Blanc SIMI 4 - Blanc - SIMI 4 - Physique des milieux condensés et dilués

Symmetry breaking and birth of chirality in molecular films : an approach with nonlinear optics – DynaChir

Submission summary

The Dynachir project addresses the fundamental question of the birth of homochirality in molecular systems. This will be achieved with an innovative approach using nonlinear optical techniques in the frequency and time domain to investigate symmetry breaking in films of chiral and achiral molecules. The consortium is constituted by four partners and managed by E. Benichou (LASIM, UCB Lyon 1).
The project first entails the fabrication by Pulsed Laser Deposition (PLD) of binaphthols and helicenes films, two chiral compounds. Monolayer and multilayer films of these compounds are known to remain isotropic and preserve the chiral properties of the initial molecules. Films of different enantiomeric ratio will thus be prepared and their stability towards segregation into domains investigated. In parallel, chiral films of achiral organic molecular compounds formed at the air-water interface in a Langmuir trough by lateral compression and subsequently transferred onto solid glass substrates will also be prepared. These films are known to segregate into enantiomerically pure microscopic domains. Access to the chiral and achiral compounds will be granted through close collaborations outside the consortium with ENS Lyon and the ICCAS in Beijing (China). The samples have already been realized and are therefore known to be available.
In the frequency domain, Circular Dichroism Second Harmonic and Sum Frequency Generation (CD-SHG and CD-SFG) will be used to study the segregation process using a microscopic geometry adapted to the size of the domains. CD-SHG and CD-SFG are known to be two powerful techniques to observe chirality since the susceptibility tensor elements associated with this process can be isolated with specific polarization configurations. CD-SFG further supports a vibrational analysis specific to the molecular compounds when one of the exciting photons is tuned over a vibrational resonance. In the time domain, time-resolved CD spectroscopy will be conducted for films of varying enantiomeric ratio. It is indeed known that in the excited state, binaphthols have weaker chiral properties than in their fundamental state owing to a spatial intramolecular re-orientation. Hence, time-resolving the relaxation process will give a hint on how chirality appears over the course of time and how it can be imprinted on the environment. Such an experiment will be performed for one enantiomer diluted into a film enriched in the other enantiomeric form.
Finally, the current models available will be confronted to the experimental results and refined to correctly account for the observations.

Project coordination

Emmanuel BENICHOU (Laboratoire de Spectrométire Ionique et Moléculaire) –

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


LOB Laboratoire d'Optique et Biosciences
LPCML - CNRS Laboratoire de Physico-Chimie des Matériaux Luminescents
IPCMS Institut de Physique et Chimie des Matériaux de Strasbourg
LASIM - CNRS Laboratoire de Spectrométire Ionique et Moléculaire

Help of the ANR 425,709 euros
Beginning and duration of the scientific project: March 2013 - 42 Months

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