Synthesis,structure and spectroscopic properties of CuL(MeOH), H2L = (E)-N 1-(2-((2-aminocyclohexydiimino)(phenyl)methyl)-4-chlorophenyl)-N 2-(2-benzyl-4-chlorophenyl)oxalamide

A new kind of copper(II) complex, CuL(MeOH) (H₂L?=?(E)-N ¹-(2-((2-aminocyclohexydiimino)(phenyl)methyl)-4-chlorophenyl)-N ²-(2-benzyl-4-chlorophenyl)oxalamide) has been synthesized and its structure determined by single-crystal X-ray methods. Copper(II) ion is five-coordinate, bonding to four nitrogen atoms from H₂L and one oxygen atom from MeOH. Hydrogen bonds in the crystal result in the formation of a one-dimensional structure. EPR spectra are discussed. Computer simulation gave g_||?=?2.200, g_⊥?=?2.002. On the basis of the synthesis and the crystal structure, the mechanism of the metal template reaction involved in the formation of the complex was verified.     

A five-coordinate copper(II) perchlorate complex with tris(N-methylbenzimidazol-2-ylmethyl)amine and salicylate

A five-coordinate copper(II) complex with the tripod ligand tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) and salicylate, with the composition [Cu(Mentb) (salicylate)](ClO₄) · 2DMF, was synthesized and characterized by elemental and thermal analyses, electrical conductivity, IR and UV-Vis spectral measurements. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. The Cu(II) is five-coordinate with four N atoms from the Mentb ligand and an O atom of the monodentate salicylate ligand. The N₄O donors are in a distorted trigonal-bipyramid geometry. Cyclic voltammograms indicate a quasireversible Cu²⁺/Cu⁺ couple. The X-band EPR spectrum of the complex confirms the trigonal-bipyramidal structure with g_∥ < g _⊥ and a very small value of A_∥ (41 × 10^?4 cm^?1).     

Spectrophotometric Determination of Cobalt(II), Nickel(II) and Copper(II) with Acenaphthenequinone Monosemicarbazone (AQSC)

Cobalt(II), nickel(II) and copper(II) complexation with acenaphthenequinone monosemicarbazone (AQSC) has been studied spectrophotometrically. The Co(II), Ni(II) and Cu(II) complexes are soluble in ethanol medium and exhibit maximum absorbance at 410, 420 and 430 nm, respectively. The sensitivity of the reactions are 0.012, 0.02 and 0.01 μg/cm² for cobalt, nickel and copper systems. All the three complexes show maximum and constant absorbance in the pH range 8.4 to 9.8, 6.3 to 8.4 and 5.4 to 8.0 for Co-AQSC, Ni-AQSC and Cu-AQSC, respectively. Nickel and copper in some alloys have also been analysed.     

Synthesis,spectral, and biological studies of transition metal chelates of N-[1-(3-aminopropyl)imidazole]salicylaldimine

Tridentate chelate complexes M[LX?·?2H₂O], where M?=?Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have been synthesized from the Schiff base L?=?N-[1-(3-aminopropyl)imidazole]salicylaldimine and X?=?Cl. Microanalytical data, UV-Vis, magnetic susceptibility, IR, ¹H-NMR, mass, and EPR techniques were used to confirm the structures. Electronic absorption spectra and magnetic susceptibility measurements suggest square-planar geometry for copper complex and octahedral for other metal complexes. EPR spectra of copper(II) complex recorded at 300?K confirm the distorted square-planar geometry of the copper(II) complex. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans by the well diffusion method. The activity data show the metal complexes to be more potent than the parent ligand against two bacterial species and one fungus. The electrochemical behavior of the copper complex was studied by cyclic voltammetry.     

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.     

Thermodynamics of ligand exchange reactions between bis(dithiocarbamato)copper(II) and copper(II) salts. An EPR study

EPR spectroscopy was chosen to investigate the ligand exchange reactions between copper(II) bis(dithiocarbamate), Cu(dtc)2, and copper(II) salts which proceeds with the formation of mixed-ligand complexes of the type Cu(dtc)X, where X = Cl, NO3, ClO4. Large concentrations of 1:1 mixed-ligand complexes of this type are obtained as indicated by the EPR spectra of acetone, CHCl3/EtOH, CHCl3/i-PrOH, CCl4/EtOH and CCl4/i-PrOH, solutions of Cu(dtc)2 and the appropriate copper(II) salt CuCl2, Cu(NO3)2 or Cu(ClO4)2. Double integration of Cu(dtc)2 EPR signals obtained at temperatures between 240 and 310 K affords the calculation of the equilibrium constant (K) of the reaction: Cu(dtc)2 + CuX2 <==> 2 Cu(dtc)X in all solvents as a function of T. From the values of K the stability constant beta of the mixed-ligand complexes has been derived. The error associated with the calculated stability constant is +/- 10%. Thermodynamic parameters (deltaH0, deltaG0 and deltaS0) are determined from the temperature dependence of K as measured by EPR spectroscopy.     

EPR study of the atom transfer radical polymerization (ATRP) of (meth)acrylates

Electron paramagnetic resonance (EPR) spectroscopy was applied to atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and methyl acrylate (MA) in order to investigate the mechanism of the controlled/“living” radical polymerization system. Although initially only copper(I) species was added to the system as a catalyst, EPR signals of copper(II) species were observed during the polymerization of MMA initiated by ethyl 2-bromoisobutyrate and p-methylbenzenesulfonyl chloride, and polymerization of MA initiated by methyl 2-bromopropionate. As the polymerization proceeded, the concentration of copper(II) increased gradually until a steady state was reached. The EPR results indicate that 5–6% of copper(I) species converted to copper(II) species in polymerization of MMA and about 3% in polymerization of MA at 90°C.     

Exchange interactions in bis(diethyldithiocarbamato)copper(II), Cu(detc)2

The exchange coupling constant J in bis(diethyldithiocarbamato)copper(II) has been derived through analysis of the EPR g values and linewidth as a function of orientation, frequency and temperature. The single line in the ac* plane is due to the averaging of the fine-structure splitting by interdimer exchange for which a lower limit of 0.02 cm^?1 has been obtained. Analysis of the spectra in the bc plane gives an estimate of 0.008 cm^?1 for the intersite exchange.     

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.     

ZINC(II), CADMIUM(II), MERCURY(II) AND LEAD(II) SEMIQUINONE-TYPE COMPLEXES OF A NEW SCHIFF-BASE LIGAND: ANTIBACTERIAL STUDIES

Abstract

A new Schiff-base ligand LH₂, has been prepared by reaction of 2,9-diformv 1-1,10-phenan-throline with 2,3-diamino-l,4-naphthoquinone. The formation and characterization of complexes of Zn(II), Cd(II), Hg(II) and Pb(II) with the semi-oxidized ligand LH is described. The M(LH)X₂ (X = CI, Br and AcO) radical species are paramagnetic and the observed EPR signals in the solid state at room temperature, with g values close to the electron free g value are proof of the semiquinonic character of the ligand. The antibacterial activity of the ligand and the metal complexes prepared were tested against four bacteria strains and compared with the activity of penicillin.     

Magnetic and structural properties of trans-bis ( -isoleucine) copper(II)

A magnetic and structural characterization of single crystals of the copper derivative of the amino acid -isoleucine, Cu[NH₂(CH)₂CH₂(CH₃)₂CO₂]₂, was performed by EPR and X-ray diffraction techniques. The complex crystallizes in the orthorhombic space group Aba2, with a = 11.165(3) Å, b = 11.111(3) Å, c = 25.985(6) Å, and Z = 8. The copper ions occupy sites of point symmetry C₂. The position and peak-to-peak linewidth of the single EPR line observed were measured at 9.7 GHz and 293 K in three perpendicular planes of the sample. The gyromagnetic tensor has near axial symmetry around , with a small anisotropy in the perpendicular plane, in agreement with the orthorhombic symmetry indicated by the crystallographic results. The principal values of are g₁ = 2.0607(5), g₂ = 2.0616(5), and g₃ = 2.2619(3), with principal directions parallel to the crystal axes. The observed angular variation of the linewidth suggests a layered arrangement of the copper ions.     

Hyaluronic acid-copper(II) complexes: Spectroscopic characterization

Hyaluronic acid-copper(II) complexes were studied by ultraviolet and electron spin resonance spectroscopy (ESR), as well as by rheological measurements. Spin-Hamiltonian parameters were obtained from experimental spectra measured at 200 K by non-linear optimization method. These showg _x g _y <g _z and indicate the ground electronic state of copper ion, which is characteristic for carboxylato-copper(II) complexes. The non-axial symmetry of theg-tensor suggest rhombic crystal field symmetry. Formation of HA-Cu(II) complex is realized through the interaction of copper ions with carboxyl groups of the HA macromolecule. This complex is characteristic of the network-like rheological properties of its aqueous solution.     

E.p.r. and spectroscopic studies of configurational changes in 1,4-diazacycloheptane copper(II) complexes

Summary E.p.r. and spectroscopic studies of bis(1,4-diazacycloheptane)copper(II) perchlorate, bromobis(1,4-diazacycloheptane)copper(II) perchlorate and dibromo-bis(1,4-diazacycloheptane)copper(II), were carried out in MeNO₂, DMSO and H₂O solutions as well as in the polycrystalline state. The ligation of bromide ion to bis(1,4-diazacycloheptane)copper(II) along thez-axis was investigated. The e.p.r. spectra are explained in terms of energy changes involving the electronic ground state and the lowest excited state as a function of ligation of nucleophiles to the metal atom along thez-axis. In the polycrystalline state, the weaker the apical interaction (square-planar species) the lower theg-value and the higher the copper(II) hyperfine coupling constant. In the liquid state, theg-values observed in non-coordinating solvents such as MeNO₂ are similar to those for the polycrystalline material suggesting structural similarity in the two states. The electronic absorption maxima for the three complexes in the liquid state shift to higher energy with an increase in tetragonal distortion around copper(II). In strongly coordinating solvents the e.p.r. spectra and absorption maxima are independent of the anion present. The increasing strength of solvation results in an increase in the wavelength of the optical transition and theg-values, and a decrease in the copper(II) hyperfine coupling constant. It appears that an increase in the basicity of the solvent has the same effect on thed-orbital energy levels and on the unpaired electron density on copper(II)_as does increasing the electronegativity of the substituents on the ligand.     

EPR spectra and structures of dinuclear copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with acyldihydrazones of benzenedicarboxylic acids

Spacer-armed dinuclear copper(II) complexes with condensation products of isophthalic and terephthalic acid dihydrazides with salicylaldehyde and 2-hydroxyacetophenone were synthesized and studied by EPR and X-ray diffraction. The compositions and structures of most of the complexes were determined by elemental analysis, thermogravimetric analysis, and IR spectroscopy. The structure of the copper(II) complex with acyldihydrazone of salicylaldehyde and 1,3-benzenedicarboxylic acid (H₄L) with the composition [Cu₂L¹·2morph·MeOH] (morph is morpholine) was established by X-ray diffraction. The Cu^II atoms are spaced by 10.29 Å and are structurally nonequivalent. One copper cation has a square-planar coordination formed by donor atoms (2 N + O) of the doubly deprotonated acylhydrazine fragment and the N atom of the morpholine molecule. The second copper atom is additionally coordinated by a methanol molecule through the oxygen atom, so that this copper atom is in a tetragonal-pyramidal coordination with the oxygen atom in the axial position. The EPR spectra of liquid solutions of the complexes based on 1,4-benzenedicarboxylic acid acyldihydrazones and 1,3-benzenedicarboxylic acid bis(salicylidene)hydrazone at room temperature show a four-line hyperfine structure with the constant a _Cu = 54.4–67.0·10⁻⁴ cm⁻¹ (g = 2.105–2.147), which is indicative of the independent behavior of the paramagnetic centers. The EPR spectrum of a solution of the complex based on isophthalic acid and 2-hydroxyacetophenone shows the seven-line hyperfine structure corresponding to two equivalent copper nuclei (g = 2.11, a _Cu = 36.5·10⁻⁴ cm⁻¹). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1898–1905, October, 2007.     

Cis‐trans Isomerism in Copper(II) Complexes with N‐acyl Thiourea Ligands

The N‐acyl thiourea complexes bis[N,N‐diethyl‐N′‐(p‐nitrobenzoyl)‐thioureato]copper(II) ( 1a,1b ) and bis(N,N‐diphenyl‐N′‐benzoylthioureato)copper(II) ( 2a,2b ) crystallize in each case in two modifications. X‐ray structural analysis shows that 1a and 1b are cis‐trans isomers. This is very unusual for N‐acyl thioureato complexes because with exception of one platinum(II) complex up to now only cis complexes have been found. In contrast X‐ray structural analysis of both forms 2a and 2b of the other complex shows no cis‐trans pair. Both modifications are cis complexes. In solution both isomers of the copper(II) complexes are observable by EPR spectroscopy.     

Synthesis and photochemical degradation of copper(II) <Emphasis Type="Italic">ortho</Emphasis>-azidobenzoate

An aqua complex of copper(II) ortho-azidobenzoate was synthesized. The formula of this complex, [Cu(OH)ABA 2H₂O]₂ (ABA is ortho-azidobenzoate), was determined by IR, UV, and EPR spectroscopy and volumetric analysis (from the amount of nitrogen released upon dissolving the aqua complex in dry DMF). It was found that, in this aqua complex, the azido group is not coordinated to the copper(II) ion. On the dissolution of the aqua complex in dry organic solvents, such as DMF, DMSO, dioxane, and methanol, it underwent dehydration followed by the coordination of the azido group to copper(II) to convert into a chelate complex. The chelate complex in the solid state was stable at room temperature; however, it slowly degraded in solutions to liberate nitrogen. Dissolution in dry THF did not result in the dehydration of the complex. In the photolysis of the aqua complex in dry THF or a THF-water mixture, photochemical dehydration yielding the chelate complex occurred along with the degradation of the azido group and the formation of copper(II) anthranilate.Translated from Khimiya Vysokikh Energii, Vol. 39, No. 2, 2005, pp. 135–139.Original Russian Text Copyright © 2005 by Budruev, Levina, Karyakina, Oleinik.This revised version was published online in April 2005 with a corrected cover date.     

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.     

EPR of vanadyl ion in a natural mineral, apophyllite

Single crystal EPR spectra of a natural mineral, apophyllite, containing VO(II) ion as an impurity have been investigated. The EPR spectra of the mineral, as obtained, was complex in nature, but was simplified by annealing the crystals at 490 K. The EPR parameters of the VO(II) species in the annealed crystal,g _∥ = 1.924 (2);g _⊥ = 1.983 (2);A _∥ = 18.35 (5); andA _⊥ = 7.24 (5)mT, are very close to a typical VO(II) impurity. Theoretically calculated line positions, using second-order hyperfine terms in the spin Hamiltonian with an axially symmetricg andA tensor values, agreed very well with the experimental ones. The EPR analysis of the annealed crystal has further revealed that the most preferred location of the VO(II) impurity is a substitutional Ca(II) site. The calculated bonding parameters and admixture coefficients indicate a fair amount of covalent bonding in the complex.     

EPR Evidence For Magnetic Exchange Through a Four-Carbon Aliphatic Bridge in a Binuclear Copper(II) Complex. Single Crystal X-Ray Structure of 7, 7′-(1, 4-Butanediyl)-Bis{2,12-Dimethyl-3,7,11,17-Tetraazabicyclo[11.3.1]Heptadeca-1(17),2,11,13,15-Pentaene)Nickel(II)} Perchlorate Monohydrate

The single crystal x-ray structure of the title, binuclear nickel(II) complex has been determined and the compound used as a host for EPR investigations of the analogous copper(II) complex. The impetus for this work was an earlier suggestion that magnetic exchange interactions detected by EPR spectroscopy on frozen solutions of the biscopper(II) complex were a result of a direct copper-copper interaction in a “closed” conformation of the binuclear species. Results reported here suggest that the complex exists in the open conformation where the distance between metal centres is maximized and that the magnetic exchange occurs by a super-exchange mechanism through the aliphatic chain. The │J│ value for the exchange interaction is greater than 0.018 cm^-1. Crystal data for [Ni₂(C₃₄H₅₀N₈](CIO₄)₄-H₂O(298 K): monoclinic, space group P2₁/n, a = 13.560(3), b = 11.678(2), c = 15.377(3) Å, β = 108.48(2)°, ρ_caled = 1.588 g cm^-3 for Z = 2 and M _r = 1104.1, R = 0.068, R _w = 0.076. The intramolecular Ni-Ni distance is 9.13 Å. The analogous copper complex is isomorphorus with the nickel complex.     

Preparation of a novel polymeric ligand containing a tetraaza macrocycle supported on polystyrene,and separation of copper(II) and nickel(II)

The novel polymeric ligand containing the tetraaza macrocycle as a pendant group was prepared by the reaction of 2,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,5,7,12-tetraene with iodomethylstyrene-divinylbenzene copolymer beads. The content of the ligand in the polymer was 0.75 mmol g⁻¹ under the optimum conditions. The complexation of this polymer with copper(II) and nickel(II) in water under heterogeneous conditions in a batch system showed that it can bind copper(II) selectively by complex formation with the tetraaza macrocycle. The capacity for copper(II) was found to depend on the pH, ionic strength and ethanol content of the sample solutions. Moreover, the separation of nickel(II) and copper(II) was achieved in a column system.