Alkali Cation Ligating Chains and Sheets of the Macrocycle 1, 7‐Dithia‐18‐Crown‐6 with Bridging Iodo‐ and Thiocyanatocuprate(I) Units

Treatment of an acetonitrile solution of CuI with 1, 7‐dithia‐18‐crown‐6 (1, 7‐DT18C6) at 100°C affords the coordination polymer ¹[(CuI)₂(1, 7‐DT18C6)₂] ( 1 ) in which 1, 7‐DT18C6 ligands bridge (CuI)₂ rings into double chains. 1D polymers of the type ¹[M{(Cu₃I₄)(1, 7‐DT18C6)}] (M = K, 2 ; M = Cs, 3 ) can be isolated under similar conditions in the presence of respectively KI and CsI. Both contain bridging heptacyclic [Cu₆I₈]^2— units but crystallise in different space groups, namely P1 and C2/m. The cesium cation of 3 is markedly displaced from the best plane through the thiacrown ether donor atoms. Reaction of 1, 7‐DT18C6 with CuSCN in the presence of NaSCN yields ²[{Na(CH₃CN)₂} {(CuSCN)₂(1, 7‐DT18C6)}][Cu(SCN)₂] ( 4 ), in which ¹[(CuSCN)₂] double chains are linked through macrocycles into sheets. Infinite ¹[{Cu(SCN)₂}^—] chains compensate the charge of the Na⁺ cations. Complex 1 can imbibe 0.90 mol CsNO₃ per mol of 1, 7‐DT18C6 pairs.     

Coordination properties of 6-deoxy-6-[1-(2-amino) ethylamino]-β-cyclodextrin and the ability of its copper(II) complex to recognize and separate amino acid enantiomeric pairs

The functionalized cyclodextrin 6-deoxy-6-[1-(2-amino)ethylamino]--cyclodextrin was synthesized, and an NMR, EPR, pH-metric, and calorimetric investigation was carried out in aqueous solution in order to ascertain its behaviour towards protonation and copper(II) complex formation. The thermodynamic parameters of the ternary complex formation with alanine, phenylalanine and tryptophan enantiomeric pairs were also determined (25° C andI=0.1 mol dm^–3). No thermodynamic enantioselectivity was observed in these systems, while a chiral, though poor, discrimination was observed in LEC: c.d. spectra also show enantiomeric stereoselectivity. The results of the present investigation, compared with previously reported results, suggest the occurence of acis-complex trans-complex equilibrium in such systems.     

Magnetic exchange interactions in tetrabromocuprate compounds

Magnetic and structural data for 28 compounds containing the tetrabromocuprate ion are presented. The parameters which affect the strength and sign of the magnetic superexchange interaction via non-bonding contacts between bromide ions are described and a system for describing the topology of the interaction between tetrahedra is proposed. Analysis of the data suggests that the primary factors affecting the magnetic exchange are the Br?Br distance, the Cu-Br?Br angle and the Cu-Br?Br-Cu dihedral angle.     

Cu4O12-Baugruppen aus planaren CuO4-Polygonen im Barium-Vanadyl-Oxocuprat(II)-phosphat Ba(VO)Cu4(PO4)4

Cu₄O₁₂ Groups Built of Square Planar CuO₄ Polygones in the Barium Vanadyl Oxocuprate(II) Phosphate Ba(VO)Cu₄(PO₄)₄ Single crystals of Ba(VO)Cu₄(PO₄)₄ have been prepared by solid state reactions just below the melting points of the reaction mixtures of BaP₂O₆, Cu₃(PO₄)₂, CuO, V₂O₅ and V₂O₃ in evacuated closed quartz glas tubes. The compound crystallizes with tetragonal symmetry, Space group D? P42₁2, a = 9.560(2), c = 7.160(2) Å, Z = 2. Special and new features of the crystal structure are to each other isolated Cu₄O₁₂ and (VO)(PO₄)₄ groups. The crystal chemistry of the Cu₄O₁₂ groups is discussed with respect to other compounds containing out of plane connected square planar MO₄ polygones.     

Investigation of electrochemical reactions on copper electrode in Cu4RbCl3I2 solid electrolyte

Investigations are carried out by potentiostatic method. It is found that at potentials ϕ less than 100 mV, a reaction rate of copper deposition is limited by the formation and the three-dimensional growth of copper nuclei and the rate of copper dissolution is limited by a two-dimensional growth of holes in the metal. The rate of nucleus growth was evaluated at 10⁻⁹...10⁻⁶ μm s⁻¹ depending on the potential. At ϕ>120 mV, the reaction rate is limited by charge transport at the exchange current density of 2.7 mA cm⁻² and the anodic transfer coefficient α_a≈ 0.45. The accumulation of a divalent copper phase on Cu/Cu₄RbCl₃I₂ interface at anodic polarization is explained by a parallel course of Cu⁺ − e → Cu²⁺ reaction.     

Enantioselektive Cyclopropanierung von 1,1-Diphenylethylen und Diazoessigester mit Kupfer-Katalysatoren

Copper(II) compounds catalyze the reaction of 1,1-diphenylethylene with diazoacetic acid ethylester. The main product is 2,2-diphenylcyclopropane carboxylic acid ethylester. The formation of the carbene dimerization products fumaric and maleic acid diethylester can be suppressed by the continuous addition of diazoacetic acid ester to 1,1-diphenylethylene.37 optically active ligands, partly new, were combined with copper(II)-acetate to givein-situ-catalysts. In five cases isolated copper complexes were used as catalysts. The best optical inductions in the formation of 2,2-diphenylcyclopro-pane carboxylic acid ethylester with up to 65.6% ee were achieved withSchiff base ligands, which derive from salicylaldehyde and amino alcohols, obtained from amino acid esters and phenylGrignard.

Prof. Dr.Karl Schlögl, Universität Wien, mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Amperometric Determination of lndole-3-acetic Acid Based on Platinum Nanowires and Carbon Nanotubes

Platinum nanowire （PtNW） can be grown by electrodeposition in polycarbonate membrane, with the average diameter of the nanowires about 250 nm. The PtNW and multiwalled carbon nanotubes （CNT） are then dispersed into chitosan （CHIT） solution. The resulting PtNW-CNT-CHIT material brings new capabilities for electrochemical devices by using the synergistic action of the electrocatalytic activity of PtNW and CNT. By dropping the PtNW-CNT-CHIT film onto the glassy carbon （GO） electrode surface, and after evaporation an amperometric sensor for the determination of indole-3-acetic acid （IAA） was developed. The oxidation current of IAA increased significantly at the PtNW-CNT-CHIT film coated GC electrode, in contrast to that at the CNT-CHIT modified GC. The linear response of the sensor is from 50 ng/ml to 50 μg/ml with a detection limit of 25 ng/mL.     

Darstellung und Kristallstruktur der Kupfer(I)-chalkogenolat-2,2′-Bipyridin-Komplexe [CuS(2,4,6-iPr3C6H2)]4(Bipy)2 und [CuSe(2,4,6-iPr3C6H2)]2(Bipy)2

Synthesis and Structure of Copper(I)Chalcogenolate-2,2′-Bipyridine Complexes [CuS(2,4,6-iPr₃C₆H₂)]₄(Bipy)₂ and [CuSe(2,4,6-iPr₃C₆H₂)]₂(Bipy)₂ The oligomeric homoleptical copper(I) chalcogenolate compounds [CuS(2,4,6-iPr₃C₆H₂)]_x=4,8 and [CuSe(2,4,6-iPr₃C₆H₂)]₆ react with 2,2′-bipyridine (Bipy) to yield the tetranuclear complex [CuS(2,4,6-iPr₃C₆H₂)]₄(Bipy)₂ ( 4 ) and the dinuclear complex [CuSe(2,4,6-iPr₃C₆H₂)]₂(Bipy)₂ ( 5 ). The structures of 4 and 5 were determined by X-ray analysis. In the eight-membered Cu₄S₄ core of 4 with chair conformation the copper atoms are linked by μ₂-bridging selenolate ligands. Only two copper atoms are coordinated by 2,2′bipyridine. The corresponding copper(I) selenolate complex ( 5 ) forms a folded four-membered Cu₂Se₂ ring with μ₂-bridging selenolate ligands. The Cu? Cu distance of 2.52 Å is relatively short. In contrast to the reaction performed with 2,2′-bipyridine, addition of phenantroline to 1 respectively 2 yields a dinuclear complex [CuS(2,4,6-iPr₃C₆H₂)]₂(Phen)₂ ( 10 ). NMR spectroskopic and cryoscopic measurement of 4 show that this complex dissociates into smaller fragments in solution which undergo rapid exchange reactions. However, corresponding investigations performed on 5 indicate that the solid state structure is maintained in solution. The electrochemical behaviour of 4, 5 and 10 was studied in CH₂Cl₂ and in any case no reversible redox processes could be observed.     

旋转铂盘电极上Cu(phen)_2~(2 )与6-巯基嘌呤的相互作用

在Tris-NaC1*(pH=7.2)缓冲溶液中,应用循环伏安法,微分脉冲伏安法、旋转圆盘电极实验、交流阻抗法及其数据模拟等技术研究了Cu(phen)2 25(phcn=1.10-邻菲咯啉)与6-巯基嘌呤(6-MP)的相互作用.结果显示.Cu(phen)2 2MP与6-MP无论在扩散控制过程或电化学控制过程都发生了相互作用.Cu(phen)2 2及其与6-MP的作用产物于铂电极上均呈现一对氧化还原峰,但后者呈现的氧化还原峰负移.峰电流减小.交流阻抗结果显示,无论6-MP存在与否,Cu(phen)2 2在交流阻抗谱上均呈现两个清晰的电容弧,但当6-MP存在时,电化学反应电阻和电化学吸脱附电阻均增大.Cu(phen)2 2在不同转速下的阻抗拟合结果显示.随转速增大.电化学反应电阻和电化学吸脱附电阻均减小.双电层电容呈增大趋势,而吸脱附电容呈减小趋势:当6-MP存在时.仍然呈现此变化规律.     

Simultaneous determination of copper and lead in ethanol fuel by anodic stripping voltammetry

The presence of trace metals in car fuels plays an important role in the engine maintenance. In addition, these metals contribute for the environmental contamination in big cities and their control is necessary. Square Wave Stripping Voltammetry (SWSV) is a very sensitive technique for elemental trace determination and was applied for ethanol fuel analysis. The first studies were done searching for the best conditions for copper determination in alcoholic medium, utilizing gold electrodes. During these studies, the possibility of the simultaneous determination of copper and lead in the same experiment was observed. Two procedures for the analysis of these metals were adopted: The direct quantification of metals in alcohol–water mixtures and a second way that involves the evaporation of the organic solvent and re-suspension of the ions with water+electrolyte. Good recovery values were obtained for synthetic samples spiked with known amounts of metals. The results obtained for the two methods were in good agreement. The detection limits for copper and lead in 75% ethanol–water ratio solution were calculated as 120 and 235 ng l⁻¹, respectively, for 15-min deposition time.