title: Multifunctional and reactive enantiopure organometallic helicenes: tuning chiroptical properties by structural variations of mono- and bis(platinahelicene)s.
abstract: Acetylacetonato-platina[6]- and -platina[7]helicenes have been prepared from 2-pyridyl-substituted benzophenanthrene ligands by following a two-step cycloplatination reaction. The photophysical properties (UV-visible absorption and emission behavior) and chiroptical properties (circular dichroism and molar rotation) of the resolved enantiomers have been measured. These metallahelicenes constitute a novel family of easily accessible helicene derivatives that exhibit large and tuneable chiroptical properties that can be rationalized theoretically and compared to the parent [6]- and [7]carbohelicenes. Furthermore, they are red phosphors at room temperature and their large chiroptical properties can be modulated by oxidation of the metal center to Pt(IV). Hetero- and homochiral diastereomeric bis(metallahelicene)s that possess a rare Pt(III)-Pt(III) scaffold bridged by benzoato ligands have also been prepared. It is shown that the heterochiral (P,M)-bis(Pt(III)-[6]helicene) 9a(1) can isomerize into the homochiral (P,P)- and (M,M)-bis(Pt(III)-[6]helicene) 9a(2). Spectral assignments and an analysis of the optical rotation of these systems were made with the help of time-dependent density functional theory. The calculations highlight the contributions of the metal centers to the chiroptical properties. For 9a(1) and 9a(2), σ-π conjugation between the helicenes and the Pt-Pt moiety may contribute strongly to the optical rotation and electronic circular dichroism.
authors: Sciences Chimiques de Rennes, UMR 6226, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors: Emmanuel
authors: E
authors: Anger
authors: Mark
authors: M
authors: Rudolph
authors: Lucie
authors: L
authors: Norel
authors: Samia
authors: S
authors: Zrig
authors: Chengshuo
authors: C
authors: Shen
authors: Nicolas
authors: N
authors: Vanthuyne
authors: Loïc
authors: L
authors: Toupet
authors: J A Gareth
authors: JA
authors: Williams
authors: Christian
authors: C
authors: Roussel
authors: Jochen
authors: J
authors: Autschbach
authors: Jeanne
authors: J
authors: Crassous
authors: Régis
authors: R
authors: Réau