Titrimetric analysis with adding the titrant by means of electrodialysis

A titration method is developed that titrant is added continuously to the analyte by electromigration through an ion exchange membrane. A constant rate of the titrant addition is achieved by keeping the electric current constant. Analyte amount then is proportional to the titration time. The method is applied to the most widely used titrations with a visual end point indication.     

A New Type of Anionic Framework in Microporous Potassium Iron(II) Phosphate K[Fe(PO4)]

A new iron(II) orthophosphate K[Fe(PO₄)] has been obtained by hydrothermal synthesis and its crystal structure was determined by single‐crystal X‐ray diffraction: space group P2₁/n, Z = 8, a = 9.6199(10), b = 8.6756(8), c = 10.8996(13) Å, β = 115.577(8)° at 193 K, R = 0.023. Fe^II shows coordination numbers (CN) 4 (distorted tetrahedral) and CN 5 (distorted trigonal bipyramidal). The [FeO₄] and [FeO₅] units form together with the [PO₄] tetrahedra a microporous 3D para‐framework with open channels along the a and b directions. The potassium ions positioned in the channels show CN 7 and 8. The structural relations within the morphotropic row of non‐isotypic K[M(PO₄)] structures (M = Zn, Ni, Mn, Fe) are discussed on the basis of common basic structural units.     

Lupane-triterpenes from Bupleurum flavum

Two new triterpenoids, lup-20(29)-en-3 alpha, 28-diol (1) and lup-20(29)-en-3 alpha, 28,30-triol (2), have been isolated from aerial parts of Bupleurum flavum, a native plant of the Eastern Mediterranean area (Bulgaria, Greece, and Turkey). Their structures were elucidated by spectral analysis. The known compounds betulin, betulinic acid, jasminol, together with the lignan nemerosin and eight flavonoids (kaempferol, isokaempferide, gossipetin, quercetin, luteolin, isorhamnetin 3-O-beta-D-glucopyranoside, isorhamnetin 3-rutinoside, and rutin) were also characterized.     

A stepwise approach for defining the applicability domain of SAR and QSAR models

A stepwise approach for determining the model applicability domain is proposed. Four stages are applied to account for the diversity and complexity of the current SAR/QSAR models, reflecting their mechanistic rationality (including metabolic activation of chemicals) and transparency. General parametric requirements are imposed in the first stage, specifying in the domain only those chemicals that fall in the range of variation of the physicochemical properties of the chemicals in the training set. The second stage defines the structural similarity between chemicals that are correctly predicted by the model. The structural neighborhood of atom-centered fragments is used to determine this similarity. The third stage in defining the domain is based on a mechanistic understanding of the modeled phenomenon. Here, the model domain combines the reliability of specific reactive groups hypothesized to cause the effect and the domain of explanatory variables determining the parametric requirements in order for functional groups to elicit their reactivity. Finally, the reliability of simulated metabolism (metabolites, pathways, and maps) is taken into account in assessing the reliability of predictions, if metabolic activation of chemicals is a part of the (Q)SAR model. Some of the stages of the proposed approach for defining the model domain can be eliminated depending on the availability and quality of the experimental data used to derive the model, the specificity of (Q)SARs, and the goals of their ultimate application. The performance of the proposed definition of the model domain is tested using several examples of (Q)SARs that have been externally validated, including models for predicting acute toxicity, skin sensitization, and biodegradation. The results clearly showed that credibility in predictions of QSAR models for chemicals belonging to their domain is much higher than for chemicals outside this domain.     

Dimerization of n-butenes on nickel mordenite catalysts

The catalytic activity of synthetic and natural nickel exchanged mordenites of different compositions has been investigated in dimerization of n-butenes at high pressure in the liquid phase. High selectivities to n-octenes and methylheptenes were found. It is suggested that the mordenite channel structure influences the product distribution.

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Crystal structure of Rb<Subscript>2</Subscript>Mn<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>[P<Subscript>2</Subscript>O<Subscript>7</Subscript>]<Subscript>2</Subscript>, a new representative of the family of hydrated diphosphates

The crystal structure of Rb₂Mn₃(H₂O)₂[P₂O₇]₂, a new phase obtained in the form of single crystals under hydrothermal conditions in the MnCl₂–Rb₃PO₄–H₂O system, is determined by X-ray diffraction (Xcalibur-S-CCD diffractometer, R = 0.0270): a = 9.374(2), b = 8.367(2), c = 9.437(2) Å, ß = 99.12(2)°, space group P2₁/c, Z = 2, D_x = 3.27 g/cm³. A correlation between the unit-cell parameters and the size of cations forming the crystal structures of isostructural A₂M₃(H₂O)₂[P₂O₇]₂ diphosphates (A = K, NH₄, Rb, or Na; _M = Mn, Fe, Co, or Ni) is revealed. It is shown that, due to the topological similarity, the structures of diphosphates and orthophosphates of the farringtonite structural type can undergo mutual transformations.     

12‐Membered borophosphate rings in KNi5[P6B6O23(OH)13]

The title compound, potassium pentanickel hexaborophosphate tridecahydroxide, was synthesized under hydrothermal conditions from the NiCl₂–K₃PO₄–B₂O₃–K₂CO₃–H₂O system. The crystal structure was determined using single‐crystal X‐ray diffraction at 100 K. The KNi₅[P₆B₆O₂₃(OH)₁₃] phase is cubic. For the three crystallographically distinct Ni centers, two occupy sites with 3 symmetry, while the third Ni and the K atom are located on sites. The structure is built from alternating borate and phosphate tetrahedra forming 12‐membered puckered rings with K⁺ ions at the centers. These rings are arranged as in cubic dense sphere packing. A novel feature of the new crystal structure is the presence of linear trimers of face‐sharing [NiO₆] octahedra occupying the octahedral interstices of this sphere packing, and of single [NiO₆] octahedra in the tetrahedral interstices. All oxygen corners of the Ni octahedra are linked to phosphate or borate tetrahedra of the 12‐membered rings to form a mixed anionic framework.     

New Lead Orthosilicate {Pb4(О(ОН)2)}[SiO4] with a Framework of Anion-Centered Pb Tetrahedra Related to Sodalite

Crystallography Reports - New lead silicate {Pb4(О(ОН)2)}[SiO4] was synthesized under hydrothermal conditions and structurally characterized, sp. gr. P213, а = 8.9756(13)...     

Charge-transfer photolysis of copper(II) dithiocarbamate mixed-ligand complexes in toluene/alcohol solutions

Charge-transfer (CT)-photolysis of Cu(II) dithiocarbamate mixed-ligand complexes Cu(II)(Et2dtc)X (X = Cl-, Br-) and Cu(II)(Et2dtc)(+)...Y- (Y = ClO4-, NO3-) has been studied in toluene/ROH and compared with our previous data obtained in chloromethane/ROH solutions, where chloromethane = CCl4, CHCl3 or CH2Cl2 and ROH = MeOH, EtOH, i-PrOH or i-BuOH. An EPR evidence is obtained about the formation of a new copper(II) dithiocarbamate mixed-ligand complex during simultaneous photolyses of Cu(II)(Et2dtc)+ and Cu(II)(Et2dtc)2 species in toluene/ROH. The role of the solvent is discussed from the combined analysis of spectrophotometric and EPR data and quantum yield results.