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Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Molecule Isomerism Modulates the Diradical Properties of Stable Singlet Diradicaloids
Joshua E Barker1, Justin J Dressler1, Abel Cárdenas Valdivia2
1Department of Chemistry & Biochemistry and the Materials Science Institute , University of Oregon , Eugene , Oregon 97403-1253 , United States.
Abstract:
Inclusion of quinoidal cores in conjugated hydrocarbons is a common strategy to modulate the properties of diradicaloids formed by aromaticity recovery within the quinoidal unit. Here we describe an alternative approach of tuning of diradical properties in indenoindenodibenzothiophenes upon anti → syn isomerism of the benzothiophene motif. This alters the relationship of the S atom with the radical center from linear to cross conjugation yet retains the same 2,6-naphtho conjugation pattern of the rearomatized core. We conduct a full comparison between the anti and syn derivatives based on structural, spectroscopic, theoretical, and magnetic measurements, showing that these systems are stable open-shell singlet diradicaloids that only access their triplet state at elevated temperatures.
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