Origin of Both Right- and Left-Handed Helicities in a Supramolecular Gel with and without Ni²⁺ at the Supramolecular Level

Abstract

We demonstrate the different origins of helical directions in polymeric gels derived from a hydrazone reaction in the absence and presence of Ni. The right-handed helicity of polymeric gels without Ni originates from the enantiomeric d-form alanine moiety embedded in the building block. However, the right-handed helicity is inverted to a left-handed helicity upon the addition of Ni, indicating that added Ni greatly affects the conformation of the polymeric gel by overcoming the influence of the enantiomer embedded in the building block on the helicity at the supramolecular level. More interestingly, the ratio of the right-toleft-handed helical fibers varies with the concentration of Ni, which converts from 100% right-handed helical fiber to 90% left-handed helical fiber. In the presence of Ni, both right- and left-handed helical fibers coexist at the supramolecular level. Some fibers also exhibit both right- and left-handed helicities in a single fiber.

Entropically Favoured Assembly of Pyrazine‐Based Helical Fibers into Superstructures: Achiral/ Chiral Guest‐Induced Chirality Transformation

“…We believe that due to the strong interactions between the helical fibers and the Ni 2+ ions, intermolecular hydrogen bonding between the helical fibers and solvent molecules (water) as well as analyte (Ni 2+ ions) and solvent molecules is collapsed, and as a result, “ordered” water molecules are released, which further drives the assembly of the helical fibers to generate entropically favorable superstructures, that is, a supercoiled 1 :Ni 2+ ensemble (Figure ). Previously, a metal‐ion‐induced chirality transformation in hydrogels was reported, and this study is the first one where Ni 2+ ions induce a chirality transformation and a transition of helical fibers to entropically driven superstructures in aqueous media is observed. We believe that the high coordination ability of Ni 2+ ions supported by the hydrophobic effect further drives the aggregation of the helical architectures into supercoiled structures.…”

Self-assembled stereomutation with supramolecular chirality inversion

“…Ni( ii ) induced helicity inversion in the polymeric gels was also observed. 83 In addition, the chiral self-sorting was observed by changing the Ag( i ) content in the complex, accompanied by the helicity inversion of aggregates. 84 There are three kinds of pathways for the chiral self-sorting process, which are precisely modulated by the stoichiometric ratio of Ag( i ) to ligands.…”

Bipyridine-containing π-conjugated polymers bearing optically active amide groups: mechanistic aspects of formation of chiral higher-order structures

“…1–7 Organometallic compounds with chiral 2,2′-bipyridine derivatives catalyze asymmetric reactions, 8,9 and compounds bearing chiral 2,2′-bipyridine moieties coordinate to metals to give chiral supramolecular assemblies. 10,11 2,2′-Bipyridine derivatives are also widely employed as building blocks in polymer chemistry. π-Conjugated polymers containing 2,2′-bipyridine moieties are commonly synthesized by the Heck, Sonogashira–Hagihara, Suzuki–Miyaura, Stille coupling polymerizations, and Wittig–Horner type polymerization.…”