Stabilization of dyes against hydrolytic decomposition by the formation of inclusion compounds

The decomposition reactions of the dyes phenol blue and murexide were measured spectroscopically in acidic solution at different temperatures. From these reaction rates and their temperature dependence in the absence and presence of various hosts, the stability constants and the reaction enthalpies of the dye complexes with noncyclic dextrins, cyclodextrins and cucurbituril were calculated.-Cyclodextrin enhances the stability of phenol blue in acidic solution. This effect is even more pronounced with cucurbituril. Due to the molecular structure of murexide this dye cannot form inclusion complexes with hosts containing hydrophobic cavities.     

REGULATION OF CHLOROPLAST DEVELOPMENT BY RED AND BLUE LIGHT

There are specific differences between red and blue light greening of etiolated seedlings of Hordevm vulgare L. Blue light results in a different prenyl lipid composition of chloroplast as compared to red light of equal quanta density. This is documented by a much higher prenylquinone content, higher chlorophyll a/b ratios, and lower values for the ratio xanthophylls to carotenes (x/c). The photosynthetic activity of “blue light” chloroplasts (Hill reaction) is higher than that of “red light” chloroplasts. These differences in prenylquinone composition and Hill-activity are associated with a different ultrastructure of chloroplasts. “Red light” chloroplasts exhibit a much higher grana content than “blue light” chloroplasts. The difference in thylakoid composition, photosynthetic activity and chloroplast structure found between blue and red light greening are similar to those found between sun and shade leaves and those between plants grown under high and low light intensities.     

A Journey from Thermally Tunable Synthesis to Spectroscopy of Phenylmethanimine in Gas Phase and Solution

Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine-intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state-of-the-art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined.     

Synthesis of Cucurbituril-spermine-[2]rotaxanes of the Amide-type

Abstract

[2]Rotaxanes with the macrocyclic ligand cucurbituril were prepared in yields between 10 and 90% from the reaction of the spermine complex with cucurbituril and different carboxylic acid chlorides in a two phase Schotten-Baumann reaction. This reaction type offers the possibility to synthesize a lot of different [2]rotaxanes. They are characterised by elemental analysis, ¹H-NMR spectroscopy and mass spectrometry.     

Ion-selective Dyes for the Complexation of Alkali and Alkaline Earth Cations

Abstract

The interactions of ion-selective dyes with alkali and alkaline earth cations in methanol have been investigated quantitatively. Both dyes examined are able to complex these cations selectively. From the spectral changes the stability constants of the complexes formed are calculated. The substituents at the nitrogen atoms of the diaza crown ethers obviously influence the stability of the complexes.     

Nanoscale Organolanthanum Clusters: Nuclearity-Directing Role of Cyclopentadienyl and Halogenido Ligands

Tetramethylaluminato/halogenido(X) ligand exchange reactions in half-sandwich complexes [Cp^RLa(AlMe₄)₂] are feasible in non-coordinating solvents and provide access to large coordination clusters of the type [Cp^RLaX₂]_x. Incomplete exchange reactions generate the hexalanthanum clusters [Cp^R₆La₆X₈(AlMe₄)₄] (Cp^R=Cp*=C₅Me₅, X=I; Cp^R=Cp′=C₅H₄SiMe₃, X=Br, I). Treatment of [Cp*La(AlMe₄)₂] with two equivalents Me₃SiI gave the nonalanthanum cluster [Cp*LaI₂]₉, while the exhaustive reaction of [Cp′La(AlMe₄)₂] with the halogenido transfer reagents Me₃GeX and Me₃SiX (X=I, Br, Cl) produced a series of monocyclopentadienyl rare-earth-metal clusters with distinct nuclearity. Depending on the halogenido ion size the homometallic clusters [Cp′LaCl₂]₁₀ and [Cp′LaX₂]₁₂ (X=Br, I) could be isolated, whereas different crystallization techniques led to the aggregation of clusters of distinct structural motifs, including the desilylated cyclopentadienyl-bridged cluster [(μ-Cp)₂Cp′₈La₈I₁₄] and the heteroaluminato derivative [Cp′₁₀La₁₀Br₁₈(AlBr₂Me₂)₂]. The use of the Cp′ ancillary ligand facilitates cluster characterization by means of NMR spectroscopy.     

乙基苯胺的转动光谱及分子结构

本文使用傅里叶变换微波谱仪研究了乙基苯胺类物质(邻乙基苯胺,间乙基苯胺,对乙基苯胺)的分子结构. 由于此类分子含氮原子(I¹⁴N=1),因此跃迁谱线中都呈现出核四级裂分. 通过比较实验测定得到的分子结构,可总结苯胺环上不同位置乙基的取代对氨基及分子整体结构的影响.