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.