Uranyl Ion Complexes with Long-Chain Aliphatic α,ω-Dicarboxylates and 3d-Block Metal Counterions

Twelve
new complexes were obtained from reaction of uranyl ions with the
aliphatic dicarboxylic acids HOOC–(CH2)n−2–COOH (H2Cn; n = 7–10 and 12) under solvo-hydrothermal
conditions, in the presence of 3d-block metal ions (Mn2+, Fe3+, Co2+, Ni2+, and Cu2+) and 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen).
In contrast to previously reported triple-stranded helicates obtained
with C92– and C122–, all these
complexes crystallize as polymeric one-dimensional (1D) or two-dimensional
(2D) species. [Fe­(bipy)3]­[(UO2)2(C7)3]·3H2O (1), [Cu­(phen)2]2­[(UO2)3(C7)4(H2O)2]·2H2O (2), and [Cu­(bipy)2]2[(UO2)2(C9)3] (6), in which the 3d cation was reduced
in situ, are 1D ladderlike polymers displaying tetra- or hexanuclear
rings, of sufficient width to encompass two counterions in 2 and 6. The three complexes [Co­(phen)3]­[(UO2)3­(C8)3(O)]·H2O (3), [Ni­(phen)3]­[(UO2)3­(C8)3(O)]·H2O (4) and [Co­(phen)3]­[(UO2)3­(C9)3(O)]·H2O (5) contain bis­(μ3-oxo)-bridged tetranuclear secondary building units, and they
crystallize as deeply furrowed 2D assemblies. Depending on the nature
of the counterion, C102– gives [Ni­(bipy)3]­[(UO2)2­(C10)3]·2H2O (7), a 2D network displaying elongated decanuclear
rings containing the counterions, or [Mn­(phen)3]­[(UO2)2(C10)3]·6H2O (8), [Co­(phen)3]­[(UO2)2(C10)3]·7H2O (9), and [Ni­(phen)3]­[(UO2)2(C10)3]·7H2O (10), which consist of 2D assemblies with honeycomb
topology; the hexanuclear rings in 8–10 are chairlike and occupied by one counterion and two uranyl groups
from neighboring layers. Two complexes of the ligand with the longest
chain, C122–, are reported. [UO2(C12)­(bipy)]
(11) is a neutral 1D species in which bipy chelates the
uranyl ion and plays an important role in the packing through π-stacking
interactions. Two polymeric units, 1D and 2D, coexist in the complex
[Ni­(bipy)3]­[(UO2)2­(C12)3]­[UO2(C12)­(H2O)2]·H2O (12); the 2D network has the honeycomb
topology, but the hexanuclear rings are markedly convoluted, with
local features akin to those in helicates, and the counterions are
embedded in intralayer cavities. Emission spectra measured in the
solid state show in most cases various degrees of quenching, with
intense and well-resolved uranyl emission being observed only for
complexes 2 and 11.