U(IV)/LN(III) unexpected mixed site in polymetallic oxalato complexes. Part II. Substitution of U(IV) for Ln(III) in the new oxalates (N2H5)Ln(C2O4)2·nH2O (Ln=Nd, Gd)

Two new hydrazinium lanthanide(III) oxalates, (N₂H₅)[Nd(C₂O₄)₂(H₂O)]·4H₂O (1) and (N₂H₅)[Gd(C₂O₄)₂(H₂O)]·4.5H₂O (2) have been prepared and their crystal structures determined by single-crystal X-ray diffraction. The crystal structures were solved by the direct methods and Fourier difference techniques, and refined by a least-squares method on the basis of F² for all unique reflections. Crystallographic data: 1, triclinic, space group , , b=9.762(4), , α=62.378(5), β=76.681(5), γ=73.858(5), Z=2, R₁=0.0335 for 172 parameters with 3430 reflections with I?2σ(I); 2, triclinic, space group , , b=9.51(3), , α=62.11(4), β=76.15(5), γ=73.73(5), Z=2, R₁=0.0325 for 172 parameters with 1742 reflections with I?2σ(I). The two isotypic structures are built from a three-dimensional (3D) arrangement of lanthanide and oxalate ions. The lanthanide atom is coordinated by eight oxygen atoms from four tetradentate oxalate ions and one aqua oxygen. Alternating lanthanide and oxalate ions form six-membered rings that delimit tunnels running down three directions and occupied by hydrazinium and water molecules. Starting from these lanthanide(III) compounds two isotypic mixed Ln(III)/U(IV) oxalates, (N₂H₅)_0.75[Nd_0.75U_0.25(C₂O₄)₂(H₂O)]·4.5H₂O (3) and (N₂H₅)_0.75[Gd_0.75U_0.25(C₂O₄)₂(H₂O)]·4H₂O (4), are obtained by partial substitution of Ln(III) by U(IV) in the nine-coordinated site, the charge excess being compensated by removal of monovalent ions from the tunnels. Finally, using Na⁺ gel, two mixed Ln(III)/U(IV) sodium oxalates, Na_0.5[Nd_0.5U_0.5(C₂O₄)₂(H₂O)]·3H₂O (5) and Na_0.65[Gd_0.65U_0.35(C₂O₄)₂(H₂O)]·4.5H₂O (6) have been obtained without any change in the 3D framework.     

U(IV)/Ln(III) unexpected mixed site in polymetallic oxalato complexes. Part I. Substitution of Ln(III) for U(IV) from the new oxalate (NH4)2U2(C2O4)5·0.7H2O

A new ammonium uranium (IV) oxalate (NH₄)₂U₂(C₂O₄)₅·0.7H₂O (1) and three mixed uranium (IV)-lanthanide (III) oxalates, (N₂H₅)_2.6U_1.4M_0.6(C₂O₄)₅·xH₂O (M=Nd (2) and M=Sm (3)), Na_2.56U_1.44Nd_0.56(C₂O₄)₅·7.6H₂O (4) and Na₃UCe(C₂O₄)₅·10.4H₂O (5), have been prepared. The crystal structures of compounds 1, 4 and 5 have been determined by single-crystal X-ray diffraction. The crystal structures were solved by the direct methods and Fourier difference techniques, and refined by a least square method on the basis of F² for all unique reflections. Compounds 2 and 3 are isotypic with 1. Crystallographic data: 1, hexagonal, space group P6₃/mmc, a=19.177(3), c=12.728(4) Å, Z=6, R₁=0.0575 for 52 parameters with 1360 reflections with I?2σ(I); 2, hexagonal, space group P6₃/mmc, a=19.243(4), c=12.760(5) Å, Z=6; 3, hexagonal, space group P6₃/mmc, a=19.211(3), c=12.274(4) Å, Z=6; 4, orthorhombic, space group Pbcn, a=18.79(3), b=11.46(1), c=12.77(2) Å, Z=4, R₁=0.0511 for 183 parameters with 3026 reflections with I?2σ(I); 5, monoclinic, space group C2/c, a=18.878(6), b=11.684(4), c=12.932(4) Å, β=95.97(1)°, Z=4, R₁=0.0416 for 213 parameters with 4060 reflections with I?2σ(I). The honeycomb-like structure of the five compounds is built from the same three-dimensional arrangement of metallic and oxalate ions. Similar hexagonal rings of alternating metallic and oxalate ions form layers parallel to the (001) plane that are pillared by another oxalate ion. Indeed, some torsions or rotations of the bridging oxalate ligands led to modifications of the network symmetry. The monovalent cations and the water molecules occupy the hexagonal tunnels running down the [001] direction. Starting from the uranium (IV) compound A₂U₂(C₂O₄)₅·0.7H₂O with A=NH₄⁺ (1), the mixed U(IV)/Ln(III) oxalates are obtained by partial substitution of U(IV) by Ln(III) in a ten-coordinated site, the charge deficit being compensated by intercalation of supplementary monovalent ions within the tunnels. The distortion of the arrangement in the [001] direction for the Na-containing compounds allows the accommodation of a greater number of water molecules that insure an octahedral coordination of the Na atoms.     

Solid phase extraction and preconcentration of uranium(VI) and thorium(IV) on Duolite XAD761 prior to their inductively coupled plasma mass spectrometric determination

A simple and effective method is presented for the separation and preconcentration of thorium(IV) and uranium(VI) by solid phase extraction on Duolite XAD761 adsorption resin. Thorium(IV) and uranium(VI) 9-phenyl-3-fluorone chelates are formed and adsorbed onto the Duolite XAD761. Thorium(IV) and uranium(VI) are quantitatively eluted with 2 mol L⁻¹ HCl and determined by inductively coupled plasma-mass spectrometry (ICP-MS). The influences of analytical parameters including pH, amount of reagents, amount of Duolite XAD761 and sample volume, etc. were investigated on the recovery of analyte ions. The interference of a large number of anions and cations has been studied and the optimized conditions developed have been utilized for the trace determination of uranium and thorium. A preconcentration factor of 30 for uranium and thorium was achieved. The relative standard deviation (N = 10) was 2.3% for uranium and 4.5% for thorium ions for 10 replicate determinations in the solution containing 0.5 μg of uranium and thorium. The three sigma detection limits (N = 15) for thorium(IV) and uranium(VI) ions were found to be 4.5 and 6.3 ng L⁻¹, respectively. The developed solid phase extraction method was successively utilized for the determination of traces thorium(IV) and uranium(VI) in environmental samples by ICP-MS.     

Coordination and extraction studies of an unexplored bi-functional ligand,carbamoyl methyl pyrazole (CMPz) with uranium(VI), lanthanum(III) and cerium(III) nitrates

The bi-functional carbamoyl methyl pyrazole ligands, C₅H₇N₂CH₂CONBu₂ (L₁), C₅H₇N₂CH₂CONⁱBu₂ (L₂), C₃H₃N₂CH₂CONBu₂ (L₃), C₃H₃N₂CH₂CONⁱBu₂ (L₄) and C₅H₇N₂CH₂CON(C₈H₁₇)₂ (L₅) were synthesized and characterized by spectroscopic and elemental analysis methods. The selected coordination chemistry of L₁ to L₄ with [UO₂(NO₃)₂ · 6H₂O], [La(NO₃)₃ · 6H₂O] and [Ce(NO₃)₃ · 6H₂O] has been evaluated. Structures for the compounds [UO₂(NO₃)₂ C₅H₇N₂CH₂CONBu₂] (6) [UO₂(NO₃)₂ C₅H₇N₂CH₂CONⁱBu₂] (7) and [Ce(NO₃)₃{C₃H₃N₂CH₂CONⁱBu₂}₂] (11) have been determined by single crystal X-ray diffraction methods. Preliminary extraction studies of the ligand L₅ with U(VI) and Pu(IV) in tracer level showed an appreciable extraction for U(VI) and Pu(IV) up to 10 M HNO₃ but not for Am(III). Thermal studies of the compounds 6 and 7 in air revealed that the ligands can be destroyed completely on incineration.     

Uranyl(VI) and lanthanum(III) thio-diglycolamides complexes: Synthesis and structural studies involving nitrate complexation

New tri-functional ligands of the type R₂NCOCH₂SCH₂CONR₂ (where R = iso-propyl, n-butyl or iso-butyl) were prepared and characterized. The coordination chemistry of these ligands with uranyl and lanthanum(III) nitrates was studied by using the IR, ¹HNMR and elemental analysis methods. Structures for the compounds [UO₂(NO₃)₂(ⁱPr₂NCOCH₂SCH₂CONⁱPr₂)] [UO₂(NO₃)₂(ⁱBu₂NCOCH₂SCH₂CONⁱBu₂)], [La(NO₃)₃(ⁱPr₂NCOCH₂SCH₂CONⁱPr₂)₂] and [La(NO₃)₃(ⁱBu₂NCOCH₂SCH₂CONⁱBu₂)₂] were determined by single crystal X-ray diffraction. These structures show that the ligand acts as a bidentate chelating ligand and bonds through both the carbamoyl groups to the uranyl and lanthanum(III) nitrate groups. Solvent extraction studies show that the ligand can extract the uranyl ion from the nitric acid medium but does not show any ability to extract the americium (III) ion.     

Group III quinaldates: synthesis,structure and photoluminescence

The reactions of Al(III), Ga(III) and In(III) nitrates with 2-quinaldic acid (qaH) afforded [Al₂(OH)₂(qa)₄]·2H₂O (1), [Ga(qa)₂(H₂O)₂]NO₃ (2) and [In(qa)₂(NO₃)(H₂O)] (3), respectively, in high yields. The crystal structures of 1, 2 and 3 have been determined by single-crystal X-ray crystallography. The structure of 1 features a di-hydroxo bridged [Al₂(μ-OH)₂]⁴⁺ dimer in which each Al(III) is further ligated by two bidentate chelate qa^? ligands. Complexes 2 and 3 are mononuclear with the M(III) ions in octahedral environments surrounded by two bidentate chelate qa^? and two H₂O in 2 or one H₂O and a terminal NO₃^? in 3. Characteristic IR as well as thermal analysis and solid-state fluorescence are discussed.     

Complex formation constants and thermodynamic parameters for La(III) and Y(III)L-serine complexes

Summary The stoichiometric stability constants for La(III) and Y(III)L-serine complexes were determined by potentiometric methods at different ionic strengths adjusted with NaClO₄ and at different temperatures. The overall changes in free energy (G ^o), enthalpy (H ^o), and entropy (S ^o) during the protonation ofL-serine and that accompanying the complex formation with the metal ions have been evaluated.

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Komplexbildungskonstanten und thermodynamische Parameter für La(III)- und Y(III)-L-Serin-Komplexe

Zusammenfassung Die stöchiometrischen Komplexbildungskonstanten für La(III)- und Y(III)-L-Serin-Komplexe wurden mittels potentiometrischer Methoden bei verschiedenen Ionenstärken (mit NaClO₄ adjustiert) und bei verschiedenen Temperaturen bestimmt. Die Änderungen in der freien Energie (G ^o), Enthalpie (H ^o) und Entropie (S ^o) während der Protonierung und der Komplexbildung mit den Metallionen wurden ermittelt.

     

Effect of the varying π-accepting properties of someortho-substituted benzoic acids on the stability of mixed-ligand complexes also containing quinizarin and thorium(IV)

The mixed-ligand complexes of thorium(IV) with quinizarin (quin) and as a second ligand,L, salicyclic acid (sa), thiosalicylic acid (tsa) or anthranilic acid (ant) were studied potentiometrically in 40% (v/v) ethanol-water medium [I=100 mmol dm^–3 (KNO₃), 25±0.1 °C]. The equilibria existing in solutions were demonstrated and the ternary stability constants of the 1:1:1 Th-quin-L-complexes were characterized. All of these biligand complexes are considerably more stable than the corresponding monoligand ones. In addition, the relatively most stable ternary complex is formed withant which is the best -acceptor. The order of stability of the ternary complexes is in accordance with the calculated -charge densities of the varying ligating group in the ligandL. The values of the equilibrium constants (log units) for the reaction: Th(quin)₂+ThL ₂2Th(quin)(L) are 2.47 (0.13), 2.60 (0.3) and 4.25 (0.86) for Th(quin)(tsa), Th(quin)(sa) and Th(quin)(ant), respectively. The constants given in parentheses correspond to logK _Th (= logK _Th(quin ^)(L)Th(quin) — logK _ThL ^Th ).

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Der Effekt verschiedener -Acceptoreigenschaften einiger ortho-substituierter Benzoesäuren auf die Stabilität von Komplexen mit gemischten Liganden unter Beteiligung von Chinizarin und Thorium(IV)

Zusammenfassung Die gemischtligandigen Komplexe von Thorium(IV) mit Chinizarin (quin) und als zweiten Liganden (L) Salizylsäure (sa), Thisalizylsäure (tsa) oder Anthranilsäure (ant) wurden potentiometrisch in 40% (v/v) Ethanol-Wasser [I=100 mmol dm^–3 (KNO₃),t=25±0.1 °C] untersucht. Die vorliegenden Gleichgewichte wurden formuliert und die ternären Stabilitätskonstanten der 1:1:1 Th-quin-L-Komplexe bestimmt. Alle zweiligandigen Komplexe sind wesentlich stabiler als die entsprechenden Monoligand-Komplexe. Der relativ stabilste Komplex wurde mitant gebildet, daant der beste -Acceptor ist. Die Reihung der relativen Stabilitäten stimmt mit den berechneten -Elektronendichten der verschiedenen LigandenL überein. Die Werte der Gleichgewichtskonstanten (in log Einheiten) für die Reaktion Th(quin)₂+ThL ₂2Th(quin)(L) sind 2.47 (0.13), 2.60 (0.30) and 4.25 (0.86) für Th(quin)(tsa), Th(quin)(sa) bzw. Th(quin)(ant), wobei die Werte in Klammern logK _Th = logK _Th(quin ^{)(L)/Th(quin)} — logK _ThL ^Th entsprechen.

     

Structural and thermal characterization of cerium, thorium and uranyl complexes of sulfasalazine

Cerium(IV), Thorium(IV) and Uranyl(II) complexes with the ammonium salt of sulfasalazine drug (H2SSZ, HL-) have been studied. The structures of the complexes were elucidated using elemental analysis, IR and mass spectroscopy and thermal analysis. The complexes were isolated in 1:1 and 1:2 (M:L) ratios. The solid monocomplexes (1:1) (M:H(2)SSZ) were isolated in the general formulae [UO2(L)(H2O)2].2H2O and [M(L)(X)z(H2O)n].yH2O (M=Ce(IV) and Th(IV) (X=NO3, z=2, n=2, y=0-3)). The biscomplexes (1:2) (M:H2SSZ) solid chelates found to have the general formulae [UO2(HL)2].2H2O and [M(L)2(H2O)2] (M=Ce(IV) and Th(IV)). The thermal decomposition of the complexes should be discussed in relation to structure, and the thermodynamic parameters of the decomposition stages were evaluated applying Coats-Redfern and Horwitz-Mitzger methods.     

Two- and three-dimensional coordination complexes constructed by 2-(1H-imidazol-1-methyl)-1H-benzimidazole: syntheses,structures, and fluorescent properties

Two new complexes, {[Zn(imb)(SO₄)]·H₂O}_n (1) and {[Cd₂(imb)₂(SO₄)₂(H₂O)]·CH₃OH}_n (2) (imb?=?2-(1H-imidazol-1-methyl)-1H-benzimidazole), have been solvothermally synthesized. Single-crystal X-ray diffraction shows that 1 displays a 2-D (4,4) network, which is further extended to a 3-D supramolecular structure by hydrogen bonding interactions. Complex 2 exhibits a 3-D framework with (3,5)-connected (4²·6)₂(4²·6⁵·8³)₂ topology. The results indicate that changing metal ions can influence the coordination modes of sulfate, and then affect the structures of the complexes. In addition, IR and UV–vis spectra, powder X-ray diffraction patterns, thermogravimetric analyses, and fluorescent properties of both complexes have been investigated.     

Solubility, dissociation and complexation with Nd(III) and Th(IV) of oxine, thenoyltrifluoroacetone and 1,10-phenanthroline in 5.0 m NaCl

Equilibria in the system of Nd(III) and Th(IV) with 8-hydroxyquinoline (oxine), thenoyltrifluoroacetone (HTTA) and 1,10-phenanthroline (phen) in 5.0 m NaCl solution have been investigated by spectroscopy and potentiometry. The solubility and deprotonation constants of the three organics were measured to be: pK_s = 3.09 ± 0.01, pK_a1 = 5.82 ±0.02, pK_a2= 10.00 ±0.01 for oxine; pK_s = 2.49 ± 0.01, pK_a1 = 6.47 ±0.03 for HTTA; pK_s = 2.86 ± 0.02, pK_a2 = 5.82 ± 0.05 for phen. The stabilities of the corresponding metal complexes are in the order M(oxine) > M(TTA) > M(phen), where M = Nd(III), Th(IV). For all three organic ligands, the Th(IV) complexation is stronger than that of Nd(III).     

Synthesis and coordination chemistry of organotin(IV) complexes of 2,3-methylenedioxyphenylpropenoic acid

The synthesis, spectroscopy, and antitumor behavior of organotin(IV) complexes of 2,3-methylenedioxyphenylpropenoic acid are described. The spectroscopic data indicate 1 : 2 and 1 : 1 metal to ligand stoichiometry in case of di- and trioganotin(IV) compounds and hypervalency of Sn(IV) in trigonal bipyramidal and octahedral modes. Mass spectrometric and elemental analysis data support the solid and solution spectroscopic results. The complexes have been evaluated in vitro against crown gall tumor and bio-activity screenings showed in vitro biological potential. The nature of covalent attachments (methyl, ethyl, n-butyl, phenyl, and n-octyl) of Sn(IV) played a decisive role for bioactivity. All the compounds have been studied in solution by NMR (¹H, ¹³C) and also in solid state using FTIR, mass spectrometry, and by X-ray crystallography. The molecular structure of Et₂Sn(IV) and Me₃Sn(IV) derivatives confirm the behavior of di- and tri-organotin(IV) compounds in solid state. Mono-organotin derivatives are octahedral both in solid and solution.     

Colorimetric detection of uranium(VI) on building surfaces after enrichment by solid phase extraction

A method for detecting and quantifying uranium(VI) levels on building materials that include concrete, Plexiglas, glass and steel surfaces is presented. Uranium(VI) was extracted from building material surfaces using a pH 2.2 buffer rinse and, subsequently complexed by an organic chelating agent, arsenazo III. The application of a uranium-chelating molecule, arsenazo III, allows for concentration enhancement using C₁₈ solid phase extraction and colorimetric detection of the uranium complex using ultraviolet-visible spectroscopy at 654 nm. The method has a detection limit (based on 3σ) of 40 ng/L (5 ng/cm²) and an overall extraction efficiency greater than 80% for each surface type (concrete, Plexiglas, glass, steel). Methods to prevent interference by metal ions commonly found on building materials are discussed.     

Synthesis,spectral, thermal and crystallographic investigations on oxovanadium(IV) and manganese(III) complexes derived from heterocyclic β-diketone and 2-amino ethanol

Novel mononuclear oxovanadium(IV) and manganese(III) complexes [VO(L¹)₂·H₂O] (1); [VO(L²)₂·H₂O] (2); [VO(L³)₂·H₂O] (3); [Mn(L¹)₂]ClO₄·H₂O (4); [Mn(L²)₂] ClO₄·H₂O (5); [Mn(L³)₂]ClO₄·H₂O (6) were prepared by condensation of 1 mol of VOSO₄·5H₂O or Mn(OAc)₃· 2H₂O with 2 mol of ligand HL¹, HL² or HL³ (where HL¹ = 4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2- phenyl-2,4-dihydro-pyrazol-3-one; HL²=4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2-p-tolyl-2,4-dihydro-pyrazol-3-one; HL³=4-{4-[(2-hydroxy-ethyl-amino)-methyl]-3-methyl-5-oxo-4,5-dihydropyrazol-1-yl} benzene sulfonic acid). The resulting complexes were characterized by elemental analyses, molar conductance, magnetic and decomposition temperature measurements, electron spin resonance, FAB mass, IR and electronic spectral studies. From TGA, DTA and DSC, the thermal behaviour and degradation kinetic were studied. Electronic spectra and magnetic susceptibility measurements indicate distorted octahedral stereochemistry of oxovanadium(IV) complexes and regular octahedral stereochemistry of manganese(III) complexes. Hamiltonian and bonding parameters found from ESR spectra indicate the metal ligand bonding is partial covalent. The X-ray single crystal determination of one of the representative ligand was carried out which suggests existence of amine-one tautomeric form in the solid state. The ¹H-NMR spectra support the existence of imine-ol form in solution state. The LC-MS studies sustain the¹H-NMR result. The electronic structure of the same representative ligand was optimized using 6-311G basis set at HF level ab initio studies to predict the coordinating atoms of the ligand.     

Iron(III) chloride and its coordination chemistry

Abstract

The coordination chemistry of FeCl₃ is distinctly different to that of the other 3d metal halides. It has a distinct preference for O-donor ligands. Although it primarily forms six-coordinate complexes, it has some distinctive features that set it apart from metals like Mn(II), Co(II), and Ni(II), such as the self-ionized complexes [FeL₄Cl₂]⁺ [FeCl₄]^?. There are a number of examples where very small changes in the coordination sphere tilt the balance between isomeric structures. Chloride has a significant steric effect in the coordination sphere as well as a greater trans-influence than water.     

Mononuclear gallium(III) complexes based on salicylaldoximes: Synthesis,structure and spectroscopic characterization

The reactions of Ga(acac)₃ with salicylaldoxime (saoH₂) and methyl-salicylaldoxime (Me-saoH₂) in dichloromethane/hexane afforded the complexes [Ga(acac)(saoH)₂] (1) and [Ga(acac)₃][Ga(acac)(MesaoH)₂] (2), respectively, in high yields. The crystal structures of 1 and 2 have been determined by single-crystal X-ray crystallography. Both complexes are mononuclear with the Ga(III) atoms being in octahedral environments surrounded by two bidentate chelate R-saoH⁻ and one bidentate chelate acac⁻ ligands. A [Ga(acac)₃] moiety has co-crystallized along with the methylsalicylaldoximato complex. Characteristic IR as well as NMR data are discussed in terms of the nature of bonding in the structures of the two complexes. ¹H and ¹³C NMR data in CDCl₃ indicate that the salicylaldoximato complexes isomerize in solution.     

Adaptable coordination of U(IV) in the 2D-(4,4) uranium oxalate network: From 8 to 10 coordinations in the uranium (IV) oxalate hydrates

Crystals of uranium (IV) oxalate hydrates, U(C₂O₄)₂·6H₂O (1) and U(C₂O₄)₂·2H₂O (2), were obtained by hydrothermal methods using two different U(IV) precursors, U₃O₈ oxide and nitric U(IV) solution in presence of hydrazine to avoid oxidation of U(IV) into uranyl ion. Growth of crystals of solvated monohydrated uranium (IV) oxalate, U(C₂O₄)₂·H₂O·(dma) (3), dma=dimethylamine, was achieved by slow diffusion of U(IV) into a gel containing oxalate ions. The three structures are built on a bi-dimensional complex polymer of U(IV) atoms connected through bis-bidentate oxalate ions forming [U(C₂O₄)]₄ pseudo-squares. The flexibility of this supramolecular arrangement allows modifications of the coordination number of the U(IV) atom which, starting from 8 in 1 increases to 9 in 3 and, finally increases, to 10 in 2. The coordination polyhedron changes from a distorted cube, formed by eight oxygen atoms of four oxalate ions, in 1, to a mono-capped square anti-prism in 3 and, finally, to a di-capped square anti-prism in 2, resulting from rotation of the oxalate ions and addition of one and two water oxygen atoms in the coordination of U(IV). In 1, the space between the _∞²[U(C₂O₄)₂] planar layers is occupied by non-coordinated water molecules; in 2, the space between the staggered _∞²[U(C₂O₄)₂·2H₂O] layers is empty, finally in 3, the solvate molecules occupy the interlayer space between corrugated _∞²[U(C₂O₄)₂·H₂O] sheets. The thermal decomposition of U(C₂O₄)₂·6H₂O under air and argon atmospheres gives U₃O₈ and UO₂, respectively.     

Synthesis,electrochemical and antimicrobial studies of mono and binuclear iron(III) and oxovanadium(IV) complexes of [ONO] donor tridentate Schiff-base ligands

Tridentate Schiff bases (H₂L¹ or H₂L²) were derived from condensation of acetylacetone and 2-aminophenol or 2-aminobenzoic acid. Binuclear square pyramidal complexes of the type [M₂(L¹)₂]?·?nH₂O (M?=?Fe–Cl, n?=?0; M?=?VO, n?=?1) were accessed from interaction of H₂L¹ with anhydrous FeCl₃ and VOSO₄?·?5H₂O, respectively. A similar reaction with H₂L², however, produced mononuclear complexes [ML²(H₂O) _x ]?·?nH₂O (M=Fe–Cl, x?=?0, n?=?0; M=VO, x?=?1, n?=?1). The compounds were characterized using elemental analysis, FT-IR, UV-Vis, and NMR (for ligand only), and mass spectroscopies and solution electrical conductivity studies. Magnetic susceptibility measurements suggest antiferromagnetic exchange in binuclear Fe(III) and VO(IV) complexes. Thermo gravimetric analysis (TGA) provided unambiguous evidence for the presence of coordinated as well as lattice water in [VOL²(H₂O)]?·?H₂O. Cyclic voltammetric studies showed well-defined redox processes corresponding to Fe(III)/Fe(II) and VO(V)/VO(IV). In vitro antimicrobial activities of the compounds were investigated against Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeroginosa, Escherichia coli, Bacillus subtilis, and Proteus vulgaris. H₂L¹ and its binuclear complexes exhibited pronounced activity against all the microorganisms tested.     

Transition metal chemistry of oxime containing ligands,VII

Complexes of pyridine-2-aldoxime (Hpox) with iron(II) and chromium(III) of type, [Fe(Hpox)₂ X ₂] (X=Cl, Br, I or NCS); [Cr(Hpox)₃]Cl₃·3 H₂O; [Cr(Hpox)₂ X ₂]ClO₄ (X=F, Cl or Br) and [Cr(Hpox)₂(H₂O)₂]Br₃·H₂O were prepared and characterized by analytical X-ray powder diffraction, magnetism, vibrational (conventional and far-infrared) and electronic spectroscopy techniques. X-ray and electronic spectral data indicate that all the complexes except [Cr(Hpox)₃]Cl₃·3 H₂O havetrans-pseudo-octahedral microsymmetry around the metal ion. Infrared spectral data indicate that the ligand, Hpox, behaves like a neutral ligand and coordinates to the metal ion through pyridine nitrogen atom and oxime nitrogen atom in all these complexes. The magnetic susceptibilities of chromium(III) complexes, measured over a temperature range 300–78 K, are independent of temperature whereas the magnetic moments of iron(II) complexes over a temperature range 300–20 K are dependent of temperature. The observed temperature dependence of magnetic moments of iron(II) complexes was used to evaluate the magnitude of orbital reduction factor,k, the low-symmetry distortion parameter, , and the extent of reduction in spin-orbital coupling, . In all these iron(II) complexes the magnetic results indicate the presence of an orbitally non-degenerate,⁵B_2g, ground state. Magnetically unperturbed and perturbedMössbauer spectra of iron(II) complexes at various temperatures have also been reported. Magnetically perturbedMössbauer spectra of iron(II) complexes at 4.2 K in an axial field of 60kGauss indicate that the principal component of electric field gradient tensor is positive and consistent with⁵B_2g ground electronic state in a tetragonal (D _4h) local site symmetry.

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Übergangsmetallkomplexe mit Oxim-enthaltenden Liganden, VII. Elektronische und strukturelle Eigenschaften vonFe(II)-undCr(III)-Komplexen mit Pyridin-2-aldoxim

Zusammenfassung Es wurden Komplexe von Pyridin-2-aldoxim (Hpox) mit Fe(II) und Cr(III) vom Typ [Fe(Hpox)₂ X ₂] (X=Cl, Br, I, NCS), [Cr(Hpox)₃]Cl₃·3 H₂O, [Cr(Hpox)₂ X ₂]ClO₄ (X=F, Cl, Br) und [Cr(Hpox)₂(H₂O)₂]Br₃·H₂O hergestellt. Charakterisierung und Diskussion von Geometrie und Bindungsverhalten in den Komplexen erfolgte auf Grund von analytischen Daten, Röntgen-Pulveraufnahmen, Elektronenanregungsspektroskopie, Infrarotspektroskopie, magnetischen Messungen undMössbauer-Spektroskopie.

     

Structural studies on 3-acetyl-1,5-diaryl and 3-cyano-1,5-diaryl formazan chelates with cerium(III), thorium(IV) and uranium(VI)

Summary Solid complexes of 3-acetyl-1,5-diaryl and 3-cyano-1,5-diaryl formazans were prepared and characterized by elemental analysis, IR, NMR, TGA and DTA analyses. Based on these studies, the suggested general formula for the complexes is [M(HL) _m (OH^–) _n or (NO ₃ ^– or Cl^–) _x ·(H₂O) _y or (C₂H₅OH orDMSO) _z , where HL=formazanM=Ce³⁺, Th⁴⁺, and UO ₂ ²⁺ ,m=1–2,n=0–3,x=0–3,y=0–4 andz=0–3. The metal ions are expected to have coordination numbers 6–8.

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Strukturuntersuchungen an 3-Acetyl-1,5-diaryl- und 3-Cyan-1,5-diaryl-formazan-Chelaten mit Cer(III), Thorium(IV) und Uran(VI)

Zusammenfassung Die hergestellten Chelate wurden mittels Elementaranalyse, IR, NMR, TGA und DTA charakterisiert. Darauf basierend wird die generelle Formel [M(HL) _m (OH^–) _n bzw. (NO ₃ ^– oder Cl^–) _x ·(H₂O) _y oder (C₂H₅OH bzw.DMSO) _z ] vorgeschlagen, wobei HL=Formazan,M=Ce³⁺, Th⁴⁺ oder UO ₂ ²⁺ ,m=1–2,n=0–3,x=0–3,y=0–4 undz=0–3. Die Metallionen haben Koordinationszahlen von 6–8.