Zwitterionic dicopper helicates: anion encapsulation and binding studies

Dalton Trans. 2010 Mar 21;39(11):2936-41. doi: 10.1039/b922998a. Epub 2010 Feb 8.

Abstract

The synthesis and spectroscopic studies of a dicopper(II) double helicate capable of binding anions is described. X-Ray crystallographic analysis of three anion variations of the complex have shown that the helicate is capable of accommodating anions with an approximate volume of 0.09 nm(3) and smaller. ESI-MS revealed that the supramolecular complexes retain the 2 : 2 ligand : metal cluster in solution. Spectrometric analysis has shown the complex is capable of binding anions in a 1 : 1 ratio of helicate to anion, in the order SO(4)(2-) > HPO(4)(2-) > ClO(4)(-) approximately BF(4)(-) approximately NO(3)(-). We demonstrate that coordination to the metal centre, H-bonding and electrostatic interactions all play a role in encapsulating the anions.