Synthesis and characterization of novel (<Emphasis Type="Italic">E</Emphasis>,<Emphasis Type="Italic">E</Emphasis>)-dioxime and its mono- and polynuclear metal complexes containing azacrown moieties

The novel (E,E)-dioxime,7,8-bis(hydroxyimino)-1,14-bis(monoaza[8]crown-6)-benzo[f]-4,11-dioxa-1,14-diazadecane[7,8-g]quinoxaline (H₂L), has been synthesized by the reaction of 6,7-diamino-1,12-bis(monoaza[18]crown-6)benzo[f]-4,9-dioxa-1,12-diazadecane (4) which has been prepared by the reduction of 6,7-dinitro-1,12-bis(mono-aza[18]crown-6)benzo[f]-4,9-dioxa-1,12-diazdecane (3) and cyanogendi-N-oxide. Mononuclear Ni^II and Cu^II complexes of H₂L have a metal:ligand ratio of 1:2 and the ligand coordinates through two hydroxyimino nitrogen atoms, as do most of the (E,E)-dioximes. The hydrogen-bridged Ni^II complex was converted into its BF ₂ ⁺ capped anologue by the reaction with BF₃ · Et₂O. The reaction of the Cu^II complex with 2,2′-dipyridyl as an end-cap ligand gave the homotrinuclear complex. Structures for the ligand and its complexes are proposed in accordance with elemental analysis, magnetic susceptibility measurements, ¹H, ¹³C-n.m.r, IR and MS spectral data.     

Synthesis and characterization of the [Cu(Cin2bda)2]ClO4 and [Cu(Ncin2bda)2]ClO4 complexes: Crystal structure of [Cu(Ncin2bda)2]ClO4

Two copper(I) complexes [Cu(Cin₂bda)₂]ClO₄ (I) and [Cu(Ncin₂bda)₂]ClO₄ (II) have been prepared by the reaction of the ligands N²,N²′-bis(3-phenylallylidene)biphenyl-2,2′-diamine (L¹) and N²,N²′-bis[3-(2-nitrophenyl)allylidene]biphenyl-2,2′-diamine (L²) and copper(I) salt. These compounds were characterized by CHN analyses, ¹H NMR, IR, and UV-Vis spectroscopy. The C=N stretching frequency in the copper(I) complexes shows a shift to a lower frequency relative to the free ligand due to the coordination of the nitrogen atoms. The crystal and molecular structure of II was determined by X-ray single-crystal crystallography. The coordination polyhedron about the copper(I) center in the complex is best described as a distorted tetrahedron. A quasireversible redox behavior was observed for complexes I and II. The article is published in the original.     

A vic -dioxime ligand bearing fluorescent coumarin moieties and its complexes; preparation,spectroscopy, and electrochemistry

The synthesis of a new vic-dioxime ligand, N,N′²-dihydroxy-O ¹,O ²-bis(4-methyl-2-oxo-2H-chromen-7-yl)oxalimidamid (LH₂) (1), bearing functional coumarins and its soluble mono- {Ni(II), Cu(II), Co(II)} and dinuclear {UO₂(II)} complexes are presented. The fluorescence properties due to the 7-hydroxy-4-methylcoumarin fluorophore, which is conjugated with vic-dioxime that functions as the MN₄ core of 1 and its complexes, are also reported. The formation of coordination complexes resulted in the blue shift in excitation spectrum and fluorescence quenching of 1. Both mononuclear {(LH)₂M, M=Ni(II), Cu(II), and Co(II)} and homodinuclear {(LH)₂(UO₂)₂(OH)₂)} complexes have been obtained with metal?:?ligand ratios of 1?:?2 and 2?:?2, respectively. The characterizations of the new compounds were made by elemental analysis, ¹H-NMR, FT-IR, UV-Vis, and LCMS data. Redox behavior of 1, involving oxime and coumarin moieties, and its complexes with Ni(II), Cu(II), Co(II) and UO₂(II) were investigated by cyclic voltammetry. The comparison of the electrochemical behavior of 1 with its complexes enabled us to identify metal-, oxime- and coumarin-based signals.     

The synthesis,characterization and spectral studies of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes with N,N-bis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl) methyl]amino}butyl) N′,N′-dihydroxyethanediimidamide

Co^II, Ni^II, Cu^II, Zn^II and Cd^II complexes of N,N-bis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl)methyl]amino}butyl)N′,N′-dihydroxyethanediimidamide (LH₂) were synthesized and characterized by elemental analyses, IR, ¹H- and ¹³C-NMR spectra, electronic spectra, magnetic susceptibility measurements, conductivity measurements and thermogravimetric analyses (TGA). The Co^II, Ni^II and Cu^II complexes of LH₂ were synthesized with 1?:?2 metal ligand stoichiometry. Zn^II and Cd^II complexes with LH₂ have a metal ligand ratio of 1?:?1. The reaction of LH₂ with Co^II, Ni^II, Cu^II, Zn^II and Cd^II chloride give complexes Ni(LH)₂, Cu(LH)₂, Zn(LH₂)(Cl)₂, Cd(LH₂)(Cl)₂, respectively.     

Alcohol-soluble functional vic-dioxime bearing alcoholhexylsulfanyl moieties: preparation, spectroscopy and electrochemistry

A new alcohol soluble functionalized vic-dioxime, bis-[(1-hydroxyhexyl)-(8,9-hydroxyimino)-7,10-dithiahexacosane (LH₂), and its alcohol-soluble mono and dinuclear complexes (Ni^II, Cu^II, Co^II, Mn^II, Pd^II and UO ₂ ^II ) have been prepared from 6-mercapto-1-hexanol and (E,E)-dichloroglyoxime under high dilution basic conditions. Reactive polyalcohol moieties appended at the periphery of the oxime containing two different heteroatoms (S-, O-), serve as a weak exocyclic binding sites for Pd^II and Ag^I metal ions and also provide solubility for the vic-dioxime complexes in low molecular-weight alcohols. Both mono-nuclear (LH)₂M and homodinuclear (LH)₂(UO₂)₂(OH)₂ and heterotrinuclear (LH)₂MM ₂ ^′ Xn, where M = Co^II M′ = Pd^II, X = Cl⁻, n = 4 and Ag^I X = NO ₃ ⁻ , n = 2) complexes have been obtained with a 1:2, 2:2, 3:2 metal/ligand ratio, respectively. Electronic spectra of the modified vic-dioximes exhibit monitorable changes in UV. All mono and dinuclear-complexes are soluble in common organic solvents. The elemental analysis, ¹H-n.m.r, i.r., u.v–vis, and f.a.b.–m.s data and by cyclic and differential pulse voltammetry measurements are presented.     

Synthesis,characterization, fluorescence and redox features of new <Emphasis Type="Italic">vic</Emphasis>-dioxime ligand bearing pyrene and its metal complexes

A new vic-dioxime ligand, N,N′-bis(aminopyreneglyoxime) (LH₂), and its copper(II), nickel(II) and cobalt(II) metal complexes were synthesized and characterized by elemental analyses, IR, UVVIS and ¹H and ¹³C NMR spectra (for the ligand). Mononuclear complexes were synthesized by a reaction of ligand (LH₂) and salts of Co(II), Ni(II), and Cu(II) in ethanol. The complexes have the metal-ligand ratio of 1: 2 and metals are coordinated by N,N′ atoms of vicinal dioximes. The ligand acts in a polydentate fashion bending through nitrogen atoms in the presence of a base, as do most vic-dioximes. Detection of a H-bonding in the Co(II), Ni(II), and Cu(II) complexes by IR revealed the square-planar MN₄ coordination of mononuclear complexes. Fluorescent properties of the ligand and its complexes arise from pyrene units conjugated with a vic-dioxime moiety. Fluorescence emission spectra of the ligand showed a drastic decrease in its fluorescence intensity upon metal binding. The electrochemical properties of the complexes were studied by the cyclic voltammetry technique. The nickel complex displayed an irreversible oxidation process while the copper complex exhibited a quasi-reversible oxidation and reduction processes based on the copper Cu(II)/Cu(III) and Cu(II)/Cu(I) couples, respectively.     

Synthesis and complexation of a novel soluble vic-dioxime with hydroxyethyl pendant arms

A new soluble vic-dioxime ligand namely 1,4-bis(2′-hydroxyethyl)-2,3-bis(hydroxyimino)-5,6-diphenylpiperazine, (LH₂) containing optically active centers has been prepared as a mixture of isomers from (CNO)₂ and N,N-bis(2-hydroxyethyl)stilbendiamine (1) which has been made by the reduction of the condensation of the product of benzaldehyde and 2-aminoethanol in the presence of aluminum amalgam. N,N-coordinated planar metal complexes of this ligand have been synthesized with Ni^II, Cu^II, Co^II, Pd^II and U^VIO₂. Oxidation of (LH)₂Co in the presence of a base, such as pyridine, leads to an octahedral complex (LH)₂CopyCl containing pyridine and chloride as axial ligands in addition to vic-dioxime ligands. The structures of the ligand and its complexes are proposed on the basis of elemental analysis, ¹H-n.m.r., mass, i.r. and u.v.–vis. spectral data. This revised version was published online in June 2006 with corrections to the Cover Date.     

Homo- and heteronuclear complexes of a new,vicinal dioxime ligand

A new symmetrical vicinal dioxime, N,N′-bis-{4-[[(2-hydroxyphenyl)methylene]hydrazinecarbonyl]phenyl}diaminoglyoxime (LH₄), was prepared by reacting anti-dichloroglyoxime with salicylaldehyde 4-aminobenzoylhydrazone. The reaction of ligand with Ni²⁺ salts gave mono-and homopentanuclear complexes, [Ni(LH₃)₂] and [Ni₅(LH)₂X₂]. Furthermore, heteropentanuclear complexes of dioxime ligand, [Cu₄Ni(LH)₂X₄], were prepared by the reaction of [Ni(LH₃)₂)] with Cu²⁺ salt and a monodentate ligand (X = SCN⁻, CN⁻, or N ₃ ⁻ ). The structures of both the new symmetrical vicinal dioxime and its complexes were identified by elemental analyses, IR, ¹H NMR, UV-VIS spectra, and magnetic susceptibility. The elemental analyses and spectral data indicate that the hydrazone side of ligand acts as a O,N,O′ tridentate and the fourth position is occupied with monodentate anion such as SCN⁻, CN⁻, N ₃ ⁻ .     

Manganese,cobalt and nickel complexes with a novel 17-membered macrocycle containing an N5 donor set

Summary The synthesis of a new macrocycle containing phenanthroline and pyridine subunits is described. The reaction of 2,9-bis(hydrazone)-1,10-phenanthroline with 2,6-bis-(bromomethyl) pyridine in the presence of Mn^II, Co^II or Ni^II ion templates leads to the isolation, in high yield, of the seven-coordinate complexes [M(L³)Br₂] (L³ = 4,5, 6,7,8,9-phenanthrolino-14,15,16-pyridino-1,2,5,8,11,12,15 heptaazacycloheptadecane,2,10-diene). The compounds were characterized by physical measurements, which indicated that in all the complexes the ligand is acting as a pentadentate N₅ chelating agent.     

Bimetallic complexes of a potentially pentadentate,acyclic, symmetrical compartmental Schiff base ligand that provides suitable topology for an exogenous bridge

The binucleating ligand LH₃, 2,6-diformyl-p-cresol-bis(phenylthioacetyldrazone), a Schiff base condensation product of 2,6-diformyl-p-cresol and phenylthioacetyldrazide forms complexes of the [M₂ClL] type with Co^II, Ni^II and Cu^II ions, which were characterized by elemental analysis, magnetic susceptibility, electronic spectra, molar conductance, i.r., n.m.r., e.p.r., t.g. and FAB mass spectral measurements. Sub-normal magnetic moments indicate the operation of antiferromagnetic coupling between the metal centres. The ligand and its copper complex show a pronounced fungistatic activity.     

Formation of polymeric chain assemblies of transition metal complexes with a multidentate Schiff-base

The new multidentate Schiff-base (E)-6,6′-((1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-ylidene))bis(4-methyl-2-((E)(pyridine-2-ylmethylimino)methyl)phenol) H₂L and its polymeric binuclear metal complexes with Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) are reported. The reaction of 2,6-diformyl-4-methyl-phenol with ethylenediamine in mole ratios of 2:1 gave the precursor 3,3′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1ylidene))bis(methan-1-yl-1-ylidene)bis(2-hydroxy-5-methylbenzaldehyde) W. Condensation of the precursor with 2-(amino-methyl)pyridine in mole ratios of 1:2 gave the new N₆O₂ multidentate Schiff-base ligand H₂L. Upon complex formation, the ligand behaves as a dibasic octadentate species with the involvement of the nitrogen atoms of the pyridine groups in coordination for all complexes. The mode of bonding and overall geometry of the complexes were determined through physico-chemical and spectroscopic methods. These studies revealed octahedral geometries for Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Cd(II) and Hg(II) complexes of general formulae [Cr₂^III(L)Cl₂]Cl₂, [Ni₂^II(L)(H₂O)₂]Cl₂ and [M₂(L)Cl₂] and five co-ordinate Zn(II) complex of general formula [Zn₂^II(L)]Cl₂.     

Synthesis,structural and catalytic activity of binaphthyl macrocyclic complexes

The binaphthyl macrocyclic ligand, N,N′-diethyl-[3,3′-(2,2′-dihydroxy-1,1′-binaphthyl)carboxamide]-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxylic acid (DDCDB), has been synthesized and investigated. The ligand (DDCDB) and its metal complexes involving Cu^II, Zn^II, UO ₂ ^II , Th^IV, Ce^III, Mo^VI and W^VI ions have been prepared and characterized by spectral (i.r., u.v.–vis.), elemental analyses, magnetic moments and thermal analyses measurements. DDCDB behaves as a tridentate ligand towards Cu^II, Zn^II and UO ₂ ^II ions coordinating via CO, NH and the deprotonated naphthyl OH groups in a ratio of 2:1 (M:L). On the other hand, DDCDB behaves in a bidentate manner coordinatingvia the NH and the deprotonated naphthyl OH groups only in case of the Th^IV, Ce^III, Mo^VI, and W^IV ions and in ratio 1:1 (M:L). Results of thermal measurements confirm the existence of solvent molecules inside and outside the coordination sphere. Th^VI complex has been applied for the hydrolysis of phosphodiester and the results show a significant rate enhancement of ~5.8 million fold with respect to the auto-hydrolysis of bis-(p-nitrophenyl) phosphate (BNPP) under the same conditions Also, Cu^II complex accelerates the photodegradation of the hazardous pollutant (acid green dye) in the presence of hydrogen peroxide by degrading 90% of the dye within 23 min.     

Investigation on the thermal decomposition some heterodinuclear NiII-MII complexes prepared from ONNO type reduced Schiff base compounds ( M II=ZnII, CdII)

N,N′-bis(salicylidene)-1,3-propanediamine (LH₂), N,N′-bis(salicylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH₂), N,N′-bis(salicylidene)-2-hydroxy-1,3-propanediamine (LOH₃), N,N′-bis(2-hydroxyacetophenylidene)-1,3-propanediamine (LACH₂) and N,N′-bis(2-hydroxyacetophenone)-2,2′-dimethyl-1,3-propanediamine (LACDMH₂) were synthesized and reduced to their phenol-amine form in alcoholic media using NaBH₄ (L^HH₂, LDM^HH₂, LOH^HH₂, LAC^HH₂ and LACDM^HH₂). Heterodinuclear complexes were synthesized using Ni(II), Zn(II) and Cd(II) salts, according to the template method in DMF media. The complex structures were analyzed using elemental analysis, IR spectroscopy, and thermogravimetry. Suitable crystals of only one complex were obtained and its structure determined using X-ray diffraction, NiLAC^H·CdBr₂·DMF₂, space group orthorhombic, Pbca, a=20.249, b=14.881, c=20.565 ? and Z=8. The heterodinuclear complexes were seen to be of [Ni·ligand·MX₂·DMF₂] structure (ligand=L^H2−, LDM^H2−, LOH^H2−, LAC^H2−, LACDM^H2−, M=Zn^II, Cd^II, X=Br⁻, I⁻). Thermogravimetric analysis showed irreversible bond breakage of the coordinatively bonded DMF molecules followed by decomposition at this temperature.     

Synthesis and characterization of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with acetylacetone bis-benzoylhydrazone and acetylacetone bis-isonicotinoylhydrazone

Summary Acetylacetone bis-benzoylhydrazone (PhCONHN=CMe)₂ CH₂(LH₂) and acetylacetone bis-isonicotinoylhydrazone (NC₅H₄CONHN=CMe)₂CH₂(LH₂) complexes of the types [ML] and [ML] (M = Co^II, Ni^II, Cu^II or Zn^II) have been prepared and characterized. All the complexes are non-electrolytes and the cobalt(II) complexes are lowspin, the nickel(II) complexes are diamagnetic and the copper(II) complexes are paramagnetic. The ligands chelate via two C=N groups and two deprotonated enolate groups. The e.s.r. spectra of the copper(II) complexes indicate a tetragonally distorted dimeric structure. The X-ray diffraction parameters for [CoL] and [NiL] correspond to a tetragonal crystal lattice.     

Synthesis,characterization and redox properties of a new vic-dioxime and its transition metal complexes

A novel vic-dioxime, 1,2 dihydroxyimino-1-p-tolyl-3-aza-6-morpholine heptane (LH₂) was prepared by reacting anti-p-tolylchloroglyoxime with 4-(3-aminopropyl)morpholine in absolute THF. Mononuclear complexes with a metal–ligand ratio of 1:2 were prepared using Co^II, Cu^II and Ni^II salts. The ligand and its complexes were characterized by elemental analyses, FT-IR, u.v.–vis., ¹H- and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.), and by cyclic voltammetry.     

Synthesis and spectral characterization of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,4- bis (2-carboxyaldehydephenoxy)butane and its CuII, NiII, PbII, CoIII and LaIII complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:15,16-tribenzo-9,15-dioxacycloheptadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine with 1,4-bis(2-carboxyaldehydephenoxy)butane. Then, its Cu^II, Ni^II, Pb^II, Co^III and La^III complexes were synthesized by the template effect by reaction of 2,6-diaminopyridine and 1,4-bis (2-carboxyaldehydephenoxy)butane and Cu(NO₃)₂ · 3H₂O, Ni(NO₃)₂ · 6H₂O, Pb(NO₃)₂, Co(NO₃)₂ · 6H₂O, La (NO₃)₃ · 6H₂O, respectively. The ligand and its metal complexes were characterized by elemental analysis, IR, ¹H- and ¹³C-n.m.r., UV-vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements and mass spectra. All complexes are diamagnetic and the Cu^II complex is binuclear. The Co^II complex was oxidised to Co^III.     

Synthesis,spectral, catalytic,and thermal studies of vanadium complexes with quadridentate schiff bases

The paper reports the synthesis and characterization of vanadium complexes of N,N′-(±)-trans-bis(2,4-dihydroxyacetophenone)-1,2-cyclohexanediamine (H₂L¹) and N,N′-(±)-trans-bis(2,4-dihyroxy-5-nitroacetophenone)-1,2-chyclohexanediamine (H₂L²). All the complexes were characterized by elemental analysis, magnetic susceptibility measurements, infrared and electronic spectra, and thermogravimetric analysis. The X-ray patterns of the [VO(L¹)] · H₂O (I) and [VO(L²)] · H₂O (II) complexes show the monoclinic system with the unit cell parameters a = 26.1352, b = 11.7149, c = 6.0401 β = 115.38° and a = 29.3787, b = 12.9398, c = 5.9175 β = 96.84°, respectively. The complexes I and II catalyze the oxidation of styrene in the presence of hydrogen peroxide.     

A novel (E,E)-dioxime and its mono-, di- and trinuclear complexes bearing tetradentate octyl sulfanyl phenylamino substituents. Synthesis,characterization and electrochemical properties of its transition metal complexes

A new vic-dioxime, 13,14-bis-(hydroxyimino)-9,12,15,18-diazadithiaoctacosane, has been synthesized from 2-octylsulfanylaminobenzene and (E,E)-dichloroglyoxime. Mononuclear transition metal complexes of Ni^II, Cu^II, Co^II and Fe^II have been prepared and were found to have a metal–ligand ratio of 1:2. The synthesis of di- and trinuclear complexes was achieved with U^IVO₂ and Cu^II depending on the stoichiometry of the reactants. The complexes were characterized by elemental analysis, ¹H-n.m.r., u.v.–vis, i.r., f.a.b.-m.s. and by cyclic voltammetry.     

Synthesis,spectroscopy and electrochemistry of mono and dinuclear complexes of a peripherally mixed ligand and the interaction of (E,E) Ni(LH)2 with Pd2+ and Ag+

We describe the synthesis, characterization and electrochemistry of a new family of peripherally functionalised vic-dioxime, 5,6-bis-(hydroxyimino)-1,2,9,10-hydroxy-4,7-dithiadecane (LH₂), with bis-(thiopropandiol) moieties attached to the oxime. Thiopolyalcohol groups containing two different heteroatoms (—S— and —O—) serve as weak exocyclic binding sites for Pd⁺² and Ag⁺ ions. Novel mononuclear (LH)₂M, (M = Ni^II, Cu^II, Co^II, Mn^II and Fe^II), homodinuclear (LH)₂(UO₂)₂(OH) and heterotrinuclear (LH)₂MM₂ (M = Ni^II and M = Pd^II and Ag^I) species have been obtained with the metal:ligand ratios of 1:2, 2:2, and 3:2 respectively. Metal ions coordinate through N,N of the oxime and S,O donor sites of the peripherally attached groups in the presence of the base. The heterotrinuclear complexes were prepared by the interaction of the mononuclear complex, (LH)₂Ni, with Pd(C₅H₅)₂ and AgNO₃ in an appropriate solvent. The complexes were characterized by elemental analysis, ¹H-n.m.r., u.v.–vis. spectroscopy, FT-IR., and by f.a.b-m.s. The redox properties of the complexes were studied by cyclic voltammetry.     

Novel vic-dioxime ligands and their poly-metal complexes bearing 1,8-diamino-3,6-dioxaoctane: synthesis, characterization, spectroscopy and electrochemistry

Three novel vic-dioxime ligands containing the 1,8-diamino-3,6-dioxaoctane group, N,N′-(1,8-diamino-3,6-dioxaoctane)-p-tolylglyoxime (L¹SL¹H₄), N,N′-(1,8-diamino-3,6-dioxaoctane)-phenylglyoxime (L²SL²H₄), and N,N′-(1,8-diamino-3,6-dioxaoctane)-glyoxime (L³SL³H₄) have been prepared from 1,8-diamino-3,6-dioxaoctane with anti-p-tolylchloroglyoxime, anti-phenylchloroglyoxime or anti-monochloroglyoxime. Polynuclear complexes [M(L ^x SL ^x )] _n or [M(L ^x SL ^x )(H₂O)] _n (x = 1, 2 and 3), where M = Cu^II, Co^II, and Ni^II, have been obtained with 1:1 metal/ligand ratio. The Cu^II and Ni^II poly-metal complexes of these ligands are proposed to be square planar, while also the prepared Co^II complexes are proposed to be octahedral with two water molecules as axial ligands. The detection of H-bonding in the [Ni(L¹SL¹)] _n , [Ni(L²SL²)] _n and [M(L³SL³)(H₂O)] _n metal complexes by FT i.r. spectra revealed the square planar or octahedral [MN₄·H₂O)] _n coordination of poly-nuclear metal complexes. [MN₄] _n coordination of the [Ni(L¹SL¹)] _n and [Ni(L²SL²)] _n complexes were also determined by ¹H-n.m.r. spectroscopy. The ligands and poly-metal complexes were characterized by elemental analyses, FT-i.r., u.v.-vis., ¹H and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, and differential pulse voltammetric (DPV) techniques.