Crystal Structures of Double Vanadates LiCoVO4 and Li0.5Co1.25VO4

The crystal structures of vanadates Li_1-2xCo_1+xVO₄ with x = 0 and 0.25 have been studied by a full pattern analysis. It has been shown that in cubic spinel LiCoVO₄ (space group Fd3m), the 8a tetrahedral sites contain a majority of vanadium and a small amount of lithium; all cobalt, lithium, and a small amount of vanadium occupy the 16d octahedral sites. Li_0.5Co_1.25VO₄ crystals belong to the rhombic system (Imma space group) with unit cell parameters a = 5.939(1), b = 5.810(1), and c = 8.303(1). On substitution of lithium by cobalt according to the scheme 2Li⁺ Co²⁺ + , half of the lithium and 70% of the vacancies formed are in the 4a octahedral sites, and onethird of lithium and most of cobalt occupy the 4d octahedral sites. The 4e tetrahedral sites are completely occupied by vanadium and lithium in a ratio of 0.92/0.08. The interatomic distances in LiCoVO₄ and Li_0.5Co_1.25VO₄ are calculated, and the sizes of lithium ion transport channels are evaluated.     

Determination of activation energies in the annealing of cobalt recoil atoms in single and double complexes

Activation energies for the recombination of point defects generated by the /n,/ reaction in Ba (CoEDTA)₂·4H₂O, t-(Co(en)₂(NO₂)₂)Cl and (Co(en)₂(NO₂)₂) (CoEDTA)·1H₂O, have been evaluated using isothermal step annealing. The reselts were interpreted in terms of compound structures. It is possible to relate the recoil atom behaviour between single complexes and the double one.     

2,6-di-tert-butyl-4-perimidylphenols and their oxidation

1,8-Naphthylenediamine was reacted with 2,6-di-tert-butyl-4-formyl-phenol to produce 2,6-di-tert-butyl-4-(1,3-dihydro-perimidyl) phenol (I). The latter was coverted into 2,6-di-tert-butyl-4-(1H-perimidyl)phenol (II) by oxidizing I with sodium pyrosulfate. When phenol II was oxidized by lead dioxide in toluene and THF, the EPR spectra revealed a 12-component multiplet with perimidyl splitting constants a¹ _N=a³ _N=a_H ^NH=0.2 mT; a_H ^6.7=0.6 mT.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 1, pp. 64–67, January, 1992.     

Calcium-selective electrodes based on calcium tetra(4-chlorophenyl)borate complexes of macrocyclic polyether diamides

The preparation of macrocyclic 7,19-dibenzyl-7,19-diaza-1,4,10,13,16-pentaoxa-cycloheneicosane-6, 20-diones substituted in positions 2 and 3 with methyl groups, and their properties in PVC membranes as calcium sensors are described. Complexes of these polyether diamides (PEDA) with calcium and tetra(4-chlorophenyl)borate (TClPB) ions having the composition 2PEDA·Ca·2TClPB were prepared. Calcium electrodes based on these complexes have selectivity coefficients for calcium over barium up to 10³, and over alkali metals up to 3 × 10⁴.     

Specific Features of Glucoamylase Immobilization by Adsorption on Fibrous Polyelectrolytes

Some fundamental aspects of the immobilization of a hydrolytic enzyme glucoamylase via adsorption on aminocarboxylic ion-exchangers with fibrous structure were considered. The sorption capacity of amphoteric supports for the enzyme was studied in relation to the time of immobilization, concentration of hydrogen ions and the protein, and the ionic form of a polyelectrolyte. The catalytic properties of free and immobilized enzymes were compared.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 6, 2005, pp. 1003–1005.Original Russian Text Copyright © 2005 by Shkutina, Stoyanova, Selemenev.     

Synthesis,characterisation and ferric ion complexation studies of chelating probes for oxidative stress

The ferric ion binding characteristics of a novel chelating probe for detecting reactive oxygen and nitrogen species are reported. The probe comprises a polyaminocarboxylic acid chelator (EDTA) conjugated with aromatic amino acids. The probe (i) complexes redox-active and non-redox active metal ions and (ii) differentiates between different reactive oxygen/nitrogen species based upon the reaction products with same. The ferric ion binding characteristics were measured using species distribution and electronic absorption spectroscopic investigations. Over the physiological pH range a favoured one to one complex exists.     

Vibronic intensities in centrosymmetric lanthanide complex ions. I

Summary A theoretical model to calculate the vibronic intensities induced by the odd vibrational modes in centrosymmetric lanthanide complexes is developed and applied to octahedral complex ions, LnX ₆ ^3– , such as occur in the hexachloroelpasolites Cs₂NaLnCl₆. Both the crystal field and the ligand polarisation contributions are evaluated using a standard set of symmetry coordinates. For the crystal field term a truncated expansion of the intermediates states is employed rather than the more conventional closure approximation. Special care is necessary to ensure that the phases of the contributions are correctly determined since the cross-term between the ligand polarisation and crystal field contributions is signed. General equations applicable to anyf ⁿ complex ion are derived and an example of their application to the PrCl ₆ ^3– ion is given The agreement with experiment is satisfactory.     

Improvement of latex piezoelectric immunoassay: Detection of rheumatoid factor

Latex piezoelectric immunoassay is a method for detection of agglutination of antibody- or antigen-bearing latex by immunoreaction using a piezoelectric quartz crystal; the agglutination decreases the oscillation frequency of the crystal. This is advantageous in that coating the surface of the crystal followed by fixation of antibody or antigen is unnecessary. There is, however, a drawback, and to improve this, we designed a micro-cell in which only one side of the crystal is exposed to the solution. A method for regenerating the crystal was also devised. Measurement was carried out using a calibration curve of the frequency change against rheumatoid factor activity. The improvement made it possible to use one crystal repeatedly and reproducibility was satisfactory. The calibration curve became almost independent of the crystal used.     

Metal ion capillary zone electrophoresis with direct UV detection: determination of transition metals using an 8-hydroxyquinoline- 5-sulphonic acid chelating system

The application of capillary zone electrophoresis to the separation and determination of metal ions after the precolumn formation of negatively charged chelates is described. Multi-component mixtures of transition metal complexes with 8-hydroxyquinoline-5-sulphonic acid (HQS) were separated in about 10 min in a fused-silica capillary column with a borate buffer of pH 9.2 at an applied voltage of 15 kV followed by direct UV detection. The capillary pretreatment with an electroosmotic flow modifier, namely a tetraalkylammonium salt, is necessary to achieve resonable migration times of these metal complexes. Incorporating the chelating reagent in the electrophoretic buffer markedly improves the detectability of relatively unstable chelates, such as those of Co(II), Zn(II) and Cd(II), and allows the separation of metal ions that form unstable HQS chelates, such as Mn(II) and alkaline earth metals. The effects of electrophoretic buffer parameters affecting the complexation reaction and migration behaviour are discussed. Linearity of calibration graphs is observed for about three orders of magnitude with sub-ppm detection limits. The applicability of the method to the analysis of real samples is demonstrated.     

Crystal and molecular structure of 2e-diethylamino-3e,4e-dimethyl-5e-phenyl-2a-thio-1,3,2-oxazaphospholane

The results of an x-ray structural investigation of 2e-diethylamino-3e,4e-dimethyl-5e-phenyl-2a-thio-1,3,2-oxazaphospholane are discussed. It has been shown that the conformation of the 5-membered ring is that of a half-chair.Institute of Organic Synthesis and Coal Chemistry, Kazkh SSR Academy of Sciences, Karganda. A. N. Nesmeyanov Institute of Heteroorganic Compounds, USSR Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 386–389, May–June, 1990.