Counter-ion control of structure in uranyl ion complexes with 2,5-thiophenedicarboxylate

Abstract

2,5-Thiophenedicarboxylic acid (H₂TDC) was reacted with uranyl nitrate under solvo-hydrothermal conditions with acetonitrile or N-methyl-2-pyrrolidone as organic co-solvents and different combinations of d-block metal ions and N-donating chelators. The complexes [Ni(bipy)₃][(UO₂)₂(TDC)₂(HTDC)(NO₃)]·NMP·H₂O (1) and [Co((NH₂)₂sar)][(UO₂)₂(TDC)₂(HTDC)₂]·Cl·6H₂O (2) (bipy = 2,2′-bipyridine, sar = sarcophagine = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane), the latter containing the enantiomerically pure Λ-isomer of the counter-ion, crystallize as one-dimensional coordination polymers in which the TDC²⁻ ligands are bis-chelating and the HTDC⁻ ones are mono-chelating and terminal. Two-dimensional (2D) honeycomb networks with all ligands bis-chelating are generated in the two isomorphous complexes [Fe(phen)₃]₂[(UO₂)₄(TDC)₆][UO₂(NMP)₂(NO₃)₂]·2NMP (3) and [Ni(phen)₃]₂[(UO₂)₄(TDC)₆][UO₂(NMP)₂(NO₃)₂]·NMP (4) (phen = 1,10-phenanthroline), while a 2D assembly with a tessellation of 4- and 8-membered rings (fes topological type) is formed in [Ag(CH₃CN)₃]₂[(UO₂)₂(TDC)₃]·H₂O (5). Finally, [Ag(bipy)₂]₅[(UO₂)₄(TDC)₆]·NO₃·6H₂O (6) comprises planar honeycomb networks which generate a three-dimensional (3D) architecture through inclined 2D → 3D polycatenation; the [Ag(bipy)₂]⁺ cations are assembled into columns held by π-stacking and weak argentophilic interactions, which occupy the channels formed by the intersecting layers. Complete quenching of uranyl luminescence occurs in complexes 1–4 and only 6 displays an emission spectrum in the solid state showing the usual well-resolved vibronic fine structure.