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Issue 38, 2017
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Spin-state-correlated optical properties of copper(II)–nitroxide based molecular magnets

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Molecular magnets based on copper(II) ions and stable nitroxide radicals exhibit promising switchable behavior triggered by a number of external stimuli; however, their spin-state-correlated optical properties vital for photoinduced switching have not been profoundly investigated to date. Herein, the electronic absorption spectra of single crystals of three representatives of this unique family are studied experimentally and theoretically in the visible and near-IR regions. We established that the color of the complexes is mainly determined by optical properties of the nitroxide radicals, whereas the Cu(hfac)2 fragment contributes to the near-IR range with the intensity smaller by an order of magnitude. The thermochromism of these complexes evident upon thermal spin state switching is mainly caused by a spectral shift of the absorption bands of the nitroxides. The vibrational progression observed in the visible range for single crystals as well as for solutions of pure nitroxides is well reproduced by DFT calculations, where the C–C stretching mode governs the observed progression. The analysis of the spectra of single crystals in the near-IR region reveals changes in the energy and in the intensity of the copper(II) d–d transitions, which are well reproduced by SOC-NEVPT2 calculations and owe to the flip of the Jahn–Teller axis in the coordination environment of copper. Further strategies for designing bidirectional magnetic photoswitches using these appealing compounds are discussed.

Graphical abstract: Spin-state-correlated optical properties of copper(ii)–nitroxide based molecular magnets

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The article was received on 25 Jul 2017, accepted on 03 Sep 2017 and first published on 05 Sep 2017

Article type: Paper
DOI: 10.1039/C7DT02719B
Citation: Dalton Trans., 2017,46, 13108-13117
  • Open access: Creative Commons BY-NC license
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    Spin-state-correlated optical properties of copper(II)–nitroxide based molecular magnets

    I. Yu. Barskaya, S. L. Veber, E. A. Suturina, P. S. Sherin, K. Yu. Maryunina, N. A. Artiukhova, E. V. Tretyakov, R. Z. Sagdeev, V. I. Ovcharenko, N. P. Gritsan and M. V. Fedin, Dalton Trans., 2017, 46, 13108
    DOI: 10.1039/C7DT02719B

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