Solvation Of Copper Ions Research Articles

Coordination and solvation of copper ion: infrared photodissociation spectroscopy of Cu+(NH3)n (n = 3–8)

Coordination and solvation structures of the Cu(+)(NH(3))(n) ions with n = 3-8 are studied by infrared photodissociation spectroscopy in the NH-stretch region with the aid of density functional theory calculations. Hydrogen bonding between NH(3) molecules is absent for n = 3, indicating that all NH(3) molecules are bonded directly to Cu(+) in a tri-coordinated form. The first sign of hydrogen bonding is detected at n = 4 through frequency reduction and intensity enhancement of the infrared transitions, implying that at least one NH(3) molecule is placed in the second solvation shell. The spectra of n = 4 and 5 suggest the coexistence of multiple isomers, which have different coordination numbers (2, 3, and 4) or different types of hydrogen-bonding configurations. With increasing n, however, the di-coordinated isomer is of growing importance until becoming predominant at n = 8. These results signify a strong tendency of Cu(+) to adopt the twofold linear coordination, as in the case of Cu(+)(H(2)O)(n).

Electrochemical determination of standard thermodynamic parameters characterizing resolvation of Cu2+ cations in water-acetone mixtures

Standard thermodynamic parameters characterizing the resolvation of the Cu2+ ions and the surface potential at the gas-phase/acetone interface, ΔχMe2CO, are determined on the basis of the results of measuring compensating voltages of the Volta circuits by the Kenrick method at 298.15 K and the value of the surface potential at the nonaqueous-solvent/gas phase interface, ΔχH2OS, which was obtained earlier. A comparison of thermodynamic parameters characterizing the resolvation of the copper ions with similar quantities for the calcium and cadmium ions is performed. Specific features pertaining to the solvation of copper ions in a mixed water-acetone solvent are elucidated and the effect of the composition and nature of the mixed solvent on the quantities obtained is determined. A dependence of variations in the thermodynamic parameters characterizing the resolvation of cations on their charge and crystallographic radius is established. The dependence corresponds to the series K+, Ca2+, Cd2+, Cu2+.

Solvation of copper ions by imidazole: Structures and sequential binding energies of Cu+(imidazole)x, x = 1–4. Competition between ion solvation and hydrogen bonding

The sequential bond dissociation energies of Cu+(imidazole)x, where x = 1-4 are determined by analysis of the kinetic energy dependence of the collision-induced dissociation with Xe in a guided ion beam tandem mass spectrometer. In all cases, the primary and lowest energy dissociation channel observed is the endothermic loss of an intact imidazole molecule. The primary cross section thresholds are interpreted to yield 0 K and 298 K bond dissociation energies after accounting for the effects of multiple ion-neutral collisions, kinetic and internal energy distributions of the reactants, and dissociation lifetimes. To obtain model structures, vibrational frequencies, rotational constants and energetics for the Cu+(imidazole)x complexes and their dissociation products, density functional theory calculations at the B3LYP/6-31G* level are performed. Theoretical bond dissociation energies are determined from single point energy calculations at the B3LYP/6-311+G(2d,2p) level of theory using the B3LYP/6-31G* optimized geometries. Excellent agreement between theory and experiment is observed for the Cu+(imidazole)x complexes, where x = 1, 2 and 4. In contrast, theory systematically underestimates the strength of the binding in the Cu+(imidazole)3 complex. The ground state structures of the Cu+(imidazole), complexes and the trends in the sequential bond dissociation energies are explained in terms of stabilization gained from sd hybridization and hydrogen bonding interactions and destabilization arising from ligand-ligand repulsion. The trends in the binding of these complexes are also examined to provide insight into the structural and functional roles that histidine and other ligands play in the behavior of metalloproteins and metalloenzymes.

Solvation of copper ions by acetone. Structures and sequential binding energies of Cu +(acetone) x, x = 1–4 from collision-induced dissociation and theoretical studies

Collision-induced dissociation of Cu +(acetone) x , x = 1–4, with Xe is studied as a function of kinetic energy using guided ion beam mass spectrometry. In all cases, the primary and lowest energy dissociation channel observed is endothermic loss of one acetone molecule. The primary cross section thresholds are interpreted to yield 0 and 298 K bond energies after accounting for the effects of multiple ion-neutral collisions, internal energy of the complexes, and dissociation lifetimes. Density functional calculations at the B3LYP/6-31G* level of theory are used to determine the structures of these complexes and provide molecular constants necessary for the thermodynamic analysis of the experimental data. Theoretical bond dissociation energies are determined from single point calculations at the B3LYP/6-311+G(2d,2p) and MP2(full)/6-311+G(2d,2p) levels, using the B3LYP/6-31G* optimized geometries. The experimental bond energies determined here are in good agreement with previous experimental measurements made in a high-pressure mass spectrometer for the sum of the first and second bond energy (i.e., Cu +(acetone) 2 → Cu + + 2 acetone) when these results are properly anchored. The agreement between theory and experiment is reasonable in all cases, but varies both with the size of the cluster and the level of theory employed. B3LYP does an excellent job for the x = 1 and 3 clusters, but is systematically low for the x = 2 and 4 clusters such that the overall trends in sequential binding energies are not parallel. In contrast, all MP2 values are somewhat low, but the overall trends parallel the measured values for all clusters. The trends in the measured Cu +(acetone) x binding energies are explained in terms of 4s-3d σ hybridization effects and ligand-ligand repulsion in the clusters.

Solvation of Copper Ions by Acetonitrile. Structures and Sequential Binding Energies of Cu+(CH3CN)x, x = 1−5, from Collision-Induced Dissociation and Theoretical Studies

Collision-induced dissociation of Cu+(CH3CN)x, x = 1−5, with xenon is studied as a function of kinetic energy using guided ion beam mass spectrometry. In all cases, the primary and lowest energy dissociation channel observed is endothermic loss of one acetonitrile molecule. The cross section thresholds are interpreted to yield 0 and 298 K bond energies after accounting for the effects of multiple ion-molecule collisions, internal energy of the complexes, and dissociation lifetimes. Density functional calculations at the B3LYP/6-31G* level of theory are used to determine the structures of these complexes and provide molecular constants necessary for the thermodynamic analysis of the experimental data. Theoretical bond dissociation energies are determined from single point calculations at the B3LYP/6-311+G(2d,2p) level and also with an extended basis on Cu+ of 6-311+G(3df) using the B3LYP/6-31G* optimized geometries. The experimental bond energies determined here are in excellent agreement with previous experimental measurements made in a high-pressure mass spectrometer for the sum of the first and second bond energy (i.e., Cu+(CH3CN)2 → Cu+ + 2CH3CN) when these results are properly anchored. Excellent agreement between theory and experiment is also found for the Cu+(CH3CN)x, x = 1 and 2 clusters. Theory systematically underestimates the binding energy in the larger clusters such that higher levels of theory are necessary to adequately describe the very weak noncovalent interactions in these systems.