Determination of trace mercury by solid substrate-room temperature phosphorimetry based on catalytic effect of Hg(2+) on formation of the ion association complex [Fe(bipy)(3)](2+)[(FinBr(4))(2)](2-)

A new solid substrate-room temperature phosphorimetry method for the determination of trace mercury has been established. It bases on the fact that in acetic acid medium, Hg²⁺ ion can catalyze the substitute reaction of CN⁻ ligand in [Fe(CN)₆]⁴⁻ by 2,2′-bipyridyl (bipy), and the resultant [Fe(bipy)₃]²⁺ cation can react with FinBr₄⁻ anion of tetrabromofluorescein (HFinBr₄) to form ion association complex [Fe(bipy)₃]²⁺[(FinBr₄)₂]²⁻ which can emit phosphorescent signal on filter paper substrate. Under the optimum condition, the linear dynamic range of this method is 1.6-16 fg per spot with a detection limit (LD) of 0.18 fg per spot (0.4 μl sample solution per spot), and the regression equation of working curve is ΔI_p=1.058+7.671 C_Hg²⁺ (fg per spot ), n=7, correlation coefficient is 0.9990. This method has been applied to the determination of trace mercury in hair and cigarette samples with satisfactory result. The reaction mechanism for formation of the ion association complex is also discussed.     

IR and Raman spectra of two layered aluminium phosphates Co(en)3Al3P4O16 · 3H2O and [NH4]3[Co(NH3)6]3[Al2(PO4)4]2 · 2H2O

The FT IR and FT Raman spectra of Co(en)₃Al₃P₄O₁₆ · 3H₂O (compound I) and [NH₄]₃[Co(NH₃)₆]₃[Al₂(PO₄)₄]₂ · 2H₂O (compound II) are recorded and analysed based on the vibrations of Co(en)₃³⁺, Co(NH₃)₆³⁺, NH₄⁺, Al---O---P, PO₃, PO₂ and H₂O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH₂ deformation Fermi resonates with its symmetric stretching vibration. The NH₄ ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.     

Influence of several factors on potential-modulated DNA cleavage by the Cu(en)2 and Cu(EDTA) complexes

Potential-modulated DNA cleavage in the presence of copper–ethylenediamine (en) and –ethylenediamine tetraacetic acid (EDTA) complexes was investigated at a gold electrode in a thin layer cell. DNA can be efficiently cleaved through production of active oxygen species at −0.50 V (vs. Ag/AgCl/KCl(sat)) by reducing Cu(en)₂²⁺ to Cu(en)₂⁺ or Cu(EDTA)²⁻ to Cu(EDTA)³⁻. The extent of DNA cleavage increased as the working potential was shifted more negative and the electrolysis time was increased in air-saturated solution. When a small flow of O₂ was passed through the solution during electrolysis, the extent of DNA cleavage was dramatically enhanced. In the absence of Cu(en)₂²⁺ or Cu(EDTA)²⁻ complex, slight DNA cleavage was observed at a more negative working potential due to the reduction of oxygen at the electrode. This observation suggests that potential-modulated DNA cleavage was caused mainly by electrochemical reduction of the Cu(en)₂²⁺ or Cu(EDTA)²⁻ complex in the presence of oxygen. The cleaved DNA fragments were separated by high performance liquid chromatography (HPLC). The experimental results proved that this method of potential-modulated DNA cleavage by Cu(en)₂²⁺ and Cu(EDTA)²⁻ complexes is simple, mild and highly efficient.     

Spectroscopic properties of guanidinium zinc sulphate [C(NH2)3]2Zn(SO4)2 and ab initio calculations of [C(NH2)3]2 and HC(NH2)3

Raman and FTIR spectra of guanidinium zinc sulphate [C(NH₂)₃]₂Zn(SO₄)₂ are recorded and the spectral bands assignment is carried out in terms of the fundamental modes of vibration of the guanidinium cations and sulphate anions. The analysis of the spectrum reveals distorted SO₄²⁻ tetrahedra with distinct S–O bonds. The distortion of the sulphate tetrahedra is attributed to Zn–O–S–O–Zn bridging in the structure as well as hydrogen bonding. The CN₃ group is planar which is expressed in the twofold symmetry along the C–N (1) vector. Spectral studies also reveal the presence of hydrogen bonds in the sample. The vibrational frequencies of [C(NH₂)₃]₂ and HC(NH₂)₃ are computed using Gaussian 03 with HF/6-31G* as basis set.     

一维双核锌配合物[Zn2(SHSH)2(2-Me-py)2]的合成、晶体结构及理论研究

The crystal of one-dimensional binuclear zinc complex [Zn₂(SHSH)₂(2-Me-py)₂] was obtained in DMF and 2-methylpyridine, where SHSH is salicylaldehyde salicylhydrazone. It has been characterized by IR, UV, element analysis and X-ray diffraction analysis. The crystallographic data were as follows: monoclinic system, space group P2₁/c, a=1.144 49 nm, b=1.206 69 nm, c=1.379 39 nm, β=97.039°, Z=2, V=1.890 6 nm³, M_r=825.47, D_c=1.450 g·cm^-3, μ=1.324 mm-1, F(000)=848 and the final R=0.033 6 and wR=0.094 7 for 3 752 observed reflections with I≥2σ(I). The theoretical investigation of title complex as a structure unit was carried out at B3LYP/6-31G and HF/6-31G levels with Guassian 03W program, and the atomic charges, natural bond orbital analysis and bond energies were also discussed. CCDC: 260920.     

Crystal structure and characterization of Rb2Ca[B4O5(OH)4]2·8H2O

Dirubidium calcium tetraborate octahydrate, Rb₂Ca[B₄O₅(OH)₄]₂·8H₂O, was prepared by reaction of Rb-borate aqueous solution with CaCl₂ and it's structure has been determined by single-crystal X-ray diffraction data. It crystallizes in the orthorhombic system, space group P2₁2₁2₁ with unit cell parameters, Z=4, The structure contains alternate layers of [B₄O₅(OH)₄]²⁻ polyanions separated by water molecules and Rb, Ca cations. The isolated [B₄O₅(OH)₄]²⁻ is constructed from two BO₃(OH) tetrahedron groups and two BO₂(OH) triangular groups joined at common oxygen atoms. The two BO₃(OH) tetrahedron groups are further linked by means of an oxygen bridge across the ring. The Ca²⁺ ion displays seven coordination, while the two non-equivalent Rb⁺ ions display nine and seven coordination, respectively. Infrared and Raman (4000-400 cm⁻¹) spectra of Rb₂Ca[B₄O₅(OH)₄]₂·8H₂O were recorded at room temperature and analyzed. Fundamental vibrational modes were identified and band assignments were made. The dehydration of this hydrated mixed borate occurs in one step and leads to an amorphous phase which undergoes a crystallization.     

Novel M(II)–Hg(II) coordination polymers generated from metal-containing building blocks M(2-pyrazinecarboxylate)2 · (H2O)2 (M=Cu, Ni, Co) and HgCl2

A new class of M(II)–Hg(II) (M=Cu(II), Co(II), Ni(II)) mixed-metal coordination polymers, Cu(2-pyrazinecarboxylate)₂HgCl₂ (4), [Co(2-pyrazinecarboxylate)₂(HgCl₂)₂] · 0.61H₂O (5) and [Ni(2-pyrazinecarboxylate)₂(HgCl₂)₂] · 0.77H₂O (6), have been prepared by self assembly of metal-containing building blocks, M(2-pyrazinecarboxylate)₂ · (H₂O)₂(M=Cu(II), Co(II), Ni(II)), with HgCl₂. Compounds 4–6 were characterized fully by IR, elemental analysis and single crystal X-ray diffraction. Compound 4 crystallized in the monoclinic space group C2/c, with a=17.916(5) Å, b=7.223(2) Å, c=13.335(4) Å, β=128.726(3)°, V=1346.2(6) ų, Z=4. It contains alternating Hg(II) and Cu(II) metal centers that are cross-linked by 2-pyrazinecarboxylate spacers and chlorine co-ligands to generate a unique three-dimensional Hg(II)–Cu(II) mixed metal framework. Compound 5 crystallized in the triclinic space group P , with a=6.3879(7) Å, b=6.6626(8) Å, c=13.2286(15) Å, α=96.339(2)°, β=91.590(2)°, γ=113.462(2)°, V=511.71(10) ų, Z=1. Compound 6 also crystallized in the triclinic space group P , with a=6.3543(8) Å, b=6.6194(8) Å, c=13.2801(16) Å, α=96.449(2)°, β=92.263(2)°, γ=113.541(2)°, V=506.67(11) ų, Z=1. Compounds 5 and 6 are isostructural and in the solid state the Hg(II)M(II)Hg(II) units are connected by Hg₂Cl₂ linkages to produce a novel M(II)–Hg(II) (M=Co(II), Ni(II)) zigzag mixed-metal chain, in which a new type of M–M′–M′–M array was observed. The metal containing building blocks, M(2-pyrazinecarboxylate)₂ · (H₂O)₂ (M=Cu(II), Co(II), Ni(II)), exhibit different connectivities to HgCl₂ depending on the metal cation contained within them.     

[Ru(bpy)3] nanocomposites containing heteropolyacids: Simple preparation and stable solid-state electrochemiluminescence detection application

In order to solidify the electrochemiluminescence (ECL) luminophor tris(2,2′-bipyridyl) ruthenium(II) ([Ru(bpy)₃]²⁺) onto the electrode surfaces robustly, the negative charged heteropolyacids (HPAs) moieties were utilized to attract and bond cations [Ru(bpy)₃]²⁺ via an adsorption method. The compositions and microstructures of the hybrid complexes were characterized by elemental analysis (EDS), spectroscopic techniques (UV-vis, FTIR) and field-emission scanning electron microscopy (FE-SEM). The electrochemical and ECL behaviors of the [Ru(bpy)₃]²⁺/[PW₁₂O₄₀]³⁻ hybrid complex contained in the solid film of the nanocomposites formed on the electrode surfaces were also studied. It was found that the corresponding solid membranes exhibited a diffusion-controlled voltammetric feature and excellent electrochemiluminescence behaviors. Hence potential prospects as new electrochemiluminescent materials for application in electroanalytical detection are envisioned.     

Syntheses, structures, and magnetic and optical properties of the compounds [Hg3Te2][UCl6] and [Hg4As2][UCl6]

Two new quaternary salts, [Hg₃Te₂][UCl₆] and [Hg₄As₂][UCl₆], have been synthesized and their structures determined by single-crystal X-ray diffraction analysis. [Hg₃Te₂][UCl₆] is the product of a reaction involving UCl₄, HgCl₂, and HgTe at 873 K. The compound crystallizes in space group P2₁/c of the monoclinic system. [Hg₄As₂][UCl₆] results from the reaction of U, Hg₂Cl₂, and As at 788 K. It crystallizes in space group Pbca of the orthorhombic system. [Hg₃Te₂][UCl₆] has a two-dimensional framework of layers, whereas [Hg₄As₂][UCl₆] has a three-dimensional framework of layers interconnected by Hg atoms linearly bonded to As atoms. Both framework structures contain discrete [UCl₆]²⁻ anions between the layers. [Hg₃Te₂][UCl₆] exhibits temperature-independent paramagnetism. The optical absorption spectra of these compounds display f-f transitions.     

Hydrothermal synthesis, characterization and thermochemistry of Ca2[B2O4(OH)2]·0.5H2O

A pure calcium borate Ca₂[B₂O₄(OH)₂]·0.5H₂O has been synthesized under hydrothermal condition and characterized by XRD, FT-IR and TG as well as by chemical analysis. The molar enthalpy of solution of Ca₂[B₂O₄(OH)₂]·0.5H₂O in HC1·54.582H₂O was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in HC1·54.561H₂O and of CaO in (HCl + H₃BO₃) solution, together with the standard molar enthalpies of formation of CaO(s), H₃BO₃(s) and H₂O(l), the standard molar enthalpy of formation of −(3172.5 ± 2.5) kJ mol⁻¹ of Ca₂[B₂O₄(OH)₂]·0.5H₂O was obtained.     

Calorimetric study and thermal analysis of [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O (Gly: glycin)

Two solid-state coordination compounds of rare earth metals with glycin, [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O and [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 342.90 K, while [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol⁻¹ and 53.9 J K⁻¹ mol⁻¹ for [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, 1.82 kJ mol⁻¹ and 5.5 J K⁻¹ mol⁻¹ for [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.     

Low-dimensional compounds containing cyano groups. XVII. Crystal structure, spectroscopic, thermal and magnetic properties of [Cu(bmen)2][Pt(CN)4] (bmen=N,N′-dimethylethylenediamine)

The synthesis, structural analysis, spectroscopic studies, susceptibility and specific-heat measurements of {[Cu(bmen)₂][Pt(CN)₄]}_n (bmen=N,N′-dimethylethylenediamine) are presented. X-ray crystal-structure analysis revealed that the [Pt(CN)₄]²⁻ building blocks are combined with [Cu(bmen)₂]²⁺ units to form a chain-like structure along the a axis. The Cu(II) atoms are hexacoordinated by four nitrogen atoms in the equatorial plane belonging to two molecules of bidentate bmen ligands with average Cu-N distance of 2.043(18) Å. The axial positions are occupied by two nitrogen atoms from bridging [Pt(CN)₄]²⁻ anions at a longer axial Cu-N distance of 2.490(4) Å. The compound is characterized by the presence of a weak antiferromagnetic exchange coupling J/k_B=0.6 K. Despite the one-dimensional (1D) character of the structure, the analysis of the magnetic properties and specific heat at very low temperatures shows that [Cu(bmen)₂][Pt(CN)₄] behaves as a two-dimensional (2D) square-lattice Heisenberg magnet with weak interlayer coupling.     

Thermochemistry of NaRb[B4O5(OH)4]·4H2O

The enthalpies of solution of NaRb[B₄O₅(OH)₄]·4H₂O in approximately 1 mol dm⁻³ aqueous hydrochloric acid and of RbCl in aqueous (hydrochloric acid + boric acid + sodium chloride) were determined. From these results and the enthalpy of solution of H₃BO₃ in approximately 1 mol dm⁻³ HCl(aq) and of sodium chloride in aqueous (hydrochloric acid + boric acid), the standard molar enthalpy of formation of −(5128.02 ± 1.94) kJ mol⁻¹ for NaRb[B₄O₅(OH)₄]·4H₂O was obtained from the standard molar enthalpies of formation of NaCl(s), RbCl(s), H₃BO₃(s) and H₂O(l). The standard molar entropy of formation of NaRb[B₄O₅(OH)₄]·4H₂O was calculated from the Gibbs free energy of formation of NaRb[B₄O₅(OH)₄]·4H₂O computed from a group contribution method.     

反相离子对高效液相色谱法分离金属配合物｛Fe［3-(2-吡啶基)-5,6-二苯基-1,2,4-三嗪］3｝2+几何异构体

采用反相离子对高效液相色谱法分离测定了金属配合物｛Fe［3-(2-吡啶基)-5,6-二苯基-1,2,4-三嗪］3｝2+ (［Fe(PDT)3］2+)的两种几何异构体,研究了流动相中有机改性剂(乙腈、甲醇)的含量、不同种类和浓度的离子对试剂(高氯酸钠和十二烷基硫酸钠(SDS))对色谱分离的影响。并在不同的试验条件下,对所获得的色谱参数(保留因子(k)、分离度、选择性因子等)进行了探讨。在不同种类及浓度的离子对试剂条件下,二元流动相中乙腈的含量与两种几何异构体的ln k之间均呈显著的线性关系。研究进一步发现SDS的浓度变化对异构体的保留因子影响程度更为显著。在上述实验的基础上,引入更能灵活调节洗脱强度和分离度的三元流动相(乙腈/甲醇/水),优化选择了三元流动相中有机改性剂的比例以及离子对试剂的种类和浓度,使得异构体的色谱分离得到了满意的结果。实验结果表明,异构体的峰面积(A)和浓度(C)之间的线性关系良好,面式和经式异构体的检测限分别为4.28和3.44 ng/mL (S/N=3)。     

Coordination behaviour of the multidentate Schiff base 2,6-bis(2-hydroxyphenyliminomethyl)pyridine towards the fac-[Re(CO)3] and [ReO] cores

The seven-coordinate rhenium(III) complex cation [Re^III(dhp)(PPh₃)₂]⁺ was isolated as the iodide salt from the reaction of cis-[Re^vO₂I(PPh₃)₂] with 2,6-bis(2-hydroxyphenyliminomethyl)pyridine (H₂dhp) in ethanol. In the complex fac-[Re(CO)₃(H₂dhp)Br], prepared from [Re(CO)₅Br] and H₂dhp in toluene, the H₂dhp ligand acts as a neutral bidentate N,N-donor chelate. The complexes were characterized by elemental analysis, infrared and ¹H NMR spectroscopy and X-ray crystallography.     

Spectroscopic and photoelectrochemical differences between racemic and enantiomeric [Ru(phen)3] ions intercalated into layered niobate K4Nb6O17

Chirality effects have been observed in the intercalation, spectroscopic and photoelectrochemical behavior when enantiomeric and racemic [Ru(phen)₃]²⁺ complexes were intercalated in the interlayer spaces of K₄Nb₆O₁₇. The results were interpreted in terms of a [Nb₆O₁₇]⁴⁻-chelate and chelate–chelate interactions. The faster luminescence decay and higher photocurrent of the enantiomeric [Ru(phen)₃]²⁺–K₄Nb₆O₁₇ compounds than the racemic ones suggest that the emission of adsorbed [Ru(phen)₃]²⁺ ions was not only quenched by adsorbed complexes (or concentration quenching) but also by the semiconductive host lattices.     

Imidazole-based bifunctional chelates for the “fac-[Re(CO)3]” core

Three monocationic rhenium(I) complexes of the type [Re(CO)₃(L)]Br, containing the bis-imidazole tridentate ligands bis-(2-(1-methylimidazolyl)methyl)amine (L¹), bis-(2-(1-methylimidazolyl)methyl)aminoethanol (L²) and bis-(2-(benzimidazolyl)ethyl)sulfide (L³), were prepared and characterized by ¹H NMR and IR spectroscopy. The complex salt [Re(CO)₃(L²)]Br (2) was also characterized by X-ray crystallography. The structure consists of discrete monocationic monomers with a fac-[Re(CO)₃]⁺ coordination unit, and the remaining three sites are occupied by one amine and two imidazolyl nitrogen donor atoms.     

螺桨烷型分子BX[(CH_2)_n]_3和BX(CH_2)[CH(CH_2)_nCH](X=N,P)的结构和性质

采用密度泛函理论(DFT)研究了螺桨烷型分子BX[(CH2)n]3和BX(CH2)[CH(CH2)n CH](X=N,P;n=1-6)的结构、稳定性、化学键和电子光谱性质.计算结果表明这些分子都是稳定的.BX[(CH2)n]3(X=N,P;n=1-6)的最高占据分子轨道(HOMO)和最低空分子轨道(LUMO)之间的能隙均大于5.20 eV,其中BN[CH2]3和BP[CH2]3的能隙超过7.0 eV,与C5H6的能隙(7.27 eV)很接近,BX(CH2)[CH(CH2)n CH](X=N,P;n=1-6)的能隙在6.80 eV左右.所研究分子能量的二阶差分表明BN[(CH2)3]3、BP[(CH2)4]3及BX(CH2)[CH(CH2)2CH](X=N,P)是最稳定的.BX[(CH2)n]3的Wiberg键级表明除了BN[(CH2)n]3(n=2和6)中不存在B―N键,其它化合物中B和N均形成了化学键,BP[(CH2)n]3中除了BP[(CH2)2]3不存在B―P键,其它的均存在.电子密度的拓扑分析表明N―B键属于离子键,而P―B键具有共价键特征.BX[(CH2)n]3(X=N,P)的第一垂直激发能分别在191.1-284.8 nm和191.8-270.1 nm之间,BX(CH2)[CH(CH2)n CH](X=N,P)的第一垂直激发能分别在190.5-199.7 nm和209.0-221.3 nm之间.     

Mechanism of Formation of Nanocrystalline ZnO Particles through the Reaction of [Zn(acac)2] with NaOH in EtOH

The mechanism of formation of nanocrystalline ZnO particles from the reaction of zinc acetylacetonate ([Zn(acac)₂]) with 2-equivalent NaOH in boiling EtOH was investigated by characterizing the particles and following the transformation of acac moieties. The reaction was found to proceed via hydrolysis of zinc ethoxide derivatives, followed by dehydration–condensation reactions. High-resolution solid-state CP-MAS¹³C NMR measurements indicate that the ZnO particles are produced through Zn (acac)(OZn)_n(acac) (3). Furthermore, it was suggested that acac⁻ligands play an important role in the generation of nanocrystalline ZnO particles by suppressing the hydrolysis–condensation of Zn(acac)(OZn)_n(acac).     

Synthesis, heat capacity and enthalpy of formation of [Ho2(l-Glu)2(H2O)8](ClO4)4·H2O

A complex of holmium perchlorate coordinated with l-glutamic acid, [Ho₂(l-Glu)₂(H₂O)₈](ClO₄)₄·H₂O, was prepared with a purity of 98.96%. The compound was characterized by chemical, elemental and thermal analysis. Heat capacities of the compound were determined by automated adiabatic calorimetry from 78 to 370 K. The dehydration temperature is 350 K. The dehydration enthalpy and entropy are 16.34 kJ mol⁻¹ and 16.67 J K⁻¹ mol⁻¹, respectively. The standard enthalpy of formation is −6474.6 kJ mol⁻¹ from reaction calorimetry at 298.15 K.