Selbstorganisation von molekularen Tennisbällen: Molekulare Erkennung

The assembly of multiple copies of the same simple subunit to higher level architectures leads to complex functions beyond the capabilities of each isolated subunit. The validity of this principle at the molecular level is illustrated with hydrogenbonded capsules that developed from a playground for fundamental research to the object of materials science. Two identical copies of a selfcomplementary monomer are sufficient to implement functions which span from the generation of closed‐shell containers with the ability to encapsulate guest molecules to chiral recognition and catalysis. Multiple copies assemble to hydrogenbonded polymers containing capsules like beads on a string which feature more complex properties such as liquid‐crystalline behavior and the formation of fibers with a considerable load carrying capacity.     

Palladiumpnictide des Zirconiums und Hafniums mit einem Metall : Nichtmetall‐Verhältnis von 2 : 1

Palladium Pnictides of Zirconium and Hafnium with a Metal : Nonmetal Ratio of 2 : 1 The following compounds were prepared by heating the elements in the range of 800°–1100 °C and characterized by means of X‐ray single crystal methods: Zr₅Pd₉P₇ (a = 3.815(1), b = 26.319(5), c = 6.511(1) Å) and Hf₅Pd₉P₇ (a = 3.776(1), b = 26.382(7), c = 6.500(3) Å) are isotypic and crystallize in a new structure type (Amm2; Z = 2). This also applies to ZrPdAs (a = 3.887(1), b = 19.288(6), c = 6.690(2) Å; Pmmn; Z = 10), while ZrPdSb (a = 6.814(1), b = 4.289(1), c = 7.870(2) Å) forms a TiNiSi analogous structure (Pnma; Z = 4). Common feature of all structures is the tetrahedral environment of Pd by X atoms (X: P, As, Sb). The linking of the tetrahedra leads to a PdX framework with holes, in which the Zr and Hf atoms respectively are located. The non‐metal atoms have trigonal prismatic metal coordination with three additional metal atoms outside the rectangular faces of the prisms. This XMe₉ polyhedron (Me = metal) is typical for the large family of ternary pnictides with a metal : non‐metal ratio of 2 : 1.     

Der Einfluss von Substituenten in Stellung 4 auf das n-Ionisationspotential des Chinuclidins

The vertical ‘lone-pair’ ionization potentials I_v(n) of fifteen 4-substituted quinuclidines, of aza-adamantane and of aza-twistane have been determined by photoelectron spectroscopy. It is shown that the dependence of I_v(n) on the nature of the substituent S can be rationalized in terms of the contribution to the local potential at the ionization site (i.e. the nitrogen centre) by the dipole of S. Both the solution pK's and I_v(n) correlate with classical substituent parameters (e. g. σ* or F) and with each other. However, no conclusions can be drawn from such regressions concerning a close relationship between the electronic mechanisms responsible for the observed changes in pK or I_v(n).     

Zum Einfluß von Kaliumtricyanmethanid und -dicyanamid auf das anodische Verhalten von Kupfer in wäßrigen Lösungen

On the Influence of Potassium Tricyanmethanide and Dicyanamide on the Anodic Behaviour of Copper in Aqueous Solutions Electrochemical measurements on copper anodes in aqueous solutions of potassium tricyanmethanide and dicyanamide show a strong tendency of passivation of copper. Comparative galvanostatic investigations of copper in aqueous solutions of the potassium halides and pseudo-halides KX (X: Cl, Br, J, SCN, N(CN)₂, N(CN)₂, C(CN)₃) are indicating a clear increase in the efficiency of the formation of a passivating layer in the series Cl^? ? Br^?<J^?<SCN^?<N(CN)₂^?<C(CN)₃^?. In solutions of halides the first anodic process is followed by the second one at few increased potential, whereas a broad passive areal appears in solutions of pseudohalides, for instance in the cases of tricyanmethanide and dicyanamide.     

Ternäre Nickelphosphide und -arsenide mit einem Metall: Nichtmetall-Verhältnis von 2:1

Ternary Phosphides and Arsenides of Nickel with a Metal: Non-Metal Ratio of 2:1 Several new ternary phosphides and arsenides of nickel were prepared by reaction of the elements. SrNi₅P₃, SrNi₅As₃, and EuNi₅As₃ crystallize in the LaCo₅P₃ structure with the following lattice constants [Å]: BaNi₉P₅ (a = 6.534(1) Å, c = 10.847(2) Å) and BaNi₉As₅ (a = 6.760(1) Å, c = 11.226(2) Å) crystallize in a new type of structure (P6₃/mmc, Z = 2). The characteristic polyhedra are trigonal Ni-antiprisms centered by P or As atoms and trigonal Ni-prisms with vacant centres and sides capped by non-metal atoms. U₂Ni₁₂P₇ (a = 9.077(2) Å, c = 3.694(1) Å) has a Zr₂Fe₁₂P₇ structure (P6 , Z = 1).