Two mononuclear uranyl complexes, [UO2 L1 ] (1) and [UO2 L2 ]⋅0.5 CH3 CN⋅0.25 CH3 OH (2), have been synthesized from two multidentate N3 O4 donor ligands, N,N'-bis(5-methoxysalicylidene)diethylenetriamine (H2 L1 ) and N,N'-bis(3-methoxysalicylidene)diethylenetriamine (H2 L2 ), respectively, and have been structurally characterized. Both complexes 1 and 2 showed a reversible UVI /UV couple at -1.571 and -1.519 V, respectively, in cyclic voltammetry. The reduction potential of the UVI /UV couple shifted towards more positive potential on addition of Li+ , Na+ , K+ , and Ag+ metal ions to acetonitrile solutions of complex 2, and the resulting potential was correlated with the Lewis acidity of the metal ions and was also justified by theoretical DFT calculations. No such shift in reduction potential was observed for complex 1. All four bimetallic products, [UO2 L2 Li0.5 ](ClO4 )0.5 (3), [UO2 L2 Na(ClO4 )]2 (4), [UO2 L2 Ag(NO3 )(H2 O)] (5), and [(UO2 L2 )2 K(H2 O)2 ]PF6 (6), formed on addition of the Li+ , Na+ , Ag+ , and K+ metal ions, respectively, to acetonitrile solutions of complex 2, were isolated in the solid state and structurally characterized by single-crystal X-ray diffraction. In all the species, the inner N3 O2 donor set of the ligand encompasses the equatorial plane of the uranyl ion and the outer open compartment with O2 O'2 donor sites hosts the second metal ion.
Keywords: bimetallic complexes; density functional calculations; electrochemistry; structure elucidation; uranium.
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