Charge‐Assisted Hydrogen‐Bonding and Crystallization Effects within UVI Glycine Compounds

Abstract

UVI chemistry is dominated by the uranyl (UO2)2+ cation, in which the oxo group is essentially passivated by a triple bond to the metal center. Weak interactions between the oxo group Lewis acids or hydrogen‐bond donors can be observed in extended solids, but there is little understanding of how the uranyl bond is affected by these additional forces. In the current study, the influence of charge‐assisted hydrogen‐bonding and crystallization effects on the uranyl oxo bond is explored through the synthesis and characterization of four uranyl compounds: [(UO2)3(Gly)2(O)2(OH)2](H2O)1.5 (UG1b), [(UO2)4(Gly)3(For)(O)3(OH)](H2O)6.5 (UGFA1a), [(UO2)8(Gly)6(For)2(O)6(OH)2](H2O)10 (UGFA1b), and [(UO2)4(Gly)3(O)3(OH)2](HFor)(H2O)9.45 (UGFA2). Each of these compounds contains uranyl infinite chain topologies that are built upon trimeric or tetrameric repeating units and are linked through multiple hydrogen‐bonding interactions to the uranyl oxo groups. The impact on the uranyl bond was explored through an examination of hydrogen‐bonding donor–acceptor distances and the calculation of force constants obtained from Raman and IR spectral bands. The stretching force constants are lower with cooperative hydrogen bonds to the uranyl oxo groups. This suggests that these interactions are important and can combine with crystallization effects to impact the uranyl oxo bond.