Imposition of chirality in a dinuclear triple-stranded helicate by ion pair formation

Tunable chiral induction and complete determination of chirality in a dinuc lear triple helicate, [Ga(2)1(3)](6-) (1 = N,N ' -bis(2,3-dihydroxybenzoyl) -1,4-phenylenediamine, an achiral ligand) is achieved by the use of a chira l counterion. The counterion, (S)-N-methylnicotinium (s-nic), has stereospe cific interactions with the helicate. The energy difference, DeltaG, betwee n the Lambda Lambda and Delta Delta helicates in the asymmetric environment afforded by enantiopure s-nic is about 1.1 (+/-0.2) kcal/mol.