Heterocyclic nickel(II) dithiocarbamates with aromatic thiols as bridging ligands

Binuclear NiII dithiocarbamates, with aromatic monothiols as bridging ligands, of composition [Ni(-L) (Rdtc)]2 [dtc = S2CN, R = C4H8O (morph), C5H10 (pip), C4H8 (pld); HL = thiophenol, 4-methylthiophenol or 2-thionaphthol] and [Ni(-L)(HR1dtc)]2 {R1 = C11H11N2O (aap)} have been prepared and characterized by elemental analyses, i.r. and electron spectroscopy, magnetochemical and conductivity measurements, and thermal analysis. The methods used indicate that the complexes are diamagnetic, complex non-electrolytes with two square-planar NiS4 chromophores.     

Voltammetric determination of 2-mercaptobenzothiazole in a mixture of ethylene glycol + water

Voltammetry employing rotating platinum and disc electrodes proves to be a suitable method for determining 2-mercaptobenzothiazole in the mixture ethylene glycol + water in the relatively large concentration range 0.005–1% (i.e. approximately 3 × 10^?4 ?6 × 10^?2 mol 1^?1).The shapes of the voltammetric curves of thiol on both electrodes are essentially identical. During the gradual anodic polarization of the electrodes thiol is oxidized to a disulphide and adsorbed on the electrode surface, which is not accompanied by a conspicuous peak. In the more positive regions of the potential the next anodic process takes place:

manifested by the formation of an anodic peak.The calibration graphs are based on the linear dependence of the current of anodic peak I_A on the thiol concentration.In all cases the use of the rotating platinum electrodes proves to be more advantageous. The results are time reproducible, the determination requires no treatment of samples and requires approximately 15 min.     

Neighboring group participation and rearrangement in hypobromous acid addition to 10β-vinyl-cholestanes

Hypobromous acid addition to the diol $\text{Ia}$ yields two epimeric dibromo 6β,19a-epoxides $\text{III}$ and $\text{IV}$ in a 83:17 ratio. Under the same conditions the 6β-acetoxy derivative $\text{Ib}$ gives three products: $\text{III}$ (46%), its epimer $\text{VII}$ (5%) and the spyrocyclic ketone $\text{V}$ (49%).     

Chemie der Seltenerdmetalle, 12. Mitt.: pH-metrische Bestimmung des SystemsLn 3+−H4 T−KOH im sauren Bereich

Zusammenfassung Auf Grund von pH-Messungen wurden die erste und zweite Dissoziationskonstante der Weinsäure und Dissoziationskonstanten der KomplexionenLnH₂ T ⁺,Ln ₂H₂ T ⁴⁺,Ln(H₂ T)₂-undLnHT bestimmt.

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The first and second constant of dissociation of tartaric acid, and the constants of dissociation of the complex ionsLnH₂ T ⁺,Ln ₂H₂ T ⁴⁺,Ln(H₂ T)₂- andLnHT were determined, making use of p_H-measurements.

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Zugl. 30. Mitt. der Reihe: Koordinationsverbindungen mit organischen Hydroxysäuren.

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Ln ³⁺=La³⁺, Ce³⁺.

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H₄ T=C₄H₆O₆.     

Reducedab initio theoretical internuclear potentials of diatomic molecules

Ab initio theoretical ground state potentials of diatomic molecules calculated with the use of the variational CI-MO (configuration interaction method based on molecular orbitals) are analyzed with the use of the RPC (reduced potential curve) method. It is shown on a series of examples that the following statement is true even for inaccurateab initio calculations: in reduced form, the theoretical potential coincides to a high degree of accuracy with the reduced RKR (Rydberg-Klein-Rees) potential calculated from the spectroscopic data. Thus, with the use of the RPC method, even inaccurateab initio calculations (in particular for heavier molecules) may be used for the construction of rather accurate internuclear potentials and hence obtain a practical significance. The statement also holds for excited states if strong perturbations are not present.     

Visible Photoluminescence in Polysilanes

 The photoluminescence spectrum of poly-(methyl-(phenyl)-silanediyl) shows a strong narrow peak in the UV region which is of excitonic nature and related to σ^*-σ transitions. The broad emission peak in the visible region is related to polymer branching, charge transfer transitions, and defect electronic states (backbone scission). Chemical substitution of the Si backbone with π-conjugated side groups allows to generate photoluminescence also in the visible region.     

Die anwendung der ionexeigenschaften des silikagels zur trennung von metallen

The mechanism of sorption of cationic metal complexes on silica gel and the utilization of this process for separation of trace concentrations of metals are discussed. Some practical examples are given.