Metal benzoylpivaloylmethanates. Part II. 1,4-dioxane adducts of copper(II) chelates

Summary 1 : 1 Dioxane adducts of Copper(II) chelates withpara-subtituted benzoylpivaloylmethanes have been synthesized and their u.v., vis., i.r., mass, e.p.r. spectra as well as their magnetic moments and thermal stabilities investigated. Powdered samples of undiluted magnetically adducts were found to give well resolved e.p.r. spectra; the (S = 1) g_| signal being split into nine lines. Magnetic susceptibilities measured down to 4 K did not reveal exchange interactions. The uncommon structure of the e.p.r. spectra is believed to be due to the dimeric structure of the adduct in which an interion dipolar zero-field splitting of the triplet state occurs. The Cu-Cu distance estimated from the e.p.r. D_dd parameter is found to be 7.4 Å.     

CRYSTAL STRUCTURE,SPECTRAL AND MAGNETIC BEHAVIOR OF COPPER(II)(5-CHLOROSALICYLATO)2 (AQUA)2

Abstract

The synthesis and characterization of Cu(5-Clsal)₂(H₂O)₂ (5-Clsal = 5-chlorosalicylate) are reported. Characterization of the compound was based on elemental analysis, electronic and EPR spectra, and magnetic susceptibility measurement over a temperature range 93–239 K.

An X-ray analysis of Cu(5-Clsal)₂(H₂O)₂ was carried out, showing a polymeric chain of copper(II) atoms bridged by pairs of water molecules with Cu-O(bridge) bond lengths of 1.970(2) and 2.718(2)Å. The coordination sphere about each copper(II) atom is completed (on the X-axis) by a trans-pair of unidentate 5-chlorosalicylate anions. The bridging oxygen atoms arrange a planar Cu₂O₂ rhombus. The relationship between degree of distortion and g-values from EPR spectra is also discussed.     

N -oxide bridged manganese(II) coordination polymers

A simple method for synthesis of manganese(II) coordination polymers with different benzoate ligands and pyridine N-oxide having general composition [Mn(RC₆H₄CO₂)₂(PyO)] _n is presented (where PyO = pyridine N-oxide and R = H, 1a; R = 4-NO₂, 1b; R = 4-Cl, 1c; R = 4-OH, 1d; R = 2-NO₂, 1e). All these polymers are characterized by X-ray crystallography and other spectroscopic techniques. The coordination polymers have similar structures, but the positions of the manganese atoms differ. For example, 1c is highly symmetric and a mirror plane exists between each manganese site (2/m). In 1d, the manganese centers are related by an inversion center (?1) whereas in 1e the manganese centers are related by C₁ rotation (1). Reaction of manganese(II) acetate tetrahydrate with 4-chlorobenzoic acid and PyO upon crystallization from methanol/pyridine gave crystals of coordination polymer 1c along with aqua-bis-pyridine bis-4-chlorobenzoato manganese(II) (2). The structure of 2 also determined by single-crystal X-ray diffraction has a 1-D hydrogen bonded chain structure. Temperature-dependent zero-field cooled and field-cooled magnetization data of 1a–1c measured at 20 Oe and 1000 Oe show field-dependent magnetization spread over a wide temperature range from 5 to 300 K. These coordination polymers show anti-ferromagnetic behavior below 20 K.     

SOME METAL COMPLEXES OF α, β, γ, δ-TETRA-(4-PYRIDYL) PORPHINE

Abstract

The zinc (II), copper (II), nickel (II), cobalt (II), chloromanganese (III), and chloroiron (III) complexes of α, β, γ, δ-tetra-(4-pyridyl)-porphine (4-TPyP) were prepared. The magnetic susceptibilities from near 0° to 90° K and at room temperature were measured for solid Cu(4-TPyp), Ni(4-TPyP), Co-(4-TPyP), ClMn(4-TPyP) · H₂ O and ClFe(4-TPyP). The Mössbauer spectra of ClFe(4-TPyP) were obtained at several temperatures. The infrared spectra and d-spacings were obtained for all of the solids. Electronic spectra of the complexes in pyridine and, where possible, in 0.1 N HCl solution were recorded. Evidence of intermolecular interaction was found for Co(4-TPyP), Ni(4-TPyP), and ClFe(4-TPyP).     

A new tetranuclear copper(II) complex containing decameric water clusters bridged by–OH–and pyridine-2,4, 6-tricarboxylate: synthesis and magnetic characterization

Using pyridine-2,4,6-tricarboxylic acid (H₃ptc) and 2,2-bipyridine (2,2-bipy), a tetranuclear copper(II) compound [Cu₄(2,2-bipy)₄(ptc)₂(H₂O)₂(OH)₂] · 12H₂O (1) has been isolated under hydrothermal conditions. Variable temperature magnetic susceptibility of 1 from 2–300 K indicates anti-ferromagnetic interactions. The magnetic exchange coupling constants of J = ?159.4 and J′ = ?18.66 cm^?1 for 1 can be obtained through fit of the magnetic data, corresponding to two kinds of bridges, hydroxyl anions (OH^?) and pyridine carboxylate oxygen of ptc^3?. Moreover, decameric water clusters can also be observed, which are located between these tetranuclear copper(II) entities, forming a series of intricate O-H ··· O hydrogen bonds and stabilizing the resulting three-dimensional (3-D) hydrogen-bonded framework structure.     

Interpretation of EPR and optical spectra of Ni(II) ions in crystalline lattices at ambient temperature

Many biologically important paramagnetic metal ions are characterized by electron paramagnetic resonance (EPR) spectroscopy to use as spin probes to investigate the structure and function of biomolecules. Though nickel(II) ions are an essential trace element and part of many biomolecules, the EPR properties are least understood. Herein, the EPR and optical absorption spectra measured at 300 K for Ni(II) ions diluted in two different diamagnetic hosts are investigated and reported. The EPR spectrum of a polycrystalline Ni/Mg(3-methylpyrazole)₆(ClO₄)₂ [Ni/MMPC] shows two transitions at X-band frequency (~9.5 GHz), suggesting the zero-field splitting parameter (D) is larger than the resonance field of the free electron (H_o). This incomplete and complex spectrum is successfully analyzed to obtain EPR parameters. The EPR spectrum of the polycrystalline Ni/Zn(pyrazole)₆(NO₃)₂ [Ni/ZPN] shows a triplet spectrum indicating D < H_o. A detailed analysis of single-crystal EPR data yielded the spin Hamiltonian parameters. The optical absorption spectra are deconvoluted to understand the symmetry of the coordination environment in the complex.     

Synthesis and magnetic properties of copper (II)-manganese (II) compounds with N,N′-ethylenedisalicylamidatocuprate(II)

By the reaction of sodium N,N′-ethylenedisalicylamidatocuprate ( I ) pentahydrate, Na₂[Cu(samen)]·5H₂O, with a manganese ( I ) salt and 2,2′-dipyridyl (bpy) or 1,10-phenanthroline (phen), the binuclear metal complexes [Cu(samen) Mn(L)₂] (L ? bpy, phen) have been synthesized. Based on IR, elemental analyses and electronic spectra, the complexes are proposed to consist of a four-coordinated Cu( I ) in a distorted planar environment and Mn( I ) in a distorted octahedron. The complexes have been characterized with variable-temperature magnetic susceptibility (4.2—300 K) and the susceptibility data were least-squares fit to susceptibility equation derived from the spin Hamiltonian including single-ion zero-field interaction for Mn²⁺ ion, H?—2JS₁·S₂—DS, where D is the axial zero-field splitting parameter for the Mn(II) ion. The exchange integral, J, was found to be —34.6 and —28.8 cm^?1 for [Cu(samen)Mn(bpy)₂] and [Cu(samen)Mn(phen)₂] respectively. The weak antiferromagnetic spin-exchange interaction can be interpreted by considering σ-π exchange pathway.     

Reaction of copper(II) fluoro- and chloroacetates with triphenylphosphine oxide

Triphenylphosphine oxide adducts of copper(II) dichloro-, trichloro- and trifluoroacetate were prepared. Electronic, IR and EPR spectra as well as magnetic data over the temperature range 81–301 K have been mainly used for the determination of the stereochemistry and electronic structure of the adducts. The spectral and magnetic behaviours of the adducts are similar to that of copper(II) acetate hydrate. Some correlations between the magnetic and spectral data as well as the acidity of the respective acids are discussed. Cu(F₃CCOO)₂Ph₃PO, represent the first example of a stable binuclear copper(II) trifluoroacetate adduct.     

SYNTHESIS AND SPECTROSCOPIC STUDIES OF SOME NEW REDOX-ACTIVE BENZYLAMINE COMPLEXES OF COPPER(II) AND ESR STUDIES OF THEIR OXIDATIONREDUCTION PRODUCTS

Abstract

New Cu(II) complexes Cu(L′_x)₂, where L′_x=L′₁, L′₂, L′₃, L′₄ are monoanion of unsubstituted, 5-Cl, 5-Br and 3,5-di-Br-substituted 2-hydroxybenzylamines of redox-active N-(3,5-di-tert-butyl-1-hydroxyphenyl)-2-hydroxybenzylamines were synthesized. Each compound of L′_xH and Cu(L′_x)2 as well as products of their oxidation and reduction by PbO2 and PPh3, respectively, was characterized by IR, UV-visible and ESR spectroscopy. ESR results showed that one-electron oxidation of mononuclear tetrahedrally distorted Cu(L′_x)2 chelates with PbO2, via C-C coupling of the Cu(II)-stabilized ligand radical intermediates and by the oxidative dehydrogenation of amine-chelates, produce new Cu(II) complexes with square-planar geometry. The powder ESR spectra of these new Cu(II) complexes exhibit a triplet-state type pattern with the zero-field splitting due to interaction between the copper(II) pairs. Interaction of Cu(L′_x)2 with PPh3 via intramolecular ligand-metal electron transfer results in the formation of radical species and reduction of the metal center. All radical intermediates were characterized by ESR parameters.     

Pyridine-based complexes of copper(II) chloride and bromide: ligand conformation effects on crystal structure. Synthesis,structure and magnetic behavior of Cu(2-Cl-3-X′py)2X2 [X,X′ = Cl,Br]

Abstract

Reaction of copper(II) chloride or bromide with 2-chloro-3-bromopyridine or 2,3-dichloropyridine generates a family of compounds of the general formula L₂CuX₂ (1–4). X-ray crystallography shows that the bromide complexes (3-bromo-2-chloropyridine)dibromidocopper(II) (1) and (2,3-dichloropyridine)dibromidocopper(II) (3) are particularly unusual in that they crystallize with both the syn- and anti-conformation structures in the same crystal. A review of the literature on complexes of the formula (substituted-pyridine)₂CuX₂ suggests that these are the first examples of such complexes. The members of the family show a variety of magnetic behaviors and variable temperature magnetic susceptibility data indicate that 1 is essentially paramagnetic (θ = ?0.9(1) K) while 3 is weakly ferromagnetic (J?=?2.9(1) K). Compound 2 [(3-bromo-2-chloropyridine)dichloridocopper(II)] is fit by the uniform 1-D antiferromagnetic model (J = ?19.6(1) K), while 4 [(2,3-dichloropyridine)dichloridocopper(II)] exhibits weak anti-ferromagnetic interactions (J = ?3.68(3) K).     

Bis -(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine complexes of copper(II), nickel(II), and cobalt(II)

A series of Cu(II), Co(II), and Ni(II) complexes of bis-(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine C₁₅H₂₆N₅P (1), prepared from 3-aminopropylphosphine and 1-hydroxymethyl-3,5-dimethylpyrazole were characterized. The nature of bonding and the geometry of the complexes have been deduced from elemental analysis, infrared, electronic, ¹H NMR, ³¹P NMR spectra, magnetic susceptibility, and conductivity measurements. The studies indicate octahedral geometry for nickel complex and square pyramidal geometry for copper and cobalt complexes. The EPR spectra of copper complex in acetonitrile at 300 K and 77 K were recorded. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus by well-diffusion method. The zone of inhibition values were measured at 37°C for a period of 24 h. The electrochemical behavior of copper complexes was studied by cyclic voltammetry. Catalytic study indicates the copper complex has efficient catalytic activity in oxidation of amitriptyline.     

INFRARED ASSIGNMENT OF BIS(GLYCOLATO)-BIS(PYRIDINE) METAL(II) COMPOUNDS AND CRYSTAL STRUCTURE OF TRANS-BIS(GLYCOLATO)-CIS-BIS(PYRIDINE)NICKEL(II) DIHYDRATE

Abstract

Infrared spectra of the coordination compounds [MG₂(py)₂], M(II)=Co, Ni, Cu and Zn; G=glycolato, py=pyridine, have been fully assigned by means of py and py-d ₅ and glycolato α—OH and α—OD (G-d) labelling as well as metal ion substitution in the 4000–70cm^?1 region. The crystal structure of the Ni(II) compound is presented and the spectra of the compounds are discussed on the basis of their structure and their bonding to the glycolato and pyridine ligands. Vibrational frequencies obtained for the Ni(II) compound are compared to those obtained by calculations carried out using the Gaussian 94 program package.     

A binuclear copper(II) complex with unusual magnetism

A binuclear copper(II) complex [Cu₂ (μ-pyo)₂Br₄] _n (where pyo = pyridine N-oxide) has been synthesized and its structure determined by X-ray crystallography. This complex crystallizes in monoclinic, space group P2₁/c, with unit cell dimensions a = 11.020(3) Å, b = 10.049(3) Å, c = 7.905(2) Å, β = 110.609(3)°, and Z = 2. The structure was refined to final R = 0.0311 and wR = 0.0721 for 1302 observed reflections (I > 2σ(I)). In the complex, two Cu(II) ions are bridged by two pyo ligands and four bromides coordinate the Cu(II); the distance between the bridged Cu(II) ions is 3.261 Å. The variable-temperature (4–300 K) magnetic susceptibility data show that the magnetic moment is zero. Thus, there exists very strong anti-ferromagnetic coupling between the bridged binuclear Cu(II) ions. Density functional calculations yield a singlet-triplet splitting 2J = ?1355 cm^?1.     

Crystal Structure and Magnetic Properties of a Hexanuclear Copper(II) Carboxylate

The synthesis and characterisation of the hexanuclear copper(II) carboxylate complex [Cu(O₂CCHPhOC₂H₄OC₂H₄OCH₃)₂]₆ ( 1 ) is described. Single‐crystal X‐ray structure analysis reveals that the copper(II) ions are arranged in a six‐membered ring which adopts a chair‐like conformation. The copper(II) ions are bridged by μ₂‐ and μ₃‐coordinating carboxylates. The magnetic behavior of 1 was measured between 2 and 300 K, revealing at low temperature a weak antiferromagnetic interaction. The χ_M(T) dependency was fitted mathematically with one coupling constant J₁ and a paramagnetic impurity α.     

Synthesis,crystal structure and properties of a 1D copper(II) complex with 1,5,9-triazacyclododecane bridged by p -benzenebicarboxylate

A 1D complex [{[Cu₂([12]aneN₃)₂(p-paa)(H₂O)₂](ClO₄)₂}[Cu₂([12]aneN₃)₂(p-paa)₂]] _n ([12]aneN₃ = 1,5,9-triazacyclododecane, p-paa = p-benzenebicarboxylate) has been synthesized and structurally characterized. The complex contains two different binuclear copper(II) moieties. One part includes a binuclear copper(II) unit and non-coordinated perchlorate anions. A neutral binuclear copper(II) part which forms a zigzag chain structure via the bridging p-paa ligand completes the unit-cell. Elemental analysis, IR, UV-Vis spectra and magnetic properties for the complex have also been determined. Magnetic susceptibilities in the solid state are measured over the temperature range from 77 to 300 K, showing a weak antiferromagnetic coupling with a best fit J ₁ = ?3.09 cm^?1, J ₂ = ?5.279 cm^?1, g = 2.099 and R = 1.226 × 10^?5.     

Temperature dependence of the Mössbauer spectrum and magnetic susceptibility [Fe(uridine)Cl2]∞: Novel magnetic ordering of transition metal complexes based on nucleoside ligands

The zero-field Mössbauer spectra and magnetic susceptibility of a polycrystalline sample of the polymeric material [Fe(uridine)Cl₂]_∞ have been measured in the temperature range 1.7-300 K. The compound exhibits two magnetic transitions. The isomer shift and quadrupole splitting indicate a distorted pseudo-octahedral FeCl₄O₂ chromophore resulting from condensation to a network structure via chloro and uridine ligand bridging.     

E.p.r. studies on dichloromono(1-phenylamidino-o-alkylurea)copper(II) complexes. Evidence for field induced partial ordering in the solid state and some unusual features in solution

E.p.r. and optical absorption studies have been conducted on dichloromono(1-phenylamidino-o-alkylurea)copper(II) complexes (Alkyl = Me, Et, Pr, Bu or Pe). The e.p.r. spectra of solids, recorded at 300 K, confirmed the square-planar geometry with the unpaired electron in the dx ²–y ² orbital of copper. Magnetic field-induced partial molecular alignment has been observed in some of the polycrystalline samples when cooled in a magnetic field of 1 T at 77 K. E.p.r. spectra at 77 K in pyridine and DMF has shown axial ligation of solvent molecules (pyridine and DMF), whereas in MeOH and DMSO at least three structurally different Cu^II species have been identified. These features are consistent with differences in electronic absorption spectra in the powder and in solution.     

Synthesis and Characterization of Copper(II) and Zinc(II) Tricyanomethanide (tcm) Complexes with Di(2‐pyridyl)amine (dpyam) as Co‐ligands: [Cu(dpyam)(tcm)2], [Cu(dpyam)(tcm)(OAc)] and Zn(dpyam)2(tcm)2

Three new transition metal tricyanomethanide complexes [Cu(dpyam)(tcm)₂] ( 1 ), [Cu(dpyam)(tcm)(OAc)] ( 2 ) and Zn(dpyam)₂(tcm)₂ ( 3 ) were synthesized and characterized by single crystal X‐ray diffraction analysis. In 1 each copper(II) atom is coordinated to three tcm anions and one dpyam molecule to form a square pyramide geometry. In 2 the coordination geometry around the central metal is also square pyramidal, and each copper atom is surrounded by two tcm anions, one dpyam ligand and one OAc. Both 1 and 2 display a µ_1,5‐tcm bridged infinite chain structure. In 3 each zinc(II) atom is coordinated by two tcm anions and two dpyam molecules to form a distorted octahedral geometry. Different from the former two complexes, 3 shows a mononuclear structure. Magnetic susceptibility measurement in the range 2–300 K indicates that there are weak antiferromagnetic couplings between adjacent copper(II) ions in 1 (J=?0.03 cm^?1) and 2 (J=?0.11 cm^?1) respectively.     

Synthesis,crystal structure and magnetic property of a one-dimensional copper(II) complex with 2,5-dimethylpyrazine-1,4-dioxide as bridging ligand

A one-dimensional polynuclear copper(II) complex [Cu(μ_1,6-dmpzdo)(SCN)₂] _n (where dmpzdo?=?2,5-dimethylpyrazine-1,4-dioxide) has been synthesized and its crystal structure determined by X-ray crystallography. The coordination geometry of Cu(II) atom is a square plane and each Cu(II) ion is connected by two μ_1,6-dmpzdo bridging ligands, leading to the formation of a one-dimensional chain. ESR spectra indicate magnetic coupling between the bridged Cu(II) ions. The fitting of the variable-temperature magnetic susceptibility data (4–300?K) gave 2J?=??68.69?cm^?1.     

A thiophenopolyamine Cu(II) complex fixed by atmospheric carbon dioxide: synthesis,structure and properties

A new trinuclear complex, {[Cu(L)]₃ (μ₃-CO₃)}(ClO₄)₄ (L = N-(2-thiophenoethyl)-N,N-bis (3-aminopropyl)amine), was synthesized and characterized by single-crystal X-ray analysis. The complex contained three identical mononuclear copper(II) units connected by the μ₃-carbonate formed from atmospheric carbon dioxide. The electronic and magnetic properties were studied by cyclic voltammetry and the measurement of magnetic susceptibility, respectively. The μ₃-bridging model revealed weak ferromagnetic coupling of Cu(II), with the J value of ?11.28 cm^?1 and the Zeeman splitting g value of 2.06, which were determined by means of magnetic measurements in the 2–300 K range.