A single-crystal ESR study of bis(1,1-diisobutyl-3-benzoyl-selenoureato)-copper(II)

A single-crystal ESR study of bis(1,1-diisobutyl-3-benzoyl-selenoureato)copper(II) is reported. From the ⁷⁷Se-hfs the Se atoms of the CuSe₂O₂ coordination sphere were found to be in cis-position. In addition covalency considerations of the Cu-chalcogeno bonds have been made.     

Über die Koordinationstendenz saurer Aminogruppen. XVIII. Struktur- und Bindungsverhältnisse von Bis-(3-phenyl-5-pyridyl(2)-pyrazolato)-kupfer(II) - eine ESR-Studie

Bis-(3-phenyl-5-pyridyl(2)-pyrazolato)-copper(II), [Cu(PPP)₂], a brown paramagnetic nonionic chelate, is studied by ESR techniques in solution and as powder (diamagnetically diluted). The ESR spectra can be interpreted by means of a spin-Hamiltonian of axial symmetry. The bonding parameters of Cu–N bonds were calculated by interpretation of the g, Cu hfs and ¹⁴N-ligand hfs tensors. From these parameters follows that the degree of covalency of the s?- and π-bonds increases in comparision to other cationic copper(II) chelates (e.g. ethylenediamine complexes). These results are in good agreement with the chemical behaviour of [Cu(PPP)₂].     

Studies on the <Emphasis Type="Italic">g</Emphasis>-factors of the copper(II)–oxygen compounds

The g factors for Cu²⁺ in meta-zeunerite (Cu(UO₂)₂(AsO₄)₂·3H₂O), kroehnkite (Na₂Cu(SO₄)₂·2H₂O), copper benzoate (Cu(PhCO₂)₂·3H₂O) and diaboleite (Pb₂Cu(OH)₄Cl₂) of the tetragonal phase are uniformly treated by high order perturbation formulas for 3d ⁹ ions in tetragonally elongated octahedra. The calculation results are in good agreement with the observed values and systematically analyzed in view of the local structures around Cu²⁺. The g anisotropies Δg (= g _‖?g _⊥) are largely ascribed to the local tetragonal elongations of the Cu²⁺ sites, characterized by the relative elongation ratios (R _‖?R _⊥)/R? ≈ 19%, 21%, 27% and 30% for metazeunertie, kroehnkite, copper benzoate and diaboletie, respectively. The anomalous valley (minimum) of relative g anisotropy for copper benzoate is attributed to the modification of the Cu²⁺ electronic states due to the phenyl ring. The ligand orbital contributions are found to be significant due to covalency, and should be taken into account. The present study would be helpful to the unified investigations of structures and properties of the copper oxygen compounds.     

Physico‐Chemical Studies on Cu(II) Complexes of Acrylate Chelating Polymers

Abstract

Metal chelating polymers containing amide and carboxylic groups were prepared by gamma‐radiation polymerization of acrylic acid (AA) monomers in the presence of polyacrylamide (PAM). The resins obtained were loaded by copper ions and characterized by FT‐IR spectroscopy, electron spin resonance (ESR), thermogravimetric analysis (TGA), and differential scanning calorimetery (DSC). The IR spectra indicated a lower frequencies shift in the carbonyl bands due to copper ion chelation with carbonyl groups in the polymer resins. Also, the IR spectra reveal a splitting in the band at 3600–3200?cm^?1 that due to the coordination of the NH and OH groups with copper ions. The ESR spectrum was anisotropic with hyperfine structure having the following values 2.3808 and 2.07218 for g _∥ and g _⊥, respectively. These spectra for copper ions have square planar coordination with two nitrogen and two oxygen atoms. TGA and DSC studies show that radiation crosslinking and complexation with copper ion increase the thermal stability of PAM–AA resins. Meanwhile, resin complexes with copper ion showed a higher thermal stability than pure resin. The increase in thermal stability may be correlated with the metal ions coordination with NH and OH groups; this coordination prevents the splitting of ammonia and water molecules. Also, the metal ions providing a coordination crosslink between polymer chains could increase thermal stability.     

Two yttrium(III) coordination compounds containing a3-ptz or atza [a3-ptz = 5-[N-acetato(3-pyridyl)]tetrazole; atza = 5-aminotetrazole-1-acetato]

Two yttrium(III) coordination compounds, [Y(a3-ptz)₂(H₂O)₅]Cl?·?4H₂O (1) and [Y(atza)₂(H₂O)₂(CH₃OH)]Cl (2) [a3-ptz?=?5-[N-acetato(3-pyridyl)]tetrazole; atza?=?5-aminotetrazole-1-acetato], have been synthesized. Single-crystal X-ray diffraction analysis reveals that 1 has a distorted monocapped square-antiprism coordination geometry around Y^III. Complex 2 is a distorted pentagonal bipyramid with coordination from four atza ligands, two waters, and one methanol; the coordination of atza in 2 leads to its 1-D polymeric chain structure. 1 and 2 are self-assembled to form 3-D supramolecular structures through hydrogen bonds. The luminescence properties of 1 and Ka3-ptz were investigated at room temperature in the solid state.     

Spectral,magnetic, thermal and electrochemical studies on new copper(II) thiosemicarbazone complexes

The chelation behavior of some =N(1) and NH(4) thiosemicarbazones towards copper(II) ions has been investigated. The isolated complexes are characterized by elemental analysis, magnetic moment, electronic, IR, ESR and ms spectra, and by thermal and voltammetric measurements. The substituents on =N(1) and/or NH(4) thiosemicarbazones and the log K values of the ligands play an important role in complex formation. The IR spectra showed that the reagents HAT, HAET, HAPT, HApClPT, H₂ST and HBT are deprotonated in the complexes and act as mononegative SN donors; H₂SET, H₂SpClPT, H₂HyMBPT and H₂HyMBpClPT, as binegative NSO donors while H₂SPT is a mononegative NSO donor. The ESR spectra of the complexes are quite similar and exhibit axially symmetric g-tensor parameters with g _‖?>?g _⊥?>?2.0023. The loss of thiol and/or hydroxyl hydrogen was confirmed from potentiometric titrations of the ligands and their copper(II) complexes. The protonation constants of the ligands as well as the stability constants of their Cu(II) complexes were calculated. Thermogravimetric analysis of the complexes suggests different decomposition steps. The Coats–Redfern and Horowitz–Metzger equations have been used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. The redox properties, nature of the electroactive species and the stability of the complexes towards oxidation are strongly dependent on the substituents on the precursor NH(4) thiosemicarbazone. The redox data are discussed in terms of the kinetic parameters and the reaction mechanism.     

Copper (II) complexes of sterically hindered o-diphenol derivatives: synthesis, characterization and microbiological studies

Cu (II) complexes with the sterically hindered diphenol derivatives 3,5-di(tert-butyl)-1,2-benzenediol (I), 4,6-di(tert-butyl)-1,2,3-benzenetriol (II) and the sulfur-containing 4,6-di(tert-butyl)-3-(2-hydroxyethylsulfanyl)-1,2-benzenediol (III) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (IV) have been synthesized and characterized by elemental analysis, TG/DTA, FT-IR, ESR, XPS, XPD and conductivity measurements. Compounds I–III can coordinate in their singly deprotonated forms and act as bidentate ligands. These compounds yield Cu (II) complexes of the stoichiometry Cu(L)₂, which have square planar geometry (g_| > g_⊥ > g_e). Unlike them, compound IV behaves as a terdentate ligand, and its complex Cu(L^IV)₂ has distorted octahedral geometry. According to ESR data, only the Cu(L^II)₂ complex contains a very small amount of phenoxyl radicals. Antimicrobial activities of these ligands and their respective Cu (II) complexes have been determined with respect to Gram-positive and Gram-negative bacteria, as well as on yeasts. Their phytotoxic properties against Chlorella vulgaris 157 were also examined.     

Characterization of copper(II) complexes of N4,N4-disubstituted thiosemicarbazones of 2-acetylpyridine by combined evaluation of electronic and ESR parameters

Copper(II) complexes of 2-acetylpyridine 4,4-dimethyl-3-thiosemicarbazone (L′H) and 2-acetylpyridine 4-(4-methylpiperidinyl)-3-thiosemicarbazone (LH) of the general formula CuLX (where L is a deprotonated ligand and X = F⁻, Cl⁻, Br⁻, I⁻, OAc⁻ and NO⁻₃) have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements between 93 and 298 K in the polycrystalline state, i.r. spectra, electronic spectra, conductivity measurements and ESR spectra recorded in the polycrystalline state, in chloroform and dimethylformamide solution at room temperature and at 77K. The molar conductivities measured in dimethylformamide for all complexes show them to be non-electrolytes. The terdentate character of the ligands in all the complexes is inferred from i.r. spectral studies. The i.r. spectra also confirm the monodentate nature of the polyatomic anions such as nitrate and acetate. The electronic spectra in Nujol mulls, chloroform or dimethylformamide solution suggest planar geometry for all of the complexes. The calculated ESR parameters show an axial d_x²−y² ground state and suggest coordination through sulphur in agreement with the i.r. results. Little change in the value of g with temperature indicates no significant change in planarity of these four coordinated species. ESR spectra in solution at room temperature and 77 K also suggest a strong covalent environment with strong in-plane sigma and pi bonds provided by the ligands.     

Spectroscopic,magnetic and thermal studies on complexes of Cu(II) and VO2+ with diacetylmonoxime derivatives: new method for extraction of Cu(II)

The coordination behavior of Cu(II) and VO²⁺ towards some oximes has been investigated. The isolated complexes were characterized by elemental analysis, molar conductance, magnetic moment, spectra (electronic, IR, ESR and mass) and thermal measurements. The IR spectra showed most ligands are deprotonated during complex formation acting as mononegative bi- or tridentate, binegative tetradentate and neutral tridentate. The magnetic moments and electronic spectra showed octahedral, square pyramidal and square-planar structures for the Cu(II) and VO²⁺ complexes. The ESR spectra of the complexes are quite similar and exhibit axial symmetric g-tensor parameters with g _∥ > g _⊥ > 2.0023 and confirmed the structures. The TG curves showed decomposition steps and indicate stability of the complexes. The ligands can remove Cu(II) ions from water by flotation technology using oleic acid surfactant with high efficiency.     

ELECTRON SPIN RESONANCE OR Pd(I). III: The Nature of the Metal-ligand Bonds in Square Planar Complexes of Palladium(I)

Abstract

ESR spectra for a variety of palladium(I) complexes produced in the powders and the frozen solutions of palladium(II) complexes by γ -ray irradiation have been interpreted in terms of the nature of the metal-ligand bonds. It has been found that the covalency for the palladium-ligand σ-bond increases in the order of Pd[sbnd]O, Pd[sbnd]Cl < Pd[sbnd]N < Pd[sbnd]S, Pd[sbnd]C, and that the nature of the metal-ligand bond in palladium(I) complexes is very similar to that in copper(II) complexes. The ratio of the magnitude of the ligand field splitting for palladium(I) complex to that for the copper(II) complex with the same ligand has been estimated from the comparison of their g values.     

Investigation of 3,5-dichlorosalicylate-copper(II)-(3-pyridylmethanol or N,N′-diethylnicotinamide) complex systems by EPR spectroscopy

Copper(II) complex systems, containing 3,5-dichlorosalicylic acid (3,5-Cl₂salH) and different copper salts (Cu(ac)₂ or CuSO₄), with varying concentrations of 3-pyridylmethanol (ronicol, ron) or N,N′-diethylnicotinamide (denia) as ligands, were prepared. The effects of Cu(II) salts containing anions of different basicity and two different N-donor ligands with varying ligand-to-metal ratio (x) on the formation of the resultant complexes in the water/methanol solutions were studied by EPR spectroscopy at low temperature of 98 K. When ligand concentration was increased, the resolution and signal intensity of the ¹⁴N perpendicular super-hyperfine splitting patterns increased (for ron more progressively), becoming saturated at higher ligand concentrations. In comparing the ronicoland denia-containing systems, both g-factors (g _⊥, g _‖) are systematically higher and the parallel hyperfine splitting (A _‖) systematically lower in denia-containing systems for both Cu(II) salts.     

ESR-Spektren von CuN4-Chromophoren II: Komplexe mit Ammoniak, Äthylendiamin,Biguanid, N-Trifluoracetimidoyl-trifluoracetamidin,N-Trichloracetimidoyl-trichloracetamidin,Tetraaza-undecan,Hexamethyl-tetraaza-cyclotetradecan und -cyclotetra decadien in Einkristallen

The ESR spectra of eight copper complexes with two groups of nitrogen ligands have been measured in the solid state. The first group includes the σ-bonding ligands ammonia, ethylenediamine, 1,4,8,11-tetraaza-undecane, and the macrocyclic hexamethyl-1,4,8,11-tetraazacyclotetradecane of CURTIS . Ligands of the second group are biguanide, the CF₃ and CCl₃ derivatives of acetimidoyl-acetamidine, and hexamethyl-1, 4,8,11-tetraazacyclotetradecadiene. Single crystals of the parent Pt^II, Ni^II, or Zn^II compounds were used as host lattices and magnetic diluents. The spectra of the chromophores CuN₄, showing resolved hyperfine structure due to copper and nitrogen nuclear spins, are fitting a Spin-Hamiltonian on the basis of virtual site symmetry D_4h. The parameters g∥, g?, A∥, and A? were used to derive delocalization coefficients in terms of the LCAO-MO model introduced by MAKI and MC GARVEY . The comparative study clearly reveals that no reliable information on π-bonding is provided by application of this model. The results on σ-bonding ligands are particularly valuable in showing that the simple LCAO-MO model cannot account for the attenuation of spin orbit coupling due to σ-bonding in a physically meaningful way. Our results are qualitatively in agreement with AMMETER'S explanation of this phenomenon in terms of a virtual expansion of the d-shell in antibonding orbitals.     

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

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

Synthesis and crystal structure of a copper(II) complex of the tripodal tetradentate ligand tris(2-benzimidazolylmethyl)amine

A mononuclear copper complex [Cu(NTB)Cl]Cl·3CH₃CH₂OH (1) (NTB?=?tris(2-benzimidazolylmethyl)amine) was synthesized and its structure was determined by single crystal X-ray diffraction. In this complex, copper(II) is five-coordinate with NTB serving as a neutral tetradentate ligand. Three tertiary nitrogen atoms of benzimidazole groups of NTB formed the base of the trigonal bipyramidal geometry. One axial position was occupied by the apical nitrogen atom of NTB and the other was occupied by chloride. The ESR spectrum of complex 1 in ethanol at 101?K was recorded and the well-defined ESR parameters (g _∥?=?2.02, g _⊥ =?2.16 and A _∥ ^?=?109?G) indicated that the Cu(II) has a distorted trigonal-bipyramidal environment, in good agreement with crystal structure determination for complex 1.     

ESR-Untersuchungen an Tetramesitylmolybdän(V) – einem homoleptischen σ-Arylübergangsmetallkation

ESR Investigations on Tetramesityl Molybdenum(V) – a Homoleptic σ-Aryl Transition Metal Cation An ESR investigation on the homoleptic σ-aryl transition metal cation tetramesityl molybdenum(V) is reported. The ESR parameters can be interpreted by means of a D_2d ligandfield model (distorted tetrahedral symmetry, B₁ ground state). Analyzing the ^95,97Mo hyperfine splitting the hyperfine parameters P and K are derived. They indicate a very low value for the effective nuclear charge on the molybdenum: ≈ +0.4. The covalency degree of the Mo? C σ bonds is considerably larger than that observed for tetramesityl vanadium(IV). The small anisotropy of the g tensor indicates the presence of remarkable charge-transfer interactions.     

Supramolecular structural and spectral perspectives of novel ruthenium(III) azodye complexes

Five bis-[5-(4′-R-phenylazo)-8-hydroxyquinoline] ruthenium complexes [RuLn?·?Cl₂?·?OH₂]; where Ln?=?5-(4′-R-phenylazo)-8-hydroxyquinolinol, R?=?OCH₃ (n?=?1), CH₃(2), H(3), Cl(4), NO₂(5), have been prepared and characterized on the basis of elemental analyses, IR, ¹H NMR, ESR, thermal analysis and magnetic susceptibility measurements. The data show that these complexes exist in trans-isomeric solid form. Two inversion-related ligands and two Ru³⁺ atoms form a cage-like dimer. Both ligands of the dimer are bridged by a pair of inversion-related Ru–N (azodye) bonds. The octahedral coordination geometry of Ru³⁺ is made up of an N of pyridine, the deprotonated quinoline O atom, one of the azodye N atoms, two chlorides and one water. The ligands in the dimer are stacked over one another. In the solid state of azo-8-hydroxyquinoline, the dimers have inter-and intramolecular hydrogen bonds. Interactions between the ligands and the metal are discussed. The azo group was involved in chelation for all the prepared complexes. The effect of Hammet's constant on the ligand field parameters are also discussed and drawn.     

Correlation of zero-field splittings and site distortions: Variation of b2 FOR Mn2+ with ligand and coordination number

The intrinsic zero-field splitting parameter $\text{b}$₂ increases monotonically with increasing covalency of the Mn-X bonds, but depends on coordination number and type of metal ion. At least two effects of opposite sign must contribute to this complicated behavior. The trigonal distortions of the MX^4?₆ octahedra in some MX₂ layer compounds are evaluated.     

(2‐Aminopyrimidine‐κN1)aqua(pyridine‐2,6‐dicarboxylato‐κ3O2,N,O6)copper(II): X‐ray and DFT calculated structure

In the title compound, [Cu(C₇H₃N₂O₄)(C₄H₅N₂)(H₂O)], (I), pyridine‐2,6‐dicarboxylate (pydc²⁻), 2‐aminopyrimidine and aqua ligands coordinate the Cu^II centre through two N atoms, two carboxylate O atoms and one water O atom, respectively, to give a nominally distorted square‐pyramidal coordination geometry, a common arrangement for copper complexes containing the pydc²⁻ ligand. Because of the presence of Cu...X_bridged contacts (X = N or O) between adjacent molecules in the crystal structures of (I) and three analogous previously reported compounds, and the corresponding uncertainty about the effective coordination number of the Cu^II centre, density functional theory (DFT) calculations were used to elucidate the degree of covalency in these contacts. The calculated Wiberg and Mayer bond‐order indices reveal that the Cu...O contact can be considered as a coordination bond, whereas the amine group forming a Cu...N contact is not an effective participant in the coordination environment.     

Synthesis and Characterization of New Schiff Bases 2-(2-(2-(Aryl)Methyleneamino)Phenylthio) Ethylthio)-N-((aryl)Methylene)Benzeneamine

A series of Schiff bases containing four to six coordination sites N₂S₂ X₂(X = O,N) 2-(2-(2-(aryl)methyleneamino)phenylthio)ethylthio)-N-((aryl)methylene)benzeneamine (2c–f) were prepared from the reaction of 1,2-di(2-aminophenylthio)ethane (1) with aromatic aldehydes. All compounds were characterized by means IR, mass, ¹H and ¹³C NMR spectroscopy, and elemental analysis, and in the case of 2b with a single crystal X-ray diffraction. The X-ray crystal structure of 2b showed that the resonance occurs between aromatic rings, through the C=N bonds of the molecule.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Cu(bapen)M(CN)<Subscript>4</Subscript>·H<Subscript>2</Subscript>O complexes exhibiting chain-like structures (bapen = N,N′-bis(3-aminopropyl)-1,2-diaminoethane,M = Ni,Pd): preparations,crystal structures,spectroscopic and magnetic properties

Single crystals of Cu(bapen)Ni(CN)₄·H₂O and Cu(bapen)Pd(CN)₄·H₂O (bapen = N,N′-bis(3-aminopropyl)-1,2-diaminoethane) were isolated from the aqueous systems copper(II)—bapen—[M(CN)₄]^2? (M = Ni, Pd). Crystals of the two compounds are isostructural and are built up of two crystallographically independent quasi-linear chains [-Cu(bapen)-μ₂-NC-Ni(CN)₂-μ₂-CN-] _n and solvate water molecules. The copper(II) centers exhibit the usual distorted octahedral coordination with one tetradentate bapen ligand in the equatorial plane (mean Cu–N are 2.030 Å for Cu(bapen)Ni(CN)₄·H₂O and 2.018 Å for Cu(bapen)Pd(CN)₄·H₂O), while the axial positions are occupied by nitrogen atoms from μ₂-bridging cyanido ligands with longer Cu–N bonds (mean values are 2.544 Å for Cu(bapen)Ni(CN)₄·H₂O and 2.543 Å for Cu(bapen)Pd(CN)₄·H₂O). One of the two independent coordinated bapen ligands is disordered, as are the water molecules of crystallization. The Ni and Pd atoms in both studied compounds exhibit the usual square coordination with the bridging cyanido ligands trans to each other. Several OH···O, N–H···O and N–H···N hydrogen bonds enhance the stability of the structures. ESR spectra corroborated the presence of Jahn–Teller anisotropy at the copper(II) atoms. Magnetic studies in the temperature range 1.8–300 K reveal that both Cu(bapen)Ni(CN)₄·H₂O and Cu(bapen)Pd(CN)₄·H₂O follow Curie-Weiss laws with θ = ?0.51 K and θ = ?0.34 K, respectively, suggesting the presence of weak antiferromagnetic interactions.