Designed synthesis for some transition metal clusters involving bridging-sulfido ligand

Designed synthesis for some transition metal clusters involving bridging-sulfido ligands is reviewed. The basic concept with the use of reactive fragments as building blocks is described. It is shown that the sulfido ligands with lone-pair electrons and the unsaturated coordination sites play important roles in this rational synthesis. The relationship between the metallic coordination types of the sulfido ligands and their assembling activity in the compounds is summarized. Examples of the six kinds of unit construction with reactive fragments as building blocks are shown, indicating clearly that the unit construction is a reasonable way in the synthesis of transition metal clusters involving bridging sulfido ligands. Finally, the potential application of the unit construction schemes in the synthesis of transition metal clusters involving other bridging ligands is presented.     

环烷酸钴-氯二异丁基铝催化体系相态的研究

研究了Co(naph) 2 Al(i Bu) 2 Cl催化体系的相态 .通过Tyndall效应、电镜观察和超过滤实验 ,证明了Co(naph) 2 Al(i Bu) 2 Cl催化体系在溶有丁二烯的苯溶剂中以纳米级小颗粒分散 ,在较佳配比时 ,粒径在 1～10 0nm之间 ,为胶体催化剂 ,属于高度分散的多相催化体系 .催化剂的活性位位于胶粒表面 ,催化剂颗粒是无定形的 .以较佳配比得到的催化剂颗粒较小、分布均匀 ,催化丁二烯聚合反应活性高 .归纳出胶体催化剂的制备特点为外观类似于均相催化体系 ,但是制备方法 (各组分配比、加入顺序、陈化等 )对催化活性有明显的影响 .并给出将胶体催化动力学作均相动力学近似的条件 ,在聚合反应初期 ,且单体浓度比烷基铝以及其他填加物浓度大 2～ 3数量级     

UV-B induced keratinocyte apoptosis is blocked by 2-selenium-bridged beta-cyclodextrin,a GPX mimic

Cell proliferation and cell death of keratinocytes are tightly regulated to ensure epidermal homeostasis. UV-B induces keratinocyte apoptosis. UV-B also induces lipid peroxidation of keratinocytes to increase their amount of malondialdehyde (MDA). These phenomena can be explained by the production of reactive oxygen species (ROS) induced by UV-B radiation. We synthesized 2-selenium-bridged beta-cyclodextrin (2-SeCD) to imitate glutathione peroxidase (GPX), an important antioxidant and established a damage system, in which keratinocytes can be damaged by Ultraviolet B (UV-B) radiation. Using this damage system we studied 2-SeCD protection of keratinocytes against injury induced by UV-B. Experimental results showed that 2-SeCD could protect keratinocytes from apoptosis. Moreover, 2-SeCD inhibits lipid peroxidation of keratinocytes and scavenges ROS. 2-SeCD inhibits the UV-B induced apoptotic signal transduction. This antiapoptotic mechanism may be partly related to the elimination of hydrogen peroxide.     

An efficient preparation of N-per- (or poly)fluorophenyl pyrroles and N-fluoroalkanesulfonyl pyrroles

Hetero-Diels-Alder reaction of N-sulfinyl per- (or poly)fluoroaniline and N-sulfinylfluoroalkanesulfonyl amine with 1,3-dienes affords the corresponding cycloadduct 3,6-dihydro-1,2-thiazine-1-oxide which is readily converted to N-per- (or poly)fluorophenyl pyrrole and N-fluoroalkanesulfonyl pyrrole under mild reaction conditions in good yields.     

A series of novel Mo(W)/Cu/S heterobimetallic clusters containing SBu(t-) linkages. Synthesis, structure and spectroscopic characterisation

Six new copper(I) clusters, [Et4N]2[(MOS3)2Cu4(mu-SBu(t))2](1a: M = Mo; 1b: M = W), [Et4N][(MOS3)2Cu6(mu-SBu(t))3](2a: M = Mo; 2b: M = W) and [Bu4N]2[(MOS3)3Cu9(mu-SBu(t))3(mu3-SBu(t))][I](3a: M = Mo; 3b: M = W) have been prepared by the reactions of thiomolybdates and thiotungstates with CuSBu(t) under various conditions. The [(MOS3)2Cu4(mu-SBu(t))2](2-) dianions in 1a and 1b represent the first examples of double butterfly-shaped Mo(W)/Cu/S clusters. Addition of more Cu atoms to 1a or 1b resulted in the formation of incomplete double cubane-like clusters 2a or 2b. Single crystal structural studies showed that the anions of 2a and 2b are formed in a mouth-to-mouth fashion by two incomplete cubanes [MOS3Cu3](M = Mo, W) with three mu-SBu(t-) linkages. In the molecular structure of 3b, the SBu(t-) ligands act as mu- and mu3-bridges which link three WOS3Cu3 incomplete cubane-like fragments. An iodide ion crystallises in the cavity defined by the three incomplete cubanes in 3b. The spectroscopic and electrochemical properties of all the clusters are also studied.     

铁系丁二烯聚合胶体催化剂电导率的研究——探讨烷基铝的作用

研究了在２５℃加氢汽油介质中，铁系胶体催化剂［Ｆｅ（ｎａｐｈ）２Ａｌ（ｉ Ｂｕ）３—ＣＨ２ＣＨＣＨ２Ｃｌ］单组分、多组分按不同配比混合，非水体系电导率与浓度的关系，结合Ｔｙｎｄａｌ效应，聚合实验结果，得出Ａｌ（ｉ Ｂｕ）３以缔合状态存在并解离成离子对；它同环烷酸亚铁的作用是形成胶核的主要反应，与氯丙烯反应生成的氯化异丁基铝，在胶核表面参与形成活性中心；由过量Ａｌ（ｉ Ｂｕ）３解离的离子对形成的双电层结构，使胶粒保持相对稳定．催化剂各组分较佳配比对应稳定胶粒的形成；它具有颗粒小、均匀、较高的催化活性．催化体系加入丁二烯引起电导率下降表明活性中心是正离子性的．     

Syntheses,crystal structures,and characterizations of two novel cubane-like and double cubane-like molybdenum-copper-sulphur clusters {MoCu3S3(S2COEt)}(O)(Ph3P)3 and {Mo2Cu6S6(SCMe3)2}(O)2(Ph3P)4

Two novel heterometallic cubane-like and double cubane-like clusters, {MoCu₃S₃(S₂COEt)}(O)(Ph₃P)₃ I and {Mo₂Cu₆S₆(SCMe₃)₂}(O)₂(Ph₃P)₄ II, were synthesized by reaction of {MoCu₂S₃}(O)(Ph₃P)₃ with CuS₂COEt and CuSCMe₃, respectively. ClusterI crystallized in the triclinic space group (2) witha=12.766(6) Å,b=22.904(5) Å,c=10.522(3) Å, =99.86(2)°, =109.68(2)°, =86.84(3)°,V=2854(2) ų,Z=2,R=0.049 for 6622 observed reflections (I>5(I)) and 410 variables. ClusterII crystallized in the triclinic space group (2) with dimensionsa=14.212(4) Å,b=14.725(5) Å,c=12.396(8) Å, =110.32(4)°, =90.40(5)°, =62.88(2)°,V=2129(2) ų,Z=1,R=0.039 for 6020 observed reflections (I>3(I)) and 461 variables. ClusterI consists of a neutral cubane-like molecule with the core {MoCu₃S₃(S₂COEt)}²⁺, in which one corner of the cubane-like core is a novel triply bridging bidentate 1,1-dithiolato (xanthate, S₂COEt^–) ligand. ClusterII is a double cubane-like one, in which two cubane-like cores {MoCu₃S₃(SCMe₃)}²⁺ are connected by two Cu-S bonds of the triply bridging monothiolato (SCMe ₃ ^– ) ligand. Two different pathways of unit construction from a small heterometallic cluster {MoCu₂S₃}(O)(Ph₃P)₃ have been outlined. Comparisons of the selected bond lengths and bond angles for the cubane-like core {MoCu₃S₃ X} (X=Cl^–, Br^–, S₂COEt^–, SCMe ₃ ^– ) are given. Spectroscopic properties of the title clusters are also reported.     

Substituents effect on molecular structures of 13-vertex closo-metallacarboranes of rare earths. Synthesis and structural characterization of metallacarboranes bearing nido- and arachno-carborane ligands

Several new 13-vertex closo-metallacarboranes of rare earths incorporating nido- and arachno-carborane ligands have been prepared and structurally characterized. They represent a new class of metallacarboranes bearing a η⁷-carboranyl ligand recently discovered in our laboratory. This work indicates that the substituents on carborane cage carbons may affect the overall molecular structures of the resultant 13-vertex closo-metallacarborane complexes, but have little influence on the interactions between the central metal ion and nido- or arachno-carborane ligand.     

Synthesis, characterization, and catalytic activity of rare earth metal amides supported by a diamido ligand with a CH2SiMe2 link

A series of four coordinate rare earth metal amides with general formula ((CH2SiMe2)[(2,6- IPr2C6H3)N]2)LnN(SiMe3)2(THF) [(Ln = Yb(2), Y (3), Dy (4), Sm (5), Nd (6)] containing a diamido ligand (CH2SiMe2)[(2,6-iPr2C6H3)N]2(2-) with a CH2SiMe2 link were synthesized in good yields via reaction of [(Me3Si)2N]3Ln(III)(mu-Cl)Li(THF)3 with the corresponding diamine (CH2SiMe2)[(2,6-iPr2C6H3)NH]2 (1). All compounds were fully characterized by spectroscopic methods and elemental analyses. The structures of complexes 2, 3, 4, 5, and 6 were determined by single-crystal X-ray analyses. Investigation of the catalytic properties of the complexes indicated that all complexes exhibited a high catalytic activity on the cyclotrimerization of aromatic isocyanates, which represents the first example of cyclopentadienyl-free rare earth metal complexes exhibiting a high catalytic activity and a high selectivity on cyclotrimerization of aromatic isocyanates. The temperatures, solvents, catalyst loading, and the rare earth metal effects on the catalytic activities of the complexes were examined.     

Loss and back-coupling effects on subwavelength imaging of three-dimensional superlens

The loss and back-coupling effects on the subwavelength imaging of three-dimensional superlens are reported in this paper. The loss is added in the image region of a superlens. The back-coupling effects are considered by adding a shielded layer above the object region. (1) By adding loss in the image region, the long range plasmon mode is drastically suppressed. (2) The back-coupling shield above the objects has the effects of amplifying the higher spatial frequency components while suppressing the long range plasmon mode. Because of (1) and (2), the transfer function becomes flatter. Subsequently, the finer resolution of images is obtained. This is confirmed by the field and intensity distribution generated by the horizontal magnetic dipoles and vertical electric dipoles located in the object region and the image intensity distributions of the patterned mask structures in the lithography.