Study on the coordination of cyclopentanocucurbit[5,6]uril with Fe(3+), Co(2+) and Ni(2+) ions

This paper reports the coordination of cyclopentanocucurbit[5]uril (CyP(5)Q[5]) and cyclopentanocucurbit[6]uril (CyP(6)Q[6]) with Fe(ClO(4))(3), Co(ClO(4))(2) and Ni(ClO(4))(2). Single crystal X-ray diffraction analysis shows the metal ions are directly coordinated with the portal of the cucurbit[n]uril to form a one-dimensional supramolecular chain or independent systems in the CyP(5)Q[5]@Fe(ClO(4))(3), CyP(5)Q[5]@Co(ClO(4))(2), CyP(6)Q[6]@Co(ClO(4))(2) and CyP(5)Q[5]@Ni(ClO(4))(2) complexes. In CyP(6)Q[6]@Fe(ClO(4))(3), the metal ion is not directly coordinated with the cucurbit[n]uril portal, but after forming Fe(H(2)O)(6), it interacts with the cucurbit[n]uril portal via a hydrogen bond. The CyP(6)Q[6]@Ni(ClO(4))(2) complex is quite special; in this system, there are both metal ions directly coordinated with the cucurbit[n]uril portal and free on the outer surface of the cucurbit[n]uril.