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Université de Fribourg

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

Antonov, Liudmil ; Kurteva, Vanya ; Crochet, Aurelien ; 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 of...

Université de Fribourg

Magnetic criteria of aromaticity in a benzene cation and anion: how does the Jahn–Teller effect influence the aromaticity?

Andjelković, Ljubica ; Perić, Marko ; Zlatar, Matija ; Grubišić, Sonja ; Gruden-Pavlović, Maja

In: Tetrahedron Letters, 2011, vol. 53, no. 7, p. 794-799

The aromatic/antiaromatic behavior of the Jahn–Teller (JT) active benzene cation and anion has been investigated using Density Functional Theory (DFT) calculations of Nuclear Independent Chemical Shifts (NICS) and magnetic susceptibility. NICS parameters have been scanned along the Intrinsic Distortion Path (IDP) for the benzene cation showing antiaromaticity which decreases with increasing...

Université de Fribourg

Density functional theory study of the Jahn-Teller effect in cobaltocene

Zlatar, Matija ; Schläpfer, Carl-Wilhelm ; Fowe, Emmanuel Penka ; Daul, Claude A.

In: Pure and Applied Chemistry, 2009, vol. 81, no. 8, p. 1397-1411

A detailed discussion of the potential energy surface of bis(cyclopentadienyl)cobalt(II), cobaltocene, is given. Vibronic coupling coefficients are calculated using density functional theory (DFT). Results are in good agreement with experimental findings. On the basis of our calculation there is no second-order Jahn–Teller (JT) effect as predicted by group theory. The JT distortion can be...

Université de Fribourg

Possible ring structures of armchair single-walled carbon nanotubes

Tamilmani, Venkatachalam ; Daul, Claude A. ; Jenny, Titus A.

In: Chimia, 2006, vol. 60, no. 4, p. 228-230

Energetics and the electronic structure of various types of single-walled carbon nanotubes have been investigated by using Density Functional Theory. Armchair [n,n], zigzag [n,0] and chiral [n,m] C₄₀H₂₀ nanotubes have been considered. Calculations show that the armchair isomer is the most stable among the three types and they further reveal the factors that stabilize this isomer....

Université de Neuchâtel

Vibrational and electronic circular dichroism of Δ-TRISPHAT [tris(tetrachlorobenzenediolato)phosphate(V)] anion

Bas, Delphine ; Bürgi, Thomas ; Lacour, Jerôme ; Vachon, Jerôme ; Weber, Jacques

In: Chirality, 2005, vol. 17, p. S143-S148

Herein is reported an experimental and theoretical study of the circular dichroism properties of TRISPHAT (1) anion. ECD analysis of the [tetramethylammonium][Δ-1] salt confirms the absolute configuration assignment obtained through X-ray crystallographic analysis of the parent cinchonidium salt. The structure, infrared, and vibrational circular dichroism (VCD) spectra derived from...

Université de Fribourg

Asymmetric μ2-1,1-azido bridged copper(II) complex: Synthesis, X-ray structure, magnetic study and DFT calculations

Zbiri, Mohamed ; Saha, Sandip ; Adhikary, Chandan ; Chaudhuri, Siddhartha ; Daul, Claude A. ; Koner, Subratanath

In: Inorganica Chimica Acta, 2006, vol. 359, p. 1193

A new rare variety asymmetric μ2-1,1-azido bridged copper(II) complex has been synthesized and characterized structurally and magnetically. The complex [Cu2L2(μ2-1,1-N3)2] · H2O · CH3OH (L = 1-(N-ortho-hydroxyacetophenimine)-2-aminoethane) (1), crystallizes in monoclinic space group, P21/n, with a = 9.469(4) Angstrom capital A, ring, b = 12.526(8) Angstrom capital A, ring, c = 12.899(10)...

Université de Fribourg

Chemical bonding in molecules and complexes containing d-elements based on DFT

Atanasov, Mihail ; Daul, Claude A. ; Fowe, E. Penka

In: Monatshefte für Chemie / Chemical Monthly, 2005, vol. 136(6), p. 925

Metal–ligand bonding in transition metal halide molecules and complexes with different central ions, oxidations states, and coordination numbers: CrIIIX₆³⁻, CrIVX₄, CrIIX₂ (X = F,Cl,Br,I), MIIICl₆³⁻(M = Mo,W), MIII(H₂O)₆³⁺(M = Cr,Co) and Re₂Cl₈²⁻ has been...

Université de Fribourg

DFT study of mixed-valent Mn(II/III) hexacyanide clusters

Daul, Claude ; Rauzy, Cédrick ; Decurtins, Silvio ; Franz, Patrick ; Hauser, Andreas

In: International Journal of Quantum Chemistry, 2005, vol. 101 (6), p. 753-760

The cubic Prussian blue analogue Mn³[Mn(CN)₆]₂·15H₂O, which has the advantage of being transparent and magnetic (TN = 35 K) at the same time, has been investigated by density functional theory (DFT) calculations. The three-dimensional structure is built of MnII ions linked to MnIII ions by μ-bridging cyanides, to form a crystal structure,...

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

Hydrogen bond stabilization in Diels–Alder transition states: The cycloaddition of hydroxy-ortho-quinodimethane with fumaric acid and dimethylfumarate

Tamilmani, Venkatachalam ; Daul, Claude A. ; Lage Robles, Jaime ; Bochet, Christian G. ; Venuvanalingam, P.

In: Chemical Physics Letters, 2005, vol. 406 (4-6), p. 355-359

DFT investigations on the mechanism of Diels–Alder reactions of a hydroxy-ortho-quinodimethane with fumaric acid derivatives were performed to understand the origin of the syn or anti configuration of the adducts. The diene hydroxyl group and the dieneophile carboxyl group show hydrogen bonding in the transition state, significantly favouring the syn product. This reaction is poorly...