Crystal structure, electronic properties and cytotoxic activity of palladium chloride complexes with monosubstituted pyridines

Palladium(II) complexes attract great attention due to their remarkable catalytic and biological activity. In the present study X-ray characterization, UV-Vis and Time-Dependent Density Functional Theory (TD-DFT) calculations for six PdCl(2)(XPy)(2) complexes (where: Py = pyridine; X = H, CH(3) or Cl) were applied in order to investigate substituent effects on their crystal structures and electronic properties and to combine the results with their catalytic and cytotoxic activity. The structures of complexes PdCl(2)(3-MePy)(2), PdCl(2)(4-MePy)(2) and PdCl(2)(2-ClPy)(2), have been described for the first time and we compared our results with available data for the whole series of six complexes. All compounds exhibit a square planar coordination geometry in which the palladium ion coordinates two nitrogen atoms of pyridine ligands and two chlorine atoms in trans positions. For complexes with ortho substituted XPy ligands a cis disposition of substituents takes place, whereas for other ligands: 3-MePy and 3-ClPy--the substituents are in trans positions. For XPy the energies of π-π* and n-π* transitions depend on the position and nature of the X substituent in the XPy ring. After complex formation a hipsochromic shift (24-34 nm) of π-π* and a bathochromic shift of n-π* bands are observed. The UV-Vis spectra of PdCl(2)(XPy)(2) confirm that square planar coordination geometry of complexes I-VI and two dπ-π* transitions are expected. With the help of the TD-DFT calculations we proved that dπ-π* transitions in solutions of PdCl(2)(XPy)(2) complexes result from MLCT (metal-to-ligand charge transfer) with contribution from chlorine atoms to palladium. We also studied substituent effects on cytotoxic properties of Pd(II) complexes against the human breast cancer cell line MCF7, the human prostate cancer cell line PC3, and the human T-cell lymphoblast-like cell line CCRF. The studied complexes were the most active against the CCRF cell line and less or even no cytotoxic effect was observed for PC3 cells. Complexes with MePy ligands showed increased cytotoxic activity compared to unsubstituted pyridine ligands.     

Enhanced mobility in P3HT-based OTFTs upon blending with a phenylene-thiophene-thiophene-phenylene small molecule

An enhancement in charge transport capacity in a poly(3-hexylthiophene) (P3HT) semicrystalline film, up to field-effect mobilities approaching 0.1 cm(2) V(-1) s(-1), has been achieved by co-deposition with a small molecule, i.e. 5,5'-bis(4-n-hexylphenyl)-2,2'-bithiophene (dH-PTTP), forming highly ordered crystals bridging large polymeric domains.     

On the stability of single-walled carbon nanotubes and their binding strengths

The series of rhenium (I) tricarbonyl mixed-ligand complexes ReCl(CO)₃(H_nbpydt) (n?=?2, 1; n?=?4, 2; bpy?=?bispyridine, dt?=?1,3-dithiole) and ReCl(CO)₃(H_nbpyTTF) (n?=?2, 3; n?=?3, 4; TTF?=?Tetrathiafulvalene) have been investigated theoretically to explore the effect of COOH functional group on their electronic structures, spectroscopic properties and their properties as dye in a solar cell. The calculated geometry structure and absorption spectrum of 1 and 3 are generally consistent with the experimental results. By attaching the COOH groups on both bpy and dt (TTF in 4) moiety in 2, the nature of LUMO is also contributed by both π*(bpy) and π*(dt) (π*(TTF) in 4), and the absorptions have an obvious red shift compared with 1 and 3. In addition, it can be found that the transition terminates at the orbital populated by the COOH-appended moieties, and the performance of 2 and 4 in the dye-sensitized solar cell can be enhanced as compared with 1 and 3.     

Insights from impedance spectroscopy into the mechanism of thermal decomposition of M(NH2BH3), M = H, Li, Na, Li(0.5)Na(0.5), hydrogen stores

We report the first solid-state impedance study of hydrogen-rich ammonia borane, AB, and its three alkali metal amidoborane derivatives. Temperature-dependent impedance spectra of solid M(NH(2)BH(3)) salts are predominated by ionic conductivity, which at room temperature ranges from 5.5 μS cm(-1) (M = Li) to 2.2-3.0 mS cm(-1) (Na, Na(0.5)Li(0.5)), while the activation energy for conductivity is rather high (140-158 kJ mol(-1)). Variation of conductivity with time can be used to extract information about the evolution of the system during thermal decomposition. By using a combination of impedance spectroscopy, thermogravimetric analysis, scanning calorimetry, evolved gas analysis, infrared absorption spectroscopy as well as (11)B and (1)H MAS NMR, we were able to reconfirm the complex pathway of thermal decomposition of amidoboranes postulated by two of us earlier (J. Mater. Chem. 2009, 19, 2043).     

On series of signed vectors and their rearrangements

Let x₁,…,x_m∈ \input amssym $ \Bbb R$ n be a sequence of vectors with ∥x_i∥₂ ≤ 1 for all i. It is proved that there are signs ε₁,…,ε_m = ±1 such that where C₁, C₂ are some numerical constants. It is also proved that there are signs ε,…,ε = ±1 and a permutation π of {1,…,m} such that where C^′ is some other numerical constant. © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 2011     

New Metal–Organic Framework Solids Built from Barium and Isoelectronic Chelidamic and Chelidonic Acids

Abstract  

Two new Ba(II) metal–organic framework solids bearing the chelidamate [Ba₂(C₇H₃NO₅)₂(μ-H₂O)(H₂O)₆]·2H₂O (1) and chelidonate [Ba(C₇H₂O₆)(H₂O)] (2) ligands were synthesized and characterized by IR, elemental, thermal, photoluminescent and X-ray diffraction analyses. In complex 1 the chelidamate dianion exists in two tautomeric forms, in which the enol form exhibits unprecedented (К¹, К¹) (К¹) (К², К², μ₂, μ₂)-μ₇ heptadentate coordination while the keto form with (К¹, К¹)(К²)-μ₄ tetradentate mode. It is a 2D polymer in which the first and second dimensions are satisfied by carboxylate oxygens while the third is by the combination of hydrogen bonds and π–π stacking of aromatic rings. There are two independent barium ions (Ba1, Ba2) in complex 1 that are nine coordinated, but their coordination environment is different. Complex 2 is a 3D polymer and the organic linker, 4-oxo-pyran-2,6-dicarboxylate (chelidonate) anion exhibits denticity as seven with barium having the similar nine coordination.     

Columnar Mesophase Formation of Cyclohexa‐m‐phenylene‐Based Macrocycles

Two novel discotic macrocycles, substituted cyclohexa‐m‐phenylene (CHP) and cyclo‐3,6‐trisphenanthrylene (CTP), and the linear oligomer 3,3′:6′,3′′‐terphenanthrene (TP) as a model substance have been synthesized by repetitive cross‐coupling reactions. To correlate the molecular design with the supramolecular architecture and the established macroscopic order, 2D wide‐angle X‐ray scattering experiments were performed on mechanically extruded filaments. At room temperature in their crystalline phases, all three compounds revealed columnar assemblies in which the macrocycles self‐organized by π‐stacking interactions. The degree of macroscopic order was found to depend upon the planarity and stiffness of the aromatic core. The flexible CHP ring showed a poor macroscopic order of the columnar structures and a low isotropization temperature, whereas the more‐planar, less‐flexible CTP self‐assembled into well‐defined superstructures. The larger π‐stacking area and the more‐pronounced intermolecular interactions for CTP led to the formation of a mesophase over a very large temperature range. The surprising columnar organization of the “open” TP system was explained by back‐folding of the molecule into a ringlike structure.     

Molecular Triangles: Synthesis,Self‐Assembly,and Blue Emission of Cyclo‐7,10‐tris‐triphenylenyl Macrocycles

A set of cyclo‐7,10‐tris‐triphenylenyl macrocycles have been prepared by a Yamamoto cyclotrimerization protocol. In these novel macrocycles, three triphenylene units are covalently linked to each other, resulting in the formation of triangular‐shaped molecules. The fully planar derivative revealed pronounced self‐assembly behavior. NMR spectroscopy was used to determine the association constant in solution. 2D wide‐angle X‐ray scattering was applied to the study of the liquid crystallinity of this new discotic mesogen in the bulk state. Furthermore, nonplanar, laterally substituted derivatives were successfully tested as blue emitters in organic light‐emitting diodes owing to their unique optoelectronic properties and their high stability. In this case, substitution with sterically demanding phenyl groups was efficiently used to suppress intermolecular packing, thus preventing undesired quenching effects.     

The role of carboxylate ligands in two novel cyanido-bridged 2D coordination networks Cu(II)-W(V) and Mn(II)-Nb(IV)

We report on the synthesis, molecular structure and magnetic properties of two novel coordination polymers: [{Cu(II)(4)(pic)(2)(H(2)O)(2)(MeOH)}{W(V)(CN)(8)}(2)]·MeOH·4H(2)O (1) and [{Mn(II)(3)(HCOO)(2)(H(2)O)(4)}{Mn(II)(H(2)O)(3)(HCONH(2))}(2){Nb(IV)(CN)(8)}(2)]·4HCONH(2)·2H(2)O (2). The single-crystal X-ray diffraction analysis of 1 shows that its molecular structure can be interpreted as a cyanido bridged (3,4,7)-connected 2D bilayer built of two different subnets sharing the tungsten centers. The magnetic measurements suggest that the system reveals long-range ferromagnetic ordering between Cu(II) and W(V) centers below 13.4 K. The molecular structure of (2) reveals a 2D topology of layers built of cyanido and formato bridging ligands. The system reveals ferrimagnetic behavior with a critical temperature at 17.8 K.