Lanthanide Ion Complexes with 2-, 3-, or 4-Sulfobenzoate and Cucurbit[6]uril

The reaction of lanthanide nitrate, trifluoromethanesulfonate, or chloride salts with the three positional isomers of sulfobenzoic acid (SBH2) in the presence of cucurbit[6]uril (CB6) under hydrotherrnal conditions yielded 13 complexes which were crystallographically characterized. The ortho isomer gave a series of one-dimensional polymeric complexes of columnar shape, {[Ln(2-SB)(NO3)(H2O)(2)](2)CB6}center dot xH(2)O [isomorphous for Ln = La (1) and Ce (2), x = 10 or 11], {[Nd(2-SB)(H2O)(3)][Nd(2-SB)(H2O)(4)]CB6}center dot 2NO(3)center dot 7 center dot 5H(2)O (3), and {[Ln(2-SB)(H2O)(4)](2)CB6}center dot 2NO(3)center dot xH(2)O [isomorphous for Ln = Eu (4), Dy (5), Er (6), and Yb (7), x = 5 or 6]. These compounds all comprise carboxylate-bridged dinuclear units connecting the CB6 molecules through lanthanide-carbonyl coordination, and they differ by sulfonate bonding and formation of a chelate ring being only present in 1-3. In contrast, [Lu(2-SB)center dot(H2O)(7)](2)center dot CB6 center dot 2NO(3)center dot 7H(2)O (8) does not display sulfonate and carbonyl coordination, the carboxylate group being monodentate and the complex species being held as a lid over the CB6 portal by hydrogen bonding. The complexes obtained from erbium trifluoromethanesulfonate and chloride salts, {[Er(2-SB)(H2O)(4)](2)CB6}center dot 2CF(3)SO(3)center dot 2 center dot 5H(2)O (9) and [Er(2-SB)(H2O)(7)](2)center dot CB6 center dot 2Cl.6H(2)O (10), present the same features as 4-7 and 8, respectively. The meta isomer is in the form of the carboxybenzosulfonate 3-SBH-, with the carboxylic acid retaining its proton, in the isomorphous complexes {[Ln(3-SBH)(H2O)(4)](2)CB6]center dot 4NO(3) [Ln = Ce (11) or Nd (12)]. These complexes display the feature, unusual in this series, of coordination by the monodentate sulfonate group only. A columnar assembly is formed by coordination of each metal ion to two CB6 molecules, the 3-SBH- ligand having no role in the polymer formation. Finally, the para isomer is only coordinated by the chelating carboxylate group in [Nd-1.5(4-SB)(CB6)(NO3)(H2O)(6.5)]center dot 4-SBH center dot 4-SBH1.5 center dot 15H(2)O(13).