Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

3D global aromaticity in a fully conjugated diradicaloid cage at different oxidation states

Abstract

Aromaticity is a vital concept that governs the electronic properties of π-conjugated organic molecules and has long been restricted to 2D systems. The aromaticity in 3D π-conjugated molecules has been rarely studied. Here we report a fully conjugated diradicaloid molecular cage and its global aromaticity at different oxidation states. The neutral compound has an open-shell singlet ground state with a dominant 38π monocyclic conjugation pathway and follows the [4n + 2] Hückel aromaticity rule; the dication has a triplet ground state with a dominant 36π monocyclic conjugation pathway and satisfies [4n] Baird aromaticity; the tetracation is an open-shell singlet with 52 π-electrons that are delocalized along the 3D rigid framework, showing 3D global antiaromaticity; and the hexacation possesses D3 symmetry with 50 globally delocalized π-electrons, showing [6n + 2] 3D global aromaticity. Different types of aromaticity were therefore accessed in one molecular cage platform, depending on the symmetry, number of π-electrons and spin state.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: The design of a 3D π-conjugated diradical cage and synthesis of c-T12.
Fig. 2: Electrochemical and optical properties.
Fig. 3: X-ray crystallographic structures.
Fig. 4: Theoretical calculations and π-electron delocalization diagrams of c-T12, c-T122+, c-T124+ and c-T126+ in ground state.
Fig. 5: 1H NMR (500 MHz) spectra of c-T12 at different oxidation states.

Data availability

The authors declare that the data supporting the findings of this study are available within the paper and its Supplementary Information. Output files of the optimized geometries of c-T12, c-T122+, c-T124+, c-T126+ and c-T12′6+ in their respective ground states are available as Supplementary Data. Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition nos. CCDC 1907315 (c-T12), 1907316 (c-T122+), 1907317 (c-T124+), 1907318 (c-T125+) and 1907319 (c-T126+). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/.

References

  1. 1.

    Hückel, E. Quantentheoretische beiträge zum benzolproblem. Z. Phys. 70, 204–286 (1931).

    Google Scholar 

  2. 2.

    Krygowski, T. M., Cyrañki, M. K., Czarnocki, Z., Häelinger, G. & Katritzky, A. R. Aromaticity: a theoretical concept of immense practical importance. Tetrahedron 56, 1783–1796 (2000).

    CAS  Google Scholar 

  3. 3.

    Cyrański, M. K. Energetic aspects of cyclic π-electron delocalization: evaluation of the methods of estimating aromatic stabilization energies. Chem. Rev. 105, 3773–3811 (2005).

    PubMed  Google Scholar 

  4. 4.

    Breslow, R. Antiaromaticity. Acc. Chem. Res. 6, 393–398 (1973).

    CAS  Google Scholar 

  5. 5.

    Voter, A. F. & Goddard, W. A. The generalized resonating valence bond description of cyclobutadiene. J. Am. Chem. Soc. 108, 2830–2837 (1986).

    CAS  Google Scholar 

  6. 6.

    Tanaka, T. & Osuka, A. Chemistry of meso-aryl-substituted expanded porphyrins: aromaticity and molecular twist. Chem. Rev. 117, 2584–2640 (2017).

    CAS  PubMed  Google Scholar 

  7. 7.

    Stępień, M. & Latos-Grażyński, L. Aromaticity and tautomerism in porphyrins and porphyrinoids. Top. Heterocycl. Chem. 19, 82–153 (2008).

    Google Scholar 

  8. 8.

    Peeks, M. D., Claridge, T. D. W. & Anderson, H. L. Aromatic and antiaromatic ring currents in a molecular nanoring. Nature 541, 200–203 (2017).

    CAS  PubMed  Google Scholar 

  9. 9.

    Toriumi, N., Muranaka, A., Kayahara, E., Yamago, S. & Uchiyama, M. In-plane aromaticity in cycloparaphenylene dications: a magnetic circular dichroism and theoretical study. J. Am. Chem. Soc. 137, 82–85 (2015).

    CAS  PubMed  Google Scholar 

  10. 10.

    Baird, N. C. Quantum organic photochemistry. II. Resonance and aromaticity in the lowest 3ππ* state of cyclic hydrocarbons. J. Am. Chem. Soc. 94, 4941–4948 (1972).

    CAS  Google Scholar 

  11. 11.

    Sung, Y. M. et al. Reversal of Hückel (anti)aromaticity in the lowest triplet states of hexaphyrins and spectroscopic evidence for Baird’s rule. Nat. Chem. 7, 418–422 (2015).

    CAS  PubMed  Google Scholar 

  12. 12.

    Rosenberg, M. et al. Excited state aromaticity and antiaromaticity: opportunities for photophysical and photochemical rationalizations. Chem. Rev. 114, 5379–5425 (2014).

    CAS  PubMed  Google Scholar 

  13. 13.

    Saunders, M. et al. Unsubstituted cyclopentadienyl cation, a ground-state triplet. J. Am. Chem. Soc. 95, 3017 (1973).

    CAS  Google Scholar 

  14. 14.

    Heilbronner, E. Hückel molecular orbitals of Möbius-type conformations of annulenes. Tetrahedron Lett. 29, 1923–1928 (1964).

    Google Scholar 

  15. 15.

    Ajami, D., Oeckler, O., Simon, A. & Herges, R. Synthesis of a Möbius aromatic hydrocarbon. Nature 426, 819–821 (2003).

    CAS  PubMed  Google Scholar 

  16. 16.

    Yoon, Z. S., Osuka, A. & Kim, D. Möbius aromaticity and antiaromaticity in expanded porphyrins. Nat. Chem. 1, 113–122 (2009).

    CAS  PubMed  Google Scholar 

  17. 17.

    Stępień, M., Latos-Grażyński, L., Sprutta, N., Chwalisz, P. & Szterenberg, L. Expanded porphyrin with a split personality: a Hückel–Möbius aromaticity switch. Angew. Chem. Int. Ed. 46, 7869–7873 (2007).

    Google Scholar 

  18. 18.

    Stępień, M., Sprutta, N. & Latos-Grażyński, L. Figure eights, Möbius bands, and more: conformation and aromaticity of porphyrinoids. Angew. Chem. Int. Ed. 50, 4288–4340 (2011).

    Google Scholar 

  19. 19.

    Hirsch, A., Chen, Z. & Jiao, H. Spherical aromaticity in I h symmetrical fullerenes: the 2(N+1)2 rule. Angew. Chem. Int. Ed. 39, 3915–3917 (2000).

    CAS  Google Scholar 

  20. 20.

    Bühl, M. & Hirsch, A. Spherical aromaticity of fullerenes. Chem. Rev. 101, 1153–1183 (2001).

    PubMed  Google Scholar 

  21. 21.

    Chen, Z. & King, R. B. Spherical aromaticity: recent work on fullerenes, polyhedral boranes, and related structures. Chem. Rev. 105, 3613–3642 (2005).

    CAS  PubMed  Google Scholar 

  22. 22.

    Chen, Z., Jiao, H., Hirsch, A. & Schleyer, Pv. R. Spherical homoaromaticity. Angew. Chem. Int. Ed. 41, 4309–4312 (2002).

    CAS  Google Scholar 

  23. 23.

    Corminboeuf, C., Schleyer, P. v. R. & Warner, P. Are antiaromatic rings stacked face-to-face aromatic? Org. Lett. 9, 3263–3266 (2007).

    CAS  PubMed  Google Scholar 

  24. 24.

    Nozawa, R. et al. Stacked antiaromatic porphyrins. Nat. Commun. 7, 13620 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  25. 25.

    Högberg, H.-E., Thulin, B. & Wennerström, O. Bicyclophanehexaene, a new case cyclophane from a sixfold Wittig reaction. Tetrahedron Lett. 18, 931–934 (1977).

    Google Scholar 

  26. 26.

    Wu, Z., Lee, S. & Moore, J. S. Synthesis of three-dimensional nanoscaffolding. J. Am. Chem. Soc. 114, 8730–8732 (1992).

    CAS  Google Scholar 

  27. 27.

    Kayahara, E. et al. Synthesis and physical properties of a ball-like three-dimensional π-conjugated molecule. Nat. Commun. 4, 2694 (2013).

    PubMed  Google Scholar 

  28. 28.

    Matsui, K., Segawa, Y. & Itami, K. All-benzene carbon nanocages: size-selective synthesis, photophysical properties, and crystal structure. J. Am. Chem. Soc. 136, 16452–16458 (2014).

    CAS  PubMed  Google Scholar 

  29. 29.

    Song, J., Aratani, N., Shinokubo, H. & Osuka, A. A porphyrin nanobarrel that encapsulates C60. J. Am. Chem. Soc. 132, 16356–16357 (2010).

    CAS  PubMed  Google Scholar 

  30. 30.

    Zhang, C., Wang, Q., Long, H. & Zhang, W. A highly C70 selective shape-persistent rectangular prism constructed through one-step alkyne metathesis. J. Am. Chem. Soc. 133, 20995–21001 (2011).

    CAS  PubMed  Google Scholar 

  31. 31.

    Ke, X.-S. et al. Three-dimensional fully conjugated carbaporphyrin cage. J. Am. Chem. Soc. 140, 16455–16459 (2018).

    CAS  PubMed  Google Scholar 

  32. 32.

    Oh, J. et al. Unraveling excited-singlet-state aromaticity via vibrational Analysis. Chem 3, 870–880 (2017).

    CAS  Google Scholar 

  33. 33.

    Soya, T. et al. Internally 2,5‐thienylene‐bridged [46]decaphyrin: (annuleno)annulene network consisting of Möbius aromatic thia[28]hexaphyrins and strong Hückel aromaticity of its protonated form. Angew. Chem. Int. Ed. 56, 3232–3236 (2017).

    CAS  Google Scholar 

  34. 34.

    Cha, W.-Y. et al. Bicyclic Baird-type aromaticity. Nat. Chem. 9, 1243–1248 (2017).

    CAS  PubMed  Google Scholar 

  35. 35.

    Das, S. et al. Fully fused quinoidal/aromatic carbazole macrocycles with poly-radical characters. J. Am. Chem. Soc. 138, 7782–7790 (2016).

    CAS  PubMed  Google Scholar 

  36. 36.

    Lu, X. et al. Fluorenyl based macrocyclic polyradicaloids. J. J. Am. Chem. Soc. 139, 13173–13183 (2017).

    CAS  PubMed  Google Scholar 

  37. 37.

    Liu, C. et al. Macrocyclic polyradicaloids with unusual super-ring structure and global aromaticity. Chem 4, 1586–1595 (2018).

    CAS  Google Scholar 

  38. 38.

    Liu, C., Ni, Y., Lu, X., Li, G. & Wu, J. Global aromaticity in macrocyclic polyradicaloids: Hückel’s rule or Baird’s rule? Acc. Chem. Res. 52, 2309–2321 (2019).

    CAS  PubMed  Google Scholar 

  39. 39.

    Nakano, M. et al. Second hyperpolarizability of zethrenes. Comp. Lett. 3, 333–338 (2007).

    CAS  Google Scholar 

  40. 40.

    Kamada, K. et al. Singlet diradical character from experiment. J. Phys. Chem. Lett. 1, 937–940 (2010).

    CAS  Google Scholar 

  41. 41.

    Katritzky, A. R., Jug, K. & Oniciu, D. C. Quantitative measures of aromaticity for mono-, bi-, and tricyclic penta- and hexaatomic heteroaromatic ring systems and their interrelationships. Chem. Rev. 101, 1421–1449 (2001).

    CAS  PubMed  Google Scholar 

  42. 42.

    Schleyer, Pv. R., Jiao, H., Goldfuss, B. & Freeman, P. K. Aromaticity and antiaromaticity in five‐membered C4H4X ring systems: “classical” and “magnetic” concepts may not be “orthogonal”. Angew. Chem. Int. Ed. Engl. 34, 337–340 (1995).

    CAS  Google Scholar 

  43. 43.

    Schleyer, Pv. R., Maerker, C., Dransfeld, A., Jiao, H. & Hommes, N. J. Rv. E. Nucleus-independent chemical shifts: a simple and efficient aromaticity probe. J. Am. Chem. Soc. 118, 6317–6318 (1996).

    CAS  PubMed  Google Scholar 

  44. 44.

    Gopalakrishna, T. Y., Reddy, J. S. & Anand, V. G. An amphoteric switch to aromatic and antiaromatic states of a neutral air-stable 25π radical. Angew. Chem. Int. Ed. 53, 10984–10987 (2014).

    CAS  Google Scholar 

  45. 45.

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

    CAS  PubMed  Google Scholar 

  46. 46.

    Kubo, T. Recent progress in quinoidal singlet biradical molecules. Chem. Lett. 44, 111–122 (2015).

    Google Scholar 

  47. 47.

    Gopalakrishna, T. Y., Zeng, W., Lu, X. & Wu, J. From open-shell singlet diradicaloids to polyradicaloids. Chem. Commun. 54, 2186–2199 (2018).

    Google Scholar 

  48. 48.

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

    CAS  Google Scholar 

  49. 49.

    Choi, C. H. & Kertesz, M. Bond length alternation and aromaticity in large annulenes. J. Chem. Phy. 108, 6681––66688 (1998).

    Google Scholar 

  50. 50.

    Geuenich, D., Hess, K., Köhler, F. & Herges, R. Anisotropy of the induced current density (ACID), a general method to quantify and visualize electronic delocalization. Chem. Rev. 105, 3758–3772 (2005).

    CAS  PubMed  Google Scholar 

  51. 51.

    Valiev, R. R., Fliegl, H. & Sundholm, D. Bicycloaromaticity and Baird-type bicycloaromaticity of dithienothiophene-bridged [34]octaphyrins. Phys. Chem. Chem. Phys. 20, 17705–17713 (2018).

    CAS  PubMed  Google Scholar 

  52. 52.

    Chen, Z., Wannere, C. S., Corminboeuf, C., Puchta, R. & Schleyer, Pv. R. Nucleus-independent chemical shifts (NICS) as an aromaticity criterion. Chem. Rev. 105, 3842–3888 (2005).

    CAS  PubMed  Google Scholar 

  53. 53.

    Humphrey, W., Dalke, A. & Schulten, K. VMD-visual molecular dynamics. J. Mol. Graph. 14, 33–38 (1996).

    CAS  PubMed  Google Scholar 

  54. 54.

    Shin, J.-Y. et al. Aromaticity and photophysical properties of various topology-controlled expanded porphyrins. Chem. Soc. Rev. 39, 2751–2767 (2010).

    CAS  PubMed  Google Scholar 

Download references

Acknowledgements

J.W. acknowledges financial support from the MOE Tier 3 programme (grant no. MOE2014-T3-1-004) and NRF Investigatorship (grant no. NRF-NRFI05-2019-0005). We thank S. Tobias and H. Ott from Brucker for their support on X-ray diffraction data collection. We also thank Z. Chen in the University of Puerto Rico for his helpful discussion.

Author information

Affiliations

Authors

Contributions

J.W. and Y.N. conceived the project. Y.N. synthesized the compounds and collected the spectral data. T.Y.G. performed theoretical calculations. Y.N., T.S.H., H.P. and J.D. did magnetic measurements and analysis. Y.N., Y.H. and T.T. did the X-ray analysis. T.K. and D.K. did the transient absorption spectral measurement and analysis. All authors participated in the manuscript writing.

Corresponding author

Correspondence to Jishan Wu.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary information

Experimental methods, synthetic procedures and characterization data. Details of theoretical calculations and X-ray crystallographic analysis.

Crystallographic data

CIF for compound c-T12; CCDC reference: 1907315.

Crystallographic data

CIF for compound c-T122+; CCDC reference: 1907316.

Crystallographic data

CIF for compound c-T124+; CCDC reference: 1907317.

Crystallographic data

CIF for compound c-T125+; CCDC reference: 1907318.

Crystallographic data

CIF for compound c-T126+; CCDC reference: 1907319.

Computational data

Output files of the optimized geometries of c-T12, c-T122+, c-T124+, c-T126+ and c-T12′6+ in their respective ground states. Note that c-T12′6+ is an analogue of c-T126+ in which the Mes groups are replaced by hydrogen atoms.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Ni, Y., Gopalakrishna, T.Y., Phan, H. et al. 3D global aromaticity in a fully conjugated diradicaloid cage at different oxidation states. Nat. Chem. 12, 242–248 (2020). https://doi.org/10.1038/s41557-019-0399-2

Download citation

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing