Poly(phenylacetylene) with bulky chiral germyl groups: synthesis and effects of measuring solvents and temperature on chiroptical properties

Abstract

(+)- p-[{Methyl(1-naphthyl)phenyl}germyl]phenylacetylene, an acetylene with a bulky chiral germyl group, was polymerized with [(nbd)RhCl] 2–Et 3N to give a high-molecular-weight polymer in good yield. The CD spectrum of the polymer exhibited very large molar ellipticities [ θ] in the UV region in non-aromatic solvents (e.g. THF and CHCl 3). In contrast, the CD signals of the polymer in aromatic solvents (e.g. toluene, tetralin, and benzene) became appreciably smaller: [ θ] max=6.4×10 4 (330 nm) and −4.7×10 4° cm 2 dmol −1 (370 nm) in CHCl 3; [ θ] max=1.1×10 4 (330 nm) and −0.7×10 4° cm 2 dmol −1 (370 nm) in toluene. The [ θ] max values of the polymer in aromatic solvents increased when the solutions were heated, which is attributed to decreased π–π interaction between the solvents and side groups.