The crystal structure of a mononuclear Pr(III) complex with cucurbit[6]uril.

A new mononuclear complex, penta-aqua-(cucurbit[6]uril-κ(2) O,O')(nitrato-κ(2) O,O')praseodymium(III) dinitrate 9.56-hydrate, [Pr(NO(3))(CB6)(H(2)O)(5)](NO(3))(2)·9.56H(2)O (1), was obtained as outcome of the hydro-thermal reaction between the macrocyclic ligand cucurbit[6]uril (CB6, C(36)H(36)N(24)O(12)) with a tenfold excess of Pr(NO(3))(3)·6H(2)O. Complex 1 crystallizes in the P2(1)/n space group with two crystallographically independent but chemically identical [Pr(CB6)(NO(3))(H(2)O)(5)](2+) complex cations, four nitrate counter-anions and 19.12 inter-stitial water mol-ecules per asymmetric unit. The nona-coordinated Pr(III) in 1 are located in the PrO(9) coordination environment formed by two carbonyl O atoms from bidentate cucurbit[6]uril units, two oxygen atoms from the bidentate nitrate anion and five water mol-ecules. Considering the differences in Pr-O bond distances and O-Pr-O angles in the coordination spheres, the coordination polyhedrons of the two Pr(III) atoms can be described as distorted spherical capped square anti-prismatic and muffin polyhedral.