Vibrational coherences in manganese single-molecule magnets after ultrafast photoexcitation

Abstract

Magnetic recording using femtosecond laser pulses has recently been achieved in some dielectric media, showing potential for ultrafast data storage applications. Single-molecule magnets (SMMs) are metal complexes with two degenerate magnetic ground states and are promising for increasing storage density, but remain unexplored using ultrafast techniques. Here we have explored the dynamics occurring after photoexcitation of a trinuclear µ3-oxo-bridged Mn(iii)-based SMM, whose magnetic anisotropy is closely related to the Jahn–Teller distortion. Ultrafast transient absorption spectroscopy in solution reveals oscillations superimposed on the decay traces due to a vibrational wavepacket. Based on complementary measurements and calculations on the monomer Mn(acac)3, we conclude that the wavepacket motion in the trinuclear SMM is constrained along the Jahn–Teller axis due to the µ3-oxo and µ-oxime bridges. Our results provide new possibilities for optical control of the magnetization in SMMs on femtosecond timescales and open up new molecular-design challenges to control the wavepacket motion in the excited state of polynuclear transition-metal complexes.

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Fig. 1: The structures of JT-distorted Mn(iii) complexes.
Fig. 2: Electronic absorption spectra of Mn(acac)3 and Mn3.
Fig. 3: Ultrafast transient absorption spectra of Mn(acac)3 and Mn3.
Fig. 4: Kinetic traces of Mn(acac)3 and Mn3.
Fig. 5: Analysis of vibrational wavepacket.
Fig. 6: Photophysical model of the Mn(acac)3 dynamics and wavepacket motion in Mn3.

Data availability

The raw transient absorption data (including the anisotropy measurements), Raman and ultraviolet–visible spectra, and computational data that support the findings of this study are available in the Edinburgh DataShare repository with the identifier https://doi.org/10.7488/ds/2751.

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Acknowledgements

This work was supported by funding from the Royal Society of Edinburgh and the Carnegie Trust (Collaborative Research Grant). The authors thank M. D. Horbury and V. Stavros for allowing us to carry out preliminary measurements in their laboratory and for their assistance with these measurements. F.L. and J.O.J. thank A. Gromov for the help with the Raman spectrometer and E. Riedle for helpful advice with building the transient absorption set-up. J.O.J. is a Royal Society of Edinburgh/BP Trust research fellow. E.K.B. thanks the EPSRC for grants EP/P025986/1 and EP/N01331X/1. T.J.P. and J.E. thank the EPSRC for grants EP/R021503/1 and EP/P012388/1.

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Contributions

F.L. performed the optical experiments and analysed the data and R.McN synthesized and characterized the samples under the supervision of R.I. and E.K.B. J.E. and T.J.P. carried out the calculations. F.L., E.K.B. and J.O.J. conceived the experiments and interpreted the results. F.L. and J.O.J. co-wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to J. Olof Johansson.

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Supplementary information

Supplementary Information

Supplementary Computational Methods, Tables 1–3, Figs. 1–11 and Data.

Supplementary Video 1

Video of the vibrational mode giving rise to the wavepacket in Mn3.

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Liedy, F., Eng, J., McNab, R. et al. Vibrational coherences in manganese single-molecule magnets after ultrafast photoexcitation. Nat. Chem. 12, 452–458 (2020). https://doi.org/10.1038/s41557-020-0431-6

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