Synthesis and molecular structure of new O/N/O ligands: Bis-phenol-pyridine and bis-phenol-pyrazole

Crystal structure of 2,6-bis(2-hydroxy-5-methylphenyl)-4-phenylpyridinium bromide dichloromethane hemisolvate hemihydrate

The asymmetric unit in the structure of the title compound, C₂₅H₂₂NO₂⁺·Br ⁻·0.5CH₂Cl₂·0.5H₂O, comprises two pseudosymmetry-related cations, two bromide anions, a di­chloro­methane molecule and a water mol­ecule of solvation. The two independent cations are conformationally similar with the comparative dihedral angles between the central pyridine ring and the three benzene substituent rings being 3.0 (2), 36.4 (1) and 24.2 (1)°, and 3.7 (2), 36.5 (1) and 24.8 (1)°, respectively. In the crystal, the cations, anions and water mol­ecules are linked through O—H⋯O and O—H⋯Br hydrogen bonds, forming an insular unit. Within the cations there are also intra­molecular N—H⋯O hydrogen bonds. Adjacent centrosymmetrically related aggregates are linked by π–π stacking inter­actions between the pyridine ring and a benzene ring in both cations [ring-centroid separations = 3.525 (3) and 3.668 (3) Å], forming chains extending across the ac diagonal. Voids between these chains are filled by dichloromethane molecules.

Synthesis and biological evaluation of novel pyrazole derivatives with anticancer activity

We synthesized thirty-six novel pyrazole derivatives and studied their antiproliferative activity in human ovarian adenocarcinoma A2780 cells, human lung carcinoma A549 cells, and murine P388 leukemia cells. Four of these substances were selected because of their higher antiproliferative activity and further analyses showed that they were all able to induce apoptosis, although to a different extent. The expression of p53 and p21(waf1), which induce apoptosis and cell cycle arrest, was evaluated by western blot analysis in cells treated with compound 12d. The analysis of the cell cycle showed that all the selected compounds cause a partial G2/M block and the formation of polyploid cells. Furthermore, the four selected compounds were tested for their interaction with the microtubular cytoskeletal system by docking analysis, tubulin polymerization assay and immunofluorescence staining, demonstrating that the compound 12d, unlike the other active derivatives, was able to significantly bind dimers of α- and β-tubulin, probably causing a molecular distortion resulting in the disassembly of microtubules.

Bis[2,6-bis-(2-meth-oxy-phen-yl)pyridinium] di-μ-bromido-bis-[dibromidocuprate(II)]

The title salt, (C₁₉H₁₈NO₂)₂[Cu₂Br₆], was obtained from an attempt to synthesize the copper(II) complex of 2,6-bis­(2-meth­oxy­phen­yl)pyridine (L) from a reaction between CuBr₂ and one equivalent of L in CH₂Cl₂ at room temperature. The resulting compound is the salt of the 2,6-bis­(2-meth­oxy­phen­yl)pyridinium cation and 0.5 equivalents of a hexa­bromido­dicuprate(II) dianion. Both meth­oxy groups of the cationic pyridinium moiety are directed towards the N atom of the pyridine ring as a result of intra­molecular N—H⋯O hydrogen bonds. The centrosymmetric hexabromidodicuprate dianion possesses a distorted tetra­hedral geometry at the copper ion. The Cu—Br bond lengths are 2.3385 (7) and 2.3304 (7) Å for the terminal bromides, whereas the bond length between the Cu atom and two bridging bromides is slightly longer [2.4451 (6) Å].

Neutron and X-ray Diffraction and Spectroscopic Investigations of Intramolecular [CH⋅⋅⋅FC] Contacts in Post-Metallocene Polyolefin Catalysts: Modeling Weak Attractive Polymer–Ligand Interactions

A family of Group 4 post-metallocene catalysts, supported by fluorine-functionalized tridentate ligands with the fluorine substituent in the locality of the metal center, is described. For the first time, the contentious C-H...F-C interaction has been characterized by a neutron diffraction study, which has allowed the position of the hydrogen atoms to be accurately determined. The nature of the weak intramolecular C-H...F-C contacts in these complexes in solution and the solid state was probed by using multinuclear NMR spectroscopy in tandem with neutron and X-ray crystallography. Evidence is presented to demonstrate that the spectroscopic C-H...F-C coupling occurs "through-space" rather than "through-bond" or by MF coordination. The titanium catalysts exhibit excellent activities and high co-monomer incorporation in olefin polymerization. The observed intramolecular C-H...F-C interactions are important with regards to potential applications in polyolefin catalysis because they substantiate the proposed ortho-F...H(beta) ligand-(polymer chain) contacts derived from DFT calculations for the remarkable fluorinated phenoxyimine Group 4 catalysts. Compared with agostic and co-catalyst...metal contacts, weak attractive noncovalent interactions between a polymer chain and a judiciously designed "active" ligand is a new concept in polyolefin catalysis.