Liquid chromatography of platinum metals and prospects of development

Summary A survey of the authors' work on liquid chromatography of platinum metals in the form of chelates with 1-(2-pyridylazo)-2-naphthol (PAN) is given. Extraction chromatography with PAN in isopentanol as a stationary phase was used to achieve a group concentration of these metals (Pd, Pt and Rh, concentration coefficient 100) from large volumes of aqueous solutions and a selective extraction of palladium from solutions containing other platinum, nonferrous and heavy metals on a 85–98° C thermostatted chromatographic column. The prospects for the use of liquid chromatography in the analysis of platinum metals are discussed.

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Flüssig-Chromatographie von Platinmetallen und zukünftige Entwicklungen

     

Reactivity of 3d transition metal cations in diethylene glycol solutions. Synthesis of transition metal ferrites with the structure of discrete nanoparticles complexed with long-chain carboxylate anions

Study of the reactivity of 3d transition metal cations in diethylene glycol solutions revealed several key features that made it possible to develop a new method for synthesis of the nanocrystalline transition metal ferrites. The 3-7 nm particles of [MFe2O4]n[O2CR]m, where M = Mn, Fe, Co, Ni, and Zn, ligated on their surface with long-chain carboxylate anions, have been obtained in an isolated yield of 75-90%. The key features are the following. Complexation of the first-row transition metal cations with diethylene glycol at a presence of alkaline hydroxide is sufficient to enable control over the rate of their hydrolysis. The reaction of hydrolysis leads to the formation of metal oxide nanocrystals in colloidal solution. The nanoparticles growth is terminated by an added long-chain carboxylic acid, which binds to their surface and acts as a capping ligand. The isolated nanocrystalline powders are stable against agglomeration and highly soluble in nonpolar organic solvents.     

Electrospray mass and tandem mass spectrometry of homologous and isomeric singly, doubly, triply and quadruply charged cationic ruthenated meso-(phenyl)m-(meta- and para-pyridyl)n (m + n = 4) macrocyclic porphyrin complexes

Ten homologous or isomeric singly, doubly, triply and quadruply charged cationic macrocyclic complexes I-Va, bn+ (n = 1-4) formed by the coordination of [Ru(bipy)2Cl]+ to the pyridyl N-atoms of a series of meso-(phenyl)m-(meta or para-pyridyl)n-porphyrins (m + n = 4) were transferred to the gas phase and structurally characterized by electrospray ionization (ESI) mass (MS) and tandem mass (MS/MS) spectrometry. Previously known to be stable in solution and in the solid state, I-Va, bn+ are found to constitute also a new class of stable, long-lived multiply charged gas-phase ions with spatially separated charge sites. Increasing intramolecular electrostatic repulsion from Ia, b+ to IVa, b3+ facilitates in-source and tandem collision-induced dissociation (CID). However, for the quadruply charged ions Va, b4+, electrostatic repulsion is alleviated mainly by ion pairing with the CF3SO3- counterion forming the salt clusters [Va,b/CF3SO3]3+ and [Va,b/(CF3SO3)2]2+ with reduced charge states. Ion-pairing that yields [IVa,b/CF3SO3]2+ is also observed as a minor ESI process for the triply charged ions IVa, b3+. The gaseous ions I-Va, bn+ (n = 2, 3 or 4) dissociate by sequential 'charge partitioning' with the formation of two cationic fragments by the release of [Ru(bipy)2Cl]+. The meta (a) and para (b) isomers and the positional isomers II2+ and III2+ display nearly identical ESI-MS and ESI-MS/MS spectra. ESI-MS/MS of I-Va, bn+ shows that the Ru-py(P) is, intrinsically, the weakest bond since this bond breaks preferentially upon CID.     

Ion-induced CO adsorption on polycrystalline nickel. Secondary ion mass spectrometry study

In the process of ion-induced CO adsorption (Ar⁺, 4 keV, 4 A/cm²) on polycrystalline Ni at room temperature and P=(1–40)×10^–6 Pa the emission of Ni⁺, NiCO⁺, CO⁺, NiO⁺ and C⁺ ions is observed. The emission of the last three ions is due to the ion-stimulated dissociation of weakly bound CO state and NiO formation. The weakly bound state is formed owing to surface defects produced by ion bombardment. The cross sections of the ion-induced desorption are 1.8 and 0.8×10^–14 cm², respectively, for weakly bound and strongly bound states.     

Unusual heme-histidine bond in the active site of a chaperone

The heme chaperone CcmE is essential for the delivery of heme to c-type cytochromes. It forms an unusual transient, yet covalent, bond between an essential histidine, H130, and heme. We report on the discovery of the chemical structure of this bond solved by NMR, where the heme vinyl is cross-linked at the beta carbon to the Ndelta1 of H130. As this type of heme linkage has not been described previously in any cytochrome or hemoprotein, it represents a novel type of heme-histidine complex.     

Total synthesis of (±)-cyclooroidin

The first total synthesis of (±)-cyclooroidin, a member of the pyrrole-imidazole alkaloid family recently isolated from the sponge Agelas oroides in optically pure form, is described. The synthesis was achieved in nine linear steps, with an overall yield of 10%. Key step was a Wolff bromoketone synthesis performed on the intermediate longamide B.     

Proton Relaxometry of Long-Lived Spin Order

A study of long-lived spin order in chlorothiophene carboxylates at both high and low magnetic fields is presented. Careful sample preparation (removal of dissolved oxygen in solution, chelating of paramagnetic impurities, reduction of convection) allows one to obtain very long-lived singlet order of the two coupled protons in chlorothiophene derivatives, having lifetimes of about 130 s in D₂O and 240 s in deuterated methanol, which are much longer than the T₁-relaxation times (18 and 30 s, respectively, at a field =9.4 T). In protonated solvents the relaxation times become shorter, but the lifetime is still substantially longer than . In addition, long-lived coherences are shown to have lifetimes as long as 30 s. Thiophene derivatives can be used as molecular tags to study slow transport, slow dynamics and slow chemical processes, as has been shown in recent years.     

Asymptotics of many-electron wavefunctions and calculation of tunnel transitions

A new method for defining the wavefunction asymptotics for many-electron systems in the far-subbarrier region is suggested. The method is based on the Lippman-Schwinger formalism and can provide an accuracy in defining the asymptotics similar to that in the main region of the electron localization (MREL). The wavefunctions in MREL are the basis for obtaining the asymptotics. Molecular, cluster and surface systems are considered. A new approach to the calculation of tunneling transitions is formulated. A general expression for the tunneling current in scanning tunneling microscopy (STM) is obtained which strictly takes into account the penetration factor, the correlation between the tunneling current from individual atoms, and the angular dependence of asymptotics of basic atomic functions. This permits us to state and correctly solve the problem of defining the electron wavefunctions of the surface using the data of the tunneling current measurement at various biases and the positions of the tip.