Combinatorial Multinuclear NMR and X-ray Diffraction Studies of Uranium(VI)-Nucleotide Complexes

The complex formation of uranium(VI) with four nucleotides, adenosine- (AMP), guanosine-
(GMP), uridine- (UMP), and cytidine-monophosphate (CMP), has been studied in the alkaline pH range
(8.5−12) by 1H, 31P, 13C, and 17O NMR spectroscopy, providing spectral integral, chemical shift, homo-
and heteronuclear coupling, and diffusion coefficient data. We find that two and only two complexes are
formed with all ligands in the investigated pH region independently of the total uranium(VI) and ligand
concentrations. Although the coordination of the 5‘-phosphate group and the 2‘- and 3‘-hydroxyl groups of
the sugar unit to the uranyl ions is similar to that proposed earlier (“Feldman complex”), the number and
the structures of the complexes are different. The uranium-to-nucleotide ratio is 6:4 in one of the complexes
and 3:3 in the other one, as unambiguously determined by a combinatorial approach using a systematic
variation of the ratio of two ligands in ternary uranium(VI)-nucleotide systems. The structure of the 3:3
complex has been determined by single-crystal diffraction as well, and the results confirm the structure
proposed by NMR in aqueous solution. The results have important implications on the synthesis of
oligonucleotides.