The novel U(VI) and Np(VI) mixed-ligand complexes based on quinaldic acid zwitterion

Varied role of organic carboxylate dizwitterions and anionic donors in mixed-ligand uranyl ion coordination polymers

“…zwitterionic, polycarboxylate ligand to a neutral uranyl carboxylate could be used to generate a triperiodic framework defining cavities suited to neutral guest exchange, to add to the presently known unique example of a triperiodic, cationic uranyl polymer derived from a trizwitterion ligand alone which has been shown to undergo anion exchange. 3 This requires the formation of mixed (neutral plus anionic) carboxylate complexes and while the deposition from solution of a complex of a labile metal ion such as uranyl ion is determined by its solubility and not necessarily just its solution stability, it is encouraging that the known structural chemistry of monocarboxylate zwitterions with uranyl ion 4 closely parallels that of monocarboxylate anions, indicating that the donor capacity of the two carboxylate forms must be similar. In fact, in our previous studies of complexation of uranyl ion by metal-containing zwitterionic carboxylate ligands, 5 combination of a zwitterion source with a polycarboxylic acid in reaction with uranyl ion under solvo-hydrothermal conditions invariably led to mixed-ligand complex products.…”