Stability Of Cu Complexes Research Articles

THE EFFECT OF ORGANIC FERTILIZERS ON THE CONTENT OF TRACE ELEMENTS IN THE GREEN MASS OF CORN

The optimal content of trace elements in green feeds is of fundamental importance for ensuring high productivity of cattle. For the production of green fodder, corn grown in fields located near livestock complexes and fertilized by by-products of animal husbandry (BPA) is used. In conditions of a high load of BPA (manure, manure runoff), the accumulation of trace elements in the green mass of corn (GMC) occurs more intensively than when using fertilizers in mineral form. Corn cultivation promotes active removal of Fe, Zn, Mn from the soil and weak removal of Cu. The accumulation of trace elements in plants grown on acidic soils fertilized by BPA is higher than when grown on neutral soils. According to the absolute content in GMC, trace elements are arranged in the following sequence: Mn>Fe>Zn>Cu. The corresponding series coincides with the sequence of decreasing concentrations of mobile forms of elements in agro-ecosystems, but differs from the sequence of changes in the indices of accumulation (IA) of trace elements. The IA values calculated on the basis of experimental data are arranged as follows: Fe>Zn>Mn>Cu. The IA of all trace elements, except Cu, in the GMC was higher than one, so corn can be classified as battery plants. IA Cu in different agro-ecosystems was below 1 and practically did not depend on the level of metabolic acidity. The weak accumulation is probably due to the low Cu content in sod-podzolic soils, the high stability of Cu complexes with organic ligands and the significant content of nitrogen available to plants in soils fertilized by BPA.

Electrochemical study of the effect of Al3+ on the stability and performance of Cu-based ATRP catalysts in organic media

Electrochemically-mediated atom transfer radical polymerization (eATRP) has attracted a great deal of attention as one of the most powerful methods of synthesis of polymers with well-defined architecture and low dispersity. The process is more cost-effective and simpler if performed in undivided cells with cheap sacrificial anodes such as aluminum. In this connection, knowledge of the effect of Al3+ ions released from the anode on the stability and performance of typical Cu catalysts is highly desired. In this study, the stability of Cu complexes with tris(2-(dimethylamino)ethyl)amine (Me6TREN) and tris(2-pyridylmethyl)amine (TPMA), was investigated in DMF, DMSO, and MeCN by cyclic voltammetry, UV-vis-NIR spectroscopy and controlled-potential eATRP. Both ligands form complexes with Al3+, but in DMF and DMSO, TPMA binds more strongly to Cu2+ and Cu+ than Al3+, whereas the opposite is true for Me6TREN in all tested solvents. Therefore, eATRP of n-butyl acrylate catalyzed by [CuITPMA]+ in DMF or DMSO was not affected by Al3+ ions. In contrast, when Me6TREN was used, the reactions could not proceed to high conversions because Al3+ ions displace Cu2+ from the ligand. To suppress the effect of Al3+, use of excess ligand and/or Br− with respect to CuII proved to be efficient.

Relationships between stability of Cu complexes and nitrification inhibition effects of corresponding ligands in soils

In order to investigate the relationships between the stability of Cu complexes and the nitrification inhibition effects of corresponding ligands, the effects of 22 kinds of Cu (II) ligands and eight kinds of Cu (I) ligands were evaluated in three types of soil on nitrification potentials (NPs) under short-term incubation (5 h) and nitrification inhibitory rates (NIRs) under long-term incubation (14 d). The results showed that the inhibitory effect of Cu (II) or Cu (I) ligands on nitrification exhibited significant linear relationships (P < 0.01) with the logarithms of the first stability constants (lgK1) and the total stability constants (lgKf) of corresponding complexes. Furthermore, lgKf of Cu (II) complexes exhibited a greater linear correlation than the corresponding lgK1 with the nitrification inhibition effects of the corresponding ligands; lgKf of Cu (I) complexes exhibited a steeper linear relationship than that of Cu (II) complexes with NPs or NIRs, and hence, nitrification inhibition effects of Cu (I) ligands almost doubled that of Cu (II) ligands when the lgKf values of Cu (I) and Cu (II) complexes have the same changes.

Thermal equilibrium and stability of copper complexes in silicon crystal

Formation of the photoluminescence (PL) Cu center (1.014 eV) for silicon crystals diffused with Cu at 700 °C was observed. For the samples with a Cu concentration lower than 1×1014 atom/cm3, almost the same amount of the Cu center was formed for the same concentration of Cu for all the cooling conditions employed without forming Cu precipitation, and the Cu center was very stable for a long storage time at room temperature. More frequent Cu precipitation occurred for the samples with higher Cu concentrations. Quenching of the equilibrium states of the Cu complexes at high temperatures did not occur by rapid cooling. Thermal equilibrium and stability of Cu complexes for the samples containing no Cu precipitates differed from those of the samples containing precipitates.