Coordination of lanthanide cations to cucurbituril and supramolecular self-assembly in the absence and presence of polychloridometallate ions

Abstract

Compared to isolated, simple Ln³⁺/Q[6] complexes in the absence of polychloridometallate ions, linear coordination polymers have been assembled from lanthanide cations (Ln³⁺) and cucurbituril (Q[6]) in the presence of polychloridometallate ions as inorganic structure inducers in HCl solution. X-ray diffraction analysis has revealed that not only [CuCl₄]²⁻ anions but also [FeCl₂(H₂O)₄]⁺ cations can induce the coordination of Ln³⁺ cations to Q[6] so as to form Ln³⁺/Q[6]-based tubular coordination polymers. The driving forces are considered to be interaction of the electron-deficient carbon sites of the carbonyl dipoles of Q[n] molecules with the chloride ends of the M_d-block−Cl bonds in the [M_d-blockCl_x]ⁿ⁻ anions or [M_d-blockCl_x]^m+ cations, as well as unusual hydrogen bonding between the methine and methylene groups on the back of adjacent Q[n] molecules and the chlorine atoms of the [M_d-blockCl_x]ⁿ⁻ ions. We have classified such interactions as ‘back-interaction of Q[n]s’.

Keywords:

• Lanthanide cations
• cucurbituril
• coordination
• polychloridometallate ions
• structure inducers

Acknowledgements

We acknowledge the support of National Natural Science Foundation of China [grant number 21272045], the Natural Science Foundation of the Department of Education of Guizhou Province.

Disclosure statement

No potential conflict of interest was reported by the authors.