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Characterizing vibrational motion beyond internal coordinates

Hug, Werner ; Fedorovsky, Maxim

In: Theoretical Chemistry Accounts, 2008, vol. 119, no. 1-3, p. 113-131

Université de Fribourg

Efficient calculation of ROA tensors with analytical gradients and fragmentation

Thorvaldsen, Andreas J. ; Gao, Bin ; Ruud, Kenneth ; Fedorovsky, Maxim ; Zuber, Gérard ; Hug, Werner

In: Chirality, 2012, vol. 24, no. 12, p. 1018–1030

We present the results of calculations of Raman optical activity spectra of sizable systems from optical tensors of the fragments, the tensors calculated by an analytic approach at the time-dependent Hartree–Fock level of theory. The analytic approach permits large basis sets which, together with the limited geometrical extent of the fragments, obviates the need for the use of London-type...

Université de Fribourg

Total synthesis of Junionone, a natural monoterpenoid from Juniperus communis L., and determination of the absolute configuration of the naturally occurring enantiomer by ROA spectroscopy

Lovchik, Martin A. ; Fráter, Georg ; Goeke, Andreas ; Hug, Werner

In: Chemistry & Biodiversity, 2008, vol. 5, no. 1, p. 126-139

Recently, we reported a novel access to 2,2-diethyl-3-[(E/Z)-prop-1-en-1-yl]cyclobutanone by an intramolecular nucleophilic substitution with allylic rearrangement (SNi′) of (E)-6-chloro-3,3-diethylhept-4-en-2-one. The ring closure reaction was found to proceed with selective syn-displacement of the leaving group. This method was now applied...

Université de Fribourg

Characterizing vibrational motion beyond internal coordinates

Hug, Werner ; Fedorovsky, Maxim

In: Theoretical Chemistry Accounts: Theory, Computation, and Modeling, 2008, vol. 119, no. 1-3, p. 113-131

We present a procedure for the decomposition of the normal modes of a composite system, including its rotations and translations, into those of fragments. The method permits—by the cross-contraction of dyads of mass-weighted displacement vectors, without recourse to valence coordinates—the direct comparison of nuclear motions of structurally similar but otherwise arbitrary fragments of...

Université de Fribourg

1,4-Dimethylenespiropentane: a unique model system for studying fermi resonance in raman optical activity

Hug, Werner ; Haesler, Jacques ; Kozhushkov, Sergei I. ; Meijere, Armin de

In: ChemPhysChem, 2007, vol. 8, no. 8, p. 1161 - 1169

The C₂-symmetric title compound, a small, rigid hydrocarbon molecule with two distinct, strongly interacting vibrational chromophores, represents a unique model system for testing computational approaches to Raman optical activity (ROA) beyond the isolated molecule and the harmonic approximation. We show that the experimental Raman and ROA spectra are marked by the presence of strong Fermi...

Université de Fribourg

Analysis of the VROA signals of helical heptasilanes using an atomistic approach

Liégeois, Vincent ; Quinet, Olivier ; Champagne, Benoît ; Haesler, Jacques ; Zuber, Gérard ; Hug, Werner

In: Vibrational Spectroscopy, 2006, vol. 42, no. 2, p. 309-316

The VROA signatures of different helical conformers of heptasilane have been analyzed using an atomistic approach. Based on ab initio VROA quantities, the decomposition scheme and its representation under the form of group coupling matrices enable us to highlight the dominant role of the Si atoms for the modes studied. The sum of the contributions from H atoms, on the other hand, is generally...

Université de Fribourg

Is the vibrational optical activity of (R)-[²H₁, ²H₂, ²H₃]-neopentane measurable?

Hug, Werner ; Haesler, Jacques

In: International Journal of Quantum Chemistry, 2005, vol. 104(5), p. 695

The compound, (R)-[²H₁, ²H₂, ²H₃]-neopentane, with its Td symmetric electron distribution, is the archetype of molecules that owe their chirality exclusively to an asymmetric distribution of the masses of their nuclei. It has nine rotamers, which fall into two classes, one where the interchange of hydrogen and deuterium nuclei leads to an identical rotamer, and...

Université de Fribourg

Computational interpretation of vibrational optical activity: The ROA spectra of (4S)-4-Methylisochromane and the (4S)-Isomers of Galaxolide®

Zuber, Gérard ; Hug, Werner

In: Helvetica Chimica Acta, 2004, vol. 87(9), p. 2208-2234

The reliable computation of Raman-optical-activity (ROA) spectra of molecules of the size of the title compounds has, until now, not been possible. We show that our rarefied basis sets yield results in good agreement with the experimental data for (4S)-4-methylisochromane (=(4S)-3,4-dihydro-4-methyl-1H-2-benzopyran; 1), provided the equilibrium between the...