Rheniumkomplexe mit heterocyclischen Thiolen – Synthesen und Strukturen

Rhenium Compounds Containing Heterocyclic Thiols – Syntheses and Structures Reactions of trans‐[ReOCl₃(PPh₃)₂] with 1,3‐thiazoline‐2‐thiol (thiazSH), pyridine‐2‐thiol (pyrSH) or pyrimidine‐2‐thiol (pyrmSH) result in the formation of rhenium(V) oxo complexes or rhenium(III) species depending on the conditions applied. mer‐[ReOCl₃(thiazSH)(OPPh₃)], trans‐[ReCl₃(PPh₃)(thiazSH)₂], [ReO(2‐propO)(PPh₃)Cl(pyrS‐S,N)], cis‐[ReCl₂(PPh₃)₂(pyrS‐S,N)] and [ReCl₂(PPh₃)₂(pyrmS‐S,N)] have been isolated from such reactions and structurally characterized. cis‐[ReCl₂(PPh₃)₂(pyrS‐S,N)] and [ReCl₂(PPh₃)₂(pyrmS‐S,N)] are obtained in better yields by ligand substitution on trans‐[ReCl₃(MeCN)(PPh₃)₂]. The reaction between (n‐Bu₄N)[ReOCl₄] and purine‐6‐thiol (purinSH) gives the oxo‐bridged [O{ReO(purinS‐S,N)₂}₂].     

Quenching of bacteriochlorophyll fluorescence in chlorosomes from Chloroflexus aurantiacus by exogenous quinones

The quenching of bacteriochlorophyll (BChl) c fluorescence in chlorosomes isolated from Chloroflexus aurantiacus was examined by the addition of various benzoquinones, naphthoquinones (NQ), and anthraquinones (AQ). Many quinones showed strong quenching in the micromolar or submicromolar range. The number of quinone molecules bound to the chlorosomes was estimated to be as small as one quinone molecule per 50 BChl c molecules. Quinones which exhibit a high quenching effect have sufficient hydrophobicity and one or more hydroxyl groups in the alpha positions of NQ and AQ. Chlorobiumquinone has been suggested to be essential for the endogenous quenching of chlorosome fluorescence in Chlorobium tepidum under oxic conditions. We suggest that the quenching effect of chlorobiumquinone in chlorosomes from Chl. tepidum is related to the 1'-oxo group neighboring the dicarbonyl group.     

过渡金属对分子筛担载Pd催化剂上CO氧化性能影响

分别采用共浸和连续浸渍法制备了一系列添加过渡金属的Pd-M-Ox-NaZSM-5(M=Cr，Mn，Fe，Co，Ni，Cu，Zn，Mo，Zr等)负载型催化剂．以CO氧化为探针反应，考察了不同制备方法对CO氧化性能影响，结果表明共浸法制备的各催化剂其活性明显优于连续浸渍法．详细考察了反应温度、Fe含量、氢气预还原、空速以及水蒸气等对共浸Pd-Fe-Ox-NaZSM-5催化剂上CO氧化行为影响，并应用XRD和XPS等手段对催化剂体相结构和表面状态进行了表征．结果表明：加入Fe2O3可明显提高Pd/NaZSM-5催化剂活性，且催化CO氧化的转化率随反应温度及Fe含量增加而增加；空速增加以及H2预还原作用导致Pd-Fe-Ox-NaZSM-5活性有所降低；催化剂对水蒸气较为敏感．XRD测试结果表明催化剂中Pd组分处于较高分散状态，以红铁矿形式存在的Fe2O3的引入，促进了Pd物种在NaZSM-5载体上的分散．表面XPS分析证实Fe2O3与Pd物种间存在较强的相互协同作用，且催化剂表面Pd物种处于较高氧化状态．Pd的高分散及其与Fe2O3的相互协同作用是共浸催化剂具有高活性的关键因素．     

Spherical molecularly imprinted polymers (SMIPs) via a novel precipitation polymerization in the controlled delivery of sulfasalazine

Spherical molecularly imprinted polymers (SMIPs) have been prepared via a novel precipitation polymerization using sulfasalazine (prodrug used in the diseases of the colon) as template. The sulfasalazine was incorporated into SMIPs and into a spherical non-imprinted polymer (control), and then the release rate of the bioactive agent at different pH values was evaluated. Considerable differences in the release characteristics between imprinted and non-imprinted polymers have been observed. This opens the possibility of the development of drug release systems capable of modulating the release of a specific molecule. Photomicrography of spherical molecularly imprinted polymers (SMIPs).     

The design of molecules containing planar tetracoordinate carbon

A novel preference for planar tetracoordination was observed over the conventional tetrahedral arrangement in a new series of C₅H₂, C₅H₄, C₅H₄^1+/2+ and related compounds. The stability of these molecules is assessed with the ring-opening barriers, HOMO-LUMO gap, singlet-triplet energy differences and nucleus independent chemical shift values.     

Fe-exchanged montmorillonite K10--the first heterogeneous catalyst for acylation of sulfonamides with carboxylic acid anhydrides

Fe-exchanged montmorillonite K10 catalyzes a highly efficient reaction between sterically and electronically diverse sulfonamides and carboxylic acid anhydrides to furnish N-acylsulfonamides in excellent yield and high selectivity. The catalyst can also be reused several times.     

New nucleoside analogs from 2-amino-9-(beta-D-ribofuranosyl)purine

Four novel derivatives of 2-amino-9-(beta-D-ribofuranosyl)purine (1) were synthesised and fully characterised. When 1 was reacted with chloroacetaldehyde (a), 2-chloropropanal (b), bromomalonaldehyde (c) and a mixture of chloroacetaldehyde + malonaldehyde (d), 3-(beta-D-ribofuranosyl)-imidazo-[1,2a]purine (2), 3-(beta-D-ribofuranosyl)-5-methylimidazo-[1,2a]purine (3), 3-(beta-D-ribofuranosyl)-5-formylimidazo-[1,2a]purine (4) and 9-(beta-D-ribofuranosyl)-2-(3,5-diformyl-4-methyl-1,4-dihydro-1-pyridyl)purine (5) were formed, respectively. The products were isolated, purified by chromatography and characterised by MS, complete NMR assignment as well as fluorescence and UV spectroscopy. The yields of these reactions were moderate (14-20%). The fluorescence properties differed from those of the starting compound and the quantum yields were considerably lower.