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Bichler B.,Vienna University of Technology | Veiros L.F.,University of Lisbon | Oztopcu O.,Vienna University of Technology | Puchberger M.,Vienna University of Technology | And 4 more authors.
Organometallics | Year: 2011

A series of cationic palladium allyl complexes of the type [Pd(η3-allyl)(κ2(E,N)-EN-chelate)]+ containing several heterodifunctional EN (E = P, O, S, Se) ligands based on N-(2-pyridinyl) aminophosphines and oxo, thio, and seleno derivatives thereof are prepared. These complexes are studied by one- and two-dimensional NMR techniques together with X-ray and DFT calculations. Variable-temperature and phase-sensitive 1H,1HNOESYNMRmeasurements reveal both allyl and EN ligand dynamics. In the case of palladium, PN complexes' η3 to η1 isomerization takes place by opening the η3-allyl group selectively at the trans position with respect to the phosphorus center, while for EN (E = O, S, Se) complexes an "apparent" allyl rotation is observed proceeding with Pd-E and Pd-Nbond breaking. DFT calculations indicate that both isomerization processes are solvent assisted, in agreement with the NMR data. In addition, the use of the new palladium allyl complexes has been examined as catalysts for Suzuki-Miyaura coupling of various aryl bromides and arylboronic acids. [Pd(η3-CHPhCHCH2)(ON-Ph)]+, bearing an η3- cinnamyl ligand, is one of the most efficient catalysts, converting aryl bromides and arylboronic acids at 80 °C with a catalyst loading of 0.1 mol % quantitatively into the expected biaryl products. © 2011 American Chemical Society.


Benito-Garagorri D.,Institute of Applied Synthetic Chemistry | Alves L.G.,Institute of Applied Synthetic Chemistry | Veiros L.F.,University of Lisbon | Standfest-Hauser C.M.,Institute of Applied Synthetic Chemistry | And 3 more authors.
Organometallics | Year: 2010

Treatment of either cis-[Fe(PNP)(X2)(CO)], trans-[Fe(PNP)(X 2)(CO)], or [Fe(PNP)X2] (X = Cl, Br; PNP are tridentate pincer-type ligands based on 2,6-diaminopyridine and 2,6-diaminopyrimidine) with 1 equiv of AgBF4 in the presence of CO afforded selectively octahedral iron(II) complexes of the type trans-[Fe(PNP)(CO)2X] +. The same reaction carried out with trans-[Fe(PNP-iPr)(Cl) 2(CO)] in the absence of CO affords also trans-[Fe(PNP-iPr)(CO) 2Cl]+ together with unidentified paramagnetic species. This reaction involves an intermolecular CO transfer between coordinately unsaturated [Fe(PNP-iPr)(CO)(Cl)]+ intermediates. In all reactions studied, there was no evidence for the formation of cis dicarbonyl complexes. X-ray structures of representative complexes are presented. A detailed mechanism, based on DFT/B3LYP calculations, is presented, suggesting that upon irreversible removal of X- transient cationic intermediates [Fe(PNP)(CO)(X)]+ of two conformations, one with the CO in the apical and the halide in the basal position (A) and vice versa (B), are formed. These adopt a singlet ground state in the case of A and a triplet ground state in the case of B. The formation of trans-[Fe(PNP)(CO)2X]+ is kinetically controlled, with A in the singlet ground state being the key intermediate. Pathways originating from complexes with a triplet ground state are "spin-blocked" (spin forbidden) or thermodynamically disfavored. © 2010 American Chemical Society.


De Aguiar S.R.M.M.,University of Lisbon | De Aguiar S.R.M.M.,Institute of Applied Synthetic Chemistry | Nicolai M.,University of Lisbon | Almeida M.,University of Lisbon | Gomes A.,University of Lisbon
Bio-Medical Materials and Engineering | Year: 2015

The stability of the Co-Cr-Mo dental alloy immersed in artificial salivas (pH 6.7) was investigated over 24 h. Three artificial salivas have been studied: saline saliva (saliva I); saline saliva buffered with phosphate ions (saliva II) and saliva II plus mucin molecules (saliva III). For all the systems, open circuit potential shift positively over 24 hours of immersion. Data extracted from the steady-state polarization curves demonstrated that the Co-Cr-Mo alloy has higher corrosion potential in saliva III, lower corrosion potential in saliva I and lower initial corrosion resistance in saliva III. After 24 hours of immersion in the artificial salivas, the Co-Cr-Mo alloy presents high corrosion stability, due to the protective action created by the presence of corrosion products. From the analysis of the breakdown potential it was concluded that, the presence of the phosphate ions and mucin promote the oxidation process, inducing the formation of etch pits. Regarding the effect of the mucin concentration in the corrosion behaviour of the Co-Cr-Mo dental alloy, it was observed a negative shift in the corrosion potential, pointing to a cathodic inhibitor role for the mucin molecules. Nevertheless, no correlation between the mucin concentration and corrosion rate was possible to establish. © 2015-IOS Press and the authors. All rights reserved.


Stoger B.,Institute of Chemical Technologies and Analytics | Weil M.,Institute of Chemical Technologies and Analytics | Murugesan S.,Institute of Applied Synthetic Chemistry | Kirchner K.,Institute of Applied Synthetic Chemistry
Zeitschrift fur Kristallographie - Crystalline Materials | Year: 2016

Four twins are interpreted by pseudo-symmetry analysis. The pincer complexes Co(PCP)X (X=Cl, Br) are order-disorder (OD) twins. The individuals are composed of one polytype with a maximum degree of order (MDO) with Pc symmetry, whereas at the composition plane is located a fragment of the second MDO polytype with Pbc21 symmetry. The twinning of the low-temperature (LT, 100 K) P21 phase of 2,3-dicyanohydroquinone dihydrate (DCHQ·H2O) can be explained by a symmetry reduction of index 2 from the high-temperature (HT, 250 K) Pn21m phase. Propylammonium perchlorate (nPrNH3ClO4) features different kinds of twinning. On the one hand, transformation twinning is caused by a symmetry reduction of index 2 from the HT (150 K) Pbnm to the LT (100 K) P21/n phase. On the other hand, the crystals feature growth twinning by rotation about the [010] axis, where the nature of the twin interface remains unknown. The twinning of the Ccce Ba[H2TeO5] structure with pseudo-tetragonal metrics is explained by a part of the structure featuring higher P42/nmc symmetry. At the twin interface is probably located a fragment with the formal composition TeO3. © 2016 Walter de Gruyter GmbH, Berlin/Boston.


Stoger B.,Institute of Chemical Technologies and Analytics | Pokorny B.,Institute of Applied Synthetic Chemistry | Lumpi D.,Institute of Applied Synthetic Chemistry | Zobetz E.,Institute of Chemical Technologies and Analytics | Frohlich J.,Institute of Applied Synthetic Chemistry
Zeitschrift fur Kristallographie | Year: 2013

The closely related 5-[(1Z)-2-(methylthio)-1-propen-1-yl]-3-(4-nitrophenyl) isoxazole (I) and 3-(4-meth-oxyphenyl)-5-[(1Z)-2-(methylthio)-1-propen-1-yl] isoxazole (II) were synthesized by consecutive ring fragmentation and cycloaddition and their crystal structures were determined by X-ray single crystal diffraction at 100 K. Both compounds are twinned by mirroring at (100). The nitrophenyl (I) [P21=c, Z = 8, Z′ = 2, a = 32:1827(10) Å, b = 5:5992(2) Å, c = 13:9145(4) Å, β = 102:2428(14)°, Robs = 0:048, 6408 F data, 344 parameters] crystallizes as an order-disorder (OD) structure of one kind of layers. The twin individuals are polytypes of a maximum degree of order (MDO). The twin boundary is interpreted as a triple of adjacent layers of the second MDO polytype. The methoxyphenyl (II) [P21=c, Z = 4, Z′ = 1, a = 16:0545(7) Å, b = 5:6575(3) Å, c = 13:8891(7) Å, β = 94:334(3)°, Robs = 0:039, 3365 F data, 164 parameters] can be described as an OD structure composed of two kinds of layers, made up of -CH2-fragments of the S-methyl groups and the remaining parts of the (II) molecules, respectively. Of the four MDO polytypes, one corresponds to the twin individuals. The twin boundary is composed of layer triples of either of two other MDO polytypes. © by Oldenbourg Wissenschaftsverlag, München.


Bichler B.,Institute of Applied Synthetic Chemistry | Holzhacker C.,Institute of Applied Synthetic Chemistry | Glatz M.,Institute of Applied Synthetic Chemistry | Stoger B.,Institute of Chemical Technologies and Analytics | Kirchner K.,Institute of Applied Synthetic Chemistry
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials | Year: 2015

The systematic twinning of three 2,6-diaminopyridine-based Fe-PNP complexes is interpreted using order-disorder (OD) theory. The monoclinic [Fe0(PNPEt-iPr)(CO)2] [P1121/b, Z′ = 4] possesses pseudo-orthorhombic metrics and crystallizes as a reflection twin by pseudo-merohedry with the twin plane (100). The structure is made up of layers with idealized p21 a(b) symmetry. The a glide planes of adjacent layers do not overlap, leading to OD polytypism. trans-[FeII(PNP-Et)Br2(CO)] [P21/n, Z′ = 1] is systematically twinned via twofold rotation about [001]. It is made up of OD layers with idealized p2121(2) symmetry. OD polytypism is caused by the twofold rotation axes of adjacent layers which do not overlap. [FeII(κ2 P,N-PNP-iPr,TAD)Cl2]·THF [P1, ] is systematically twinned via a twofold rotation about [010]. It is made up of layers with idealized p121(1) symmetry. OD polytypism is caused by screw rotations relating adjacent layers with an intrinsic translation along a fourth of a primitive lattice vector. In all three structures the twin individuals are a polytype with a maximum degree of order (MDO) and at the twin interface is located a fragment of the second MDO polytype. © 2015 International Union of Crystallography.


PubMed | Institute of Applied Synthetic Chemistry and Institute of Chemical Technologies and Analytics
Type: Journal Article | Journal: Acta crystallographica Section B, Structural science, crystal engineering and materials | Year: 2015

The systematic twinning of three 2,6-diaminopyridine-based Fe-PNP complexes is interpreted using order-disorder (OD) theory. The monoclinic [Fe(0)(PNP(Et)-(i)Pr)(CO)2] [P112(1)/b, Z = 4] possesses pseudo-orthorhombic metrics and crystallizes as a reflection twin by pseudo-merohedry with the twin plane (100). The structure is made up of layers with idealized p2(1)a(b) symmetry. The a glide planes of adjacent layers do not overlap, leading to OD polytypism. trans-[Fe(II)(PNP-Et)Br2(CO)] [P2(1)/n, Z = 1] is systematically twinned via twofold rotation about [001]. It is made up of OD layers with idealized p2(1)2(1)(2) symmetry. OD polytypism is caused by the twofold rotation axes of adjacent layers which do not overlap. [Fe(II)((2)P,N-PNP-(i)Pr,TAD)Cl2]THF [P1, Z^{\prime} = 2] is systematically twinned via a twofold rotation about [010]. It is made up of layers with idealized p121(1) symmetry. OD polytypism is caused by screw rotations relating adjacent layers with an intrinsic translation along a fourth of a primitive lattice vector. In all three structures the twin individuals are a polytype with a maximum degree of order (MDO) and at the twin interface is located a fragment of the second MDO polytype.


Duong H.T.T.,University of New South Wales | Nguyen T.L.U.,University of New South Wales | Kumpfmuller J.,Institute of Applied Synthetic Chemistry | Stenzel M.H.,University of New South Wales
Australian Journal of Chemistry | Year: 2010

Coreshell nanoparticles have been synthesized by core crosslinking of micelles. The underlying block copolymer, poly(oligo(ethylene glycol methyl ether methacrylate))-block-polystyrene (POEGMA-b-PS), was synthesized successfully by the reversible additionfragmentation chain transfer (RAFT) process, using POEGMA as a macro-RAFT agent. The block copolymers were self-assembled into micelles in aqueous media and the resulting micelles and the RAFT endgroup, located in the core of the micelle, were used for the subsequent crosslinking step using a crosslinker, divinyl benzene (DVB). The rate of the crosslinking reaction was found to be slow with less than 20% conversion being achieved after 72 h. Nevertheless, crosslinked micelles were obtained and only a small fraction of free block copolymers remained. Cytotoxicity tests confirmed the biocompatibility of the prepared core-crosslinked micelles. In addition the crosslinked micelles were taken up by L929 cells without causing any signs of cell damage. © CSIRO 2010.


Murrison S.,University of Leeds | Maurya S.K.,University of Leeds | Einzinger C.,Institute of Applied Synthetic Chemistry | McKeever-Abbas B.,Astrazeneca | And 2 more authors.
European Journal of Organic Chemistry | Year: 2011

A synthetic approach to skeletally diverse alkaloid-like compounds, involving two consecutive three-component reactions, was developed. First, reaction between a range of secondary amines, carbonyl compounds and triazines yielded cyclic imines. Crucially, the identity of the substituents in the amine and carbonyl compound components determined-through a "folding" pathway-the alkaloid-like scaffold that was prepared. The cyclic imine products were substrates for a second reaction, most usually a Joullié-Ugi reaction with an isocyanide and a carboxylic acid. Thus, the final products were, in general, ultimately derived from five separate components, and wide and independent variation of the substitution of each scaffold was possible. The 43 products were based on 28 distinct graph-node level frameworks. The high skeletal diversity of the products stemmed both from the "folding" pathway used to define the scaffolds of the cyclic imines, and from cyclic substituents used in each of the components. A synthetic approach to skeletally diverse alkaloid-like compounds, involving two consecutive three-component reactions, was developed. First, reaction between a range of secondary amines, carbonyl compounds and triazines yielded alternative complex cyclic imines. The cyclic imineswere substrates for a second reaction, most usually a Joullié-Ugi reaction. The final products were, in general, ultimately derived from five separate components. The 43 products were based on 28 distinct graph-node level frameworks. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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