title: Influence of linker geometry on uranyl complexation by rigidly linked bis(3-hydroxy-N-methyl-pyridin-2-one).
abstract: A series of bis(3-hydroxy-N-methyl-pyridin-2-one) ligands was synthesized, and their respective uranyl complexes were characterized by single crystal X-ray diffraction analyses. These structures were inspected for high-energy conformations and evaluated using a series of metrics to measure co-planarity of chelating moieties with each other and the uranyl coordination plane, as well as to measure coordinative crowding about the uranyl dication. Both very short (ethyl, 3,4-thiophene and o-phenylene) and very long (alpha,alpha'-m-xylene and 1,8-fluorene) linkers provide optimal ligand geometries about the uranyl cation, resulting in planar, unstrained molecular arrangements. The planarity of the rigid linkers also suggests there is a degree of pre-organization for a planar coordination mode that is ideal for uranyl-selective ligand design. Comparison of intramolecular N(amide)-O(phenolate) distances and (1)H NMR chemical shifts of amide protons supports earlier results that short linkers provide the optimal geometry for intramolecular hydrogen bonding.
authors.affiliation: Department of Chemistry, University of California at Berkeley, Berkeley, California 94720-1460, USA.
authors.forename: Géza
authors.initials: G
authors.lastname: Szigethy
authors.forename: Kenneth N
authors.initials: KN
authors.lastname: Raymond