Darstellung, 19F-NMR-spektroskopischer Nachweis und Untersuchung zur Bildung der metallgemischten Clusteranionen [(Mo6−nWnCl)F]2−, n = 0−6

Preparation, ¹⁹F NMR Spectroscopic Evidence and Study of the Formation of Metal-Mixed Cluster Anions [(Mo_6?nW_nCl )F ]^2?, n = 0?6 The complete system of metal-mixed octahedral cluster ions [(Mo_6?nW_nCl)F]^2?, n = 0?6, is prepared by tempering Mo powder with WCl₆ at 600°C. A mixture containing inclusively the geometric isomers (n = 2, 3, 4) all ten possible species is transferred into the tetra-n-butylammonium salts (TBA)₂[(Mo_6?nW_nCl)F]. In the ¹⁹F nmr spectrum the 24 expected signals are observed, assigned on the basis of their chemical shifts, multiplicities and intensities, and confirmed by a 2D-¹⁹F-¹⁹F COSY spectrum. From the integrated intensities the distribution of the different components is derived revealing a non-statistical formation, in that isomers with Mo…?Mo or W…?W atoms in trans-positions in comparision to those with mixed Mo…?W axes are favoured, and that especially the homoleptic compounds Mo₆ and W₆ are present to an over-average extent. Evaluation of ¹⁹F chemical shifts reveals that F bound to W which is in antipodal position to Mo resonates at higher field compared to F bound to W in a W…?W arrangement, caused by an increased shielding, which is synonymous to a positive antipodal-effect by Mo. Vice versa F bound to Mo with an antipodal W resonates at lower field compared with F bound to Mo in an Mo…?Mo arrangement caused by an increased deshielding and synonymous a negative antipodal-effect by W. The chemical shifts, resulting from antipodal-effects, are different for the compounds within the [(Mo_6?nW_nCl)F]^2? - system. The difference of the antipodal effect of successive substitution products results in characteristic values designated as antipodal shift constants, depending on the kind of substituents, which is valid for other cluster systems, too.     

Das erste Titanat mit „Stuffed Pyrgoms”︁: RbNa3Li12[TiO4]4 = RbNa3Li8{Li[TiO4]}4

The First Titanate with ?Stuffed Pyrgoms”?: RbNa₃Li₁₂[TiO₄]₄ = RbNa₃Li₈{Li[TiO₄]}₄ By heating a well grounded mixture of the binary oxides Rb₂O, Na₂O, Li₂O, and TiO₂ [Rb:Na:Li:Ti = 1.1:3.1:12.5:4.0; 780°C, 41 d] we obtained RbNa₃Li₈{Li[TiO₄]}₄ as colourless platelike crystals. This first titanate with ?stuffed pyrgoms”? is isostructural with RbNa₃Li₈{Li[SiO₄]}₄, CsKNa₂Li₈{Li[SiO₄]}₄ and CsKNaLi₉{Li[SiO₄]}₄ [2]. The compound crystallizes tetragonal I4/m with a = 1 125.8(1) pm and c = 652.4(1) pm (Guinier-Simon-Data, Z = 2). The structure was determined by four-cyrcle-data (Siemens AED2, MoK) and leds to the residual values R = 3.7% and R_w = 3.1% (additional data see text). The Madelung Part of Lattice Energy (MAPLE), Effective Coordination Numbers (ECoN), Mean Fictive Ionic Raddii (MEFIR) and the Charge Distribution in Solids (CHARDI) are calculated and discussed.     

Structural Studies on Host + Guest Recognition Sensory Systems

Rhodamine B-ethylenediamine--cyclodextrins (RhB--CDen) and rhodamine B--cyclodextrins (RhB--CD) can form inclusive complexes with many guest molecules, a reaction which can be used as a nucleic acid probe. In this paper, the most stable conformations of RhB--CDen and RhB--CD have been determined by fluorescence experiments and analyzed by molecular modeling simulation. The interaction between RhB--CDen and two guest molecules, 1-borneol and cyclohexanol, has also been investigated. The results showed that RhB--CDen has a stronger interaction with 1-borneol than with cyclohexanol. Borneol could push the three aromatic-rings of rhodamine B out of the CD cavity, while the cyclohexanol could not. The interactive sites of host and guest are also presented.     

Reaction ofN-(3,3,3-trifluoro-2-trifluoromethylprop-1-enyl)dimethylamine with MgSO4·7H2O. Synthesis of 4,4-difluoro-5-trifluoromethyl-2-(2,2,2-trifluoro-1-trifluoromethylethyl)-4H-1,3-dioxine andcis/trans-3-dimethylamino-2-trifluoromethacryloyl fluoride

4,4-Difluoro-5-trifluoromethyl-2-(2,2,2-trifluoro-1-trifluoromethylethyl)-4H-1,3-dioxine andcis/trans-3-dimethylamino-2-trifluoromethacryloyl fluoride were obtained by reaction ofN-(3,3,3-trifluoro-2-trifluoromethylprop-1-enyl)dimethylamine with MgSO₄·7H₂O. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1069–1071, May, 1997.     

Cerebrosides fromfomitopsis pinicola (Sw. Ex Fr.) Karst.

Summary A cerebroside fraction was obtained from the fruit bodies offomitopsis pinicola using column chromatography and then separated into six compounds by reversed-phase HPLC. The sugar component of all cerebrosides wasD-glucose. The major fatty acids were 2-hydroxyfatty acids (C₁₄–C₁₈), the long chain base was identified as 9-methyl-C₁₈-4,8-sphingadienine which is widely distributed in fungi and reported to be essential for the fruit-inducing activity of fungi. Based on degradation studies, fast atom bombardment mass spectrometry, and different¹H and¹³C NMR investigations, the structure of the main cerebroside (1) was determined to be (4E,8E,2S,3R,2R)-N-2-hydroxypalmityl-1-O--D-glucopyranosyl-9-methyl-4,8-sphingadienine.

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Cerebroside ausFomitopsis pinicola (Sw. Ex Fr.) Karst.

Zusammenfassung Aus den Fruchtkörpern vonfomitopsis pinicola wurde ein Cerebrosidgemisch erhalten und durch Säulenchromatographie und HPLC in sechs Verbindungen aufgetrennt. Der Zuckerbaustein aller Cerebroside warD-Glucose. Die Fettsäurekomponenten waren 2-Hydroxyfettsäuren mit einer Kettenlänge zwische C₁₄ und C₁₈. Der Basenteil konnte als 9-Methyl-C₁₈-4,8-sphingadienin identifiziert werden. Diese Verbindung ist in Pilzen weit verbreitet und für die Fruchtbildung verantwortlich. Aus Abbaustudien, FAB-MS und verschiedenen¹H- und¹³C-NMR-Messungen wurde die Struktur des Hauptcerebrosids (1) als (4E,8E,2S,3R,2R)-N-2-hydroxypalmityl-1-O--D-glucopyranosyl-9-methyl-4,8-sphingadienin ermittelt.

     

Tandem transformations of tetrahydropyrrolo[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridines under the action of dimethyl acetylenedicarboxylate. A novel route to pyrrolo[2,3-<Emphasis Type="Italic">d</Emphasis>]azocines

Reactions of substituted tetrahydropyrrolo[3,2-c]pyridines with dimethyl acetylenedicarboxylate in protic and aprotic solvents were studied. A novel single-step method for the synthesis of pyrrolo[2,3-d]azocine derivatives was developed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2513–2519, November, 2005.     

Ion-exchange selectivity of a network calixarene-containing polymer obtained by the template synthesis on Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>, and Ba<Superscript>2+</Superscript> matrices

The ion-exchange equilibrium in network polymers obtained from cis-2,8,14,20-tetraphenyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene by template synthesis on cations Na⁺, K⁺, and Ba²⁺ as matrices was studied. The selectivity coefficients of ion exchanges Ba²⁺-H⁺, Na⁺-H⁺, K⁺-H⁺, Na⁺-K⁺, and Na⁺-NH₄ ⁺ were determined. The template synthesis enhanced the affinity of the polymers to matrix-forming cations by 6–8 kJ mol⁻¹. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1919–1922, August, 2005.     

Grid‐like Cobalt(II) Layered Complex with an Unprecedented Double 1,2‐Bis(1,2,4‐triazole‐1‐yl)methane Bridges

A novel two‐dimensional cobalt complex, [Co(btrm)₂(dca)]ClO₄ ( 1 , btrm = 1,2‐bis(1,2,4‐triazole‐1‐yl)methane, dca = dicyanamide), was synthesized and characterized. X‐ray diffraction analyses reveal that the title complex crystallizes in the monoclinic space group C2/m with a = 29.507(13)Å, b = 17.804(8) Å, c = 14.709(7) Å, β = 119.916(7)°, Z = 12, and R₁ = 0.0784, wR₂ = 0.2041. The cobalt atom involves a six‐coordinated CoN₆ environment, with a distorted octahedral coordination. Two btrm ligands connect the Co^II atoms with the exodentate nitrogen atoms on the 4‐position of triazole rings to form a sixteen‐membered rhombic grid. The unprecedented double btrm bridges and μ_1,5‐dca bridge connect the cobalt atoms to form a two‐dimensional grid‐like layered structure. The spectroscopic and magnetic properties have also been investigated.     

超分子自组装合成杯[4]芳烃黄原酸镍(Ⅱ)配合物

利用二维和三维的大环及笼状主体分子与金属离子直接进行自组装反应合成新型有机无机杂化分子是当前超分子领域的研究热点之一。这类分子不仅具有新奇的光、电、磁等特性，而且还可作为新型的主体分子在客体识别、催化、吸附与分离等方面有广阔的应用前景。杯芳烃是有机超分子领域广受     

On the conformational stability and dimerization of phosphotransferase enzyme I from Escherichia coli

The activity of enzyme I (EI), the first protein in the bacterial PEP:sugar phosphotransferase system, is regulated by a monomer–dimer equilibrium where a Mg²⁺-dependent autophosphorylation by PEP requires the homodimer. Using inactive EI(H189A), in which alanine is substituted for the active-site His189, substrate binding effects can be separated from those of phosphorylation. Whereas 1 mM PEP (with 2 mM Mg²⁺) strongly promotes dimerization of EI(H189A) at pH 7.5 and 20 °C, 5 mM pyruvate (with 2 mM Mg²⁺) has the opposite effect. A correlation between the coupling of N- and C-terminal domain unfolding, measured by differential scanning calorimetry, and the dimerization constant for EI, determined by sedimentation equilibrium, is observed. That is, when the coupling between N- and C-terminal domain unfolding produced by 0.2 or 1.0 mM PEP and 2 mM Mg²⁺ is inhibited by 5 mM pyruvate, the dimerization constant for EI(H189A) decreases from >10⁸ to <5 × 10⁵ or 3 × 10⁷ M⁻¹, respectively. With 2 mM Mg²⁺ at 15–25 °C and pH 7.5, PEP has been found to bind to one site/monomer of EI(H189A) with K_A′10⁶ M⁻¹ (ΔG′=−33.7±0.2 kJ mol⁻¹ and ΔH=+16.3 kJ mol⁻¹ at 20 °C with ΔC_p=−1.4 kJ K⁻¹ mol⁻¹). The binding of PEP to EI(H189A) is synergistic with that of Mg²⁺. Thus, physiological concentrations of PEP and Mg²⁺ increase, whereas pyruvate and Mg²⁺ decrease the amount of dimeric, active, dephospho-enzyme I.