Showing papers by "Andreia Valente published in 2011"
TL;DR: The cytotoxicity of compounds 1234 was much higher than that of cisplatin against human leukemia cancer cells (HL-60 cells) and IC(50) values for all the compounds are in the range of submicromolar amounts.
84 citations
TL;DR: In this paper, a transmetalation process is performed with the borohydride complexes in the presence of magnesium dialkyl and trialkylaluminum, and a 1,4-trans stereospecific reversible coordinative chain transfer copolymerization of isoprene and styrene is observed when the half-lanthanocene 2b is used as precatalyst.
Abstract: A series of lanthanum and neodymium borohydrido complexes comprising the trisborohydrides Nd(BH4)3(THF)3 (1a) and La(BH4)3(THF)3 (1b) and the half-lanthanidocenes Cp*Nd(BH4)2(THF)2 (2a) (Cp* = C5Me5) and Cp*La(BH4)2(THF)2 (2b) has been assessed for the chain transfer copolymerization of isoprene and styrene. A transmetalation process is occurring efficiently with the borohydride complexes in the presence of magnesium dialkyl. The transmetalation is accompanied by (i) a gradual decrease of the 1,4-trans stereoselectivity of the reaction at the benefit of 3,4-selectivity and (ii) an increase in the quantity of styrene inserted in the copolymer. This can be at least partially attributed to a magnesium induced co-oligomerization of isoprene and styrene. By combining dialkylmagnesium and trialkylaluminum, a 1,4-trans stereospecific reversible coordinative chain transfer copolymerization of isoprene and styrene is observed when the half-lanthanocene 2b is used as precatalyst. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
48 citations
TL;DR: In this article, the Cp*La(BH4)2(THF)2/n-butylethylmagnesium (BEM) catalytic system has been assessed for the coordinative chain transfer copolymerization of styrene and 1-hexene.
Abstract: The Cp*La(BH4)2(THF)2/n-butylethylmagnesium (BEM) catalytic system has been assessed for the coordinative chain transfer copolymerization of styrene and 1-hexene. Poly(styrene-co-hexene) statistical copolymers were obtained with number-average molecular weight up to 7600 g/mol, PDI around 1.4 and 1.5 and up to 23% hexene content. The occurence of chain transfer reactions in the presence of excess BEM is established in the course of the statistical copolymerization. Thanks to this transfer process, the quantity of 1-hexene in the copolymer is increased by a factor of about 3 for high ratio of hexene in the feed, extending the range of our concept of a chain transfer induced control of the composition of statistical copolymers to poly(styrene-co-hexene) copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
17 citations
TL;DR: In this paper, a series of ruthenium(II) complexes with the general formula [Ru(η 5 -C 5 H 5 ) (η 6 -substituted arene)] + [PF 6 ] − (substitized arene = 2-phenylpyridine (1), dibenzosuberone (2 ) and toluene (3 )), in combination with isopropyl alcohol, were used for the polymerization of ǫ-caprolactone.
Abstract: A series of ruthenium(II) complexes with the general formula [Ru(η 5 -C 5 H 5 ) (η 6 -substituted arene)] + [PF 6 ] − (substituted arene = 2-phenylpyridine ( 1 ), dibenzosuberone ( 2 ) and toluene ( 3 )), in combination with isopropyl alcohol were used for the polymerization of ɛ-caprolactone. The polymerization was found to be quantitative and controlled, with PDI in the range 1.1–1.3. By means of MALDI-ToF analyses, functionalization studies with d , l -lactide and NMR monitoring techniques, it has been found that the polymerization proceeds via a living Activated Monomer mechanism (AM) involving an η 6 –η 4 change of the coordination mode of the arene. These experimental results were corroborated by DFT studies. The growth of several polymer chains per ruthenium atom highlights interesting potentialities for molecular weight control and catalyst economy. The stability of the ruthenium complexes allows their recovery at the end of the polymerization, which can be viewed as a further advance in a green chemistry frame.
11 citations