Sequential Induction of Chirality in Helical Polymers: From the Stereocenter to the Achiral Solvent

Abstract

This is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of the Physical Chemistry Letters, Copyright © 2018 American Chemical Society after peer review and technical edityng by the publisher. To access the final edited and published work see: https://pubs.acs.org/doi/10.1021/acs.jpclett.8b00519Several steps of chiral induction have been detected in poly(phenylacetylene)s among their different hierarchical levels of chirality by vibrational circular dichroism, namely, (i) from the stereogenic centers to the innermost polyacetylene helical covalent backbone (helixint), (ii) from this to the external helix (helixext) formed by the side phenyl pendants that form a complementary helix or counter-helix, and (iii) from this pendant helix to the helical solvation sphere (helixsolv.), the last one being observed along this work. The pendant to polyene backbone chiral induction determines the helical structure adopted by the polymer and therefore the solvation helix. This helical structure is promoted by two mechanisms: steric effects and hydrogen bonding. An important finding concerns the demonstration by VCD of how an achiral solvent becomes chirally organized owing to the template effect of the covalent polymer helices, an effect that is silent to other structural techniques such as ECD or AFM and that hence significantly broadens the scope of these previous analysesFinancial support from Ministerio de Ciencia e Innovación [CTQ2014-61470-EXP, CTQ2015- 69391-P, FPI (R. Rodríguez), FPU (S. Medina), Juan de la Cierva postdoctoral Fellowship FJCI- 2015-23531 (B.Nieto-Ortega)], Xunta de Galicia (GRC2014/040, Centro singular de investigación de Galicia accreditation 2016-2019, ED431G/09) and the European Regional Development Fund (ERDF) is gratefully acknowledgedS