Chiral induction in self-assembled helicates: CHIRAGEN type ligands with ferrocene bridging units

The aim of this work was the preparation of enantiomerically pure bis(pinene-bipyridine) ligands containing the ferrocenyl moiety. Several such ligands (1-3) were synthesized and completely characterized. These molecules can be diastereoselectively deprotonated at the acidic methylene group of the pinene moiety using a strong and sterically hindered base such as LDA. Subsequent reaction of the formed anion with alkyl halides yield the family of C(2)-symmetric enantiopure compounds (1a-c). Copper(I), silver(I), or zinc(II) complexes with several ligands (C1-C8) were prepared and structurally characterized in the solid state and in solution. Self-assembled helical species are formed in several cases. It became evident that the chiral groups present in the ligand do not completely determined the helical configuration of the assemblages. Diastereoselectivity is thus not complete with this type of ligands, contrary to other, similar ligands studied before.     

Röntgenographische,thermoelektrische, und IR-spektroskopische Untersuchung des Spinellsystems LixMn1−xV2O4

The spinels of the system Li_xMn_1?xV₂O₄ (0 ? x ? 1) have been prepared at 700–750°C from LiV₂O₄ and MnV₂O₄. The lattice constants decrease linearly with increasing x. In the region x>0.75, the d-electrons of V should be delocalized as the VV distances are lower than the critical VV separation of 2.94 Å. Experimentally, the samples with x>0.6 show no IR absorption bands and the Seebeck coefficient is near zero. The Seebeck coefficient can be described with a model of intermediate polarons and can be expressed by the equation $\text{Θ = 198}\text{log}\text{[1 +}\text{(1 ? x)}{}^5\text{x}\text{]}$.     

Die Struktur des Harpagosids. 2. Mitteilung über Iridoide

The structure and configuration of harpagoside, a bitter principle from the roots of Harpagophytum procumbens DC, have been elucidated by degradation reactions and NMR. spectra. The hitherto uncertain position of a secondary hydroxyl group could be assigned to C-6 of the aglycone moiety. As earlier postulated, harpagoside ( 1 ) as well as its saponification product, harpagide ( 12 ), belong to a series of natural enol ethers known as iridoids.     

Structures of Addition Products of Acetylenedicarboxylic Acid Esters with Various Dinucleophiles. An application of C,H-spin-coupling constants

Heterocyclic compounds obtained by addition of acetylenedicarboxylic acid esters to thioureas, cyclic amidines and o-difunctionalized aromatic systems have been studied by ¹³C-NMR. In particular, C, H-spin-coupling constants over two and three bonds were used to differentiate between the various constitutional isomers and to establish the configuration of trisubstituted exocyclic C, C-double bonds. The configurational significance and diagnostic value of vicinal cis and trans C,H-spin coupling is again demonstrated in the present series.     

In-situ HEED structure analysis of AlNx films grown by the simultaneous use of a radical beam source and ICB technique

A reactive ionized cluster beam technique (RICB) which was composed of a conventional ICB source and a radical beam source has been used to deposit stable and metastable polycrystalline AlN_x (0x1) films. Using in-situ high energy electron diffraction (HEED) at grazing incidence geometry, crystallographic properties such as structure, preferred orientation and interplanar dspacing values were determined and the relation to deposition parameters investigated. It could be shown that the simultaneous use of the ICB technique and a radical beam source to separately control the kinetic energy of the Al ions and the dissociation rate of molecular nitrogen, allows AlN films to be deposited with variable composition and crystal structures. In-situ HEED used in the transmission mode is an effective tool to investigate the crystallography of growing compound films such as AlN_x.     

The collisional quenching of O2*(1Δg) by NO and CO2

Rate coefficients for the collisional quenching of O₂^*(¹Δ_g) by NO and CO₂ at 2–8 torr and 300 K have been determined. k_NO = (2.48 ± 0.23) × 10^?17 cm³ molecule^?1 s^?1 and

= (2.56 ± 0.12) × 10^?18 cm³ molecule^?1 s^?1.     

The electronic structure of molecules by a many-body approach : II. Ionization potentials one-electron properties of pyridine and phosphoridine

The valence ionization potential (IPs) of pyridine and phosphoridine are studied by an ab initio many-body approach which includes the effects of electron correlation and reorganization beyond the Hartree-Fock approximation. For pyridine the order of the first three IPs is a₂(π), a₁(n), b₁(π), but the IPs of the a₂ and a₁ orbitals are so close together that they have to be regarded as identical in binding energy, which is also concluded from experiment. Whereas for pyridine the ordering of the IPs calculated in the HF approximation is incorrect, it is correct for phosphoridine. For this latter molecule the first three ionization potentials are due to ionization from the b₁(π), a₂(π), and a₁(n) orbitals. Several one-electron properties are calculated and compared with experimental and other theoretical data. The localized molecular orbitals are discussed as well.     

FRIEDEL-CRAFTS-Reaktionen der C7-, C8- und C12-Cycloalkane mit Kohlenmonoxid

The reaction of cycloheptane, cyclooctane, and cyclododecane with carbon monoxide under pressure in the presence of anhydrous aluminium chloride has been investigated. Cycloheptane leads to acetylcyclohexane and trans-2-methyl-cyclohexane carboxylic acid as main products. Cyclooctane yields 3- and trans-4-acetyl-methylcyclohexane and various dimethylcyclohexane carboxylic acids. From cyclododecane a mixture of numerous ketones has been obtained besides a mixture of acids.     

Konstruktion von Fundamentallösungen für Convolutoren in roumieuschen Ultradistributionsräumen

Fundamental solutions in a space D(M_p) of Roumieu ultradistributions are constructed for convolutors f whose Fourier transform is slowly decreasing. The solutions are of exponential growth if satisfies a stronger condition. These results include a constructive proof of the known existence theorem of Chou. For families of convolutors our method yields solutions which depend continuously on parameters.