Über faktorisierbare Lösungen von Riccatischen Differentialgleichungen

Ohne ZusammenfassungHerrn Hans Wittich zum 60. Geburtstag am 4. Mai 1971 gewidmet     

Ternäre Erdalkali-und Seltene Erd-Silicide und-Germanide mit AlB2-Struktur

Zusammenfassung Der AlB₂-Strukturtyp (C 32) wurde für SrGeZn, elf Verbindungen mit der ZusammensetzungRGe_1,33Cu_0,67 und vierzehn Silicide der FormelRSi_1,33Cu_0,67 aufgefunden, wobeiR ein Atom der Erdalkaligruppe oder der Seltenen Erdelemente symbolisiert. Das Auftreten von binären und ternären Vertretern dieses Strukturtyps wird in Beziehung gesetzt zu einem bestimmten Bereich der Valenzelektronenkonzentration.

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Ternary alkaline earth- and rare earth-silicides and-germanides with AlB₂-structure

The AlB₂ type structure was found with SrGeZn, eleven phases of compositionRGe_1,33Cu_0,67 and fourteen silicides of compositionRSi_1,33Cu_0,67 whereR indicates an alkaline earth or a rare earth element. The occurence of binary and ternary representatives of this structure type can be correlated with a certain range of valence electron concentration.

     

Tuning of redox properties for the design of ruthenium anticancer drugs: part 2. Syntheses, crystal structures, and electrochemistry of potentially antitumor [Ru III/II Cl6-n(Azole)n]z(n = 3, 4, 6) complexes

A series of mixed chloro-azole ruthenium complexes with potential antitumor activity, viz., mer-[RuIIICl3(azole)3] (B), trans-[RuIIICl2(azole)4]Cl (C), trans-[RuIICl2(azole)4] (D), and [RuII(azole)6](SO3CF3)2 (E), where azole = 1-butylimidazole (1), imidazole (2), benzimidazole (3), 1-methyl-1,2,4-triazole (4), 4-methylpyrazole (5), 1,2,4-triazole (6), pyrazole (7), and indazole (8), have been prepared as a further development of anticancer drugs with the general formula [RuCl4(azole)2]- (A). These compounds were characterized by elemental analysis, IR spectroscopy, electronic spectra, electrospray mass spectrometry, and X-ray crystallography. The electrochemical behavior has been studied in detail in DMF, DMSO, and aqueous media using cyclic voltammetry, square wave voltammetry, and controlled potential electrolysis. Compounds B and a number of C complexes exhibit one RuIII/RuII reduction, followed, at a sufficiently long time scale, by metal dechlorination on solvolysis. The redox potential values in organic media agree with those predicted by Lever's parametrization method, and the yet unknown EL parameters were estimated for 1 (EL = 0.06 V), 3 (EL = 0.10 V), 4 (EL = 0.17 V), and 5 (EL = 0.18 V). The EL values for the azole ligands 1-8 correlate linearly with their basicity (pK(a) value of the corresponding azolium acid H2L+). In addition, a logarithmic dependence between the homogeneous rate constants for the reductively induced stepwise replacement of chloro ligands by solvent molecules and the RuIII/RuII redox potentials was observed. Lower E(1/2) values (higher net electron donor character of the ligands) result in enhanced kinetic rate constants of solvolysis upon reduction. The effect of the net charge on the RuIII/RuII redox potentials in water is tentatively explained by the application of the Born equation. In addition, the pH-dependent electrochemical behavior of trans-[RuCl2(1,2,4-triazole)4]Cl is discussed.