Synthesis and Structure of [NbCl3(NPPh2Fc)2]: The First Example of a Complex Containing a Redox‐functionalised Phosphaneiminato Ligand

Reaction of Me₃SiNPPh₂Fc (Fc = ferrocenyl) with niobium pentachloride affords [NbCl₃(NPPh₂Fc)₂], whose redox‐functionalised phosphaneiminato ligands exhibit remarkably different bend angles at nitrogen according to a crystal structure analysis.     

Ru/C-Catalyzed Hydrogenation of Aqueous Glycolic Acid from Microalgae – Influence of pH and Biologically Relevant Additives

Ethylene glycol (EG) is obtained by a novel, two-step approach combining a biotechnological and a heterogeneously catalyzed step. First, microalgae are cultivated to photobiocatalytically yield glycolic acid (GA) by means of photosynthesis from CO₂ and water. GA is continuously excreted into the surrounding medium. In the second step, the GA-containing algal medium is used as feedstock for catalytic reduction with H₂ to EG over a Ru/C catalyst. The present study focuses on the conversion of an authentic algae-derived GA solution. After identification of the key characteristics of the algal medium (compared to pure aqueous GA), the influence of pH, numerous salt additives, pH buffers and other relevant organic molecules on the catalytic GA reduction was investigated. Nitrogen- and sulfur-containing organic molecules can strongly inhibit the reaction. Moreover, pH adjustment by acidification is required, for which H₂SO₄ is found most suitable. In combination with a modification of the biotechnological process to mitigate the use of inhibitory compounds, and after acidifying the algal medium, over Ru/C a EG yield of up to 21 % even at non-optimized reaction conditions was achieved.     

Increasing the π–π Interactions in Trinuclear NiII3 Triplesalophen Complexes

The new triplesalophen ligand H₆kruse^Br was synthesized as a variation of the triplesalophen ligands H₆baron^R by replacing a phenyl by a methyl group at the terminal ketimine in order to allow closer contacts of trinuclear complexes due to less steric hindrance by the smaller methyl group. The ligand H₆kruse^Br was used to synthesize the trinuclear complex [(kruse^Br)Ni^II₃], which is insoluble in organic solvents despite the coordinating solvent pyridine. Recrystallization from pyridine results in the complex [(kruse^Br){Ni₂(Ni(py)₂)}], which was characterized by single‐crystal X‐ray diffraction. Two Ni^II ions are four‐coordinate by the salophen‐like subunits while the third Ni^II ion is six‐coordinate by two additional pyridine donors. The analysis of the molecular and crystal structure in comparison to that of Ni^II₃ complexes of (baron^R)^6– reveals that the methyl group in [(kruse^Br){Ni₂(Ni(py)₂)}] results in less ligand folding and in closer contact distance of two Ni^II₃ complexes by π–π interactions of 3.2 Å. This indicates that trinuclear complexes of H₆kruse^Br are more suitable than complexes of H₆baron^R as molecular building blocks for the anticipated synthesis of nonanuclear single‐molecule magnets.     

First-principles study of the magnetic exchange forces between the RuO2(110) surface and Fe tip

Magnetic exchange force microscopy (MExFM) is an important experimental technique for mapping the magnetic structure of surfaces with atomic resolution relying on the spin-dependent short-range exchange interaction between a magnetic tip and a magnetic surface. RuO₂ is a significant compound with applications in heterogeneous catalysis and electrocatalysis. It has been characterized recently as an antiferromagnetic (AFM) material, and its magnetism has been predicted somewhat surprisingly to play an important role in its catalytic properties. In the current study, we explore theoretically whether MExFM can visualize the magnetic surface structure of RuO₂. We use density functional theory (DFT) calculations to extract the exchange interactions between a ferromagnetic Fe tip interacting with an AFM RuO₂(110) surface, as a function of tip-surface distance and the position of the tip over the surface. Mimicking the MExFM experiment, these data are then used to calculate the normalized frequency shift of an oscillating cantilever tip versus the minimum tip-surface distance, and construct corrugation height line profiles. It is found that the exchange interaction between tip and surface is strongest for a parallel configuration of the spins of the tip and of the surface; it is weakest for an anti-parallel orientation. In a corrugation profile, this gives rise to a sizable height difference of 25 pm between the spin-up and spin-down Ru atoms in the RuO₂(110) surface at a normalized frequency shift =−10.12 fNm^1/2. The O atoms in the surface are not or hardly visible in the corrugation profile.     

Coatings with self-cleaning properties

The issue of self-cleaning significantly gained popularity due to the work of Barthlott and coworkers on the so called “Lotos-Effect^®”. They found out, that the cleanliness of the Lotos leaves originates from a combined effect of surface topography and hydrophobicity. The symbol of the beautiful Lotos flower as well as the fascination of surfaces being cleaned without any manual activity, simply by a rain shower, has since then stimulated the fantasy of many researchers. Our vision is to copy this mechanism from mother nature and to implement it into coating systems in such a way, that conventional application techniques, e.g. spray-coating, can be applied without the necessity of further process steps like e.g. soft lithography. Three different approaches will be presented in this paper. Roughness and contact angle measurements have been used to quantify the self-cleaning properties.     

ChemInform Abstract: Small Magnesium Clusters: Between van der Waals and Valence Bonds.

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