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Chirality/chiroptical properties

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J. Crassous - L. Favereau - T. Reynaldo

1 - Synthesis and coordination of phosphorated heterohelicenes; impact of the metal on the chiroptical properties

In our group, we are currently preparing azahelicenes bearing phospholes and studying the coordination of such P,N chelates to metallic ions, in order to conceive new chiral molecules with original topologies. This strategy enables to prepare a diversity of structures simply by changing the metallic ion. By this method, we have been able to prepare enantiomerically pure aza[6]helicene-phospholes and their corresponding PdII and CuI complexes (see Figure), which displayed high molar rotations and circular dichroism values. Of particular interest the impact of the metal on the chiroptical properties was investigated by theoretical calculations.

Collaborations

  • Pr. Christian Roussel, Dr. Nicolas Vanthuyne, Faculté des Sciences de Saint Jérôme, Marseille : séparations par HPLC chirale.
  • Pr. Jochen Autschbach, University of Buffalo, USA, calculs théoriques des propriétés chiroptiques (CD, ORD).

2 - Metallahelicenes: first organometallic helicenes

We have recently demonstrated that it was possible to use organometallic chemistry to create a helicene incorporating a metallic ion into its helical backbone. Such method allowed the preparation of the first platinahelicenes and provided these new chiral molecules with new properties such as phosphorescence at room temperature. Moreover these metallahelicenes display huge chiroptical properties (molar rotation and circular dichroism) and can be prepared in a few steps. We hope that this method will be useful to create a diversity of helicenes incorporating metallic ions.

Collaborations

  • Pr. Christian Roussel, Dr. Nicolas Vanthuyne, Faculté des Sciences de Saint Jérôme, Marseille, chiral separation by HPLC.
  • Pr. Jochen Autschbach, University of Buffalo, USA
  • Pr. J. A. Gareth Williams, University of Durham (England)

3 - Chiral molecules for parity violation (PV) experiments

Since several years, Jeanne Crassous is involved in the search of parity violation (PV) or parity non conservation (PNC) effects in chiral molecules, in collaboration with physicists, theoretical chemist and spectroscopists. This project aims at measuring the tiny energy difference which exists between two enantiomers of a chiral molecule. While for a long time the molecule of choice has been the bromochlorofluoromethane (see Figure) we are now currently investigating simple chiral oxorhenium complexes.

Collaborations

  • Dr Laure Guy, ENS Lyon: Analyse de molécules chirales.
  • Pr. Christian Roussel, Dr. Nicolas Vanthuyne, Faculté des Sciences de Saint Jérôme, Marseille : séparation by HPLC chirale.
  • Pr Larry Nafie, Pr Tess Freedman, Syracuse University (USA) : mesures VCD
  • Dr. Christian Chardonnet, Pr. Anne Amy-Klein, Dr. Christophe Daussy, Dr. Benoît Darquié, LPL Villetaneuse : mesures d’effets de violation de parité par spectroscopie IR à très haute résolution.
  • Dr. Trond Saue, Université de Strasbourg: calculs relativistes d’effets de violation de parité dans les molécules.uet (PhLAM Lille) : mesures spectroscopiques.