Anion-directed assembly helicates

Keegan, J. Kruger, P.E. Nieuwenhuyzen, M. O Brien, J. Martin, N. Anion directed assembly of a dinuclear double helicate. Chem. Commun. 2001, 2192 -2193. 

De Mendoza reported the first example of anion-directed helix formation in 1996 [91]. The assembly of this helical structure relies, not only on electrostatic interactions between the anionic template and the positively charged strands, but also on hydrogen bonding. The tetraguanidinium strand 69 (see Scheme 34) self-assembles around a sulfate anion via hydrogen bonding to produce a double helical structure. The formation of this assembly and its anion-dependence was proposed on the basis of NMR and CD spectroscopic studies. 

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