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Aromatic and antiaromatic ring currents in a molecular nanoring

Nature volume 541, pages 200–203 (2017)Cite this article

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Abstract

Aromatic and antiaromatic molecules—which have delocalized circuits of [4n + 2] or [4n] electrons, respectively—exhibit ring currents around their perimeters1,2,3,4. The direction of the ring current in an aromatic molecule is such as to generate a magnetic field that opposes the external field inside the ring (a ‘diatropic’ current), while the ring current in an antiaromatic molecule flows in the reverse direction (‘paratropic’)5. Similar persistent currents occur in metal or semiconductor rings, when the phase coherence of the electronic wavefunction is preserved around the ring6,7. Persistent currents in non-molecular rings switch direction as a function of the magnetic flux passing through the ring, so that they can be changed from diatropic (‘aromatic’) to paratropic (‘antiaromatic’) simply by changing the external magnetic field. As in molecular systems, the direction of the persistent current also depends on the number of electrons8. The relationship between ring currents in molecular and non-molecular rings is poorly understood, partly because they are studied in different size regimes: the largest aromatic molecules have diameters of about one nanometre, whereas persistent currents are observed in microfabricated rings with diameters of 20–1,000 nanometres. Understanding the connection between aromaticity and quantum-coherence effects in mesoscopic rings provides a motivation for investigating ring currents in molecules of an intermediate size9. Here we show, using nuclear magnetic resonance spectroscopy and density functional theory, that a six-porphyrin nanoring template complex, with a diameter of 2.4 nanometres, is antiaromatic in its 4+ oxidation state (80 π electrons) and aromatic in its 6+ oxidation state (78 π electrons). The antiaromatic state has a huge paramagnetic susceptibility, despite having no unpaired electrons. This work demonstrates that a global ring current can be promoted in a macrocycle by adjusting its oxidation state to suppress the local ring currents of its components.The discovery of ring currents around a molecule with a circumference of 7.5 nanometres, at room temperature, shows that quantum coherence can persist in surprisingly large molecular frameworks.

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Figure 1: Molecular structures of the butadiyne-linked porphyrin oligomers used in this study. l-PN, c-PN and c-P6·T6.
Figure 2: Computational data supporting aromaticity and antiaromaticity.
Figure 3: Square-wave voltammetry of c-P6·T6.
Figure 4: NMR spectra of neutral and oxidised c-P6·T6.

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References

  1. Spitler, E. L., Johnson, C. A., II & Haley, M. M. Renaissance of annulene chemistry. Chem. Rev. 106, 5344–5386 (2006)

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  3. Gleiter, R. & Haberhauer, G. Aromaticity and Other Conjugation Effects (Wiley-VCH, 2012)

  4. Lazzeretti, P . Ring currents. Prog. NMR Spectrosc. 36, 1–88 (2000)

    Article  CAS  Google Scholar 

  5. Gomes, J. A. N. F. & Mallion, R. B. Aromaticity and ring currents. Chem. Rev. 101, 1349–1384 (2001)

    Article  CAS  Google Scholar 

  6. Bleszynski-Jayich, A. C. et al. Persistent currents in normal metal rings. Science 326, 272–275 (2009)

    Article  ADS  CAS  Google Scholar 

  7. Lorke, A. et al. Spectroscopy of nanoscopic semiconductor rings. Phys. Rev. Lett. 84, 2223–2226 (2000)

    Article  ADS  CAS  Google Scholar 

  8. Loss, D. & Goldbart, P. Period and amplitude halving in mesoscopic rings with spin. Phys. Rev. B 43, 13762–13765 (1991)

    Article  ADS  Google Scholar 

  9. Mayor, M. & Didschies, C. A giant conjugated molecular ring. Angew. Chem. Int. Ed. 42, 3176–3179 (2003)

    Article  CAS  Google Scholar 

  10. Wannere, C. S. & von Ragué Schleyer, P . How aromatic are large (4n + 2) π annulenes? Org. Lett. 5, 865–868 (2003)

    Article  CAS  Google Scholar 

  11. Choi, C. H. & Kertesz, M. Bond length alternation and aromaticity in large annulenes. J. Chem. Phys. 108, 6681–6688 (1998)

    Article  ADS  CAS  Google Scholar 

  12. Soncini, A., Fowler, P. W. & Jenneskens, L. W. Ring currents in large [4n + 2]-annulenes. Phys. Chem. Chem. Phys. 6, 277–284 (2004)

    Article  CAS  Google Scholar 

  13. Soya, T., Kim, W., Kim, D. & Osuka, A. Stable [48]-, [50]-, and [52]dodecaphyrins(1.1.0.1.1.0.1.1.0.1.1.0): the largest Hückel aromatic molecules. Chem. Eur. J. 21, 8341–8346 (2015)

    Article  CAS  Google Scholar 

  14. 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)

    Article  CAS  Google Scholar 

  15. Kondratuk, D. V. et al. Supramolecular nesting of cyclic polymers. Nat. Chem. 7, 317–322 (2015)

    Article  CAS  Google Scholar 

  16. Liu, P. et al. Synthesis of five-porphyrin nanorings by using ferrocene and corannulene templates. Angew. Chem. Int. Ed. 55, 8358–8362 (2016)

    Article  CAS  Google Scholar 

  17. Sprafke, J. K. et al. Belt-shaped π-systems: relating geometry to electronic structure in a six-porphyrin nanoring. J. Am. Chem. Soc. 133, 17262–17273 (2011)

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  19. Geuenich, D., Hess, K., Kohler, 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)

    Article  CAS  Google Scholar 

  20. Connelly, N. G. & Geiger, W. E. Chemical redox agents for organometallic chemistry. Chem. Rev. 96, 877–910 (1996)

    Article  CAS  Google Scholar 

  21. Karunanithy, G. et al. Harnessing NMR relaxation interference effects to characterise supramolecular assemblies. Chem. Commun. (Camb.) 52, 7450–7453 (2016)

    Article  CAS  Google Scholar 

  22. Evans, D. F. 400. The determination of the paramagnetic susceptibility of substances in solution by nuclear magnetic resonance. J. Chem. Soc. 2003–2005 (1959)

  23. Tellgren, E. I., Helgaker, T. & Soncini, A. Non-perturbative magnetic phenomena in closed-shell paramagnetic molecules. Phys. Chem. Chem. Phys. 11, 5489–5498 (2009)

    Article  CAS  Google Scholar 

  24. Dauben, H. J. Jr, Wilson, J. D. & Laity, J. L. Diamagnetic susceptibility exaltation in hydrocarbons. J. Am. Chem. Soc. 91, 1991–1998 (1969)

    Article  CAS  Google Scholar 

  25. Tamura, R., Ikuta, M., Hirahara, T. & Tsukada, M. Positive magnetic susceptibility in polygonal nanotube tori. Phys. Rev. B 71, 045418 (2005)

    Article  ADS  Google Scholar 

  26. Yamamoto, Y. et al. Synthesis, reactions, and electronic properties of 16 π-electron octaisobutyltetraphenylporphyrin. J. Am. Chem. Soc. 132, 12627–12638 (2010)

    Article  CAS  Google Scholar 

  27. Gouterman, M. Spectra of porphyrins. J. Mol. Spectrosc. 6, 138–163 (1961)

    Article  ADS  CAS  Google Scholar 

  28. Lin, V. S.-Y. & Therien, M. J. The role of porphyrin-to-porphyrin linkage topology in the extensive modulation of the absorptive and emissive properties of a series of ethynyl- and butadiynyl- bridged bis- and tris(porphinato)zinc chromophores. Chem. Eur. J. 1, 645–651 (1995)

    Article  Google Scholar 

  29. Peeks, M. D., Neuhaus, P. & Anderson, H. L. Experimental and computational evaluation of the barrier to torsional rotation in a butadiyne-linked porphyrin dimer. Phys. Chem. Chem. Phys. 18, 5264–5274 (2016)

    Article  CAS  Google Scholar 

  30. Perrin, C. L. & Dwyer, T. J. Application of two-dimensional NMR to kinetics of chemical exchange. Chem. Rev. 90, 935–967 (1990)

    Article  CAS  Google Scholar 

  31. Tait, C. E., Neuhaus, P., Peeks, M. D., Anderson, H. L. & Timmel, C. R . Transient EPR reveals triplet state delocalization in a series of cyclic and linear π-conjugated porphyrin oligomers. J. Am. Chem. Soc. 137, 8284–8293 (2015)

    Article  CAS  Google Scholar 

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

  33. Becke, A. D. Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98, 5648–5652 (1993)

    Article  ADS  CAS  Google Scholar 

  34. Hehre, W. J., Ditchfield, R. & Pople, J. A. Self-consistent molecular orbital methods. XII. Further extensions of Gaussian-type basis sets for use in molecular orbital studies of organic molecules. J. Chem. Phys. 56, 2257–2261 (1972)

    Article  ADS  CAS  Google Scholar 

  35. Rassolov, V. A., Pople, J. A., Ratner, M. A. & Windus, T. L. 6-31G* basis set for atoms K through Zn. J. Chem. Phys. 109, 1223–1229 (1998)

    Article  ADS  CAS  Google Scholar 

  36. Grimme, S., Antony, J., Ehrlich, S. & Krieg, H. A consistent and accurate ab initio parameterization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 132, 154104 (2010)

    Article  ADS  Google Scholar 

  37. Zhao, Y. & Truhlar, D. G. The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theor. Chem. Acc. 120, 215–241 (2008)

    Article  CAS  Google Scholar 

  38. Chai, J.-D. & Head-Gordon, M. Long-range corrected hybrid density functionals with damped atom-atom dispersion corrections. Phys. Chem. Chem. Phys. 10, 6615–6620 (2008)

    Article  CAS  Google Scholar 

  39. Jeener, J., Meier, B. H., Bachmann, P. & Ernst, R. R. Investigation of exchange processes by two-dimensional NMR spectroscopy. J. Chem. Phys. 71, 4546–4549 (1979)

    Article  ADS  CAS  Google Scholar 

  40. Green, M. L. H., Wong, L. L. & Sella, A. Relationship between intramolecular chemical exchange and NMR-observed rate constants. Organometallics 11, 2660–2668 (1992)

    Article  CAS  Google Scholar 

  41. Liu, S. et al. Caterpillar track complexes in template-directed synthesis and correlated molecular motion. Angew. Chem. Int. Ed. 54, 5355–5359 (2015)

    Article  CAS  Google Scholar 

  42. Schubert, E. M. Utilizing the Evans method with a superconducting NMR spectrometer in the undergraduate laboratory. J. Chem. Educ. 69, 62 (1992)

    Article  CAS  Google Scholar 

  43. Grant, D. H. Paramagnetic susceptibility by NMR. J. Chem. Educ. 72, 39–40 (1995)

    Article  CAS  Google Scholar 

  44. Piguet, C. Paramagnetic susceptibility by NMR: the “solvent correction” removed for large paramagnetic molecules. J. Chem. Educ. 74, 815–816 (1997)

    Article  CAS  Google Scholar 

  45. Peeks, M. D., Claridge, T. D. W. & Anderson, H. L. Data for ‘aromatic and antiaromatic ring currents in a molecular nanoring’. http://dx.doi.org/10.5287/bodleian:JVB5KZaD0 (Oxford University Research Archive, 2016)

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Acknowledgements

We thank the ERC (grant 320969), the EPSRC and the John Templeton Foundation for support, B. Odell for help with NMR spectroscopy and the Oxford Advanced Research Computing (ARC) centre for the high-performance computing provision (http://dx.doi.org/10.5281/zenodo.22558). M.D.P. thanks Exeter College, Oxford, for further support.

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  1. Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Oxford, OX1 3TA, UK

    Martin D. Peeks, Timothy D. W. Claridge & Harry L. Anderson

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Contributions

M.D.P. synthesized the compounds, performed the calculations, collected and analysed the spectroscopic data. T.D.W.C. assisted with NMR data collection and interpretation. H.L.A. devised the project. M.D.P. and H.L.A. wrote the paper. All authors discussed the results and edited the manuscript.

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Correspondence to Harry L. Anderson.

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The authors declare no competing financial interests.

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Nature thanks M. Bröring and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

This file contains Supplementary Tables 1-5 and Supplementary Figures 1-27. This file was updated on 11 January 2017 to correct the DOI number. (PDF 5478 kb)

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Peeks, M., Claridge, T. & Anderson, H. Aromatic and antiaromatic ring currents in a molecular nanoring. Nature 541, 200–203 (2017). https://doi.org/10.1038/nature20798

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