Anionic uranyl ion complexes with pyrazinetetracarboxylate: Influence of structure-directing cations

Abstract

Pyrazine-2,3,5,6-tetracarboxylic acid (H4PZTC) has been used to synthesize three uranyl ion complexes under solvo-hydrothermal conditions and in the presence of additional cations as structure-directing agents. The complex [C(NH2)3]2[UO2(PZTC)]⋅2H2O (1) displays double ONO-chelation of uranyl, resulting in the formation of a monoperiodic coordination polymer, further association being provided by guanidinium and water hydrogen bonding. The PZTC4– ligand in [Co(en)3][UO2(PZTC)](NO3)⋅H2O (2) is bound to three uranyl cations, one of them ONO-chelated and the others bound to monodentate carboxylate donors, and the polymer formed is triperiodic with the ths topology. The ONO sites in the heterometallic complex [UO2Ag2(PZTC)] (3) are occupied by Ag+ cations, further carboxylate bonding to uranyl and Ag+ cations, as well as oxo bonding of uranyl to Ag+, resulting in the formation of an intricate triperiodic framework in which uranyl cations and PZTC4– alone give a triperiodic polymer with the lvt topology displaying double interpenetration, the Ag+ cations connecting the two networks into a single assembly.