title: Ruthenium-Grafted Vinylhelicenes: Chiroptical Properties and Redox Switching.
abstract: The properties of mono- and bis-Ru-vinyl[6]helicene complexes (2 a and 2 b, respectively), recently synthesized by using molecular engineering of helicenes based on the grafting of lateral organometallic substituents on the π-helical backbone through a vinyl bridge, are presented. These helicene derivatives are thoroughly characterized, with special attention given to their chiroptical properties and redox switching activity. The UV/Vis and electronic circular dichroism (ECD) spectra of P and M enantiopure species, both in the neutral and oxidized states ([2 a](·+), [2 b](·+), and [2 b](2+)), are analyzed with the aid of quantum-chemical calculations. The extended π-conjugation facilitated by the vinyl moiety, clearly visible in the electronic structures of 2 a,b, introduces new active bands in the ECD spectra that consequently lead to a significant increase in optical rotation of Ru-vinylhelicenes compared with the organic precursors. The vibrational circular dichroism (VCD) spectra were measured and calculated for both the organic and organometallic species and constitute the first examples of VCD for metal-based helicene derivatives. Finally, the redox-triggered chiroptical switching activity of 2 a,b is examined in detail by using ECD spectroscopy. The modifications of the ECD spectra in the UV/Vis and NIR region are well reproduced and rationalized by calculations.
authors.affiliation: Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, R. Ingardena 3, 30-060 Krakow (Poland).
authors.forename: Monika
authors.initials: M
authors.lastname: Srebro
authors.affiliation: Institut des Sciences Chimiques de Rennes UMR 6226, CNRS Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France).
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Anger
authors.affiliation: Department of Chemistry, 312 Natural Sciences Complex, University at Buffalo, State University of New York, Buffalo, NY 14260-3000 (USA).
authors.forename: Barry
authors.initials: B
authors.lastname: Moore
authors.affiliation: Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille (France).
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vanthuyne
authors.affiliation: Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille (France).
authors.forename: Christian
authors.initials: C
authors.lastname: Roussel
authors.affiliation: Institut des Sciences Chimiques de Rennes UMR 6226, CNRS Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France).
authors.forename: Régis
authors.initials: R
authors.lastname: Réau
authors.affiliation: Department of Chemistry, 312 Natural Sciences Complex, University at Buffalo, State University of New York, Buffalo, NY 14260-3000 (USA). jochena@buffalo.edu.
authors.forename: Jochen
authors.initials: J
authors.lastname: Autschbach
authors.affiliation: Institut des Sciences Chimiques de Rennes UMR 6226, CNRS Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France). jeanne.crassous@univ-rennes1.fr.
authors.forename: Jeanne
authors.initials: J
authors.lastname: Crassous
keywords: chiroptical properties; helicenes; organometallic complexes; redox switches; ruthenium complexes