Frank, N. L.; Clérac, R.; Green, M. T.; Daro, N.; Sutter, J.-P.; Kahn*, O.; Coulon*, C.; Golhen, S. and Ouahab*, L. Synthesis, Crystal Structure, Magnetic, and Electron Paramagnetic Resonance Properties of a Spiroconjugated Biradical. Evidence for a Spiroconjugation Exchange Pathway J. Am. Chem. Soc. 2000 122, 2053-2061. (MAR 8 2000) DOI: 10.1021/ja993071a.
A spiroconjugated nitronyl nitroxide biradical, 6,6'-(4,4,5,5-tetramethylimidazolidine-3-oxide-1-oxyl)-3,3,3',3'-tetramethyl- 1,1'-spirobisindane (1) was synthesized and the strength and mechanism of magnetic exchange via spiroconjugation pathway was explored. Structural analysis carried out by single crystal X-ray diffraction studies in combination with magnetization measurements, EPR spectroscopy and computational modeling reveals weak antiferromagnetic exchange and conformational exchange in solution leading to atropisomerism.