钒酸根、金属离子和腺苷二磷酸的相互作用-ATP及Mg^2^+-ATP类似物的形成

用钒-51核磁共振方法研究钒酸根在不同浓度和离子强度下, 在生理pH水溶液中的物种分配。研究结果表明毫摩尔级浓度的钒酸根主要以中心钒原子为四面体构型的单体、二聚、四聚和五聚体存在。通过比较所得的平衡常数说明在离子强度降低时, 钒酸根的聚合度下降。对于钒酸根-ADP体系, 从所显示的核磁谱变化通过计算得到相应的结合平衡常数, 说明主要发生的反应一是形成ATP类似物ADPV(V代表四面体构型的单体钒酸根); 二是在ADP浓度相对高时, 钒酸根与ADP核糖基上2', 3'-颗位羟基同时作用形成2:2配比的、钒原子为五配位三角双锥构型的配合物。在钒酸根-ADP体系中加入Mn^2^+后, ^5^1V NMR的变化说明ATP的类似物ADPV中β-磷酸根和γ-钒酸根可以协同螯合Mn^2^+, 表明形成了Mg^2^+-ATP的类似物Mn^2^+-ADPV。     

Chiral self-dimerization of vanadium complexes on a SiO2 surface for asymmetric catalytic coupling of 2-naphthol: structure, performance, and mechanism

Vanadium monomers with chiral tridentate Schiff-base ligands were supported on SiO(2) through a chemical reaction with surface silanols, where we found a new chirality creation by the self-dimerization of the vanadyl complexes on the surface. The chiral self-dimerization and the role of surface silanols in the self-assembly were investigated by means of X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), diffuse-reflectance ultraviolet/visible (DR-UV/VIS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), electron spin resonance (ESR), and density functional theory (DFT) calculations. The surface vanadyl complexes had a distorted square-pyramidal conformation with a V=O bond. FT-IR spectra revealed that the Ph-O moiety of Schiff-base ligands was converted to Ph-OH by a surface-concerted reaction between the vanadium precursors and surface SiOH groups. The Ph-OH in an attached vanadyl complex interacted with a COO moiety of another vanadyl complex by hydrogen bonding to form a self-dimerized structure at the surface. The interatomic distance of V-V in the surface self-assembly was evaluated to be 0.40 +/- 0.05 nm by ESR after O(2) adsorption. The self-dimerized V structure on SiO(2) was modeled by DFT calculations, which demonstrated that two vanadium monomers with Ph-OH linked together by two hydrogen bonds and their V=O groups were directed opposite to each other. The surface self-dimerization of the vanadium precursors fixes the direction of the V=O bond and the plane of the Schiff-base ligand. Thus, a new chiral reaction field was created by two types of chirality: the chiral Schiff-base ligand and the chiral V center. We have also found that the chiral self-dimerized vanadyl complexes exhibit remarkable catalytic performance for the asymmetric oxidative coupling of 2-naphthol: 96% conversion, 100% selectivity to 1,1'-binaphthol (BINOL), and 90% enantiomeric excess (ee). Increasing the vanadium loading on SiO(2) caused a dramatic swell of enantioselectivity, and the maximum 90% ee was observed on the supported catalyst with the full coverage of the vanadyl complex (3.4 wt % vanadium). This value is equivalent to the maximum ee reported in homogeneous catalysis for the coupling reaction. Furthermore, the supported vanadium dimers were reusable without loss of the catalytic performance. To our knowledge, this is the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol.     

Novel stereochemistry, reactivity, and stability of an arsenic heterocycle in a metal-promoted asymmetric cycloaddition reaction

The organopalladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]phenylene as the chiral auxiliary has been used as the chiral template to promote the asymmetric cycloaddition reaction between diphenylvinylphosphine and 3,4-dimethyl-1-phenylarsole. A diphenylphosphino-substituted asymmetrical heterobidentate arsanorbornene (As-P) ligand was obtained stereoselectively on the chiral palladium template in moderate yield. The chiral benzylamine auxiliary could be removed chemoselectively from the template by treatment with HCl to produce the neutral complex [(As-P)PdCl2]. In contrast to their reported P-P analogue, the arsenic donor in the dichloro complex could be eliminated stereospecifically under mild reaction conditions to generate the corresponding 1-(diphenylphosphino)-3,4-dimethyl-2,4-cyclohexadiene, which remained as a bidentate ligand at the PdCl2 unit via phosphorus and the eta2-C4-C5 double bond. The arsenic-elimination process was found to be influenced by the halo ligand in [(As-P)PdX2]. A similar process was observed with the analogous dibromo complex, but the corresponding diiodo species did not show similar reactivity. All of the novel As-Pd complexes have been characterized by X-ray crystallography.     

Highly enantioselective aerobic oxidation of alpha-hydroxyphosphonates catalyzed by chiral vanadyl(V) methoxides bearing N-salicylidene-alpha-aminocarboxylates

An unprecedented vanadyl(V) methoxide complex 4 derived from 3,5-dibromo-N-salicylidene-l-tert-leucinate enables highly enantioselective aerobic oxidations of alpha-hydroxyphosphonates at ambient temperature with selectivity factors ranging from 3 to >99.     

Raman spectroscopic study of pascoite Ca3V10O(28)·17H2O

Raman spectroscopy has been used to study the molecular structure of the vanadate mineral pascoite. Pascoite, rauvite and huemulite are examples of simple salts involving the decavanadate anion (V10O28)6-. Decavanadate consists of four distinct VO6 units which are reflected in Raman bands occurring at higher wavenumbers. The Raman spectrum of pascoite is characterised by two intense bands at 991 and 965 cm(-1). Raman bands are observed at 991, 965, 958 and 905 cm(-1) and originate from four distinct VO6 sites in the mineral structure. In the infrared spectra of pascoite, two wavenumber regions are observed between: (1) 837 and 860, and (2) between 803 and 833 cm(-1). These bands are assigned to ν3 antisymmetric stretching modes of (V10O28)6- or (V5O14)3- units. The spectrum is highly complex in the lower wavenumber region, and therefore the assignment of bands is difficult. Bands observed in the 404 to 458 cm(-1) region are assigned to the ν2 bending modes of (V10O28)6- or (V5O14)3- units. Raman bands observed in the 530-620 cm(-1) region are assigned to the ν4 bending modes of (V10O28)6- or (V5O14)3- units. The Raman spectra of the vanadates in the low wavenumber region are complex with multiple overlapping bands which are probably due to VO subunits and MO bonds.     

A DFT study on the hydrated V2O5-TiO2-anatase catalyst: stability of monomeric species

A combined cluster and periodic study has been carried out to elucidate the stability of hydrated species on the vanadia/titania catalyst. First, the hydration of a V₂O₅ cluster was analyzed for the successive adsorption of one to four water molecules. The dimeric skeleton is found to be preserved at a low water concentration. However, after the adsorption of four water molecules on the dimer, it is found to break to generate stable monomeric OV(OH)₃ units. The two moieties are related by the equation: Such OV(OH)₃ units have been taken as a monomer model for the periodic representation of the vanadia/titania catalyst. On the (100) surface, the OV(OH)₃ moieties are anchored by three V–O–Ti bonds to the support surface in a pyramidal arrangement. The vanadyl V=O bond is found to be very stable.     

Catalytic asymmetric coupling of 2-naphthols by chiral tridentate oxovanadium (IV) complexes

A series of chiral oxovanadium(IV) complexes derived from tridentate N-3,5-substituted and N-3,4-benzo- and N-5,6-benzo-salicylidene-alpha-amino acids can serve as efficient catalysts for the enantioselective oxidative couplings of various 3-, 6-, and 7-substituted 2-naphthols under O(2). The best scenario involves the use of a vanadyl complex arising from 2-hydroxy-1-naphthaldehyde and valine (or phenylalanine) in CCl(4), leading to BINOLs in good yields (75-100%) and with enantioselectivities of up to 68%.     

Catalytic Asymmetric Coupling of 2-Naphthols by Chiral Tridentate Oxovanadium(IV) Complexes

A series of chiral oxovanadium(IV) complexes derived from tridentate N-3,5-substituted-, N-3,4-benzo-and N-5,6-benzo-salicylidene-α-amino acids can serve as efficient catalysts for the enantioselective oxidative couplings of various 3-, 6-, and 7-substituted 2-naphthols under O2. The best scenario involves the use of a vanadyl complex arising from 2-hydroxy-l-naphthaldehyde and valine (or phenylalanine) in CCl4, leading to BINOLs in good yields (75-100%) and with enantioselectivities of up to 68%.     

Synthesis and fluorescence emission of neutral and anionic di- and tetra-carboranyl compounds

A new family of photoluminescent neutral and anionic di-carboranyl and tetra-carboranyl derivatives have been synthesized and characterized. The reaction of α,α'-bis(3,5-bis(bromomethyl)phenoxy-m-xylene with 4 equiv. of the monolithium salt of 1-Ph-1,2-C(2)B(10)H(11) or 1-Me-1,2-C(2)B(10)H(11) gives the neutral tetracarboranyl-functionalized aryl ether derivatives closo-1 and closo-2, respectively. The addition of the monolithium salt of 1-Ph-1,2-closo-C(2)B(10)H(11) to α,α,'-dibromo-m-xylene or 2,6-dibromomethyl-pyridine gives the corresponding di-carboranyl derivatives closo-3 and closo-4. These compounds, which contain four or two closo clusters, were degraded using the classical method, KOH in EtOH, affording the corresponding nido species, which were isolated as potassium or tetramethylammonium salts. All the compounds were characterized by IR, (1)H, (11)B and (13)C NMR spectroscopy, and the crystal structure of closo-3 was analysed by X-ray diffraction. The carboranyl fragments are bonded through CH(2) units to different organic moieties, and their influence on the photoluminescent properties of the final molecules has been studied. All the closo- and nido-carborane derivatives exhibit a blue emission under ultraviolet excitation at room temperature in different solvents. The fluorescence properties of these closo and nido-derivatives depend on the substituent (Ph or Me) bonded to the C(cluster), the solvent polarity, and the organic unit bearing the carborane clusters (benzene or pyridine). In the case of nido-derivatives, an important effect of the cation is also observed.     

From platonic templates to Archimedean solids: successive construction of nanoscopic {V16As8}, {V16As10}, {V20As8}, and {V24As8} polyoxovanadate cages

Supramolecular coordination cages provide unique restricted inner cavities that can be exploited for molecular recognition purposes and catalysis. Their syntheses often involve complex self-organization processes and rely on the identification of preorganized, kinetically stable building units that provide ligand-accessible coordination sites. Here we report a highly effective protocol for the successive buildup of symmetrical nanoscopic polyoxometalate (POM) cages. Our methodology takes advantage of a supramolecular templating effect and utilizes the structure-directing influence of octahedral {X(x)(H(2)O)(6-x)} (X = Br(-), Cl(-); x = 2, 4, 6) assemblies that reside inside the hollow cluster shells and determine the arrangement of di- and tetranuclear vanadate units. The approach allows the preparation of a series of high-nuclearity POM cages that are characterized by {V(16)As(8)}, {V(16)As(10)}, {V(20)As(8)}, and {V(24)As(8)} core structures. In the latter cluster cage, the vanadium centers adopt a truncated octahedral topology. The formation of this Archimedean body is the direct result of the assembly of six square {V(4)O(8)} units that cap the vertices of the encapsulated Platonic {Cl(6)} octahedron. To the best of our knowledge, this {V(24)As(8)} cage is the largest hybrid vanadate cluster reported to date.     

Vanadium(IV) Complexes with Mixed O,S Donor Ligands. Syntheses, Structures, and Properties of the Anions Tris(2-mercapto-4-methylphenolato)vanadate(IV) and Bis(2-mercaptophenolato)oxovanadate(IV)

Reaction of VO(acac)(2) with 2-mercaptophenol (mpH(2)) in the presence of triethylamine gives the mononuclear tris complex (Et(3)NH)(2)[V(mp)(3)] (1), in which the vanadyl oxygen has been displaced. An analogous reaction using 2-mercapto-4-methylphenol (mmpH(2)) afforded (Et(3)NH)(PNP)[V(mmp)(3)] (2), which was structurally characterized. 2 crystallizes in the orthorhombic space group Pna2(1 )with unit cell parameters (at -163 degrees C) a = 23.974(7) ?, b = 9.569(4) ?, c = 25.101(6) ?, and Z = 4. The coordination geometry around the vanadium is between octahedral and trigonal prismatic. Reaction of VO(acac)(2 )with the sodium salt of 2-mercaptophenol produces the vanadyl(IV) complex Na(Ph(4)P)[VO(mp)(2)].Et(2)O (3), which crystallizes in the triclinic space group P&onemacr; with unit cell parameters (at -135 degrees C) a = 12.185(4) ?, b = 12.658(4) ?, c = 14.244(4) ?, alpha = 103.19(2) degrees, beta = 100.84(2) degrees, and gamma = 114.17(2) degrees. The unit cell of 3 contains a pair of symmetry-related [VO(mp)(2)](2)(-) units bridged through vanadyl and ligand oxygen atoms by a pair of sodium ions, in addition to two PPh(4)(+) ions. The coordination geometry around the vanadium is square pyramidal, with a V=O bond length of 1.611(5) ?. 1, 2, and 3 are characterized by IR and UV-vis spectroscopies, magnetic susceptibility, EPR spectroscopy, and cyclic voltammetry. 1 and 2 can be oxidized by I(2, )Cp(2)Fe(+), or O(2) to [V(mp)(3)](-) and [V(mmp)(3)](-), respectively, which in turn can be reduced back to the dianions by oxalate ion. These reversible redox processes can be followed by UV-vis spectroscopy.     

Spontaneous resolution of chiral polyoxometalate-based compounds consisting of 3D chiral inorganic skeletons assembled from different helical units

Four enantiomerically pure 3D chiral POM-based compounds, [Ni(2)(bbi)(2)(H(2)O)(4)V(4)O(12)]2 H(2)O (1 a and 1 b) and [Co(bbi)(H(2)O)V(2)O(6)] (2 a and 2 b) (bbi=1,1'-(1,4-butanediyl)bisimidazole) based on the achiral ligand, different vanadate chains, and different metal centers have been synthesized by hydrothermal methods. Single-crystal X-ray diffraction analyses revealed that 1 a and 1 b, and 2 a and 2 b, respectively, are enantiomers. In 1 a and 1 b two kinds of vanadate chains with different screw axes link Ni cations to generate 3D chiral inorganic skeletons, which are connected by the achiral bbi ligands to form complicated 3D 3,4-connected chiral self-penetrating frameworks with (7(2)8)(7(2)8(2)9(2))(7(3)8(2)10) topology. They represent the first examples of chiral self-penetrating frameworks known for polyoxometalate (POM) systems. Contrary to 1 a and 1 b, in 2 a and 2 b the vanadate chains link Co(II) cations to generate 3D chiral inorganic skeletons, which are assembled from two kinds of heterometallic helical units of opposite chirality along the c axes. The chiral inorganic skeletons are connected by bbi to form 3D 3,4-connected chiral POM-based frameworks with (6(2)8)(2)(6(2)8(2)10(2)) topology. It is believed that the asymmetrical coordination modes of the metal cations in 1 a-2 b generate the initial chiral centers, and that the formation of the various helical units and the hydrogen bond interactions are responsible for preservation of the chirality and spontaneous resolution when the chirality is extended into the homochiral 3D-networks. This is the first known report of chiral POM-based compounds consisting of 3D chiral inorganic skeletons being obtained by spontaneous resolution upon crystallization in the absence of any chiral source, which may provide a rational strategy for synthesis of chiral POM-based compounds by using achiral ligands and POM helical units.     

CDMPC手性固定相对新型金属簇化合物的手性拆分

应用纤维素三（3,5-二甲基苯基氨基甲酸酯）（cellulose tris (3, 5- dimethylphenylcarbamate,CDMPC）手性固定相对两种新型金属簇合物进行了拆分,通过流动相组成、流速和样品溶剂等条件对拆分影响的考察进行了拆分条件的优化。实验结果表明,簇合物1和簇合物2分别在含乙醇V(hexane)∶V(ethanol)=95∶5)和异丙醇(V(hexane)∶V(2-propanol)=90∶10)的流动相中得到了较好的拆分,将样品溶解在和流动相组成相近的溶剂中更利于簇合物拆分,簇合物配体结构对簇合物在固定相上的保留和拆分有重要的影响。 在优化条件下,2种金属簇合物分离度均达到1.5以上。     

CDMPC手性固定相对金属簇化合物的手性拆分

应用纤维素三(3,5-二甲基苯基氨基甲酸酯)(CDMPC)手性固定相对2种羰基钌金属簇合物进行了拆分,通过流动相组成、流速和样品溶剂等条件对拆分影响的考察对拆分条件进行了优化。实验结果表明,簇合物1和簇合物2分别在含乙醇(V(hexane):V(ethanol)=95:5)和异丙醇(V(hexane):V(2-propanol)=90:10)的流动相中得到了较好的拆分,将样品溶解在和流动相组成相近的溶剂中更利于簇合物拆分,簇合物配体结构对簇合物在固定相上的保留和拆分有重要的影响。在优化条件下,2种金属簇合物分离度均达到1.5以上。     

Low-valent gallium, indium, and tin compounds that contain a highly fluorinated tris(pyrazolyl)borate ligand: syntheses and characterization of

Syntheses and characterization of gallium(I), indium(I), and tin(II) complexes of the [HB(3,5-(CF3)2Pz)3]- ligand (where [HB(3,5-(CF3)2Pz)3]- = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate)) are reported. X-ray crystal structures of [HB(3,5-(CF3)2Pz)3]In and [HB(3,5-(CF3)2Pz)3]Sn(CF3SO3) show monomeric structures in the solid state. The In-N and Sn-N bond distances are longer than the corresponding bond distances of nonfluorinated analogues. NMR data of the gallium(I) adduct [HB(3,5-(CF3)2Pz)3]Ga are very similar to those of the indium(I) analogue suggesting similar solution structures.     

Alkali salts of C3-symmetric,linked aryloxides: selective binding of substrates with metal aggregates

The lithium, sodium, and potassium salts of tris(3,5-dialkyl-2-hydroxyphenyl)methanes (tert-butyl, tert-pentyl, methyl) have been prepared by reaction of the triarylmethane with n-butyllithium, sodium hydride, and potassium hydride, respectively. These compounds are all hexanuclear aggregates composed of two triarylmethane units. Whereas the lithium salt is compact and cannot bind oxygen-donor solvent molecules, the sodium and potassium systems have vacant coordination sites that can interact with solvents. For the sodium compounds, the solvent can be subsequently removed, and the resulting coordinatively unsaturated compounds have been shown to selectively bind oxygen-donor substrates (ethers, aldehydes, and ketones) of suitable size and shape. The paper reports the synthesis and characterization of these novel compounds, including thirteen crystal structures of the salts and their adducts.     

Antiferromagnetic porous metal-organic framework containing mixed-valence [Mn(II)4Mn(III)2(μ4-O)2]10+ units with catecholase activity and selective gas adsorption

A multifunctional porous metal organic framework based on mixed-valence hexa-nuclear [Mn(III)(2)Mn(II)(4)O(2)(pyz)(2)(C(6)H(5)CH(2)COO)(10)] (pyz = pyrazine) units has been synthesized. The complex has been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction analysis, and variable-temperature magnetic measurements. The structural analysis reveals that the bidentate pyz molecules connect each [Mn(6)] unit to its four [Mn(6)] neighbors through the peripheral Mn(II) centers, giving rise to a three-dimensional (3D) distorted diamond-like porous framework. Variable-temperature (2-300 K) magnetic susceptibility measurements show the presence of dominant antiferromagnetic interactions within the discrete [Mn(6)] cluster that have been fitted with a model containing three exchange constants developed for the complex (J(1) = -8.6 cm(-1), J(2) = -3.9 cm(-1), and J(3) = -100.0 cm(-1)). Using 3,5-di-tert-butyl catechol (3,5-DTBC) as the substrate, catecholase activity of the complex has been studied; the turn over number is determined to be of 2547 h(-1) in acetonitrile. This porous compound shows remarkable selectivity for adsorption of CO(2) over N(2) that may be correlated with the effect of window flexibility of the pore to the corresponding adsorbate molecules.     

Synthesis,Structural Characterization,and Reductive Cleavage of an Oxygen-Containing Naphthyl Macrocycle

A small macrocycle comprising ether-bridged naphthyl units was prepared in a two-step synthesis. Single-crystal X-ray diffraction of two polymorphs are reported, one of which showed multiple C−H⋅⋅⋅π_naphthyl interactions of a solvent molecule in the cavity of the macrocycle. Chemical reduction led to C−O bond cleavages accompanied by a Z/E isomerization. The resulting twofold negatively charged (E)-1,2-bis(2-naphthyl)ethylene fragment was isolated as its potassium salts. Electronic characterization revealed a singlet ground state, and a marked distortion of the central ethylene unit was observed upon electron uptake.     

手性双核Salen配合物的谱学性质

合成了四个新型的手性双核(R,R)Salen配合物[(Cu)2L•H2O(2), (Ni)2L(3), (Zn)2L•H2O(4), (MnCl)2L•2H2O(5)], (其中L是由(R,R)环己二胺、 3,5-叔丁基水杨醛、 5,5’-亚甲基二水杨醛为原料合成的手性二聚Salen配体(1)).用元素分析、NMR、FT-IR、UV-Vis、CD光谱对配体和配合物进行了表征.在与单核的Salen配体和配合物比较的基础上，详细讨论了红外光谱、电子吸收光谱、圆二色光谱性质.发现双核配体和配合物的电子吸收光谱吸收峰的位置和形状与单核的配体和配合物基本一致，而吸收峰的强度有近似两倍的关系.另外， 用激子偶合理论解释了此类手性化合物圆二色谱的Cotton效应和Cotton分裂. Cotton分裂的方向依赖于环己二胺的构象.(R,R)环己二胺决定了Salen化合物的手征性为负， Cotton分裂的正负两部分分别处于高能区和低能区.     

Synthesis and complexing properties of a chiral macrocyclic molecular receptor with convergent binding sites

Two novel hosts: 15-crown-5 and N-benzyl-aza-15-crown-5 incorporating a boron-containing D-mannopyranosidic unit form more stable cascade complexes with (S)-amino acid sodium or potassium salts than with the respective (R)-enantiomers. Complexes with sodium salts are more stable than the corresponding complexes with potassium salts as revealed by variable-temperature NMR measurements. Strong non-bonded interaction between the sugar unit and the -substituents of the amino acids results in enantiomeric differentiation and destabilization of the complex. Complex formation is interpreted in terms of ion-pair inclusion by macrocyclic ring and nitrogen-boron interaction.