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Université de Fribourg

Ground States, Excited States and Metal-Ligand Bonding in Rare Earth Hexachloro Complexes: A DFT Based Ligand Field Study

Atanasov, Mihail ; Daul, Claude A. ; Güdel, Hans-Ulrich ; Wesolowski, Tomasz A. ; Zbiri, Mohamed

In: Inorganic Chemistry, 2005, vol. 44(8), p. 2954-2963

Metal (4f)-ligand (Cl 3p) bonding in LnCl63- (Ln = Ce to Yb) complexes has been studied on the basis of 4f->4f and Cl,3p->4f charge-transfer spectra and on the analysis of these spectra within the valence bond configuration interaction model to show that mixing of Cl 3p into the Ln 4f ligand field orbitals does not exceed 1%. Contrary to this, Kohn-Sham formalism...

Université de Fribourg

Asymmetric Synthesis of Coordination Compounds: Back to the Roots. Diastereoselective Synthesis of Simple Platinum(IV) Complexes

Drahoňovský, Dušan ; Zelewsky, Alexander von

In: Helvetica Chimica Acta, 2005, vol. 88(3), p. 496-506

A publication by Alexander P. Smirnoff in Helvetica Chimica Acta in 1920 [6] describes the first synthesis of a coordination species, i.e., of tris(propane-1,2-diamine-κN¹,κN²)platinum(4+) ([PtIV(pn)₃]⁴⁺), where it was shown that the configuration of a chiral center in the ligand can influence the configuration at the metal. The present investigation of...

Université de Fribourg

Synthesis and Stereochemical Properties of Chiral Square Complexes of Iron(II)

Bark, Thomas ; Zelewsky, Alexander von ; Rappoport, Dmitrij ; Neuburger, Markus ; Schaffner, Silvia ; Lacour, Jérôme ; Jodry, Jonathan

In: Chemistry - A European Journal, 2004, vol. 10(19), p. 4839-4845

The hexadentate, and ditopic ligand 2,5-bis([2,2']bipyridin-6-yl)pyrazine yields a chiral, tetrameric, square-shaped, self-assembled species upon complexation with Fe²⁺ ions. The racemate of this complex was resolved with antimonyl tatrate as the chiral auxiliary. The purity of the enantiomer was determined by NMR spectroscopy, by using a chiral, diamagnetic shift reagent, and by circular...

Université de Fribourg

Density functional study of nitroprusside: Mechanism of the photochemical formation and deactivation of the metastable states

Buchs, M. ; Daul, Claude A. ; Manoharan, P. T. ; Schläpfer, Carl-Wilhelm

In: International Journal of Quantum Chemistry, 2003, vol. 91 (3), p. 418-431

In this article, we present a theoretical investigation about the mechanism of the photochemical formation and deactivation of the metastable states observed in nitroprusside ions. The quantum chemical calculations are based on density functional theory. The peculiar photochemical and photophysical behavior of this molecule has attracted chemists' interest for a while. Due to this interest, many...

Université de Fribourg

Modelling markets dynamics : minority games and beyond

Challet, Damien ; Zhang, Yi-Cheng (Dir.) ; Dacorogna, Michel (Codir.)

Thèse de doctorat : Université de Fribourg : 2000 ; no 1303.

Starting from the El Farol's bar problem, we introduce the minority game, an extremely simple model of competition between adaptive agents. We study its properties, and find that it displays a phase transition with symmetry breaking. An adequate mathematical formalism is introduced and reveals the spin glass nature of the model. We prove that available information is a Lyapunov function for this...

Université de Fribourg

Study of 110Cd using the (n, n'γ) reaction and 114Te using the (α, 2n) reaction

Corminboeuf, Frédéric ; Jolie, Jan (Dir.)

Thèse de doctorat : Université de Fribourg : 2000 ; Nr. 1326.

The study of nuclear structure is one of the research domains in nuclear physics which have known an important development. It has asked a great effort for the experimenters as well as the theoreticians to study in detail the nuclear many-body problem. In the framework of this thesis, we have tested several nuclear models for two nuclei: 110Cd and 114Te. This choice has not been made at random....

Université de Fribourg

Experimental Evolutionary Biology of Learning in “drosophila melanogaster”

Mery, Frederic ; Kawecki, Tadeusz (Dir.)

Thèse de doctorat : Université de Fribourg : 2003 ; 1403.

La plupart des animaux, invertébrés inclus, ont la capacité de modifier leur comportement à la suite d'expériences, ils sont capables d'apprendre. Leur capacité d'apprentissage est elle-même un produit de l'évolution et le degré de modification d'un comportement par l'apprentissage varie selon les espèces et selon le comportement considéré. Pour un biologiste de l'évolution ceci...

Université de Fribourg

Weak-coupling instabilities of two-dimensional lattice electrons

Binz, Benedikt ; Baeriswyl, Dionys (Dir.) ; Douçot, Benoit (Codir.)

Thèse de doctorat : Université de Fribourg : 2002 ; 1374.

Interacting e1ectrons in two dimensions are of particular interest in relation to high-temperature superconductivity. In this thesis, I study a two-dimensional extended Hubbard model in the weak coupling limit. Quite generally, the electron gas is unstable towards a superconducting state even in the absence of phonons. However in the special case of a half-filled band, the Fermi surface is nested...