Transition metal chemistry of oxime-containing ligands,part XXIII; some trinuclear copper(II) complexes of quinoline-2-aldoxime and isoquinoline-3-aldoxime

Summary Some copper(II) complexes of types [Cu₃(L)₃(OH)₂](X) and [Cu₃(L)₃(OH)(SO₄)] · 3 H₂O (where L=qox, anion of quinoline-2-aldoxime (Hqox) or iqox, anion of isoquinoline-3-aldoxime (Hiqox) and X=Cl, Br, I, NO₃, NCS or NCSe) were prepared and characterized by elemental analysis, molecular conductance, magnetic moment (300-77K) and spectral measurements. The complexes are highly antiferromagnetic and have S=1/2. A distorted square-pyramidal structure with CuN₂O₃ chromophore is proposed.     

Transition metal chemistry of oxime-containing ligands,IX

The vibrational (conventional and far-infrared) and diffuse-reflectance spectra in conjunction with magnetic susceptibility measurements over a temperature range down to liquid nitrogen temperature are reported and discussed for the complexes; [Mn(HPOX)₂ X ₂]; [Mn(HMPX)₂ X ₂]; [Fe(HPOX)(POX) X ₂] and [Fe(HMPX)(MPX) X ₂](whereHPOX=pyridine-2-aldoxime (C₆H₆N₂O);POX=C₆H₅N₂O;HMPX=6-Methylpyridine-2-aldoxime (C₇H₈N₂O);MPX=C₇H₇N₂O;X=Cl, Br, I, NO₃, NCS, or OA c andX ₂=SO₄). On the basis of these physical studies a six-coordinated structure is suggested for the manganese(II) and iron(III) complexes.Mössbauer spectra, measured at room-temperature and liquid nitrogen temperature also indicated a six-coordinate geometry for iron(III) complexes.

---

Übergangsmetallkomplexe mit Oxim-enthaltenden Liganden, IX. Spektroskopische und magnetische Untersuchungen von Mn(II)- und Fe(II)-Komplexen mit Pyridin-2-aldoxim und 6-Methylpyridin-2-aldoxim

Zusammenfassung Es wurden Komplexe von Pyridin-2-aldoxim (HPOX) und 6-Methylpyridin-2-aldoxim (HMPX) vom Typ [Mn(HPOX)₂ X ₂], [Mn(HMPX)₂ X ₂], [Fe(HPOX)(POX)X ₂] und [Fe(HMPX)(MPX)X ₂] (X=Cl, Br, I, NO₃, NCS, OA c;X ₂=SO₄) dargestellt. Die Diskussion erfolgt basierend auf Infrarot-spektroskopie (inklusive fernes IR), Messungen der magnetischen Suszeptibilität (Temp. bis zu fl. N₂) undMössbauer-Spektroskopie.

     

Transition metal chemistry of oxime-containing ligands,part XI. Copper(II) complexes of syn-phenyl-2-pyridylketoxime and syn-methyl-2-pyridylketoxime

Summary Some copper(II) complexes of the types: Cu(HPPK)-(PPK)X, Cu(HMPK)(MPK)X (where HPPK = syn-phenyl-2-pyridylketoxime, HMPK = syn-methyl-2-pyridylketoxime and X = Cl^–, Br^–, I^–, NO₃ ^–, SCN^– or SeCN^–) Cu(HPPK)₂SO₄ 3 H₂O and Cu(HMPK)₂SO₄ · 3 H₂O were synthesized and characterized by analysis, magnetic susceptibility, e.s.r., reflectance and i.r. spectral measurements. The spectral data suggest that Cu(HPPK)(PPK)X and Cu(HMPK)(MPK)X containcis square-coplanar [Cu(HPPK)(PPK)]⁺ and [Cu(HMPK)(MPK)]⁺ units respectively, linked by weakly coordinated anions, giving infinite polymeric highly distorted octahedral chain structures, whereas Cu(HPPK)₂SO₄ · 3H₂O and Cu(HMPK)₂SO₄ · 3 H₂O have acis distorted octahedral structure containing two ligand molecules of ketoxime and a bidentate sulphate group. The polycrystalline e.s.r. spectra suggest a distorted octahedral stereochemistry for the Cu^II ion involving a ground-state. By using e.s.r. and reflectance spectral data, the orbital reduction parameters, k₁₁ and k₁ were calculated and interpreted in terms of molecular orbital coefficients.     

Pyridine-2-aldoxime and 6-methylpyridine-2-aldoxime as gravimetric reagents for estimation of palladium(II) and uranium(VI)

Pyridine-2-aldoiumc (I) has been found to be a sensitive reagent for the gravimetric determination of palladium(II). From chloride medium, precipitation is complete at pH 3.0-11.0, and in solution containing 1NHNO(3) to pH6.0. The compositions of the precipitates (dried at 130 degrees ) correspond to PdL(2), and PdL(2). HNO(3) (HL representing the reagent) respectively. Pd(II) can be estimated gravimetncally in presence of acetate, oxalate, tartrate, phosphate, fluoride borate, perchlorate, Cu(II), Cd, Co(II), Fe(II), Ni, Zn, Pb, Bi, Sb(III), Pt(IV), Ir(IV), Ru(III), Rh(III); Os(IV) in quantities more than twice that of Pd(II), and Ag(I), Au(III) and Fe(II) even m traces cause serious interference. The yellow uranium(VI) complex with (I) is precipitated quantitatively over the pH range 3.5-10.5 and, after washing and drying corresponds to the composition (c(6)h(5)n(2)o)(2)uo(2), The uranium(VI) complex with 6-methylpyridine-2-aldoxime (II) is precipitated quantitatively over the pH range 3.0-10.5, and after washing and drying at 120-130 degrees corresponds to UO(2),(C(7),H(7),N(2)O)(2). Both (I) and (II) are suitable for the estimation of 1-50 mg of uranium(VI) in the presence of up to 10-fold quantities ofTh(IV), La(III) and Ce(III) even when present together. Ce(IV) in quantities more than three times that of U must be reduced to Ce(III). Tartrate, citrate, phosphate, Ti(IV) and Zr interfere, but acetate, oxalate, and borate do not.     

Use of 6-methylpyridine-2-carbaldehydeoxime in nickel(II) carboxylate chemistry: synthetic, structural and magnetic properties of penta and hexanuclear complexes

The use of 6-methylpyridine-2-carbaldehydeoxime ligand (6-mepaoH), in nickel(II) chemistry has been investigated and three new clusters isolated in mild conditions. Depending on the nature of the metal starting salts and the reaction conditions, the Ni(II)/6-mepaoH system has provided access to the complexes [Ni(6)(O(2)CPh)(6)(6-mepao)(6)] (1), [Ni(6)(O(2)CMe)(6)(6-mepao)(6)] (2) and [Ni(5)(3-Cl-BzO)(4)(6-mepao)(4)(6-mepaoH)(2)(N(3))(2)] (3), where 3-Cl-BzO(-) is the 3-chlorobenzoate anion. Compounds 1 and 2 are two new members of the [Ni(6)(O(2)C-R)(oximato)(6)] family of hexanuclear complexes whereas 3 exhibits an unusual irregular bowtie topology including end-on azido bridges. The structures of the three compounds have been determined by single-crystal X-ray crystallography. Variable-temperature dc magnetic susceptibility studies were carried out for 1-3. The data indicate antiferromagnetic exchange for complexes 1 and 2 and ferrimagnetic interaction for complex 3.     

Ethers as ligands. Part VI. Transition metal(II) complexes with 18-crown-6

Summary Seven new coordination compounds are reported with the cyclicpolyether 18-crown-6 as the ligand,viz. [Mg(18-crown-6) (H₂O)₂](SbCl₆)₂, [M(18-crown-6)(MeNO₆)₂](SbCl₆)₂ with M is Ca²⁺ and Sr²⁺, [M(18-crown-6)(MeNO₂)](SbCl₆)₂ with M is Mn²⁺ and Co²⁺, and [M(18-crown-6)](SbCl₆)₂ with M is Ni²⁺ and Zn²⁺.     

Transition-metal chemistry of oxime-containing ligands—XXVII. Five- and six-coordinate complexes of iron(II) and iron(III) with 2,6-diacetylpyridine

Iron(II) and iron(III) complexes of 2,6-diacetylpyridine dioxime (H₂dapd) have been prepared and their electronic and structural properties investi     

The thermal decomposition reactions of bis-(pyridine-2-aldoxime)-copper(II) complexes

The thermal properties of some complexes of copper(II) with pyridine-2-aldoxime (HPAO), where the ligand appears either as the ion (PAO^–) or as a neutral molecule, were determined in vacuo and in dynamic nitrogen and oxygen gas atmospheres. The study was carried out by thermoanalytical (TG, DTG. DTA), spectroscopic and spectrometric (UV-visible, IR, diffuse reflectance, mass) techniques.The initial decomposition temperature is influenced by the number of acid hydrogens in the complex; the thermal stability sequence in vacuo is: [Cu(PAO)₂H]Cl > [Cu(PAO)₂H₂]Cl₂ > [Cu(PAO)₂]The thermal decomposition reactions occur in several separate steps, the first of which gives rise to partial ligand decomposition, the reduction of copper(II) to copper(I), and the conversion of the residual pyridine-2-aldoxime into acid amide.

---

Zusammenfassung Die thermischen Eigenschaften einiger Komplexe von Kupfer(II) mit Pyridin-2-aldoxim (HPAO), in denen der Ligand entweder als Ion (PAO^–) oder als neutrales Molekül vorliegt, wurden im Vakuum und in dynamischer N₂- und O₂-Atmosphäre ermittelt. Zur Untersuchung wurden thermoanalytische (TG, DTG, DTA) und spektrometrische (UV-sichtbar, IR, diffuse Reflektionsspektrophotometrie, Massenspektrometrie) Techniken herangezogen. Die Temperatur, bei der die Zersetzung beginnt, wird durch die Zahl der sauren Wasserstoffatome im Komplex beeinflußt; für die thermische Stabilität im Vakuum gilt die Reihenfolge [Cu(PAO)₂H]Cl > [Cu(PAO)₂H₂]Cl₂ > [Cu(PAO)₂]. Die thermischen Zersetzurigsreaktionen verlaufen in mehreren diskreten Schritten, wobei der erste von diesen eine partielle Zersetzung des Liganden, die Reduktion von Kupfer(II) zu Kupfer(I) und die Konversion des verbleibenden Pyridin-2-aldoxims in das Säureamid in sich einschließt.

---

-2- ( ), (-), . (, , ) , - , , - . , [Cu(PAO)₂H]CI > [Cu(PAO)₂H₂]Cl₂ > [Cu(PAO)₂] , , -2- .

     

Copper(II)-methylmalonate complexes with unidentate N-donor ligands: Syntheses,structural characterization and magnetic properties

Two new methylmalonate-bridged copper(II) complexes with the formulas [Cu(3-Ipy)(Memal)(H₂O)] (1) and [Cu(2,4′-bpy)(Memal)(H₂O)] · 3H₂O (2) [Memal = methylmalonate dianion, 3-Ipy = 3-iodopyridine, 2,4′-bpy = 2,4′-bipyridine] have been synthesized and characterized by X-ray diffraction. Both compounds crystallize in the monoclinic space group P2₁/n and Z = 4, with unit cell parameters a = 8.5874(13) Å, b = 7.1738(14) Å, c = 19.093(5) Å, β = 99.509(15)° in 1 and a = 17.375(4) Å, b = 7.3305(14) Å, c = 14.247(3) Å, β = 111.409(15)° in 2. The structures of 1 and 2 consist of zigzag chains of anti-syn carboxylate-bridged copper(II) ions running along the b direction. The pyridine-like ligands occupy one equatorial position of the copper environment avoiding the formation of the sheet-like arrangement observed in previously reported Memal complexes. The chains are grouped together in hydrophilic layers through hydrogen bonds and the layers are pillared through the 3-Ipy (1) and 2,4′-bpy (2) ligands which are stacked through π–π interactions involving alternatively aromatic ligands from two adjacent chains. Magnetic susceptibility measurements of both compounds in the temperature range 2–290 K show the occurrence of intrachain ferromagnetic interactions between the copper(II) ions [J = +2.66(2) cm^?1 (1) and J = +2.62(2) cm^?1 (2)].     

An investigation of some homo- and heterobinuclear complexes of copper(II) and nickel(II) with pyridine-2-aldoxime

The reactions between copper(II) or nickel(II) with thecis-pyridine-2-aldoxime complexes of the same metal ions have been investigated by spectrophotometric measurements. The homo and heterobinuclear chelates involved have been isolated as the chlorides and characterized by spectroscopic and thermoanalytical techniques. The first decomposition step is not dependent on the furnace atmosphere (N₂ or O₂) and is accompanied by a large exothermic effect (DSC curves in N₂). TG curves show that binuclear complexes are generally slightly less stable than the respective mononuclear complexes but, in the case of [Cu(NiL₂)Cl₂(H₂O)₂], the complexation of copper(II) gives rise a drastic decrease of its thermal stability.

---

Zusammenfassung Die Reaktionen zwischen Kupfer(II) und Nickel(II) mit den cis-Pyridin-2-aldoxim-Komplexen der gleichen Metallionen wurden spektrophotometrisch untersucht. Die homo- und heterobinuklearen Chelate wurden als Chloride isoliert und durch spektroskopische und thermoanalytische Methoden charakterisiert. Der erste Zersetzungsschritt ist unabhängig von der Ofenatmosphäre (N₂ oder O₂) und ist stark exotherm (s. DSC-Kurven in Abb. 1). Die TG-Kurven lassen erkennen, dass zweikernige Komplexe im allgemeinen etwas weniger stabil als die entsprechenden einkernigen Komplexe sind, im Falle von [Cu(NiL₂)Cl₂(H₂O)₂], aber die Anlagerung von Liganden an das Kupfer zu einer drastischen Verminderung der Stabilität führt.

---

- -2- . - , . ( ) , -, . , , , , [Cu(NiL₂)Cl₂(H₂O)₂], .

---

---

This work was carried out with financial support by MPI National Project.     

Dinuclear, tetranuclear and polymeric complexes in copper(II) perchlorate/pyridine-2,6-diamidoxime chemistry: synthetic, structural and magnetic studies

The initial use of pyridine-2,6-diamidoxime (pdamoH(2)) in metal cluster and polymer chemistry is described. Depending on the reaction conditions employed, the Cu(ClO(4))(2)·6H(2)O/pdamoH(2) system has provided access to the dinuclear compound [Cu(2)(pdamoH)(2)(ClO(4))(2)(MeOH)(2)] (1), the chain-like polymer [Cu(2)(pdamoH)(2)](n)(ClO(4))(2n) (2) and to the tetranuclear cluster [Cu(4)(pdamo)(2)(pdamoH)(2)](ClO(4))(2) (3). Single-crystal, X-ray crystallography reveals different coordination modes for the pdamoH(-) ligand in each compound, providing the first evidence for the flexibility and versatility of the anionic forms of pdamoH(2). Variable-temperature magnetic susceptibility studies indicate very strong antiferromagnetic coupling in the three complexes, attributable to the double oximato bridges which link the Cu(II) spin carriers.     

Bis(2-pyridylimino)isoindolato iron(II) and cobalt(II) complexes: structural chemistry and paramagnetic NMR spectroscopy

Condensation of phthalodinitrile and 2-amino-5,6,7,8-tetrahydroquinoline gave the bis(2-pyridylimino)isoindole protioligand 1 (thqbpiH) in high yield. Deprotonation of thqbpiH (1) using LDA in THF at -78 °C yields the corresponding lithium complex [Li(THF)(thqbpi)] (2) in which the lithium atom enforces almost planar arrangement of the tridentate ligand, with an additional molecule of THF coordinated to Li. Reaction of cobalt(II) chloride or iron(II) chloride with one equivalent of the lithium complex 2 in THF led to formation of the metal complexes [CoCl(THF)(thqbpi)] (3a) and [FeCl(THF)(thqbpi)] (3b). The paramagnetic susceptibility of 3a,b in solution was measured by the Evans method (3a: μ(eff) = 4.17 μ(B); 3b: μ(eff) = 5.57 μ(B)). Stirring a solution of 1 and cobalt(II) acetate tetrahydrate in methanol yielded the cobalt(II) complex 4 which was also accessible by treatment of 3a with one equivalent of silver or thallium acetate in DMSO. Whereas 3a,b were found to be mononuclear in the solid state, the acetate complex 4 was found to be dinuclear, the two metal centres being linked by an almost symmetrically bridging acetate. For all transition metal complexes paramagnetic (1)H as well as (13)C NMR spectra were recorded at variable temperatures. The complete assignment of the paramagnetic NMR spectra was achieved by computation of the spin densities within the complexes using DFT. The proton NMR spectra of 3a and 3b displayed dynamic behaviour. This was attributed to the exchange of coordinating solvent molecules by an associative mechanism which was analysed using lineshape analysis (ΔS(≠)= -154 ± 25 J mol(-1) K(-1) for 3a and ΔS(≠) = -168 ± 15 J mol(-1) K(-1) for 3b).     

Transition metal chemistry of oxime — Containing ligands,Part XXVIII; manganese(II) complexes of 2,6-diacetylpyridine dioxime

Summary Complexes of manganese(II) with the tridentate oxime ligand 2,6-diacetylpyridine dioxime (H₂dapd) have been synthesized and characterized. The complexes [Mn(H₂dapd)X₂] are pentacoordinate for X = Cl, Br or I but apparently octahedralvia bridging anions for X = NCS or NCSe. The complex [Mn(H₂dapd)(NO₃)₂] adopts an octahedral structure involving monodentate and bidentate coordination of nitro groups. The complexes [Mn(H₂dapd)₂]X₂ (X = Cl, Br, I, NO₃, NCS or NCSe) involve an octahedral cation.     

Co(II) and Ni(II) complexes with imidazole-containing ligands: Synthesis,structural characterization,and magnetic property

Hydrothermal reaction of Co(II) salt with 1,4-di(1-imidazolyl)benzene (L¹) and 4,4’-oxydiphthalic acid (H₄OA) yields a new complex [Co₃(HOA)₂(L¹)₄(H₂O)₄] (I). [Ni(L²)₂SO₄] · 0.5H₂O (II) can be obtained via the hydrothermal reaction of NiSO₄ · 6H₂O with 1,3-di(1H-imidazol-4-yl)benzene (L²). Complexes I and II have been characterized by single-crystal and powder X-ray diffraction (CIF files CCDC nos. 1019291 (I) and 1019292 (II)), IR, elemental, and thermogravimetric analyses. Complex I exhibits the uninodal six-connected 3D pcu framework structure of I with (4¹² · 6³) topology; Complex II consists of the uninodal four-connected 2D sql (4⁴ · 6²) networks. In addition, magnetic property of I was investigated.     

The synthesis and magnetic and spectral studies of some lanthanide(III) chelates of 6-methyl pyridine-2-aldoxime

A series of trivalent lanthanide chelates of the type [Ln(HMPOX)₃(X)₂](X) (where Ln³⁺ = La, Pr, Nd, Sm, Gd or Dy; HMPOX = 6-methylpyridine-2-aldoxime and X⁻ = NO₃ or Cl) have been synthesised by the direct reaction of 6-methylpyridine-2-aldoxime with lanthanide(III) nitrates or chlorides in 2,2′-dimethoxypropane and ethanol. These chelates have been characterized by analysis, molar conductance, X-ray powder diffraction patterns, magnetic, electronic and vibrational spectral studies. The analytical data reveal the presence of 1:3 (metal:ligand) stoichiometry and molar conductance data in ethanol indicate 1:1 electrolytes in all the lanthanide(III) chelates. The lanthanide(III) chelates with HMPOX are X-ray isomorphous. The magnetic moment values show little deviation from Van Vleck values. The electronic spectra, recorded at room temperature in methanol are dominated by ligand absorption bands and exhibit only slight shift and marked enhancement in the intensity of the bands. IR spectral data suggest the cis-coordination of the neutral HMPOX ligand molecules through pyridine nitrogen and oxime group nitrogen atoms and monodentate nitrate coordination to all lanthanide(III) chelates.     

Synthesis, structural analysis, and magnetic properties of ethylmalonate-manganese(II) complexes

Five manganese(II) complexes of formulas [Mn(2)(Etmal)(2)(H(2)O)(2)(L)](n) (1-4) and {[Mn(Etmal)(2)(H(2)O)][Mn(H(2)O)(4)]}(n) (5) with H(2)Etmal = ethylmalonic acid (1-5) and L = 1,2-bis(4-pyridyl)ethane (bpa) (1), 4,4'-azobispyridine (azpy) (2), 4,4'-bipyridyl (4,4'-bpy) (3), and 1,2-bis(4-pyridyl)ethylene (bpe) (4) were synthesized and structurally characterized by single crystal X-ray diffraction. Their thermal behavior and variable-temperature magnetic properties were also investigated. The structure of the compounds 1-4 consists of corrugated layers of aquamanganese(II) units with intralayer carboxylate-ethylmalonate bridges in the anti-syn (equatorial-equatorial) coordination mode which are linked through bis-monodentate bpa (1), azpy (2), 4,4'-bpy (3), and bpe (4) ligands to build up a three-dimensional (3D) framework. The structure of compound 5 is made up by zigzag chains of manganese(II) ions with a regular alternation of [Mn(H(2)O)(4)](2+) and chiral (either Δ or λ enantiomeric forms) [Mn(Etmal)(2)(H(2)O)](2-) units within each chain. In contrast to the bidentate/bis-monodentate coordination mode of the Etmal ligand in 1-4, it adopts the bidentate/monodentate coordination mode in 5 with the bridging carboxylate-ethylmalonate also exhibiting the anti-syn conformation but connecting one equatorial and an axial position from adjacent metal centers. The manganese-manganese separation through the carboxylate-ethylmalonate bridge in 1-5 vary in the range 5.3167(4)-5.5336(7) ?. These values are much shorter than those across the extended bis-monodentate N-donors in 1-4 with longest/shortest values of 11.682(3) (3)/13.9745(9) ? (4). Compounds 1-5 exhibit an overall antiferromagnetic behavior, where the exchange pathway is provided by the carboxylate-ethylmalonate bridge. Monte Carlo simulations based on the classical spin approach (1-5) were used to successfully reproduce the magnetic data of 1-5.     

Heptacopper(II) and dicopper(II)-adenine complexes: synthesis,structural characterization,and magnetic properties

The syntheses, crystal structures, and magnetic properties of two new copper(II) complexes with molecular formulas [Cu₇(μ₂-OH₂)₆(μ₃-O)₆(adenine)₆](NO₃)₂·6H₂O (1) and [Cu₂(μ₂-H₂O)₂(adenine)₂(H₂O)₄](NO₃)₄·2H₂O (2) are reported. The heptanuclear compound is composed of a central octahedral CuO₆ core sharing edges with six adjacent copper octahedra. In 2, the copper octahedra shares one equatorial edge. In both compounds, these basic copper cluster units are further linked by water bridges and bridging adenine ligands through N3 and N9 donors. All copper(II) centers exhibit Jahn–Teller distorted octahedral coordination characteristic of a d⁹ center. The study of the magnetic properties of the heptacopper complex revealed a dominant ferromagnetic intra-cluster interaction, while the dicopper complex exhibits antiferromagnetic intra-dimer interactions with weakly ferromagnetic inter-dimer interaction.     

Trinuclear copper(II) complexes derived from Schiff-base ligands based on a 6-amino-6-deoxyglucopyranoside: structural and magnetic characterization

The trinuclear copper(II) complexes ([CuL1)(mu-ac)Cu(mu-ac)CuL1) (1) and ([CuL2)(mu-ac)Cu(mu-ac)CuL2) (2) of the tridentate aminosaccharide-derived Schiff-base ligands H2L1 [6-N-(salicylidene)amino-6-deoxy-1,2,3-tri-O-methyl-alpha-D-glucopyranoside] and H2L2 [6-N-(3,5-di-tert-butylsalicylidene)amino-6-deoxy-1,2,3-tri-O-methyl-alpha-D-glucopyranoside] were synthesized and structurally characterized. The trinuclear complex units can be described as two terminal copper-ligand moieties bridged by a central copper acetate moiety, with the Cu centers arranged in a triangular fashion. IR and UV/vis spectroscopic studies strongly indicate that the trinuclear structure is maintained in a methanolic solution. The temperature dependence of the magnetic susceptibility of both complexes shows a moderate antiferromagnetic coupling and can be well interpreted by applying a symmetric Cua-Cub-Cua' model with linear spin topology. The fit of the magnetic data affords coupling constants J of -34 and -24 cm(-1) for 1 and 2, respectively [H = -J(SaSb + SbSa')]. For mu-alkoxo-mu-acetato-bridged copper(II) complexes with a large dihedral angle between the adjacent coordination planes, as found in 1 and 2, such an antiferromagnetic coupling is unusual. However, density functional theory calculations of 2 using BP86, B3LYP*, and B3LYP density functionals confirmed a symmetric doublet ground state.     

Spectroscopic,structural and magnetic studies of nickel(II) complexes with tetra- and pentadentate ligands

Abstract  Two new nickel(II) complexes, namely [Ni(BPSE)](BF₄) 1, and [Ni (5-BST)CH₃OH]ClO₄ 2 [BPSE = 2-benzoylpyridinesalicylidene ethylenediamine, 5-BST = 5-bromosalicylidene-tris(2-aminoethyl)amine] have been synthesized and characterized using various physico-chemical methods. The magnetic and spectroscopic data indicate a distorted square planar geometry for complex 1, while complex 2 is assigned a distorted octahedral geometry. Complex 1 crystallized in the triclinic space group P-1. Complex 2 adopts an octahedral geometry with space group symmetry P 21/n. The superoxide dismutase activity of these complexes has been measured. Graphical Abstract  This paper describes three new nickel (II) complexes viz; [Ni(BPSE)](BF4) 1, [Ni(BSE)] 2 and [Ni (5-BST) CH3OH] ClO4 3 [BPSE = 2-benzoylpyridine salicyledene-ethylenediamine, BSE = bis(salicylaldehyde) ethylenediamine, 5-BST = 5-bromosalicyledene-tris(2-amino ethyl) amine]. The magnetic and spectroscopic data indicate a distorted square planar geometry for complex 1 and 2, while the comlplex 3 is assigned a distorted octahedral geometry. Superoxide dismutase activity of these complexes have also been measured. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.