Circularly Polarized Luminescence and Circular Dichroism from Si−Si-Bonded Network Polymers

Abstract

We demonstrated the first circularly polarized luminescence (CPL) and circular dichroism (CD) spectra of three new Si−Si-bonded network polymers bearing the chiral alkyl side groups poly[(S)-2-methylbutylsilyne] (1S), poly[(R)-3,7-dimethyloctylsilyne] (2R), poly[(S)-3,7-dimethyloctylsilyne] (2S), and, for comparison, poly(n-pentylsilyne), which bears an achiral alkyl side group (3). These polymers were successfully prepared by Na-mediated condensation of the corresponding alkyltrichlorosilanes with the help of crown ether. It was revealed that only 1S, which bears a β-branched chiral group, clearly showed an intense CPL signal at ∼570 nm with a quantum yield of ∼1%, along with its corresponding Cotton CD signals in tetrahydrofuran at room temperature. In contrast, 2R and 2S, which possess γ-branched chiral groups, did not show any CPL signal, though they did show the CD bands. As expected, 3 did not show CPL or CD signals. The β-branched chiral side chain was needed to provide the intense CPL band in the ...