New beta cis folded organocobalt derivatives with a salen-type ligand

The reduction of [Co(III)(tmsalen)py(2)](+)ClO(4)(-), where tmsalen = 4,4',7,7'-tetramethylsalen, with NaBH(4)/PdCl(2) in alkaline methanolic solution, followed by the oxidative addition of CH(2)ClI, leads to the expected trans organometallic dimeric species 1, [CH(2)ClCo(tmsalen)](2), provided that the product is recovered from the reaction mixture immediately after the completion of the reaction. If 1 is left for longer time in contact with the reaction mixture, the intramolecular reaction of the axial chloromethyl group with the equatorial chelate leads to the formation of the monocationic complex 2, containing a seven-membered ring. In this complex the novel tetradentate ligand coordinates Co in a cis fashion, the other two positions being occupied by one py and one water molecule. The resulting complex is chiral, even if the reaction product is a racemic compound. The unidentate ligands of 2 have been exchanged quantitatively for N-MeIm, and the resulting complex 3 still maintains the beta cis geometry. Therefore, 2 may be considered the precursor of a new class of organocobalt derivatives with a folded tetradentate ligand and two adjacent exchangeable sites. On the basis of the geometry of the tetradentate Schiff bases in complexes, where they adopt a planar geometry, it was suggested that there is a significant electron density delocalization involving the metal center over the two chemically equivalent moieties of Co(chel). Comparison of the geometry of the planar salicylaldiminate (sal) moiety with that of the cyclized methoxy-iminate one (imi) in 2 and 3 strongly supports that the delocalization, still present in sal, is essentially either lost or strongly reduced in imi.     

Comparison of chemical composition and free radical scavenging ability of glycosidically bound and free volatiles from Bosnian pine (Pinus heldreichii Christ. var. leucodermis)

The results obtained show that Bosnian pine is rich in glycosidically bound volatile compounds with strong free radical scavenging properties. Since volatiles can be released from nonvolatile glycoside precursors, these compounds can be considered as a hidden potential source of antioxidant substances and may contribute to the total free radical scavenging ability of Bosnian pine.     

The Cuts Selection Method Based on Histogram Segmentation and Impact on Discretization Algorithms

The preprocessing of data is an important task in rough set theory as well as in Entropy. The discretization of data as part of the preprocessing of data is a very influential process. Is there a connection between the segmentation of the data histogram and data discretization? The authors propose a novel data segmentation technique based on a histogram with regard to the quality of a data discretization. The significance of a cut’s position has been researched on several groups of histograms. A data set reduct was observed with respect to the histogram type. Connections between the data histograms and cuts, reduct and the classification rules have been researched. The result is that the reduct attributes have a more irregular histogram than attributes out of the reduct. The following discretization algorithms were used: the entropy algorithm and the Maximal Discernibility algorithm developed in rough set theory. This article presents the Cuts Selection Method based on histogram segmentation, reduct of data and MD algorithm of discretization. An application on the selected database shows that the benefits of a selection of cuts relies on histogram segmentation. The results of the classification were compared with the results of the Naïve Bayes algorithm.     

Determination of Cr(III) and Cr(VI) in industrial and environmental liquid samples by EDXRF method

A rapid, sensitive and selective procedure for determination of Cr(III) and Cr(VI) in environmental and industrial liquid samples via preconcentration with ammonium pyrrolidine dithiocarbamate (APDC) and determination by means of the EDXRF was described. The effect of pH in the range of 3-11 on the recovery of Cr(III) and Cr(VI) has been investigated separately and in combination of these two species. The influence of organic matter, carbonate species and elements V, Mn and Fe on the recovery of each chromium specie (separately/in combination) over whole pH range was also tested in order to simulate condition occurring in natural waters that usually contain certain amount of dissolved organic matter and carbonate ions. Cr(VI) and Cr(III) have shown different behaviors in reaction with APDC at different pH ranges and therefore it is possible to separate those two species. It was found that Cr(VI) creates complex with APDC only in the pH range from 3 to 5 with quantitative recovery (app. 98%) at pH 3, but there was no recovery of Cr(III) at that pH. On the contrary, in pH range from 6 to 11, reaction with Cr(III) and APDC reviled that the only reaction product is Cr(OH)₃ instead of the expected Cr(III)-APDC complex. All reaction products were characterized by IR spectroscopy.     

Determination of lanthanides by source excited energy dispersive X-ray fluorescence (EDXRF) method after preconcentration with ammonium pyrrolidine dithiocarbamate (APDC)

A new analytical procedure for determination of lanthanides in environmental samples after chemical separation from major matrix elements on DOWEX 50W-X8 resin followed by preconcentration with chelating agent ammonium pyrrolidine dithiocarbamate (APDC) and analyses of thin targets by energy dispersive X-ray fluorescence (EDXRF) method using ¹⁰⁹Cd as the source of excitation was presented. Characteristic L X-ray lines of the lanthanides were used for calculations of the net peak area and mass concentrations. The influence of pH value of the solution and addition of organic matter on the complexation was investigated. Percentage of recovery of each lanthanide after separation on DOWEX 50W-X8 resin was also determined. Accuracy of the method was tested on standard reference materials and real environmental samples (red mud material). For that purpose samples of standard reference materials and red mud were prepared as thick targets and directly analyzed (without the separation step) by EDXRF method using ²⁴¹Am as the excitation source. In that case lanthanides concentrations were determined over their characteristic K X-ray lines and results were compared with those obtained after separation/preconcentration step described above. Results showed that selected lanthanides made stable complexes with APDC in the alkaline medium with the maximum recovery at pH = 8. The presence of organic matter slightly modified the complexation by means of somewhat higher recovery percentage at pH lower than 7 and approx. 20% lower recovery at pH higher than 7.

Recovery of the elements after separation on DOWEX 50W-X8 resin and preconcentration with APDC at pH = 8 varied from 91.4% (Pr) to only 24.9% in the case of Dy.

Concentrations of lanthanides measured in standard reference material and environmental samples of red mud after microwave digestion, separation on DOWEX 50W-X8 resin, preconcentration with APDC at pH = 8 and recalculation on the percentage of recovery were in good agreement with certified values in the case of SRM as well as with the concentrations obtained by direct determination over K lines using ²⁴¹Am excitation source in the case of red mud leading to the conclusion that presented method was applicable for the determination of lanthanides in real environmental samples.