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Diindeno-fusion of an anthracene as a design strategy for stable organic biradicals


The consequence of unpaired electrons in organic molecules has fascinated and confounded chemists for over a century. The study of open-shell molecules has been rekindled in recent years as new synthetic methods, improved spectroscopic techniques and powerful computational tools have been brought to bear on this field. Nonetheless, it is the intrinsic instability of the biradical species that limits the practicality of this research. Here we report the synthesis and characterization of a molecule based on the diindeno[b,i]anthracene framework that exhibits pronounced open-shell character yet possesses remarkable stability. The synthetic route is rapid, efficient and possible on the gram scale. The molecular structure was confirmed through single-crystal X-ray diffraction. From variable-temperature Raman spectroscopy and magnetic susceptibility measurements a thermally accessible triplet excited state was found. Organic field-effect transistor device data show an ambipolar performance with balanced electron and hole mobilities. Our results demonstrate the rational design and synthesis of an air- and temperature-stable biradical compound.

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Figure 1: PCHs with open-shell character.
Figure 2: Synthesis of DIAn.
Figure 3: Steady-state properties of DIAn and OFET device results.
Figure 4: Solid-state structure of DIAn by XRD.
Figure 5: Temperature-dependent properties of DIAn.
Figure 6: Theoretical assessment of DIAn.


  1. 1

    Tschitschibabin, A. E. Über einige phenylierte Derivate des p,p-Ditolyls. Chem. Ber. 40, 1810–1819 (1907).

    CAS  Article  Google Scholar 

  2. 2

    Montgomery, L. K., Huffman, J. C., Jurczak, E. A. & Grendze, M. P. The molecular structures of Thiele's and Chichibabin's hydrocarbons. J. Am. Chem. Soc. 108, 6004–6011 (1986).

    CAS  Article  Google Scholar 

  3. 3

    Doehnert, D. & Koutecky, J. Occupation numbers of natural orbitals as a criterion for biradical character. Different kinds of biradicals. J. Am. Chem. Soc. 102, 1789–1796 (1980).

    CAS  Article  Google Scholar 

  4. 4

    Yamaguchi, K. et al. Analytical and ab initio studies of effective exchange interactions, polyradical character, unpaired electron density, and information entropy in radical clusters (R)N: allyl radical cluster (N = 2–10) and hydrogen radical cluster (N = 50). Int. J. Quantum Chem. 90, 370–385 (2002).

    CAS  Article  Google Scholar 

  5. 5

    Abe, M. Diradicals. Chem. Rev. 113, 7011–7088 (2013).

    CAS  Article  Google Scholar 

  6. 6

    Karafiloglou, P. The double (or dynamic) spin polarization in π diradicals. J. Chem. Educ. 66, 816–817 (1989).

    CAS  Article  Google Scholar 

  7. 7

    Shimizu, A. et al. Indeno[2,1-b]fluorene: a 20-π-electron hydrocarbon with very low-energy light absorption. Angew. Chem. Int. Ed. 52, 6076–6079 (2013).

    CAS  Article  Google Scholar 

  8. 8

    Kubo, T. et al. Synthesis, intermolecular interaction, and semiconductive behavior of a delocalized singlet biradical hydrocarbon. Angew. Chem. Int. Ed. 44, 6564–6568 (2005).

    CAS  Article  Google Scholar 

  9. 9

    Li, Y. et al. Kinetically blocked stable heptazethrene and octazethrene: closed-shell or open-shell in the ground state? J. Am. Chem. Soc. 134, 14913–14922 (2012).

    CAS  Article  Google Scholar 

  10. 10

    Konishi, A. et al. Synthesis and characterization of teranthene: a singlet biradical polycyclic aromatic hydrocarbon having Kekulé structures. J. Am. Chem. Soc. 132, 11021–11023 (2010).

    CAS  Article  Google Scholar 

  11. 11

    Sun, Z., Ye, Q., Chi, C. & Wu, J. Low band gap polycyclic hydrocarbons: from closed-shell near infrared dyes and semiconductors to open-shell radicals. Chem. Soc. Rev. 41, 7857–7889 (2012).

    CAS  Article  Google Scholar 

  12. 12

    Nakano, M. et al. Second hyperpolarizability (γ) of singlet diradical system: dependence of γ on the diradical character. J. Phys. Chem. A 109, 885–891 (2005).

    CAS  Article  Google Scholar 

  13. 13

    Motomura, S. et al. Size dependences of the diradical character and the second hyperpolarizabilities in dicyclopenta-fused acenes: relationships with their aromaticity/antiaromaticity. Phys. Chem. Chem. Phys. 13, 20575–20583 (2011).

    CAS  Article  Google Scholar 

  14. 14

    Nakano, M. et al. Relationship between third-order nonlinear optical properties and magnetic interactions in open-shell systems: a new paradigm for nonlinear optics. Phys. Rev. Lett. 99, 033001 (2007).

    Article  Google Scholar 

  15. 15

    Nakano, M. & Champagne, B. Theoretical design of open-shell singlet molecular systems for nonlinear optics. J. Phys. Chem. Lett. 6, 3236–3256 (2015).

    CAS  Article  Google Scholar 

  16. 16

    Kamada, K. et al. Strong two-photon absorption of singlet diradical hydrocarbons. Angew. Chem. Int. Ed. 46, 3544–3546 (2007).

    CAS  Article  Google Scholar 

  17. 17

    Zeng, Z. et al. Pro-aromatic and anti-aromatic π-conjugated molecules: an irresistible wish to be diradicals. Chem. Soc. Rev. 44, 6578–6596 (2015).

    CAS  Article  Google Scholar 

  18. 18

    Morita, Y., Suzuki, S., Sato, K. & Takui, T. Synthetic organic spin chemistry for structurally well-defined open-shell graphene fragments. Nature Chem. 3, 197–204 (2011).

    CAS  Article  Google Scholar 

  19. 19

    Ito, S., Minami, T. & Nakano, M. Diradical character based design for singlet fission of condensed-ring systems with 4 electrons. J. Phys. Chem. C 116, 19729–19736 (2012).

    CAS  Article  Google Scholar 

  20. 20

    Smith, M. B. & Michl, J. Recent advances in singlet fission. Annu. Rev. Phys. Chem. 64, 361–386 (2013).

    CAS  Article  Google Scholar 

  21. 21

    Varnavski, O. et al. High yield ultrafast intramolecular singlet exciton fission in a quinoidal bithiophene. J. Phys. Chem. Lett. 6, 1375–1384 (2015).

    CAS  Article  Google Scholar 

  22. 22

    Thorley, K. J. & Anthony, J. E. The electronic nature and reactivity of the larger acenes. Isr. J. Chem. 13, 642–649 (2014).

    Article  Google Scholar 

  23. 23

    Anthony, J. E., Brooks, J. S., Eaton, D. L. & Parkin, S. R. Functionalized pentacene: improved electronic properties from control of solid-state order. J. Am. Chem. Soc. 123, 9482–9483 (2001).

    CAS  Article  Google Scholar 

  24. 24

    Fudickar, W. & Linker, T. Why triple bonds protect acenes from oxidation and decomposition. J. Am. Chem. Soc. 134, 15071–15082 (2012).

    CAS  Article  Google Scholar 

  25. 25

    Park, J.-H. et al. Soluble and easily crystallized anthracene derivatives: precursors of solution-processable semiconducting molecules. Org. Lett. 9, 2573–2576 (2007).

    CAS  Article  Google Scholar 

  26. 26

    Chase, D. T. et al. 6,12-Diarylindeno[1,2-b]fluorenes: syntheses, photophysics, and ambipolar OFETs. J. Am. Chem. Soc. 134, 10349–10352 (2012).

    CAS  Article  Google Scholar 

  27. 27

    Wood, J. D., Jellison, J. L., Finke, A. D., Wang, L. & Plunkett, K. N. Electron acceptors based on functionalizable cyclopenta[hi]aceanthrylenes and dicyclopenta[de,mn]tetracenes. J. Am. Chem. Soc. 134, 15783–15789 (2012).

    CAS  Article  Google Scholar 

  28. 28

    Chikamatsu, M. et al. Ambipolar organic field-effect transistors based on a low band gap semiconductor with balance hole and electron mobilities. Appl. Phys. Lett. 91, 043506 (2007).

    Article  Google Scholar 

  29. 29

    Koike, H. et al. Stable delocalized singlet biradical hydrocarbon for organic field-effect transistors. Adv. Funct. Mater. 26, 277–283 (2016).

    CAS  Article  Google Scholar 

  30. 30

    Marshall, J. L. & Haley, M. M. in Organic Redox Systems: Synthesis, Properties and Applications 1st edn (ed. Nishinaga, T.) 311–358 (Wiley, 2016).

    Google Scholar 

  31. 31

    Turro, N. J., Ramamurthy, V. & Scaiano, J. C. in Principles of Molecular Photochemistry: An Introduction 1st edn (University Science Books, 2009).

    Google Scholar 

  32. 32

    Bleaney, B. & Bowers, K. D. Anomalous paramagnetism of copper acetate. Proc. R. Soc. Lond. A 214, 451–465 (1952).

    CAS  Article  Google Scholar 

  33. 33

    Bernard, Y. A., Shao, Y. & Krylov, A. I. General formulation of spin-flip time-dependent density functional theory using non-collinear kernels: theory, implementation, and benchmarks. J. Chem. Phys. 136, 204103 (2012).

    Article  Google Scholar 

  34. 34

    Casado, J. et al. Raman detection of ‘ambiguous’ conjugated biradicals: rapid thermal singlet-to-triplet intersystem crossing in an extended viologen. Angew. Chem. Int. Ed. 47, 1443–1446 (2008).

    CAS  Article  Google Scholar 

  35. 35

    Casado, J., Ponce Ortiz, R. & López Navarrete, J. T. Quinoidal oligothiophenes: new properties behind an unconventional electronic structure. Chem. Soc. Rev. 41, 5672–5686 (2012).

    CAS  Article  Google Scholar 

  36. 36

    Casado, J. et al. Vibrational fingerprint of the structural tuning in push–pull organic chromophores with quinoid or proaromatic spacers. J. Chem. Phys. 126, 074701 (2007).

    Article  Google Scholar 

  37. 37

    Albrecht, A. C. On the theory of Raman intensities. J. Chem. Phys. 34, 1476–1484 (1961).

    CAS  Article  Google Scholar 

  38. 38

    Burdett, J. J. & Bardeen, C. J. Quantum beats in crystalline tetracene delayed fluorescence due to triplet pair coherences produced by direct singlet fission. J. Am. Chem. Soc. 134, 8597–8607 (2012).

    CAS  Article  Google Scholar 

  39. 39

    Frisch, M. J. et al. Gaussian 09, Revision D.01 (Gaussian, Inc., 2009).

    Google Scholar 

  40. 40

    Stephens, P. J., Devlin, F. J., Chabalowski, C. F. & Frisch, M. J. Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields. J. Phys. Chem. 98, 11623–11627 (1994).

    CAS  Article  Google Scholar 

  41. 41

    Krishnan, R., Binkley, J. S., Seeger, R. & Pople, J. A. Self-consistent molecular orbital methods. XX. A basis set for correlated wave functions. J. Chem. Phys. 72, 650–654 (1980).

    CAS  Article  Google Scholar 

  42. 42

    Yamaguchi, K. in Self-Consistent Field: Theory and Applications 1st edn (eds Carbó, R. & Klobukowski, M.) 727–828 (Elsevier, 1990).

    Google Scholar 

  43. 43

    Herges, R. & Geuenich, D. Delocalization of electrons in molecules. J. Phys. Chem. A 105, 3214–3220 (2001).

    CAS  Article  Google Scholar 

  44. 44

    Keith, T. A. & Bader, R. F. W. Calculation of magnetic response properties using a continuous set of gauge transformations. Chem. Phys. Lett. 210, 223–231 (1993).

    CAS  Article  Google Scholar 

  45. 45

    Becke, A. D. Density-functional exchange-energy approximation with correct asymptotic behavior. Phys. Rev. A 38, 3098–3100 (1988).

    CAS  Article  Google Scholar 

  46. 46

    Lee, C., Yang, W. & Parr, R. G. Development of the Colle–Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B 37, 785–789 (1988).

    CAS  Article  Google Scholar 

  47. 47

    Iikura, H., Tsuneda, T., Yanai, T. & Hirao, K. A long-range correction scheme for generalized-gradient-approximation exchange functionals. J. Chem. Phys. 115, 3540–3544 (2001).

    CAS  Article  Google Scholar 

  48. 48

    Gershoni-Poranna, R. & Stanger, A. The NICS-XY-scan: identification of local and global ring currents in multi-ring systems. Chem. Eur. J. 20, 5673–5688 (2014).

    Article  Google Scholar 

  49. 49

    Wolinski, K., Hinton, J. F. & Pulay, P. Efficient implementation of the gauge-independent atomic orbital method for NMR chemical shift calculations. J. Am. Chem. Soc. 112, 8251–8260 (1990).

    CAS  Article  Google Scholar 

  50. 50

    Stanger, A. Obtaining relative induced ring currents quantitatively from NICS. J. Org. Chem. 75, 2281–2288 (2010).

    CAS  Article  Google Scholar 

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This work was supported by the US National Science Foundation (CHE-1301485), by the Spanish Government, MINECO (CTQ2012-33733 and CTQ2011-26507), by Junta de Andalucía (P09-FQM-4708) and Generalitat Valenciana (PrometeoII/2014/076), by a Japan Society for the Promotion of Science (JSPS) Research Fellowship for Young Scientists (No. 15J04949), Grant-in-Aid for Scientific Research (A) (No. 25248007) from the JSPS, a Grant-in-Aid for Scientific Research on Innovative Areas ‘Stimuli-Responsive Chemical Species’ (No. A24109002a), ‘π-System Figuration’ (15H00999), ‘Photosynergetics’ (A26107004a), the Strategic Programs for Innovative Research, Ministry of Education, Culture, Sports, Science & Technology, Japan, the Computational Materials Science Initiative, Japan, the Swedish Research Council (project grant 621-2011-4177) and the Swedish National Infrastructure for Computation (NSC, Linköping). K.J. and H.O. thank R. Herges for providing the AICD 2.0.0 program. The authors acknowledge the Biomolecular Mass Spectrometry Core of the Environmental Health Sciences Core Center at Oregon State University (NIH P30ES000210). We thank T. Kubo (Osaka) for insightful discussions.

Author information




G.E.R. conceived the project, and designed and carried out the experiments, analysed the data and wrote the manuscript. M.M.H. played a critical role in the discussion of the experimental design, project direction, experiments and results, and in the preparation of the manuscript. J.L.M. acquired and analysed the CV data. I.A.M., G.L.E. and R.P.O. obtained the OFET data. L.N.Z. acquired and analysed the X-ray crystallographic data. J.L.Z. performed the Raman spectroscopic measurements. C.G.G. performed the SQUID experiments. J.C. interpreted the magnetic and spectroscopic data and co-wrote the paper. K.F. and M.N. performed the calculation and discussed the geometry optimization, the open-shell character and the S–T gaps. K.J. performed the ACID and NICS-XY density functional theory calculations, and, together with H.O., analysed the data from these computations. All the authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Masayoshi Nakano or Henrik Ottosson or Juan Casado or Michael M. Haley.

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The authors declare no competing financial interests.

Supplementary information

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Supplementary information

Crystallographic data for compound DIAn. (CIF 1014 kb)

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Rudebusch, G., Zafra, J., Jorner, K. et al. Diindeno-fusion of an anthracene as a design strategy for stable organic biradicals. Nature Chem 8, 753–759 (2016).

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