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

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

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...