Innentitelbild: Regioregular Synthesis of Azaborine Oligomers and a Polymer with a syn Conformation Stabilized by N?H⋅⋅⋅π Interactions (Angew. Chem. 38/2015)

The regioregular synthesis of the first azaborine oligomers and a corresponding conjugated polymer was accomplished by Suzuki–Miyaura coupling methods. An almost perfectly coplanar syn arrangement of the heterocycles was deduced from an X‐ray crystal structure of the dimer, which also suggested that N H⋅⋅⋅π interactions play an important role. Computational studies further supported these experimental observations and indicated that the electronic structure of the longer azaborine oligomers and polymer resembles that of poly(cyclohexadiene) more than poly(p‐phenylene). A comparison of the absorption and emission properties of the polymer with those of the oligomers revealed dramatic bathochromic shifts upon chain elongation, thus suggesting highly effective extension of conjugation.     

Kinetic Monte Carlo study of nucleation processes on patterned surfaces

The properties of template-directed nucleation are studied in the transition region where full nucleation control is lost and additional nucleation beyond the prepatterned structure is observed. To get deeper insight into the microscopic mechanisms, Monte Carlo simulations were performed. In this context, the previously used continuous algorithm [F. Kalischewski, J. Zhu, and A. Heuer, Phys. Rev. B 77, 155401, (2008)] was replaced by a discrete one to reduce simulation time and to allow more detailed calculations. The applied method is based on the assumption that the molecules on the surface occupy the sites of a simple fcc lattice. It is shown that a careful mapping of the continuous Monte Carlo technique onto the discrete algorithm leads to a good reproduction of the former results by means of the latter method. Furthermore, the new method facilitates the calculation of the spatial distribution of nuclei on the surface. This provides a detailed comparison with experimental data.     

Dialkylaluminium‐, ‐Gallium‐, and ‐Indium‐Based Poly‐Lewis Acids with a 1,8‐Diethynylanthracene Backbone

Potential host systems based on a rigid 1,8‐diethynylanthracendiyl backbone were synthesised by treatment of 1,8‐diethynylanthracene with the Group 13 trialkyls AlMe₃, GaMe₃, InMe₃, AlEt₃ and GaEt₃. The resulting products were characterised by IR and multinuclear NMR spectroscopy, elemental analyses and determination of their crystal structures by X‐ray diffraction. The compounds are dimeric in the solid state and comprise two M₂C₂ heterocycles. Depending on the steric demand of the alkyl substituents at the metal atom, different types of binding modes were observed, which can be classified to lie between the ideals of side‐on coordination with almost linear primary M? C?C units and the 3c–2e coordination with symmetrically bridging alkynyl units in M‐C‐M bonds. As a solution in THF the dimers are broken into monomers and some are found to undergo ligand scrambling reactions.     

Direct electrochemistry and spectroelectrochemistry of osmium substituted horseradish peroxidase

In this contribution the substitution of the central protoporphyrin IX iron complex of horseradish peroxidase by the respective osmium porphyrin complex is described. The direct electrochemical reduction of the Os containing horseradish peroxidase (OsHRP) was achieved at ITO and modified glassy carbon electrodes and in combination with spectroscopy revealed the three redox couples Os^IIIHRP/Os^IVHRP, Os^IVHRP/Os^VHRP and Os^VHRP/Os^VIHRP. The midpoint potentials differ dependent on the electrode material used with E_1/2 (Os^III/IV) of − 0.4 V (ITO) and − 0.25 V (GC), E_1/2 (Os^IV/^V) of − 0.16 V (ITO) and + 0.10 V (GC), and E_1/2 (Os^V/VI)of + 0.18 V (ITO), respectively. Moreover, with immobilised OsHRP the direct electrocatalytic reduction of hydrogen peroxide and tert-butyl hydroperoxide was observed. In comparison to electrodes modified with native HRP the sensitivity of the OsHRP-electrode for tert-butyl hydroperoxide is higher.     

Restructuring and break-up of two-dimensional aggregates in shear flow

We consider single two-dimensional aggregates, containing glass particles, placed at a water/air interface. We have investigated the critical shear rate for break-up of aggregates with different sizes in a simple shear flow. All aggregates break-up nearly at the same shear rate (1.8 +/- 0.2 s(-)(1)) independent of their size. The evolution of the aggregate structure before break-up was also investigated. With increasing shear rate, the aggregates adopt a more circular shape, and the particles order in a more dense, hexagonal structure. A simple theoretical model was developed to explain the experimentally observed break-up. In the model, the aggregate is considered as a solid circular disk that will break near its diameter. The capillary and drag force on the two parts of the aggregate were calculated, and from this force balance, the critical shear rate was found. The model shows a weak size dependence of the critical shear rate for the considered aggregates. This is consistent with the experimental observations.     

Luminescence tuning of organoboron quinolates through substituent variation at the 5-position of the quinolato moiety

[Structure: see text] A series of organoboron quinolates with emission colors ranging from blue to red have been prepared. In comparison to the respective AlQ3 derivatives a distinct blue-shift of the emission is observed. Theoretical calculations serve to provide insight into the nature of the frontier orbitals and the effect of the substituents in the 5-position of the quinolate ligands on the relative HOMO and LUMO energy levels. An efficient new blue emitting material with a pinacolborane substituent has been identified.     

Structure and reactivity of a planar chiral naphthylferrocenylcopper heteroaggregate

A chiral 2-naphthylferrocenylcopper heteroaggregate (2) was prepared in high yield by reaction of (S_p-2-naphthylferrocenyl)trimethyltin with (C₆F₅Cu)₄ and fully characterized by multinuclear NMR, single crystal X-ray diffraction, and elemental analysis. The reactivity of 2 toward boron halides was examined. Rearrangement reactions resulted in formation of 1,2-, 1,3-, and 1,1′-disubstituted naphthylferrocenylboranes.     

Universality of the automorphism group of the real line

We discuss the question, whether each automorphism group (of cardinality at most ) of a linear order is embeddable into the automorphism group of the real line. We show that the answer to this question is independent of the axioms of ZFC: the answer is positive, if we assume < and Souslin's hypothesis; the answer is negative, if we assume orV=L.