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. 2025 Aug 28;19(35):31572–31581. doi: 10.1021/acsnano.5c08710

Tip-Induced Nitrene Generation

Leonard-Alexander Lieske †,*, Aaron H Oechsle †, Igor Rončević ‡, Ilias Gazizullin §, Florian Albrecht †, Matthias Krinninger ∥, Leonhard Grill §, Friedrich Esch ∥, Leo Gross †,*
PMCID: PMC12424296  PMID: 40875785

Abstract

We generated trinitreno-s-heptazine, a small molecule featuring three nitrene centers, by tip-induced chemistry from the precursor 2,5,8-triazido-s-heptazine on bilayer NaCl on Au(111). The precursor’s azide groups were dissociated to form mono-, di- and trinitreno-s-heptazine, yielding molecules with one to three nitrene centers. The precursor and its products are characterized by atomic force microscopy and scanning tunnelling microscopy. Broken-symmetry DFT and configuration interaction calculations of inter-nitrene and intra-nitrene exchange couplings suggest a ferromagnetic coupling of the S = 1 nitrene centers, resulting in a high-spin septet ground state for neutral trinitreno-s-heptazine in the gas phase. On bilayer NaCl on Au(111), the combined results of experiments and theory suggest trinitreno-s-heptazine to be an anion with a sextet ground state.

Keywords: atomic force microscopy, tip-induced chemistry, on-surface synthesis, nitrene chemistry, computational chemistry

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Introduction

Nitrenes are known as highly reactive intermediates present in many reactions of nitrogen-containing compounds. − Because of their high reactivity, nitrenes are studied enclosed in crystals or matrices, − but are generally difficult to isolate. In this study, the tip-induced generation of individual nitrene sites in individual molecules is realized using 2,5,8-triazido-s-heptazine − as the precursor. Denitrogenation of triazido-s-heptazine has been previously achieved by X-ray illumination, photocatalysis, and thermal decomposition. ,, Heptazine- ,,− and triazine-based − structures of interest since a long time and are promising candidates for bottom-up growth of nitrogen-rich covalent organic frameworks based on carbon-nitride-based structures and 2D films. ,−

Individual nitrene centers are generally considered to be sp-hybridized, with high-spin (triplet) ground states. ,− Electron spin resonance performed on nitrene-containing molecules showed mononitrenes in a triplet ground state, dinitrenes in a quintet ground state and trinitrenes in a septet ground state. − Such molecules exhibit a strong localization of unpaired electrons on the nitrene centers. , This strong localization is attributed to the small mixing of the heteroatom orbitals with the conjugated π-system. The on-surface tip-induced generation of nitrenes might prove useful for the investigation and coupling of molecules with multiple localized spin centers.

Noncontact atomic force microscopy (AFM) with CO-functionalized tips, allows for resolving the structure of individual molecules. Additionally, scanning tunneling microscopy (STM) can be used to gain information about the open-/closed-shell character and spin ground states of molecules. − Atom manipulation is a useful tool to perform redox chemistry − and to dissociate constituent groups from precursors. − Related to our work, tip-induced generation of cyclic P3N3 by dechlorination of hexachlorophosphazene was demonstrated, and denitrogenation of azide groups yielding cyclic P3N3 was performed by photoinduced extrusion of dinitrogen from hexaazidephosphazene.

Results and Discussion

To obtain and characterize molecules that contain one, two or three nitrene groups, we generated them using tip-induced chemistry from the precursor 2,5,8-triazido-s-heptazine 1 (TAH). ,, The reaction scheme is shown in Figure .

1.

1

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Structures of triazido-s-heptazine and its tip-induced products representing the reaction sequence to form a molecule with three nitrene centers. From (a) 2,5,8-triazido-s-heptazine (TAH), 1, shown in a zwitterionic resonance structure, (b) mononitreno-s-heptazine 2, (c) dinitreno-s-heptazine 3 and (d) trinitreno-s-heptazine 4 can be generated by voltage pulses using the tip of the STM/AFM. Approximate voltage-pulse thresholds are indicated.

Nitrene generation by azide-group dissociation, i.e., cleaving off N2, was performed by applying voltage pulses with the tip placed above a molecule. The applied pulse voltages V P ranged from V P = 2 to 2.6 V resulting in maximum tunnelling currents I P in the range of I P = 0.2 pA to 20 pA during a pulse (see Note S1 for a detailed description of the voltage pulses for nitrene generation). Increased values of V P and I P were needed for each subsequent azide-group dissociation from 1 to 2 to 3. Sequential tip-induced dissociation of azide groups starting from 1 to form 2, 3 and 4 is shown in Figure S2.

Constant-current STM and constant-height AFM measurements of 1 on bilayer NaCl are shown in Figure a. STM shows a central protrusion at the location of the heptazine core surrounded by three fainter features located at the positions of the azide groups. AFM resolves the heptazine core atomically. We observe a brighter contrast (more positive Δf signal) on the nitrogen atoms compared to the carbon atoms, in agreement with computational studies of planar s-triazine moieties, which can be partly attributed to the increased electron density on the nitrogen atoms. , Differences in AFM contrast above nitrogen compared to carbon atoms in molecules have been observed in several works. − In addition to the differences in electron density, nonplanarity of the molecules contributes to the AFM contrast, as observed here, e.g., for the product trinitrine 4, see Figure d, in which the nitrene moieties are bent toward the substrate (vide infra). Moreover, at the small tip–sample distances in our experiment, tilting of the CO molecule at the tip enhances the imaging contrast but is known to lead to image distortions, ,− which result here in distorted six-membered rings in the appearance of the heptazine core. ,, The presence of nitrogen atoms in heterocycles has been shown to cause distortions in AFM images, explained by slightly polar C–N bonds. ,,, Thus, the contrast in AFM images contains information about both the chemical composition and the molecular adsorption geometry, however, both effects are challenging to separate.

2.

2

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STM and AFM measurements of 1, 2, 3, and 4 on NaCl­(2 ML)/Au(111). (a) TAH 1, (b) mononitrene 2, (c) dinitrene 3 and (d) trinitrene 4. Constant-current STM measurements are shown in the first row, constant-height AFM measurements in the second row and corresponding Laplace-filtered AFM images in the third row. For each molecule, a correspondingly oriented resonance structure is shown in the fourth row. STM parameters in (a), (b), (d) I = 1 pA, V = 0.2 V, in (c) I = 0.5 pA, V = 0.5 V. For AFM, tip-height offsets Δz from the respective STM parameters as setpoints are indicated. A positive Δz corresponds to an increase in tip–sample distance from the setpoint. Scale bars are 5 Å.

The AFM data on 1 (Figure a) indicate that the heptazine core of 1 is planar and adsorbed parallel to the surface. The orientations of all azide groups can be inferred from the AFM contrast. Figure S1 shows the experimentally determined and the simulated adsorption position of 1. The AFM simulation agrees with the experimental AFM data (Figure S1c,d). In the simulated geometry, we find that each azide group is oriented toward a sodium cation of the NaCl surface (Figure S1e).

In the STM measurement of mononitreno-s-heptazine 2 (mononitrene) (Figure b) the nitrene moiety appears with a more circular shape compared to the appearance of an azide group. In the AFM measurement, the nitrene center, i.e., the remaining N atom of the dissociated azide group, is atomically resolved. Additionally, the AFM data suggests a tilted heptazine core of 2 with respect to the NaCl surface. That is, at the position of the generated nitrene (top, left corner of the molecule in Figure b) the AFM contrast of the heptazine core appears darker, indicating that the molecule is closer to the surface at this location. In dinitreno-s-heptazine 3 (dinitrene) (Figure c) AFM resolves the two nitrene centers and again indicates a tilt of the heptazine core with respect to the sample surface. In the AFM measurement of trinitreno-s-heptazine 4 (trinitrene) (Figure d) all three nitrene centers are resolved and the heptazine core appears adsorbed with a small tilt angle with two nitrene centers close to the surface (top, and right corner of the molecule in Figure d) and one further away from the surface (bottom left corner of the molecule in Figure d). The tilted adsorption of 4 relates to the 3-fold symmetric molecule being adsorbed on the 4-fold symmetric NaCl surface, see Figure . The charge state and the spin state of 4 also have a subtle influence on the adsorption geometry, as will be discussed in the following (see also Figure S4).

3.

3

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Adsorption geometry of 4 on bilayer NaCl. (a) Constant-current STM measurement of 4 at I = 1 pA, V = 0.2 V. A dark halo and a standing-wave pattern around the molecule indicate a negative charge state of 4. The three dark circular features correspond to CO molecules. (b) Same data as (a) with a grid overlaid to extract the adsorption position of 4. The grid’s vertices indicate chlorine sites. (c) AFM measurement of 4 on bilayer NaCl. The tip-height offset Δz from the setpoint I = 1 pA, V = 0.2 V is indicated. (d) AFM simulation based on the relaxed geometry of the anionic sextet 4 on NaCl. (e) Top-down view and (f) side view of the geometry-optimized on-surface adsorption position of anionic 4 on NaCl. The calculated molecular geometry is nonplanar, with the nitrene’s nitrogen atoms being close to sodium cations of the surface.

Our measurements indicate that 1, 2, and 3 are neutral on bilayer NaCl on Au(111), whereas 4 is negatively charged. Figure a shows an individual 4 exhibiting a dark halo around the molecule and a scattering pattern that is centered at the molecule’s position. Such a pattern indicates interface-state electrons scattering at a charged adsorbate. , The dark halo can be attributed to a locally increased tunnelling barrier, due to a negative charge state. , In addition, Kelvin probe force spectroscopy data (Figure S5) support a negative charge state of 4. The precursor 1 and products 2 and 3 do not exhibit interface state scattering nor a dark halo indicating that they are charge-neutral on this surface. The charge state of 4 was stable within a bias window of V = ±0.7 V (see Figure S3). When imaging 4 at a bias voltage of V = 0.8 V, it appears 4-fold symmetric because of tip-induced changes of its adsorption orientation (see Figure ), caused by changes between four energy-degenerate adsorption orientations related to the 4-fold symmetry of the NaCl surface, with small barriers for 90° rotations of the molecule. This effect precluded imaging of the frontier orbital densities of 4.

4.

4

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STM measurements of 4 at different bias voltages. (a) STM data, I = 0.75 pA, V = 0.2 V. (b) At V = 0.8 V, 4 appears 4-fold symmetric. We interpret this by induced changes of the adsorption geometry, that is, changes between four energy-degenerate adsorption orientations, related to the 4-fold symmetry of the NaCl surface, with small barriers for 90° rotations of the molecule. These barriers might be overcome by inelastic electron tunneling processes or transient (dianionic) charging of 4. The effect precluded imaging of the frontier orbital densities of 4. (c) Lowering the bias voltage to V = 0.2 V after image (b) was acquired, showed 4 with the same contrast as before, i.e., as in (a). The circular depressions correspond to CO molecules.

Complete active space perturbation theory (CASPT2) calculations (see Methods) of 4 give an adiabatic electron affinity of 5.29 eV. For Au(111), we assume a work function of ϕAu(111) ≈ 5.26 eV. For bilayer NaCl on Au(111) we expect a decrease of the work function by about 1 eV with respect to the bare Au(111) surface, , as is seen for thin alkali-halide films deposited on coinage metals. − Thus, the calculated electron affinity of 4 suggests an anionic charge state on bilayer NaCl on Au(111). A neutral charge state of adsorbed 4 might be yielded by changing the substrate system toward one with a larger work function. However, this is not easily done by changing the metal substrate because Au(111) already features one of the largest work functions among all noble metal surfaces.

The ground state of neutral 4 was computationally examined in the gas phase. Figure schematically shows the exchange-coupling values within and between the three nitrene centers of 4. Considering a 3-fold symmetry of 4 in gas phase, the inter-nitrene coupling J is assumed to be equal between all three nitrene centers, and intra-nitrene coupling J′ to be the same for all three nitrene centers. Note that a positive (negative) coupling value indicates a ferromagnetic (antiferromagnetic) coupling between two spins. Details on the calculations and fitting procedure are given in Note S2.

5.

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Exchange coupling in trinitreno-s-heptazine, 4. Considering the symmetry of the relaxed neutral 4 in the gas-phase, the spin-alignment description can be reduced to two values: intra-nitrene coupling J′ (solid double arrows) and inter-nitrene coupling J (dashed double arrows). For each nitrene center, red arrows denote the relative spin orientation of unpaired electrons in the septet. Blue spheres denote nitrogen atoms, gray spheres denote carbon atoms.

We obtain J and J′ by mapping the broken-symmetry DFT (BS-DFT) and difference-dedicated configuration interaction (DDCI) results to a bilinear (BL) Heisenberg–Dirac-van Vleck (HDvV) Hamiltonian

ĤBL=−∑⟨i,j⟩JBLŜi·Ŝj

In this equation J ij is the exchange-coupling constant between spin operators Ŝi and Ŝj on sites i and j.

By mapping the broken-symmetry DFT results from the M06-2X hybrid functional calculations of 2, 3 and 4 onto a BL Hamiltonian, we obtain the averaged intra-nitrene coupling of J′(2,3,4)BS‑BL = 723.59 meV and, with averaged results of 3 and 4, an inter-nitrene coupling of J(3,4)BS‑BL = 5.80 meV.

Because the BL HDvV model might not be best suited for systems with nonregular energy spacings and for systems with three-spin exchange, , we also performed a nonlinear fit of the DDCI energy-spectra using a bilinear–biquadratic (BLBQ) model. This model is a generalization of the bilinear HDvV Hamiltonian for S = 1 systems ,

ĤBLBQ=−∑i[JBLBQŜi·Ŝi+1+B(Ŝi·Ŝi+1)2]

Mapping DDCI results of 2 onto a BL or BLBQ Hamiltonian, we obtain an intra-nitrene coupling of J′(2)DDCI‑BL = 1092.06 meV and, with combined results of 3 and 4, inter-nitrene couplings of J(3,4)DDCI‑BL = 1.53 ± 0.06 meV and J(3,4)DDCI‑BLBQ = 1.62 ± 0.07 meV for B(3,4)DDCI‑BLBQ = 0.28 ± 0.13 meV.

All employed methods yielded positive values of J and J′, indicating ferromagnetic coupling between all six unpaired spins (septet ground state) for neutral 4 in the gas phase. All J and J′ values for 2, 3 and 4, calculated using different levels of theory and their mapping onto different spin Hamiltonians, are noted in Table S7. The calculated J′ values are in line with experimental intra-nitrene exchange coupling, e.g., about 650–870 meV for aryl nitrenes, and about 1579 meV for NH nitrene. ,

The relatively large intra-nitrene coupling J′, found by all used methods, can be attributed to the strong orbital overlap between the two ferromagnetically aligned spins on a nitrene center. The relatively small inter-nitrene coupling J between individual nitrene centers, found by all used methods to be ferromagnetic, can be understood as resulting from competition between Coulomb-driven ferromagnetic superexchange coupling and classical antiferromagnetic coupling by superexchange mediated through the heptazine core. − The antiferromagnetic component is likely weakened because (i) the in-plane component of the spin density (see Figure S5) cannot couple through the out-of-plane orbitals of the heptazine core, and (ii) the presence of heteroatoms in the heptazine hinders hybridization. Experimentally, ferromagnetic alignment of spins attributed to superexchange has been shown. −

To qualitatively compare the AFM measurements of 4 on NaCl with simulations, we conducted on-surface DFT calculations. For the calculations, we placed 4 on the NaCl surface according to the experimentally determined lateral adsorption position (Figure b), and from this initial geometry relaxed the structures. Because the experiments indicate a negative charge state of 4 on NaCl/Au(111) (Figure a), we allowed 4 to relax in the anionic (4 – ) and dianionic (4 2– ) charge states, considering all possible spin multiplicities for each charge state (see Methods). We performed AFM simulations on the relaxed geometries of all possible spin multiplicities for 4 – and 4 2– using the probe-particle model (see Figure S4 and Methods). , The heptazine core is resolved in all AFM simulations. Our simulations show less brightness on the nitrogen atoms in contrast to the experiment (compare Figures S4 and c,d). This difference might result from not considering charge distributions and electron density distributions of sample and tip in our approach. Using more elaborate full-density-based AFM simulations as proposed by Ellner et al., the contrast differences related to the atomic species might be captured. Furthermore, our simulations show no (repulsive) atomic contrast at the nitrene centers. This could be explained by the nitrene centers being closer to the substrate in the calculation than in the experiment. Important for our assessment, our AFM simulations (Figure S4) show different contrasts and symmetries of the heptazine core for different charge and spin states, which relate to differences in the DFT-calculated adsorption geometries, particularly to the tilt orientation of the heptazine core with respect to the surface.

We find that the AFM simulations of the anionic doublet, i.e., 2 4 – , and the anionic sextet, i.e., 6 4 – , best match the experimental contrast of the heptazine core (see Figures d and c), whereas the simulations for the dianion do not fit the experiment well, suggesting an anionic charge state of 4 on NaCl, in line with the calculated electron affinity of 4. The DFT calculated energies indicate that the sextet is the anionic ground state. Thus, the combined results of calculations and experiment indicate that we experimentally observe 4 as an anionic sextet, i.e., 6 4 – . A top-down view of the relaxed geometry of 6 4 – is shown in Figure e, a side view in Figure f. The nitrene centers are located close to the sodium cations of the NaCl lattice, possibly because of electrostatic attraction between a sodium cation of the NaCl surface and the lone pair of each nitrene center. , The AFM simulation (see Methods) reflects the nonplanarity of the molecule resulting from the adsorption site and orientation on NaCl (Figure d).

Spin-density DFT calculations of 6 4 – in the gas phase (see Figure S5) suggest that the (six) spins on the nitrene centers are aligned ferromagnetically, similar to the septet ground state 7 4 0 , however, in the negative charge state of 4, the additional electron is located at the heptazine core and is antiferromagnetically coupled to the unpaired nitrene electrons, resulting in the anionic sextet 6 4 – .

Conclusions

We have successfully generated mono-, di- and trinitreno-s-heptazine (2, 3, 4) from 2,5,8-triazido-s-heptazine (1) by tip-induced chemistry. By voltage pulses, the precursor’s azide groups were dissociated, generating 2, 3 and 4 on bilayer NaCl on Au(111). Theoretical investigations of neutral 4 using BS-DFT and DDCI indicate a ferromagnetic coupling between all three S = 1 nitrene centers, resulting in a high-spin, septet, ground state, i.e., 7 4 0 . Combined results of theory and AFM experiments indicate a sextet ground state of the anion of 4, i.e. 6 4 –, on bilayer NaCl on Au(111). Our study demonstrates that by tip-induced chemistry multiple nitrene centers can be successively obtained in a molecule, by dissociation of azide moieties, and how coupling between multiple nitrene centers can give rise to high-spin ground states. In future studies, on-surface-synthesized molecules with multiple nitrene centers could be used as building blocks for atomically precise superstructures with localized spin centers and for exploring possible coupling motifs between nitrene-containing molecules. Within a single molecule, the nitrogen–carbon core could be modified for the realization of different exchange couplings between individual nitrene centers.

Methods

Sample Preparation, STM and AFM Methods

The STM (scanning tunneling microscopy) and AFM (atomic force microscopy) measurements were performed in a home-built combined STM/AFM setup , operating at low temperature (T ≈ 5 K) and under ultrahigh vacuum (UHV) conditions (p ≈ 1 × 10–10 mbar). The mode of operation is described in refs and The microscope is equipped with a qPlus sensor operated in frequency-modulation mode and the oscillation amplitude A is kept constant at A = 0.5 Å. The tip is made from a 25 μm diameter PtIr-wire, sharpened ex situ by focused ion beam milling, and in situ by indenting the tip into the bare Au surface. A Au(111) single crystal was kept at 280–290 K while NaCl was evaporated to partially cover the Au(111) substrate with two monolayer (2 ML) thick NaCl(100) islands. 2,5,8-triazido-s-heptazine molecules (1) were placed onto a SiO2-covered Si-wafer in ambient conditions in darkness. Afterward, the wafer was introduced to the UHV chamber and flash-annealed to ∼900 K within a few seconds by resistive heating, sublimating the molecules from the wafer directly onto the cold (T < 15 K) sample in the microscope. In Figure S8, an overview STM image shows the prepared sample. For AFM imaging, a CO molecule was picked up by the tip from bilayer NaCl. , STM images were measured in constant-current mode with a sample voltage V as indicated (V is indicated as sample bias with respect to the tip at virtual ground potential). AFM images were acquired in constant-height mode at V = 0 V. The tip-height offset Δz indicates the offset from the STM controlled setpoint. Positive Δz values correspond to an increase in the tip–sample distance from the setpoint. Setpoint parameters for constant-current STM measurements and for AFM measurements are I = 1 pA, V = 0.2 V, unless indicated otherwise. Measurements of molecules 2, 3, 4 on bilayer NaCl on Au(111) were restricted to currents on the order of about 1 pA, as for larger currents the molecule was displaced on the surface. The restriction to such small current signals precluded resolving spin-excitation features in inelastic tunneling spectroscopy (IETS) measurements.

On-Surface DFT Calculations

Density functional theory (DFT) calculations of 1 and 4 adsorbed on NaCl were performed within AiiDAlab utilizing CP2K 9.1. The PBE functional with the Grimme-D3 dispersion correction was used. The basis set that was used is TZV2P-MOLOPT-GTH. As a substrate, three layers of NaCl(100) were chosen, with the atom positions of the bottom layer being fixed, while the two top layers and the molecule were free to relax. The cell size in the sample plane is 6 × 6 NaCl unit cells with periodic boundary conditions. Planar neutral 1 and the planar anionic 4 were placed 2.7 Å above the topmost NaCl layer at the lateral adsorption position deduced from the experiment (see Figures and S1) and relaxed from that starting geometry. For 4, geometry optimizations were conducted on the NaCl(100) surface with anionic (with S = 1/2, 3/2, 5/2, 7/2), and dianionic (with S = 0, 1, 2, 3, 4) charge states.

Electron Affinity Calculations of Trinitreno-s-Heptazine

The adiabatic electron affinity of 4 was calculated using the fully internally contracted CASPT2 (complete active space second-order perturbation) approach as implemented in ORCA. As a basis set cc-pVTZ (correlation-consistent polarized triple-ζ valence) was chosen. The active space (n,m) (n electrons and m orbitals) was chosen as (6,6) for the neutral septet and (7,6) for the anionic sextet. The gas-phase-optimized DFT geometry (B3LYP/def2-TZVP) of the neutral septet was used as the input geometry.

AFM Probe-Particle Model Simulations

The probe-particle model was used to simulate AFM images with the CO-tip preset with the following parameters: lateral resolution dx = 0.1 Å, oscillation frequency f 0 = 30 kHz, cantilever stiffness 1800 N/m, and oscillation amplitude A = 0.5 Å. The probe has a lateral stiffness of 0.25 N/m and radial stiffness of 30 N/m. Using a tip electrostatics model with dz 2-like charge density, the partial charge on the oxygen atom of the CO probe is −0.1 e.

Broken-Symmetry DFT and Configuration Interaction Calculations

The coupling values between spins on a nitrene spin-center (intra-nitrene coupling J′) and between two distinct nitrene centers (inter-nitrene coupling J) on a single molecule were calculated using broken-symmetry DFT and difference-dedicated configuration interaction (DDCI). All these calculations were carried out using ORCA.

For the broken-symmetry DFT calculations, a geometry optimization of the structures of 2, 3 and 4 has been performed for each high-spin configuration using the B3LYP hybrid functional and def2-TZVP (triple-ζ valence orbitals with polarized functions) basis set. The Resolution of Identity approximation for Coulomb integrals (RI-J), with Chain-of-Sphere integration for Hartree–Fock exchange (COSX) was employed. The spins were then manually flipped on the respective nitrene center and the new electronic configuration was converged to a broken-symmetry solution. Keeping all else fixed, two different hybrid functionals with varying amounts of Hartree–Fock (HF) exchange were used: B3LYP (20% HF exchange) and M06-2X (54% HF exchange). −

With DDCI­(n,m), mononitrene 2 was used to calculate intra-nitrene coupling J′, and 3 and 4 were used to calculate the inter-nitrene coupling J. For each DDCI­(n,m) calculation, a CASSCF­(n,m) calculation with unpaired nitrene electrons in the active space was used as the input. DDCI­(2,2) was used for 2, DDCI­(4,4) for 3, and DDCI­(6,6) for 4. The basis set for the DDCI calculations was cc-pVTZ, and only the low energy spectrum of magnetic excitations was probed for 2 and 3 (one singlet and triplet for 2, one singlet, triplet, and quintet for 3). The full spectrum was calculated for 4 (one singlet, three triplets, two quintets, and one septet).

Supplementary Material

nn5c08710_si_001.pdf (749.1KB, pdf)

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.5c08710.

  • Additional experimental data measured on NaCl­(2 ML)/Au(111), description of the voltage pulses for nitrene generation, DFT and DDCI results and an overview of all calculated exchange coupling values (PDF)

⊥.

Laboratory for X-ray Nanoscience and Technologies, Center for Photon Science, Paul Scherrer Institute, 5232 Villigen, Switzerland

#.

Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences and Humanities, 85748 Garching, Germany.

L.-A.L., A.O. and L.Gross performed the experiments. L.-A.L. performed the DFT, BS-DFT calculations and AFM simulations. L.-A.L. and I.R. performed the CASSCF calculations and the calculation of exchange couplings. I.R. performed the DDCI calculations and programmed the DDCI-fitting routine. M.K. and F.E. synthesized the precursor molecules. I.G. and L.Grill conceived the dissociation experiments. All authors discussed the results. L.-A.L. and L.Gross wrote the manuscript.

This work was financially supported by the H2020-MSCA-ITN ULTIMATE (grant number 813036), the European Research Council Synergy grant MolDAM (grant number 951519), and the European Research Council Advanced Grant AMOS (grant number 101097326).

A preprint of this article has been published on arXiv. Leonard-Alexander Lieske, Aaron H. Oechsle, Igor Rončević, Ilias Gazizullin, Florian Albrecht, Matthias Krinninger, Leonhard Grill, Friedrich Esch, Leo Gross. Tip-induced nitrene generation. 2025, arXiv:2506.04741. arXiv. 10.48550/arXiv.2506.04741 (accessed August 14, 2025).

The authors declare no competing financial interest.

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