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Chiral control of spin-crossover dynamics in Fe(II) complexes

Nature Chemistry volume 14, pages 739–745 (2022)Cite this article

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Abstract

Iron-based spin-crossover complexes hold tremendous promise as multifunctional switches in molecular devices. However, real-world technological applications require the excited high-spin state to be kinetically stable—a feature that has been achieved only at cryogenic temperatures. Here we demonstrate high-spin-state trapping by controlling the chiral configuration of the prototypical iron(II)tris(4,4′-dimethyl-2,2′-bipyridine) in solution, associated for stereocontrol with the enantiopure Δ- or Λ-enantiomer of tris(3,4,5,6-tetrachlorobenzene-1,2-diolato-κ2O1,O2)phosphorus(V) (P(O2C6Cl4)3– or TRISPHAT) anions. We characterize the high-spin-state relaxation using broadband ultrafast circular dichroism spectroscopy in the deep ultraviolet in combination with transient absorption and anisotropy measurements. We find that the high-spin-state decay is accompanied by ultrafast changes of its optical activity, reflecting the coupling to a symmetry-breaking torsional twisting mode, contrary to the commonly assumed picture. The diastereoselective ion pairing suppresses the vibrational population of the identified reaction coordinate, thereby achieving a fourfold increase of the high-spin-state lifetime. More generally, our results motivate the synthetic control of the torsional modes of iron(II) complexes as a complementary route to manipulate their spin-crossover dynamics.

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Fig. 1: Due to the lability of its Fe–N bonds, an enantiomerization of the Λ- and Δ-configurations of [Fe(dm-bpy)3]2+ occurs in solution via the intramolecular Ray–Dutt twist.
Fig. 2: Transient absorption (TA) measurements show that diastereoselective ion pairing extends the HS-state lifetime of [Fe(dm-bpy)3]2+.
Fig. 3: TAA experiments correlate the diastereoselective interaction with the conformational flexibility of [Fe(dm-bpy)3]2+’s ligand system.
Fig. 4: TRCD resolves an asymmetric decay of the HS-state circular dichroism of [Fe(dm-bpy)3]2+, indicating a symmetry-breaking structural distortion.
Fig. 5: As the spin relaxation of [Fe(dm-bpy)3]2+ is driven by the Ray–Dutt twist, the diasteromeric ion pairing traps the HS state in its vibrational potential.

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Data availability

The TA, TAA and TRCD datasets analysed and discussed in this publication are available from the Zenodo repository at https://doi.org/10.5281/zenodo.6255933.

References

  1. Molnár, G., Rat, S., Salmon, L., Nicolazzi, W. & Bousseksou, A. Spin crossover nanomaterials: from fundamental concepts to devices. Adv. Mater. 30, 1703862 (2018).

    Article  CAS  Google Scholar 

  2. Halcrow, M. A. (ed.) Spin-Crossover Materials: Properties and Applications 1st edn (Wiley, 2013).

  3. Hauser, A. in Spin Crossover in Transition Metal Compounds II. Topics in Current Chemistry Vol. 234 155–198 (Springer Berlin Heidelberg, 2004).

  4. Hauser, A., Enachescu, C., Daku, M. L., Vargas, A. & Amstutz, N. Low-temperature lifetimes of metastable high-spin states in spin-crossover and in low-spin iron(II) compounds: the rule and exceptions to the rule. Coord. Chem. Rev. 250, 1642–1652 (2006).

    Article  CAS  Google Scholar 

  5. Gawelda, W. et al. Ultrafast nonadiabatic dynamics of [FeII(bpy)3]2+ in solution. J. Am. Chem. Soc. 129, 8199–8206 (2007).

    Article  CAS  PubMed  Google Scholar 

  6. Smeigh, A. L., Creelman, M., Mathies, R. A. & McCusker, J. K. Femtosecond time-resolved optical and Raman spectroscopy of photoinduced spin crossover: temporal resolution of low-to-high spin optical switching. J. Am. Chem. Soc. 130, 14105–14107 (2008).

    Article  CAS  PubMed  Google Scholar 

  7. Consani, C. et al. Vibrational coherences and relaxation in the high-spin state of aqueous [FeII(bpy)3]2+. Angew. Chem. Int. Ed. 48, 7184–7187 (2009).

    Article  CAS  Google Scholar 

  8. Auböck, G. & Chergui, M. Sub-50-fs photoinduced spin crossover in [Fe(bpy)3]2+. Nat. Chem. 7, 629–633 (2015).

    Article  PubMed  CAS  Google Scholar 

  9. Gawelda, W. et al. Structural determination of a short-lived excited iron(II) complex by picosecond X-ray absorption spectroscopy. Phys. Rev. Lett. 98, 057401 (2007).

    Article  PubMed  CAS  Google Scholar 

  10. Bressler, C. et al. Femtosecond XANES study of the light-induced spin crossover dynamics in an iron(II) complex. Science 323, 489–492 (2009).

    Article  CAS  PubMed  Google Scholar 

  11. Huse, N. et al. Femtosecond soft X-ray spectroscopy of solvated transition-metal complexes: deciphering the interplay of electronic and structural dynamics. J. Phys. Chem. Lett. 2, 880–884 (2011).

    Article  CAS  PubMed  Google Scholar 

  12. Zhang, W. et al. Tracking excited-state charge and spin dynamics in iron coordination complexes. Nature 509, 345–348 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  13. Lemke, H. T. et al. Coherent structural trapping through wave packet dispersion during photoinduced spin state switching. Nat. Commun. 8, 15342 (2017).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  14. Buhks, E., Navon, G., Bixon, M. & Jortner, J. Spin conversion processes in solutions. J. Am. Chem. Soc. 102, 2918–2923 (1980).

    Article  CAS  Google Scholar 

  15. Sutin, N. Nuclear, electronic, and frequency factors in electron transfer reactions. Acc. Chem. Res. 15, 275–282 (1982).

    Article  CAS  Google Scholar 

  16. Decurtins, S., Gütlich, P., Köhler, C. P., Spiering, H. & Hauser, A. Light-induced excited spin state trapping in a transition-metal complex: the hexa-1-propyltetrazole-iron (II) tetrafluoroborate spin-crossover system. Chem. Phys. Lett. 105, 1–4 (1984).

    Article  CAS  Google Scholar 

  17. Cammarata, M. et al. Sequential activation of molecular breathing and bending during spin-crossover photoswitching revealed by femtosecond optical and X-ray absorption spectroscopy. Phys. Rev. Lett. 113, 227402 (2014).

    Article  PubMed  CAS  Google Scholar 

  18. Nance, J., Bowman, D. N., Mukherjee, S., Kelley, C. T. & Jakubikova, E. Insights into the spin-state transitions in [Fe(tpy)2]2+: importance of the terpyridine rocking motion. Inorg. Chem. 54, 11259–11268 (2015).

    Article  CAS  PubMed  Google Scholar 

  19. Zhang, W. & Gaffney, K. J. Mechanistic studies of photoinduced spin crossover and electron transfer in inorganic complexes. Acc. Chem. Res. 48, 1140–1148 (2015).

    Article  CAS  PubMed  Google Scholar 

  20. Stock, P. et al. Molecular spin crossover in slow motion: light-induced spin-state transitions in trigonal prismatic iron(II) complexes. Inorg. Chem. 55, 5254–5265 (2016).

    Article  CAS  PubMed  Google Scholar 

  21. Marchivie, M., Guionneau, P., Létard, J.-F. & Chasseau, D. Photo-induced spin-transition: the role of the iron(II) environment distortion. Acta Crystallogr. B Struct. Sci. 61, 25–28 (2005).

    Article  CAS  Google Scholar 

  22. Halcrow, M. Structure:function relationships in molecular spin-crossover complexes. Chem. Soc. Rev. 40, 4119–4142 (2011).

    Article  CAS  PubMed  Google Scholar 

  23. Purcell, K. F. & Zapata, J. P. Magnetic isomers. cis-bis(cyanotriphenylborato)bisphenanthrolineiron(II). J. Chem. Soc. Chem. Commun. 1978, 497–499 (1978).

  24. Purcell, K. F. Pseudorotational intersystem crossing in d6 complexes. J. Am. Chem. Soc. 101, 5147–5152 (1979).

    Article  CAS  Google Scholar 

  25. Vanquickenborne, L. G. & Pierloot, K. Role of spin change in the stereomobile reactions of strong-field d6 transition-metal complexes. Inorg. Chem. 20, 3673–3677 (1981).

    Article  CAS  Google Scholar 

  26. McCusker, J. K., Rheingold, A. L. & Hendrickson, D. N. Variable-temperature studies of laser-initiated 5T2 → 1A1 intersystem crossing in spin-crossover complexes: empirical correlations between activation parameters and ligand structure in a series of polypyridyl ferrous complexes. Inorg. Chem. 35, 2100–2112 (1996).

    Article  CAS  Google Scholar 

  27. Ashley, D. C. & Jakubikova, E. Ray-Dutt and Bailar twists in Fe(II)-tris(2,2′-bipyridine): spin states, sterics, and Fe–N bond strengths. Inorg. Chem. 57, 5585–5596 (2018).

    Article  CAS  PubMed  Google Scholar 

  28. Lacour, J., Jodry, J. J., Ginglinger, C. & Torche-Haldimann, S. Diastereoselective ion pairing of TRISPHAT anions and tris(4,4′-dimethyl-2,2′-bipyridine)iron(II). Angew. Chem. Int. Ed. 37, 2379–2380 (1998).

    Article  CAS  Google Scholar 

  29. Frantz, R., Pinto, A., Constant, S., Bernardinelli, G. & Lacour, J. Fluorinated TRISPHAT anions: spectroscopic probes for detailed asymmetric ion pairing studies. Angew. Chem. Int. Ed. 44, 5060–5064 (2005).

    Article  CAS  Google Scholar 

  30. Reddy, G. M., Ballesteros-Garrido, R., Lacour, J. & Caldarelli, S. Determination of labile chiral supramolecular ion pairs by chromatographic NMR spectroscopy. Angew. Chem. Int. Ed. 52, 3255–3258 (2013).

    Article  CAS  Google Scholar 

  31. Oppermann, M. et al. Ultrafast broadband circular dichroism in the deep ultraviolet. Optica 6, 56–60 (2019).

    Article  CAS  Google Scholar 

  32. Oppermann, M. et al. Broad-band ultraviolet CD spectroscopy of ultrafast peptide backbone conformational dynamics. J. Phys. Chem. Lett. 10, 2700–2705 (2019).

    Article  CAS  PubMed  Google Scholar 

  33. Miller, J. N. & McCusker, J. K. Outer-sphere effects on ligand-field excited-state dynamics: solvent dependence of high-spin to low-spin conversion in [Fe(bpy)3]2+. Chem. Sci. 11, 5191–5204 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  34. Wallin, S., Davidsson, J., Modin, J. & Hammarström, L. Femtosecond transient absorption anisotropy study on [Ru(bpy)3]2+ and [Ru(bpy)(py)4]2+. Ultrafast interligand randomization of the MLCT state. J. Phys. Chem. A 109, 4697–4704 (2005).

    Article  CAS  PubMed  Google Scholar 

  35. Fan, J., Autschbach, J. & Ziegler, T. Electronic structure and circular dichroism of tris(bipyridyl) metal complexes within density functional theory. Inorg. Chem. 49, 1355–1362 (2010).

    Article  CAS  PubMed  Google Scholar 

  36. Rudolph, M. & Autschbach, J. Calculation of optical rotatory dispersion and electronic circular dichroism for tris-bidentate groups 8 and 9 metal complexes, with emphasis on exciton coupling. J. Phys. Chem. A 115, 2635–2649 (2011).

    Article  CAS  PubMed  Google Scholar 

  37. Richardson, F., Caliga, D., Hilmes, G. & Jenkins, J. Vibronic effects in the chiroptical spectra of dissymmetric trigonal systems. Mol. Phys. 30, 257–280 (1975).

    Article  CAS  Google Scholar 

  38. Zgierski, M. Z. & Pawlikowski, M. Jahn–Teller, pseudo Jahn–Teller coupling, and circular dichroism spectra of (E+A)e systems. J. Chem. Phys. 70, 3444–3452 (1979).

    Article  CAS  Google Scholar 

  39. Rodger, A. Template symmetry restrictions on reaction mechanisms. Inorganica Chim. Acta 185, 193–200 (1991).

    Article  CAS  Google Scholar 

  40. Zhang, X. et al. Dynamic Jahn–Teller effect in the metastable high-spin state of solvated [Fe(terpy)2]2+. J. Phys. Chem. C 119, 3312–3321 (2015).

    Article  CAS  Google Scholar 

  41. Carey, M. C., Adelman, S. L. & McCusker, J. K. Insights into the excited state dynamics of Fe(II) polypyridyl complexes from variable-temperature ultrafast spectroscopy. Chem. Sci. 10, 134–144 (2018).

    Article  PubMed  PubMed Central  Google Scholar 

  42. Paulus, B. C., Adelman, S. L., Jamula, L. L. & McCusker, J. K. Leveraging excited-state coherence for synthetic control of ultrafast dynamics. Nature 582, 214–218 (2020).

    Article  CAS  PubMed  Google Scholar 

  43. McCusker, J. K. Electronic structure in the transition metal block and its implications for light harvesting. Science 363, 484–488 (2019).

    Article  CAS  PubMed  Google Scholar 

  44. Wenger, O. S. Is iron the new ruthenium? Chem. Eur. J. 25, 6043–6052 (2019).

    Article  CAS  PubMed  Google Scholar 

  45. Kepp, K. P. Heme: from quantum spin crossover to oxygen manager of life. Coord. Chem. Rev. 344, 363–374 (2017).

    Article  CAS  Google Scholar 

  46. Kinschel, D. et al. Femtosecond X-ray emission study of the spin cross-over dynamics in haem proteins. Nat. Commun. 11, 4145 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  47. Ki, H., Oang, K. Y., Kim, J. & Ihee, H. Ultrafast X-ray crystallography and liquidography. Ann. Rev. Phys. Chem. 68, 473–497 (2017).

    Article  CAS  Google Scholar 

  48. Pomeranc, D., Heitz, V., Chambron, J.-C. & Sauvage, J.-P. Octahedral Fe(II) and Ru(II) complexes based on a new bis 1,10-phenanthroline ligand that imposes a well defined axis. J. Am. Chem. Soc. 123, 12215–12221 (2001).

    Article  CAS  PubMed  Google Scholar 

  49. Cazzanti, S., Caramori, S., Argazzi, R., Elliott, C. M. & Bignozzi, C. A. Efficient non-corrosive electron-transfer mediator mixtures for dye-sensitized solar cells. J. Am. Chem. Soc. 128, 9996–9997 (2006).

    Article  CAS  PubMed  Google Scholar 

  50. Lacour, J., Ginglinger, C., Grivet, C. & Bernardinelli, G. Synthesis and resolution of the configurationally stable tris(tetrachlorobenzenediolato)phosphate(V) ion. Angew. Chem. Int. Ed. 36, 608–610 (1997).

    Article  CAS  Google Scholar 

  51. Favarger, F., Goujon-Ginglinger, C., Monchaud, D. & Lacour, J. Large-scale synthesis and resolution of TRISPHAT [tris(tetrachlorobenzenediolato) phosphate(V)] anion. J. Org. Chem. 69, 8521–8524 (2004).

    Article  CAS  PubMed  Google Scholar 

  52. Mason, S. F., Peart, B. J. & Waddell, R. E. Optical rotatory power of co-ordination compounds. Part XVI. Intermediate exciton coupling in the circular dichroism of trisbipyridyl complexes. J. Chem. Soc. Dalton Trans. 1973, 944–949 (1973).

    Article  Google Scholar 

  53. Castellucci, E., Salvi, P. R. & Foggi, P. Two-photon excitation spectra of the lowest electronic states of 2,2′-bipyridine. Chem. Phys. 66, 281–291 (1982).

    Article  CAS  Google Scholar 

  54. Mason, S. F. The electronic spectra and optical activity of phenanthroline and dipyridyl metal complexes. Inorganica Chim. Acta Rev. 2, 89–109 (1968).

    Article  CAS  Google Scholar 

  55. Bosnich, B. Application of exciton theory to the determination of the absolute configurations of inorganic complexes. Acc. Chem. Res. 2, 266–273 (1969).

    Article  CAS  Google Scholar 

  56. Reist, M., Testa, B., Carrupt, P.-A., Jung, M. & Schurig, V. Racemization, enantiomerization, diastereomerization, and epimerization: their meaning and pharmacological significance. Chirality 7, 396–400 (1995).

    Article  CAS  Google Scholar 

  57. Jodry, J. J., Frantz, R. & Lacour, J. Supramolecular stereocontrol of octahedral metal-centered chirality. Ligand modulation. Inorg. Chem. 43, 3329–3331 (2004).

    Article  CAS  PubMed  Google Scholar 

  58. Auböck, G. et al. Femtosecond pump/supercontinuum-probe setup with 20 kHz repetition rate. Rev. Sci. Instrum. 83, 093105 (2012).

    Article  PubMed  CAS  Google Scholar 

  59. Auböck, G., Consani, C., Mourik, F. V. & Chergui, M. Ultrabroadband femtosecond two-dimensional ultraviolet transient absorption. Opt. Lett. 37, 2337–2339 (2012).

    Article  PubMed  Google Scholar 

  60. Baum, P., Lochbrunner, S. & Riedle, E. Tunable sub-10-fs ultraviolet pulses generated by achromatic frequency doubling. Opt. Lett. 29, 1686–1688 (2004).

    Article  CAS  PubMed  Google Scholar 

  61. Slavov, C., Hartmann, H. & Wachtveitl, J. Implementation and evaluation of data analysis strategies for time-resolved optical spectroscopy. Anal. Chem. 87, 2328–2336 (2015).

    Article  CAS  PubMed  Google Scholar 

  62. Jiang, Y. et al. Direct observation of nuclear reorganization driven by ultrafast spin transitions. Nat. Commun.11, 1530 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  63. Bethardy, G., Wang, X. & Perry, D. S. The role of molecular flexibility in accelerating intramolecular vibrational relaxation. Can. J. Chem. 72, 652–659 (1994).

    Article  CAS  Google Scholar 

  64. Berova, N., Polavarapu, P. L., Nakanishi, K. & Woody, R. W. (eds) Comprehensive Chiroptical Spectroscopy: Instrumentation, Methodologies, and Theoretical Simulations Vol. 1 (Wiley, 2012).

  65. Meyer-Ilse, J., Akimov, D. & Dietzek, B. Recent advances in ultrafast time-resolved chirality measurements: perspective and outlook: ultrafast transient molecular chirality. Laser Photonics Rev. 7, 495–505 (2013).

    Article  CAS  Google Scholar 

  66. Feng, Y., Vinogradov, I. & Ge, N.-H. General noise suppression scheme with reference detection in heterodyne nonlinear spectroscopy. Opt. Express 25, 26262–26279 (2017).

    Article  CAS  PubMed  Google Scholar 

  67. Feng, Y., Vinogradov, I. & Ge, N.-H. Optimized noise reduction scheme for heterodyne spectroscopy using array detectors. Opt. Express 27, 20323–20346 (2019).

    Article  CAS  PubMed  Google Scholar 

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Acknowledgements

We thank J. Spekowius and J. Helbing (Zürich University) for adapting and sharing the B-Matrix referencing methodology and S. Grass (Geneva University) for the preparation of the enantiopure ammonium TT salts. We also thank L. Müller and B. Bauer (École Polytechnique Fédérale de Lausanne (EPFL)) for assistance in the laboratory and X. Kong and C. Heinis (EPFL) for providing access to a steady-state circular dichroism spectrometer. Finally, we thank L. M. Lawson Daku (Geneva University), G. Pescitelli and F. Santoro (Pisa University) for helpful discussions. This work was supported by the Swiss National Science Foundation (SNSF) through the National Center of Competence in Research (NCCR) Molecular Ultrafast Science and Technology (MUST). M.O. was supported by a fellowship within the postdoc programme of the German Academic Exchange Service (DAAD).

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Authors and Affiliations

  1. Laboratory of Ultrafast Spectroscopy (LSU) and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne, ISIC-FSB, Lausanne, Switzerland

    Malte Oppermann & Majed Chergui

  2. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Pisa, Italy

    Francesco Zinna

  3. Département de Chimie Organique, Université de Genève, Geneva, Switzerland

    Francesco Zinna & Jérôme Lacour

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  1. Malte Oppermann
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Contributions

J.L. and M.O. conceived the original idea. M.O. coordinated and carried out all aspects of the research (experiments, data analysis and interpretation), discussing them regularly with M.C.; F.Z. and J.L. contributed to sample preparation and manipulation and to discussions about the stereochemistry of the complexes. M.O. wrote the manuscript with contributions from all authors.

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Correspondence to Malte Oppermann.

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Extended data

Extended Data Fig. 1 Steady-state characterization of the diastereomeric ion pair [Fe(dm-bpy)3][Λ-TT]2.

Detailed comparison of the spectroscopic properties of the diastereomeric ion pair in its Λ configuration when dissolved in CHCl3 and CH2Cl2: Comparison of molar extinction as a function of wavelength (a), comparison of CD spectra normalized to their maximum amplitude (b), spectral decomposition of the normalized absorption spectrum in CHCl3 (c), and spectral decomposition of the normalized CD spectrum in CHCl3 (d). The inset in panel (a) displays the structure of the Λ configuration of the TT anion.

Extended Data Fig. 2 Results from the global analysis of the TA experiments.

Decay-associated spectra (DAS, left panels) and species-associated spectra (SAS, right panels) obtained from a global analysis of the TA data of [Fe(dm-bpy)3][Λ-TT]2 in CHCl3 (a,b), in CH2Cl2 (c,d), and [Fe(dm-bpy)3][PF6]2 in CH2Cl2 (e,f) after photoexcitation of the MLCT band at 530 nm. For the plots of the DAS, a TA spectrum at 5 ps is included to show the positions of the GSB and ESA bands.

Extended Data Fig. 3 Results from the global analysis of the TAA experiments.

Decay-associated spectra (DAS, left panels) and species-associated spectra (SAS, right panels) obtained from a global analysis of the TAA data of [Fe(dm-bpy)3][Λ-TT]2 in CHCl3 (a,b), in CH2Cl2 (c,d), and [Fe(dm-bpy)3][PF6]2 in CH2Cl2 (e,f) after photoexcitation of the MLCT band at 530 nm. For both the DAS and the SAS, a TAA spectrum at 5 ps is included to show the positions of the main TAA bands and zero-crossings.

Extended Data Fig. 4 Spectrally resolved data from the TRCD experiments.

TRCD spectra as a function of pump-probe delay for Λ-Fecont(a), Λ-Fecont(b), Λ-Fesep(c), and Λ-Fesep(d). For the Λ configurations a total of 26 pump-probe delays are displayed, whereas 9 pump-probe delays are displayed for the Λ configurations. For all samples, the maximum absorbance near 295 nm was approximately 0.7 OD in a 0.5 mm pathlength flow cell. The samples were photoexcited at 530 nm with a peak fluence of approximately 3.5 mJ cm−2.

Extended Data Fig. 5 Model calculations of the HS-state TAA as a function of the ligands’ conformational ensemble.

Calculation of expected anisotropy values from the long-axis ligand centred (LC) transition dipoles of a tris-chelate complex photoexcited via one of its MLCT transitions (here: \(\stackrel{\rightharpoonup}{M}_{1}\) on ligand 1). a) Anisotropy calculated for individual LC transition dipoles as a function of their out-of-ligand-plane rotation angle. The inset displays the employed coordinate system and the labelling of the transition dipoles. b) Anisotropy calculated for individual LC transition dipoles as a function of their in-ligand-plane rotation angle around the origin of the coordinate system. c) Anisotropy obtained from a conformational ensemble over the in- and out-of-ligand-plane rotation angles as a function of the standard deviation of the associated two-dimensional Gaussian distribution. The average anisotropy value (solid black line) corresponds to the value obtained in an experimental measurement. d) One-dimensional Gaussian distributions with selected standard deviations, illustrating the conformational ensembles associated with the anisotropy values measured in the presented experiments.

Extended Data Fig. 6 Decomposition of representative TA and TRCD spectra into ground state bleach and excited state absorption contributions.

Spectral decomposition of the simultaneously acquired TA (a) and TRCD (b) spectrum of Λ-Fecont at 5 ps into a GSB and a HS-state contribution consisting of Gaussian bands. Note that in (a) the GSB and ESA bands are scaled by a factor of 0.5 for a better comparison with the TA spectrum.

Extended Data Fig. 7 Assessment of the sensitivity of the TRCD experiments and the suppression of polarization artefacts.

The left-most panels display the TRCD spectrum at -0.1 ps and 10 ps for racemic [Fe(bpy)3]Cl2 in H2O, where any non-zero signal is attributed to polarization artifacts. These measurements were performed prior to each of the reported TRCD experiments: a) for Λ-Fecont, b) for Λ-Fesep, and c) for Λ-Fecont and -Fesep, which were measured back-to-back. The right panels display the TRCD spectra at -0.1 ps for each of the four samples, including the associated standard error as a shaded area.

Supplementary information

Supplementary Information

Supplementary Figs. 1–27, Tables 1–5 and Discussions on the steady-state sample characterization, the TA experiments, the TAA experiments and the TRCD experiments.

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Oppermann, M., Zinna, F., Lacour, J. et al. Chiral control of spin-crossover dynamics in Fe(II) complexes. Nat. Chem. 14, 739–745 (2022). https://doi.org/10.1038/s41557-022-00933-0

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