Construction of one-dimensional homochiral helical supramolecular stereoismers using chiral macrocyclic nickel(II) complexes as building blocks

• The helicity of one-dimensional chains is much dependent on the chirality of the building blocks.
• The molecular building blocks may change the helicity of helical chain, but not affect the displayed Cotton effects.
• Two different one-dimensional helical chains were obtained from the same reactions.

One one-dimensional right-handed helical chain of {[Ni(RR-L)][Ni(CN)4]·2H2O}n (Δ-2·(2H2O)n) was successfully constructed by the reaction of the [Ni(α-RR-L)]2+ and [Ni(CN)4]2− in acetonitrile/water (1:1) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane), and another two one-dimensional left-handed helical chains of {[Ni(SS-L)][Ni(CN)4]·2H2O}n (Λ-2·(2H2O)n) and {[Ni(SS-L)][Ni(CN)4]·1.25H2O}n (Λ-3·(1.25H2O)n) were obtained from the reaction of [Ni(α-SS-L)]2+ with [Ni(CN)4]2−. The reaction of [Ni(CN)4]2− building blocks with [Ni(α-SS-L)]2+ in acetonitrile/methanol (1:1) gave a one-dimensional left-handed helical chain of {[Ni(SS-L)][Ni(CN)4]·MeCN}n (Λ-2·(MeCN)n). In all supramolecular isomers, the [Ni(RR-L)]2+/[Ni(SS-L)]2+ cations are alternately bridged by [Ni(CN)4]2− anions through cyano-groups to form one-dimensional helical chains. The homochiral natures of four complexes were confirmed by the results of solid-state circular dichroism spectra measurements.

Four supramolecular isomers with one-dimensional helical chains of -2·(2H2O)n, Λ-2·(2H2O)n, Λ-2·(MeCN)n and Λ-3·(1.25H2O)n were obtained by the reactions of the [Ni(α-RR-L)]2+/[Ni(α-SS-L)]2+ and [Ni(CN)4]2−. The homochiral natures of four complexes were confirmed by the results of solid-state circular dichroism spectra measurements.Figure optionsDownload as PowerPoint slide