Optically active polymer charge‐transfer complex as a form of charge‐transfer chiralions

Abstract

AbstractPoly(bis‐3,4‐ethylenedioxythiophene) was synthesized by electrochemical polymerization in cholesteric liquid crystal (Ch*LC) in the presence of 7,7,8,8‐tetracyanoquinodimethane (TCNQ). TCNQ acted as a supporting salt and a molecular dopant against the resultant poly(bisEDOT) to form a donor–acceptor‐type polymer charge‐transfer (CT) complex. Because a three‐dimensional (3D) one‐handed chiral structure was imprinted from the matrix chiral liquid crystal, the resulting polymer with TCNQ molecular doping displayed optical activity in the circular dichroism absorptions. This result indicates the production of optically active CT species comprising the polymer and the low‐molecular‐weight acceptor. The intermolecular chiral CT complex formed a one‐handed helical structure. This method is referred to as “CT complex liquid crystal (LC) electrochemical polymerization” to produce the helical polymer CT complex as atropisomers. Further, the optically active CT of the polymer is referred to as “CT chiralions.” The CT formation resulted from the molecular doping of TCNQ in the chiral polymer prepared in the helical LC matrix. As a result, molecular doping and molecular‐imprinting polymerization in the LC produced CT chiralions. The two‐step electrochemical polymerization in one‐pot polymerization developed in this study allowed the results to form a double‐layer fingerprint with a moiré‐like pattern.