title: Selective self-assembly of hexameric homo- and heteropolymetallic lanthanide wheels: synthesis, structure, and photophysical studies.
abstract: A rational approach to the formation of pure heteropolymetallic lanthanide complexes that uses a two-step assembly strategy and exploits the different size requirements of the two metals included in the final structure is described. The investigation of the assembly of [LnL2](Otf) (L = 2,2':6',2' '-terpyridine-6-carboxylate) complexes into hexametallic rings hosting an additional hexacoordinated lanthanide cation was crucial for the development of this strategy. The formation and size of the cyclic assembly are controlled by the ionic radius and by the coordination number of the lanthanides. The rather high luminescence quantum yield of the heptaeuropium complex (25%) indicates that the ring structure is well adapted to include highly luminescent lanthanide complexes in nanosized architecture. The use of a stepwise synthetic strategy leads to the selective assembly of large heteropolymetallic rings. The addition of a smaller lanthanide ion to the [EuL2](Otf) complex in anhydrous acetonitrile leads selectively to heterometallic species with the Eu ions located on the peripheral sites and the smaller ion occupying only the central site. The high selectivity is the result of the different size requirements of the two metal sites present in the cyclic structure. The heterometallic structure of the isolated [Lu subset (EuL2)6](Otf)9 complex was confirmed by X-ray diffraction and by high resolution solid-state photophysical studies. The described synthetic approach allowed us to obtain the first example of selective assembly of two different lanthanide ions in a large polymetallic structure characterized in solution and in the solid state and will make the isolation of planned dimetallic combinations presenting different lanthanide emitters in the peripheral sites possible.
authors.affiliation: Laboratoire de Reconnaissance Ionique et Chimie de Coordination, Service de Chimie Inorganique et Biologique (UMR-E 3 CEA-UJF), Département de Recherche Fondamentale sur la Matière Condensée SCIB/DRFMC/DSM CEA-Grenoble, Grenoble, France.
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Chen
authors.forename: Yann
authors.initials: Y
authors.lastname: Bretonnière
authors.forename: Jacques
authors.initials: J
authors.lastname: Pécaut
authors.forename: Daniel
authors.initials: D
authors.lastname: Imbert
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Bünzli
authors.forename: Marinella
authors.initials: M
authors.lastname: Mazzanti
mesh_terms: D028581:Lanthanoid Series Elements / Q000737:chemistry*; D049449:Luminescence; D047028:Macrocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D028581:Lanthanoid Series Elements; D047028:Macrocyclic Compounds; D009942:Organometallic Compounds