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Université de Fribourg

CFA-2 and CFA-3 (Coordination Framework Augsburg University-2 and -3); novel MOFs assembled from trinuclear Cu(I)/Ag(I) secondary building units and 3,3′,5,5′-tetraphenyl-bipyrazolate ligands

Grzywa, Maciej ; Geßner, Christof ; Denysenko, Dmytro ; Bredenkötter, Björn ; Gschwind, Fabienne ; Fromm, Katharina M. ; Nitek, Wojciech ; Klemm, Elias ; Volkmer, Dirk

In: Dalton Transactions, 2013, vol. 42, no. 19, p. 6909–6921

The syntheses of H₂-phbpz, [Cu₂(phbpz)]·2DEF·MeOH (CFA-2) and [Ag₂(phbpz)] (CFA-3) (H₂-phbpz = 3,3′,5,5′-tetraphenyl-1H,1′H-4,4′-bipyrazole) compounds and their crystal structures are described. The Cu(I) containing metal–organic framework CFA-2 crystallizes in the tetragonal crystal system, within space...

Université de Fribourg

Rings, chains and helices: new antimicrobial silver coordination compounds with (iso-)nicotinic acid derivatives

Chevrier, Inès ; Sagué, Jorge L. ; Brunetto, Priscilla S. ; Khanna, Nina ; Rajacic, Zarko ; Fromm, Katharina M.

In: Dalton Transactions, 2013, vol. 42, no. 1, p. 217-231

Complexes with silver ions have great potential for applications in medicine. Appropriate bidentate ligands, binding to silver ions, are able to generate coordination polymers as well as molecular entities as a function of ligand flexibility, conformation and length. Here we present the continuation of our previous studies in this field with ligands based on oligomers of polyethylene glycol,...

Université de Fribourg

pH-dependent coordination of AgI ions by histidine: experiment, theory, and a model for SilE

Mirolo, Laurent ; Schmidt, Tobias ; Eckhardt, Sonja ; Meuwly, Markus ; Fromm, Katharina M.

In: Chemistry - A European Journal, 2013, vol. 19, no. 5, p. 1754–1761

Artificial implants and biomaterials lack the natural defense system of our body and, thus, have to be protected from bacterial adhesion and biofilm formation. In addition to the increasing number of implanted objects, the resistance of bacteria is also an important problem. Silver ions are well-known for their antimicrobial properties, yet not a lot is known about their mode of action. Silver is...

Université de Fribourg

Kinetics of ion transport through supramolecular channels in single crystals

Assouma, Cyrille D. ; Crochet, Aurélien ; Chérémond, Yvens ; Giese, Bernd ; Fromm, Katharina M.

In: Angewandte Chemie International Edition, 2013, vol. 52, no. 17, p. 4682–4685

Single-crystal to single-crystal transformations are possible by ion-exchange and transport reactions through supramolecular channels that are composed of crown ether molecules and use trihalide ions as scaffolds. Kinetic measurements of ion transport at different temperatures provide activation energy data and show that a very fast.

Université de Fribourg

Single crystal to single crystal polymorphic phase transition of a silver nitrate 24-crown-8 complex and its pseudo-polymorphism

Girard, Jérôme ; Fromm, Katharina M.

In: CrystEngComm, 2012, vol. 14, no. 20, p. 6487-6491

A silver nitrate 24-crown-8 complex [Ag₄(24-crown-8)(NO₃)₄] (1) was synthesized, showing a single crystal to single crystal polymorphic phase transition induced by temperature and leading to polymorph [Ag₄(24-crown-8)(NO₃)₄] 1′. When this complex (1) is exposed to humidity or directly crystallized from a water containing...

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...