A New Form of Triple-Stranded Helicate Found in Uranyl Complexes of Aliphatic α,ω-Dicarboxylates
Résumé
The reaction of uranyl ions with azelaic or dodecanedioic acids under solvohydrothermal conditions leads to crystallization of anionic dinuclear cage compounds with [M(bipy/phen) 3 ] 2+ counterions (M = 3d-block cation), while the smaller suberic acid yields heterometallic metallacycles. Complexes with the longer aliphatic chains are the first triple-stranded helicates reported in actinide chemistry. A lthough the synthesis of discrete metallamacrocycles and metallacages through coordination-driven self-assembly involving d-block metal ions has reached a high level of sophistication, 1 such closed species remain rare in uranyl ion chemistry, with only a few examples involving organic ligands 2,3 apart from the remarkable family of peroxo-linked nanospheres. 4 It is particularly notable that no uranyl-based helicate 5 has been reported until now, although the quasi-planar coordination environment required by this linear cation does not preclude the formation of such species with polytopic ligands displaying widely spaced coordination sites. In the course of an investigation of the complexes formed by uranyl ions with large carboxylic diacids under solvohydrothermal conditions and in the presence of [M(bipy/phen) 3 ] 2+ counterions (where M = 3d-block metal cation, bipy = 2,2′-bipyridine, and phen = 1,10-phenanthroline), 6