Supramolecular asymmetric induction in dinuclear triple-stranded helicates.

Supramolecular chiral induction has been observed in five dinuclear triple-stranded helicates composed entirely of achiral components. Three different chiral cations were found to be very effective at inducing high levels of enantiomeric enrichment in racemic mixtures of the helicates. The mechanism of intermolecular chiral induction in one cation-helicate pair, s-nic/K6[Ga2L(1)3], has been elucidated through circular dichroism spectroscopy, X-ray crystallography, and one and two-dimensional NMR spectroscopy (s-nic = N-methyl-s-nicotinium, H4L(1) = 1,4-bis(2',3'-dihydroxybenzamido)phenylene).