Covalent Photosensitizer–Polyoxometalate‐Catalyst Dyads for Visible‐Light‐Driven Hydrogen Evolution

A general concept for the covalent linkage of coordination compounds to bipyridine‐functionalized polyoxometalates is presented. The new route is used to link an iridium photosensitizer to an Anderson‐type hydrogen‐evolution catalyst. This covalent dyad catalyzes the visible‐light‐driven hydrogen evolution reaction (HER) and shows superior HER activity compared with the non‐covalent reference. Hydrogen evolution is observed over periods >1 week. Spectroscopic, photophysical, and electrochemical analyses give initial insight into the stability, electronic structure, and reactivity of the dyad. The results demonstrate that the proposed linkage concept allows synergistic covalent interactions between functional coordination compounds and reactive molecular metal oxides.     

Stereoselectivity in Pinacol-Homocoupling Mediated by Samarium Diiodide

Summary. The stereoselectivity of the pinacol-coupling of various substituted benzaldehydes mediated by samarium diiodide was investigated. The dependence of product-ratios, yields, and stereoselectivities on the substrate, the substrate-reagent-ratio, and the solvent is described.     

Perylenediimide-surfactant complexes: thermotropic liquid-crystalline materials via ionic self-assembly

In this communication we present the facile preparation and characterisation of thermotropic liquid-crystalline materials from the ionic self-assembly of a charged perylenediimide derivative and oppositely charged surfactants.     

Impurity distribution in a solid-liquid interface during static layer crystallization

The impurity distribution inside crystalline layers in static layer crystallizations was explored theoretically and experimentally for a binary eutectic mixture of caprolactam and water. The impurity distribution in the layer is modeled by a mass balance equation coupled with an energy balance equation. The mass balance equation is established with a combination of the growth of the layer and the diffusional movement of impurity. The mathematical model was solved by a numerical method. The predictions are discussed with respect to the interfacial distribution coefficient, concentration, and temperature at the solid-liquid interface, crystalline layer thickness, and concentration of the layer. The impurity distribution obtained by the model was appropriately verified with the results obtained by the experiments.     

Synthesis of naturally occurring phloroglucinol derivatives

Starting with isobutyryl phloroglucinol nine naturally occurring compounds from $\text{Helichrysum}$ species were synthesized.     

An optical investigation of Ho2(SO4)3 ·8H2O

The optical absorption spectra of Ho³⁺ in single crystals of Ho₂(SO₄)₃·8H₂O have been studied between 2500 A and 9000 A at 4.2 and 77 K. The microscopic crystal structure has been related to the macroscopic shape of the crystals. From the polarization of the optical transitions it is found that the point symmetry of the crystalline electric field (CEF) at the site of the rare earth ions in the sulfate lattice is well described by C_1h. The CEF parameters associated with this symmetry were derived from the observed Stark splitting of the [SL]?J levels and the polarization of the optical transitions. We suggest that the magnetically inequivalent sites observed in Tm₂(SO₄)₃·8H₂O are due to triclinic distortions of the monoclinic CEF.     

Si-methyl- und-chlorsubstituierte Disilazane

The hitherto unknown methylchlorodisilazanes Cl₂ meSi-NH-Sime ₃ (IV), Cl₂ meSi-NH-SimeCl₂ (VII), Cl₃Si-NH-Si_{me 2}Cl (VIII) and Cl₃Si-NH-SimeCl₂ (IX) (Scheme 1) were prepared (equ. 6–11), characterized by their properties (Table 1) and transformed into the derivatives XI–XIII.Es wurden die bisher unbekannten Methylchlordisilazane (IV), (VII), (VIII) und (IX) dargestellt (Rkk. 6–11), charakterisiert (Tab. 1) und in einige Derivate (XI–XIII) übergeführt.

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94. Mitt.:U. Wannagat undE. Bogusch, Mh. Chem.102, 1806 (1971).

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Mit Auszügen aus den Diplomarbeiten a)J. Herzig (1966) und b)P. Schmidt (1966) sowie der DissertationM. Schulze (1968), alle Techn. Universität Braunschweig.