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[Donglin Li](https://orcid.org/0009-0001-6866-8715), [Orlando J. Silveira](https://orcid.org/0000-0002-0403-9485), Takuma Matsuda, [Hironobu Hayashi](https://orcid.org/0000-0002-7872-3052), [Hiromitsu Maeda](https://orcid.org/0000-0001-9928-1655), [Adam S. Foster](https://orcid.org/0000-0001-5371-5905), [Shigeki Kawai](https://orcid.org/0000-0003-2128-0120)

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[On‐Surface Synthesis of Triaza[5]triangulene through Cyclodehydrogenation and its Magnetism](https://mdr.nims.go.jp/datasets/6ecd4cf6-dd0c-4d86-8905-a2d92e903068)

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On‐Surface Synthesis of Triaza[5]triangulene through Cyclodehydrogenation and its MagnetismTriangulenesOn-Surface Synthesis of Triaza[5]triangulene throughCyclodehydrogenation and its MagnetismDonglin Li, Orlando J. Silveira, Takuma Matsuda, Hironobu Hayashi, Hiromitsu Maeda,*Adam S. Foster,* and Shigeki Kawai*Abstract: Triangulenes as neutral radicals are becomingpromising candidates for future applications such asspintronics and quantum technologies. To extend thepotential of the advanced materials, it is of importanceto control their electronic and magnetic properties bymultiple graphitic nitrogen doping. Here, we synthesizetriaza[5]triangulene on Au(111) by cyclodehydrogena-tion, and its derivatives by cleaving C� N bonds. Bond-resolved scanning tunneling microscopy and scanningtunneling spectroscopy provided detailed structuralinformation and evidence for open-shell singlet groundstate. The antiferromagnetic arrangement of the spins inpositively doped triaza[5]triangulene was further con-firmed by density function theory calculations. The keyaspect of triangulenes with multiple graphitic nitrogen isthe extra pz electrons composing the π orbitals, favoringcharge transfer to the substrate and changing their low-energy excitations. Our findings pave the way for theexploration of exotic low-dimensional quantum phasesof matter in heteroatom doped organic systems.IntroductionA unique class of open-shell nanographene, the zigzag-edged triangular nanographene, has attracted enormousinterest as a promising candidate in next-generation molec-ular spintronics due to their multiple unpaired π-electronsand intriguing magnetic properties.[1] However, the highreactivity of the zigzag edge leads to a long-standingchallenge to synthesize unsubstituted triangulenes in sol-ution based organic chemistry. In this regard, on-surfacesynthesis[2] has become a powerful strategy to fabricatetriangulenes under ultra-high vacuum conditions becausesuch reactive carbon-based structures can be obtained fromdesigner precursors. So far, a series of triangulenes havebeen synthesized on surfaces by both tip-inducedmanipulation[3] and annealing of precursors.[4] The previousstudies demonstrated that the total net spin of trianguleneand its higher homologues (N�3, where N is the number ofcarbon atoms on each zigzag edge) linearly increases withtheir size N (Scheme 1a). However, even using the on-surface synthesis strategy, extended triangulenes (N >7)with higher polyradicals poses significant challenges in termsof the solubility of the precursors and the thermal stabilityduring sublimation. It has been demonstrated that heter-[*] Dr. D. Li, Dr. H. Hayashi, Prof. Dr. S. KawaiCenter for Basic Research on MaterialsNational Institute for Materials ScienceTsukuba 305-0047 (Japan)E-mail: KAWAI.Shigeki@nims.go.jpDr. O. J. Silveira, Prof. Dr. A. S. FosterDepartment of Applied PhysicsAalto UniversityP.O. Box 11100, Aalto, Espoo 00076 (Finland)E-mail: adam.foster@aalto.fiT. Matsuda, Prof. Dr. H. MaedaDepartment of Applied Chemistry, College of Life SciencesRitsumeikan UniversityKusatsu 525-8577 (Japan)E-mail: maedahir@ph.ritsumei.ac.jpProf. Dr. A. S. FosterNano Life Science Institute (WPI-NanoLSI)Kanazawa UniversityKanazawa 920-1192 (Japan)Prof. Dr. S. KawaiGraduate School of Pure and Applied Sciences,University of TsukubaTsukuba 305-8571 (Japan)© 2024 The Authors. Angewandte Chemie International Editionpublished by Wiley-VCH GmbH. This is an open access article underthe terms of the Creative Commons Attribution License, whichpermits use, distribution and reproduction in any medium, providedthe original work is properly cited.Scheme 1. Chemical structures of open-shell triangulenes and synthesisstrategy for azatriangulenes and nitrogen-doped nanographene. (a)Triangulenes with different numbers of zigzag carbon atoms (N) andpredicted spin multiplicity (S), having a linear relationship between Sand N. (b) Chemical structures of 4,8,12-Tris(2,6-dimethylphenyl)-4,8,12-triazatriangulenium+ -Cl� (1) as a precursor ion pair and triaza-[5]triangulene (2), nitrogen-doped nanographene (3), and triaza-[3]triangulene (4) as products. C� N bonds indicated by red lines in 1can be broken during cyclodehydrogenation. The N� H bonds in 3 and4 are omitted for simplicity.AngewandteChemieResearch Articlewww.angewandte.orgHow to cite: Angew. Chem. Int. Ed. 2024, 63, e202411893doi.org/10.1002/anie.202411893Angew. Chem. Int. Ed. 2024, 63, e202411893 (1 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbHhttp://orcid.org/0009-0001-6866-8715http://orcid.org/0000-0002-0403-9485http://orcid.org/0000-0002-7872-3052http://orcid.org/0000-0001-9928-1655http://orcid.org/0000-0001-5371-5905http://orcid.org/0000-0003-2128-0120https://doi.org/10.1002/anie.202411893oatom doping of graphene-based structures allows furthertuning of their electronic and magnetic properties.[5] Forinstance, introducing a nitrogen atom into the triangulenestructure is an alternative approach to obtain a higherpolyradical, consequently inducing an additional π-electronto the triangulene due to the double occupancy of thenitrogen’s pz orbital.[5d,6] The introduction of more nitrogenatoms into the same sublattice sites increases the imbalanceof the π-electrons, which in a controlled scenario can beused as a tool to tailor the magnetism that arises from thetopological frustrations.Here, we successfully synthesized triaza[5]triangulene(2), a version of the N=5 triangulene with three graphiticnitrogen atoms, in which the spin and orbital degeneracycoexist, driving the molecule to a valley-mixing phase in itsneutral phase. We synthesized 2 from 4,8,12-Tris(2,6-dimeth-ylphenyl)-4,8,12-triazatriangulenium+-Cl� (1) as a precursorion pair by cyclodehydrogenation on the Au(111) surface(Scheme 1b). Surprisingly, C� N bonds in 1 were also brokenduring the annealing process, resulting in the additionalformation of N-doped trapezoidal nanographene (3) andtriaza[3]triangulene (4), in which pyridinic nitrogen atomsexist. A combination of bond-resolved scanning tunnelingmicroscopy (BR-STM) with a carbon monoxide (CO)terminated tip[7] and scanning tunneling spectroscopy (STS)revealed that all three products exhibit an open-shell singletground state on Au(111). Our density function theory(DFT) calculations show an S=1/2 state in gas-phase neutral2 and 3, suggesting that the open shell-singlet is aconsequence of charge transfer between molecule andsubstrate. This is consistent with cationic versions of 2 and 3with antiferromagnetic (AF) alignment. Hence, the excita-tion of two exchange coupled spins by tunneling electrons isthe reason for the symmetric steps around the Fermi levelobserved in the STS, where the magnetic exchange coupling(MEC) strengths in 2, 3, and 4 are 9, 10.6, and 31 meV,respectively. Our finding validates the influence of multiplegraphitic nitrogen doping on high-spin nanographene.Results and DiscussionThe precursor 1 was synthesized via solution chemistry (seeSupporting Information for detailed synthetic procedures).To obtain triaza[5]triangulene, several different preparationparameters were tested. For example, 1 was either depositedon Au(111) kept at room temperature followed by annealingthe sample to 300 °C or deposited on Au(111) kept atelevated temperatures (300–400 °C). We found that increas-ing the substrate temperature increased the reaction yield oftriaza[5]triangulene. The products were finally obtained bydepositing 1 on Au(111) kept at 380 °C (Figure S1) andsubsequently were characterized with STM at 4.3 K. Weobserved three kinds of isolated products as indicated bysquares in red, blue, and green (Figure 1a), with yields of5%, 13%, and 3%, respectively (Figure S2). The close-upview of the STM topography in the area indicated by the redsquare shows the product as an equilateral triangular shapewith a side length of approximately 1.4 nm (Figure 1b). Boththe shape and side length are consistent with those oftriaza[5]triangulene. Next, the close-up view of the STMtopography in the area indicated by the blue square showsan isosceles trapezoid shaped molecule (Figure 1c). Thelength of the longer side was approximately 1.4 nm, which isalmost identical to the side length of 2. Therefore, wetentatively identify this molecule as a broken triaza-Figure 1. On-surface syntheses of 2–4. (a) Large-scale STM image of the sample prepared by depositing precursor 1 on Au(111) kept at 380 °C. (b–d) Close-up views of 2, 3, and 4, respectively. (e,h,k) BR-STM images over the structure in (b–d), (f,i,l) the corresponding Laplace filtered images,and (g, j, m) the chemical structures superimposed on the corresponding Laplace filtered images. Measurement parameters: sample bias voltageV=200 mV and tunneling current I=10 pA in (a). V=200 mV and I=10 pA in (b). V=200 mV and I=2 pA in (c). V=100 mV and I=10 pA in (d).AngewandteChemieResearch ArticleAngew. Chem. Int. Ed. 2024, 63, e202411893 (2 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 45, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202411893 by National Institute For, Wiley Online Library on [28/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttps://onlinelibrary.wiley.com/action/rightsLink?doi=10.1002%2Fanie.202411893&mode=[5]triangulene, which is formed by accidental cleavage ofone C� N bond during the cyclodehydrogenation process.Additionally, we observed a molecule with a smaller equi-lateral triangular shape as indicated by the green square(Figure 1d). The side length is approximately 0.9 nm, whichis smaller than that of triaza[5]triangulene (Figure 1b). Thismolecule is likely triaza[3]triangulene, formed by dissociat-ing all dimethylphenyl groups during the cyclodehydrogena-tion. The constant-height BR-STM image (Figure 1e) of thelarger triangular molecule and the corresponding Laplacefiltered image (Figure 1f) reveal the skeletal structure.However, the left corner part was still unclear. By settingthe tip closer to the surface by 21 pm, the hexagonal ringappeared at the corner (Figure S3), meaning that themolecule was composed of 15 fused six-membered rings.Thus, the larger triangular molecule corresponds to 2. Theneutral form of 2 was tentatively depicted in Figure 1g,which helped to identify the number of its π-electrons as 49.We found significant variations of the contrasts at the edgesof 2 in the BR-STM image. The bright contrast around theedge should relate to the spin polarization.[8] Note that nosignificant feature relating to the CH2 termination caused byimperfect cyclodehydrogenation was observed.[9] The BR-STM image (Figure 1h) of the trapezoidal molecule and thecorresponding Laplace-filtered image (Figure 1i) show 12fused six-membered rings in the molecule. Thus, the productwas synthesized via cyclodehydrogenation among two 2,6-dimethylphenyl groups and the triaza[3]triangulene corewhile the last phenyl group was simply dissociated, that is 3(Figure 1j). After this dissociation, the N atom at the edgewas passivated by an H atom, as demonstrated by themanipulation experiment (Figure S4). The BR-STM image(Figure 1k) of the smaller triangular molecule and thecorresponding Laplace filtered image (Figure 1l) show threebenzene rings and a darker region at the center. Due to thehigh mobility of this small molecule, it was challenging toobtain a higher resolution image. Inspired by the formationof 3, this smaller molecule could correspond to 4, which wassynthesized via dissociation of three 2,6-dimethylphenylgroups in 1 (Figure 1m). This compound deviates from ourmain focus due to the absence of the graphitic nitrogendoping. Moreover, substituting CH groups at zigzag edgeswith N atoms can retain the electronic properties of themolecule because the nitrogen atom maintains the π-systemtopology equivalent to that of the substituted CH group.[10]Additionally, the contribution of such pyridinic nitrogen tothe modulation of the magnetic property is considerablyless.[11] Therefore, we focus on the products with graphiticnitrogen atoms, 2 and 3. Apart from the isolated products, anumber of dimers and trimers as well as oligomers of 2–4were also formed because the highly reactive edges of open-shell molecules tend to be stabilized by fusing with eachother at elevated temperatures.[12] In a fused productcomposed of one 3 and two 4 molecules, 4 was bound to thelonger side of 3 (Figure S5). The reactivity of the longer sideis most probably higher than that of the shorter one due tothe localized spins. Note that we found absence of theproduct synthesized by dissociating two 2,6-dimethylphenylgroups from 1, most probably relating to the low cleavagebarrier of the last C� N bond.Ovchinnikov’s rule[13] and Lieb’s theorem[14] are com-monly employed to estimate the spin state of[N]triangulenes.[15] However, we found that the products donot follow the Ovchinnikov-Lieb rules since the system doesnot obey half-filling, complicating the prediction of theirground state. We investigated magnetic properties of 2 and3 by acquiring low energy dI/dV spectra (Figure 2). Both dI/dV curves (middle panels in Figure 2) show dip features atthe zero bias surrounded by two symmetric steps, which areattributed to excitation by tunneling electrons of spinslocalized at different sites in molecules.[16] This is consistentwith the distinct contrasts observed by BR-STM as shown inFigure 1, where brighter spots are observed at the cornerand edge of 2 and at the larger edge of 3. Assuming thespins are concentrated over these brighter areas, thetunneling electrons can inelastically flip the spins through aresonance process when the energy is equivalent to theexchange coupling between the spins.[17] We assume that thepz electrons modified by the nitrogen atom doping inducespin alignment in the system and act as apparent sublatticeslocalized at the bright spots in Figure 1. The absence ofKondo resonance at the zero bias in the dI/dV curvesindicates a spin-flipping transition from open-shell singletstates to triplets, which is similar to an AF to ferromagnetic(FM) transition.[18] Since 2 and 3 with the geometriesproposed here contain odd numbers of electrons, only acharge transfer mechanism between the products and theunderlying gold substrate could influence their spin multi-plicity in a way that allows such spin states.[5d] Electrondonation to gold surfaces is expected in nitrogen-functional-ized systems due to the misalignment of their Fermi levelwith the vacuum.[19] The corresponding inelastic electrontunneling spectroscopy (IETS) spectrum of 2 shows that theMEC between spins is ~9 meV while that of 3 shows asimilar MEC of 10.6 meV (right panels in Figure 2). Notethat 4 has an MEC energy of 31 meV (Figure S6), which isFigure 2. Characterization of the magnetic properties of 2 and 3. (a, b)dI/dV and IETS spectra were taken at the sites marked by red dots inthe left panel in a and b, respectively. Vac=5 mV. The dI/dV curves inblack were taken over the bare Au(111) surface.AngewandteChemieResearch ArticleAngew. Chem. Int. Ed. 2024, 63, e202411893 (3 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 45, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202411893 by National Institute For, Wiley Online Library on [28/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttps://onlinelibrary.wiley.com/action/rightsLink?doi=10.1002%2Fanie.202411893&mode=relatively large for [3]triangulene-based structures.[20] Wealso measured the fused trimer composed of one 3 and two4 molecules and the measured MEC energy (9.6 mV) overthe 4 unit in the fused molecule was smaller than that of theisolated 4 (Figure S5). The strong spin coupling betweenmulti spin units significantly reduces the energy differencebetween the ground state and the excited state of 4.To get an insight into the spin state of the products andto elucidate the charge transfer mechanism, we investigatedtheir frontier orbitals using STS measurements. The dI/dVspectra taken at three different sites of 2 have severalelectronic resonances at 0.9, � 0.9, and � 1.3 V as well as adip feature around the Fermi level (Figure 3a). We foundthat the contrasts in the constant current dI/dV maps at thecorresponding energies are C2 symmetric rather than C3symmetric (Figure 3b). The spatial distributions of the dI/dVmaps measured at � 0.9 and 0.9 V concentrated along theedges, with the number of bright lobes matching those in thesimulated maps at � 1.2 and 0.9 V, respectively (Figure 3c).Thus, the energies relate to the DFT frontier orbitals ψ4 andψ3 in Figure 3d.[5d] Here, we selected the energies of thesimulated images to get a best agreement with the measureddI/dV maps. The simulated dI/dV maps (Figure S7) over awider energy range reveal significant broadening of thecorresponding orbitals (Figure 3e). The orbitals ψ2 and ψ3have similar distributions as the dI/dV images measured at� 0.7 to � 1.1 V have similar contrasts (Figure S8). We alsofound that the dI/dV image at � 1.3 V (Figure 3b) is inagreement with the simulated dI/dV map at � 1.8 V,corresponding to the ψ1 orbital. It should be noted that theslight deviation of the energies would relate to the hybrid-ization of the molecular orbitals with the substrate. Theenergy levels in Figure 3e reveal the open-shell character-istic of 2+, where the low energy spin orbitals aredegenerated but spatially separated (for example, both spinorbitals of ψ1 are at the same energy (Figure 3e) but arelocated at opposite sides of 2+ (Figure 3d)). Note thatcharging the molecule leaves the ψ4 orbital unoccupied,breaking the orbital-degeneracy observed in neutral 2. ThedI/dV maps of 3 and 4 were also measured at differentenergies (Figures S9,S10). We found that 4 was highlymobile at negative sample bias voltages (Figure S11).In contrast to [5]triangulene[4b] (Figure 4a) and singlydoped aza[5]triangulene[6b] (Figure 4b), the three extraelectrons in 2 populate degenerated levels, leading to Jahn–Teller distortions and a valley-mixing of the highestoccupied molecular orbital in an S=1/2 ground state (Fig-ure 4c). This is similar to earlier results for the smalleraza[3]triangulene.[5d] For 2, enforcing C3 symmetry as seen inFigure 4d leads the wave function to vanish completely atthe central atoms.[21] If this restriction is removed, thedistance maps reveal that the Jahn–Teller distortion isobserved around the nitrogen atoms (Figure 4e), andcharging the system does not induce the C3 symmetry(Figure 4f). The distortion also causes a distribution of thewave function over the central atoms, where 2 is then drivento an AF phase as one electron is transferred to the surfacewhile retaining a Jahn–Teller distortion compatible to thecharged system, thus leading to the C2 symmetry of the dI/dV maps. We noticed that fixing a triplet ground state inFigure 3. (a) Long-range dI/dV spectra taken at the sites of 2 marked by green, red, and blue dots in the inset. The curve in black was taken at thebar Au for a reference. Vac=10 mV. (b) Constant-current dI/dV maps of 2 taken at � 1.3, � 0.9, and 0.9 V with a metal tip, which was obtained bycontacting to a clean gold substrate. (c) DFT simulated constant height dI/dV maps of 2+ that best agree with the resonances observed in theexperiment. (d) Spatial distribution of the wave functions of 2+ , where the ψ4 wave function in blue is the orbital that becomes unoccupied whenthe system is positively charged. (e) Energy levels of 2+ and its spin density in the inset.AngewandteChemieResearch ArticleAngew. Chem. Int. Ed. 2024, 63, e202411893 (4 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 45, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202411893 by National Institute For, Wiley Online Library on [28/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttps://onlinelibrary.wiley.com/action/rightsLink?doi=10.1002%2Fanie.202411893&mode=cationic 2+ and 3+ brings the systems to an FM phase,increasing their total energies by 0.9 and 5.2 meV, respec-tively.ConclusionWe demonstrated the synthesis of triaza[5]triangulene andits derivatives via cyclodehydrogenation of triaza-precursorion pair. BR-STM revealed their chemical structures whiletheir open-shell singlet ground states were investigated witha combination of STS and DFT calculations. The additionalπ-electrons introduced by the graphitic nitrogen atoms andthe charge transfer between the molecules and the substrateled to an AF alignment. We found that the azatrianguleneshave a relatively high magnetic exchanging couplingstrength, which is an important parameter for spin-logicoperations at practical temperatures. Our results provideelementary building blocks to explore quantum magnetismand a strategy for the bottom-up synthesis of high-spinquantum nanostructures for future spintronic devices.AcknowledgementsThis work was supported by in part by Japan Society for thePromotion of Science (JSPS) KAKENHI Grant NumberJP22H00285, JP22H02067, JP20H05863, and JP24K01576.The authors acknowledge funding from the Academy ofFinland (project no. 346824). A.S.F. was supported by theWorld Premier International Research Center Initiative(WPI), MEXT, Japan. The authors acknowledge thecomputational resources provided by the Aalto Science-ITproject and CSC, Helsinki.Conflict of InterestThe authors declare no conflict of interest.Data Availability StatementThe data that support the findings of this study are availablefrom the corresponding author upon reasonable request.Keywords: on-surface synthesis · triangulene · graphiticnitrogen · scanning tunneling microscopy/spectroscopy ·density functional theory[1] a) W. Han, R. K. Kawakami, M. Gmitra, J. Fabian, Nat.Nanotechnol. 2014, 9, 794–807; b) Y. Morita, S. Suzuki, K.Sato, T. Takui, Nat. Chem. 2011, 3, 197–204; c) W. L. Wang,O. V. Yazyev, S. Meng, E. Kaxiras, Phys. Rev. Lett. 2009, 102,157201.[2] a) J. Cai, C. A. Pignedoli, L. Talirz, P. Ruffieux, H. Söde, L.Liang, V. Meunier, R. Berger, R. Li, X. Feng, Nat. Nano-technol. 2014, 9, 896–900; b) J. Cai, P. Ruffieux, R. Jaafar, M.Bieri, T. Braun, S. Blankenburg, M. Muoth, A. P. Seitsonen,M. Saleh, X. Feng, Nature 2010, 466, 470–473; c) Y.-C. Chen, T.Cao, C. Chen, Z. Pedramrazi, D. Haberer, D. G. De Oteyza,F. R. Fischer, S. G. Louie, M. F. Crommie, Nat. Nanotechnol.2015, 10, 156–160; d) P. Ruffieux, S. Wang, B. Yang, C.Sánchez-Sánchez, J. Liu, T. Dienel, L. Talirz, P. Shinde, C. A.Pignedoli, D. Passerone, Nature 2016, 531, 489–492.[3] a) N. Pavlicek, A. Mistry, Z. Majzik, N. Moll, G. Meyer, D. J.Fox, L. Gross, Nat. Nanotechnol. 2017, 12, 308–311; b) J. Su, J.Li, N. Guo, X. Peng, J. Yin, J. Wang, P. Lyu, Z. Luo, K.Mouthaan, J. Wu, C. Zhang, X. Wang, J. Lu, Nat. Synth. 2024,3, 466–476 .[4] a) S. Mishra, D. Beyer, K. Eimre, J. Liu, R. Berger, O.Groning, C. A. Pignedoli, K. Mullen, R. Fasel, X. Feng, P.Ruffieux, J. Am. Chem. Soc. 2019, 141, 10621–10625; b) J. Su,M. Telychko, P. Hu, G. Macam, P. Mutombo, H. Zhang, Y.Bao, F. Cheng, Z. Huang, Z. Qiu, S. J. R. Tan, H. Lin, P.Jelínek, F. Chuang, J. Wu, J. Lu, Sci. Adv. 2019, 5, eaav7717.[5] a) E. Carbonell-Sanromà, J. Hieulle, M. Vilas-Varela, P.Brandimarte, M. Iraola, A. Barragán, J. Li, M. Abadia, M.Corso, D. Sánchez-Portal, ACS Nano 2017, 11, 7355–7361;b) S. Kawai, S. Nakatsuka, T. Hatakeyama, R. Pawlak, T.Meier, J. Tracey, E. Meyer, A. S. Foster, Sci. Adv. 2018, 4,eaar7181; c) K. Nakamura, Q.-Q. Li, O. Krejci, A. S. Foster, K.Sun, S. Kawai, S. Ito, J. Am. Chem. Soc. 2020, 142, 11363–11369; d) T. Wang, A. Berdonces-Layunta, N. Friedrich, M.Vilas-Varela, J. P. Calupitan, J. I. Pascual, D. Peña, D.Casanova, M. Corso, D. G. de Oteyza, J. Am. Chem. Soc. 2022,144, 4522–4529; e) X. Wang, J. I. Urgel, G. B. Barin, K. Eimre,M. Di Giovannantonio, A. Milani, M. Tommasini, C. A.Pignedoli, P. Ruffieux, X. Feng, J. Am. Chem. Soc. 2018, 140,9104–9107; f) X. Wang, X. Yao, A. Narita, K. Müllen, Acc.Chem. Res. 2019, 52, 2491–2505; g) K. Sun, O. J. Silveira, S.Saito, K. Sagisaka, S. Yamaguchi, A. S. Foster, S. Kawai, ACSNano 2022, 16, 11244–11250.[6] a) J. Lawrence, Y. He, H. Wei, J. Su, S. Song, A. W. Rodrigues,D. Miravet, P. Hawrylak, J. Zhao, J. Wu, J. Lu, ACS Nano2023, 17, 20237–20245; b) M. Vilas-Varela, F. Romero-Lara, A.Vegliante, J. P. Calupitan, A. Martínez, L. Meyer, U. Uriarte-Amiano, N. Friedrich, D. Wang, F. Schulz, N. E. Koval, M. E.Sandoval-Salinas, D. Casanova, M. Corso, E. Artacho, D.Figure 4. (a–c) Evolution of the low energy levels among [5]triangulene,aza[5]triangulene, and 2 (triaza[5]triangulene). The Insets show thespin density of each case. (d–f) Distance maps of 2 in three differentscenarios: in (d) the C3 symmetry is kept intact while in (e) and (f) theJahn–Teller distortion is clearly seen around the nitrogen atoms for theneutral and cationic 2, respectively.AngewandteChemieResearch ArticleAngew. Chem. Int. Ed. 2024, 63, e202411893 (5 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 45, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202411893 by National Institute For, Wiley Online Library on [28/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttps://doi.org/10.1038/nnano.2014.214https://doi.org/10.1038/nnano.2014.214https://doi.org/10.1038/nchem.985https://doi.org/10.1038/nnano.2014.184https://doi.org/10.1038/nnano.2014.184https://doi.org/10.1038/nature09211https://doi.org/10.1038/nnano.2014.307https://doi.org/10.1038/nnano.2014.307https://doi.org/10.1038/nature17151https://doi.org/10.1038/s44160-024-00488-7https://doi.org/10.1038/s44160-024-00488-7https://doi.org/10.1021/jacs.9b05319https://doi.org/10.1021/acsnano.7b03522https://doi.org/10.1021/jacs.0c02534https://doi.org/10.1021/jacs.0c02534https://doi.org/10.1021/jacs.1c12618https://doi.org/10.1021/jacs.1c12618https://doi.org/10.1021/jacs.8b06210https://doi.org/10.1021/jacs.8b06210https://doi.org/10.1021/acs.accounts.9b00322https://doi.org/10.1021/acs.accounts.9b00322https://doi.org/10.1021/acsnano.2c04563https://doi.org/10.1021/acsnano.2c04563https://doi.org/10.1021/acsnano.3c05974https://doi.org/10.1021/acsnano.3c05974https://onlinelibrary.wiley.com/action/rightsLink?doi=10.1002%2Fanie.202411893&mode=Peña, J. I. Pascual, Angew. Chem. Int. Ed. 2023, 62,e202307884.[7] a) L. Gross, F. Mohn, N. Moll, P. Liljeroth, G. Meyer, Science2009, 325, 1110–1114; b) R. Temirov, S. Soubatch, O. Neuche-va, A. C. Lassise, F. S. Tautz, New J. Phys. 2008, 10, 053012.[8] a) J. Li, S. Sanz, J. Castro-Esteban, M. Vilas-Varela, N.Friedrich, T. Frederiksen, D. Pena, J. I. Pascual, Phys. Rev.Lett. 2020, 124, 177201; b) J. Li, S. Sanz, M. Corso, D. J. Choi,D. Pena, T. Frederiksen, J. I. Pascual, Nat. Commun. 2019, 10,200.[9] a) N. Pavliček, A. Mistry, Z. Majzik, N. Moll, G. Meyer, D. J.Fox, L. Gross, Nat. Nanotechnol. 2017, 12, 308–311; b) S.Mishra, S. Fatayer, S. Fernández, K. Kaiser, D. Peña, L. Gross,ACS Nano 2022, 16, 3264–3271.[10] K. Eimre, J. I. Urgel, H. Hayashi, M. D. Giovannantonio, P.Ruffieux, S. Sato, S. Otomo, Y. Chan, N. Aratani, D. Passer-one, O. Gröning, H. Yamada, R. Fasel, C. A. Pignedoli, Nat.Commun. 2022, 13, 511.[11] P. Lazar, R. Mach, M. Otyepka, J. Phys. Chem. C 2019, 123,10695–10702.[12] T. Stuyver, B. Chen, T. Zeng, P. Geerlings, F. De Proft, R.Hoffmann, Chem. Rev. 2019, 119, 11291–11351.[13] A. Ovchinnikov, Theor. Chim. Acta 1978, 47, 297–304.[14] E. H. Lieb, Phys. Rev. Lett. 1989, 62, 1201.[15] J. Su, M. Telychko, S. Song, J. Lu, Angew. Chem. Int. Ed. 2020,59, 7658–7668.[16] M. A. Reed,Mater. Today 2008, 11, 46–50.[17] a) Y. Zheng, C. Li, C. Xu, D. Beyer, X. Yue, Y. Zhao, G.Wang, D. Guan, Y. Li, H. Zheng, Nat. Commun. 2020, 11,6076; b) S. Mishra, X. Yao, Q. Chen, K. Eimre, O. Gröning, R.Ortiz, M. Di Giovannantonio, J. C. Sancho-García, J. Fernán-dez-Rossier, C. A. Pignedoli, Nat. Chem. 2021, 13, 581–586;c) Y. Zheng, C. Li, Y. Zhao, D. Beyer, G. Wang, C. Xu, X.Yue, Y. Chen, D. Guan, Y. Li, Phys. Rev. Lett. 2020, 124,147206.[18] T. Wang, S. Sanz, J. Castro-Esteban, J. Lawrence, A.Berdonces-Layunta, M. S. G. Mohammed, M. Vilas-Varela, M.Corso, D. Pena, T. Frederiksen, D. G. de Oteyza, Nano Lett.2022, 22, 164–171.[19] E. C. H. Wen, P. H. Jacobse, J. Jiang, Z. Wang, R. D.McCurdy, S. G. Louie, M. F. Crommie, F. R. Fischer, J. Am.Chem. Soc. 2022, 144, 13696–13703.[20] a) S. Mishra, D. Beyer, K. Eimre, R. Ortiz, J. Fernández-Rossier, R. Berger, O. Gröning, C. A. Pignedoli, R. Fasel, X.Feng, Angew. Chem. Int. Ed. 2020, 132, 12139–12145; b) S.Mishra, D. Beyer, K. Eimre, S. Kezilebieke, R. Berger, O.Gröning, C. A. Pignedoli, K. Müllen, P. Liljeroth, P. Ruffieux,Nat. Nanotechnol. 2020, 15, 22–28.[21] J. C. G. Henriques, D. Jacob, A. Molina-Sánchez, G. Catarina,A. T. Costa, J. Fernández-Rossier, arXiv preprint 2023,arXiv:2312.04938.Manuscript received: June 25, 2024Accepted manuscript online: July 22, 2024Version of record online: September 10, 2024AngewandteChemieResearch ArticleAngew. Chem. Int. Ed. 2024, 63, e202411893 (6 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 45, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202411893 by National Institute For, Wiley Online Library on [28/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttps://doi.org/10.1126/science.1176210https://doi.org/10.1126/science.1176210https://doi.org/10.1088/1367-2630/10/5/053012https://doi.org/10.1021/acsnano.1c11157https://doi.org/10.1021/acs.jpcc.9b02163https://doi.org/10.1021/acs.jpcc.9b02163https://doi.org/10.1021/acs.chemrev.9b00260https://doi.org/10.1007/BF00549259https://doi.org/10.1103/PhysRevLett.62.1201https://doi.org/10.1002/anie.201913783https://doi.org/10.1002/anie.201913783https://doi.org/10.1016/S1369-7021(08)70238-4https://doi.org/10.1038/s41557-021-00678-2https://doi.org/10.1021/acs.nanolett.1c03578https://doi.org/10.1021/acs.nanolett.1c03578https://doi.org/10.1021/jacs.2c04432https://doi.org/10.1021/jacs.2c04432https://doi.org/10.1002/ange.202002687https://doi.org/10.1038/s41565-019-0577-9https://onlinelibrary.wiley.com/action/rightsLink?doi=10.1002%2Fanie.202411893&mode= On-Surface Synthesis of Triaza[5]triangulene through Cyclodehydrogenation and its Magnetism Introduction Results and Discussion Conclusion Acknowledgements Conflict of Interest Data Availability Statement