RESUMO
A study of the anion-binding properties of three structurally related lanthanide complexes, which all contain chemically identical anion-binding motifs, has revealed dramatic differences in their anion affinity. These arise as a consequence of changes in the substitution pattern on the periphery of the molecule, at a substantial distance from the binding pocket. Herein, we explore these remote substituent effects and explain the observed behaviour through discussion of the way in which remote substituents can influence and control the global structure of a molecule through their demands upon conformational space. Peripheral modifications to a binuclear lanthanide motif derived from α,α'-bis(DO3 Ayl)-m-xylene are shown to result in dramatic changes to the binding constant for isophthalate. In this system, the parent compound displays considerable conformational flexibility, yet can be assumed to bind to isophthalate through a well-defined conformer. Addition of steric bulk remote from the binding site restricts conformational mobility, giving rise to an increase in binding constant on entropic grounds as long as the ideal binding conformation is not excluded from the available range of conformers.
RESUMO
A heterotrimetallic tetranuclear lanthanide complex containing two dysprosium ions, a terbium ion and a europium ion has been prepared by coupling three kinetically stable complexes together using the Ugi reaction. The covalently linked trimetallic system exhibits luminescence from all the different lanthanide centres.
Assuntos
Complexos de Coordenação/química , Disprósio/química , Európio/química , Substâncias Luminescentes/química , Térbio/química , Complexos de Coordenação/síntese química , Substâncias Luminescentes/síntese químicaRESUMO
A binuclear lanthanide complex consisting of two lanthanide binding domains linked by a m-xylyl bridging unit forms very stable 1 : 1 adducts with benzene dicarboxylic acids and their derivatives. The complex with isophthalate derivatives is particularly stable.
