Chiral Transmission to Cationic Polycobaltocenes over Multiple Length Scales Using Anionic Surfactants

摘要

Chiral polymers are ubiquitous in nature, and the self-assembly of chiral materials is a field of widespread interest. In this paper, we describe the formation of chiral metallopolymers based on poly(cobaltoceniumethylene) ([PCE]~(n +)), which have been prepared through oxidation of poly(cobaltocenylethylene) (PCE) in the presence of enantiopure N -acyl-amino-acid-derived anionic surfactants, such as N -palmitoyl-l-alanine (C_(16)-l-Ala) and N -palmitoyl-d-alanine (C_(16)-d-Ala). It is postulated that the resulting metallopolymer complexes [PCE][C_(16)-l/d-Ala]_(n ) contain close ionic contacts, and exhibit chirality through the axially chiral ethylenic CH_(2)–CH_(2) bridges, leading to interaction of the chromophoric [CoCp_(2)]~(+) units through chiral space. The steric influence of the long palmitoyl (C_(16)) surfactant tail is key for the transmission of chirality to the polymer, and results in a brushlike amphiphilic macromolecular structure that also affords solubility in polar organic solvents (e.g., EtOH, THF). Upon dialysis of these solutions into water, the hydrophobic palmitoyl surfactant substituents aggregate and the complex assembles into superhelical ribbons with identifiable “handedness”, indicating the transmission of chirality from the molecular surfactant to the micrometer length scale, via the macromolecular complex.