Polysilanes diarylpolysilanes

When the substituent groups are large (aryl or branched alkyl) normally no long-wavelength thermochromic shift takes place. This behavior is found for arylalkyl-polysilanes, diarylpolysilanes, and (cyclo-HexSiMe) . 

Since for the diarylpolysilanes, as for all polysilanes, the main chain is chromophoric due to the electronic transition between the delocalized silicon a and a orbitals, the electronic spectroscopies of CD, UV-Vis, and FL are particularly powerful probes of the structures of these materials. The magnitude of dimensionless quantity, gabs, is perhaps the most useful in comparing the CD spectra of optically active poly(diarylsilane)s. 

Recent studies have validated the idea that the superhelix model is responsible for chiroptical switching of polysilane aggregates in a series of diarylpolysilanes, 28-30, in which only the length of the para-substituent in the aryl side chain varies, decreasing monotonically in the order of 28 (ethyl), 29(rc-propyl), 39 (n-butyl) with the intention to effect a chirality switch by reduction of d alone [82]. The proper structural tuning results in a p/d ratio,... 

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