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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...

Université de Fribourg

A transparent, flexible, ion conductive, and luminescent PMMA ionogel based on a Pt/Eu bimetallic complex and the ionic liquid [Bmim][N(Tf)₂]

Xie, Zai-Lai ; Xu, Hai-Bing ; Geßner, André ; Kumke, Michael U. ; Priebe, Magdalena ; Fromm, Katharina M. ; Taubert, Andreas

In: Journal of Materials Chemistry, 2012, vol. 22, no. 16, p. 8110-8116

Transparent, ion-conducting, luminescent, and flexible ionogels based on the room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide [Bmim][N(Tf)₂], a PtEu₂ chromophore, and poly(methylmethacrylate) (PMMA) have been prepared. The thermal stability of the PMMA significantly increases with IL incorporation. In particular, the onset weight loss observed...

Université de Fribourg

Switching azonaphthols containing a side chain with limited flexibility. Part 1. Synthesis and tautomeric properties

Kurteva, Vanya B. ; Antonov, Liudmil ; Nedeltcheva, Daniela V. ; Crochet, Aurélien ; Fromm, Katharina M. ; Nikolova, Rositsa P. ; Shivachev, Boris L. ; Nikiforova, Maya S.

In: Dyes and Pigments, 2012, vol. 92, no. 3, p. 1266–1277

A series of azo dyes, possessing amide fragments with restricted flexibility tethered to 4-(phenyldiazenyl)naphthalen-1-ol, was obtained from 1-hydroxy-2-naphthoic acid by subsequent conversion to amides and diazo coupling. It was shown that the position of the tautomeric equilibrium in solution strongly depends on the solvent in both UV and NMR concentration scale. The compounds exist as...

Université de Fribourg

Coordination Networks of Mercury(II) Halides and Polyether Ligand

Crochet, Aurélien ; Fromm, Katharina M.

In: Zeitschrift für anorganische und allgemeine Chemie, 2011, vol. 637, no. 14-15, p. 2089–2092

New crystalline mercury halide adducts with polyetheras ligands were isolated, characterized, and identified as trans-[HgIICl₂(diox)₂]n (1) and trans-[HgIII₂(diox)]n (2). The compounds were obtained from the metal halide salts in solution of 1,4-dioxane and can be considered as “cutting-out”...

Université de Fribourg

Tetraethylene glycol adducts of alkaline earth halides

Gschwind, Fabienne ; Fromm, Katharina M.

In: Zeitschrift für anorganische und allgemeine Chemie, 2011, vol. 637, no. 12, p. 1871–1879

Reaction of commercially available tetraethylene glycol with different alkaline earth metal halides affords tetraethylene glycol complexes with different coordination numbers at the metal ion and structural features; depending on the ionic radius of the metal ion, one or two ligand molecules will be coordinated to the metal ion. In this article we will first present complexes with...

Université de Fribourg

Polymorph of dibenzo-24-crown-8 and its mercury complex

Crochet, Aurélien ; Kottelat, Emmanuel ; Fleury, Antoine ; Neuburger, Markus ; Fromm, Katharina M.

In: Zeitschrift für anorganische und allgemeine Chemie, 2011, vol. 637, no. 6, p. 672–675

Dibenzo-24-crown-8 is studied herein as a flexible ligand able to adopt different conformations, as well as for the complexation of mercury. The recrystallization of dibenzo-24-crown-8 (DB24C8) from dry THF gives a new polymorphic structure of this ligand. This new structure is described and compared to the literature compound. Additionally, coordination of this ligand to mercury iodide HgI₂ is...