Synthesis,Structures, and Properties of Layered Quaternary Chalcogenides of the General Formula ALnEQ4 (A = K,Rb; Ln = Ce,Pr, Eu; E = Si,Ge; Q = S,Se)

Four related quaternary compounds containing rare‐earth metals have been synthesized employing the molten flux method and metathesis. The reactions of Eu and Rb₂S₅ with Si and Ge in evacuated fused silica ampoules at 725 °C for 150 h yielded RbEuSiS₄ ( I ) and RbEuGeS₄ ( II ), respectively. On the other hand, a reaction between CeCl₃ and K₄Ge₄Se₁₀ at 650 °C for 148 h has yielded KCeGeSe₄ ( III ) and KPrSiSe₄( IV ) was obtained by the reaction of elemental Pr, Si and Se in KCl flux at 850 °C for 168 h. Crystal data for these compounds are as follows: I , orthorhombic, space group P2₁2₁2₁ (#19), a = 6.392(1), b = 6.634(2), c = 17.001(3) Å, α = β = γ = 90°, Z = 4; II , monoclinic, space group P2₁/m (#11), a = 6.498(2), b = 6.689(3), c = 8.964(3) Å, β = 108.647(6)°, Z = 2; III , monoclinic, space group P2₁ (#4), a = 6.852(2), b = 7.025(2), c = 9.017(3) Å, β = 108.116(2)°, Z = 2; IV , monoclinic, space group P2₁ (#4), a = 6.736(2), b = 6.943(2), c = 8.990(1) Å, β = 108.262(2)°, Z = 2. The crystal structures of I ‐ IV contain two‐dimensional corrugated anionic layers of the general formula, [LnEQ₄]^? (Ln = Ce, Pr, Eu; E = Si, Ge and Q = S, Se) alternately piled upon layers of alkali cations. In addition to structural elucidation, Raman and UV‐visible spectroscopy, and magnetic measurements for compound III (KCeGeSe₄) are also discussed.     

The Diammoniates of dipotassiumtetraethinylozincate and -cadmate: K2M(C2H)4.2NH3 (M = Zn, Cd)

By reaction of KC(2)H and K(2)Zn(CN)(4) in liquid ammonia, the diammoniate K(2)Zn(C(2)H)(4).2NH(3) was obtained. K(2)Cd(C(2)H)(4).2NH(3) was synthesized by reacting KC(2)H, Cd(NH(2))(2), and acetylene in liquid ammonia. The crystal structures of the air and temperature sensitive compounds were determined by X-ray single crystal diffraction at low temperatures (T = 170 K). Both compounds crystallize in the monoclinic space group I2/a (No. 15) with Z = 4. K(2)Zn(C(2)H)(4).2NH(3): a = 7.289(1) A, b = 12.765(2) A, c = 14.066(2) A, beta = 98.11(2) degrees. K(2)Cd(C(2)H)(4).2NH(3): a = 7.444(1) A, b = 12.619(3) A, c = 14.304(2) A, beta = 98.94(1) degrees. Characteristic structural motifs are tetrahedral [M(C(2)H)(4)](2-) fragments (M = Zn, Cd) and zigzag chains of edge sharing distorted (C(2)H)(6) octahedra centered by potassium ions. These zigzag chains are connected by a second type of crystallographically distinct potassium ions that also bind to two ammonia molecules.     

Pharmacophore features of potential drugs

Drug discovery efforts rely increasingly on the identification of quality lead compounds through high-throughput synthesis and screening. However, large-scale random libraries have yielded only a low number of quality lead molecules. To address this shortcoming researchers have paid more attention to the concept of "drug-likeness" of molecules in combinatorial and screening libraries. Database profiling and analysis methods have been employed to identify the structural features of known drug molecules. Neural networks and machine learning methods help to distinguish between drugs and nondrugs. More recently, database-independent pharmacophore filters have been introduced that provide simple intuitive rules to classify potential drugs.     

Dinuclear and Mononuclear Platinum(II) and Palladium(II) Complexes with Modified 2,2′‐Dipyridylamine Ligands Featuring a Cisplatin Analogous Structure Motif

In modern cancer therapy the clinical application of platinum‐based drugs is more and more limited by the occurrence of intrinsic or acquired resistances. In this context the potential use of dinuclear platinum complexes in chemotherapy is increasingly relevant. The novel complexes Pd(Bzdpa)Cl₂, Pd₂(C₄H₈(dpa)₂)Cl₄, and Pt₂(C₄H₈(dpa)₂)Cl₄ allow a direct comparison of mono‐ and dinuclear palladium and platinum complexes respectively deriving from a 2,2′‐dipyridylamine (Hdpa) ligand system. They were characterized by single crystal X‐ray analysis as well as infrared spectroscopy and elemental analysis. The cisplatin analogous mononuclear palladium complex Pd(Bzdpa)Cl₂ ( 1 ) (Bzdpa: (2,2′‐dipyridylbenzyl)amine) belongs to a range of 2,2′‐dipyridylamine‐based compounds which were extensively studied in our laboratories. 1 crystallizes in the orthorhombic space group Pna2₁ with a = 13.722(3), b = 13.457(3), c = 9.483(2), V = 1751.1(6) ų, and Z = 4. The metal binding motif of 1 was expanded by a flexible butyl‐linker to form the tetradentate C₄H₈(dpa)₂ ligand. The resulting isotypic dinuclear complexes Pd₂(C₄H₈(dpa)₂)Cl₄·2CH₃CN ( 2 ) and Pt₂(C₄H₈(dpa)₂)Cl₄·2CH₃CN ( 3 ) crystallize in the triclinic space group with a = 7.8427(2), b = 8.7940(2), c = 11.7645 (3), α = 79.219(2)°, β = 84.033(2)°, γ = 87.744(2)°, V = 792.58(3) ų ( 2 ) and a = 7.831(5), b = 8.814(5), c = 11.817(5), α = 79.271(5)°, β = 83.571(5)°, γ = 88.063(5)°, V = 796.3(8) ų ( 3 ), both with one centrosymmetrical molecule in the unit cell.     

Strukturen von Bis(trifluormethyl)halogeno‐ und ‐thiocyanato‐mercuraten, [Hg(CF3)2X]— (X = Br,I, SCN), und ein Vergleich der Strukturparameter der CF3‐Gruppen

Structures of Bis(trifluoromethyl)halogeno and thiocyanato Mercurates, [Hg(CF₃)₂X]^— (X = Br, I, SCN), and a Comparison of the Structural Parameters of the CF₃ Groups [(18‐C‐6)K]₂[Hg(CF₃)₂SCN]₂ (1) and [P(CH₃)(C₆H₅)₃]₂[Hg(CF₃)₂X]₂ (X = Br (2) , I (3) ) are prepared and their crystal structures are determined. [(18‐C‐6)K]₂[Hg(CF₃)₂SCN]₂ (1) crystallizes in the monoclinic space group P2₁/c with Z = 2, [P(CH₃)(C₆H₅)₃]₂[Hg(CF₃)₂Br]₂ (2) in the monoclinic space group P2₁/n with Z = 2 and [P(CH₃)(C₆H₅)₃]₂[Hg(CF₃)₂I]₂ (3) in the triclinic space group P1¯ with Z = 1. In the solid state the three compounds form dimeric anions with planar Hg₂X₂ rings. The structural parameters of the Hg(CF₃)₂ units in the till now known bis(trifluoromethyl)halogeno mercurates are compared. In all compounds one nearly symmetric and one distorted CF₃ group exist. The largest differences of the C—F bond lengths is found for [(18‐C‐6)K][Hg(CF₃)₂I]. This can be regarded as the experimental evidence for the properties of trifluoromethyl mercury compounds to act as excellent difluorocarbene sources in the presence of alkali iodides.     

Evaluation of docking/scoring approaches: A comparative study based on MMP3 inhibitors

An increasing number of docking/scoring programs are available that use different sampling and scoring algorithms. A reliable scoring function is the crucial element of such approaches. Comparative studies are needed to evaluate their current capabilities. DOCK4 with force field and PMF scoring as well as FlexX were used to evaluate the predictive power of these docking/scoring approaches to identify the correct binding mode of 61 MMP-3 inhibitors in a crystal structure of stromelysin and also to rank them according to their different binding affinities. It was found that DOCK4/PMF scoring performs significantly better than FlexX and DOCK4/FF in both ranking ligands and predicting their binding modes. Most notably, DOCK4/PMF was the only scoring/docking approach that found a significant correlation between binding affinity and predicted score of the docked inhibitors. However, comparing only those cases where the correct binding mode was identified (scoring highest among sampled poses), FlexX showed the best `fine tuning' (lowest rmsd) in predicted binding modes. The results suggest that not so much the sampling procedure but rather the scoring function is the crucial element of a docking program.     

Measurements and Utilization of Consistent Gibbs Energies of Transfer of Single Ions: Towards a Unified Redox Potential Scale for All Solvents

Utilizing the “ideal” ionic liquid salt bridge to measure Gibbs energies of transfer of silver ions between the solvents water, acetonitrile, propylene carbonate and dimethylformamide results in a consistent data set with a precision of 0.6 kJ mol⁻¹ over 87 measurements in 10 half-cells. This forms the basis for a coherent experimental thermodynamic framework of ion solvation chemistry. In addition, we define the solvent independent - and the values that account for the electronating potential of any redox system similar to the value of a medium that accounts for its protonating potential. This scale is thermodynamically well-defined enabling a straightforward comparison of the redox potentials (reducities) of all media with respect to the aqueous redox potential scale, hence unifying all conventional solvents′ redox potential scales. Thus, using the Gibbs energy of transfer of the silver ion published herein, one can convert and unify all hitherto published redox potentials measured, for example, against ferrocene, to the scale.