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Electron spin resonance of single iron phthalocyanine molecules and role of their non-localized spins in magnetic interactions


Electron spin resonance (ESR) spectroscopy is a crucial tool, through spin labelling, in investigations of the chemical structure of materials and of the electronic structure of materials associated with unpaired spins. ESR spectra measured in molecular systems, however, are established on large ensembles of spins and usually require a complicated structural analysis. Recently, the combination of scanning tunnelling microscopy with ESR has proved to be a powerful tool to image and coherently control individual atomic spins on surfaces. Here we extend this technique to single coordination complexes—iron phthalocyanines (FePc)—and investigate the magnetic interactions between their molecular spin with either another molecular spin (in FePc–FePc dimers) or an atomic spin (in FePc–Ti pairs). We show that the molecular spin density of FePc is both localized at the central Fe atom and also distributed to the ligands (Pc), which yields a strongly molecular-geometry-dependent exchange coupling.

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Fig. 1: [FePc] molecules adsorbed on MgO/Ag(100) and ESR measurements with varied tip fields.
Fig. 2: Spin coupling in [FePc]–[FePc] dimers.
Fig. 3: DFT calculations of exchange coupling in an [FePc]–[FePc] dimer atop MgO only.
Fig. 4: Exchange coupling of [FePc]–TiB pairs with different TiB–ligand distance.
Fig. 5: Molecular-geometry-dependent exchange coupling in [FePc]–TiB pairs.

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Data availability

All the data that support the findings of this study are available in this article and its Supplementary Information, or from the corresponding authors on reasonable request. The source data and DFT models that support all the figures displayed in the main article and Supplementary Information are also publicly available through the link

Code availability

The MATLAB code used to plot and fit the ESR spectra displayed in article and Supplementary Information is available through the Figshare link, WSxM software39 was used to change the colour schemes of our STM images for better clarity; we used the integrated low-order Gaussian filtering function, a built-in function within the software, without modifications.


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All the authors acknowledge support from the Institute for Basic Science under grant IBS-R027-D1. P.W. also acknowledges funding from the Emmy Noether Programme of the DFG (WI5486/1-1). We thank N. Lorente for fruitful discussions.

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Authors and Affiliations



T.C. and X.Z. designed the project. X.Z., Y.W., T.B. and P.W. performed the experiments. C.W. carried out the DFT calculations. H.A. contributed to the Hamiltonian model simulations. X.Z. and T.C. wrote the manuscript with the help of all the authors. T.C. and A.J.H. advised the project process.

Corresponding authors

Correspondence to Andreas J. Heinrich or Taeyoung Choi.

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The authors declare no competing interests.

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Peer review information Nature Chemistry thanks the anonymous reviewers for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Sections 1–19: STM images, STM spectroscopic measurements, ESR spectra and DFT studies, additional discussion, Figs. 1–25, Tables 1–3 and references

Supplementary Data 1

All related DFT computational models used in the main article and Supplementary Information are supplied in a Supplementary zip file. Once unzipped, the name of each file indicates its content.

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Zhang, X., Wolf, C., Wang, Y. et al. Electron spin resonance of single iron phthalocyanine molecules and role of their non-localized spins in magnetic interactions. Nat. Chem. 14, 59–65 (2022).

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