Multipodal dynamic coordination involving cation-π interactions to control the structure of helical polymers

A precise tuning of the four possible states of a helix (P/M helical sense and stretched/compressed helical backbone) is attained by controlling the complexation between Li⁺ and a poly(phenylacetylene) that bears amide, ester and phenyl ring functionalities at the pendant group. Depending on the MeOH ratio that is present as a cosolvent, different coordination sites are involved in interactions leading to complexes I-III, each one with a characteristic structure (tri-, bi-, and unipodal) and an associated helical state. This dynamic coordination allows the selective modification of the helical sense or the stretching/compression backbone of a helical polymer.