Effects of Hyperconjugation on the Electronic Structure and Photoreactivity of Organic Sulfonyl Chlorides

Effects of Hyperconjugation on the Electronic Structure and Photoreactivity of Organic Sulfonyl Chlorides. Martin-Diaconescu, V. & Kennepohl, P. Inorg. Chem., 48(3):1038-1044, 2, 2009.

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The electronic structure of organic sulfonyl compounds of the form RSO(2)G (G = -Cl, -OH, -CH(3)) is investigated to evaluate the effect of aryl R groups on photocleavage of the S-G bond. Sulfur K-edge X-ray absorption spectroscopy (XAS) provides a direct measure of the empty low-lying molecular orbitals in these complexes and, in combination with DFT calculations, a detailed description of the bonding in these compounds. The presence of an aryl group bound to the sulfonyl moiety has a significant impact on the spectroscopy and electronic structure of the site. The analysis suggests that the SCl(sigma*) orbital is significantly affected by mixing with the aryl pi* manifold. This mixing is dependent upon the nature of G and is most pronounced in the sulfonyl chlorides, where the energy of the SCl(sigma*) orbital is lowered by approximately 0.5 eV. The observed mixing is best described as excited-state hyperconjugation of the aryl pi system into the SCl(sigma*) orbital. The magnitude of the effect can be estimated directly from the S K-edge XAS spectra. These results are discussed in relation to the observed photochemistry of RSO(2)Cl, which is significantly enhanced when R = aryl as compared to alkyl substituents.

@article{
 title = {Effects of Hyperconjugation on the Electronic Structure and Photoreactivity of Organic Sulfonyl Chlorides},
 type = {article},
 year = {2009},
 keywords = {DFT,SSRL,X-ray Absorption Spectroscopy,photochemistry,sulfur redox},
 pages = {1038-1044},
 volume = {48},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/19132932,http://pubs.acs.org/doi/abs/10.1021/ic801665f},
 month = {2},
 day = {2},
 institution = {The University of British Columbia, Department of Chemistry, Vancouver, British Columbia V6T 1Z1.},
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 abstract = {The electronic structure of organic sulfonyl compounds of the form RSO(2)G (G = -Cl, -OH, -CH(3)) is investigated to evaluate the effect of aryl R groups on photocleavage of the S-G bond. Sulfur K-edge X-ray absorption spectroscopy (XAS) provides a direct measure of the empty low-lying molecular orbitals in these complexes and, in combination with DFT calculations, a detailed description of the bonding in these compounds. The presence of an aryl group bound to the sulfonyl moiety has a significant impact on the spectroscopy and electronic structure of the site. The analysis suggests that the SCl(sigma*) orbital is significantly affected by mixing with the aryl pi* manifold. This mixing is dependent upon the nature of G and is most pronounced in the sulfonyl chlorides, where the energy of the SCl(sigma*) orbital is lowered by approximately 0.5 eV. The observed mixing is best described as excited-state hyperconjugation of the aryl pi system into the SCl(sigma*) orbital. The magnitude of the effect can be estimated directly from the S K-edge XAS spectra. These results are discussed in relation to the observed photochemistry of RSO(2)Cl, which is significantly enhanced when R = aryl as compared to alkyl substituents.},
 bibtype = {article},
 author = {Martin-Diaconescu, Vlad and Kennepohl, Pierre},
 doi = {10.1021/ic801665f},
 journal = {Inorg. Chem.},
 number = {3}
}

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