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[Kewei Sun](https://orcid.org/0000-0002-1835-243X), Donglin Li, Takahito Kaihara, Satoshi Minakata, Youhei Takeda, [Shigeki Kawai](https://orcid.org/0000-0003-2128-0120)

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[On-surface synthesis of nitrogen-doped nanographene with an [18]annulene pore on Ag(111)](https://mdr.nims.go.jp/datasets/7f6d58cf-624f-4d58-a162-4d3583e2d576)

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On-surface synthesis of nitrogen-doped nanographene with an [18]annulene pore on Ag(111)ARTICLEOn-surface synthesis of nitrogen-dopednanographene with an [18]annulene poreon Ag(111)Kewei Sun 1, Donglin Li2, Takahito Kaihara3, Satoshi Minakata 3, Youhei Takeda 3✉ &Shigeki Kawai 2,4✉On-surface synthesis is of importance to fabricate low dimensional carbon-based nanoma-terials with atomic precision. Here, we synthesize nitrogen-doped nanographene with an [18]annulene pore and its dimer through sequential reactions of debromination, aryl–aryl cou-pling, cyclodehydrogenation and C–N coupling on Ag(111) from 3,12-dibromo-7,8-diaza[5]helicene. The inner structures of the products were characterized with scanning tunnelingmicroscopy with a CO terminated tip at low temperature. Furthermore, the first four unoc-cupied electronic states of the nanographene were investigated with a combination ofscanning tunneling spectroscopy and theoretical calculations. Except for the LUMO+ 2 stateobserved at +1.3 V, the electronic states at 500mV, 750mV and 1.9 V were attributed to thesuperatom molecular orbitals at the [18]annulene pore, which were significantly shiftedtowards the Fermi level due to the hybridization with the confined surface state.https://doi.org/10.1038/s42004-023-01023-z OPEN1 International Center for Young Scientists, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan. 2 Center for BasicResearch on Materials, National Institute for Materials Science, 1-2-1 Segen, Tsukuba, Ibaraki 305-0047, Japan. 3 Department of Applied Chemistry,Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan. 4 Graduate School of Pure and Applied Sciences, Universityof Tsukuba, Tsukuba 305-8571, Japan. ✉email: takeda@chem.eng.osaka-u.ac.jp; KAWAI.Shigeki@nims.go.jpCOMMUNICATIONS CHEMISTRY |           (2023) 6:228 | https://doi.org/10.1038/s42004-023-01023-z | www.nature.com/commschem 11234567890():,;http://crossmark.crossref.org/dialog/?doi=10.1038/s42004-023-01023-z&domain=pdfhttp://crossmark.crossref.org/dialog/?doi=10.1038/s42004-023-01023-z&domain=pdfhttp://crossmark.crossref.org/dialog/?doi=10.1038/s42004-023-01023-z&domain=pdfhttp://crossmark.crossref.org/dialog/?doi=10.1038/s42004-023-01023-z&domain=pdfhttp://orcid.org/0000-0002-1835-243Xhttp://orcid.org/0000-0002-1835-243Xhttp://orcid.org/0000-0002-1835-243Xhttp://orcid.org/0000-0002-1835-243Xhttp://orcid.org/0000-0002-1835-243Xhttp://orcid.org/0000-0001-9619-445Xhttp://orcid.org/0000-0001-9619-445Xhttp://orcid.org/0000-0001-9619-445Xhttp://orcid.org/0000-0001-9619-445Xhttp://orcid.org/0000-0001-9619-445Xhttp://orcid.org/0000-0001-9103-4238http://orcid.org/0000-0001-9103-4238http://orcid.org/0000-0001-9103-4238http://orcid.org/0000-0001-9103-4238http://orcid.org/0000-0001-9103-4238http://orcid.org/0000-0003-2128-0120http://orcid.org/0000-0003-2128-0120http://orcid.org/0000-0003-2128-0120http://orcid.org/0000-0003-2128-0120http://orcid.org/0000-0003-2128-0120mailto:takeda@chem.eng.osaka-u.ac.jpmailto:KAWAI.Shigeki@nims.go.jpwww.nature.com/commschemwww.nature.com/commschemNanographenes (NGs) can be regarded as representativezero-dimensional graphene derivatives and have attractedsignificant attention from researchers in recent years. Thenanomaterials are promising candidates for forthcoming carbon-based nanoelectronics1, spintronics2, solar cells3, and gasstorages4 because their electronic, optical and magnetic propertiescan be tuned by edge topologies and sizes5–8 as well as heteroa-tom substitutions9. Specifically, engineering band gaps of NGswould lead to various applications such as photovoltaic system10and light-emitting diode (LED)11. On-surface synthesis as abottom-up approach became a powerful method to obtainthese nanocarbon materials because of the high-controllability ofthe structure down to atomic scale12,13. The small moleculessynthesized in wet chemistry are usually sublimated onmetal surfaces, and subsequently annealed to activate thereaction. Through homo-14–18 and hetero-coupling19–22 anddehydration23 of molecules, desired products are obtained. Thismethod is free from the solubility issue, which often limits thetype of reactants in wet chemistry8,24. Adsorption to the metalsubstrate also lowers the activation barrier of cyclodehy-drogenation for planarization25–27, which usually requiresharsh conditions in wet chemistry. In the last decade, the on-surface synthesis has been successfully developed to fabricatecarbon-based low dimensional nanostructures with atomic pre-cision such as graphene nanoribbons25,28–36 and covalentorganic frameworks22,23,37,38. Besides one- and two-dimensionalnanocarbons, NGs with various edge shapes and sizeshave also been obtained by dehalogenative coupling orcyclodehydrogenation26,27,39–42. For instance, NGs with sub-nanoscale pores43–47 and with heteroatom substitutions48–51 weresuccessfully synthesized. However, on-surface synthesis of NGs,having both the pore and the heteroatom substitution, is stillscarce.Here, we employ 3,12-dibromo-7,8-diaza[5]helicene (DBDH, 1)molecule52 as a precursor to synthesize nitrogen-doped NG and itsdimer with sub-nanoscale pores on Ag(111). Triangular organo-metallic compounds composed of three molecular units are firstsynthesized via dehalogenative homo-coupling by annealing at100 °C. Higher temperature annealing at 150 °C induces the clea-vage of C–Ag bonds and the subsequent formation of the C–Cbonds between the units. Finally, the nitrogen-doped NG with an[18]annulene pore is obtained via the planarization throughcyclodehydrogenation at 250 °C. Further annealing at 300 °C leadsto the formation of the dimer by C–N coupling. Scanning tunnelingmicroscopy (STM) with a CO-terminated tip reveals the structuresof the products. We also measure the first four lowest unoccupiedmolecular orbital (LUMO) states with scanning tunneling spec-troscopy (STS). Among them, three unoccupied states mainlylocated around the [18]annulene pore are significantly downshiftedtowards the Fermi level from the energies of the molecular orbitalsin vacuum, which are obtained by density functional theory (DFT)calculations.Results and discussionsScheme of reaction processes of molecule 1 on Ag(111). Thehelicene derivative 1 (Fig. 1) is employed to synthesize thenitrogen-doped NG on Ag(111). The precursor is non-planar dueto the steric hindrance. The organometallic triangular structure isfirst formed with three DBDH molecules by formation ofaryl–Ag–aryl bonds through debromination at 100 °C, namely 2.Then, the C–C bond between the units is formed via aryl–arylcoupling at 150 °C, namely 3. Finally, 3 is planarized by cyclo-dehydrogenation (C1–C2 coupling) at 250 °C, resulting in theformation of nitrogen-doped NG with an [18]annulene pore,namely 4. The nanographenes are further fused to each other byannealing at 300 °C, and consequently the dimer 5 was formed.Synthesis of nitrogen-doped NG with an [18]annulene pore.Molecules 1 were deposited on a clean Ag(111) surface held atroom temperature, and the sample was subsequently annealed at100 °C. We found that ordered uniform triangular nanostructuresextended over the terrace with periodicities of a1= 2.29 ± 0.01 nmand b1= 2.19 ± 0.01 nm (Fig. 2a). The triangular structure wascomposed of three units, whose length of one side was1.80 ± 0.02 nm as indicated by a double arrow. The units wereconnected via three bright dots as marked by yellow arrows inFig. 2b, which correspond to single silver atoms53. Thus, theannealing temperature of 100 °C was high enough to cleave thearyl-Br bonds in 1 on Ag(111)54,55, resulting in the formation ofthe C–Ag–C organometallic bond (2, Fig. 2c). Due to the sterichinderance in the helicene structure, one side of the unit pro-truded more from the surface than another. Subsequently, theorganometallic compound has a chiral configuration on Ag(111).We found that each self-assembled molecular island was com-posed of single chiral molecules (Fig. S1). To induce the furtherreaction, the sample was annealed at 150 °C. Although each unitstill has a triangular shape, the self-assembly became more close-packed as the periodic parameters of a2= 1.97 ± 0.01 nm andb2= 1.95 ± 0.01 nm (Fig. 2d). The close-up view of the STMtopography shows a significant change in the unit (Fig. 2e). Thebright spots (Ag atoms) between the units disappeared, and thelength of one side reduced to 1.57 ± 0.06 nm as indicated by adouble arrow. Thus, these results indicate that the aryl–Ag–arylbond was transformed to the aryl–aryl bond54,55, namely theUllmann-type reaction. The slight distorted part as indicated by ablue arrow implies that no cyclodehydrogenation has occurred.The side of the triangle indicated by a red arrow significantlyprotruded from the surface. We attributed that the non-planarstructure was caused by upward shifting of the naphthyl moietiesin the helicenes (Fig. S2 and Supplementary Data 1). Thisstructure is named as 3 (Fig. 2f).In order to planarize 3, cyclodehydrogenation was induced byfurther annealing at 250 °C. We found that the extendedmolecular island was still composed of triangular molecules(Fig. 3a). The inset shows the close-up view of the product, whichis planar and has a sub-nanoscale pore in the center. Toinvestigate the structure in detail, the tip apex was terminated bya CO molecule56,57. The bond-resolved image shows the skeletonstructure, in which all units had the ring closing. We also foundthat the nitrogen-doped heterocyclic ring appeared dim (Fig. 3b),which is in agreement with previous studies51,58. Thus, theobserved molecule corresponds to the target product 4, which hasthe [18]annulene in the center (Fig. 3c). The subtle bright dotsaround 4 (Fig. 3b and S3) correspond to dissociated Br atomsadsorbed on Ag(111). It is also worth noting that no successfulsynthesis of 4 was seen on Au(111) and Cu(111) surfaces. Wededuce that the formation of the organometallic triangularintermediate 2 plays a major role in the synthesis of NG 4. Sincethe number of adatom on Au(111) is much smaller than that onAg(111), it is difficult to form the organometallic intermediateson Au(111) (Fig. S4). We found that the selective formation oforganometallic chains on Cu(111), which may relate to differentlattice distance and reactivity (Fig. S5).Electronic properties of nitrogen-doped NG. To investigate theelectronic properties, we conducted STS measurements on 4. COmolecules also adsorb at the [18]annulene pore site (Fig. S6). Toexclude the influence of the adsorption on the electronic states ofARTICLE COMMUNICATIONS CHEMISTRY | https://doi.org/10.1038/s42004-023-01023-z2 COMMUNICATIONS CHEMISTRY |           (2023) 6:228 | https://doi.org/10.1038/s42004-023-01023-z | www.nature.com/commschemwww.nature.com/commschem21Debromination100 °CAg(111)34 5C-C couplingC-C coupling C-N coupling[18]Annulene150 °C250 °C 300 °C11122 2N NBr BrN NAg AgAgNN NN NNNNNNNNNNNNNNNNHNNN NNHNNNFig. 1 Scheme of reactions of molecule 1. Reaction processes to form a nitrogen-doped nanographene with an [18]annulene pore and its dimer on Ag(111).Ag AgAg1.80 nma1b1a2b2dcf23e1.57 nm1182 nm[01-1]ΔZ (pm)0a1190.5 nm ΔZ (pm)0b1812 nm ΔZ (pm)0 1670.2 nm ΔZ (pm)0[01-1]N NAg AgAgHHNNH HNNHHNNHHNNHHNNHHFig. 2 Debromination and C–C coupling of 1. a STM topography of the products after annealing at 100 °C. b Close-up view of the topography and (c) thecorresponding chemical structure. d STM topography of the products after annealing at 150 °C. e Close-up view of the topography and (f) thecorresponding chemical structure. Measurement parameters: sample bias voltage V= 50mV and tunneling current I= 10 pA in a. V= 200mV and I= 10pA in b. V= 200mV and I= 3 pA in d. V= 200mV and I= 5 pA in e.COMMUNICATIONS CHEMISTRY | https://doi.org/10.1038/s42004-023-01023-z ARTICLECOMMUNICATIONS CHEMISTRY |           (2023) 6:228 | https://doi.org/10.1038/s42004-023-01023-z | www.nature.com/commschem 3www.nature.com/commschemwww.nature.com/commschemmolecules, we conducted STS measurements before dosing COmolecules. The dI/dV spectra were recorded above the unit, thepore, and the bare Ag(111) surface as a reference, as indicated byred, blue, and gray dots, respectively (Fig. 4a). We found fourprominent peaks of empty states (+500 mV, +750 mV, +1.3 Vand +1.9 V) in the curves taken above both the unit and poresites. The spectra have no significant feature below the Fermienergy level, which is most probably due to the suppression of theb c4High0.2 nm dI/dV (a.u.)Low[01-1]a13310 nm ΔZ (pm)0NNNNNNFig. 3 Cyclodehydrogenation towards synthesis of 4. a Large-scale STM topography of the nitrogen-doped NGs on Ag(111). The inset shows a close-viewimage of single molecule. b Constant height dI/dV mapping of the product and (c) the corresponding chemical structure. Measurement parameters:V= 200mV and I= 4 pA in a. For constant height dI/dV map:V= 10 V, Vac= 10mV in b.1.3 V00.51.01.5750 mV500 mVa bAg(111)LUMOLUMOUS+15 US+17LUMO+1 LUMO+2 LUMO+3L+1L+3L+2-2.0 -1.0-1.5 5.0 5.10.10-0.5 2.0dI/dV (a.u.)L (nm)Sample bias (V)-2.0 -1.0-1.5 0 1.0 1.50.5-0.5 2.0Sample bias (V)1.9 VHigh0.5 nm dI/dV (a.u.)LowcHigh0.5 nm dI/dV (a.u.)LowdHigh0.5 nm dI/dV (a.u.)LoweHigh0.5 nm dI/dV (a.u.)Lowfg h i jIIIIIIUS+20 US+34Fig. 4 Electronic properties of 4. a dI/dV curves recorded above the individual 4 (red and blue lines) and the bare Ag(111) substrate (gray). The insetshows a close-up view of 4. b 2D map composed of 51 sequential dI/dV curves taken along the I-II line indicated in the inset of a. Constant current dI/dVmaps taken at different bias voltages: (c) 500mV, (d) 750mV, (e) 1.3 V, (f) 1.9 V, respectively. g–j DFT calculated spatial distribution of four unoccupiedelectronic states on chemical structures of 4. Measurement parameters: V= 10 mV and I= 10 pA in the inset of a. V= 2.4 V, I= 300 pA, Vac= 10mV forSTS in a. V= 500mV, I= 110 pA, Vac= 10 mV in c. V= 1.1 V, I= 110 pA, Vac= 10mV in d. V= 1.3 V, I= 120 pA, Vac= 10 mV in e. V= 1.9 V, I= 150 pA,Vac= 10mV in f.ARTICLE COMMUNICATIONS CHEMISTRY | https://doi.org/10.1038/s42004-023-01023-z4 COMMUNICATIONS CHEMISTRY |           (2023) 6:228 | https://doi.org/10.1038/s42004-023-01023-z | www.nature.com/commschemwww.nature.com/commschemoccupied state by a strong interaction between 4 and the Agsubstrate. Here, the first four unoccupied electronic states of 4 areattributed as LUMO, LUMO+ 1, LUMO+ 2, and LUMO+ 3states. The two-dimensional map composed of 51 sequentialdI/dV curves was taken along the I-II line in the inset of Fig. 4a. Astrong signal of the LUMO+ 3 state is located at the pore(Fig. 4b). In order to further investigate the spatial distribution ofthe four electronic states, the dI/dV maps were recorded at thecorresponding bias voltages (Fig. 4c–f). Although the state of500 mV distributed on the whole molecule, the pore site appearedrelatively brighter. Only the pore appeared bright in the dI/dVmap taken at 750 mV while the other parts of the moleculeappeared darker. In contrast, the state of 1.3 V distributed only onthe molecular backbone and had no significant signal at the pore.Finally, the strong localization of the state was observed in thepore at 1.9 V. In short, the empty states at 500 mV, 750 mV, and1.9 V were concentrated mostly in the [18]annulene pore. Othernanographene structures with [18]annulene pores also exhibit ahigh density of empty states in the pores even on Au(111),demonstrating the generality of this phenomenon43,45,46. Inaddition, no significant feature of occupied state was observed(Fig. S7), similar to previous studies59–61, which is most probablydue to the suppression of the occupied state by a strong inter-action between 4 and the Ag substrate61,62.To get an insight into the electronic properties, a number ofthe unoccupied states of 4 and the corresponding density of stateswere obtained by DFT calculation in vacuum (Figs. S8 and S9 andSupplementary Data 1). Among them, we found three electronicstates that have strong electronic densities in the [18]annulenepores. The unoccupied state (US)+ 15 concentrates on both themolecular backbone and the pore (Fig. 4g), which is in agreementwith the dI/dV map measured at 500 mV (Fig. 4c). In contrast,the density of US+ 17 state weakened on the molecularbackbone while enhanced on the pore (Fig. 4h), generallyconsistent with the dI/dV map at 750 mV (Fig. 4d). TheUS+ 34 state exhibits a hexagonal distribution in the pore(Fig. 4j), fairly agrees with the dI/dV map at 1.9 V (Fig. 4f). Theagreement of the contrasts suggests that these three states arerelated to the superatom molecular orbitals (SAMOs)43,60,63,which are caused by the hybridization of π-orbitals of the carbonbackbone within the pore. We also found that the US+ 20 statedistributes on both the carbon skeleton and the concave regionsaround the molecule (Fig. 4i), which is also in agreement with thedI/dV map measured at 1.3 V (Fig. 4e). These calculated fourunoccupied states in vacuum have relatively high energies, whichare significantly lowered by the strong molecule-silver substrateinteraction63.Synthesis of nitrogen-doped NG dimer. To investigate the sta-bility of 4 on Ag(111), we further heated the sample to 300 °C. Most4 in the molecular island were still intact (Fig. 5a). Interestingly, wefound the dimer-like products as indicated by arrows. A close-upview of the individual product shows that the junction between theunits appeared brighter than the other parts (Fig. 5b). The constantheight dI/dV map (Fig. 5c) and the corresponding Laplace filteredimage (Fig. 5d) revealed the inner structure, in which two moleculeswere fused by formation of the pyrazine ring (Fig. 5e). Around thejunction, a strong signal in the dI/dV map was detected. Since nomagnetic feature was observed in the dI/dV curve (Fig. S10), thebright contrast may result from the topographic corrugation causedby the slight sp3 character of the central NH–N units. Thus, thisdimer is apparently product 5, which was proposed in Fig. 1. SinceN=N double bond often serves as an electrophile in organicchemistry64, nucleophilic attach by the π bond of the adjacentmonomer compound followed by migration of hydrogen to theadjacent nitrogen can afford NH unit in a reasonable way. Never-theless, the N core level measurement by XPS measurement couldconclude the chemical analysis65. Note that no significant differencein the electronic properties between the dimer and the monomer wasobserved (Fig. S11). After annealing to 350 °C, only disorderednanostructures were formed on Ag(111) (Fig. S12), which is mostprobably associated with the cleave of C–C bonds of NGs and sub-sequent random fusion.ConclusionsIn summary, the nitrogen-doped nanographene with an [18]annulene pore and its dimer were synthesized with 3,12-dibromo-7,8-diaza[5]helicene on Ag(111) through sequential reactions ofdebromination, aryl–aryl coupling, cyclodehydrogenation, andC–N coupling. The bond-resolved imaging with a CO moleculeterminated tip shows the molecular backbones. The STS mea-surements detected the four unoccupied states of the nitrogen-doped nanographene on Ag(111). Among them, three statesconcentrated mainly on the [18]annulene pore. These energiessignificantly lowered from those obtained by DFT calculations invacuum, which is most probably caused by the strong hybridi-zation with the confined surface state. This work demonstratedthat on-surface synthesis is an advanced method to fabricatenanographenes with defined accurate shapes.51602 nm ΔZ (pm)0aHigh0.5 nm dI/dV (a.u.)Lowb1400.5 nm ΔZ (pm)0cedNNNNHNNN NNHNNNFig. 5 Synthesis of 4 dimers on Ag(111). a STM topography of the Ag(111) surface after annealing at 300 °C for 10min. b Close-up view of single dimer.c Constant height dI/dV map over the dimer in b, and (d) the corresponding Laplace filtered image. e Chemical structure of the dimer, 5. Measurementparameters: V= 200mV and I= 10 pA in a. V= 200mV and I= 5 pA in b.COMMUNICATIONS CHEMISTRY | https://doi.org/10.1038/s42004-023-01023-z ARTICLECOMMUNICATIONS CHEMISTRY |           (2023) 6:228 | https://doi.org/10.1038/s42004-023-01023-z | www.nature.com/commschem 5www.nature.com/commschemwww.nature.com/commschemMethodsSTM experiments. All experiments were conducted with a home-made low temperature scanning tunneling microscope (STM),operating under ultrahigh vacuum (<1 × 10−10 mbar) at 4.3 K.Clean Ag(111) surfaces were obtained through repeated cycles ofAr+ sputtering for 10 min and annealing at 700 K for 10 min. Thetemperature of sample was measured by a thermocouple and apyrometer. 3,12-dibromo-7,8-diaza[5]helicene (1) molecules52were deposited from Knudsen cells (Kentax GmbH). A STM tipwas made from the chemically etched tungsten. For constantheight dI/dV imaging, the tip apex was terminated by a COmolecule56,57. The modulation amplitude was 7 mVrms and thefrequency was 510 Hz for the STS measurement.Theoretical calculations. DFT calculations were performed bythe Gaussian 16 package66 using the B3LYP functional and 6-31 G(d,p) basis set. The molecular orbitals were further calculatedby Multiwfn 3.8 code67,68.Material synthesis. 3,12-Dibromo-7,8-diaza[5]helicence (1) wasprepared according to the procedure reported in the paper52.Data availabilityAll relevant data are available from the authors upon reasonable request.Received: 21 July 2023; Accepted: 6 October 2023;References1. Wu, J., Pisula, W. & Müllen, K. Graphenes as potential material forelectronics. Chem. Rev. 107, 718–747 (2007).2. Han, W., Kawakami, R. K., Gmitra, M. & Fabian, J. Graphene spintronics. Nat.Nanotechnol. 9, 794–807 (2014).3. Loh, K. P., Tong, S. W. & Wu, J. Graphene and graphene-like molecules:prospects in solar cells. J. Am. Chem. Soc. 138, 1095–1102 (2016).4. Gadipelli, S. & Guo, Z. X. 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Kewei Sun acknowledges the supporting of ICYSproject.Author contributionsS.K. planned this project. K.S. performed the on-surface synthesis and the character-ization. D.L. conducted DFT calculation. K.S. and D.L. analyzed data. T.K., S.M., andY.T. made synthetic plan and synthesized the precursor molecules. K.S., D.L., and S.K.wrote the manuscript in joint with Y.T. through discussion.Competing interestsThe authors declare no competing interests.Additional informationSupplementary information The online version contains supplementary materialavailable at https://doi.org/10.1038/s42004-023-01023-z.Correspondence and requests for materials should be addressed to Youhei Takeda orShigeki Kawai.Peer review information Communications Chemistry thanks Cesar Moreno and Jiong Lufor their contribution to the peer review of this work.Reprints and permission information is available at http://www.nature.com/reprintsPublisher’s note Springer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.Open Access This article is licensed under a Creative CommonsAttribution 4.0 International License, which permits use, sharing,adaptation, distribution and reproduction in any medium or format, as long as you giveappropriate credit to the original author(s) and the source, provide a link to the CreativeCommons license, and indicate if changes were made. The images or other third partymaterial in this article are included in the article’s Creative Commons license, unlessindicated otherwise in a credit line to the material. If material is not included in thearticle’s Creative Commons license and your intended use is not permitted by statutoryregulation or exceeds the permitted use, you will need to obtain permission directly fromthe copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.© The Author(s) 2023COMMUNICATIONS CHEMISTRY | https://doi.org/10.1038/s42004-023-01023-z ARTICLECOMMUNICATIONS CHEMISTRY |           (2023) 6:228 | https://doi.org/10.1038/s42004-023-01023-z | www.nature.com/commschem 7https://doi.org/10.1038/s42004-023-01023-zhttp://www.nature.com/reprintshttp://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/www.nature.com/commschemwww.nature.com/commschem On-surface synthesis of nitrogen-doped nanographene with an [18]annulene pore on�Ag(111) Results and discussions Scheme of reaction processes of molecule 1 on Ag(111) Synthesis of nitrogen-doped NG with an [18]annulene pore Electronic properties of nitrogen-doped NG Synthesis of nitrogen-doped NG dimer Conclusions Methods STM experiments Theoretical calculations Material synthesis Data availability References References Acknowledgements Author contributions Competing interests Additional information