Saccharified Uranyl Ions: Self-Assembly of UO2 2+ into Trinuclear Anionic Complexes by the Coordination of Glucosamine-Derived Schiff Bases.

Abstract

The reaction of UO2(OAc)2 ⋅ 2H2O with the biologically inspired ligand 2‐salicylidene glucosamine (H2 L1) results in the formation of the anionic trinuclear uranyl complex [(UO2)3(μ3‐O)(L1)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 (H2 L2) in a similar procedure with Cs+ gave the corresponding complex [Cs(18‐crown‐6)]2[(UO2)3(μ3‐O)(L2)3 ([Cs(18‐crown‐6)]2 2). From X‐ray investigations, the [(UO2)3O(Ln)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 H2 L1 and H2 L2 towards UO2 2+ 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.