Cocrystallization of ultramicro quantities of elements with 2-mercaptobenzimidazole: Determination of gold in seawater

The cocrystallization of ultramicro quantities of 25 diverse elements with 2-mercaptobenzimidazole was investigated with the aid of radiotracers. Under optimum conditions Sn, Hg, Ag, Ta and Au were recovered in high yield. Distribution coefficients between mother liquor and solid phase were calculated for gold and were found to vary inversely with the degree of crystallization and the hydrogen ion concentration. The cocrystallization process was applied to the isolation and subsequent determination of the natural gold abundance in seawater. After radiometric correction for chemical yield, the concentration of gold was calculated to be 0.068 ± 0.003 $\text{μg}\text{1}$.     

鲁米诺-二甲亚砜-氢氧化钠体系化学发光机理的理论研究

用密度泛函理论(DFT) B3PW91/6-31G**方法研究了鲁米诺-二甲亚砜-氢氧化钠化学发光反应体系中反应物、中间体和产物的分子结构和振动频率, 用B3PW91/6-311＋G(3df,2p)方法获得反应能量以及用时间相关(Time Dependent, TD)的B3PW91/6-311＋G(3df, 2p)方法进行电子激发能态分析. 研究结果支持了下列化学发光反应通道: LH₂(¹A)＋OH^－ →LH₂•OH^－(¹A)→LH^－(¹A)→L^·－(²A)→TS₁(³A)→LO₂^2－(³A)→TS₂(³A)→AP^2－*(?³A)→AP^2－(X³A)＋hν, 最后即AP^2－*回到基态发光; 或AP^2－*(?³A)→AP^2－*(?¹A)→AP^2－(a¹A)＋hν, 即激发态势能面交叉后的单重态跃迁发光. 它们在可见光区域主要有400～460和500～530 nm的强吸收谱带, 与实验结果符合. 研究还表明, 质子化的鲁米诺能量将大幅度降低, 说明酸性溶液导致鲁米诺的反应活性降低, 从理论上解释了鲁米诺化学发光体系的溶液须呈碱性, pH值影响发光反应的实验事实.     

Lower oxidation states of lanthanides and actinides. Prospects of their use in analytical practice

Physico-chemical characteristics of Ln²⁺ and An²⁺ such as standard oxidation potentials E_M ³⁺M²⁺, hydration energies, ionic radii were obtained by the cocrystallization method. A number of energy parameters for Ln²⁺ and U³⁺ were obtained by optical spectroscopy on the basis of fd-spectra in such solvents as H₂O, C₂H₅OH, HMPA, THP and others. A new rapid method has been developed to extract higher actinides and separate them from similar elements by cocrystallization with NaCl from aqueous ethanolic solutions.     

Ligand directed synthesis of a unprecedented tetragonalbipyramidal copper (II) complex and its antibacterial activity and catalytic role in oxidative dimerisation of 2-aminophenol

In pursuit of the significant contribution of copper ion in different biological processes, this research work describes the synthesis, X-ray structure, Hirshfeld surface analysis, oxidative dimerization of 2-aminophenol and antibacterial activity of a newly designed copper (II)-Schiff base complex, [Cu( L )₂] (1), [Schiff base (H L ) = 2-(2-methoxybenzylideneamino)phenol]. X- ray structural analysis of 1 reveals that the Cu (II) complex crystallizes in a cubic crystal system with Ia-3d space group. The Cu (II) centre adopts an unprecedented tetragonal bipyramidal geometry in its crystalline phase. The Schiff base behaves as a tridentate chelator and forms an innermetallic chelate of first order with Cu (II) ion. The copper (II) complex has been tested in the bio-mimics of phenaxozinone synthase activity in acetonitrile and exhibits good catalytic activity as evident from high turnover number, 536.4 h⁻¹. Electrochemical analysis exhibits the appearance of two additional peaks at −0.15 and 0.46 V for Cu (II) complex in presence of 2-AP and suggests the development of AP⁻/AP^•− and AP^•−/IQ redox couples in solution, respectively. The presence of iminobenzosemiquinone radical at g = 2.057 in the reaction mixture was confirmed by electron paramagnetic resonance and may be considered the driving force for the oxidative dimerisation of 2-AP. The existence of a peak at m/z 624.81 for Cu (II) complex in presence of 2-AP in electrospray ionization mass spectrum ensures that the catalytic oxidation proceeds through enzyme-substrate adduct formation. The copper (II) complex exhibits potential antibacterial properties against few pathogenic bacterial species like Staphylococcus aureus, Enterococcus and Klebsiella pneumonia and scanning electron microscope studies consolidates that destruction of bacterial cell membrane accounts on the development of antibacterial activity.     

A Novel Pentadentate Redox‐Active Ligand and Its Iron(III) Complexes: Electronic Structures and O2 Reactivity

A novel redox‐active ligand, H₄^Ph2SL^AP ( 1 ) which was designed to be potentially pentadentate with an O,N,S,N,O donor set is described. Treatment of 1 with two equivalents of potassium hydride gave access to octametallic precursor complex [H₂^Ph2SL^APK₂(thf)]₄ ( 2 ), which reacted with FeCl₃ to yield iron(III) complex [H₂^Ph2SL^APFeCl] ( 3 ). Employing Fe[N(SiMe₃)₂]₃ for a direct reaction with 1 led to ligand rearrangement through C?S bond cleavage and thiolate formation, finally yielding [HL^APFe] ( 5 ). Upon exposure to O₂, 3 and 5 are oxidized through formal hydrogen‐atom abstraction from the ligand NH units to form [^Ph2SL^SQFeCl] ( 4 ) and [L^SQFe] ( 6 ) featuring two or one coordinated iminosemiquinone moieties, respectively. Mössbauer measurements demonstrated that the iron centers remain in their +III oxidation states. Compounds 3 and 5 were tested with respect to their potential as models for the catechol dioxygenase. Thus, they were treated with 3,5‐di‐tert‐butyl‐catechol, triethylamine and O₂. It turned out that the iron–catecholate complexes react with O₂ in dichloromethane at ambient conditions through C?C bond cleavage mainly forming extradiol cleavage products. Intradiol products are only side products and quinone formation becomes negligible. This observation has been rationalized by a dissociation of two donor functions upon coordination of the catecholate.     

Labeling of a bifunctional monophosphinic acid DOTA analogue with <Superscript>111</Superscript>In: Radiochemical aspects and preclinical results

The complex formation of the bifunctional monophosphinic acid DOTA analogue DO3AP^ABn (1,4,7,10-tetraazacyclododecane-4,7,10-triacetic-1-{methyl[(4-aminophenyl)methyl] phosphinic acid}) with ¹¹¹In at a tracer level was analyzed. Formation of a complex between ¹¹¹In and DO3AP^ABn was very rapid even at room temperature and high radiolabeling yields were achieved. As introducing the methylphosphinic acid arm to the DOTA structure generated a chiral centre, more than one peak (probably corresponding to various diastereoisomers) of ¹¹¹In-DO3AP^ABn were separated on HPLC. Four peaks were separated by HPLC, they probably correspond to four diastereoisomers of ¹¹¹In-DO3AP^ABn originating from combination of chirality of complexes of DOTA-like ligands with chirality of coordinated phosphorus atom. Studies in rats showed rapid elimination of radioactivity from the blood and other organs and tissues. The results indicate that DO3AP^ABn represents a promising ligand for radiolabeling of target-specific biomolecules with radiometals.     

Les antimonites antiferromagnetiques MnSb2O4 et NiSb2O4

Neutron diffraction has been used to study the variation of antiferromagnetic order in the antimony isomorphous MnSb₂O₄ (T_N ～ 60 K) and NiSb₂O₄ (T_N ～ 46 K). The magnetic moments have been related to the Mn²⁺ and Ni²⁺ spins and magnetostrictive effects have been interpreted. The influence of the method of synthesis is mentioned: polycrystalline MnSb₂O₄ has been obtained from hydrothermal synthesis. Orthorhombic distortions are not connected with magnetic interactions but with structural defects.     

Effect of Proton Transfer on Electrocatalytic Water Oxidation by Manganese Phosphates

The effect of proton transfer on water oxidation has hardly been measurably established in heterogeneous electrocatalysts. Herein, two isomorphous manganese phosphates (NH₄MnPO₄ ⋅ H₂O and KMnPO₄ ⋅ H₂O) were designed to form an ideal platform to study the effect of proton transfer on water oxidation. The hydrogen-bonding network in NH₄MnPO₄ ⋅ H₂O has been proven to be solely responsible for its better activity. The differences of the proton transfer kinetics in the two materials indicate a fast proton hopping transfer process with a low activation energy in NH₄MnPO₄ ⋅ H₂O. In addition, the hydrogen-bonding network can effectively promote the proton transfer between adjacent Mn sites and further stabilize the Mn^III−OH intermediates. The faster proton transfer results in a higher proportion of zeroth-order in [H⁺] for OER. Thus, proton transfer-affected electrocatalytic water oxidation has been measurably observed to bring detailed insights into the mechanism of water oxidation.     

Single crystal circular and linear dichroism spectra and absolute configuration of M(en)3(NO3)2 (M = Zn(II), Cu(II), Ni(II), Co(II), Mn(II) and Ru(II)

The isomorphous single crystals of M(ethylenediamine)₃(NO₃)₂, where M is Zn(II), Ni(II) and Co(II), exhibit macroscopic optical activity as predicted by their acentric space group. Axial circular dichroism measurements on these pure crystals show conclusively that spontaneous resolution has occurred. The axial circular dichroism and orthoaxial linear dichroism spectra of these pure crystals, and of Cu(II), Ni(II), Co(II), Mn(II) and Ru(II) doped into the Zn(en)₃(NO₃)₂ crystal have been measured at ambient and cryogenic temperatures in the range from 7 to 35 kK. The first NO₃^? transition at 32.5 kK is assigned as ¹A ← ¹A based on its linear polarization and sign of rotational strength. The d-d transitions are assigned in the context of D₃ symmetry and reveal a small negative crystal field parameter k, consistent with theoretical prediction. A positive R for all d-d transitions is found to be associated with the Λ configuration for all of the complex ions, by correlation with the crystal and solution circular dichroism of Ru(en)₃²⁺.     

Substituent effects in mass spectra of monosubstituted benzils

The mass spectra of a series of thirteen m- and p-substituted benzils have been determined at several ionising voltages below 20 eV and at 70 eV. At ionising voltages up to 5 eV above the ionisation potentials the benzil molecular ions decompose entirely by two pathways to give substituted and unsubstituted benzoyl ions. Fractional intensities of the molecular ion (F_M), substituted (F_X) and unsubstituted (F_H) benzoyl ions were obtained for each benzil as a function of energy from measured ionisation efficiency curves, and ionisation and appearance potentials for all major ions determined from the ionisation efficiency curves by a semilogarithmic method. Various correlations of ion intensity and energy parameters with δ⁺ and δ constants are examined; these are generally poor. Fair correlations are obtained between log (F_X/F_H) or (AP – AP) and δ or δ⁺, and these are interpreted in terms of the expected effect of substituents on the stabilities of the product ions in the decompositions. A good correlation is observed between log (F_X/F_H) and AP · AP; this suggests that substituents affect F_X/F_H mainly by changing the activation energies for the competing decompositions of the molecular ions. The competitive shift has a marked effect on these appearance potentials so that in this system AP – IP is not a good measure of the activation energy for the primary decompositions.     

Preparation and mössbauer studies of tetraaquabis[maleato(1-)]-iron(II)

Summary Tetraaquabis[maleato(1-)]iron(II), Fe(C₄H₃O₄)₂ · 4H₂O has been synthesised. The compound is monomeric and is isomorphous with the manganese(II) analogue. The temperature dependence of quadrupole splitting and optical spectral data giveca. 10000 cm^–1,ca. 650 cm^–1,ca. 190 cm^–1 andca. 1400 cm^–1 for the 10 Dq, tetragonal field, rhombic field and the splitting of the E_g level, respectively. The quadrupole splitting data indicate that distortion from cubic symmetry increases in the order oxalate < malonate < maleate. DTA, TGA and Mössbauer studies indicate elimination of one molecule of maleic acid at 235 °C. The resulting product shows a less distorted structure and this is attributed to the formation of maleato(2-)iron(II).     

Thermodynamic Study of Cadmium Chloride in Aqueous Mixtures of 2-Butanol from Potential Difference Measurements

The standard molal potential differences (E_m∘) have been determined for the cell: CdHg_x(two phase) | CdCl₂(m), H₂O(1 − w), 2-butanol (w) | AgCl(s) | Ag(s) in aqueous mixtures of low mass fraction of 2-butanol (w_2-butanol = 0.05, 0.10, and 0.15) by using the literature data for the stability constants of the chlorocadmium complexes and the present potentiometric data for this cell at five temperatures from (293.15 to 313.15) K and at 10 molalities of CdCl₂ from (0.002 to 0.02) mol-kg⁻¹. The resulting values of E∘_m have been used to calculate the standard thermodynamic quantities (Δ_rG^∘, Δ_rH^∘, and Δ_rS^∘) for the cell reaction, the stoichiometric mean molal activity coefficients (γ_±) of CdCl₂, and the standard thermodynamic functions for CdCl₂ transfer (Δ_t G∘, Δ_t H∘, and Δ_t S∘) from water to the examined aqueous mixtures of 2-butanol. The values obtained have been compared with the analogous literature data for aqueous mixtures of 2-butanone; standard thermodynamic quantities for transfer of CdCl₂ and HBr from water to mixtures containing the same mass fraction of 2-butanol have also been compared. For both electrolytes, these quantities show analogous trends with the alcohol content. This transfer process is nonspontaneous and endothermic. Enthalpy and entropy are evidently influenced by structural changes.     

Struktur und chemische bindung in dimethylacetamid verbindungen der säuren HPF6, HAsF6 und HSbF6

The compounds (dma)₂HPF₆, (dma)₂HAsF₆ and (dma)₂HSbF₆ (dma = dimethylacetamide) have been investigated by IR, ¹H and ¹⁹F NMR spectroscopy. Spectral data are consistent with the isomorphous crystal structures of (dma)₂HPF₆, and (dma)₂HSbF₆ in which short hydrogen bridges (O·O 2.419(4) and 2.443(7) Å, respectively) are present. The fluorine atoms of the anions display twofold disorder and high thermal motion.     

Die Kristallstruktur von Tetraphenylarsonium-tetrabromooxotechnetat(V), (Ph4As)TcOBr4

The Crystal Structure of Tetraphenylarsonium-tetrabromooxotechnetate(V), (Ph₄As)TcOBr₄ (Ph₄As)TcOBr₄ has been prepared from (Bu₄N)TcO₄, HBr and (Ph₄As)Br. The crystal structure of the complex has been determined by X-ray diffraction using MoKα radiation. The crystals are tetragonal, space group P 4/n with a = 1276.6(1) pm, c = 803.2(1) pm, Z = 2. The refinement based on 1595 reflexes converged to R = 0.034. The structure consists of discrete TcOBr₄^? anions and Ph₄As⁺ cations. The technetium is coordinated in a square pyramidal environment. A C_4v symmetry was derived for the complex anion. With this, it is isomorphous to the other structurally studied (Ph₄As)TcYX₄ complexes (Y = O, N; X = Cl, Br). The Tc = O length is 161.3(9) pm with Tc? Br 246.0(1) pm     

Four faces of the interaction between ions and aromatic rings

Non‐covalent interactions between ions and aromatic rings play an important role in the stabilization of macromolecular complexes; of particular interest are peptides and proteins containing aromatic side chains (Phe, Trp, and Tyr) interacting with negatively (Asp and Glu) and positively (Arg and Lys) charged amino acid residues. The structures of the ion–aromatic‐ring complexes are the result of an interaction between the large quadrupole moment of the ring and the charge of the ion. Four attractive interaction types are proposed to be distinguished based on the position of the ion with respect to the plane of the ring: perpendicular cation–π (CP_⊥), co‐planar cation–π (CP_∥), perpendicular anion–π (AP_⊥), and co‐planar anion–π (AP_∥). To understand more than the basic features of these four interaction types, a systematic, high‐level quantum chemical study is performed, using the X^– + C₆H₆, M⁺ + C₆H₆, X^– + C₆F₆, and M⁺ + C₆F₆ model systems with X⁻ = H⁻, F⁻, Cl⁻, HCOO⁻, CH₃COO⁻ and M⁺ = H⁺, Li⁺, Na⁺, , CH₃ , whereby C₆H₆ and C₆F₆ represent an electron‐rich and an electron‐deficient π system, respectively. Benchmark‐quality interaction energies with small uncertainties, obtained via the so‐called focal‐point analysis (FPA) technique, are reported for the four interaction types. The computations reveal that the interactions lead to significant stabilization, and that the interaction energy order, given in kcal mol⁻¹ in parentheses, is CP_⊥ (23–37) > AP_⊥ (14–21) > CP_∥ (9–22) > AP_∥ (6–16). A natural bond orbital analysis performed leads to a deeper qualitative understanding of the four interaction types. To facilitate the future quantum chemical characterization of ion–aromatic‐ring interactions in large biomolecules, the performance of three density functional theory methods, B3LYP, BHandHLYP, and M06‐2X, is tested against the FPA benchmarks, with the result that the M06‐2X functional performs best. © 2017 Wiley Periodicals, Inc.     

Raman spectra,Pippard relations and critical exponents for NH4Cl

The Pippard relations have been extended to correlate the vibrational frequency shifts with the relevant thermodynamic quantities in the vicinity of the λ-point in NH₄Cl. It has been shown that they describe the NH₄Cl system adequately below its λ-transition temperature. (T_λ = 242.8 K). This has been examined using our temperature-dependent frequency data for the ν₅ (174 cm^?1) Raman mode of NH₄Cl at zero pressure by means of the equations developed. The slope of the λ-transition line. (dP/dT)_λ that has been calculated from these equations, is in good agreement with those obtained by previous workers. We have deduced the critical exponents a′ and c′ for the thermal expansion and the isothermal compressibility of NH₄Cl from our temperature and pressure-dependent frequency data for the ν₅ mode. We have identified our exponent value for the thermal expasion with the specific heat exponent, a′, (Pippard relation) to demonstrate the scaling law a′+2b+c′=2, using our value of the critical exponent b for the order parameter from our previous work on NH₄Cl.     

Synthesis of bimetallic complexes based on acetylacetonates of aluminum and ferrum. Crystalline structure Al0.9Fe0.1(acac)3

X-Ray diffraction analysis of cocrystallization of Al(acac)₃ and Fe(acac)₃ in a broad range of compositions has been performed. It has been established that in the ratio Al:Fe ～0.9:0.1 bi metallic phases are formed, isostructural to γ-Al(acac)₃. The crystalline structure of Al_0.9Fe_0.1(acac)₃ has been determined (autodiffractometer X8 APEX Bruker, MoK _α-radiation), crystallographic data: a = 15.709(1) Å, b = 32.637(3) Å, c = 13.388(1) Å, V = 6863.9(9) ų, space group Pna2₁, Z = 16, d _calc = 1.264 g/cm³. The parameters of the elementary cell Al_0.5Fe_0.5(acac)₃ have been refined (diffractometer DRON-RM4, CuK _α-radiation, Ni-filter). It is shown that the values V/Z are regularly increasing with increased content of Fe. The product of thermolysis Al_0.5Fe_0.5(acac)₃ is monophase and isostructural to γ-Fe₂O₃.     

Synthesis and Application of a Perfluorinated Ammoniumyl Radical Cation as a Very Strong Deelectronator

The perfluorinated dihydrophenazine derivative (perfluoro‐5,10‐bis(perfluorophenyl)‐5,10‐dihydrophenazine) (“phenazine^F”) can be easily transformed to a stable and weighable radical cation salt by deelectronation (i.e. oxidation) with Ag[Al(OR^F)₄]/ Br₂ mixtures (R^F=C(CF₃)₃). As an innocent deelectronator it has a strong and fully reversible half‐wave potential versus Fc⁺/Fc in the coordinating solvent MeCN (E°′=1.21 V), but also in almost non‐coordinating oDFB (=1,2‐F₂C₆H₄; E°′=1.29 V). It allows for the deelectronation of [Fe^IIICp*₂]⁺ to [Fe^IV(CO)Cp*₂]²⁺ and [Fe^IV(CN‐^tBu)Cp*₂]²⁺ in common laboratory solvents and is compatible with good σ‐donor ligands, such as L=trispyrazolylmethane, to generate novel [M(L)_x]ⁿ⁺ complex salts from the respective elemental metals.     

Co-crystallization of ultramicro quantities of cobalt with α-nitroso-β-naphthol

The co-crystallization of ultramicro quantities of cobalt with α-nitroso-β-naphthol, was investigated by radio-tracer techniques. More than 99% cobalt, even when carrier-free, could be recovered. The distribution was studied and appeared to follow the logarithmic distribution law. The interference of a large excess of zinc was almost negligible. The method was applied to tlie carrier-free separation of cobalt isotopes (⁵⁵Co, ⁵⁶Co, ⁵⁷Co, ⁵⁸Co) produced by deuteron bombardment of an iron target. Contamination by manganese (⁵⁴Mn, ⁵²Mn) and iron (⁵⁹Fe) was, even in the absence of manganese carrier, almost negligible.