配合物(BenzMeIm)2[PtCl4]的合成与表征

通过离子液体氯化1-苄基-3-甲基咪唑（BenzMeIm-Cl）与PtCl₂的反应,合成了配合物（BenzMeIm）₂[PtCl₄],并用元素分析、红外光谱、紫外-可见光谱、¹H NMR、¹³C NMR和单晶X射线衍射对其进行了表征。单晶X射线分析表明,配合物结构属于P2₁/c空间群,晶胞参数和结构解析参数为：a=0.981 80（5）nm,b=0.861 47（3）nm,c=0.144 332（7）nm,β=92.480（2）°,V=121.96（1）nm³,R₁=0.014 4,wR₂=0.038 8。     

Synthesis and Structure of [4.5.5.5]Fenestranes ( = tetracyclo[5.4.1.04, 12.09, 12]dodecanes)

The preparation and the X-ray structure analysis of cis, trans, cis, cis-10-hydroxy-[4.5.5.5]fenestrane-1-methanol ( 8b ) is reported. The measured bond angles and bond lengths of the central C(C)₄ fragment are better reproduced by calculations with the AM 1 than by the MNDO method.     

Zur Kenntnis der Reaktionsfähigkeit von 4-Hydrazino-2,5-di-tert.-butyl-2-methyl-2H-imidazol

4-Hydrazino-2.5-di-tert.-Butyl-2-methyl-2H-imidazole (1) reacts with aldehydes and ketones to give condensation products (2 a-1). The reaction of1 with acyl chlorides and dicarboxylic acid chlorides gives rise to the corresponding 4-acylhydrazino-2H-imidazoles (3 a, b) and dicarboxylic-bis(imidazole-4-yl)-hydrazides (4 a-c) resp. Heating1 with acetyl bromide, ethyl orthoformate and 3-bromo-4-methyl-2-pentanone affords new condensedring systems5 a, b and7, resp.     

Structure of silica in <Emphasis Type="Italic"> Equisetum arvense</Emphasis>

Silicified regions in the stem and leaf of the horsetail Equisetum arvensewere studied by scanning and transmission electron microscopy. The silica was present as a thin layer on the outer surface with variation in the size of this layer depending on the part investigated. There was a dense arrangement of silica spheres with some density fluctuations. A loose arrangement of silica particles with variation in their size was found beneath this dense arrangement suggesting the agglomeration of silica. An electron diffraction pattern showed the presence of amorphous silica, with the short range order being comparable to that of silica from other chemical sources. The medium range order shows the presence of silica with a high inner surface. SAXS measurements correlate with the particle size observed in TEM, and provide values for surface fractals. A new method of plasma ashing to remove the organics is also described.     

Theory of excimer vibrational relaxation and U.V. emission in solid neon

A quantitative explanation is provided for the observed UV emission from Ne₂^* molecules in solid neon. An expression involving only known molecular quantities and lattice parameters is given for the rate of vibrational relaxation of an excimer, initially formed in a highly excited level, by interaction with the phonons. This expression is used to show that relaxation cannot proceed to the ground vibrational level of Ne₂^* during the radiative lifetime of the excimer (at the low temperatures at which the experiments are done). The calculation brings out that the vibrational population is concentrated at the n = 3 level when radiation takes place. The lineshape for dissociative UV emission from the n = 3 state of the excimer is computed, and found in very good agreement with experiment.     

Transient field precessions and electron polarizations for sulphur ions at high velocity

Effective transient magnetic fields have been measured for S ions traversing thin ferromagnetic foils of Fe, Ni and Gd at mean velocities of 8.0v ₀ (v ₀ =c/137). The deduced polarizations attached to 1s electrons are discussed together with all data available for light ions considering spin exchange scattering as polarization mechanism.     

Magnetic moment of the 19/2+ isomer in135Ce

Employing the time-integral PAC technique with an external magnetic field, the g-factor of the 19/2⁺ state at 2,125.6 keV in¹³⁵Ce was determined to be g=?0.07(1). This value favours a predominant (h ₁₁ ^2/?2 s ₁ ^2/?1 ) neutron configuration for this level. Its meanlife has been redetermined with improved precision to be τ=11.8(5) ns.     

Analyse der Milch

Ohne Zusammenfassung     

Time-resolved studies of neutral and ionized Nan clusters with femtosecond light pulses

The real-time dynamics of Na_n (n=3–21) cluster multiphoton ionization and fragmentation has been studied in beam experiments applying femtosecond pump-probe techniques in combination with ion and electron spectroscopy. Three dimensional wave packet motions in the trimer Na₃ ground state X and excited state B have been observed. We report the first study of cluster properties (energy, bandwidth and lifetime of intermediate resonancesNa _n ^* ) with femtosecond laser pulses. The observation of four absorption resonances for the cluster Na₈ with different energy widths and different decay patterns is more difficult to interpret by surface plasmon like resonances than by molecular structure and dynamics. Time-resolved fragmentation of cluster ions Na _n ⁺ indicates that direct photo-induced fragmentation processes are more important at short times than the statistical unimolecular decay.     

Stereoselektive Totalsynthese von natürlichem Phytol und Phytolderivaten und deren Verwendung zur Herstellung von natürlichem Vitamin K1

Steroselective Total Synthesis of Natural Phytol and Derivatives thereof; Use of these Compounds in the Synthesis of Natural Vitamin K₁ The Li₂CuCl₄-catalyzed couplings of the easily accessible bifunctional C₅ allylic acetates (E)- 18a and (E)- 18b with racemic hexahydrofarnesylmagnesium bromide ((3 RS/RS, 7 RS/SR)- 19a ) proceed with high chemo- and stereoselectivity (≥98% (E)-retention) to give the (2E, 7 RS/RS, 11 RS/SR)-phytol derivatives 1a and 1b , respectively, in yields of 72–80% (Scheme 5). The same couplings performed with optically active hexahydrofarnesylmagnesium bromide (3 R, 7 R)- 19a yielded the (E)-phytol derivatives of the natural series (7 R, 11R)- 1a and (7 R, 11 R)- 1b. Acid-catalyzed hydrolysis of(2 E, 7 R, 11 R)- 1b gave natural phytol((2 E, 7 R, 11 R)- 1c ) Friedel-Crafts alkylation of ‘menadiol monobenzoate’ 11b with (2 E, 7 R, 11 R)- 1a or (2 E, 7 R, 11 R)- 1b gave the dihydrovitamine K₁ derivative (2 E/Z, 7′ R, 11′R)- 12b ((E/Z)≈? 9:l). Conversion of configurationally pure (2 E, 7′ R, 11′ R)- 12b (yield 73%; obtained after chromatographic removal of the (Z)-isomer) into natural vitamine K₁ ((2 E,7′ R, 11′ R)- 2 ) was achieved in the usual way by saponification and oxidation with air. Some further investigations of the coupling reactions of bifunctional C₅ allylic synthons with hexahydrofarnesylmagnesium bromide (3 RS/RS, 7 RS/SR)- 19a showed the outcome of these reactions to be critically dependent on the nature of the leaving group, the double-bond geometry and the nature and concentration of the catalyst. Thus, the Li₂CuCl₄-catalyzed couplings of (3 RS/RS,7 RS/SR)- 19a with the allylic halides 29a and 29c as well as with p-toluenesulfonate 29b yielded besides the phytol derivatives 1a and 1b - also the S_N2′-type products 30a and 30b (Scheme 8, Table 2); the same result was found for the coupling with the cis-configurated allylic acetates (Z)- 18a and (Z)- 18b (Table 3). A similar loss of chemo selectivity as well as the loss of stereoselectivity in the coupling reactions of 19 with the bifunctional (E)-olefins of type 18 was observed when the Li₂CuCl₄-catalyst concentration was increased from 0.2 to 25 mol-% or upon substitution of Li₂CuCl₄ by copper (I) chloride or iodide (Table 4).