From Gas Phase Observations to Solid State Reality: The Identification and Isolation of Trinuclear Salicylaldoximato Copper Complexes

Conditions have been identified in which phenolic aldoximes and ketoximes of the types used in commercial solvent extraction processes can be doubly deprotonated and generate polynuclear Cu complexes with lower extractant:Cu molar ratios than those found in commercial operations. Electrospray mass spectrometry has provided an insight into the solution speciation in extraction experiments and has identified conditions to allow isolation and characterization of polynuclear Cu-complexes. Elevation of pH is effective in enhancing the formation of trinuclear complexes containing planar {Cu₃-μ₃-O}⁴⁺ or {Cu₃-μ₃-OH}⁵⁺ units. DFT calculations suggest that such trinuclear complexes are more stable than other polynuclear species. Solid structures of complexes formed by a salicylaldoxime with a piperidino substituent ortho to the phenolic OH group (L⁹H₂) contain two trinuclear units in a supramolecular assembly, {[Cu₃OH(L⁹H)₃(ClO₄)](ClO₄)} ₂, formed by H-bonding between the central {Cu₃-μ₃-OH}⁵⁺ units and oxygen atoms in the ligands of an adjacent complex. Whilst the lower ligand:Cu molar ratios provide more efficient Cu-loading in solvent extraction processes, the requirement to raise the pH of the aqueous phase to achieve this will make it impractical in most commercial operations because extraction will be accompanied by the precipitation (as oxyhydroxides) of Fe(III) which is present in significant quantities in feed solutions generated by acid leaching of most Cu ores.

Energy-resolved mass spectrometry to investigate nucleobase triplexes – a study applied to triplex-forming artificial nucleobases

This paper discloses the use of an energy-resolved mass spectrometric-based approach to assess the stabilities of base triplexes encompassing artificial nucleobases by using variable energy collision-induced dissociation.

Electrochemical and DFT studies of brass corrosion inhibition in 3% NaCl in the presence of environmentally friendly compounds

The effects of adenine, salicylaldoxime and 4(5)-methylimidazole on brass corrosion in NaCl were investigated. The investigation comprised electrochemical techniques, scanning electron microscopy and quantum chemical calculation. The results obtained by polarization measurements show that the examined compounds successfully inhibited the corrosion of brass. Additionally, the quantum mechanical calculations indicate that there is a correlation between energy gap and inhibition efficiency. Moreover, the inhibition mechanism includes the adsorption of the inhibitor on active sites on the electrode surface, which was confirmed by SEM-EDS analysis of the brass.

Tuning receptors for the encapsulation of beryllium2+

A method for evaluating second sphere H-bonding interactions as a means to tune specific characteristics in coordinating ligands has been used to evaluate the binding strength of a series of beryllium complexes.

Reduction from copper(II) to copper(I) upon collisional activation of (pyridine)(2) CuCl(+)

Electrospray ionization of dilute aqueous solutions of copper(II) chloride-containing traces of pyridine (py) as well as ammonia permits the generation of the gaseous ions (py)(2) Cu(+) and (py)(2) CuCl(+) , of which the latter is a formal copper(II) compound, whereas the former contains copper(I). Collision-induced dissociation of the mass-selected ions in an ion-trap mass spectrometer (IT-MS) leads to a loss of pyridine from (py)(2) Cu(+) , whereas an expulsion of atomic chlorine largely prevails for (py)(2) CuCl(+) . Theoretical studies using density functional theory predict a bond dissociation energy (BDE) of BDE[(py)(2) Cu(+) -Cl] = 125 kJ mol(-1) , whereas the pyridine ligand is bound significantly stronger, i.e. BDE[(py)CuCl(+) -py] = 194 kJ mol(-1) and BDE[(py)Cu(+) -py] = 242 kJ mol(-1) . The results are discussed with regard to the influence of the solvation on the stability of the Cu(I) /Cu(II) redox couple.