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 P 2 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.