Coordination complexes based on pentacyclohexanocucurbit[5]uril and lanthanide(III) ions: lanthanide contraction effect induced structural variation

Eight coordination complexes, {LnCl(2)(H2O)(3)Q*[5]}center dot NO3 center dot 18.5H(2)O [isomorphous for Ln = La (1), Ce (2) and Pr (3)], {LnCl(2)(H2O)(2)Q*[5]}center dot NO3 center dot 14H(2)O [isomorphous for Ln = Nd (4) and Sm (5)], {Dy(H2O)(2)[Cl subset of Q*[5]] Dy(H2O)(6)}center dot 5Cl center dot 20H(2)O (6), {LnCl(H2O)[Cl subset of Q*[5]]Ln(H2O)(6)}center dot 4Cl center dot 13H(2)O [isomorphous for Ln = Ho (7) and Er (8)], were obtained by reactions of the corresponding lanthanide species with the macrocyclic ligand pentacyclohexanocucurbit[5] uril (Q*[5]) in aqueous solution, and their structures were determined by single-crystal X-ray diffraction. Crystal structure analysis reveals that, in complexes 1-5, each Q*[5] coordinates to one lanthanide(III) ion to form an opened molecular capsule structure, and then adjacent molecular capsules bridge each other to form a 1-D coordination polymer structure, while in complexes 6-8, each Q*[5] coordinates to two lanthanide(III) ions to form a 0-D half-opened molecular capsule structure. These complexes show that their structural variations are ascribed to the effect of lanthanide contraction.