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’-顺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,~(51)V 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.     

硒钼钒杂多配合物的合成与表征

由钒原子取代杂多阴离子中的钼或钨原子后，形成的多元配合物具有与原来杂多配合物显著不同的催化性质，有关钼钒的同多阴离子，近年报道的有[V2Mo6O26]^6-、[V5Mo8O40]^7-、[V8Mo4O36]^8-等，而三元硒钼钒杂多分配物仅见于[Se2Mo2V6O28]^6-。本文合成了两种硒钼钒三元杂多配合物，并对其进行了表征。     

两个含三唑环有机配体的Hg(Ⅱ)配聚物的合成、晶体结构及其荧光性质（英文）

以碘化汞为原料,分别与3,5-二(4-吡啶基)-1,2,4-三唑(L1),4-氨基-3,5-二(4-吡啶基)-1,2,4-三唑(L2)在N,N-二甲基甲酰胺(DMF)溶液中反应,合成了2个一维链状Hg(Ⅱ)配聚物{[Hg2I4(4-bpt)2]·3DMF}n(1),{[Hg2I4(L2)]·DMF}n(2)。用红外光谱、元素分析、X-射线单晶衍射对配合物进行了表征。X-射线单晶衍射表明,配聚物1中汞离子位于扭曲的配位四面体中心,相邻汞离子通过分别与L1的2个端基N原子配位,桥连形成了一维zig-zag链结构,碘离子占据配位四面体的剩余两配位点,配聚物1的一维链平行于bc平面。配合物2中汞离子位于扭曲的配位四面体中心,分别与L2的一个吡啶N原子和3个碘离子配位,其中2个碘离子充当桥联配体将相邻汞离子连接,形成了一维-Hg-I-Hg-I-的zig-zag链,相邻的-Hg-I-Hg-I-链进一步通过作为双齿配体的L2连接,形成一独特的一维双链梯状聚合物,配聚物2一维链平行于a方向。室温固态荧光测试显示,配聚物1在383.7nm处具有强的荧光发射,而配聚物2在299.7 nm和376.5 nm处具有强的荧光发射。     

基于钒氧多酸与大环铜配合物构筑的三维配位聚合物的合成与表征(英文)

通过[CuL](ClO4)2(L=5,12-二甲基-1,8-二乙醇基-1,3,6,8,10,13-六氮杂环十四烷)与NH4VO3反应,得到一个钒氧多酸桥联大环铜配合物的三维配位聚合物{[CuL][VO3]2·0.67H2O}n。并对其进行了元素分析、红外光谱、紫外光谱、热重和X-射线单晶衍射测定。单晶结构测试结果表明配合物属于三方晶系,R3空间群。在晶体结构中,铜原子与大环配体上的4个氮原子和钒氧四面体[VO4]中的2个氧原子配位,形成畸变的八面体构型。钒氧多酸阴离子[V6O18]6-桥联大环配合物[CuL]2+形成一个具有一维通道的三维配位聚合物。     

新型三维结构亚磷酸钒(Ⅲ)[V2(HPO3)3·(H2O)3]·H2O的水热合成与晶体结构

在具有开放骨架结构的过渡金属磷酸盐微孔材料的合成中，钒磷酸盐因在催化和磁学方面具有潜在的性质和特殊结构特征而引起人们的广泛兴趣．近年来，人们正在尝试用假四面体结构的[HPO3]^2-替代四面体结构的[PO4]^3-，因为{HPO3}结构基元同钒原子的连接方式与{PO4}结构基元和钒原子的连接方式具有明显的差别，     

二个含水杨酰腙配体的钒配合物的合成与晶体结构研究

2种水杨酰腙配体H2L1(H2L1=邻羟基苯乙酮缩水杨酰腙)和H2L2(H2L2=水杨醛缩水杨酰腙)分别与VO(acac)2反应,合成了2个钒配合物[VOL1(C2H5O)]2(1)和[VOL2(i-C3H7O)](2),利用元素分析、红外光谱、紫外光谱和单晶衍射等手段进行表征。配合物1是由酚氧原子桥联2个金属中心形成的具有晶体学中心对称性的双核钒(V)配合物结构,每个V(V)原子具有扭曲的八面体配位构型。配合物2为单核结构,每个V(V)原子具有扭曲的四角锥配位构型,相邻的配合物分子通过分子间氢键作用形成一维超分子链状结构。采用循环伏安法研究了化合物2的电化学性质。     

钒化合物对酸性镀锡溶液的稳定作用

研究了钒化合物稳定剂对酸性SnSO4 溶液稳定性的影响 .可见光谱分析表明稳定剂中主要含有VO2 + 和少量的V3+ ,循环伏安实验显示在 - 0 .2 0～ - 0 .55V(vs .SCE)电位范围内VO2 + 能够在阴极上还原为V3+ ,在更负的电位下V3+ 能进一步还原到V2 + .实验结果说明稳定剂中的低价钒离子有效地清除了镀液中的溶解氧 ,因而防止了Sn2 + 离子的氧化 ,显著地提高了酸性锡镀液的稳定性 .     

离子色谱法测定钒酸根离子的研究

研究了离子色谱测定钒酸根离子的方法。用紫外－可见检测器对钒酸根离子进行了检测,并考察了Ｖ（Ⅴ）－ＰＡＲ显色反应的影响因素,确定了检测钒酸根离子的最佳条件。以此法测定钒酸根离子的检出限为４．０×１０~（－３）ｍｇ／Ｌ,相对标准偏差为１．８％,测定合成水样结果与电感藕合等离子体原子发射光谱分析法（ＩＣＰ－ＡＥＳ）测定结果相比较并进行ｔ和Ｆ检验,无显著性差异。     

库仑滴定法测定钒电池电解液中钒(Ⅲ)与钒(Ⅳ)的含量

钒电池是利用不同价态的钒离子在硫酸电解质溶液中发生氧化还原反应,实现化学能与电能之间的相互转换,从而具有大容量的快速充放电且功率和容量可调节等优点,被相关行业认为是最佳新能源储存介质[1-2]。该电池的容量和充放电效率,与电解液中不同价态的钒离子浓度有关,而该电解液中的钒离子的起始状态通常为钒(Ⅲ,V3+)和钒(Ⅵ,VO2+)混合态,当两种离子浓度的比值为1时,电池比容量达到最大[3-4],因此如何简便、快速且高效的测定V3+和VO2+的含量,对产品的质量控制意义重大。     

Mn2+浓度对钒液流电池正极液的电化学性能影响

电解液中金属离子会影响钒液流电池的电化学性能。本文采用循环伏安法和电化学阻抗谱研究了正极液中Mn2+浓度对V髨/V(Ⅳ)电对的氧化还原过程影响规律,发现Mn2+在正极液中没有发生副反应,但严重影响V髨/V(Ⅳ)的反应活性、电极反应可逆性、离子扩散与电荷转移反应等电化学性能。循环伏安测试结果表明Mn2+浓度为0.04-0.13 g.L-1时,V髨/V(Ⅳ)电对电极反应可逆性和反应活性较高,钒离子扩散系数由参照溶液中的8.89×10-7-1.098×10-6增大至1.302×10-6-1.800×10-6 cm2.s-1,提高了-60%;电化学阻抗测试结果表明Mn2+浓度为0-0.04 g.L-1时,V髨/V(Ⅳ)电对电极反应阻抗和界面阻抗均较参照溶液中的增加不明显,但当Mn2+浓度增至0.07 g.L-1时,上述阻抗值较参照溶液增大了25%-28%。基于二者结果,Mn2+对电极反应有不同程度的负面影响,但是适当的Mn2+浓度有利于钒离子的扩散。     

Vanadium (V) is reduced by the 'as isolated' nitrogenase Fe-protein at neutral pH

Orthovanadate has been investigated in the presence of the nitrogenase Fe-protein. Electron paramagnetic resonance (EPR) spectra demonstrate that vanadium (V) is reduced by the reduced Fe-protein to vanadium (IV) which then probably binds to the nucleotide binding site in place of the Mg2+ which is normally present. In contrast, the oxidized Fe-protein is unable to reduce vanadate. In this case vanadate has potential for use as a phosphate analogue where it acts as transition state mimic for hydrolysis.     

Synthesis,Crystal Structure of Cis—dioxo—catecholatotungsten（VI） Complex and Its NMR Studies on the Interaction with ATP

Cis-dioxo-catecholatotungsten(VI) complex anion[W^(VI)O2-(OC6H4O)2]^2- was obtained with discrete protonated ethylenediamine (NH2CH2CH2NH3)^ cations by the reaction of tetrabutyl ammonium decatungstate with catechol in the mixed solvent of CH3OH,CH3CN and ethylenediamine,and compared with its molybdenum anaogue [Mo^(V) O2(OC6H4O)2]^3- by crystal structure,UV,EPR,The results of the UV and EPR spectra show that tungsten is less redox active than molybdenum since the molybdenum is reduced from Mo(VI) to Mo(V) but tungsten stays in the original highest oxidized state Mo(VI) when they are crystallized from the solution above.It is worthy to note that [W^(VI)O2(OC6H4O)]^2- shows the same coordination structure as its molybdenum analogue in which the metal center exhibits distorted octahedral coordination geometry with two cis-dioxocatecholate ligands and might have the related coordination structure feature with the cofactor of flavoenzyme because [Mo^(V)O2(OC6H4O)2]^3- presented essentially the same EPR spectra as flavoenzyme.The NMR studies on the interaction of the title complex with ATP reveal that the reduction of W(VI) to W(V) occurs when the title complex is dissolved in D2O and the W(V) is oxidized again when ATP solution is mixed with original solution and the hydrolysis of the catecholato ligand take places at mean time being monitored by ^1H NMR and ^13C NMR spectra.     

Asymmetric aerobic oxidation of alpha-hydroxy acid derivatives by C4-symmetric, vanadate-centered, tetrakisvanadyl(V) clusters derived from N-salicylidene-alpha-aminocarboxylates

A series of chiral vanadyl(V) methoxides bearing 3-t-butyl-5-substituted N-salicylene-L-valinate and L-t-leucinate as chiral auxiliaries has been prepared. In all cases except the 3,5-di-t-butyl analogue, they exist as monomers both in solution and in the single crystal state. In the case of the 3,5-di-t-butyl analogue, the architectural nature of the vanadyl(V) complex highly depends on the base used during the complex formation event. A pentanuclear C4-symmetric complex was formed when potassium salts were employed instead of the corresponding sodium salts. A central vanadate(V) unit serves to grip four identical chiral monomeric vanadyl(V) units together, by which a potassium ion sits on top of the four flanking units through carbonyl coordinations and serves to hold the whole cluster by cooperation with the central vanadate(V) unit. In comparison with the corresponding monomeric vanadyl(V) methoxide complex, the cluster complex was utilized to facilitate the asymmetric aerobic oxidations of various racemic alpha-hydroxyesters, -amides, and -thioesters with excellent selectivity factors (krel 40 to >500).     

^1H弛豫研究具有表面活性的探针: 2-氯-N-十二烷基吡啶盐碘化 物(CDPI)在不 同集合体内的动态行为

本文报道具有表面活性的探针---2-氯-N-十二烷基吡啶盐碘化物(CDPI)的疏水碳氢链在几种包结体(胶束、包结在环糊精(β-CD)中以及包结在甲基直链淀粉(MA))中的^1H核磁弛豫时间。通过比较CDPI中碳氢链的CH~3、(CH~2)~9的T~1及T~1(CH~3)/T~1(CH~2)~9的变化,发现CDPI的运动自由度按下列次序降低:游离态、包结在β-CD中、胶束状态、包结在MA中,顺磁离子Mn^2^+对CDPI内各种质子的T~1的影响随其所处之包结体不同而变化。在胶束和甲基直链淀粉体系中,烷链的T~1几乎均不受Mn^2^+的影响,说明水合Mn^2^+不能进入CDPI胶束或甲基直链淀粉的螺旋内穴。     

Formation and structure of 1:1 complexes between aryl hydroxamic acids and vanadate at neutral pH

Although aryl hydroxamic acids are well-known to form coordination complexes with vanadate (V(V)), the nature of these complexes at neutral pH and submillimolar concentrations, the conditions under which such complexes inhibit various serine amidohydrolases, is not well established. A series of qualitative and quantitative experiments, involving UV/vis, (1)H NMR, and (51)V NMR spectroscopies, established that both 1:1 and 1:2 vanadate/hydroxamate complexes form at pH 7.5, with the former dominating at submillimolar concentrations. Formation constants for the complexes of several aryl and alkyl hydroxamic acids were determined; for example, for benzohydroxamic acid, the stepwise formation constants of the 1:1 and 1:2 complexes were 3000 and 400 M(-1), respectively. The (51)V chemical shift of the 1:1 4-nitrobenzohydroxamic acid complex was -497 ppm, and that of its unsubstituted analogue was -498 ppm. A (1)H-(15)N HSQC spectrum of the 4-nitrobenzo-(15)N-hydroxamic acid/vanadate complex indicated the presence of an N-H group with (15)N and (1)H chemical shifts of 115 and 5.83 ppm, respectively. A (13)C NMR spectrum of the complex of 4-nitrobenzo-(13)C-hydroxamic acid with vanadate displayed a resonance at 170.1 ppm and thus a coordination-induced shift (CIS) of +3.8 ppm. In contrast, the CIS value of an established 1:2 complex, thought to contain chelated hydroxamic acid ligands, was +11.9 ppm. These spectral data led to the following structural picture of 1:1 complexes of vanadate and aryl hydroxamic acids. They contain penta- or hexa-coordinated vanadium. The ligand is in the hydroxamate rather than hydroximate form. The ligand is presumably bound to vanadium through the hydroxamic hydroxyl oxygen, but the hydroxamic acid carbonyl oxygen interacts weakly with vanadium. These species are the most likely candidates for the inhibitors of serine amidohydrolases found in vanadate/hydroxamic acid mixtures.     

NMR, CD and MCD studies of vanadate-nucleoside complexes

Complex formation between tetraoxovanadate(V) and each of the nucleosides adenosine, guanosine, cytidine and uridine has been studied in a constant salt medium at pH 7. 13C- and 51V NMR studies show that only complexes with the formula V2L2 (V = vanadate, L = nucleoside) are formed, and their formation constants have been determined. They have 51V NMR resonances around -523 ppm relative to VOCl3 and they exhibit no CD in the spectral region of the charge-transfer transitions. MCD spectra were also measured, and all experiments are in accord with a molecular structure composed by two edge-sharing VO6 octahedra forming an O4V(mu-O)2VO4 skeleton with each of the nucleoside ligands bridging the two vanadium centres through the ribose 2',3'-oxygens, which are the oxygens outside the V2O6 plane. Admixture of imidazole-HCl buffer at pH 7 gives rise to additional complexes of 1:1 stoichiometry. They have been characterized by 51V NMR and CD, and their formation constants are reported. Vanadate(V) and the deoxynucleosides deoxyadenosine, deoxyguanosine, deoxycytidine and thymidine form very weak complexes which cannot be detected by 51V NMR or CD under conditions for which vanadate and the nucleosides form complexes.     

Simple oxovanadates as multiparameter probes of reverse micelles

Using a wide range of different methods, researchers have found that the environment inside reverse micelles differs from bulk aqueous solution in many ways. Here, we present a new tool, a series of aqueous oxovanadium(V) reactions, to probe pH, viscosity, and ionic strength in the aqueous interior of reverse micelles. In addition to their potential as anionic probe analogues to phosphates, simple oxovanadium(V) compounds have equilibrium characteristics in aqueous media exquisitely sensitive to their environment. Therefore, the speciation of vanadate equilibria can be used as a parameter to characterize the intramicellar medium. Vanadate speciation is monitored through 51V NMR spectroscopy, which also yields information through chemical shifts and linewidths of spectral features. The speciation observed suggests that the relative acidity of a basic vanadate stock solution is slightly reduced in large, w0 >or= 12, reverse micelles, but that for smaller reverse micelles, speciation reflects the strong interaction of these negatively charged oxometalates with the reverse micelle and suggest an increased solution viscosity in the reverse micelles. This interpretation is obtained through different responses closely linked to the reverse micellar size and the specific conditions in the stock solutions used to form reverse micelles.     

4-(4-羧基苯氧基)间苯二甲酸构筑的过渡金属配位聚合物: 合成、 晶体结构、 荧光传感与光催化

采用水热法合成了4个配位聚合物[Zn(Hcpoia)(2,2'-bpy)·H₂O]_n(1)和[M(Hcpoia)(phen)]_n·nH₂O[M=Zn(2), Mn(3), Co(4); H₃cpoia=4-(4-羧基苯氧基)间苯二甲酸; 2,2'-bpy=2,2'-联吡啶; phen=1,10-邻菲罗啉], 利用X射线单晶衍射分析确定了配合物的晶体结构. 配合物1为一维链状结构, 中心Zn ²⁺离子的配位环境为[ZnO₄N₂]扭曲的八面体构型, 配体Hcpoia ^2-以μ₁∶η ¹η ⁰和μ₁∶η ¹η ¹配位模式桥连相邻的Zn ²⁺离子. 配合物2和4的结构与配合物1类似, 是由配体Hcpoia ^2-以μ₁∶η ¹η ⁰和μ₁∶η ¹η ¹配位模式联接[MO₄N₂]结构单元而形成的一维链状结构. 配合物1, 2和4中均存在分子间氢键(O—H…O), 氢键的存在使一维链连接形成二维超分子结构. 配合物3为二维网状结构, Mn ²⁺离子的配位环境为[MnO₄N₂]扭曲的八面体构型, 配体Hcpoia ^2-以μ₂∶η ¹η ¹配位模式桥连相邻Mn ²⁺离子形成[Mn₂COO₂]结构单元, 该结构单元被Hcpoia ^2-连接形成二维结构. 在4个配合物中, 2,2'-bpy和phen配体均以端基的形式与金属离子螯合配位. 研究了水溶液中抗生素分子和Fe ³⁺离子对配合物1与荧光强度的影响, 实验结果表明, 甲硝唑、 Fe ³⁺离子对配合物1有荧光猝灭作用, 并进一步考察了甲硝唑浓度和Fe ³⁺离子浓度对配合物1荧光强度的影响. 基于荧光猝灭机理, 配合物1可以用作荧光传感器检测水溶液中的甲硝唑和Fe ³⁺离子. 研究了配合物4对罗丹明B(RhB)的催化降解性能, 发现在氙灯照射和H₂O₂存在条件下, 配合物4对RhB具有较好的光催化降解作用.     

NMR investigation of the interaction of vanadate with carbasilatranes in aqueous solutions

Reaction of vanadate with carbasilatranes [methoxy{N,N',N' '-2,2',3-[bis(1-methylethanolato)(propyl)]amino}silane (1), methoxy{N,N',N' '-2,2',3-[bis(1-ethanolethanolato)(propyl)]amino}silane (2), and {N,N',N' '-2,2',2-[bis(ethanolato)(glycolpropyl ether)]amino}silane (3)] in aqueous solution results in the formation of vanadosilicates and five-coordinated chelate vanadium(V) complexes as evidenced by 51V, 1H, and 13C NMR spectroscopy. Chiral carbasilatrane S,S-1 was characterized in the solid state by X-ray diffraction, revealing a trigonal bipyramidal geometry around the metal ion, with one unidentate methoxy group and one atrane nitrogen atom at the axial positions and one carbon and two atrane oxygen atoms at the equatorial plane of the bipyramid. Crystal data (Mo Kalpha; 100(2) K) are as follows: orthorhombic space group P2(1)2(1)2(1); a = 8.8751(6), b = 9.7031(7), c = 14.2263(12) A; Z = 4. The complexation of vanadium either with 1 or 2 is stereoselective yielding approximately 94% of the complex containing ligand in the S,R-configuration. The lower ability of the S,S- and R,R-diastereoisomers of 1 and 2 to ligate vanadate was attributed to stereochemical factors, dictating a square pyramidal geometry for the chelated complexes. A dynamic process between the vanadium chelate complexes and the respective carbasilatranes was evaluated by 2D {1H} EXSY NMR spectroscopy. These spectra show that the vanadate complexes with the open carbasilatranes exchange more slowly with the free ligand compared to the respective alcohol aminate complexes.     

The role of the Mg2+ cation in ATPsynthase studied by electron paramagnetic resonance using VO2+ and Mn2+ paramagnetic probes

The electron paramagnetic resonance (EPR), electron spin echo envelope modulation (ESEEM) and hyperfine sublevel correlation (HYSCORE) spectra of Mg2+-depleted chloroplast F1-ATPase substituted with stoichiometric VO2+ are reported. The ESEEM and HYSCORE spectra of the complex are dominated by the hyperfine and quadrupole interactions between the VO2+ paramagnet and two different nitrogen ligands with isotropic hyperfine couplings /A1/ = 4.11 MHz and /A2/ = 6.46 MHz and nuclear quadrupole couplings e2qQ1 approximately 3.89-4.49 MHz and e2qQ2 approximately 1.91-2.20 MHz, respectively. Aminoacid functional groups compatible with these magnetic couplings include a histidine imidazole, the epsilon-NH2 of a lysine residue, and the guanidinium group of an arginine. Consistent with this interpretation, very characteristic correlations are detected in the HYSCORE spectra between the 14N deltaM1 = 2 transitions in the negative quadrant, and also between some of the deltaM1 = 1 transitions in the positive quadrant. The interaction of the substrate and product ADP and ATP nucleotides with the enzyme has been studied in protein complexes where Mg2+ is substituted for Mn2+. Stoichiometric complexes of Mn x ADP and Mn x ATP with the whole enzyme show distinct and specific hyperfine couplings with the 31P atoms of the bonding phosphates in the HYSCORE (ADP, A(31Pbeta) = 5.20 MHz: ATP, A(31Pbeta) = 4.60 MHz and A(31Pgamma) = 5.90 MHz) demonstrating the role of the enzyme active site in positioning the di- or triphosphate chain of the nucleotide for efficient catalysis. When the complexes are formed with the isolated alpha or beta subunits of the enzyme, the HYSCORE spectra are substantially modified, suggesting that in these cases the nucleotide binding site is only partially structured.