The Influence of Different Spacer Lengths on the Selectivity of Self‐Assembly Processes of Bis(bipyridine)‐BINOL Helicates

The synthesis and self‐assembly behaviour of a series of enantiomerically pure bis(chelating) ligands is reported. The ligands differ in the spacer unit between a BINOL core and two bipyridyl groups as the chelating entities and were found to undergo completely diastereoselective self‐assembly to dinuclear double‐stranded helicates with silver(I) salts, as demonstrated by NMR and CD spectroscopy and ESI mass spectrometry. Upon coordination to iron(II) or zinc(II) ions, however, a dramatic loss in the diastereoselectivity of the self‐assembly of dinuclear triple‐stranded helicates was observed as a result of increasing spacer length. In the case of zinc(II), the self‐assembly processes were even found to be nonselective with regard to the composition of the helicates.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)