Olefin polymerization behavior of titanium(IV) alkoxo complexes with fluorinated diolate ligands: The impact of the chelate ring size and the nature of organoaluminum compounds

Titanium(IV) coordination compounds are effectively used as precatalysts for ethylene polymerization and copolymerization with other olefins. New titanium(IV) complexes 3b – d with ligands containing two diphenylcarbinol fragments linked by the perfluorinated hydrocarbon units –CF₂– or –C₂F₄– were synthesized. The structures of complexes 3b and 3d were determined by X-ray diffraction. Titanium atoms in 3b have a distorted trigonal-bipyramidal coordination environment while spiro-complex 3d is characterized by tetrahedral molecular geometry. The catalytic behavior of complexes activated by mixtures of Bu₂Mg and alkylaluminium chlorides from among Me₂AlCl, Et₂AlCl, EtAlCl₂, and Et₃Al₂Cl₃ were studied. The resulting catalytic systems catalyze ethylene polymerization to afford ultra-high molecular weight polyethylene, suitable for modern processing methods, and the solvent-free solid state formation of super high-strength (1.37–2.75 GPa) and high-modulus (up to 138 GPa) oriented film tapes. The same catalytic systems catalyze ethylene copolymerization with 1-hexene to afford high molecular weight semicrystalline elastomeric polymers containing up to 20% of comonomer units.     

Strict and bistrict plus-operators

We consider the theory of operators in spaces with indefinite metric. Strict plus-operators acting between two Krein spaces are considered. A construction showing that, under certain conditions, a strict plus-operator can be considered as a bistrict plus-operator without loss of generality is given.     

Enhancing Tumor Cell Response to Chemotherapy through the Targeted Delivery of Platinum Drugs Mediated by Highly Stable,Multifunctional Carboxymethylcellulose‐Coated Magnetic Nanoparticles

The fabrication of nanoparticles using different formulations, and which can be used for the delivery of chemotherapeutics, has recently attracted considerable attention. We describe herein an innovative approach that may ultimately allow for the selective delivery of anticancer drugs to tumor cells by using an external magnet. A conventional antitumor drug, cisplatin, has been incorporated into new carboxymethylcellulose‐stabilized magnetite nanoparticles conjugated with the fluorescent marker Alexa Fluor 488 or folic acid as targeting agent. The magnetic nanocarriers possess exceptionally high biocompatibility and colloidal stability. These cisplatin‐loaded nanoparticles overcome the resistance mechanisms typical of free cisplatin. Moreover, experiments aimed at the localization of the nanoparticles driven by an external magnet in a medium that mimics physiological conditions confirmed that this localization can inhibit tumor cell growth site‐specifically.     

Heterocyclization of N-(1-chloro-2,2,2-trifluoroethylidene)carbamates with β-enaminoesters—a novel synthetic strategy to functionalized trifluoromethylated pyrimidines

A novel synthetic strategy to 4-trifluoromethyl substituted 2-oxo-1,2-dihydropyrimidine-5-carboxylates has been developed based on the cyclocondensation of β-enaminoesters with N-(1-chloro-2,2,2-trifluoroethylidene)carbamates.     

Hyperbolicity,CAT(−1)-spaces and the Ptolemy inequality

Using a four points inequality for the boundary of CAT(-1)-spaces we study the relation between Gromov hyperbolic spaces and CAT(-1)-spaces.     

Solvent-induced hydrogen tunnelling in ascorbate proton-coupled electron transfers

The over-the-barrier proton-coupled electron transfer interaction of an ascorbate monoanion with a hexacyanoferrate(III) ion in water entered into a tunnelling regime in water-1,4-dioxane, water-ethanol and water-acetonitrile mixed solvents.