Ultraviolet Photoelectron Spectroscopy of Organic Anions

<p>Ultraviolet photoelectron spectroscopy has been used to study several negative organic ions and their corresponding neutrals: cyclopentadienide, pyrrolide, imidazolide, pyrazolide, vinyl diazomethyl anion, and 2-oxepinoxide. The photoelectron spectra obtained for these systems gives structural, vibrational, and electronic information about the corresponding neutral radicals.\&nbsp;</p> <p>Several of the ions listed above are related: cyclopentadienide, pyrrolide, imidazolide and pyrazolide. Each is a 5-membered ring system, with 0, 1, or 2 nitrogen atoms in the ring. The cyclopentadienyl radical is a well known radical exhibiting Jahn-Teller distortion, and these effects are evident in the photoelectron spectrum of cyclopentadienide. Replacement of one C\textemdashH group in cyclopentadienide by an N atom gives the pyrrolide ion. Jahn-Teller effects are no longer present in the radical counterpart, pyrrolyl; however, electronic interactions between the ground and first excited states are evident in the photoelectron spectrum. Imidazolide and pyrazolide are isomers of one another, and each has two N atoms in the ring. In imidazolide the N atoms are separated, while in pyrazolide they are adjacent. The corresponding radicals (imidazolyl and pyrazolyl) also show interesting electronic interactions between their ground and first excited states. In imidazolyl the interactions are weak, and the effects are not evident in the photoelectron spectrum. In pyrazolyl they are significantly stronger, and unexpected vibrational bands appear in the photoelectron spectrum as a result.\&nbsp;</p>
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University of Colorado Boulder
Boulder, CO
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