Models for Polysilane High Polymers. 1. Singlets Photophysics of LinearPermethylhexadecasilane (Si16 Me34)

摘要

An investigation of the UV absorption and emission properties of n-Si16Me34 inroom and low temperature solutions revealed a striking similarity to the photophysical behavior of high molecular weight peralkylated polysilanes. The absorption is that expected for a statistical collection of chromophoric segments. Room-temperature emission is that expected from the lowest excitation energy conformations of approximately 16-silicon chains, presumable all-trans. Their excited states are believed to be generated by energy transfer in the polymer and by adiabatic conformational transformations in the hexadecasilane. The latter process is suppressed in 3-methylpentane glass, where many spectrally distinct conformers are observed to behave independently. Three of them dominate and have been characterized spectrally. At concentrations of 5 x 10-6M and higher, 3-methylpentane solutions of Sil6Me34 formed dimeric or oligomeric species upon fast cooling and precipitated a microcrystalline solid upon slow cooling. These, too, have been spectrally characterized,