Spectra Of Cu Research Articles

Synthesis, spectral characterisation and cytotoxic effect of metal complexes of 2-(2-(4-carboxyphenyl)guanidino) acetic acid ligand

A new series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Sr(II), Hg(II), Ag(I), Tl(I) and UO2(II) complexes of 2-(2-(4-carboxyphenyl)guanidino)acetic acid ligand have been synthesised and characterised by elemental analyses, IR, UV-Vis spectra, mass spectra (ligand and its zinc(II) complex), 1H NMR spectra (ligand and its mercury(II) complex), magnetic moments, conductances, thermal analyses (DTA and TGA) and ESR measurements. The IR data show that, the ligand behaves as neutral tridentate, (2), [(H2 LL)3 CCu2 ((OAc)4 ((H2 OO)2 ] ], neutral bidentate, (3), [(H2LL)Cu(OAc)2]].1/2H2OO, (13), [(HL)2CCuCl2((H2OO)2]], (17), [(H2LL)Cu(OOSO2))(H2OO)J,dibasic hexadentate, (4), [(L) Ni4((OAc)6((H2OO)J.4H2OO, (5), [(L)Mn4(OAc)6(H2O)10]. 4H2O, (6), [(L)Co4(OAc)6(H2O)10] . 4H2O, monobasic bidentate, (7), [(HL)(UO2)(OAc)(H2O)3], (12), [(HL)2Cu], (15), [(HL)2Fe2(Cl4)(H2O)2]. 7H2O, (16), [(HL)2Cr2(Cl4)(H2O)2]. 7H2O, (21 ), [(H2L)Cd (OOSO2)(H2O)3]. 2H2O, monobasic tridentate, (8), [(L)2HHg2((OAc)2 (H2O)6].H2O, (9), [(L)2Zn2(OAc)2(H2O)6].H2O, (10), [(L) 2ZZn2((OAc)2((H2OO)6]].H2OO, (11), [(L)Tl4(OAc)3 (H2O)6], (18), [(HL)(OH)Cr2(SO4)2(H2O)5]. H2O, (19), [(HL)3Ag3NO3], or dibasic tridentate, (14), [(L) Sr(Cl)20 ((H2 OO)24 ]], (20), [(L)3 CCu (H2 OO)2 ] ]. Molar conductances in DMF indicate that, the complexes are non-electrolyte. The ESR spectra of Cu(II) complexes (2), (3) and (20) at room temperature show axial type symmetry with g// > g-> 2.00, indicating a d(x2-y2) ground state with significant covalent bond character in an octahedral or square planar geometry. However, Cu(II) complexes (12) and (13) show isotropic type, indicating square planar and octahedral structure. Complexes Mn(II) (5) and Co(II) (6) show broad signals in the low field region indicating spin exchange interaction take place between metal(II) ion. Hg(II) complex (9), Tl(I) complex (11), Cr(III) complex (16), Cu(II) complex (17) and Cd(II) complex (21) showed potential antiproliferative activity where they showed inhibitory effect on breast carcinoma (MCF-7 cell line) in comparing with the standard drug.

Evaluation of quantitative probes for weaker Cu(i) binding sites completes a set of four capable of detecting Cu(i) affinities from nanomolar to attomolar

Copper plays essential roles in biology, but abnormal interactions are damaging. Reliable quantification of copper-protein interactions will underpin the molecular understanding of copper nutrition and toxicity. We have previously established two high affinity probes, Bathocuproine disulfonate (Bcs) and Bicinchoninate (Bca) anions, that are capable of in vitro quantification of Cu(i) binding with affinities from pico- to atto-molar concentrations. Quantitative probes are required for Cu(i) binding of lower affinity for proteins and peptides typically associated with neurodegenerative diseases. The present work evaluates two classic Fe(ii) ligands Ferene S (Fs) and Ferrozine (Fz) as quantitative probes for Cu(i). Both react with Cu(i) quantitatively to yield well-defined complex anions [Cu(I)(Fs)2](3-) (λmax = 484 nm, ε = 6700 cm(-1) M(-1)) and [Cu(I)(Fz)2](3-) (λmax = 470 nm, ε = 4320 cm(-1) M(-1)). These complexes are sensitive to aerial oxidation (E1/2∼ +0.36 V vs. SHE) and to substitution by other ligands (e.g., Cl(-), MeCN). However, they can be protected effectively under anaerobic conditions by suitable reductants and an excess of the free probe ligands. Formation constants β2 were determined by two approaches: direct metal ion titration and ligand competition. They provided estimates which differed by ∼3 orders of magnitude. The sources of these differences were examined carefully to consolidate the affinities of the two probes to a unified standard (10(15.1) M(-2) for Fz and 10(13.7) M(-2) for Fs). It is apparent that application of direct metal ion titrations to quantification of Cu(i) binding affinities is problematical and should be avoided. The four ligands Bcs, Bca, Fz and Fs in combination form a set of versatile probes for ligand competition experiments and are capable of detecting and differentiating an extended spectrum of Cu(i) binding affinities from nano- to atto-molar concentrations. Selected examples of quantification of weaker Cu(i) binding in proteins and peptides are provided, including that of an amyloid-β peptide.

Synthesis, spectral characterization and thermal studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with 2-amino benzoic acid- and 2-hydroxy benzoic acid thiophen-2-ylmethylene hydrazide

A series of metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) with 2-amino benzoic acid thiophen-2-ylmethylene hydrazide (Habth) and 2-hydroxy benzoic acid thiophen-2-ylmethylene hydrazide (Hhbth) have been synthesized. The complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, electronic, IR, NMR, ESR spectra and thermal studies (TGA and DTA). Molecular structure of the Habth ligand was determined by single crystal X-ray diffraction technique. Habth acts as a monobasic bidentate ligand in all its complexes bonding through a deprotonated CO− and CN groups whereas, Hhbth acts as a monobasic bidentate in its Co(II) and Ni(II) complexes, bonding through a deprotonated CO− and CN groups and as monobasic tridentate in Cu(II) and Zn(II) complexes bonding through CO, CN and deprotonated (CO)− groups with the metal ion. Electronic spectra suggest a square planar geometry for Co(II), Ni(II) and Cu(II) complexes of Habth and Co(II) and Ni(II) complexes of Hhbth. However, the Cu(II) and Zn(II) complexes of Hhbth have octahedral geometry. The ESR spectra of Cu(II) complex of Hhbth in the solid state and in DMSO frozen solution show axial signals and suggest the presence of unpaired electron in dx2-y2 orbital of Cu(II). The Cu(II) complex of Habth in solid state shows isotropic signal, whereas, axial signal in DMSO frozen solution in the range of tetragonally distorted octahedral geometry due to interactions of DMSO molecules at axial positions. Thermal studies of some of the metal complexes show a multi-step decomposition pattern of bonded ligands in the complex.

Observation of unusual optical transitions in thin-film Cu(In,Ga)Se_2 solar cells

In this paper, we examine photoluminescence spectra of Cu(In,Ga)Se(2) (CIGS) via temperature-dependent and power-dependent photoluminescence (PL). Donor-acceptor pair (DAP) transition, near-band-edge transition were identified by their activation energies. S-shaped displacement of peak position was observed and was attributed to carrier confinement caused by potential fluctuation. This coincides well with the obtained activation energy at low temperature. We also present a model for transition from V(Se) to V(In) and to V(Cu) which illustrates competing mechanisms between DAPs recombinations.

Spectral studies on Cu2+ ions in sodium–lead borophosphate glasses

Electron Paramagnetic Resonance (EPR) and optical absorption spectra of Cu 2+ ions in sodium–lead borophosphate glasses doped with different concentrations of Cu 2+ ions have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu 2+ ions. The values of spin-Hamiltonian parameters indicate that the Cu 2+ ions in sodium–lead borophosphate glasses are present in octahedral sites with tetragonal distortion. The optical absorption spectra of all the glass samples show a single broad band, which has been assigned to the 2 B 1g → 2 B 2g transition of Cu 2+ ions. The optical band gap energy ( E opt ) and Urbach energy (Δ E ) are calculated from their ultraviolet absorption edges. The emission bands observed in the ultraviolet and blue region are attributed to 3d 9 4s→3d 10 triplet transition in Cu + ion. The FT-IR spectra show that the glass system contains BO 3 , BO 4 and PO 4 structural units.

Simultaneous Resonance Raman Optical Activity Involving Two Electronic States

In the present work, the first observation of strong resonance Raman optical activity (RROA) involving more that one resonant electronic state is reported. The chiral transition metal complex bis-(trifluoroacetylcamphorato) copper(II), abbreviated Cu(tfc)(2), exhibits both resonance Raman (RR) and RROA spectra with laser excitation at 532 nm. Vibrational assignments for this complex were carried out by comparing the non-RR spectra of Cu(tfc)(2) excited at 1024 nm to density functional theory (DFT) calculations. The theory of the single-electronic-state (SES) RROA is extended to the next simplest level of theory involving two resonant electronic states (TES) without interstate vibronic coupling as an aide to the interpretation of the observed TES-RROA spectra. Based on measured UV-vis electronic absorbance spectra and corresponding TD-DFT calculations, the most likely two states associated with the RROA spectra are identified.

Theory ofL-edge resonant inelastic x-ray scattering for magnetic excitations in two-leg spin ladders

We study the magnetic excitation spectra of Cu ${L}_{2,3}$-edge resonant inelastic x-ray scattering (RIXS) from the spin-liquid ground state in two-leg spin ladder cuprates. By applying the projection method developed by the present authors, we have derived the formulas of the magnetic RIXS spectra, which are expressed by one- and two-spin correlation functions in the polarization changing and preserving channels, respectively. The one-spin correlation function includes both one- and two-triplon excitations and they are picked up separately by choosing rung wave vectors $\ensuremath{-}{q}_{a}=\ensuremath{\pi}$ and 0, respectively. An application to Sr${}_{14}$Cu${}_{24}$O${}_{41}$ reveals that the calculated RIXS spectrum captures well the dispersive behavior shown by the lower boundary of two-triplon continuum. An exception is absence of the intensity at zero-momentum transfer where weak but finite intensity was observed in the experiment. By adjusting the geometrical configuration of the measurement, one-triplon dispersion around the zone center could be detectable in the RIXS experiment. The observed weak intensity in the higher-energy region might be attributed to the two-spin correlation function, which could be detected more clearly at the ${M}_{3}$-edge RIXS spectra.

Flexibility of the coordination geometry around the cupric ions in Cu(II)-rat dipeptidyl peptidase III is important for the expression of enzyme activity

Dipeptidyl peptidase III (DPP III), the zinc peptidase, has a unique helix portion in the metal-binding motif (HELLGH). The enzyme activity of the cupric derivative of rat DPP III (Cu(II)-rat DPP III) for Lys-Ala-β-NA is about 30% of that of the wild-type enzyme. On the other hand, the enzyme activity of Cu(II)-rat del-DPP III, in which Leu453 is deleted from the metal-binding motif, possesses only 1–2% of the enzyme activity of rat del-DPP III. The EPR spectra of Cu(II)-rat DPP III in the presence of various concentrations of the substrate, Lys-Ala-β-NA, changed dramatically, showing formation of the enzyme–metal–substrate complex. The EPR spectra of Cu(II)-rat del-DPP III did not change in the presence of excess Lys-Ala-β-NA. The deletion of Leu453 from the HELLGH motif of rat DPP III leads to a complete loss of flexibility in the ligand geometry around the cupric ions. Under the formation of the enzyme–metal–substrate complex, Glu451 of Cu(II)-rat DPP III is sufficiently able to approach the water molecule via a very different orientation from that of the resting state; however, Glu451 of Cu(II)-rat del-DPP III is not able to access the water molecule.

The first detailed experimental investigation of the KMM + KMN Auger electron spectrum of Cu emitted in the EC decay of radioactive 65Zn in a solid state matrix

The KMM + KMN Auger spectrum of Cu emitted in the electron capture decay of radioactive 65Zn in a solid state matrix was investigated for the first time at the instrumental energy resolution of 14 eV. Energies and relative intensities of twelve resolved spectrum components were determined and compared with theoretical predictions. A reasonable agreement of the semi-empirical calculations of transition energies by Larkins with experiment was observed. A comparison of theoretical and the measured transition rates indicates the important role of a coupling scheme applied. A more detailed analysis was hampered by absence of theoretical intensities for the individual intermediate coupling spectrum components. A slight indication of the influence of the source backing material on the absolute energies was found for the L3M4, 5M4, 5 and L2M4, 5M4, 5 Auger lines.

Spectroscopic and magnetic properties of Cu(II) complexes with selected biologically important ligands

Abstract The aim of this work was to study the spectroscopic and magnetic properties of copper(II) o-, m-, p-aminobenzoates, o-, m-, p-methoxybenzoates and o-, m- and p-nitrobenzoates. The complexes were synthesized and their compositions were evaluated by elementary analysis. The infrared and Raman spectra for Cu(II) aminobenzoates, methoxybenzoates and nitrobenzoates were recorded and assigned. The obtained data were compared with those previously published for aminobenzoic, methoxybenzoic and nitrobenzoic acids and their sodium salts. The structures of Cu(II) o-, m-, p-aminobenzoates, o-, m-, p-methoxybenzoates and o-, m- and p-nitrobenzoates as well as the change in the electronic charges distribution caused by Cu(II) complex formation were discussed.

Elaborated studies for the ligitional behavior of thiouracil derivative towards Ni(II), Pd(II), Pt(IV), Cu(II) and [formula omitted] ions

A synthesis of new thiouracil derivative was carried out and deliberately investigated. A new series of complexes was prepared using Ni(II), Pd(II), Pt(IV), Cu(II) and UO2+2 ions. IR spectral data proposed the coordination mod of the ligand towards each metal ion and displays the binegative pentadentate mod as the maximum mod of coordination obtained with Ni(II) and Cu(II) complexes. 1HNMR spectrum of UO2+2 complex in comparing with the free ligand spectrum supports the binegative appearance of the coordinated ligand through the ionization of CO and CS groups. The electronic spectral data as well as the magnetic moment measurements are coincide with each others to propose the square–planar geometry with Ni(II), Pd(II) and Cu(II) complexes and octahedral geometry with the others. ESR spectrum of Cu(II) complex displays axially symmetric g tensor parameters with g11>g⊥>2.0023 indicating that the dx2-y2 orbital as a ground state with the square–planar geometry. The TG analysis for all isolated complexes were carried out to assert about the presence of water molecules physically or chemically attached with the central atom. The biological study was carried out against different microorganisms as gram negative, gram positive and fungi. The comparable data display the relative priority of Ni(II) complex in comparing with others against all organisms but, the other complexes display activity by the same with the free ligand.

Cu nanoparticles induced structural, optical and electrical modification in PVA

Cu nanoparticles were synthesized in PVA matrix by chemical reduction of cupric nitrate with hydrazine hydrate. Structural characterization of synthesized Cu–PVA nanocomposite was carried out using UV–Visible Spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Appearance of characteristic surface plasmon resonance peak of Cu nanoparticles at 591 nm in absorption spectra of Cu–PVA colloidal solution confirms the formation of Cu nanoparticles. TEM investigation indicates that Cu nanoparticles of size 16 nm are formed in PVA matrix which are in agreement with the size obtained using X-ray diffraction. Morphology of Cu–PVA nanocomposite was further confirmed using SEM. Analysis of UV–Visible absorption and reflection data indicates towards the reduction in optical band gap and increase in refractive index of the resulting nanocomposite. The synthesized Cu–PVA nanocomposite has been found to be more conducting than PVA as ascertained using I–V studies. The decrease in band gap and increase in conductivity can be correlated due to the formation of localized electronic states in PVA matrix due to insertion of Cu nanoparticles. Photoluminescence measurements showed strong blue visible emission peak at 450 nm at different excitation wavelengths in the range of 220–245 nm.

A study of the orientation dependence of the electron energy loss spectra for single crystal films of copper and silver

Apart from two peaks caused by bulk and surface plasmons, four or five peaks (depending on the crystal type) of electron energy losses due to inter- and intraband electron transitions are observed in the investigation of the electron energy loss spectra for metals (Cu, Ag). A comparative analysis of the spectra for Cu or Ag films reveals a shift of bulk plasmon loss peaks to higher values for polycrystals, as in the case of transition metals and semiconductors. In a study concerning the orientation dependence of the energy loss spectra (ELS) for electrons scattered from the copper and silver surface, the anisotropy of the bulk plasmon peak is found when the incident beam’s polar angle or the sample’s azimuthal angle are altered. The anisotropy of the primary electron energy loss for plasmon excitation is also observed, depending on the sample orientation relative to the direction incident electrons. The energy losses are found to increase with an increasing atomic packing density of planes and crystal transparency relative to the incident beam.

Solvent effects on the absorption and fluorescence spectra of Cu(II)-phthalocyanine and DFT calculations

The absorption and fluorescence spectra of Cu(II)-phthalocyanine were recorded in different solvents of varying types. The data fitted well to Lippert–Mataga equation thus confirming the dependence of orientation polarizability on the absorbance and emission values. The spectroscopic data also fitted well to the Kamlet–Abboud–Taft model. Density functional calculations were used to assign the absorption in the visible region to a π–π* transition between the HOMO-1 and LUMO of the complex. The visible region transition occurs between orbitals largely based on the phthalocyanine ligand, with no significant Cu character. The fluorescence emission of the molecule was effectively quenched in the presence of tetrachlorobenzoquinone (TCQ). The fluorescence quenching data shows that both static and dynamic quenching are operative in the present system. This may be due to the aggregation of the phthalocyanine complex in solution which arises from π–π stacking of its wide planar aromatic structure. The fluorescence quantum yields suggest that in the excited state the molecule interacts more with an aprotic solvent, while the ground state is preferentially stabilized in the presence of a protic solvent.

Effects of electron configuration and coordination number on the vibrational circular dichroism spectra of metal complexes of trans-1,2-diaminocyclohexane

Transition metal complexes of ethylenediamine have attracted significant interest as prototype systems for a range of studies related to their chiroptical properties. In order to better elucidate the effects of different central metal ions and also different coordination numbers on the vibrational circular dichroism (VCD) spectra, trans-1,2-diamino cyclohexane (chxn) was chosen as the chiral ligands in the current report. In this case the conformation of the diamino ligand is predetermined by its absolute configuration and the transition from the λ- to the δ-form that can occur in the case of ethylenediamine is no longer possible. The fingerprint region of the vibrational absorption and VCD spectra of three transition metal complexes of chxn have been analysed in detail. For the tris chelate complexes Ni(chxn)(3)(2+) and Cu(chxn)(3)(2+), selective enhancement of some VCD bands in the otherwise almost identical spectra has been observed and explained in terms of a ring current mechanism and of a different number of unpaired electrons of the metal centers. The comparison of the VCD spectra of Cu(chxn)(3)(2+) and Cu(chxn)(2)(2+) reveals the effects of coordination number that manifest as an inversion of the strong bisignate VCD pattern of the NH(2) scissor vibrational modes. This leads to the conclusion that this region can be used to extract information about the ligand environment and the chirality of the metal center.

Synthesis and Physicochemical Properties of Schiff Base Macrocyclic Ligands and Their Transition Metal Chelates

Tetraaza Schiff base macrocyclic ligands, <TEX>$L^1$</TEX>,<TEX>$L^2$</TEX> and their transition metal chelates have been synthesized and characterized by elemental analyses, IR, electronic, EPR and <TEX>$^1H$</TEX> NMR spectra, TGA and magnetic measurements. The molar conductance of one milli-molar solution of the complexes measured in DMF indicates that the divalent metal complexes are nonelectrolyte while those of trivalent metal ion, are 1:1 electrolytic in the same solvent. The reduction of Racah parameter from the free ion value confirms the presence of considerable covalence of metal ligand sigma bond in the Co(II) and Mn(II) complexes. The EPR spectra of Cu(II) complexes at room temperature shows axial symmetry indicating a <TEX>$d_x{^2}_{-y}{^2}$</TEX> ground state with significant covalent character. The thermal analysis suggests that the complexes do not contain water molecules because only the metal is left as residue.

EPR and optical studies of Cu 2+ doped ammonium dihydrogen phosphate single crystals

Electron paramagnetic resonance (EPR) spectra of Cu 2+ ion in ammonium dihydrogen phosphate are studied at liquid nitrogen temperature (77 K). Four magnetically inequivalent Cu 2+ sites in the lattice are identified. The angular variation spectra of the crystal in the three orthogonal planes indicate that the paramagnetic impurity, Cu 2+ enters the lattice substitutionally in place of NH 4 + ions. The spin Hamiltonian parameters are determined with the fitting of spectra to rhombic symmetry crystalline field. The ground state wave function of Cu 2+ ion is constructed and found to be predominantly | x 2– y 2〉. The cubic field parameter ( Dq) and tetragonal parameters ( Ds and Dt) are determined from optical spectra at room temperature. By correlating EPR and optical absorption spectra, the bonding coefficients are calculated and nature of bonding of metal ion with different ligands in the crystal is discussed.

Induced magnetic Cu moments and magnetic ordering in Cu2MnAl thin films on MgO(0 0 1) observed by XMCD

The disorder–order transition of a highly defective A2-ordered Cu2MnAl film on MgO(0 0 1) upon annealing at 600 K was monitored by means of x-ray absorption spectroscopy (XAS) at the Cu and Mn L2,3 edges. Additionally, x-ray magnetic circular dichroism (XMCD) was employed to determine element-specific orbital and spin resolved magnetic moments of the Cu and Mn atoms. A small induced total magnetic moment of ≈0.04 ± 0.01μB per atom was detected at the Cu sites, whereas a total magnetic moment of 3.57 ± 0.52μB is carried by the Mn atoms. The experimental XAS and XMCD spectra of Cu agree reasonably with the results from ab initio calculations, magnetic moments derived by the sum rules are in accordance with the calculations.

Cu 2- xS quantum dot-sensitized solar cells

In this study we report on the photovoltaic performance of Cu 2- x S ( x = 1, 0.03) quantum-dot (QD) sensitized liquid-junction solar cells. The QDs were grown with successive ionic layer adsorption and reaction. The CuS phase in the as-grown QDs was transformed into Cu 1.97S after annealing. The assembled Cu 1.97S cells yielded a best power conversion efficiency η of 0.90% under illumination of 100 mW/cm 2. The CuS cell had an η ~ 75% lower than that of Cu 1.97S. The external quantum efficiency (EQE) spectrum of Cu 1.97S covers the spectral range of 350–1100 nm with a maximal EQE of 63% at λ = 500 nm and an average EQE of 47% over the entire spectral range. This spectral range is also two times broader than that of N3 dye. The results show that Cu 2- x S QDs can be used as highly efficient broadband sensitizers for solar cells.

Reassessment of Copper and Titanium Valences and Excess Holes in Oxygen 2p Levels of CaCu3Ti4O12

The valences of Cu and Ti ions in CaCu3Ti4O12 (CCTO) are reassessed by characterizing the spectra of Cu(2p3/2), O(1s), and Ti(2p3/2) using X-ray photoelectron spectroscopy (XPS). The structure instability of CCTO leads to easy expulsion of oxygen from lattice during vacuum outgassing in XPS measurement, wherein the created oxygen vacancies reduce Cu2+ to Cu1+. We also present the evidence concerning the creation of the excess holes in the oxygen 2p levels resulting in a copper configuration in CCTO, due to the development of Cu vacancies and related to the reduction of Ti4+ to Ti3+.