Uranyl Ion Complexes with all- cis -1,3,5-Cyclohexanetricarboxylate: Unexpected Framework and Nanotubular Assemblies

all-cis-1,3,5-Cyclohexanetricarboxylic acid (LH3) was reacted with uranyl nitrate under solvo-hydrothermal conditions, either alone or in the presence of additional metal cations (Na+, K+, Ni2+, Cu2+, or Tb3+), resulting in the crystallization of a series of eight complexes which were characterized by their crystal structures and luminescence properties. The six complexes [UO2(H2O)(5)][UO2(L)](2)center dot 2H(2)O center dot 3THF (1), [Ni(bipy)(2)(H2O)(2)]-[UO2(L)](2)center dot 4H(2)O (2), [Ni(bipy)(3)][Ni(bipy)(2)(H2O)(2)][UO2(L)](4)center dot 5H(2)O (3), [Ni(H2O)(6)][UO2(L)](2)center dot 2H(2)O (4), [Cu(H2O)(6)]-[UO2(L)](2)center dot 2H(2)O (5), and [Tb(H2O)(8)][UO2(L)](3)center dot 8H(2)O (6) all contain the same {UO2(L)(-)}(infinity) anionic motif, in which the uranyl ion is tris-chelated by three L3- anions to give a two-dimensional assembly with hexagonal {63} topology. The reaction of uranyl nitrate alone with LH3 in water/N-methyl-2-pyrrolidone (NMP) yields the complex [(UO2)(3)(L)(2)(NMP)(2)] (7), which crystallizes as a three-dimensional framework. Finally, in the presence of Na+, K+, or even Kemp's triacid (cis,cis-1,3,5-trimethylcydohexane-1,3,5-tricarboxylic acid), the complex [UO2(LH)] (8) is generated, the structure of which displays a well-resolved nanotubular species possibly associated with extremely disordered molecules or counterions of uncertain nature. These nanotubules have {6(3)} topology and can be seen as resulting from the folding of the two-dimensional assembly present in the former complexes. Emission spectra measured in the solid state show the usual vibronic fine structure, with various degrees of resolution and quenching.