Complexes of Uranyl Ions with Aromatic Di‐ and Tetracarboxylates Involving [Ni(bipy) n ] 2+ ( n = 2, 3) Counterions

Expanding uranyl dicyanoaurate coordination polymers into the second and third dimensions

The solvothermal synthesis and characterization of a three-dimensional, interpenetrated uranyl dicyanoaurate coordination polymer, K2(UO2)2(UO2)2(Au(CN)2)2(O)2(NO3)4, from UO2(NO3)2·6H2O and KAu(CN)2 is described. The structure contains a three-dimensional (3D) lattice of planar tetranuclear uranyl–oxo–nitrate clusters connected by dicyanoaurate linkers, with the rotation of the clusters providing the increased dimensionality. The material undergoes a reversible single-crystal to single-crystal transformation on exposure to water vapour, which is taken up in the channels of the 3D system. A second uranyl dicyanoaurate coordination polymer of the form [UO2(DMSO)3(H2O)(Au(CN)2)][Au(CN)2] was structurally characterized as a linear chain of dicyanoaurate units connected by gold–gold bonds with pendant uranyl–water–DMSO adducts that are hydrogen bonded into a two-dimensional sheet. Both materials exhibit emission arising from both the uranyl moiety and the gold(I) centre and represent the first multidimensional uranyl–dicyanoaurate coordination polymers.

Structure-Directing Effects of Coordinating Solvents, Ammonium and Phosphonium Counterions in Uranyl Ion Complexes with 1,2-, 1,3-, and 1,4-Phenylenediacetates

The three isomers 1,2-, 1,3-, and 1,4-phenylenediacetic acids (1,2-, 1,3-, and 1,4-pdaH₂) have been used to synthesize 16 uranyl ion complexes under solvo-hydrothermal conditions and in the presence of various coligands and organic counterions. The two neutral and homoleptic complexes [UO₂(1,2-pda)]·CH₃CN (1) and [UO₂(1,3-pda)] (2) crystallize as diperiodic assemblies with slightly different coordination modes of the ligands, but the same sql topology. Introduction of the coordinating solvents N-methyl-2-pyrrolidone (NMP) or N,N'-dimethylpropyleneurea (DMPU) in the uranyl coordination sphere produces the four complexes [UO₂(1,2-pda)(DMPU)] (3), [UO₂(1,3-pda)(NMP)] (4), [UO₂(1,4-pda)(NMP)] (5), and [UO₂(1,4-pda)(DMPU)] (6), which are either monoperiodic (4) or diperiodic species with the fes (3 and 5) or 3,4L13 (6) topology. The presence of dimethylammonium cations is associated with the formation of ladder-like monoperiodic polymers with the 1,2 isomer in the complexes [H₂NMe₂]₂[(UO₂)₂(1,2-pda)₃]·H₂O (7) and [H₂NMe₂]₂[(UO₂)₂(1,2-pda)₃]·3H₂O (8), while a conformational change giving the 1,3 and 1,4 isomers a pincer-like geometry favors the formation of dinuclear ring subunits assembled into daisy-chain-like monoperiodic polymers in [H₂NMe₂]₂[(UO₂)₂(1,3-pda)₃]·0.5H₂O (9), [H₂NMe₂]₂[(UO₂)₂(1,4-pda)₃] (10), and the mixed-ligand species [H₂NMe₂]₂[(UO₂)₂(1,2-pda)(1,4-pda)₂] (11). The unique complex including guanidinium cations, [C(NH₂)₃]₂[(UO₂)₂(1,2-pda)₃]·0.5H₂O·CH₃CN (12), crystallizes as a diperiodic polymer with the hcb topology. Due to differences in ligand conformations, the phosphonium-containing complexes [PPh₃Me]₂[(UO₂)₂(1,3-pda)₃] (13) and [PPh₄]₂[(UO₂)₂(1,4-pda)₃] (14) contain ladder-like and daisy-chain-like monoperiodic polymers, respectively, while only the latter geometry is found in the mixed-cation complexes [PPh₃Me][H₂NMe₂][(UO₂)₂(1,4-pda)₃]·H₂O (15) and [PPh₃Me][H₂NMe₂][(UO₂)₂(1,2-pda)(1,4-pda)₂] (16). The influence of ligand conformation and the structure-directing effects of coligands and counterions throughout the series are discussed. The uranyl emission spectra of 14 of the complexes display the usual vibronic fine structure, the peak positions being dependent on the number of equatorial donors.

Zero-, mono- and diperiodic uranyl ion complexes with the diphenate dianion: influences of transition metal ion coordination and differential UVI chelation

Diphenate complexes with uranyl cations are generally of low periodicity (0 or 1), but for one 2-periodic uranyl–Cu^II species.

Tubelike Uranyl-Phenylenediacetate Assemblies from Screening of Ligand Isomers and Structure-Directing Counterions

Reaction of 1,2-, 1,3-, or 1,4-phenylenediacetic acids (1,2-, 1,3-, or 1,4-H₂PDA) with uranyl ions under solvo-hydrothermal conditions and in the presence of [M(L) _n] ^q+ cations, in which M = transition metal cation, L = 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen), n = 2 or 3, and q = 1 or 2, gave 10 complexes which have been crystallographically characterized. The diacetate ligands are bis-chelating and the uranyl cations are tris-chelated in all cases. [UO₂(1,2-PDA)₂Zn(phen)₂]·2H₂O (1) and [UO₂(1,4-PDA)₂Mn(bipy)₂]·H₂O (2) are heterometallic, neutral one-dimensional (1D) coordination polymers in which the carboxylate-coordinated 3d block metal cation is either decorating only (1) or participates in polymer building (2). [Zn(phen)₃][(UO₂)₂(1,3-PDA)₃] (3) and [Ni(phen)₃][(UO₂)₂(1,4-PDA)₃]·H₂O (4), with separate counterions, crystallize as anionic two-dimensional (2D) networks, as does [Cu(bipy)₂][H₂NMe₂][(UO₂)₂(1,4-PDA)₃] (5), which displays parallel 2D interpenetration. The complex [Zn(phen)₃][(UO₂)₂(1,2-PDA)₃]·7H₂O (6) crystallizes as a ladderlike, slightly inflated ribbon. The same topology is found in [Zn(bipy)₃][(UO₂)₂(1,3-PDA)₃] (7), but the larger separation between coordination sites and the coexistence of curved and divergent ligand conformations produce a tubelike assembly. An analogous but more regular and spacious tubular geometry is found in [M(bipy)₃][(UO₂)₂(1,4-PDA)₃], with M = Co (8) or Ni (9), and {Λ-[Ru(bipy)₃]}[(UO₂)₂(1,4-PDA)₃] (10). The disordered counterions in 8 and 9 are replaced by well-ordered, enantiomerically pure chiral counterions in 10. The tubular assemblies formed in 7-10 are characterized by an oblong section and the presence of gaps in the walls, which enable the inclusion of two rows of counterions in the cavity.