Resonance Balance Shift in Stacks of Delocalized Singlet Biradicals


  • This work was supported by Yamada Science Foundation (T.K.), Grants-in-Aid for Scientific Research (nos. 19550039 (T.K.), 18350007 (M.N.), and 20340072 (H.O.)) from the Japan Society for the Promotion of Science (JSPS) and from the Ministry of Education, Culture, Sports, Science and Technology-Japan (MEXT) (no. 20110002 (H.O.)), and the Global Center of Excellence program “Global Education and Research Center for Bio-Environmental Chemistry” of Osaka University (A.S.). A.S. acknowledges the Japan Society for the Promotion of Science (JSPS) Fellowship for Young Scientists.


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Two flavors: Intra- and intermolecular spin–spin interactions of unpaired electrons coexist and correlate in stacks of phenalenyl-based singlet biradicals. The electronic structure of the one-dimensional π–π chain is best represented by the superposition of formulas A and B in terms of the resonating valence-bond (RVB) model. Lower temperatures and higher pressures induce a resonance balance shift to the formula B.