A general route to chiral nanostructures from helical polymers: P/M switch via dynamic metal coordination

A general method for the conversion of a polyphenylacetylene into its P or M helically oriented polymer, and into its corresponding P/M helical nanoparticles via dynamic metal coordination is presented. Addition of Mn+ ions (e.g., Ca2+, Zn2+, Ag+, among others) to poly(phenylacetylene)s (poly-2 to poly-6), bearing OMe protected amino acids, produces complex I (chelation of the two carbonyl groups; sp conformation) associated with a helix inversion of the polymer. Ulterior addition of a small amount of MeOH transforms complex I into complex II (metal ion coordinated only to the ester group; ap conformation), where a second helix inversion is produced. This dynamic coordination process between complex I and complex II works also at the nanoscale level, and therefore chiral nanoparticles with either P or M helices can be generated or transformed into each other by controlling the polymer/metal/methanol ratio in the helical polymer metal complex (HPMC).