Crystal structure of a La(III) complex with macrocyclic cavitand cucurbit[6]uril

Slow evaporation in air of a lanthanum nitrate solution containing macrocyclic cavitand cucurbit[6]uril yields a complex of the composition of [La(H₂O)₆(X@C₃₆H₃₆N₂₄O₁₂)(NO₃)](NO₃)₂· 6.96H₂O (X = 0.5C₅H₅N + 0.5H₂O). The complex is structurally characterized using single crystal X-ray diffraction. Lanthanum atoms are coordinated with oxygen atoms of carbonyl groups of cucurbit[6]uril portals. The compound crystallizes in the orthorhombic crystal system, space group Pnn2, unit cell parameters (150 K): a = 11.997(2) Å, b = 17.093(3) Å, c = 14.133(3) Å, V = 2899.3(10) ų, Z = 2. Lanthanum atoms are disordered, alternative positions being related by the two-fold axis. The complex has an island structure. A pyridine molecule occupies an internal cavity of one half of cucurbit[6]uril molecules, while a water molecule occupies the other.