in the presence of CaSO₄·2H₂O. The solubility of the sulfates — ocathydrates of Pr at 25°C and 64°C and of La and Ce at 64°C in tricomponent systemLn ₂(SO₄)₃·8H₂O-H₂SO₄-H₂O are also reported.

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Löslichkeit einiger Lanthanidsulfate in Mehrkomponenten-Systemen mit H₂SO₄

Zusammenfassung Die Arbeit präsentiert Daten für die Löslichkeit von La-, Ce-, Pr- und Nd-Sulfaten in den Vielkomponenten-Systemen La₂(SO₄)₃·8H₂O-Ce₂(SO₄)₃·8H₂O-Pr₂(SO₄)₃·8H₂O-Nd₂(SO₄)₃· 8H₂O-H₂SO₄-H₂O (bei 25°C und 64°C) sowie in den gleichen Systemen, jedoch in Anwesenheit von CaSO₄·2H₂O. Über die Löslichkeit von Sulfatoctahydraten von Pr bei 25°C und 64°C und von La und Ce bei 64°C in den Dreikomponenten-SystemenLn ₂(SO₄)₃·8H₂O-H₂SO₄-H₂O wird auch berichtet.

     

The role of TiO2 in the B2O3–Na2O–PbO–Al2O3 glass system

Optical and vibrational studies have been carried out on 60B₂O₃·(20−x)Na₂O·10PbO·10Al₂O₃:xTiO₂ (x=0, 1, 2, 3, 4, and 5 mol%) glasses, in order to understand the role of TiO₂ in the 60B₂O₃·20Na₂O·10PbO·10Al₂O₃ glass matrix. The X-ray patterns reveal homogeneous glasses over the entire compositional range. The absorption spectra show that the energy of the optical band gap (ΔE_opt) and Urbach's energy (E_U) decreases as TiO₂ content increases. The changes observed in the Raman and IR spectra are related to the BO₄→BO₃ back conversion effect and the appearance of “loose” BO₄⁻ groups. The data indicate that titanium ions act as a network modifier.     

Syntheses, crystal structures and vibrational spectra of KLn(SO4)2·H2O (Ln=La, Nd, Sm, Eu, Gd, Dy)

The potassium lanthanide double sulphates KLn(SO₄)₂·H₂O (Ln=La, Nd, Sm, Eu, Gd, Dy) were obtained by evaporation of aqueous reaction mixtures of rare earth (III) sulphates and potassium thiocyanate at 298 K. X-ray single-crystal investigations show that KLn(SO₄)₂·H₂O (Ln=Nd, Sm, Eu, Gd, Dy) crystallise monoclinically (Ln=Sm: P2₁/c, Z=4, a=10.047(1), b=8.4555(1), c=10.349(1) Å, wR2=0.060, R1=0.024, 945 reflections, 125 parameters) while KLa(SO₄)₂·H₂O adopts space group P3₂21 (Z=3, a=7.1490(5), c=13.2439(12) Å, wR2=0.038, R1=0.017, 695 reflections, 65 parameters). The coordination environment of the lanthanide ions in KLn(SO₄)₂·H₂O is different in the case of the Nd/Sm/Gd and the Eu/Dy compounds, respectively. In the first case the Ln atoms are nine-fold coordinated in contrast to the latter where the Ln ions are eight-fold coordinated by oxygen atoms. The vibrational spectra of KLn(SO₄)₂·H₂O and the UV-vis reflection spectra of KEu(SO₄)₂·H₂O and KNd(SO₄)₂·H₂O are also reported.     

Syntheses, crystal structures and optical spectroscopy of Ln2(SO4)3·8H2O (Ln=Ho, Tm) and Pr2(SO4)3·4H2O

The lanthanide sulphate octahydrates Ln₂(SO₄)₃·8H₂O (Ln=Ho, Tm) and the respective tetrahydrate Pr₂(SO₄)₃·4H₂O were obtained by evaporation of aqueous reaction mixtures of trivalent rare earth oxides and sulphuric acid at 300 K. Ln₂(SO₄)₃·8H₂O (Ln=Ho, Tm) crystallise in space group C2/c (Z=4, a_Ho=13.4421(4) Å, b_Ho=6.6745(2) Å, c_Ho=18.1642(5) Å, β_Ho=102.006(1) Å³ and a_Tm=13.4118(14) Å, b_Tm=6.6402(6) Å, c_Tm=18.1040(16) Å, β_Tm=101.980(8) Å³), Pr₂(SO₄)₃·4H₂O adopts space group P2₁/n (a=13.051(3) Å, b=7.2047(14) Å, c=13.316(3) Å, β=92.55(3) Å³). The vibrational and optical spectra of Ho₂(SO₄)₃·8H₂O and Pr₂(SO₄)₃·4H₂O are also reported.     

Synthesis and characterisation of TlLn(SO4)2·xH2O (Ln=La-Tb)

The compounds TlLn(SO₄)₂·2H₂OLn=La, Ce, Pr, Nd and Tl[Ln(SO₄)₂(H₂O)₃]·H₂OLn=Nd, Sm, Eu, Gd, Tb have been isolated from aqueous solutions of the corresponding sulfates. The dihydrates are all isomorphous and crystallize monoclinic, space groupP2₁/n,Z=4. The compounds which belong to the second type are also isomorphous and crystallize in monoclinic space groupP 2₁/c withZ=4.The dehydration has been studied by thermogravimetry, differential scanning calorimetry and isothermal weight change determination. The dihydrates dehydrate in a single step. For the tetrahydrates the reaction is more complex, however no intermediate phases could be isolated.The unit cell parameters, the dehydration temperatures and the dehydration enthalpies are correlated to the ionic radii ofLn ³⁺.

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Synthese und Charakterisierung von TlLn(SO₄)₂·xH₂O (Ln=La-Tb)

Zusammenfassung Die Verbindungen TlLn(SO₄)₂·2H₂OLn=La, Ce, Pr, Nd und Tl[Ln(SO₄)₂(H₂O)₃]·H₂OLn=Nd, Sm, Eu, Gd, Tb wurden aus wäßrigen Lösungen der entsprechenden Sulfate isoliert. Die Dihydrate sind alle isomorph und kristallisieren monoklin, RaumgruppeP 2₁/n,Z=4. Die Verbindungen des zweiten Typs sind auch isomorph und kristallisieren in der monoklinen RaumgruppeP 2₁/c mitZ=4.Die Dehydration wurde mit TG, DSC und dem isothermalen Gewichtsverlust untersucht. Die Entwässerung der Dihydrate verläuft in einer Stufe, die von Tetrahydraten aber in mehreren Stufen mit keiner isolierbaren Zwischenphase.Die Gitterkonstanten, die Dehydratations-Temperaturen und -Enthalpien wurden mit den Ionenradien vonLn ³⁺ korreliert.

     

Sodium and silver phosphate glasses doped with chlorides of Fe,Mn and Zn

A number of samples of sodium and silver phosphate glasses doped with various compositions of some transition metals viz. iron, manganese and zinc chlorides alongwith undoped samples of sodium and silver phosphate glasses were synthesized and characterized by X-ray diffraction, IR spectral, electrical conductivity and differential scanning calorimetry (DSC). The glass transition temperature (T _g) and crystallization temperature (T _c) values obtained from DSC curves were found to increase with increasing concentration of the dopant Fe/Mn/Zn chlorides in both sodium and silver phosphate glasses and the following sequence is observed: T _g(–FeCl₃)>T _g(–MnCl₂)>T _g(–ZnCl₂) T _c(–FeCl₃)>T _c(–MnCl₂)>T _c(–ZnCl₂) The increase in T _g and T _c values indicate enhanced chemical durability of the doped glasses. The electrical conductivity values and the results of FTIR spectral studies have been correlated with the structural changes in the glass matrix by the addition of different transition metal cations as dopants.     

Two Ce(SO4)2·4H2O polymorphs: Crystal structure and thermal behavior

Syntheses, crystal structures and thermal behavior of two polymorphic forms of Ce(SO₄)₂·4H₂O are reported. The first modification, α-Ce(SO₄)₂·4H₂O (I), crystallizes in the orthorhombic space group Fddd, with a=5.6587(1), b=12.0469(2), c=26.7201(3) Å and Z=8. The second modification, β-Ce(SO₄)₂·4H₂O (II), crystallizes in the orthorhombic space group Pnma, with a=14.6019(2), b=11.0546(2), c=5.6340(1) Å and Z=4. In both structures, the cerium atoms have eight ligands: four water molecules and four sulfate groups. The mutual position of the ligands differs in (I) and (II), resulting in geometrical isomerism. Both these structures are built up by layers of Ce(H₂O)₄(SO₄)₂ held together by a hydrogen bonding network. The dehydration of Ce(SO₄)₂·4H₂O is a two step (I) and one step (II) process, respectively, forming Ce(SO₄)₂ in both cases. During the decomposition of the anhydrous form, Ce(SO₄)₂, into the final product CeO₂, intermediate xCeO₂·yCe(SO₄)₂ species are formed.     

The crystal structure of Yb2(SO4)3·3H2O and its decomposition product, β-Yb2(SO4)3

Yb₂(SO₄)₃·3H₂O, synthesised by hydrothermal methods at 220(2) °C, has been investigated by single crystal X-ray diffraction. Yb₂(SO₄)₃·3H₂O crystallises in space group Cmc2₁ and is isostructural with Lu₂(SO₄)₃·3H₂O. The crystal structure has been refined to R₁=0.0145 for 3412 reflections [F_o>3σ(F)], and 0.0150 for all 3472 reflections. The structure of Yb₂(SO₄)₃·3H₂O is a complex framework of YbO₆ octahedra, YbO₈ and YbO₅(H₂O)₃ polyhedra and SO₄ tetrahedra. Thermal data shows that Yb₂(SO₄)₃·3H₂O decomposes between 120 and 190 °C to form β-Yb₂(SO₄)₃. The structure of a twinned crystal of β-Yb₂(SO₄)₃ was solved and refined using an amplimode refinement in R3c with an R₁=0.0755 for 8944 reflections [F_o>3σ(F)], and 0.1483 for all 16,361 reflections. β-Yb₂(SO₄)₃ has a unique structural topology based on a 3D network of pinwheels.     

The hydrothermal decomposition of calcium monosulfoaluminate 14-hydrate to katoite hydrogarnet and β-anhydrite: An in-situ synchrotron X-ray diffraction study

We apply in-situ synchrotron X-ray diffraction to study the transformation of calcium monosulfoaluminate 14-hydrate Ca₄Al₂O₆(SO₄)·14H₂O [monosulfate-14] to hydrogarnet Ca₃Al₂(OH)₁₂ on the saturated water vapor pressure curve up to 250 °C. We use an aqueous slurry of synthetic ettringite Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O as the starting material; on heating, this decomposes at about 115 °C to form monosulfate-14 and bassanite CaSO₄·0.5H₂O. Above 170 °C monosulfate-14 diffraction peaks slowly diminish in intensity, perhaps as a result of loss of crystallinity and the formation of an X-ray amorphous meta-monosulfate. Hydrogarnet nucleates only at temperatures above 210 °C. Bassanite transforms to β-anhydrite (insoluble anhydrite) at about 230 °C and this transformation is accompanied by a second burst of hydrogarnet growth. The transformation pathway is more complex than previously thought. The mapping of the transformation pathway shows the value of rapid in-situ time-resolved synchrotron diffraction.     

Thermal decomposition behavior of the rare-earth ammonium sulfate R2(SO4)3·(NH4)2SO4

Rare-earth ammonium sulfate octahydrates of R₂(SO₄)₃·(NH₄)₂SO₄·8H₂O (R=Pr, Nd, Sm, and Eu) were synthesized by a wet process, and the stable temperature region for the anhydrous R₂(SO₄)₃·(NH₄)₂SO₄ form was clarified by thermogravimetry/differential thermal analysis, infrared, Raman, and electrical conductivity measurements. Detailed characterization of these double salts demonstrated that the thermal stability of anhydrous R₂(SO₄)₃·(NH₄)₂SO₄ is different between the Pr, Nd salts and the Sm, Eu salts, and the thermal decomposition behavior of these salts was quite different from the previous reports.     

The crystal chemistry of four thorium sulfates

Four thorium sulfate compounds have been synthesized and characterized. [Th(SO₄)₂(H₂O)₇]·2H₂O (ThS1) crystallizes in space group P2₁/m, a=7.2488(4), b=12.1798(7), c=8.0625(5) Å, β=98.245(1)^o; Na₁₀[Th₂(SO₄)₉(H₂O)₂]·3H₂O (ThS2), Pna2₁, a=17.842(2), b=6.9317(8), c=27.550(3) Å; Na₂[Th₂(SO₄)₅(H₂O)₃]·H₂O (ThS3), C2/c, a=16.639(2), b=9.081(1), c=25.078(3) Å, β= 95.322(2)^o; [Th₄(SO₄)₇(OH)₂(H₂O)₆]·2H₂O (ThS4), Pnma, a=18.2127(9), b=11.1669(5), c=14.4705(7) Å. In all cases the Th cations are coordinated by nine O atoms corresponding to SO₄ tetrahedra, OH groups, and H₂O groups. The structural unit of ThS1 is an isolated cluster consisting of a single Th polyhedron with two monodentate SO₄ tetrahedra and seven H₂O groups. A double-wide Th sulfate chain is the basis of ThS2. The structures of ThS3 and ThS4 are frameworks of Th polyhedra and sulfate tetrahedra, and each contains channels that extend through the framework. One of the Th cations in ThS3 is coordinated by a bidentate SO₄ tetrahedron, and ThS4 is unusual in the presence of a pair of Th cations that share a polyhedral face.     

Synthesis and Structure of [Pd(NH3)4][cis-Pd(NH3)2(SO3)2][Pd(NH3)3(SO3)] · H2O

A new palladium compound [Pd(NH₃)₄][cis-Pd(NH₃)₂(SO₃)₂][Pd(NH₃)₃(SO₃)] · H₂O (I) was synthesized and its structure was studied by X-ray powder diffraction method. In the course of the synthesis, the initial trans-diamminesulfite anionic complex is transformed into the cis-configuration. Further heating in aqueous solution results in isomerization of a substance into a neutral complex [Pd(NH₃)₃(SO₃)]. Crystals I are triclinic: a = 10.3297(2) Å, b = 14.1062(3) Å, c = 6.8531(1) Å, = 101.36(0)°, = 92.74(0)°, = 92.71(0)°, space group P1¯. Structure I consists of the columns with alternating cis-[Pd(NH₃)₂(SO₃)₂]^2– and [Pd(NH₃)₃(SO₃)] complexes and [Pd(NH₃)₄]²⁺ ions between the columns.     

Investigations into bis(triphenylphosphine)copper(I) complexes with cyclic derivatives of methylpyruvate thiosemicarbazones

The syntheses of four compounds, obtained by the reaction of methylpyruvate thiosemicarbazone (Hmpt) and its methyl (Me-Hmpt) and allyl (Allyl-Hmpt) derivatives with bis(triphenylphosphine)copper(I) acetate, are reported. The compounds [Cu(PPh₃)₂(pt_c)(Hpt_c)]·H₂O (1), [Cu(PPh₃)₂(Me-pt_c)] (2), [Cu₂(PPh₃)₂μ-S(Me-pt)μ-S(Me-pt_c)]·H₂O (3) and [Cu(PPh₃)₂(Allyl-pt_c)] (4) [H₂pt = pyruvic acid thiosemicarbazone and Hpt_c = cyclized pyruvic acid thiosemicarbazone, Me = methyl and Allyl are radical substituents on the amino nitrogen] were characterized by elemental analysis, IR, ¹H NMR, and by X-ray crystallography. Compound 3 was also studied by EPR because of the presence in the compound of two copper atoms in two different oxidation states. During the complexation reaction, the thiosemicarbazone ligands tend to undergo a cyclization reaction that leads to the formation of a six-member heterocyclic ring. All four compounds present the [Cu(PPh₃)₂]⁺ fragment and constant but different coordination situations. Compound 1 contains two cyclic ligand molecules, one protonated and the other deprotonated, bound as monodentate through the sulfur. Compounds 2 and 4 present a single deprotonated cyclic SN bidentate ligand molecule, while compound 3 contains copper(I) and copper(II), and two ligand molecules, one of which is linear and behaves as SNO tridentate and the other is cyclic and behaves as bridging μSN.     

Coordination compounds of hydrazine derivatives with transition metals,XXIII cobalt(II) chelates of bis(N-salicylidene)dicarboxylic acid dihydrazides

The reaction of bis(N-salicylidene)dicarboxylic acid dihydrazides (H₄ Lig) with cobalt(II) salts was investigated. Chelates of the types Co(H₃ Lig)X ·nH₂O, Co₂(H₂ Lig)X ₂, Co₃(H₃ Lig)₂ X ₄, Co(H₂ Lig) ·nH₂O and Co(H₃ Lig)₂ ·nH₂O (X=Cl, Br, I or SCN) were isolated and characterized by their infrared and electronic spectra as well as their magnetic properties.

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Koordinationsverbindungen von Hydrazinderivaten mit Übergangsmetallen, 23. Mitt.: Kobalt(II)-Chelate von Bis(N-salicyliden)dicarbonsäuredihydraziden

Zusammenfassung Die Reaktion von Bis(N-salicyliden)dicarbonsäuredihydraziden (H₄ Lig) mit Kobalt(II)-Salzen ergab Chelate vom Typ Co(H₃ Lig)X ·nH₂O, Co₂(H₂ Lig)X ₂, Co₃(H₃ Lig)₂ X ₄, Co(H₂ Lig) ·nH₂O and Co(H₃ Lig)₂ ·nH₂O (X=Cl, Br, I oder SCN). Die Charakterisierung erfolgte mittels IR, Elektronenspektren und magnetischer Eigenschaften.

     

Sulfito- und Thiosulfato-Komplexe des Kobalts(III) mitα-Benzildioxim Überα-Dioximinkomplexe der Übergangsmetalle, 52. Mitt.

Some new ligand exchange reactions of [Co(diph·H)₂Cl(H₂O)] and [Co(diph·H)₂(SO₃)(H₂O)]^– complexes with N₃ ^–, S₂O₃ ^2– and with aromatic and heterocyclic amines were carried out. A series of derivatives of the types [Co(diph·H)₂(SO₃)X] ^n– (X=N₃ ^–, S₂O₃ ^2– oramine) and [Co(diph·H)₂(S₂O₃)₂]^3– were described and characterized. Some structural problems are resolved and discussed on the basis of UV and IR spectral data.     

Aqueous solubilities of praseodymium,europium, and lutetium sulfates

The aqueous solubilities of finely divided Pr₂(SO₄)₃·8H₂O(cr), Eu₂(SO₄)₃·8H₂O(cr), and Lu₂(SO₄)₃·8H₂O(cr) have been measured as a function of time at 25°C using isothermal saturation. Solubilities of the latter two salts showed a steady decrease with time, whereas Pr₂(SO₄)₃·8H₂O(cr) showed no such variation within the accuracy of the determinations. The turbidities of these filtered saturated solutions also decreased with time, and indicate that some colloidal rare earth sulfates were present. These colloidal particles (<0.2 m) have a large surface area, which contributes to the Gibbs energy of the solid phase, thus giving rise to enhanced solubilities. The micro-particles also grow with time, thereby reducing the surface area contribution to the Gibbs energy and also leaving fewer particles to pass through the filters. Extrapolation of solubilities to infinite time gives the solubilities of macrocurstalline Eu₂(SO₄)₃·8H₂O and Lu₂(SO₄)₃·8H₂O. Previous solubility data for Lu₂(SO₄)₃, at 20 and 40°C, yield an interpolated value at 25°C that is about 30% low. Densities were also measured at several concentrations of each salt.     

Syntheses and crystal structures of SmIII and ThIV complexes with macrocyclic cavitand cucurbituril

Slow evaporation of solutions of samarium nitrate and thorium chloride in hydrochloric acid containing the macrocyclic cavitand cucurbituril (C₃₆H₃₆N₂₄O₁₂) afforded crystals of the [{Sm(H₂O)₅(NO₃)}₂(C₃₆H₃₆N₂₄O₁₂)](NO₃)₄·6.5H₂O and [{Th(H₂O)₅Cl}₂(C₃₆H₃₆N₂₄O₁₂)]Cl₆·13H₂O complexes, respectively. The [Sm(C₃₆H₃₆N₂₄O₁₂)(H₂O)₅(SO₄)][Sm(H₂O)₅(SO₄)₂]·17H₂O complex was generated upon heating (130 °C) of a mixture of samarium sulfate, cucurbituril, and water in a sealed tube. X-ray diffraction analysis demonstrated that the metal atoms in these complexes are bound to the portal oxygen atoms of the cucurbituril molecules. In addition, the portal oxygen atoms of cucurbituril are linked to the coordinated H₂O molecules via hydrogen bonds.     

An aqueous thermodynamic model for Ca2+−SO 3 2− ion interactions and the solubility product of crystalline CaSO3·1/2H2O

The solubility of CaSO₃·1/2H₂O(c) was studied under alkaline conditions (pH>8.2), in deaerated and deoxygenated Na₂SO₃ solutions ranging in concentration from 0.0002 to 0.4M and in CaCl₂ solutions ranging in concentration from 0.0002 to 0.01M, for equilibration periods ranging from 1 to 7 days. Equilibrium was approached from both the over- and the under-saturation directions. In all cases, equilibrium was reached in <1 days. The aqueous Ca²⁺–SO ₃ ^2– ion interactions can be satisfactorily modeled using either ion-association or ion-interaction aqueous thermodynamic models. In the ion-association model, the log K°=2.62±0.07 for Ca²⁺+SO ₃ ^2– CaSO ₃ ⁰ . In the Pitzer ion-interaction model, the binary parameters (⁰) and (¹) for Ca²⁺–SO ₄ ^2– were used, and the value of (²) was determined from the experimental data. As expected given the strong association constant, the value of (⁰) was quite small (about –134). We feel a combination of the two models is most useful. The logarithm of the thermodynamic equilibrium constant (K°) of the CaSO₃·1/2H₂O(c) solubility reaction (CaSO₃·1/2H₂O(c)Ca²⁺+SO ₃ ²⁺ +0.5H₂O) was found to be –6.64±0.07.     

Evidence of 13 hybrid fluoroaluminates in the composition space diagram of the Al(OH)3–tren–HF–ethanol system

Thirteen phases are now evidenced in the composition space diagram of the Al(OH)₃–tren–HF–ethanol system at 190 °C. Solvothermal syntheses are performed under microwave heating. Six new organic–inorganic fluorides crystallise and their structures are determined: (H₃O)·[H₄tren]₂·(AlF₆)₃·6H₂O (P-1, Z = 2), [H₃tren]₂·(AlF₅(H₂O))₃·8H₂O (C2/c, Z = 8), [H₃tren]₄·(AlF₆)₂·(Al₂F₁₁)·(F)·10H₂O (P2₁/n, Z = 2), [H₃tren]₂·(Al₄F₁₈)·3.5H₂O (P6₃, Z = 2), [H₃tren]₂·(Al₄F₁₈) (P-1, Z = 1), and [H₃tren]₄·(Al₈F₃₅)·(OH)·H₂O (P-1, Z = 1). The existence domains are approximately located for all phases. Tren amine is tetraprotonated at high HF concentration, otherwise it is triprotonated. A protonated water cluster, H₃O⁺(H₂O)₆, appears in (H₃O)·[H₄tren]₂·(AlF₆)₃·6H₂O while a new Al₄F₁₈ unit, found in [H₃tren]₂·(Al₄F₁₈), is evidenced; it results from corner and edge sharing association of four AlF₆ octahedra. Finally, the structure of [H₃tren]₄·(Al₈F₃₅)·(OH)·H₂O revealed the largest known fluoroaluminate polyanion, built from eight vertex sharing AlF₆ octahedra, (Al₈F₃₅)¹¹⁻.     

Iron(III) complexes withN-Methyl-4-mercaptopiperidine

Summary Complexes of iron(III), containingN-methyl-4-mercaptopiperidine in its zwitterionic form (HRS), of stoichiometry Fe(HRS)₄XA₄ · nD, Fe(HRS)₃(BPh₄)₃ · 3DMF and (Fe(HRS)SO₄)₂SO₄ · 3MeOH · 2H₂O (X=Cl or NO₃; A=BPh₄ or PF₆; D=H₂O, MeOH or DMF) have been prepared and characterized by i.r. and electronic spectra, magnetic susceptibilities at room temperature and by cyclic voltammetry measurements.