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Monthly Archives: July 2024

Summer scholarship project 1. Spinning long-lived excited states (JDC/KCG)

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Kia ora

One of our funded summer scholarships available with the group.

Summer scholarship project 1. Spinning long-lived excited states (JDC/KCG)

Contact: keith.gordon@otago.ac.nz or jcrowley@chemistry.otago.ac.nz

Account code: 121.968.01.P.FE

10 weeks over the summer – dates negotiable

Molecular excited states are the key species in many renewable technologies; they are pivotal to the operation of solar cells1-3, organic light emitting diodes4, 5 and in photocatalysts.6, 7 The critical parameters for these excited states are:

1.  The efficiency of population of the desired excited state – that is how many photons get you the state required (the quantum yield)?

2.  The energy of the active excited state

3.  The lifetime of this excited state

In molecular systems there is a design tension between the creation of long-lived excited states (which are often triplet states) and the population of such states – long-lived triplet states have low spin-orbit coupling and thus their population, either by direct photoexcitation or, through subsequent excited state relaxation, is low. If spin-orbit coupling is increased, by using a metal complex, the efficiency of triplet state population is improved but this comes at the cost of decreasing the lifetime. A strategy for circumventing the undesirable effects of spin-orbit coupling is to isolate the triplet excited state away from the metal after intersystem crossing has occurred. We have shown that it is possible to make molecules that can access long-lived ligand-based triplet states called intraligand charge-transfer states.8-12 We will test this by systematic alteration of these states using earth abundant metals (such as Zn, Cu, Fe) coupled with systematic tuning of the ligand.13-20 Ultimately, this could provide materials that possess readily tuneable long-lived excited states using earth abundant metals.

  1. Kwok, E. C.-H.; Chan, M.-Y.;  Wong, K. M.-C.;  Lam, W. H.; Yam, V. W.-W., Functionalized Alkynylplatinum(II) Polypyridyl Complexes for Use as Sensitizers in Dye-Sensitized Solar Cells. Chemistry – A European Journal 2010, 16 (40), 12244-12254.
  2. Kinoshita, T.; Dy, J. T.;  Uchida, S.;  Kubo, T.; Segawa, H., Wideband dye-sensitized solar cells employing a phosphine-coordinated ruthenium sensitizer. Nature Photonics 2013, 7 (7), 535-539.
  3. Grätzel, M., Solar Energy Conversion by Dye-Sensitized Photovoltaic Cells. Inorganic Chemistry 2005, 44 (20), 6841-6851.
  4. Noda, H.; Nakanotani, H.; Adachi, C., Excited state engineering for efficient reverse intersystem crossing. Science Advances 2018, 4 (6), eaao6910.
  5. Bergmann, L.; Hedley, G. J.;  Baumann, T.;  Bräse, S.; Samuel, I. D. W., Direct observation of intersystem crossing in a thermally activated delayed fluorescence copper complex in the solid state. Science Advances 2016, 2 (1), e1500889.
  6. Proppe, A. H.; Li, Y. G. C.;  Aspuru-Guzik, A.;  Berlinguette, C. P.;  Chang, C. J.;  Cogdell, R.;  Doyle, A. G.;  Flick, J.;  Gabor, N. M.;  van Grondelle, R.;  Hammes-Schiffer, S.;  Jaffer, S. A.;  Kelley, S. O.;  Leclerc, M.;  Leo, K.;  Mallouk, T. E.;  Narang, P.;  Schlau-Cohen, G. S.;  Scholes, G. D.;  Vojvodic, A.;  Yam, V. W. W.;  Yang, J. Y.; Sargent, E. H., Bioinspiration in light harvesting and catalysis. Nat. Rev. Mater. 2020, 5 (11), 828-846.
  7. Förster, C.; Heinze, K., Photophysics and photochemistry with Earth-abundant metals – fundamentals and concepts. Chemical Society Reviews 2020.
  8. Shillito, G. E.; Preston, D.;  Traber, P.;  Steinmetzer, J.;  McAdam, C. J.;  Crowley, J. D.;  Wagner, P.;  Kupfer, S.; Gordon, K. C., Excited-State Switching Frustrates the Tuning of Properties in Triphenylamine-Donor-Ligand Rhenium(I) and Platinum(II) Complexes. Inorganic Chemistry 2020, 59 (10), 6736-6746.
  9. Shillito, G. E.; Hall, T. B. J.;  Preston, D.;  Traber, P.;  Wu, L. J.;  Reynolds, K. E. A.;  Horvath, R.;  Sun, X. Z.;  Lucas, N. T.;  Crowley, J. D.;  George, M. W.;  Kupfer, S.; Gordon, K. C., Dramatic Alteration of (ILCT)-I-3 Lifetimes Using Ancillary Ligands in Re(L)(CO)(3)(phen-TPA) (n+) Complexes: An Integrated Spectroscopic and Theoretical Study. Journal of the American Chemical Society 2018, 140 (13), 4534-4542.
  10. Barnsley, J. E.; Findlay, J. A.;  Shillito, G. E.;  Pelet, W. S.;  Scottwell, S. O.;  McIntyre, S. M.;  Tay, E. J.;  Gordon, K. C.; Crowley, J. D., Long-lived MLCT states for Ru(ii) complexes of ferrocene-appended 2,2 ‘-bipyridines. Dalton Transactions 2019, 48 (41), 15713-15722.
  11. Larsen, C. B.; van der Salm, H.;  Clark, C. A.;  Elliott, A. B. S.;  Fraser, M. G.;  Horvath, R.;  Lucas, N. T.;  Sun, X. Z.;  George, M. W.; Gordon, K. C., Intraligand Charge-Transfer Excited States in Re(I) Complexes with Donor-Substituted Dipyridophenazine Ligands. Inorganic Chemistry 2014, 53 (3), 1339-1354.
  12. Shillito, G. E.; Larsen, C. B.;  McLay, J. R. W.;  Lucas, N. T.; Gordon, K. C., Effect of Bridge Alteration on Ground- and Excited-State Properties of Ruthenium(II) Complexes with Electron-Donor-Substituted Dipyrido 3,2-a:2 ‘,3 ‘-c phenazine Ligands. Inorganic Chemistry 2016, 55 (21), 11170-11184.
  13. Preston, D.; Barnsley, J. E.;  Gordon, K. C.; Crowley, J. D., Controlled Formation of Heteroleptic Pd-2(L-a)(2)(L-b)(2) (4+) Cages. Journal of the American Chemical Society 2016, 138 (33), 10578-10585.
  14. Preston, D.; Findlay, J. A.; Crowley, J. D., Recognition Properties and Self-assembly of Planar M(2-pyridyl-1,2,3-triazole)(2) (2+) Metallo-ligands. Chemistry-an Asian Journal 2019, 14 (8), 1136-1142.
  15. Mapley, J. I.; Ross, D. A. W.;  McAdam, C. J.;  Gordon, K. C.; Crowley, J. D., Triphenylamine-substituted 2-pyridyl-1,2,3-triazole copper(I) complexes: an experimental and computational investigation. Journal of Coordination Chemistry 2019, 72 (8), 1378-1394.
  16. Preston, D.; Sutton, J. J.;  Gordon, K. C.; Crowley, J. D., A Nona-nuclear Heterometallic Pd3Pt6 “Donut”-Shaped Cage: Molecular Recognition and Photocatalysis. Angewandte Chemie-International Edition 2018, 57 (28), 8659-8663.
  17. Findlay, J. A.; McAdam, C. J.;  Sutton, J. J.;  Preston, D.;  Gordon, K. C.; Crowley, J. D., Metallosupramolecular Architectures Formed with Ferrocene-Linked Bis-Bidentate Ligands: Synthesis, Structures, and Electrochemical Studies. Inorganic Chemistry 2018, 57 (7), 3602-3614.
  18. Vasdev, R. A. S.; Preston, D.; Crowley, J. D., Functional metallosupramolecular architectures using 1,2,3-triazole ligands: it’s as easy as 1,2,3 “click”. Dalton Transactions 2017, 46 (8), 2402-2414.
  19. Barnsley, J. E.; Shillito, G. E.;  Larsen, C. B.;  van der Salm, H.;  Horvath, R.;  Sun, X. Z.;  Wu, X.;  George, M. W.;  Lucas, N. T.; Gordon, K. C., Generation of Microsecond Charge-Separated Excited States in Rhenium(I) Diimine Complexes: Driving Force Is the Dominant Factor in Controlling Lifetime. Inorganic Chemistry 2019, 58 (15), 9785-9795.
  20. Huff, G. S.; Lo, W. K. C.;  Horvath, R.;  Turner, J. O.;  Sun, X. Z.;  Weal, G. R.;  Davidson, H. J.;  Kennedy, A. D. W.;  McAdam, C. J.;  Crowley, J. D.;  George, M. W.; Gordon, K. C., Excited States of Triphenylamine-Substituted 2-Pyridyl-1,2,3-triazole Complexes. Inorganic Chemistry 2016, 55 (23), 12238-12253.

 

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