High Catalytic Activity of Heterometallic (Fe6Na7 and Fe6Na6) Cage Silsesquioxanes in Oxidations with Peroxides

International audienceTwo types of heterometallic (Fe(III),Na) silsesquioxanes—[Ph5Si5O10]2[Ph10Si10O21]Fe6(O2‒)2Na7(H3O+)(MeOH)2(MeCN)4.5.1.25(MeCN), I, and [Ph5Si5O10]2[Ph4Si4O8]2Fe6Na6(O2‒)3(MeCN)8.5(H2O)8.44, II—were obtained and characterized. X-ray studies established distinctive structures of both products, with pair of Fe(III)-O-based triangles surrounded by siloxanolate ligands, giving fascinating cage architectures. Complex II proved to be catalytically active in the formation of amides from alcohols and amines, and thus becoming a rare example of metallasilsesquioxanes performing homogeneous catalysis. Benzene, cyclohexane, and other alkanes, as well as alcohols, can be oxidized in acetonitrile solution to phenol—the corresponding alkyl hydroperoxides and ketones, respectively—by hydrogen peroxide in air in the presence of catalytic amounts of complex II and trifluoroacetic acid. Thus, the cyclohexane oxidation at 20 °C gave oxygenates in very high yield of alkanes (48% based on alkane). The kinetic behaviour of the system indicates that the mechanism includes the formation of hydroxyl radicals generated from hydrogen peroxide in its interaction with di-iron species. The latter are formed via monomerization of starting hexairon complex with further dimerization of the monomer

Phase Transformation in UHMWPE Reactor Powders Synthesized on Various Catalysts in Mechanical and Thermal Fields

Nowadays, a solvent-free method for production of high performance fibers directly from ultrahigh-molecular-weight polyethylene (UHMWPE) reactor powder is being actively developed. It causes the interest in the morphology of the reactor particles and their behavior in thermal and mechanical fields. Changes in the phase composition in virgin particles of ultra-high molecular-weight polyethylene reactor powders and in particles of powders compressed at room temperature under different pressures were studied in real time using synchrotron radiation with heating in the range of 300–370 K. It was found that the content of the monoclinic phase in reactor powders depends on the type of catalyst used for synthesis and on the applied pressure. It is shown that there are monoclinic phases of different nature: a structurally stabilized monoclinic phase formed during synthesis, and a monoclinic phase resulting from plastic deformation during compaction at room temperature. The behavior of these phases in temperature and mechanical fields is compared

<i>N</i>-(4-Methyl-3-((4-(pyridin-3-yl)pyrimidin-2-yl)amino)phenyl)-4-((4-methylpiperazin-1-yl)methyl)benzamide

Imatinib is one of the most used therapeutic agents to treat leukemia, which specifically inhibits the activity of tyrosine kinases. This polytopic molecule has been structurally characterized only in the form of its piperazin-1-ium salt (mesylate, picrate, citrate, fumarate or malonate). Herein we present the crystal structure of the freebase Imatinib which precipitated from a 1:10 mixture with arginine. The molecule realizes an extended conformation and forms infinite H-bonded chains through its amide, amine and pyrimidine groups

Abiraterone Acetate Complexes with Biometals: Synthesis, Characterization in Solid and Solution, and the Nature of Chemical Bonding

Abiraterone acetate (AbirAc) is the most used steroidal therapeutic agent for treatment of prostate cancer. The mainly hydrophobic molecular surface of AbirAc results in its poor solubility and plays an important role for retention of abiraterone in the cavity of the receptor formed by peptide chains and heme fragments. In order to evaluate the hydrolytic stability of AbirAc, to modify its solubility by formation of new solid forms and to model bonding of this medication with the heme, a series of d-metal complexes with AbirAc was obtained. AbirAc remains stable in water, acetonitrile, tetrahydrofuran, and ethanol, and readily interacts with dications as a terminal ligand to create discrete complexes, including [FePC(AbirAc)2] and [ZnTPP(AbirAc)] (H2PC = phthalocyanine and H2TPP = 5,10,15,20-tetraphenylporphyrine) models for ligand–receptor bonding. In reactions with silver(I) nitrate, AbirAc acts as a bridge ligand. Energies of chemical bonding between AbirAc and these cations vary from 97 to 235 kJ mol−1 and exceed those between metal atoms and water molecules. This can be indicative of the ability of abiraterone to replace solvent molecules in the coordination sphere of biometals in living cells, although the model [ZnTPP] complex remains stable in CDCl3, CD2Cl2, and 1,1,2,2-tetrachloroethane-d2 solvents and decomposes in polar dimethylsulfoxide-d6 and methanol-d4 solvents, as follows from the 1H DOSY spectra. Dynamics of its behavior in 1,1,2,2-tetrachloroethane-d2 were studied by ROESY and NMR spectra

N-Cyclohexylcyclohexanaminium {[acetyl(methyl)amino]methyl}bis [4,5-dibromobenzene-1,2-diolato]silicate(IV) 4,5-dibrobenzene-1,2-diol Ethanol Solvate

An X-ray diffraction study of a transesterification product of N-methyl-N-(trimethoxysilylmethyl)acetamide by 4,5-dibromobenzene-1,2-diol was carried out. It was established that the coordination polyhedron of the silicon atom in an anionic complex is a distorted octahedron disordered due to the superposition of the &Delta; and &Lambda; optical isomers. The presence of various hydrogen donor groups in bis(cyclohexyl)ammonium cations, solvent ethanol molecules, and non-coordinated 4,5-dibromobenzene-1,2-diol caused the formation of H-bonded chains, while dibromobenzenediol also took part in stacking interactions

Phase Transformation in UHMWPE Reactor Powders Synthesized on Various Catalysts in Mechanical and Thermal Fields

Nowadays, a solvent-free method for production of high performance fibers directly from ultrahigh-molecular-weight polyethylene (UHMWPE) reactor powder is being actively developed. It causes the interest in the morphology of the reactor particles and their behavior in thermal and mechanical fields. Changes in the phase composition in virgin particles of ultra-high molecular-weight polyethylene reactor powders and in particles of powders compressed at room temperature under different pressures were studied in real time using synchrotron radiation with heating in the range of 300–370 K. It was found that the content of the monoclinic phase in reactor powders depends on the type of catalyst used for synthesis and on the applied pressure. It is shown that there are monoclinic phases of different nature: a structurally stabilized monoclinic phase formed during synthesis, and a monoclinic phase resulting from plastic deformation during compaction at room temperature. The behavior of these phases in temperature and mechanical fields is compared

Crystal structures of the two epimers from the unusual thermal C6-epimerization of 5-oxo-1,2,3,5,5a,6,7,9b-octahydro-7,9a-epoxypyrrolo[2,1-a]isoindole-6-carboxylic acid, 5a(RS),6(SR),7(RS),9a(SR),9b(SR) and 5a(RS),6(RS),7(RS),9a(SR),9b(SR)

The isomeric title compounds, C12H13NO4 (Ia) and C12H13NO4 (IIa), the products of an usual thermal C6-epimerization of 5-oxo-1,2,3,5,5a,6,7,9b-octahydro-7,9a-epoxypyrrolo[2,1-a]isoindole-6-carboxylic acid, represent the two different diastereomers and have very similar molecular geometries. The molecules of both compounds comprise a fused tetracyclic system containing four five-membered rings (pyrrolidine, pyrrolidinone, dihydrofuran and tetrahydrofuran), all of which adopt the usual envelope conformations. The dihedral angle between the basal planes of the pyrrolidine and pyrrolidinone rings are 14.3 (2) and 16.50 (11)°, respectively, for (Ia) and (IIa). The nitrogen atom has a slightly pyramidalized geometry [bond-angle sum = 355.9 and 355.3°, for (Ia) and (IIa)], respectively. In the crystal of (Ia), molecules form zigzag-like hydrogen-bonded chains along [010] through strong O—H...O hydrogen bonds and are further linked by weak C—H...O hydrogen bonds into complex two-tier layers parallel to (100). Unlike (Ia), the crystal of (IIa) contains centrosymmetric cyclic hydrogen-bonded dimers [graph set R22(14)], formed through strong O—H...O hydrogen bonds and are further linked by weak C—H...O hydrogen bonds into ribbons extending across [101]

Synthesis, Structure and Magnetic Properties of Low-Dimensional Copper(II) <i>trans</i>-1,4-cyclohexanedicarboxylate

A reaction between copper(II) nitrate and trans-1,4-cyclohexanedicarboxylic acid (H2chdc) carried out under hydrothermal conditions led to a new metal-organic coordination polymer [Cu2(Hchdc)2(chdc)]n. According to single-crystal XRD data, the compound is based on bi-nuclear paddlewheel-type carboxylate blocks that are joined with polymeric chains due to the (μ3-κ1:κ2) coordination of carboxylate groups. The chains are interconnected by chdc2− bridging ligands into layers containing free COOH groups of terminal Hchdc−. The neighboring layers adopt a RCOOH···OOCR hydrogen bond-assisted arrangement into a dense-packed structure. Magnetization measurements showed the presence of a strong antiferromagnetic exchange interaction (J/kB = −495 K) inside the bi-nuclear blocks. At the same time, no significant interaction was found between the {-Cu2(OOCR)4-} units in spite of their polymeric in-chain packing. Patterns of magnetic behavior of [Cu2(Hchdc)2(chdc)]n were thoroughly analyzed and explained from a structural point of view

Toward New Horizons in Verdazyl-Nitroxide High-Spin Systems: Thermally Robust Tetraradical with Quintet Ground State

High-spin organic tetraradicals with significant intramolecular exchange interactions have high potential for advanced technological applications and fundamental research, but reported to date examples exhibit limited stability and processability. In this work, we designed the first tetraradical based on an oxoverdazyl core and nitronyl nitroxide radicals and successfully synthesized it using a palladium-catalyzed cross-coupling reaction of oxoverdazyl radical bearing three iodo-phenylene moieties with a gold(I) nitronyl nitroxide-2-ide complex in the presence of a recently developed efficient catalytic system. The molecular and crystal structures of the tetraradical were confirmed by single crystal X-ray diffraction analysis. The tetraradical possesses good thermal stability with decomposition onset at ∼115 °C in an inert atmosphere. The resulting unique verdazyl-nitroxide conjugate was thoroughly studied using a complex of SQUID magnetometry of polycrystalline powders, EPR spectroscopy in various matrices, cyclic voltammetry (CV), and high-level quantum chemical calculations. All collected data confirm the high thermal stability of the resulting tetraradical and quintet multiplicity of its ground state, which makes the synthesis of this important paramagnet a new milestone in the field of creating high-spin systems