Structure-Directing Effects of Counterions in Uranyl Ion Complexes with Long-Chain Aliphatic α,ω-Dicarboxylates: 1D to Polycatenated 3D Species.

Nine uranyl ion complexes were synthesized under (solvo-)hydrothermal conditions using α,ω-dicarboxylic acids HOOC-(CH2 ) n-2 -COOH (H2 C n, n = 6-9) and diverse counterions. Complexes [PPh4 ][UO2 (C6)(NO3 )] (1) and [PPh4 ][UO2 (C8)(NO3 )] (2) contain zigzag one-dimensional (1D) chains, with further polymerization being prevented by the terminal nitrate ligands. [PPh3 Me][UO2 (C7)(HC7)] (3) crystallizes as a 1D polymer with a curved section, with hydrogen bonding of the uncomplexed carboxylic groups giving rise to formation of 3-fold interpenetrated two-dimensional (2D) networks. [PPh4 ][H2 NMe2 ][(UO2 )2 (C7)3 ] (4) and [PPh3 Me]2 [(UO2 )2 (C8)3 ] (5) contain 1D chains, either ladder-like or containing doubly bridged dimers, while [PPh3 Me]2 [(UO2 )2 (C9)3 ]·2H2 O (6) displays interdigitated, strongly corrugated honeycomb 2D nets. Ladder-like 1D polymers in [Cu( R,S-Me6 cyclam)][(UO2 )2 (C7)2 (C2 O4 )]·4H2 O (7) are associated into layers by the hydrogen bonded counterions, whereas the [Ni(cyclam)]2+ moieties are part of the 2D polymeric arrangement in [(UO2 )2 (C7)2 (HC7)2 Ni(cyclam)]·2H2 O (8) because of axial coordination of the nickel(II) center, with hydrogen bonding mediated by water molecules generating a three-dimensional (3D) net. [(UO2 )2 K2 (C7)3 (H2 O)]·0.5H2 O (9) contains convoluted uranyl dicarboxylate 2D subunits, which generate a 3D framework through 2D → 3D parallel polycatenation similar to that previously found in [NH4 ]2 [(UO2 )2 (C7)3 ]·2H2 O; further linking of these subunits is provided by bonding of the potassium cations to carboxylate and uranyl oxido groups. The solid-state emission spectra of complexes 1-6 and 9 display maxima positions typical of hexacoordinated uranyl carboxylate complexes, but uranyl luminescence is quenched in 7. A solid-state photoluminescence quantum yield of 11.5% has been measured for complex 1, while those for compounds 3-6 and 9 are in the range of 2.0-3.5%.