Search results for "salen"
showing 10 items of 35 documents
A comparative study on the polymerization of 1-octene promoted by vanadium and titanium complexes supported by phenoxyimine and salen type ligands
2013
Polymerizations of 1-octene were carried out in the presence of vanadium and titanium complexes bearing salen-type or phenoxyimine ligands activated with various co-catalysts. Vanadium complexes turned out active only in conjunction with MAO, whereas the titanium ones were active in combination with Al(i-Bu)3/Ph3CB(C6F5)4. The activity of all catalysts was moderate or low and it was dependent on the ligand type: bis(phenoxyimine) complexes were more active than the salen ones. Both vanadium and titanium catalytic systems produced poly(1-octene)s possessing atactic structures with [mmmm] sequences in the range from 12 to 56 % at room temperature. A temperature decrease to 0.5 °C for the reac…
Ligands hybrides : synthèse et chimie de coordination
2011
This manuscript deals with the synthesis of hybrids ligands and their coordination ability. The first part is dedicated to Cp-imidazole, Cp-imidazolium and Cp-phosphine ligands. Several synthetic routes have been developed to reach these mixed ligands and their coordination chemistry has been studied with titanium. In a second part, a method developed in our laboratory to synthesize phosphine-olefines was applied to obtain a phosphino-diene bearing three potential coordination sites. We have studied the coordination modes of this hybrid ligand using various transition metals and some of the formed complexes were tested in catalysis. In the third part is described the coordination chemistry …
A method for genome-wide analysis of DNA helical tension by means of psoralen-DNA photobinding
2010
The helical tension of chromosomal DNA is one of the epigenetic landmarks most difficult to examine experimentally. The occurrence of DNA crosslinks mediated by psoralen photobinding (PB) stands as the only suitable probe for assessing this problem. PB is affected by chromatin structure when is done to saturation; but it is mainly determined by DNA helical tension when it is done to very low hit conditions. Hence, we developed a method for genome-wide analysis of DNA helical tension based on PB. We adjusted in vitro PB conditions that discern DNA helical tension and applied them to Saccharomyces cerevisiae cells. We selected the in vivo cross-linked DNA sequences and identified them on DNA …
Makašānu Salenieku kapulauks: apbedījumu veidi un hronoloģija
2018
Bakalaura darba mērķis ir izanalizēt Salenieku Makašānu kapulaukā esošās apbedīšanas tradīcijas, apbedījumus un kapu piedevas, kā arī precizēt kapulauka hronoloģiju. Pamatā darba izstrādē izmantoti pārskati par kapulaukā veiktajiem izrakumiem un to laikā iegūtā senlietu kolekcija. Darbā tiek apskatīti Salenieku Makašānu kapulaukā esošie dažādie apbedīšanas veidi. Pētīta izrakumos iegūtā informācija par uzkalniņos un akmeņu krāvumos atrastajiem kapiem. Lai precizētu kapulauka hronoloģiju tiek meklētas analoģijas Salenieku Makašānu kapulaukā atrastajām kapu piedevām.
Tri-alkenyl polyhedral oligomeric silsesquioxanes as comonomers and active center modifiers in ethylene copolymerization catalyzed by bis(phenoxy-imi…
2018
Abstract In copolymerization of ethylene (E) with tri-alkenyl-silsesquioxanes (POSS-6-3 and POSS-10-3) were used bis(phenoxy-imine) titanium, zirconium and vanadium catalysts, as well as salen-type vanadium catalysts. There were obtained copolymers with POSS-R-3 units as side branches of polymer chains. The type of employed bis(phenoxy-imine) titanium, zirconium and vanadium catalysts and salen-type catalyst of vanadium determined the copolymer chain termination reactions, as well as the mechanism of modification of the active species by the POSS-R-3 comonomer. POSS-R-3 comonomers caused selective poisoning of bis(phenoxy-imine) zirconium catalyst and they provided protection against tight …
Consolidation of waterlogged woods by in-situ polymerisation of isoeugenol
2008
Stereoselective synthesis of oligosaccharides by de novo saccharide welding
2012
Titanium (IV) chloride complexes with salen ligands supported on magnesium carrier: Synthesis and use in ethylene polymerization
2009
The magnesium support with the formula MgCl 2 (THF) 0.32 (Et 2 AlCl) 0.36 was used for immobilization of salen complexes of titanium [Ti(salen)Cl 2 , Ti(salen(O-Me) 2 )Cl 2 ]. The effects of the catalyst composition (i.e. type of titanium complex and type of activator), polymerization temperature, polymerization time, and the effect of comonomer (1-octene) on the activity of the obtained supported catalysts, on the polymer characteristics (molecular weight, molecular weight distribution, melting point), and on the polymer morphology were studied. The findings were compared to those obtained for corresponding unsupported systems. Catalysts immobilization results in considerable changes in ca…
Polimeryzacja propylenu katalizowana metaloorganicznymi kompleksami z chiralnymi ligandami salenowymi
2007
Postęp badań w zakresie polimeryzacji olefin
2011
Na podstawie obszernego przeglądu literatury omówiono rozwój katalizatorów metaloorganicznych stosowanych w procesie polimeryzacji olefin z uwzględnieniem najnowszych badań w tym zakresie. Przedstawiono możliwości otrzymywania z ich udziałem produktów o różnej strukturze i właściwościach. Na tle postępu w technologii otrzymywania poliolefin scharakteryzowano wyniki najnowszych prac zespołu opolskiego, od wielu lat biorącego aktywny udział w badaniach nad opracowaniem i oceną właściwości katalitycznych kolejnych, nowych grup metaloorganicznych katalizatorów polimeryzacji i kopolimeryzacji olefin. Szczególną uwagę poświęcono katalizatorom zaliczanym do grupy układów postmetalocenowych z ligan…