title: Self-assembly of the first discrete 3d-4f-4f triple-stranded helicate.
abstract: The connection of an additional bidentate chelating unit at the extremity of a segmental bis-tridentate ligand in L5 provides an unprecedented sequence of binding sites for the self-assembly of heterometallic 3d-4f triple-stranded helicates. Thorough thermodynamic and structural investigations in acetonitrile show the formation of intricate mixtures of complexes when a single type of metal (3d or 4f) is reacted with L5. However, the situation is greatly simplified when Zn(II) (3d-block) and Lu(III) (4f-block) are simultaneously coordinated to L5, thus leading to only two identified species: the target C(3)-symmetrical trinuclear triple-stranded d-f-f helicate HHH-[ZnLu(2)(L5)(3)](8+) and a tetranuclear double-stranded complex [Zn(2)Lu(2)(L5)(2)](10+). Interestingly, the removal of Zn(II) from the former triple-helical complex has only a minor effect on the coordination of Lu(III), and translational autodiffusion coefficients show a simple reduction of the length of the molecular rigid cylinder from L = 2.7 nm in HHH-[ZnLu(2)(L5)(3)](8+) to L = 2.3 nm in HHH-[Lu(2)(L5)(3)](6+). Finally, the complete thermodynamic picture provides five novel stability macroconstants containing information about short-range (ca. 9 A) and long-range (ca. 18 A) intramolecular intermetallic d-f and f-f interactions.
authors.affiliation: Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, 30 quai E. Ansermet, CH-1211 Geneva 4, Switzerland. thomas.riis-johannessen@epfl.ch
authors.forename: Thomas
authors.initials: T
authors.lastname: Riis-Johannessen
authors.forename: Gérald
authors.initials: G
authors.lastname: Bernardinelli
authors.forename: Yaroslav
authors.initials: Y
authors.lastname: Filinchuk
authors.forename: Sarah
authors.initials: S
authors.lastname: Clifford
authors.forename: Natalia
authors.initials: N
authors.lastname: Dalla Favera
authors.forename: Claude
authors.initials: C
authors.lastname: Piguet