Physical Chemistry Chemical Physics, 17, 23602-23612.
Ionization of a molecule can greatly alter its electronic structure as well as its molecular structure. In this collaborative experimental and theoretical study, we examined variance in hyperconjugation upon ionization of diethyl ether (DEE) and diethyl sulfide (DES). We obtained the experimental vibrational spectra of DEE, DES, DEE+, DEE+-Ar, and DES+-Ar in the wavenumber region of 2000 to 3700 cm-1. For DEE+-Ar we observed a greatly red shifted CH stretching peak at 2700 cm-1, while the lowest CH stretching peaks for the DEE, DES, and DES+-Ar were observed around 2850 cm-1. While we calculated a drastic red shifted CH stretching peak at 2760cm-1 for DEE+, the lowest calculated CH stretching peaks for DEE, DES, and DES+ were at 2860, 2945, and 2908 cm-1. In addition, for DEE the minima (maxima) geometry in the neutral state become a maxima (minima) geometry in the cation state, while similar geometries are seen for neutral and cationic DES. These experimental and theoretical findings were rationalized through the natural bond orbital analysis by quantifying the hyperconjugation between the sCH bond and the ionized single occupied p orbital of the oxygen (sulfur) in DEE+ (DES+).
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