Ground State Copper Research Articles

Ground-State Copper(III) Stabilized by N-Confused/N-Linked Corroles: Synthesis, Characterization, and Redox Reactivity.

Stable square planar organocopper(III) complexes (CuNCC2, CuNCC4, and CuBN) supported by carbacorrole-based tetradentate macrocyclic ligands with NNNC coordination cores were synthesized, and their structures were elucidated by spectroscopic means including X-ray crystallographic analysis. On the basis of their distinct planar structures, X-ray absorption/photoelectron spectroscopic features, and temperature-independent diamagnetic nature, these organocopper complexes can be preferably considered as novel organocopper(III) species. The remarkable stability of the high-valent Cu(III) states of the complexes stems from the closed-shell electronic structure derived from the peculiar NNNC coordination of the corrole-modified frameworks, which contrasts with the redox-noninnocent radical nature of regular corrole copper(II) complexes with an NNNN core. The proposed structure was supported by DFT (B3LYP) calculations. Furthermore, a π-laminated dimer architecture linked through the inner carbons was obtained from the one-electron oxidation of CuNCC4. We envisage that the precise manipulation of the molecular orbital energies and redox profiles of these organometallic corrole complexes could eventually lead to the isolation of yet unexplored high-valent metal species and the development of their organometallic reactions.

Dinuclear Metallacycles with Single M–X–M Bridges (X = Cl–, Br–; M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II)): Strong Antiferromagnetic Superexchange Interactions

A series of monochloride-bridged, dinuclear metallacycles of the general formula [M2(μ-Cl)(μ-L)2](ClO4)3 have been prepared using the third-generation, ditopic bis(pyrazolyl)methane ligands L = m-bis[bis(1-pyrazolyl)methyl]benzene (Lm), M = Cu(II), Zn(II), and L = m-bis[bis(3,5-dimethyl-1-pyrazolyl)methyl]benzene (Lm*), M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II). These complexes were synthesized from the direct reactions of M(ClO4)2·6H2O, MCl2, and the ligand, Lm or Lm*, in the appropriate stoichiometric amounts. Three analogous complexes of the formula [M2(μ-Cl)(μ-L)2](BF4)3, L = Lm, M = Cu(II), and L = Lm*, M = Co(II), Cu(II), were prepared from the reaction of [M2(μ-F)(μ-L)2](BF4)3 and (CH3)3SiCl. The bromide-bridged complex [Cu2(μ-Br)(μ-Lm*)2](ClO4)3 was prepared by the first method. Three acyclic complexes, [Co2(μ-Lm)μ-Cl4], [Co2(μ-Lm*)Cl4], and [Co2(μ-Lm*)Br4], were also prepared. The structures of all [M2(μ-X)(μ-L)2]3+ (X = Cl-, Br-) complexes have two ditopic bis(pyrazolyl)methane ligands bridging two metals in a metallacyclic arrangement. The fifth coordination site of the distorted trigonal bipyramidal metal centers is filled by a bridging halide ligand that has an unusual linear or nearly linear M-X-M angle. The NMR spectra of [Zn2(μ-Cl)(μ-Lm*)2](ClO4)3 and especially [Cd2(μ-Cl)(μ-Lm*)2](ClO4)3 demonstrate that the metallacycle structure is maintained in solution. Solid state magnetic susceptibility data for the copper(II) compounds show very strong antiferromagnetic exchange interactions, with -J values of 536 cm-1 for [Cu2(μ-Cl)(μ-Lm)2](ClO4)3·xCH3CN, 720 cm-1 for [Cu2(μ-Cl)(μ-Lm*)2](ClO4)3, and 945 cm-1 for [Cu2(μ-Br)(μ-Lm*)2](ClO4)3·2CH3CN. Smaller but still substantial antiferromagnetic interactions are observed with other first row transition metals, with -J values of 98 cm-1 for [Ni2(μ-Cl)(μ-Lm*)2](ClO4)3, 55 cm-1 for [Co2(μ-Cl)(μ-Lm*)2](ClO4)3, and 34 cm-1 for [Fe2(μ-Cl)(μ-Lm*)2](ClO4)3. EPR spectra of [Cu2(μ-Cl)(μ-Lm*)2](BF4)3 confirm the dz2 ground state of copper(II). In addition, the sign of the zero-field splitting parameter D was determined to be positive for [Cu2(μ-F)(μ-Lm*)2](BF4)3. Electronic spectra of the copper(II) complexes as well as Mössbauer spectra of the iron(II) complexes were also studied in relation with the EPR spectra and magnetic properties, respectively. Density functional theory calculations were performed using ORCA, and exchange integral values were obtained that parallel but are slightly higher than the experimental values by about 30%.

Comparison of molecular graphs of Lin, Nanand Cun(n= 2–5) clusters obtained from the density and the molecular electrostatic potential

AbstractThe analysis of the molecular graphs of the density and the molecular electrostatic potential (MEP) of small lithium, sodium and copper ground state cluster structures up to the pentamer is presented. For the underlying topological analysis all‐electron calculations were performed within the framework of Kohn–Sham density functional theory. The calculations are performed with the local level of theory in combination with all‐electron double zeta valence polarization basis sets. For this analysis, the ground state cluster structures obtained at the same level of theory were used. Molecular graphs of the density as well as the MEP are reported. The differences in the topology of the electronic density, MEP, and corresponding molecular graphs of the studied small lithium, sodium, and copper clusters are discussed. © 2012 Wiley Periodicals, Inc.

Magnetic dipole moments ofCu57,58,59

In-gas-cell laser spectroscopy of the isotopes $^{57,58,59,63,65}\mathrm{Cu}$ has been performed at the LISOL facility using the $244.164$-nm optical transition from the atomic ground state of copper. A detailed discussion on the hyperfine structure of $^{63}\mathrm{Cu}$ is presented. The magnetic dipole moments of the isotopes $^{57,58,59,65}\mathrm{Cu}$ are extracted based on that of $^{63}\mathrm{Cu}$. The new value $\ensuremath{\mu}=+0.479(13){\ensuremath{\mu}}_{N}$ is proposed for $^{58}\mathrm{Cu}$, consistent with that of a $\ensuremath{\pi}{p}_{3/2}\ensuremath{\bigotimes}\ensuremath{\nu}{p}_{3/2}$ ground-state configuration. Spin assignments for the radioactive isotopes $^{57,58,59}\mathrm{Cu}$ are confirmed. The isotope shifts between the different isotopes are also given and discussed.

Magnetic Dipole Moment ofCu57,59Measured by In-Gas-Cell Laser Spectroscopy

For the first time, in-gas-cell laser spectroscopy study of the (57,59,63,65)Cu isotopes has been performed using the 244.164 nm optical transition from the atomic ground state of copper. The nuclear magnetic dipole moments for (57,59,65)Cu relative to that of (63)Cu have been extracted. The new value for (57)Cu of mu((57)Cu) = +2.582(7)mu(N) is in strong disagreement with the previous literature value but in good agreement with recent theoretical and systematic predictions.

Kinetic analysis of the factors limiting the output power of the Ne–CuBr UV laser

The parametric optimization of the Ne–CuBr UV laser excited by longitudinal pulsed discharge is analysed by using a self-consistent kinetic model. Consistent characteristics of the optimization process are obtained by comparing with the experimental results. Simulation results show that neon ions come into being along with considerable depletion of the ground-state copper atoms. And the optimization of the discharge tube diameter is the tradeoff between the specific output photon density and the total active volume. Both the optimal neon gas pressure and the optimal reservoir temperature result from the balance between the neon ion density and the ground-state copper atom density to arrive at a maximum of their product.

Influence of the lifetime of the laser-excited level and the laser pulse duration on the saturated LIF signal during the prebreakdown phases of a pseudospark discharge

Ground state copper vapor number density, sputtered from the cathode of an experimental pseudospark switch is measured using laser-induced fluorescence (LIF) from the copper transition 4/sup 2/P/sub 3/2/-4/sup 2/D/sub 5/2/ at 510.55 nm. Measurements are made in the hollow cathode at several axial positions in the time interval between the trigger pulse and the voltage breakdown. At voltage 1 kV, this interval, referred to as a prebreakdown phase, has a random and variable shot to shot duration, but discharges for which this duration is the same reveal similar properties and can be arranged in groups. The presented results are for prebreakdown duration of 1 /spl mu/s. The metal vapor density is determined from the LIF signal by using both its maximum and integral. This approach follows from a widely used LIF model, which is examined in detail to reveal a less familiar feature, namely the possibility to obtain an estimate of the lifetime of the laser-excited level, which has been considered perturbed by collisions during the discharge. A comparison between this estimate and the lifetime, obtained by the exponential decay of the LIF signal, reveals good agreement.

MLCT state structure and dynamics of a copper(I) diimine complex characterized by pump-probe X-ray and laser spectroscopies and DFT calculations.

The molecular structure and dynamics of the photoexcited metal-to-ligand-charge-transfer (MLCT) state of [Cu(I)(dmp)(2)](+), where dmp is 2,9-dimethyl-1,10-phenanthroline, in acetonitrile have been investigated by time-domain pump-probe X-ray absorption spectroscopy, femtosecond optical transient spectroscopy, and density functional theory (DFT). The time resolution for the excited state structural determination was 100 ps, provided by single X-ray pulses from a third generation synchrotron source. The copper ion in the thermally equilibrated MLCT state has the same oxidation state as the corresponding copper(II) complex in the ground state and was found to be penta-coordinate with an average nearest neighbor Cu-N distance 0.04 A shorter than that of the ground state [Cu(I)(dmp)(2)](+). The results confirm the previously proposed "exciplex" structure of the MLCT state in Lewis basic solvents. The evolution from the photoexcited Franck-Condon MLCT state to the thermally equilibrated MLCT state was followed by femtosecond optical transient spectroscopy, revealing three time constants of 500-700 fs, 10-20 ps, and 1.6-1.7 ns, likely related to the kinetics for the formation of the triplet MLCT state, structural relaxation, and the MLCT excited-state decay to the ground state, respectively. DFT calculations are used to interpret the spectral shift on structural relaxation and to predict the geometries of the ground state, the tetracoordinate excited state, and the exciplex. The DFT calculations also indicate that the amount of charge transferred from copper to the dmp ligand upon photoexcitation is similar to the charge difference at the copper center between the ground-state copper(I) and copper(II) complexes.

Infrared spectra and density functional calculations of the copper thiocarbonyls: CuCS, Cu(CS)2, and Cu2CS in solid argon

Microwave discharge through CS2 vapor yielded CS which was cocondensed with laser-ablated copper atoms at 12 K in an argon matrix. Binary copper thiocarbonyl complexes: CuCS, Cu(CS)2, and Cu2CS were formed via the reactions of ground state copper atoms or dimers with CS in solid argon. On the basis of isotopic shifts and splittings as well as density functional calculations, absorptions at 1187.2, 1291.3, and 1353.9 cm−1 are assigned to the C–S stretching vibrations of the bent CuCS, linear Cu(CS)2, and end-on bonded Cu2CS molecules, respectively. The calculation results show that these copper thiocarbonyl complexes are more strongly bonded than the corresponding copper carbonyl complexes.

Positron and positronium interactions with Cu

The configuration-interaction (CI) method is used to investigate the interactions of positrons and positronium with copper at low energies. The calculations were performed within the framework of the fixed-core approximation with semiempirical polarization potentials used to model dynamical interactions between the active particles and the $(1s\ensuremath{-}3d)$ core. Initially, calculations upon the ${e}^{+}\mathrm{Li}$ system were used to refine the numerical procedures and highlighted the extreme difficulties of using an orthodox CI calculation to describe the ${e}^{+}$ Li system. The positron binding energy of ${e}^{+}\mathrm{Cu}$ derived from a CI calculation which included electron and positron orbitals with $\mathcal{l}<~18$ was 0.005 12 hartree while the spin-averaged annihilation rate was $0.507\ifmmode\times\else\texttimes\fi{}{10}^{9}{\mathrm{s}}^{\ensuremath{-}1}.$ The configuration basis used for the bound-state calculation was also used as a part of the trial wave function for a Kohn variational calculation of positron-copper scattering. The positron-copper system has a scattering length of about ${13.1a}_{0}$ and the annihilation parameter ${Z}_{\mathrm{eff}}$ at threshold was 72.9. The dipole polarizability of the neutral copper ground state was computed and found to be ${41.6a}_{0}^{3}.$ The structure of CuPs was also studied with the CI method and it was found to have a binding energy of 0.0143 hartree and an annihilation rate of $\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{9}{\mathrm{s}}^{\ensuremath{-}1}.$

Copper(II) complexes of 1,4,5,8,9,12-hexaazatriphenylene with oxalate, squarate, perchlorate as auxiliary ligands or counter ion

The crystal structures of [Cu(hat)(H2O)(ox)]·H2O (I), [Cu(hat)(H2O)3(sq)]·3H2O (II) and [Cu(hat)(H2O)2](ClO4)2·4H2O (III) have been determined from X-ray single crystal diffraction data (hat=1,4,5,8,9,12-hexaazatriphenylene, ox=oxalate, sq=squarate=dianion of 3,4-dihydroxy-cyclobut-3-ene-1,2-dione). Compound I crystallises in the triclinic system, space group P1̄ with a=6.6626(10), b=9.2001(14), c=12.9954(19)Å,α=103.301(15), β=91.414(21), γ=105.523(13)°, Z=2; compound II in the orthorhombic system, space group P212121 with a=6.9274(2), b=8.4327(3), c=34.0577(14)Å,Z=4; and compound III in the monoclinic system, space group C2/c with a=22.6652(10), b=9.2220(10), c=16.1400(10)Å,β=106.783(10)°, Z=8. In I chelating hat and oxalate ligands and a coordinated water molecule make up a square pyramidal coordination sphere. The mono-nuclear units so described are, however, connected into dinuclear entities through a weak axial interaction between copper and an oxalate oxygen of a neighbouring molecule. In II copper has a distorted, elongated octahedral coordination geometry, being surrounded by a chelating hat, a mono-dentate squarate and three water molecules. The copper atom in III is bound to two mono-chelating hat units and two water molecules, it is situated on a two-fold axis and features an inverted Jahn–Teller geometry with two short and four intermediate distances at room temperature. X-band ESR spectra of I and II at room temperature exhibit the pattern g∥>g⊥>2.0 corresponding to the dx2−y2 orbital ground state of copper(II) ion in elongated octahedral geometry in these complexes. In the case of complex III the room temperature spectrum exhibits the reverse pattern (g⊥>g∥>2.0); variable temperature X- and Q-band measurements reveal that the inverted spectrum is gradually converted to a normal axial spectrum as the temperature is lowered, signalling that the apparent compressed geometry at room temperature is caused by a 2D dynamic Jahn–Teller effect. Variable-temperature magnetic susceptibility measurements of I reveal the occurrence of a weak antiferromagnetic coupling (J=−1.0(1)cm−1 with the Hamiltonian defined as Ĥ=−JŜA·ŜB) between the copper ions.

Spectral, spatial and temporal characterization of a millisecond pulsed glow discharge: copper analyte emission and ionization

Two-dimensional maps of the spatial distributions of excited and ionized sputtered copper atoms are presented for a millisecond pulsed argon glow discharge. These maps demonstrate the temporal as well as spatial dependence of different excitation and ionization processes over the pulse cycle. Transitions from the low energy electronic states for the atom, characterized by emission such as that at 324.75 nm (3.82→0.00 eV), dominate the plateau time regime at a distance of 2.5 mm from the cathode surface. These processes originate from the electron excitation of ground state copper atoms. Transitions from high-energy electronic states, such as that characterized by emission at 368.74 nm (7.16→3.82 eV), predominate during the afterpeak time regime at a distance of 5.0–6.0 mm from the cathode surface. This observation is consistent with the relaxation of highly excited copper atoms produced by electron recombination with copper ions during the afterpeak time regime. Analyses of afterpeak and plateau intensities for a series of copper emission lines indicate an electron excitation temperature equivalent to 5.78 eV at 0.8 torr and 1.5 W. Temporal profiles exhibit copper ion emission only during the plateau time regime.

Absolute densities of long lived species in an ionized physical vapor deposition copper–argon plasma

Optical absorption spectroscopy has been used to measure absolute, average gas phase densities of neutral copper, ground and metastable states, and neutral argon, metastable and resonance states, in an ionized physical vapor deposition plasma. Spectroscopic measurements were carried with a xenon arc lamp as a high intensity, continuum light source, and an optical multichannel detector. Copper radiative transitions in the wavelength range of 324.8–510.6 nm and argon radiative transitions in the 706.7–811.5 nm range were employed. The curve of growth method has been used to calculate the absolute line average densities from fractional absorption data. For a copper–argon plasma of neutral pressure 30 and 10 mTorr copper metastable state densities were found to lie in the range of 1010–1012 cm−3. Comparison of these densities with neutral copper densities derived from independent measurements of neutral copper flux at the substrate indicate gas phase temperatures greater than 1500 K under certain experimental conditions. These values of inferred temperatures indicate the copper metastable state density to be significant in comparison with neutral copper ground state densities at 10 and 30 mTorr with radio frequency heating power of 1 kW. The concentrations of argon 4s sublevels of the first excited state were found to be in the range of 4.5×108–1.5×1011 cm−3 for the experimental conditions studied. The ordering of the relative densities of the argon 4s sublevels and the variation of the lumped first excited state with experimental parameters are discussed.

Intramolecular Energy Transfer in a Covalently Linked Copper(II) Porphyrin−Free Base Porphyrin Dimer: Novel Spin Polarization in the Energy Acceptor

The excitation wavelength dependence of time-resolved EPR is used to demonstrate the pathway of intramolecular energy transfer in a covalently linked copper(II)−free base porphyrin dimer. Spin polarized spectra are presented for selective excitation of both the copper(II) porphyrin donor (at 540 nm) and the free base porphyrin acceptor (at 640 nm) at 50 and 80 K. In all cases the observed spectra are assigned to the triplet state of the free base which is coupled weakly to the copper ground state doublet. The polarization pattern generated by selective excitation of the free base half is indicative of intersystem crossing (ISC), whereas excitation of the copper(II) half gives an eaa/eea polarization pattern. The latter is rationalized in terms of energy transfer via the lowest excited trip−quartet state of the copper(II) moiety, followed by selective depopulation from the spin states with doublet character in the weakly coupled free base triplet-copper doublet system. This leads to a spectrum which resemb...

Model calculations of electron scattering from copper

Electron scattering on the ground state of copper is considered using the convergent close-coupling (CCC) and coupled-channel optical (CCO) methods. In both cases the copper atom is treated by the inert d10 core model, with only the elastic ...3d104s 2S and ...3d104p2P channels considered. Comparison with experiment and other theories show best agreement of the experimental data with the CCC calculations, though some discrepancies are evident. We speculate on the source of the remaining discrepancies.

Afterglow ground-state copper density behavior in kinetically enhanced copper vapor lasers

The interferometric Hook method has been used to measure the copper ground-state density during the interpulse period for a 38 mm bore diameter copper vapor laser (CVL) operated in kinetically enhanced (KE) mode (Ne-HCl-H/sub 2/ gas mixture) and in conventional mode (pure neon and Ne-H/sub 2/ gas mixtures). It was found that the rate of regrowth of the axial copper density during the afterglow of the KE-CVL is 3-4 times faster, and the axial prepulse ground-state copper density is 2-3 times higher, than that observed for pure Ne or Ne-HI buffer gases. We conclude that the primary action of the HCl+H/sub 2/ additives is to increase the interpulse plasma relaxation rate and to increase the threshold copper density beyond which thermal runaway occurs. These effects are primarily responsible for the elevated pulse rates and increased pulse energies giving improved power scaling characteristics of KE-CVLs.

Modelling of the Parametric Behaviour of a Self-Heated Copper Vapour Laser : Issues Governing the Thermal Runaway Behaviour of the Plasma Tube Wall Temperature

A computer model has been used to simulate the discharge kinetics and parametric behaviour of a self-heated copper vapour laser for a wide range of optimum and non-optimum conditions. The results indicate that the ground state copper density and the peak electron temperature are the two most important parameters that affect laser performance. The results also confirm the existence of a threshold wall temperature (or threshold copper density) above which the plasma tube becomes thermally unstable with respect to the deposited electrical power, the wall temperature and the copper density, ultimately leading to thermal runaway. At low pulse repetition frequency (prf<8kHz), the thermal instability restricts the copper density (and laser output power) to values well below optimum.

Modelling of the kinetics and parametric behaviour of a copper vapour laser: Output power limitation issues

A self-consistent computer model was used to simulate the plasma kinetics (radially resolved) and parametric behaviour of an 18 mm bore (6 W) copper vapour laser for a wide range of optimum and non-optimum operating conditions. Good quantitative agreement was obtained between modelled results and experimental data including the temporal evolution of the 4p2P3/2, 4s2 D5/22 and 4s2D3/22 Cu laser level populations derived from hook method measurements. The modelled results show that the two most important parameters that affect laser behaviour are the ground state copper density and the peak electron temperature Te. For a given pulse repetition frequency (prf), maximum laser power is achieved by matching the copper atom density to the input pulse energy thereby maintaining the peak Te at around 3 eV. However, there is a threshold wall temperature (and copper density) above which the plasma tube becomes thermally unstable. At low prf (&amp;lt;8 kHz), this thermal instability limits the attainable copper density (and consequently the laser output power) to values below the optimum for matching to the input pulse energy. For higher prf values (&amp;gt;8 kHz), the copper density can be matched to the input pulse energy to give maximum laser power because the corresponding wall temperature then falls below the threshold temperature for thermal instability. For prf &amp;gt;14 kHz, the laser output becomes highly annular across the tube diameter due to a severe depletion of the copper atom density on axis caused by radial ion pumping.

The Interplay of Higher-Order Vibronic Coupling and Host-Lattice Strain in the 2Eg Ground State of Copper(II) — Elongated or Compressed Octahedra?*

The Interplay of Higher-Order Vibronic Coupling and Host-Lattice Strain in the ²E_g Ground State of Copper(II) — Elongated or Compressed Octahedra?*

The Interplay of Higher-Order Vibronic Coupling and Host-Lattice Strain in the2EgGround State of Copper(II) — Elongated or Compressed Octahedra?*

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