Photoreduction of chlorohemin in pure pyridine

Chlorohemin (Fe(III)PPCl) undergoes photoreduction when irradiated in pure pyridine solution with 400–450 nm light. A thermal reduction is observed to occur simultaneously with the photochemical one, but after a one hour irradiation about 75% of the reduction product is formed in a photochemical way. Both five and six-coordinated species are observed to be present in solution; however, only the Fe(III)PPpy⁺ five coordinated complex is photoreducible. A mechanism is proposed whereby the primary photochemical act is an axial pyridine → iron electron transfer process yielding Fe(II)PP and py⁺ species. The Fe(II)PP moiety gives rise to the formation of the spectrophotometrically detectable Fe(II)(PP(py)₂ complex. ESR spin trapping results are consistent with the formation of 2-pyridyl radicals from py⁺ cation by fast transfer of a proton to a pyridine molecule.     

Reactions of meso-hydroxyhemes with carbon monoxide and reducing agents in search of the elusive species responsible for the g = 2.006 resonance of carbon monoxide-treated heme oxygenase. Isolation of diamagnetic iron(II) complexes of octaethyl-meso-hydroxyporphyrin

To examine possible models for the g = 2.006 resonance seen when the hydroxylated heme-heme oxygenase complex in the Fe(III) state is treated with CO, the reactivities of CO and reducing agents with (py)(2)Fe(III)(OEPO) and [Fe(III)(OEPO)](2) (OEPO is the trianion of octaethyl-meso-hydroxyporphyrin) have been examined. A pyridine solution of (py)(2)Fe(III)(OEPO) reacts in a matter of minutes with zinc amalgam (or with hydrazine) under an atmosphere of dioxygen-free dinitrogen to produce bright-red (py)(2)Fe(II)(OEPOH).2py.0.33H(2)O, which has been isolated in crystalline form. The (1)H NMR spectrum of (py)(2)Fe(II)(OEPOH) in a pyridine-d(5) solution is indicative of the presence of a diamagnetic compound, and no EPR resonance was observed for this compound. Treatment of a solution of (py)(2)Fe(II)(OEPOH) in pyridine-d(5) with carbon monoxide produces spectral changes after a 30 s exposure that are indicative of the formation of diamagnetic (OC)(py)Fe(II)(OEPOH). Treatment of a green pyridine solution of (py)(2)Fe(III)(OEPO) with carbon monoxide reveals a slow color change to deep red over a 16 h period. Although a resonance at g = 2.006 was observed in the EPR spectrum of the sample during the reaction, the isolated product is EPR silent. The spectroscopic features of the final solution are identical to those of a solution formed by treating (py)(2)Fe(II)(OEPOH) with carbon monoxide. Addition of hydrazine to solutions of (OC)(py)Fe(II)(OEPOH) produces red, diamagnetic (OC)(N(2)H(4))Fe(II)(OEPOH).py in crystalline form. The X-ray crystal structures of (py)(2)Fe(II)(OEPOH).2py.0.33H(2)O and (OC)(N(2)H(4))Fe(II)(OEPOH).py have been determined. Solutions of diamagnetic (OC)(N(2)H(4))Fe(II)(OEPOH).py and (OC)(py)Fe(II)(OEPOH) are extremely air sensitive and are immediately converted in a pyridine solution into paramagnetic (py)(2)Fe(III)(OEPO) in the presence of dioxygen.     

Intermediates in the intramolecular ligand transfer reactions of h5-C5H5Fe(CO)2R complexes

Dissolution of h⁵-C₅H₅Fe(CO)₂R (I) (R = cyclohexyl or cyclohexylmethyl) in DMSO leads to the formation of a solvent coordinated acyl complex, h⁵-C₅H₅Fe(CO)(COR)(DMSO) (II). Treatment of this complex with triphenylphosphine leads to its conversion to h⁵-C₅H₅Fe(COR)(PPh₃) (III). Rates for the reaction I ? and II → III have been determined. A comparison of the rates of the reaction I → III in eight solvents shows no specific rate acceleration in DMSO and no correlation with solvent donicity. The results are in accord with a two step mechanism in which the first intermediate is the coordiantively-unsaturated species h⁵-C₅H₅Fe(COR)(CO). The small spread in rates for solvents of widely different dielectric constants suggests little charge separation in the transition state for this step.     

Hyperfine shifts of the 13C-NMR. in low spin iron(3) porphyrin complexes

The ¹³C-NMR. in Zn(II)(Porphin), Fe(III)(Porphin)(CN₂), Zn(II)(Tetraphenyl-porphin), and Fe(III)(Tetraphenylporphin)(CN₂) have been identified, and the ¹³C hyperfine shifts in the iron complexes evaluated. It was found that dipole-dipole coupling with the electron spin localized in the π-orbitals of the aromatic carbon atoms makes an important contribution, to the ¹³C hyperfine shifts. In a preliminary analysis the experimental spin density distribution obtained from the combined ¹H- and ¹³C-NMR.-data is compared with theoretical models of the iron porphyrin complexes.     

Cleavage of the indium(III) octaethyloxophlorin dimer, {In(III)(OEPO)}2, with Lewis bases. Importance of outer-sphere hydrogen bonding in adduct structures

Splitting of the oxygen-bridged dimer {In(III)(OEPO)}(2) [where (OEPO)(3-) is the trianion of octaethyloxophlorin] by potential axial ligands has been examined and compared to results obtained previously for the cleavage of {Fe(III)(OEPO)}(2). Treatment of {In(III)(OEPO)}(2) with an excess of imidazole (im) produced the crystalline complex {(im)(2)In(III)(OEPO...im)}(2).(im)(2)In(III)(OEPO).2Cl(2)C(6)H(4). This solid contains two different (im)(2)In(III)(OEPO) units that are bridged through hydrogen bonding by an uncoordinated imidazole. Treatment of {In(III)(OEPO)}(2) with an excess of pyridine (py) produced (py)(2)In(III)(OEPO), which is isostructural with (py)(2)Fe(III)(OEPO). Although {Fe(III)(OEPO)}(2) reacted with xylyl isocyanide (xylylNC) to form the novel free-radical complex (2,6-xylylNC)(2)Fe(II)(OEPO(*)) [where (OEPO(*))(2-) is the radical dianion of octaethyloxophlorin], {In(III)(OEPO)}(2) was unreactive toward xylyl isocyanide.     

Electrochemistry and spectroelectrochemistry of heterobimetallic porphyrin-corrole dyads. Influence of the spacer, metal ion, and oxidation state on the pyridine binding ability

Combined electrochemical and UV-visible spectroelectrochemical methods were utilized to elucidate the prevailing mechanisms for electroreduction of previously synthesized porphyrin-corrole dyads of the form (PCY)H2Co and (PCY)MClCoCl where M = Fe(III) or Mn(III), PC = porphyrin-corrole, and Y is a bridging group, either biphenylenyl (B), 9,9-dimethylxanthenyl (X), anthracenyl (A), or dibenzofuranyl (O). These studies were carried out in pyridine, conditions under which the cobalt(IV) corrole in (PCY)MClCoCl is immediately reduced to its Co(III) form, thus enabling direct comparisons with the free-base porphyrin dyad, (PCY)H2Co(III) under the same solution conditions. The compounds are all reduced in multiple one-electron-transfer steps, the first of which involves the M(III)/M(II) process of the porphyrin in the case of (PCY)MClCoCl and the Co(III)/Co(II) process of the corrole in the case of (PCY)H2Co. Each metal-centered redox reaction may be accompanied by the gain or loss of pyridine axial ligands, with the exact stoichiometry of the exchange process depending upon the specific combination of metal ions in the dyad, their oxidation states, and the particular spacer in the complex. Before this study was started, it was expected that the porphyrin-corrole dyads with the largest spacers, namely, O and A, would readily accommodate the formation of cobalt(III) bis-pyridine adducts because of the larger size of the cavity while dyads with the smallest B spacer would seem to have insufficient room to add even a single pyridine within the cavity, as was structurally seen in the case of (PCB)H2Co(py). This is clearly not the case, as shown in the present study. A reversible Co(III)/Co(II) reaction is seen for (PCB)MnClCoCl at -0.62 V, which when combined with spectroscopic data, leads to the assignment of (PCB)Mn(III)(py)2Co(III)(py) as the species in pyridine. The reduction of (PCB)Mn(III)(py)2Co(III)(py) to (PCB)Mn(II)(py)Co(III)(py) is accompanied on the slower spectroelectrochemical time scale by the appearance of a 603 nm band in the UV-vis spectra and is consistent with the addition of a second pyridine ligand to the Co(III)(py) unit of the dyad as one ligand is lost from the electrogenerated manganese(II) porphyrin, thus maintaining one pyridine ligand within the cavity. A different change in the coordination number is observed in the case of (PCB)FeClCoCl. Here the initial Fe(III) complex can be assigned as (PCB)Fe(III)ClCo(III)(py), which has no pyridine molecule within the cavity and the singly reduced form is characterized as (PCB)Fe(II)(py)2Co(III)(py)2, which contains two pyridine ligands inside the cavity. A following one-electron reduction of the Fe(II)/Co(III) complex then gives [(PCB)Fe(II)(py)2Co(II)]-.     

Synthesis and structure of iron(III) complexes containing a quasi-crownether ring

A barium-iron(III) [BaFe(cr-salen)(py)₂](ClO₄)₃ (1) was prepared and an iron(III) complex [Fe(cr-salen)(py)₂]ClO₄ (2) complex was obtained by removing Ba²⁺ ion from the barium-iron(III) complexes with guanidinium sulfate. These complexes are in the high-spin state both in the solid state and in acetonitrile. Single crystals of [BaFe(cr-salen)(MeOH)₂]₂O(ClO₄)₄·2MeOH (3) were obtained by slow evaporation of a solution of (2) and Ba(ClO₄)₂, and the single crystal X-ray structure of (3) was determined: Crystal data for [BaFe(cr-salen)(MeOH)₂]₄O₂(ClO₄)₄·2MeOH: C₂₅H₃₆N₂O_17.5Cl₂BaFe, are: space group C2/c, Z=8, a=24.79(7) Å, b=16.11(6) Å, c=17.24(6) Å, V=6753(36) ų, R=0.133, R_w=0.154. The structure of the complex has a one order polymeric chain. An iron atom is located in a cavity of square pyramidal geometry and bridged by an oxygen atom of μ-oxo. A barium ion is sitted in a quasi-crownether ring and bridged by two perchlorate anions.     

Outer-sphere electron-transfer reactions of co(III)–polymer complexes in relation to its polymer effects

The outer-sphere electron-transfer reactions between [Co(III)(NH₃)₅L] (CIO₄)₃ [L = polyethyleneimine (PEI), L = NH₃(Amm)] or cis-[Co(III)(en)₂L′Cl]Cl₂ [L′ = poly-N-vinyl-2-methylimidazole(PVI), poly-4-vinylpyridine (PVP), N-ethylimidazole (NEI), pyridine (Py)] and various Fe(II) were studied. In the reaction with Fe(II)-(phen)₃²⁺, the reactivity of Co(III)–PEI was smaller than that of Co(III)–Amm due to the larger electrostatic repulsion. On the other hand, the reactivity of Co(III)–PEI was larger by a factor of 80 in the reaction with Fe(II)(H₂O)₆²⁺. From the results of rapid-scanning spectroscopy, the higher reactivity of Co(III)–PEI is caused by the coordination of free ethyleneimine residues in the Co(III)–PEI to Fe(II)–ion. Further more, the hydrophobic interaction between heteroaromatic polymer ligands and Fe(II)-(phen)₃²⁺ brought about the higher reactivities of Co(III)–PVI and Co(III)–PVP. Three interactions caused by the essential properties of polymers are discussed in relation to conformational changes.     

Synthesis and X-ray crystal structure of a new μ-hydroxo dinuclear cobalt complex containing one cis-β folded and one planar salen moiety

The reduction of [Co(III)(tmsalen)(py)₂]⁺ with NaBH₄/PdCl₂ and the successive oxidative addition of CH₂ClI, carried out in neutral methanolic solution and followed by the addition of NaOH, afford a new dinuclear complex. The molecular structure reveals that it is formed by an octahedral [Co(tmsalen)(py)(OH)] unit connected to a β-folded [Co(tmsalenCH₂)]⁺ fragment, in such a way that the latter metal completes the coordination sphere with the hydroxo group and a tmsalen oxygen from the former unit.     

One-dimensional heterobimetallic cyanide-bridged Fe(III)–Mn(II) complex: Synthesis,crystal structure,and magnetic properties

A new cyanide-bridged heterobimetallic Fe(III)–Mn(II) complex {[MnL][FebpdBrb]} [FebpdBrb]_n· 2nH₂O has been synthesized by using pyridinecarboxamide trans-dicyanideiron as the building block. The X-ray diffraction analysis has revealed the one-dimensional infinite structure of the complex consisting of the alternating [Mn(L)]²⁺ and [Fe(bpdBrb)(CN)₂]^– units forming a cyanide-bridged cationic polymeric chain, with [Fe(bpdBrb)(CN)₂]^– as the free anions. The antiferromagnetic coupling between the neighboring Fe(III) and Mn(II) ions through the bridging cyanide group has been revealed. The magnetic coupling constant has been determined as of J =–3.17 cm^–1.     

Synthesis,crystal structure,and magnetic characteristics of chiral cyanide-bridged Fe–Cu complex

Based on the building blocks, trans-dicyanide Fe(III) precursor and chiral amine Cu(II) compound, the chiral cyanide-bridged heterometallic Fe(III)–Cu(II) complex with the formula {[Cu(R/R-Chxn)₂Fe(bpmb)·(CN)₂][Fe(bpmb)(CN)₂]}·CH₃OH·H₂O (1) [bpmb^2– = 1,2-bis(pyridine-2-carboxamido)-4-methylbenzenate, R,R-Chxn = R,R-1,2-diaminocyclohexane] has been synthesized and characterized by elemental analysis, IR spectra and X-ray analysis. The latter revealed that the complex contained the cyanide-bridged cationic binuclear entity and free anionic cyanide building block. The complex demonstrated weak ferromagnetic coupling between neighboring Fe(III) and Cu(II) ions via the bridging cyanide group.     

Direct evidence for chemically distinct regions within nation films on electrodes

Electrochemical and spectroelectrochemical experiments on the complexes [(bpy)₂(py)Ru^II(OH₂)]²⁺ and [(trpy)(bpy)Ru^II(OH₂)]²⁺ (py is pyridine; bpy is 2,2'-bipyridine; trpy is 2,2',2“-terpyridine) with Nation films coated on electrodes demonstrate that the complexes partition amongst three chemically distinct regions or phases. As Ru(II) the complexes reside both in an electroinactive phase and, based on the pH dependence of the Ru(III)/(II) couples, e.g., [(bpy)₂(py)Ru^III(OH)]²⁺/[(bpy)₂(py)Ru^II(OH₂)]²⁺, in two electroactive phases. Partitioning amongst the three phases depends on the pH of the external solution and on the oxidation state and proton content of the complex. Addition of alcohols releases the complex from the electroinactive phase but at the expense of loss of the bound water molecule and binding to the sulfonate sites by anation and, therefore, to a fourth distinct chemical or physical state in which the complex can exist within Nation films.     

In situ surface-enhanced IR absorption spectroscopy on CO adducts of iron protoporphyrin IX self-assembled on a Au electrode

The surface coordination chemistry of carbon monoxide with the reduced form (Fe(II)PP) of iron(III) protoporphyrin IX (Fe(III)PP) monolayer self-assembled on a Au electrode in 0.1 M HClO4 was studied for the first time by using in situ ATR-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). Both mono- and biscarbonyl adducts [simplified as Fe(II)(CO)PP and Fe(II)(CO)2PP, respectively] were detected, depending on the history of potential control. Initially, the Fe(II)(CO)PP predominates, and the intermediate transition potential for the conversion of Fe(II)(CO)PP to Fe(III)PP and CO was spectrally determined to be ca. 0.09 V (vs SCE). The ratio of Fe(II)(CO)2PP and Fe(II)(CO)PP increases after a potential excursion to a sufficiently positive value. Fe(II)(CO)2PP is much more stable against its electro-oxidation to Fe(III)PP than its counterpart Fe(II)(CO)PP with increasing potential. The observed change of coordination properties may be ascribed to an irreversible structural reorganization of the FePP adlayer caused by the potential excursion.     

Iron pyrrole‐based PNP pincer ligand complexes as catalyst precursors

The structure of a pincer ligand consists of a backbone and two `arms' which typically contain a P or N atom. They are tridentate ligands that coordinate to a metal center in a meridional configuration. A series of three iron complexes containing the pyrrole‐based PNP pincer ligand 2,5‐bis[(diisopropylphosphanyl)methyl]pyrrolide (PN^pyrP) has been synthesized. These complexes are possible precursors to new iron catalysts. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}carbonylchlorido(trimethylphosphane‐κP )iron(II), [Fe(C₁₈H₃₄NP₂)Cl(C₃H₉P)(CO)] or [Fe(PN^pyrP)Cl(PMe₃)(CO)], (I), has a slightly distorted octahedral geometry, with the Cl and CO ligands occupying the apical positions. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}chlorido(pyridine‐κN )iron(II), [Fe(C₁₈H₃₄NP₂)Cl(C₅H₅N)] or [Fe(PN^pyrP)Cl(py)] (py is pyridine), (II), is a five‐coordinate square‐pyramidal complex, with the pyridine ligand in the apical position. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}dicarbonylchloridoiron(II), [Fe(C₁₈H₃₄NP₂)Cl(CO)₂] or [Fe(PN^pyrP)Cl(CO)₂], (III), is structurally similar to (I), but with the PMe₃ ligand replaced by a second carbonyl ligand from the reaction of (II) with CO. The two carbonyl ligands are in a cis configuration, and there is positional disorder of the chloride and trans carbonyl ligands.     

Photoreduction of fe(iii) protoporphyrin ix in ethanol-water solutions containing bifunctional ligands

The irradiation of Fe(III) protoporphyrin IX [Fe(III)PPIX) in a thoroughly deoxygenated 35% ethanol-water solution containing pyrazine (pyz) leads to changes in the visible spectrum that are indicative of Fe(II)PP species formation. With a large excess of pyz the spectrum is similar to that of the Fe(II) pyridine hemochrome, suggesting that the monomer Fe(II)PP(pyz)₂ is formed. With a lower pyz content, the photochemically formed bis-pyz complex converts to a polymeric Fe(II)PP species. A similar photochemical behaviour is observed when piperazine or 4,4′-bipyridine are used as bridge ligands instead of pyz. The origin of the absorptions characteristic of the photoreaction products is discussed on the basis of the dependence of the spectra on the nature of the bridge ligands.     

The magnetic and structural elucidation of 3,5-bis(2-pyridyl)-1,2,4-triazolate-bridged dinuclear iron(II) spin crossover compounds

Variable temperature magnetic susceptibility, Mössbauer spectroscopic and X-ray crystallographic studies are described on two structurally similar families of dinuclear iron(II) spin crossover (SCO) complexes of formula [Fe(NCX)(py)]₂(μ-L)₂, where L is either a 3,5-bis(2-pyridyl)-pyrazolate bridging ligand, bpypz⁻, examples of which have been earlier reported by Kaizaki and coworkers, or a corresponding 3,5-bis(2-pyridyl)-1,2,4-triazolate, bpytz⁻. Compounds synthesised were [Fe(NCS)(py)]₂(μ-bpypz)₂ (1), [Fe(NCSe)(py)]₂(μ-bpypz)₂ (2), [Fe(NCS)(py)]₂(μ-bpytz)₂ (3), [Fe(NCSe)(py)]₂(μ-bpytz)₂ (4), [Fe(NCBH₃)(py)]₂(μ-bpytz)₂ (5). The crystal and molecular structures of 1 and 3 are very similar in their HS–HS forms (HS = high spin d⁶). In contrast to reported SCO behaviour for precipitated samples of 1, also repeated here, crystals of 1 show only HS–HS behaviour with no spin crossover transition. Complex 3 likewise displays HS–HS magnetism, with very weak antiferromagnetic coupling. Compound 5 displays a well resolved two-step, full spin transition from HS–HS to LS–LS states while compound 2 shows a one step transition. The Mössbauer data for 2 and 5 show unusual features at low temperatures.     

Synthese und Eigenschaften von Eisen(II)-Komplexen mit vier- und fünfzähnigen N,S-Chelatliganden. Kristallstruktur von [Fe(GBMA)py] · py (GBMA2− = Glyoxal-bis-(2-mercaptoanil))

Synthesis and Properties of Iron(II) Complexes with tetra- and pentadentate N,S-Chelate Ligands. Crystal Structure of [Fe(GBMA)py] · py (GBMA^2? = Glyoxal bis-(2-mercaptoanil)) The complexes glyoxal-bis-(2-mercaptoanil)iron(II) [Fe(GBMA)], diacetyl-bis-(2-mercaptoanil)iron(II), [Fe(DBMA)] and o-phthalaldehyde-bis-(2-mercaptoanil)iron(II) [Fe(PhBMA)] have been synthesized by reaction of the corresponding protonated ligands with anhydrous iron(II)-acetate. Pyridine-2,6-dialdehyde-bis-(2-mercaptoanil)iron(II), [Fe(PyBMA)] was obtained by a template synthesis with pyridine-2,6-dialdehyde, 2-aminothiophenol and iron(II)-acetate. Recrystallizing the complexes [Fe(GBMA)] and [Fe(DBMA)] from pyridine afforded [Fe(GBMA)py] · py and [Fe(DBMA)py] · py. For all complexes the magnetic properties have been determined, and the Mössbauer spectra were recorded at 82 K. Compounds [Fe(GBMA)] and [Fe(DBMA)] show quasi reversible redox properties in the cyclovoltammogram, while for [Fe(PhBMA)] an irreversible oxidation was observed. [Fe(GBMA)py] · py crystallizes in the monoclinic space group P2₁ with a = 1288.7(1), b = 1242.63(5), c = 1396.0(1) pm, β = 98.24(1)°, and Z = 4. In the neutral complex the Fe atom has a square pyramidal coordination with the pyridine nitrogen atom in apical position. The basal plane is formed by two nitrogen and two sulfur atoms of the ligand GBMA^2?. The iron is located 40 pm above the pyramidal base. Its average distances to the donor atoms of the GBMA ligand are Fe? N = 190 pm, and Fe? S = 222 pm, while the distance to the nitrogen atom of the coordinated pyridine molecule is 207 pm.     

Heptanuclear high-spin complex compounds based on S-donors

The precursors [Fe(III)(^SYL)Cl] (^SYLH₂) = N,N′-bis(1-hydroxy-Y-2-benzyliden)-1,6-diamino-3-thiohexane, (Y = H, 3EtO, 5Me) are high-spin (S = 5/2) complexes. The precursors are combined with [Fe(II)(CN)₆]⁴⁻ and [Co(III)(CN)₆]³⁻ to yield star-shaped heptanuclear clusters, [Fe(II)(CN–Fe(III)^SYL)₆]Cl₂ and [Co(III)(CN–Fe(III)^SYL)₆]Cl₃. The star-shaped compounds are high-spin (HS) systems at room temperature. On cooling to 20 K some of the iron(III) centers perform some HS–HS transition.     

Mixed Valence Chemistry of Pyrimidine Bridged Binuclear Complex of Pentacyanoferrate and Pentaammineruthenium

The pyrimidine bridged binuclear complex (CN)₅FepymRu(NH₃)₅- (I) was prepared in aqueous solution by mixing cquimolar of Fe(CN)₅OH₂^3? and Ru(NH₃)₅pym²⁺. Its mixed valence state molecule (CN)₅FepymRu(NH₃)₅(II) was obtained upon oxidation of I by one equivalent of peroxydisulfate ion. Both binuclear complexes and corresponding Fe(II) and Ru(II) mononuclear complexes displayed a metal-to-ligand charge transfer absorption in 400–450 nm region. Rate constants of formation and dissociation of I and II were measured, and the values of k_f (?10³M^?1s^?1) and k_d (?10^?3-10^?4 s^?1) were consistent with kinetic results expected for the substitution of Fe(CN)₅OH₂^3? with di- and trivalent ligands. Cyclic voltammetry of I exhibited two one-electron steps of oxidation corresponding to [III, L, II] + e → [II, L, II] and [III, L, III] + e → [III, L, II], respectively. The mixed valence binuclear complex II showed an intervalence band at 955 nm with a molar extinction coefficient 5.80 × 10² M^?1cm^?1 and a half-width 5100 cm^?l. The properties of the IT band conform to Hush's theory. Spectroscopic, electrochemical and kinetic results of II suggest that the mixed valence complex features a trapped - valence formulation with localized oxidation states of Fe(II) and Ru(III).     

Synthesis,crystal structure,magnetic and spectroscopic properties of {[Cu(oxbe)(py)]2Ni(py)2}·2Dmf complex of dissymmetrical oxamidate

The trinuclear complex {[Cu(oxbe)(py)]₂Ni(py)₂}·2DMF has been prepared and characterized by elemental analysis, IR and electronic spectra and magnetic susceptibility, where H₃oxbe is the dissymmetrical ligand N-benzoato-N′-(2-aminoethyl) oxamido, py?=?pyridine, DMF?=?dimethylformamide. The molecular structure of this complex is centrosymmetrical and has an extended oxamido-bridged structure consisting of two pyramidal copper(II) and one octahedral nickel(II) ions. The central Ni(II) and two terminal Cu(II) ions are antiferromagnetically coupled, J?=???60.2?cm^?1.