Constructions of 1D helical chains with left-handed/right-handed helicity: a correlation between the helicity of 1D chains and the chirality of building blocks

Abstract

The reactions of [Ni(alpha-SS-L)](ClO(4))(2)/[Ni(alpha-RR-L)](ClO(4))(2) with dca(-) gave two enantiomers of [Ni(SS-L)](dca)(2) (S-) and [Ni(RR-L)](dca)(2) (R-) in acetonitrile/water, and two supramolecular stereoisomers of {[Ni(SS-L)](2)(dca)(3)(ClO(4)).DMF}(n) (Delta-) and {[Ni(RR-L)](2)(dca)(3)(ClO(4)).DMF}(n) (Lambda-) in acetonitrile/DMF, respectively (L = 5,5,7,12,12, 14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, dca = dicyanamide, N(CN)(2)(-)). While the reaction of racemic [Ni(alpha-rac-L)](ClO(4))(2) (containing an equal amount of SS and RR enantiomers) with dca(-) in acetonitrile/water or acetonitrile/DMF produced a trimer of [Ni(rac-L)(dca)](3).(dca).(ClO(4))(2).MeCN () rather than S-/R- or Delta-/Lambda-. X-ray single-crystal analysis reveals that S-/R- and Delta-/Lambda- crystallize in a chiral space group P2(1), while crystallizes in a centrosymmetric space group C2/c. In S-/R-, the [Ni(SS-L)](dca)(2)/[Ni(RR-L)](dca)(2) monomers are linked through intermolecular hydrogen bonds to form a two-dimensional sheet. While the intermolecular hydrogen bonding linking of {[Ni(SS-L)](2)(dca)(3)}(+)/{[Ni(RR-L)](2)(dca)(3)}(+) leads to the formation of a 1D right-handed helical chain of Delta- and 1D left-handed helical chain of Lambda-, respectively, demonstrating there is a correlation between the helicity of 1D chains and the chirality of building blocks. Complex forms a triangular structure of {[Ni(rac-L)(dca)](3)}(3+), in which the macrocyclic ligand L adopts unsymmetrical RR/RR/SS or RR/SS/SS configurations. The homochiral nature of S-/R- and Delta-/Lambda- are confirmed by the results of solid circular dichroism (CD) spectra measurements. The magnetic properties of chiral Delta-/Lambda- and achiral were investigated.