Theoretical Investigation on the Decaying Behavior of Exchange Interaction in Quinoid and Aromatic Molecular Wires

Abstract

The difference in the decaying behavior of the exchange interaction between quinoid and aromatic molecular wires was investigated by means of density functional theory calculations. The biradical quinoid structure was realized when the molecular wire consists of thiophene-S,S-dioxide and allyl nitronyl nitroxide radical. While the calculated decay constant (β) for oligothiophene was 0.23 Å–1, the obtained β value for the quinoid structure of oligothiophene-S,S-dioxide was 0.09 Å–1; this finding suggested that the quinoid molecular wire had a smaller β value than the aromatic wire. It was also found that β decreases upon oxidation of the sulfur atom in the oligothiophene due to an increase in its olefinic nature. The quinoid molecular wire made of thiophene-S,S-dioxide can be thus considered as a suitable system for the charge and spin transport in molecular electronics and spintronics.