154289-75-5Relevant academic research and scientific papers
Spectroscopic and electrochemical characterization of di-tert-butylated sterically hindered Schiff bases and their phenoxyl radicals
Kasumov,Medjidov,Yayli,Zeren
, p. 3037 - 3047 (2004)
A series of sterically hindered N-arylsalicylaldimines (SAs) previously prepared from substituted salicylaldehydes (X-Sal, where X = H, Cl, Br, NO 2, OH, OCH3) and 2,6-di-t-butyl-1-hydroxyaniline (L xH) and 2,5-di-t-butylaniline (Lx′H) were characterized by 1H and 13C NMR, UV-Vis and electrochemical methods. The electronic spectra (ES) (X = OH, OCH3) in alcoholic solvents (MeOH, EtOH, PrOH, iso-PrOH) unlike other solvents exhibit a new absorption band in the region 630-675nm (ε=19-242M -1cm-1), which are not characteristic for other SA known in literature. The ESR studies of primary phenoxyl radicals generated from LxH by their oxidation with PbO2 reveal that some of them with the time are converted to more stable secondary Coppinger's radical. The cyclic voltammograms of LxH and Lx′H except NO 2-substituted ones in CH3CN are similar and along with two or three irreversible anodic waves at the potentials ranging from 0.0 to +1.9V versus Ag/AgCl, also display one or two irreversible reduction waves at potentials -0.6 to +0.5V. A series of a new SA prepared from 3,5-di-t-butylsalicylaldehyde and mono-substituted anilines (X = H, o-, p-F, Cl, Br, OCH3, p-t-butyl, 5,6-benzo) were characterized by analytical, spectroscopic (IR, UV-Vis, 1H and 13C NMR), and electrochemical techniques. The ES spectra of o-, p-Cl, p-Br, o-CH3 and 5,6-benzo-substituted SA did not exhibit expected absorptions at 400-500nm in alcoholic solutions.
Syndiospecific living catalysts for propylene polymerization: Effect of fluorination on activity, stereoselectivity, and termination
Mason, Andrew F.,Tian, Jun,Hustad, Philip D.,Lobkovsky, Emil B.,Coates, Geoffrey W.
, p. 301 - 306 (2002)
The polymerization of propylene using a variety of fluorinated bis(phenoxyimine)titanium complexes is reported. The synthesis of ten complexes containing varying fluorinated N-aryl substituents is described. X-ray structural and solution NMR data indicate that these complexes are C 2-symmetric in the solid state, although in some cases C 1-symmetric isomers are observed in solution. When activated with methylalumoxane, all complexes formed syndiotactic polypropylene. Catalysts with ortho-fluorine substituents formed polymers with very narrow molecular weight distributions, indicative of a living polymerization. Catalysts with fluorine in at least the ortho and para positions exhibited the highest syndiospecificities. Catalysts with meta- or para-fluorine-containing substituents were more active for propylene polymerization than the corresponding non-fluorinated catalyst.
