title: Enantiopure Alleno-Acetylenic Helicages Containing Multiple Binding Sites.
abstract: Enantiopure alleno-acetylenic ligands, containing two chiral allene moieties, assemble diastereoselectively with zinc(II) ions to form trinuclear triple-stranded helicates, featuring two internal cavity binding sites ("helicages"). The addition of cycloalkanes or heteroalicycles results in inclusion complex formation with two guest molecules bound in one helicate. While no positive allosteric effects were observed, the chiroptical responses increased strongly upon complexation, with guest-induced circular dichroism (ICD) signals reaching up to ΔΔϵ=205 m-1cm-1. The highest binding affinity was observed for six-membered 1,4-dichalcogens, with binding constants (K1) of up to 2400 m-1for 1,4-oxathiane in CD3OD. The X-ray co-crystal structure of 1,4-dioxane bound to a dinuclear triple-stranded helicate confirmed the previously predicted guest orientation inside the helicage, with the two oxygen atoms facing towards the electropositive zinc(II) metal centers.
authors.affiliation: Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, 8093, Zurich, Switzerland.|The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra, Givat Ram, Jerusalem, 91904, Israel.
authors.forename: Ori
authors.initials: O
authors.lastname: Gidron
authors.affiliation: Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, 8093, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Jirásek
authors.affiliation: Laboratorium für Anorganische Chemie, ETH Zurich, Vladimir-Prelog-Weg 1, 8093, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Wörle
authors.affiliation: Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, 8093, Zurich, Switzerland. diederich@org.chem.ethz.ch.
authors.forename: François
authors.initials: F
authors.lastname: Diederich
keywords: alleno-acetylenes; chiroptical chemosensors; host-guest complexation; supramolecular chemistry; triple helicates