Switching handedness in optically active polysilanes

Chain-like optically active polysilanes comprise a helical main chain of SiSi single bonds and chiral and/or achiral side groups. They exhibit unique absorption, circular dichroism, and fluorescence spectra around 300–400 nm due to the σ-conjugation. Since the first brief report of optically active polysilane synthesis in 1992, this research field has now widened to include various homo- and copolymers of optically active poly(dialkylsilane)s, poly(dialkoxysilane)s, poly[alkyl(aryl)silane]s, and poly(diarylsilane)s. This account focuses on screw-sense switchable, optically active poly(dialkylsilane)s among the above optically active polysilanes, including (i) (chir)optical properties, (ii) quantitative population analysis of right- and left-handed helices based on Kuhnʹs dissymmetry ratio, (iii) capability of screw-sense inversion, and (iv) chiroptical switch and memory, as consequences of side group internal interactions, double-well potential energy, and external stimuli. Such knowledge and understanding might stimulate a further polysilane research, and also may advance these polymers to the realization of Si-based nanomaterials and Si-based nanodevices in the future.