Unusual ion UO4? formed upon collision induced dissociation of [UO2(NO3)3]?, [UO2(ClO4)3]?, [UO2(CH3COO)3]? ions

The following ions [UO₂(NO₃)₃]⁻, [UO₂(ClO₄)₃]⁻, [UO₂(CH₃COO)₃]⁻ were generated from respective salts (UO₂(NO₃)₂, UO₂(ClO₄)₃, UO₂(CH3COO)2) by laser desorption/ionization (LDI). Collision induced dissociation of the ions has led, among others, to the formation of UO₄ ⁻ ion (m/z 302). The undertaken quantum mechanical calculations showed this ion is most likely to possess square planar geometry as suggested by MP2 results or strongly deformed geometry in between tetrahedral and square planar as indicated by DFT results. Interestingly, geometrical parameters and analysis of electron density suggest it is an U^VI compound, in which oxygen atoms bear unpaired electron and negative charge.     

Stable radical adducts of diisopropylphosphoryl radicals with fullerene complexes (η2-C60)Os(CO)(PPh3)2(CNBut) and (η2-C70)Os(CO)(PPh3)2(CNBut)

It was determined by ESR spectroscopy that the UV irradiation of toluene solutions containing Hg[P(O)(OPrⁱ)₂ and the complex (²-C₆₀)Os(CO)(PPh₃)₂(CNBu^t) produces six stable regioisomeric adducts of phosphoryl radicals with complexes, which are not demetallated under UV irradiation and do not dimerize in the absence of UV irradiation. This is caused by the addition of the phosphoryl radicals to the carbon atoms of fullerene localized near the metal-containing moiety. The addition of the phosphoryl radicals to (²-C₇₀)Os(CO)(PPh₃)₂(CNBu^t) gives rise to the formation of nine stable regioisomeric radical adducts. A comparison of the composition of regioisomers of the radical adducts of C₇₀ with the phosphoryl radicals, which were formed directly from C₇₀ and from the radical adducts of ²-C₇₀)Os(CO)(PPh₃)₂(CNBu^t) by the demetallation of the latter, revealed an orienting effect of the osmium-containing moiety on the addition of the phosphoryl radicals to the fullerene complex.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1968–1972, September, 2004.     

X@(HAlNH)12和X(HAlNH)12 (X＝F－, Cl－, Br－, O2－, S2－, Se2－)复合物的结构和稳定性

用DFT的B3LYP方法在6-31G(d)基组的水平上, 对闭式多面体簇合物(HAlNH)₁₂及其内含式X@(HAlNH)₁₂和外接式X(HAlNH)₁₂ (X＝F^－, Cl^－, Br^－, O^2－, S^2－, Se^2－)复合物的结构进行了构型优化和能量计算, 并讨论了几何构型、自然键轨道(NBO)、振动频率、能量参数及NMR数据与结构的关系, 最后得到复合物结构的稳定性信息, 具有T_h对称性的X@(HAlNH)₁₂ (X＝F^－, Cl^－, Br^－, S^2－, Se^2－)复合物和具有C₃对称性的O^2－@(HAlNH)₁₂复合物为内含式的基态结构, 从能量角度分析, 内含式复合物比外接式复合物的结构稳定.     

X@(HAlNH)12和X(HAlNH)12 (X＝F－, Cl－, Br－, O2－, S2－, Se2－)复合物的结构和稳定性

用DFT的B3LYP方法在6-31G(d)基组的水平上, 对闭式多面体簇合物(HAlNH)₁₂及其内含式X@(HAlNH)₁₂和外接式X(HAlNH)₁₂ (X＝F^－, Cl^－, Br^－, O^2－, S^2－, Se^2－)复合物的结构进行了构型优化和能量计算, 并讨论了几何构型、自然键轨道(NBO)、振动频率、能量参数及NMR数据与结构的关系, 最后得到复合物结构的稳定性信息, 具有T_h对称性的X@(HAlNH)₁₂ (X＝F^－, Cl^－, Br^－, S^2－, Se^2－)复合物和具有C₃对称性的O^2－@(HAlNH)₁₂复合物为内含式的基态结构, 从能量角度分析, 内含式复合物比外接式复合物的结构稳定.     

Coherent Vibrational Dynamics of [Au25(SR)18]- Nanoclusters?

Coherent vibrational dynamics can be observed in atomically precise gold nanoclusters using femtosecond time-resolved pump-probe spectroscopy. It can not only reveal the coupling between electrons and vibrations, but also reflect the mechanical and electronic properties of metal nanoclusters, which holds potential applications in biological sensing and mass detection. Here, we investigated the coherent vibrational dynamics of [Au₂₅(SR)₁₈]^- nanoclusters by ultrafast spectroscopy and revealed the origins of these coherent vibrations by analyzing their frequency, phase and probe wavelength distributions. Strong coherent oscillations with frequency of 40 cm^-1 and 80 cm^-1 can be reproduced in the excited state dynamics of [Au₂₅(SR)₁₈]^-, which should originate from acoustic vibrations of the Au₁₃ metal core. Phase analysis on the oscillations indicates that the 80 cm^-1 mode should arise from the frequency modulation of the electronic states while the 40 cm^-1 mode should originate from the amplitude modulation of the dynamic spectrum. Moreover, it is found that the vibration frequencies of [Au₂₅(SR)₁₈]^- obtained in pump-probe measurements are independent of the surface ligands so that they are intrinsic properties of the metal core. These results are of great value to understand the electron-vibration coupling of metal nanoclusters.     

Multiple-layer heterometallic MnII–AgI coordination polymers constructed from [Ag 2I (CN)3]? and [AgI(CN)2]? units

Two multiple-layer heterometallic Mn^II–Ag^I coordination polymers, {Mn^II(ampyz)(H₂O)[Ag₂^I(CN)₃][Ag^I(CN)₂]·ampyz} _n (1) and {[Mn^II(benzim)₂[Ag^I(CN)₂]₂][(benzim)Ag^I(CN)]·H₂O} _n (2) where ampyz = 2-aminopyrazine and benzim = benzimidazole, have been prepared and structurally characterized. Compound 1 reveals a multiple-layer two-dimensional network with strong hexanuclear argentophilic interactions leading to an infinite three-dimensional framework. Compound 2 has an unprecedented double-layer two-dimensional squared grid-type network with (4,4) topology through Ag^I···Ag^I and π–π interactions between two adjacent squared layers. These double-layer networks of 2 are linked to others by π–π interactions, leading to a three-dimensional framework.     

Molecular and crystal structures of [FeCl(HMPA)3(H2O)2]2+(FeCl4) 2? · 3HMPA

IR and single-crystal X-ray diffraction study are carried out for compound, C₃₆H₁₁₂Cl₉Fe₃N₁₈O₈P₆(I). It crystallizes in the orthorhombic space group P2₁2₁2₁ with a = 14.2992(3), b = 21.4351(4), c = 25.5407(5) ?, V = 7828.3(3) ?³, ρ_calcd = 1.553 g/cm³, Z = 4. The FeCl fragment is coordinated with chlorine atom of two water molecules and three HMPA molecules to form a cation, with a distorted octahedral coordinate geometry. In the crystal I, the cation is linked with HMPA by the O-H…O hydrogen bond. The chiral crystal is formed through self-assembly even from achiral molecules.     

Reactions of atomic transition-metal ions with long-chain alkanes

Understanding metal ion interactions with long-chain alkanes not only is of fundamental importance in the areas of organometallic chemistry, surface chemistry, and catalysis, but also has significant implication in mass spectrometry method development for the analysis of polyethylene. Polyethylene represents one of the most challenging classes of polymers to be analyzed by mass spectrometry. In this work, reactions of several transition-metal ions including Cr+, Mn+, Fe+, Co+, Ni+, Cu+, and Ag+ with long-chain alkanes, C28H58 and C36H74, are reported. A metal powder and the nonvolatile alkane are co-deposited onto a sample target of a laser desorption/ionization (LDI) time-of-flight mass spectrometer. The metal ions generated by LDI react with the vaporized alkane during desorption. It is found that all these metal ions can form adduct ions with the long-chain alkanes. Fe+, Co+, and Ni+ produce in-source fragment ions resulting from dehydrogenation and dealkylation of the adduct ions. The post-source decay (PSD) spectra of the metal-alkane adduct ions are recorded. It is shown that PSD of Ag+ alkane adduct ions produces bare metal ions only, suggesting weak binding between this metal ion and alkane. The PSD spectra of the Fe+, Co+, and Ni+ alkane adduct ions display extensive fragmentation. Fragment ions are also observed in the PSD spectra of Cr+, Mn+, and Cu+ alkane adduct ions. The high reactivity of Fe+, Co+, and Ni+ is consistent with that observed in small alkane systems. The unusually high reactivity of Cr+, Mn+, and Cu+ is rationalized by a reaction scheme where a long-chain alkane first forms a complex with a metal ion via ion/induced dipole interactions. If sufficient internal energy is gained during the complex formation, metal ions can be inserted into C-H and C-C bonds of the alkane, followed by fragmentation. The thermal energy of the neutral alkane is believed to be the main source of the internal energy acquired in the complex. Finally, the implication of this work on mass spectrometry method development for polyethylene analysis is discussed.     

Competing binding of metal ions with protein studied by microdialysis

A method has been established to study the competing binding of metal ions with protein by a combined technique of microdialysis with high performance liquid chromatography (HPLC). Ni2+, Cd2+, Zn2+, Cu2+ and human serum albumin (HSA) were chosen as model metal ions and protein. The experimental results show that Ni2+ and Cu2+ share a common primary binding site on HSA, and Zn2+ and Cd2+ share a different common primary binding site from them, but there is a common multi-metal binding site for all of those four metal ions. This method show advantages of fast sampling, easily to be operated and especially to be useful when ideal spectroscopic probes are not available for the study of interaction between protein and metal ions.     

一种高选择性汞(Ⅱ) 吸附剂的制备和应用

利用两步反应法制备了溴联苯三酚红功能性硅胶(BPRSG),并通过静态平衡方法研究了该功能性硅胶对多种性质相近的金属离子的选择性吸附性能,考察了溶液pH值和搅拌时间对Hg?吸附率的影响。结果表明,在pH=7.0时,该固相萃取剂对Hg(Ⅱ)有特异的选择性吸附,可以实现与Pb(Ⅱ),Co(Ⅱ),Mn(Ⅱ),Zn(Ⅱ),Cu(Ⅱ),Cd(Ⅱ),Ni(Ⅱ)等金属离子的选择性分离,对Hg?的吸附平衡时间为30 min;最大吸附容量为4.80 mg/g。将该吸附剂制成微型固相萃取柱,用动态平衡法研究了柱流速、洗脱剂种类、洗脱速度和各种干扰离子对分离富集Hg(Ⅱ)的影响。在优化条件下,微柱对Hg?的最低富集浓度为10μg/L,富集倍率为170倍,柱容量为0.65 mg/g。20种常见离子不干扰Hg?的吸附,用1.0 mol/L醋酸即可洗脱Hg(Ⅱ),柱子可重复使用。将微柱用于环境水样中Hg?的固相萃取,回收率在95.5%～98.0%之间。     

2'-硼酸基苯甲醛-7-(8-羟基-5-磺酸基)喹啉腙衍生物的合成及对Pb2+的识别

合成了2', 3'和4'-硼酸基苯甲醛-7-(8-羟基-5-磺酸基)喹啉腙衍生物(化合物1~3), 研究了硼酸基团取代位置对主体分子识别金属离子客体性能的影响, 比较了不同主体分子与Pb2+结合能力的差异. 研究结果表明, 在pH=7.0的KH2PO4-NaOH缓冲溶液中, 3种腙衍生物对Pb2+均具有选择性识别作用, 主客体分子间形成1∶1型的发光配合物. 其中邻位取代的化合物1与Pb2+的结合能力比化合物2和3强, 配合物1-Pb2+的最大发射波长为477 nm, 稳定常数为1.1×103 L/mol. 其它金属离子如Cu2+, Mn2+, Mg2+, Fe2+, Ca2+, Co2+, Ni2+, Hg2+, Cd2+和Ag+ 等对主体分子荧光光谱的影响较小. 同时, 荧光强度的变化值与Pb2+浓度在0.36~10 μmol/L范围内呈现良好的线性关系, 相关系数R=0.9976(n=16), 检出限为0.23 μmol/L. 将此方法用于环境水样中Pb2+的测定, 回收率为92%~108%.     

Acid-base and metal-ion binding properties of the RNA dinucleotide uridylyl-(5'-->3')-[5']uridylate (pUpU3-)

It is well known that Mg2+ and other divalent metal ions bind to the phosphate groups of nucleic acids. Subtle differences in the coordination properties of these metal ions to RNA, especially to ribozymes, determine whether they either promote or inhibit catalytic activity. The ability of metal ions to coordinate simultaneously with two neighboring phosphate groups is important for ribozyme structure and activity. However, such an interaction has not yet been quantified. Here, we have performed potentiometric pH titrations to determine the acidity constants of the protonated dinucleotide H2(pUpU)-, as well as the binding properties of pUpU3- towards Mg2+, Mn2+, Cd2+, Zn2+, and Pb2+. Whereas Mg2+, Mn2+, and Cd2+ only bind to the more basic 5'-terminal phosphate group, Pb2+, and to a certain extent also Zn2+, show a remarkably enhanced stability of the [M(pUpU)]- complex. This can be attributed to the formation of a macrochelate by bridging the two phosphate groups within this dinucleotide by these metal ions. Such a macrochelate is also possible in an oligonucleotide, because the basic structural units are the same, despite the difference in charge. The formation degrees of the macrochelated species of [Zn(pUpU)]- and [Pb(pUpU)]- amount to around 25 and 90 %, respectively. These findings are important in the context of ribozyme and DNAzyme catalysis, and explain, for example, why the leadzyme could be selected in the first place, and why this artificial ribozyme is inhibited by other divalent metal ions, such as Mg2+.     

Two-photon fluorescent probes for long-term imaging of calcium waves in live tissue

2-Acetyl-6-(dimethylamino)naphthalene-derived two-photon fluorescent Ca2+ probes (ACa1-ACa3) are reported. They can be excited by a 780 nm laser beam, show 23-50-fold enhancement in one- and two-photon excited fluorescence in response to Ca2+, emit fourfold stronger two-photon excited fluorescence than Oregon Green 488 BAPTA-1 upon complexation with Ca2+, and can selectively detect intracellular free Ca2+ ions in live cells and living tissues with minimum interference from other metal ions and membrane-bound probes. Moreover, these probes are capable of monitoring calcium waves at a depth of 120-170 microm in live tissues for 1100-4000 s using two-photon microscopy with no artifacts of photobleaching.     

Immobilized metal affinity chromatography for the separation of photosystems I and II from the thermophilic cyanobacterium Synechococcus elongatus

Immobilized metal affinity chromatography (IMAC) of solubilized, photosystem II (PS II) enriched particles from the thermophilic cyanobacterium Synechococcus elongatus was studied. A chelating Sepharose Fast Flow column was charged with various metal ions (Mn2+, Fe2+, Fe3+, Ni2+, Co2+, Ca2+, Sr2+, Zn2+ and Cu2+) and their affinity to photosystem I (PS I) and PS II was examined. Among all the metal ions tested, only copper was able to bind the two protein complexes. For elution of the column, a pH gradient, a pH step gradient and gradients of imidazole, amino acids, organic acids and various other eluents were tested; only the pH step gradient, which selectively eluted PS II at a pH between 6 and 5, was useful for the separation of PS I and PS II. All other gradients proved to be inappropriate for the separation of these two photosystems. Mechanisms of protein elution by these compounds are discussed. Alternatively, a separation of PS I and PS II at pH 7.5 could be achieved when an IMAC column was used on which the free coordination positions of the bound copper ions were occupied by imidazole. When solubilized photosystems were loaded on to this column, PS I replaced imidazole and remained bound on the column, whereas PS II was highly enriched in the effluent.     

Novel chiral N4S2- and N6S3-donor macrocyclic ligands: synthesis,protonation constants,metal-ion binding and asymmetric catalysis in the Henry reaction

New hydrophobic chiral macrocyclic ligands L1-L3 with chiral diamino and thiophene moieties have been synthesized by the Schiff base condensation approach. Protonation constants of L1 and L2 were determined by potentiometry titration. Metal-ion binding experiments exhibited that L1 and L3 are pronounced in selective recognition, Ag+, Cu2+ and Ca2+ ions among the surveyed metal ions (Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, Ag+, Li+, Na+, K+, and Ca2+). L1 was found to spectroscopically detect the presence of Cu2+ and Ca2+ to function as a multiple readout sensor. The detection limit for Ca2+ ions was found to be 9.8 x 10(-5) M in CH2Cl2-MeOH solution. The trimeric chiral ligand L3 has been shown to be an efficient auxiliary in a Zn(II)-mediated enantioselective Henry reaction.     

羧甲基壳聚糖/聚乙烯醇/甘油环氧树脂蛇笼型复合螯合膜的制备及对金属离子的吸附性能

以交联甘油环氧树脂交联的聚乙烯醇(PVA)为笼树脂，羧甲基壳聚糖(CCTS)为蛇树脂制备了具有蛇笼结构的复合螯合膜，研究了其对Cu^2 、Ni^2 、Pb^2 、Fe^3 、Zn^2 ，Hg”^2 、Cd^2 等金属离子的吸附性能，研究表明，该树脂对Cu^2 、Ni^2 、Pb^2 有较好的吸附性能，其中PVA是对Cu^2 的吸附的主要贡献者，而CCTS则是在对Ni^2 的吸附中起主要作用。该树脂可以用于含Cu^2 废水的处理。     

THE THEORETICAL STUDY OF ADSORPTION OF METAL IONS ON CHITOSAN

The interactions between metal ions such as Zn2+, Pb2+, Mn2+, Hg2+, Cd2+, Ni2+ and chitosan have been investigated using the model cluster model method and density functional method. Full optimization and frequency analysis of all cluster models have been performed employing B3LYP hybrid method at 3-21G basis set level except metal ions which were invoked to use effective core potential (ECP) method. The energy changes, and the main structural parameters have been obtained during the theoretical study of the adsorption of metal ions on the chitosan. The calculations showed that the coordination modes of metal ions with chitosan models were different, the geometries of Mn2+, Zn2+, Cd2+, Hg2+, Pb2+ ions coordinated with two nitrogen atoms and two oxygen atoms were distorted tetrahedral, while the square planar structure of Ni2+ coordinated two nitrogen atoms and two oxygen atoms was observed. The heat of reaction between six metal ions and chitosan models showed the order: Mn2+ ＞Ni2+ ＞Zn2+ ＞Pb2+ ＞Hg2+ ＞Cd2+, this suggested that the coordination strength of Mn2+ ＞Ni2+ ＞Zn2+ ＞Pb2+ ＞Hg2+ ＞Cd2+.