Saccharified Uranyl Ions: Self-Assembly of UO22+ into Trinuclear Anionic Complexes by the Coordination of Glucosamine-Derived Schiff Bases

The reaction of UO2(OAc)(2) . 2H(2)O with the biologically inspired ligand 2-salicylidene glucosamine (H2L1) results in the formation of the anionic trinuclear uranyl complex [(UO2)(3)(mu(3)-O)(L-1)(3)](2-) (1(2-)), which was isolated in good yield as its Cs-salt, [Cs](2)1. Recrystallization of [Cs](2)1 in the presence of 18-crown-6 led to formation of a neutral ion pair of type [M(18-crown-6)](2)1, which was also obtained for the alkali metal ions Rb+ and K+ (M=Cs, Rb, K). The related ligand, 2-(2-hydroxy-1-naphthylidene) glucosamine (H2L2) in a similar procedure with Cs+ gave the corresponding complex [Cs(18-crown-6)](2)[(UO2)(3)(mu(3)-O)(L-2)(3) ([Cs(18-crown-6)](2)2). From X-ray investigations, the [(UO2)(3)O(L-n)(3)](2-) anion (n=1, 2) in each complex is a discrete trinuclear uranyl species that coordinates to the alkali metal ion via three uranyl oxygen atoms. The coordination behavior of H2L1 and H2L2 towards UO22+ was investigated by NMR, UV/Vis spectroscopy and mass spectrometry, revealing the in situ formation of the 1(2-) and 2(2-)dianions in solution.

Automated summary

The reaction between UO2 (OAc) (2) .2H(2)O and the biologically inspired ligand H2L1 resulted in the formation of trinuclear uranyl complexes, which were isolated as Cs salts in good yield. Recrystallization in the presence of 18-crown-6 led to the formation of neutral ion pairs with alkali metal ions like Cs+, Rb+ and K+. X-ray investigations revealed the discrete trinuclear uranyl species in each complex, coordinating to the alkali metal ions through three uranyl oxygen atoms. Coordination behavior of H2L1 and H2L2 towards UO22+ was studied using NMR, UV/Vis spectroscopy and mass spectrometry, showing the in situ formation of the dianions in solution.