Topological Defects Induced High-Spin Quartet State in Truxene-Based Molecular Graphenoids

Open AccessCCS ChemistryRESEARCH ARTICLE10 May 2022Topological Defects Induced High-Spin Quartet State in Truxene-Based Molecular Graphenoids Can Li†, Yu Liu†, Yufeng Fu-Hua Xue, Dandan Guan, Yaoyi Li, Hao Zheng, Canhua Liu, Jinfeng Jia, Pei-Nian Deng-Yuan Li and Shiyong Wang Li† *Corresponding authors: E-mail Address: [email protected] Key Laboratory of Artificial Structures Quantum Control, Ministry Education, Shenyang National for Materials Science, School Physics Astronomy, Shanghai Jiao Tong University, 200240 †C. Y. Liu contributed equally to this work.Google Scholar More articles by author , Liu† Xue Advanced Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center Materiobiology Dynamic Chemistry, Chemistry Engineering, East China University Technology, 200237 Google Guan Tsung-Dao Lee Institute, Sciences, 201315 Zheng Jia https://doi.org/10.31635/ccschem.022.202201895 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Topological defects graphene materials introduce exotic properties with both fundamental importance technological implications, absent their defect-free counterparts. Although individual topological have been widely studied, collective magnetic behaviors originating from well-organized multiple remain a great challenge. Here, we examined the three pentagon truxene-based molecular graphenoids using scanning tunneling microscopy (STM) non-contact atomic force microscopy. Unpaired ? electrons were introduced into aromatic topology truxene one dissociating hydrogen atoms at via atom manipulation. STM measurements, together density functional theory calculations, suggested that unpaired ferromagnetically coupled, forming high-spin quartet state S = 3/2. Our work demonstrates spin ordering could be realized through engineering regular patterned graphenoids, providing new platform designing one-dimensional ferromagnetic chains two-dimensional networks. Download figure PowerPoint Introduction exist locally change intrinsic physical chemical properties. Examples include sp3 carbons, vacancies, carbon tetragons, pentagons, heptagons, dislocations, grain boundaries, which intriguing electronic, magnetic, optical, mechanical implications sensors, electronics, spintronics, quantum technologies.1–13 usually break sublattice symmetry unconventional ?-electron magnetism, differ d/f electron magnetism.14 In past decade, intense research efforts devoted studying such magnetism materials. many systems exhibit signatures presence sp2 it remains elusive reveal defects. This is mainly because are randomly interspersed lattice, arranging these controllable way challenging traditional top-down methods. Additionally, as graphene-based depends crucially on structure surrounding environments, requires ability fabricate samples precision techniques characterize them down single-chemical-bond level. Recently, atomically precise segments graphene, also named nanographenes or carefully designed reported taking advantage recent advances on-surface synthesis probe techniques.15–25 On-surface synthetic approach involves precursor solution subsequent surface-assisted reactions building blocks, permits synthesized nanostructures wide tenability.26–32 After synthesis, structural electronic can directly characterized surface techniques, combined (nc-AFM) system spatial resolution.33 Recent studies bottom-up revealed host interesting localized states, tunable band gap, properties.21,22,34,35 Compared planar configuration polyaromatic hydrocarbons purely hexagonal rings, feature curvature.15,17,18 Typically, deformation accompanied strong coupling underneath metal substrate, hindering detection Thus, characterization significant report study states molecule (10,15-dihydro-5H-diindeno[1,2-a:1?,2?-c]fluorene), heptacyclic polyarene containing pentagons vertex per ring.36 Using manipulation, observed carbons controllably dissociated one, transforming carbons. Due fully character, up topology, state, (DFT) calculations. High-resolution nc-AFM imaging dehydrogenated molecules (DTrs) adopted curved Au(111), having lower adsorption heights. resulting DTrs quenched spectroscopy (STS) measurements. To structure, deposited in-situ an insulating NaCl/Au(111) substrate hydrogens DTrs. sharp contrast singly occupied/unoccupied orbitals (SOMOs/SUMOs) resolved generated NaCl film, confirmed states. results further extended realize frameworks. Experimental Methods measurement Sample preparation carried out commercial low-temperature Unisoku Joule-Thomson (UNISOKU Co., Ltd., Osaka, Japan) under ultra-high vacuum conditions (3 × 10?10 mbar). Au(111) single-crystal was cleaned cycles argon ion sputtering subsequently annealed 800 K obtain flat terraces. thermally clean room temperature 2 min. Afterward, sample transferred cryogenic scanner (Traditional UNISOKU Style, 4.9 cooling, then islands 10 K. Carbon monoxide dosed onto cold ? 7 (4 10?9 mbar, min). achieve resolution, CO picked Au apex tungsten tip. A quartz tuning fork resonant frequency 26 KHz used measurements q-Plus sensor Japan). lock-in amplifier (589 Hz, 0.1–0.5 mV modulation; Nanonis inner amplifier, SPECS Surface Nano Analysis GmbH Berlin, Germany) acquire dI/dV spectra, obtained unless otherwise stated. Spin-polarized DFT calculations The ground structures gas-phase optimized PBE0-D3 (BJ)37–39 def2-SVP basis set,40 def2-TZVP set40 single point energy calculation. densities analyzed Multiwfn41 Visual Dynamics (VMD).42 Images isosurfaces plotted Visualization Electronic STructural (VESTA) software.43 Results Discussion According Lieb’s theorem Ovchinnikov’s rule, imbalance bipartite honeycomb lattice states.14 number given equation (NA ? NB)/2, where NA(NB), A(B) lattice. As shown Figure 1a, application predicated triangular zigzag triangulene its larger homologs Experimentally, [2]-triangulene fused 1/2) [3]-triangulene (6 1) solution, open-shell characteristics resonance (ESR) spectroscopy44–47; [4]-triangulene (10 3/2), [5]-triangulene (15 2), [7]-triangulene (28 3) synthesis.48–51 system, size increased quickly S, total required several benzene rings N (S + (2S 1). triangulenes > 3 due difficulties encountered sublimation large precursors surfaces. 1 | High-spin nanographene systems. (a) Magnetic triangulene-based while indicates molecules. (b) Conceptual routes towards molecules, chain, network based truxene. imbalance, defect much more efficient introducing graphenoids. Incorporating ring electron. principle, possible build high efficiently periodically positioning electronically coupled We performed searches database found (containing connected 1,3,5-side central ring) ideal C3 symmetry, (Figure 2). interestingly, blocks highly For example, graphenoid linked has 9/2 (Figures 1b 2c) only 22 less than those [10]-triangulene (55 rings). Except designer polymer would ferromagnetism tunability exploring low-dimensional 1b). first step toward efforts, limited our discussion work. Realization Chemical Spin-density distributions corresponding (a), respectively. (c) trimer. (d) Zoom-in DTr3 center marked blue dash circle (a). (e) trimer (c). depicts scheme Through tip-induced manipulation thermal annealing, sites two, inside molecule, referring successive DTr1, DTr2, convenience, indicating electrons, respectively 2a). 2b) (the detailed distribution 2e), triplet DTr2 DTr3, physics behind attributed minimization on-site Coulomb repulsion symmetry.10 Since ring; spin-up preferred reside (1,3,5-carbon sites) spin-down other (2,4,6-carbon minimize 2d). contrast, if 1,4-side ring, antiferromagnetically repulsion.25,52,53 2c presents DFT-calculated Owing all together, 9/2. high-resolution microscopy, 3. ( Supporting Information S1) details Information). stage holding 4 characterization. large-scale image 3a Au(111). functionalizing tip being imaged local bright dot since there pointing 3d). With above slowly ramping bias voltage 3.2 V S2). dehydrogenation, DTr1 featured curvature getting closer opposite side tilting upward (nc-AFM two monitored changes. Similar observations made displayed height rings. 3c, constant-height current images taken some fine features highest occupied orbital (HOMO; S3). Scanning differential conductance employed incremental (dI/dV) resolve low-energy no Kondo resonances S4), effect screening net spins conduction Au(111).54 absence might either lack clarify finding, resolution spectra S5) recorded mappings DTr3. If indeed DTrs, but kondo SOMOs resided should observed. However, SOMOs/SUMOs not detected Interestingly, reproduced undehydrogenated precursor, radicals Structural Large-scale (bias voltage: 0.5 V, setpoint: 50 pA; scale bar: 5 nm). Two red square, truxenes. (b–d) From top down: structures, mV; bars: 500 pm), (resonant frequency: kHz, oscillation amplitude: 80 pm; pm) precursors, decouple away situ held 8 salts stored temperature, self-assembled monolayer bilayer islands. thin film decoupled efficiently.47,55 Upon deposition, adsorb S6). procedures island. indicated hosted SOMO/SUMO, doublet 1/2. experimentally. 4c, different positions predicted SOMO SUMO ?1 1.5 V. 4d energies shapes SUMO, consistent simulations SUMO. 4b 1. S7, corner. Such showing peaks SUMOs intensity corner, simulated 4d. excluded possibility closed-shell comparing frontier experimental outcomes S7). observation SUMOs, asymmetric distribution, NaCl. 4b, state. Unlike had delocalized over entire S8). near threefold symmetric 4d, agreement simulations. 1/2 experiments defects, spin-polarized calculated spectrum I/V numerical (d). Constant (current: nm) LDOS Conclusion demonstrated realization organized By combining resolving SOMOs/SUMOs. paves induced provides fabrication frameworks networks well implications. like note similar published recently Mishra et al.56 available includes methods computational details. Competing Interests authors declare competing financial interests. Preprint Statement presented article posted preprint server before publication CCS Chemistry. here: https://arxiv.org/abs/2202.03853 Acknowledgments S.W. acknowledges support R&D Program (grant no. 2020YFA0309000), Natural Foundation nos. 11874258 12074247), Municipal Technology Qi Ming Xing Project 20QA1405100), Fok Ying Tung young researchers SJTU 21X010200846). supported 2019YFA0308600, 2016YFA0301003, 2016YFA0300403), NSFC (grants 21925201, 11521404, 11634009, 92065201, 11874256, 11790313, 11861161003), Strategic Priority Chinese Academy Sciences XDB28000000), Commission Municipality 20ZR1414200, 2019SHZDZX01, 19JC1412701, 20QA1405100) partial support. References Fan Q.; Yan L.; Tripp M. W.; Krej?í O.; Dimosthenous S.; Kachel S. R.; Chen M.; Foster A. Koert U.; Liljeroth P.; Gottfried J. M.Biphenylene Network: Nonbenzenoid Allotrope.Science2021, 372, 852–856. 2. Lombardi F.; Lodi A.; Ma J.; Slota Narita Myers W. 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