过渡金属不对称催化氧杂苯并降冰片烯开环反应的研究进展

综述了近年来过渡金属不对称催化氧杂苯并降冰片烯开环反应的研究进展, 包括钯催化、镍催化、铜催化和铑催化四部分内容, 并对部分反应的机理进行了介绍.     

Supramolecular-induced regiocontrol over the photochemical [4 + 4] cyclodimerization of NHC- or azole-substituted anthracenes

Thanks to the impressive control that microenvironments within enzymes can have over substrates, many biological reactions occur with high regio- and stereoselectivity. However, comparable regio- and stereoselectivity is extremely difficult to achieve for many types of reactions, particularly photochemical cycloaddition reactions in homogeneous solutions. Here, we describe a supramolecular templating strategy that enables photochemical [4 + 4] cycloaddition of 2,6-difunctionalized anthracenes with unique regio- and stereoselectivity and reactivity using a concept known as the supramolecular approach. The reaction of 2,6-azolium substituted anthracenes H₄-L(PF₆)₂ (L = 1a–1c) with Ag₂O yielded complexes anti-[Ag₂L₂](PF₆)₄ featuring an antiparallel orientation of the anthracene groups. Irradiation of complexes anti-[Ag₂L₂](PF₆)₄ proceeded under [4 + 4] cycloaddition linking the two anthracene moieties to give cyclodimers anti-[Ag₂(2)](PF₆)₂. Reaction of 2,6-azole substituted anthracenes with a dinuclear complex [Cl-Au-NHC–NHC-Au-Cl] yields tetranuclear assemblies with the anthracene moieties oriented in syn-fashion. Irradiation and demetallation gives a [4 + 4] syn-photodimer of two anthracenes. The stereoselectivity of the [4 + 4] cycloaddition between two anthracene moieties is determined by their orientation in the metallosupramolecular assemblies.

A supramolecular templating strategy that enables the photochemical [4 + 4] cycloaddition of 2,6-difunctionalized anthracene derivatives with unique stereoselectivity has been developed based on metal-NHC units.     

Na2O-P2O5系晶体微结构形态的拉曼光谱研究及其ab initio计算

本文采用激光拉曼光谱仪测量了磷酸钠二元系(1-x)Na₂O·xP₂O₅(x=0.25,0.33,0.50,1.0)几种晶体的拉曼光谱,比较并解释了随化学组成而变化微结构单元的拉曼振动模。同时用Gaussian 98W量子化学软件从头计算了这几种化合物的拉曼光谱。实验和计算均表明,磷酸盐晶体的基本结构单元为磷氧四面体[PO₄],并且晶体中磷氧四面体的伸缩模振动频率与连接中心磷原子的桥氧数密切相关,随桥氧数增加而升高。此外还解释了模拟图谱与实验谱差异的原因。     

应用普通ICP-MS和八极杆碰撞/反应池(ORS)技术测定动植物样品中的As和Se的比较

使用普通电感耦合等离子体质谱法(ICP MS)测定一些标准参考物质中多种元素的浓度,该方法不仅可测定常规的有毒元素如As,Pb ,Hg,Cd ,还可以测定常量元素包括P ,Ca,Fe ,K ,Na等。实验研究了消解样品的方法、回收率和方法的检测限等,证明ICP MS的EPA2 0 0 8标准干扰校正方法用于测定食品和植物样品中多元素浓度是可行的。应用ICP MS的八极杆碰撞反应池(ORS)技术测定As ,Se等元素,比较了配置ORS系统与不配置ORS系统的ICP MS仪器对这两种元素测定的结果,讨论了ArCl和ArAr干扰的消除,发现ORS系统可以有效地消除样品基体产生的ArCl,ArAr等分子离子对样品中超痕量的As,Se的干扰。     

生物矿化、仿生合成与形貌调控

介绍了生物矿化材料的种类、结构、特点、形貌调控原则以及基于微生物、蛋白质、多肽、氨基酸和核酸等晶体调节剂的生物矿化材料的合成,总结了近年来生物矿化和彷生合成领域的研究进展.     

Synthesis and characterization of half-sandwich iridium complexes containing 2,6(7)-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene and ancillary ortho-carborane-1,2-dichalcogenolato ligands

The binuclear half-sandwich iridium complexes {Cp^∗IrCl₂}₂(μ-2,6(7)-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene) (3) and {Cp^∗Ir[E₂C₂(B₁₀H₁₀)]}₂(μ-2,6(7)-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene) (E = S(5a), Se(5b)) were prepared from the reaction of [Cp^∗IrCl(μ-Cl)]₂ or the “pseudo-aromatic” half-sandwich iridium complex Cp^∗Ir[E₂C₂(B₁₀H₁₀)] (E = S(4a), Se(4b)) with a tetrathiafulvalene (TTF) derivative 2,6-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene (2) at room temperature. The complexes (3, 5a and 5b) have been fully characterized by IR and NMR spectroscopy, as well as elemental analysis. And the molecular structures of 2 and 5a were established through X-ray crystallography. It is interesting that infinite tunnels are created by repeating ‘buckled bowl’ molecules of 5a.     

Bis-imine-cyclometalated macrocycles: synthesis, characterization and observation of solution behaviour

A novel class of cyclometalated macrocycles [(Cp*Ir)(2)(R-N=C-C(6)H(2)-C=N-R)(2)](2)(pyrazine)(2)·(OTf)(4) [R = Ph (4a), p-MeOC(6)H(4) (4b), p-MeC(6)H(4) (4c), p-ClC(6)H(4) (4d), Me (4e)]; [(Cp*Rh)(2)(R-N=C-C(6)H(2)-C=N-R)(2)](2)(pyrazine)(2)·(OTf)(4) [R = Ph (4a'), p-MeOC(6)H(4) (4b'), p-MeC(6)H(4) (4c')] and [(Cp*Ir)(2)(R-C=N-C(6)H(4)-N=C-R)(2)](2)(pyrazine)(2)·(OTf)(4) [R = Ph (5a), p-MeOC(6)H(4) (5b)] was stepwise constructed through the double-site C-H activation of aromatic bis-imine substrates. The structures of binuclear complexes and tetranuclear macrocycles were confirmed by single-crystal X-ray diffraction. Isomers were found both in binuclear species and macrocyclic complexes. Flexible substrates led to the existence of isomers for binuclear species, yet gave no isomers after macrocyclic constructions; rigid ones, in contrast, led to isomers only for macrocyclic species. The isomers of tetranuclear macrocycles were thermodynamically stable to reversible transformation on a scale of days. Robust bonding and a certain degree of rigidity were invoked to explain the existence of isomers. This is the first example, to our knowledge, in which coordinated macrocycles containing half-sandwich Cp*M (M = Ir, Rh) fragments have been constructed, without a dynamic reversible process.     

Discrete half-sandwich Ir, Rh-based organometallic molecular boxes: synthesis, characterization, and their properties

The treatment of binuclear complexes [Cp*(2)M(2)(μ-QA)Cl(2)] (M = Ir, 2a; M = Rh, 2b) (H(2)QA = 1,4-dihydroxyanthraquinone) with pyrazine or bifuncational pyridyl-based ligands (4,4'-dipyridine (bpy), E-1,2-bis(4-pyridyl)ethene (bpe), 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo), and 2,5-bis(4-pyridyl)-1,3,4-thiadiazol (bpt)) in the presence of AgOTf (OTf = CF(3)SO(3)) in CH(3)OH, gave the corresponding tetra-nuclear complexes, with a general formula of [Cp*(4)M(4)(μ-QA)(2)(μ-L)(2)](OTf)(4) (M = Ir, 3a-7a; M = Rh, 3b-7b), respectively. The molecular structure of [Cp*(4)Ir(4)(μ-QA)(2)(μ-pyrazine)(2)](OTf)(4) (3a) has been determined by single-crystal X-ray analysis, revealing that the metal centers were connected by pyrazine and bis-bidentate QA(2-) ligands to construct a rectangular cavity with the dimension of 7.30 × 8.41 × 6.92 ?. Complexes 3a and 3b were found to exhibit selective trapping of halocarbons properties.     

Twisted intramolecular charge-transfer state of trans-3-(N,N-Dimethylamino)-4'-cyanostilbene: The C−C bond twisting

Whether a twisted intramolecular charge-transfer (TICT) state is formed is an important issue for understanding the fluorescence properties of a push-pull organic dye. Here we report a position effect of the donor substituent on the TICT state formation of aminostilbenes: namely, trans-3-(N,N-dimethylamino)-4′-cyanostilbene ( mDCS ) behaves differently from its TICT-free para isomer DCS and forms a TICT state in acetonitrile (MeCN). The TICT state of mDCS also differs from that of many previously reported aminostilbenes by twisting a C−C bond instead of a C−N bond. In addition, among the ring-bridged model compounds mDCS-N , mDCS-C1 , and mDCS-C2 , we observed an unusual electronic effect of the ring-bridging in mDCS-C2 that mitigates the impact of the TICT state on the fluorescence properties. Both the C−C bond twisting in mDCS and the ring-bridging electronic effect in mDCS-C2 provide new insights into the TICT chemistry of aminostilbenes.     

Unravelling the Roles of Solvophobic Effects and π⋅⋅⋅π Stacking Interactions in the Formation of [2]Catenanes Featuring Di-(N-Heterocyclic Carbene) Building Blocks

A series of [2]catenanes has been prepared from di-NHC building blocks by utilizing solvophobic effects and/or π⋅⋅⋅π stacking interactions. The dinickel naphthobiscarbene complex syn-[ 1 ] and the kinked biphenyl-bridged bipyridyl ligand L² yield the [2]catenane [ 2-IL ](OTf)₄ by self-assembly. Solvophobic effects are pivotal for the formation of the interlocked species. Substitution of the biphenyl-linker in L² for a pyromellitic diimide group gave ligand L³ , which yielded in combination with syn-[ 1 ] the [2]catenane [ 3-IL ](OTf)₄. This assembly exhibits enhanced stability in diluted solution, aided by additional π⋅⋅⋅π stacking interactions. The π⋅⋅⋅π stacking was augmented by the introduction of a pyrene bridge between two NHC donors in ligand L⁴ . Di-NHC precursor H₂- L⁴ (PF₆)₂ reacts with Ag₂O to give the [Ag₂ L⁴ ₂]₂ [2]catenane [ 4-IL ](PF₆)₄, which shows strong π⋅⋅⋅π stacking interactions between the pyrene groups. This assembly was readily converted into the [Au₂ L⁴ ₂]₂ gold species [ 5-IL ](PF₆)₄, which exhibits exceptional stability based on the strong π⋅⋅⋅π stacking interactions and the enhanced stability of the Au-C_NHC bonds.