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Université de Fribourg

The influence of dipole moments on the mechanism of electron transfer through helical peptides

Lauz, Miriam ; Eckhardt, Sonja ; Fromm, Katharina M. ; Giese, Bernd

In: Physical Chemistry Chemical Physics, 2012, vol. 14, no. 40, p. 13785-13788

The life time of aromatic radical cations is limited by reactions like β-elimination, dimerization, and addition to the solvent. Here we show that the attachment of such a radical cation to the C-terminal end of an α-/3₁₀-helical peptide further reduces its life time by two orders of magnitude. For PPII-helical peptides, such an effect is only observed if the peptide contains an adjacent...

Université de Fribourg

A comparative study of (poly)ether adducts of alkaline earth iodides – an overview including new compounds

Maudez, William ; Fromm, Katharina M.

In: Zeitschrift für anorganische und allgemeine Chemie, 2012, vol. 638, no. 11, p. 1810–1819

New homoligand and mixed-ligand adducts of the heavier alkaline earth metal (Ca, Sr, Ba) halides with oxygen-donor polyether ligands have been isolated and characterized and are compared with previously obtained compounds of the same class in order to give an overview on structures and properties. Homoligand halide adducts, discussed herein, are [CaI(DME)₃]I (1),...

Université de Fribourg

Ring a bell: Disubstituted calix[4]arene as ligand for transition metal chlorides

Crochet, Aurélien ; Fromm, Katharina M.

In: Polyhedron, 2012, p. -

Lower rim 1,3-disubstituted p-tert-butylcalix[4]arene is studied here in its deprotonated form as complexing ligand for iron and chromium chloride. Crystallization of the two complexes from dry THF gives two different stoichiometries and structures, a trinuclear iron compound and a second, mononuclear structure with chromium. In both cases, the ligand adopts an elliptical shape and the metal...

Université de Fribourg

Antibacterial properties of nanoparticles

Hajipour, Mohammad J. ; Fromm, Katharina M. ; Ashkarran, Ali Akbar ; Aberasturi, Dorleta Jimenez de ; Larramendi, Idoia Ruiz de ; Rojo, Teofilo ; Serpooshan, Vahid ; Parak, Wolfgang J. ; Mahmoudi, Morteza

In: Trends in Biotechnology, 2012, p. -

Antibacterial agents are very important in the textile industry, water disinfection, medicine, and food packaging. Organic compounds used for disinfection have some disadvantages, including toxicity to the human body, therefore, the interest in inorganic disinfectants such as metal oxide nanoparticles (NPs) is increasing. This review focuses on the properties and applications of inorganic...

Université de Fribourg

Efficient amine end-functionalization of living ring-Opening metathesis polymers

Nagarkar, Amit A. ; Crochet, Aurélien ; Fromm, Katharina M. ; Kilbinger, Andreas F. M.

In: Macromolecules, 2012, vol. 45, no. 11, p. 4447–4453

An efficient strategy for the synthesis of monoamine end-functionalized living polymers using ring-opening metathesis polymerization with ruthenium initiators is reported. A new end-capping agent for this purpose was synthesized, and its efficiency for end-functionalization was evaluated using two common ruthenium-based initiators. Finally, terminal cross-metathesis was also explored as...

Université de Fribourg

Preparation of imidazolidin-4-ones and their evaluation as hydrolytically cleavable precursors for the slow release of bioactive volatile carbonyl derivatives

Trachsel, Alain ; Buchs, Barbara ; Godin, Guillaume ; Crochet, Aurélien ; Fromm, Katharina M. ; Herrmann, Andreas

In: European Journal of Organic Chemistry, 2012, no. 14, p. 2837–2854

Imidazolidin-4-ones are suitable in practical applications as hydrolytically cleavable precursors for the controlled release of fragrant aldehydes and ketones. The corresponding profragrances were prepared by treating aliphatic carbonyl compounds with commercially available amino acid amines in the presence of a base to yield mixtures of diastereomers. The two diastereomers isolated from the...

Université de Fribourg

Synthesis and characterization of new pentacoordinate iron-based aryloxide complexes

Chérémond, Yvens ; Crochet, Aurélien ; Fromm, Katharina M.

In: European Journal of Inorganic Chemistry, 2012, p. -

Heterobimetallic lithium–iron coordination compounds are interesting targets for several reasons: they can be used as precursors for mixed metal oxides, as catalysts, for example, for ring-opening polymerization reactions or to study oxidation/reduction processes. Finally their magnetic properties are also of interest. New heterobimetallic aryloxide complexes, namely...

Université de Fribourg

Effect of increasing ligand length on the structure of silver complexes

Gschwind, Fabienne ; Fromm, Katharina M.

In: CrystEngComm, 2012, p. -

A new series of ligands in which nicotinic acid was linked to different monomethyloligoethers and their corresponding silver complexes were prepared. The crystal structures of the silver compounds were investigated to determine the effect of increasing flexibility of the ligands on coordination to the metal ion and crystal packing. We observed the formation of one-dimensional coordination...

Université de Fribourg

Enhanced electrochemical performance of <30 nm thin LiMnPO4 nanorods with a reduced amount of carbon as a cathode for lithium ion batteries

Kwon, Nam Hee ; Fromm, Katharina M.

In: Electrochimica Acta, 2012, vol. 69, p. 38-44

5–10 nm thin rod shaped LiMnPO₄ nanoparticles are synthesized by an improved thermal decomposition method. The synthesis parameters such as the concentration of surfactants, reaction temperature and time, as well as the presence of a solvent play a critical role in the formation of spherical, thin or thick nanorods, and needle-shaped particles of LiMnPO₄. A washing procedure to efficiently...

Université de Fribourg

Tautomerism in 1-phenylazo-4-naphthols: experimental results vs quantum-chemical predictions

Antonov, Liudmil ; Kurteva, Vanya ; Crochet, Aurélien ; Mirolo, Laurent ; Fromm, Katharina M. ; Angelova, Silvia

In: Dyes and Pigments, 2012, vol. 92, no. 1, p. 714–723

The reliability in the description of the tautomerism of 1-phenylazo-4-naphthol by using of HF and MP2 ab initio levels of theory and DFT methods with variety of pure GGA (OLYP), hybrid (B3LYP and B3PW91), long range corrected (LC-BLYP) and double-hybrid (B2PLYP and mPW2PLYP) functionals with large number of basis sets was estimated. In this evaluation three criteria were used: reproduction...