Imposition of Chirality in a Dinuclear Triple-Stranded Helicate by Ion Pair Formation1

Tunable chiral induction and complete determination of chirality in a dinuclear triple helicate, [Ga213]6- (1 = N,N‘-bis(2,3-dihydroxybenzoyl)-1,4-phenylenediamine, an achiral ligand) is achieved by the use of a chiral counterion. The counterion, (S)-N-methylnicotinium (s-nic), has stereospecific interactions with the helicate. The energy difference, ΔG, between the ΛΛ and ΔΔ helicates in the asymmetric environment afforded by enantiopure s-nic is about 1.1 (±0.2) kcal/mol.