Solution Photochemistry of Poly(di-n-alkylsilane)s. An EPR-ENDOR Study of the Structure of the Persistent Radicals

The structure of the initial persistent radicals formed by UV irradiation of poly(di-n-alkylsilane)s has been determined by EPR-ENDOR spectroscopy to be -RR′Si-RSi*-RR′Si- A mechanism of formation is proposed. A study of the temperature dependence of the EPR spectra shows that the rotation of the methylene group attached to the radical center is not free and that the average conformation of the alkyl substituent is dependent both on its structure and on temperature. Various isotopically labeled derivatives of poly(di-n-hexylsilane) have been studied and this has allowed the determination of the hyperfine splitting constants of nine inequivalent nuclei around the radical center on the polymer chain. © 1991, American Chemical Society. All rights reserved.