Structural Variation in Surface-Supported Synthesis by Adjusting the

Structural Variation in Surface-Supported Synthesis by Adjusting the Stoichiometric Ratio of the Reactants Zhongmiao Gong,†,⊥ Biao Yang,†,⊥ Haiping Lin,†,⊥ Yunyu Tang,‡ Zeyuan Tang,† Junjie Zhang,† Haiming Zhang,† Youyong Li,† Yongshu Xie,‡ Qing Li,*,† and Lifeng Chi*,† †

Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 199 Ren’ai Road, Suzhou, 215123, Jiangsu, People’s Republic of China ‡ Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, People’s Republic of China S Supporting Information *

ABSTRACT: Surface-supported coupling reactions between 1,3,5tris(4-formylphenyl)benzene and aromatic amines have been investigated on Au(111) using scanning tunneling microscopy under ultra-high-vacuum conditions. Upon annealing to moderate temperatures, various products, involving the discrete oligomers and the surface covalent organic frameworks, are obtained through thermal-triggered on-surface chemical reactions. We conclude from the systematic experiments that the stoichiometric composition of the reactants is vital to the surface reaction products, which is rarely reported so far. With this knowledge, we have successfully prepared two-dimensional covalently bonded networks by optimizing the stoichiometric proportions of the reaction precursors. KEYWORDS: scanning tunneling microscopy, on-surface chemistry, stoichiometric ratio, aldehyde−amine coupling, two-dimensional framework he blossoming development of graphene1 in the past decade has clearly demonstrated the essential importance of dimensionality for material properties. This principle has inspired tremendous interest in single-layered materials, e.g., transition metal dichalcogenides, 2 black phosphorus,3 and so on. Besides the inorganic materials, surface covalent organic frameworks (SCOF), in which adjacent building blocks are connected covalently via onsurface chemical reaction,4−12 provide alternative approaches for constructing two-dimensional (2D) organic materials and surface-supported oligomer/polymer structures, following the pioneering work of Grill et al.13 To date, the most commonly applied synthetic strategy is the Ullmann coupling reactions.13−16 With this approach, various kinds of covalently connected structures were synthesized on metal surfaces.17−22 Later on, halogen-free routes were successively proposed, including boronic acid condensation,23 direct coupling between sp1,24−26 sp2,27−29 and sp330 carbons, and imidization.31 Very recently, the cyclotrimerization reaction of acetyls32 is reported, providing a new protocol for the on-surface reactions. Specifically, Linderoth and co-workers found that surfacesupported polymers can be constructed via the coupling of aromatic aldehyde and amine in ultrahigh vacuum (UHV),

which is known as Schiff-base condensation.31,33 Such a mechanism has been extensively adopted in the synthesis of surface-supported polymers, both in solution and under vacuum.34−38 To date, most research has been focused on thermal treatment, the backbone length of precursors, soft solution methodology, and other factors to fabricate desired products. Nevertheless, a precise control of the reaction is still far from available. In solution, it has been well accepted that the adjustment of stoichiometric proportions of the reactant compounds is essential for obtaining the desired products. However, such influence has been seldom studied in the crosscoupling reaction under UHV condition. Herein, we present a systematical study of the aldehyde− amine coupling on Au(111) surfaces under UHV conditions. With the aid of scanning tunneling microscopy (STM), we have been able to monitor the occurrence of the on-surface reactions between various precursors. We found that by tuning the stoichiometric proportions of reactants reaction products can

T

© XXXX American Chemical Society

Received: December 2, 2015 Accepted: April 4, 2016

A

DOI: 10.1021/acsnano.5b07601 ACS Nano XXXX, XXX, XXX−XXX

Article

www.acsnano.org

Article

ACS Nano Scheme 1. Selected reactants and the proposed reaction pathways.

Figure 1. (a) Large-scale and (b) zoomed STM images after co-deposition of TFPB and DATP at room temperature, with the stoichiometric ratio 2:1. The inset of (b) shows the unit cell of the self-assembly phase. The lower panel of (b) shows the structural model of the selfassembly island. In the model, red, green, blue, and gray balls represent oxygen, carbon, nitrogen, and hydrogen atoms, respectively. (c) Large-scale STM image after annealing the prepared sample to 400 K. (d) High-resolution STM image of (c). All the STM images were acquired with Vb = −1.0 V and It = 20 pA. (e) Relaxed structural model of (d). The black and red numbers represent the calculated and experimentally measured size of the product.

be rationally selected, giving rise to the controllable synthesis of different products with variable terminal groups on surfaces.

With this knowledge, we are able to tune the product structures from identical discrete oligomers to form low-defect-density B


Article

ACS Nano

Figure 2. (a) Large-scale topographic STM image after annealing the prepared sample at 400 K (TFPB to DATP ratio is 2:1). (b) Highresolution STM image of the disordered region of (a). The arrows highlight an unreacted TFPB monomer and a representative reaction product. STM images were captured at the conditions of Vb = −1.0 V and It = 20 pA. (c) Structural models of the highlighted products of (b).

Figure 3. Large-scale (a) and zoomed image (b) of the self-assembly structure after co-deposition of TFPB and DATP with the stoichiometric ratio 2:3. The lower panel of (b) gives the structural model of the self-assembly structure. (c) Large-scale and (d) zoomed STM images after annealing the molecular surface structure at 400 K. All the STM images were acquired with Vb = −1.0 V and It = 20 pA.

SCOFs on a gold surface. The present finding demonstrates the importance of stoichiometric composition in on-surface reactions and thus provides new insight into the methodology of controllable synthesis of surface-supported materials via cross-coupling of two different reactants.

aminophenyl)benzene (TAPB). The reaction pathway is demonstrated in Scheme 1, where amines are suitable nucleophilic species and aldehydes act as electrophilic species. Since multiple reactive groups are available within both precursors, diverse products can be expected. Figure 1a gives the representative STM image after codeposition of TFPB and DATP precursors on a Au(111) surface held at room temperature (0.9 ML). Although some disordered regions are visible, most constituent molecules assemble into highly ordered islands. From the high-resolution image (Figure 1b), individual molecules can be clearly

RESULTS AND DISCUSSION For the surface-supported aldehyde−amine cross-coupling, we have chosen three reactants: 1,3,5-tris(4-formylphenyl)benzene (TFPB), 4,4″-diamino-p-terphenyl (DATP), and 1,3,5-tris(4C


Article

ACS Nano

Figure 4. (a) Representative STM images of tetragon, petagon, hexagon, and heptagon polygons of the covalent framework. (b) Statistical counting of the observed organic polygons on the surface. All the STM images were acquired with Vb = −1.0 V and It = 20 pA.

distinguished, in which the triangle-shaped objects are the TFPB molecules, while the stripe-like species are the DATP molecules. The island is stabilized via the net N−H···O hydrogen interactions between the amino and aldehyde groups. Each DATP molecule interacts with four adjacent TFPB monomers (the structural model is shown in the lower panel of Figure 1b). As can be seen, each unit cell (inset of Figure 1b, a = 3.65 nm, b = 1.70 nm, θ = 80°) is composed of two TFPB monomers and one DATP, corresponding to a 2:1 stoichiometric ratio. Distinct changes take place in the topographic image upon annealing the self-assembled molecular structures at 400 K for 20 min. As shown in Figure 1c, most monomers are converted into the bowtie-like species. Closer inspection reveals that each product is composed of two TFPBs and one DATP (Figure 1d). The TFPB component can be identified from their “Y” shape, in which bright protrusions correspond to the phenyl rings. Two TFPBs are linked together by a rod-like DATP monomer. Previous reports have revealed that the amino− aldehyde coupling reaction could take place at 400 K on a Au(111) surface, close to the temperature at which the structural evolution occurs in our experiment (Figure 1c).31,33 Moreover, different from the self-assembly phase shown in Figure 1b, TAPB and DATP interact with each other in a headto-head fashion after annealing. We therefore attribute the structural evolution to the formation of trimer via the direct coupling of aromatic trialdehyde and diamine at elevated temperatures. To further validate our proposed hypothesis, a density functional theory (DFT) calculation is performed. Figure 1e exhibits the relaxed structure of the reaction product. The calculated mean length of the molecule is 3.32 nm, in good agreement with the experimental measurements (3.29 nm), thus unambiguously evidencing the surface-assisted Schiff-base condensation reaction. Note that the trimer product shown in Figure 1d, involves two TFPBs and one DATP, close to the ratio of the reactants in the self-assembly island (Figure 1b), thus suggesting that the stoichiometric compositions may play an important role in the selectivity of reaction products. Furthermore, some irregular regions are observed in addition to the trimers, as shown in Figure 2a. A closer investigation reveals that such a region is composed of different kinds of reaction products, e.g., isolated TFPB monomers and a dimer formed by the condensation coupling of one TAPB and one DATP (highlighted by the arrows in Figure 2b; the structural model is given in Figure 2c). The presence of such minority products can be explained by two reasons: the kinetic effect arising from the strong and

irreversible interaction prevents the formation of identical products; the stoichiometric ratio of TFPB to DATP slightly deviates from 2:1 and thus inevitably produces diverse oligomers besides the trimers shown in Figure 1e. To further investigate the influence of the compound ratio on the aldehyde−amine coupling reaction on surfaces, we performed systematic experiments by reducing the amount of TFPB gradually. Upon decreasing the co-deposition proportion between TFPB and DATP to 2:3, a new self-assembly phase is formed (coverage is 0.8 ML), which differs significantly from that shown in Figure 1a (as shown in Figure 3a and b). On this surface, no large-scale well-ordered islands are visible. However, one can still identify that some monomers self-assemble into the structure shown in Figure 3b. The ratio of TFPB to DATP in Figure 3b is 1:1, smaller than the deposited stoichiometric ratio of 2:3. Fuzzy signals are seen because of the fast movement of DATP monomers on the surface. The intermolecular interaction between amines is much weaker than that between aldehydes, so that DATP can be stabilized on the surface only when they are interacting with TFPB. More interestingly, a completely new porous framework is formed extending the entire surface after annealing the surface at 400 K for 20 min, as illustrated in Figure 3c. Here, a second layer is not observed even though adequate precursors are provided, suggesting a weak molecule−molecule interaction between the perpendicularly staking molecules. Closer inspection reveals that the pores are formed with numerous polygons, and they do not have identical shapes (Figure 3d). Such coexistence of different polygons in the framework has been reported in solution.36 Figure 4a gives the STM images, representing four kinds of observed polygons. Note that the sides of these polygons are of the same shape and are similar to the bowtielike trimers shown in Figure 1d. The measured mean length (3.27 nm) is close to that shown in Figure 1e (3.32 nm), thus suggesting an aromatic aldehyde−amine covalent coupling in 2D network formations. Statistical analysis (Figure 4b) reveals that pentagons and hexagons are dominating species, while tetragons and heptagons are rarely observed. Such pentagon and heptagon defects are quite common in the honeycomb systems,36 which are ascribed to the flexible TFPB−DATP bond angle. It is also noteworthy that the porous network is very robust, so that we did not observe any dynamic movement of the structure during the scanning, which is rather different from those in solution.36 Upon further decreasing the TFPB to DATP proportion to 1:3, fork-like isolated products are formed by annealing the sample to 400 K (coverage is 0.3 ML), as shown in Figure 5a. D


Article

ACS Nano

Figure 5. (a) Large-scale and (b) zoomed STM images after co-deposition of TFPB and DATP at 400 K, with the stoichiometric ratio 1:3. (c) Structural model of the product shown in (b). All the STM images were acquired with Vb = −1.0 V and It = 20 pA.

Figure 6. Monte Carlo simulations of molecular interactions as the stoichiometric ratios of DATP (red) to TAPB (blue) are (a) 1:2 to (b) 2:3 and (c) 3:1. The probabilities of the monomer, dimer, trimer, and tetramer are set to be 0.5, 0.3, 0.2, and 0.1, respectively.

The high-resolution topographic image (Figure 5b) reveals that each product is composed of a triangle-shaped core and three rod-like terminals. The structural model is exhibited in Figure 5c, in which all the aldehyde species are chemically saturated since excessive DATPs are provided, giving rise to identical tetramers with amino group terminations. Importantly, one can conclude from Figure 5b that the TFPB to DATP ratio is close to 1:3, the same as the stoichiometric ratio of the deposited precursors. In addition, similar to that in Figure 3a, fuzzy patterns are observed in Figure 5a, which arises from the extra amines on the surface. The above experiments have clearly demonstrated that the stoichiometric ratio of the precursors plays a vital role in the selectivity of the final products during on-surface synthesis. It is well-known that different self-assembly structures can be obtained by tuning the ratio of the constitutes. Such a phenomenon arises from the relative weak and reversible intermolecular interactions, so that the self-assembly ordering is determined thermodynamically by the minimization of the free energy. The situation for covalent connection is, however, rather different since the coupling strength is strong and irreversible; thus, the products are not solely determined thermodynamically. According to previous reports, the covalently connected oligomers or networks are a result of two major parameters: the reaction rates for the coupling and the diffusion ability of the reactants on the surface.17 For the aldehyde−amine condensation reaction on the Au(111) surface, the reaction rate is fixed. Correspondingly, the coupling probability is determined by the diffusion activity of the components: the longer the mean free path, the larger the coupling probability.17

To study the underlying insights of the formation of the observed molecular products, generic Monte Carlo simulation was employed. Initially, all the monomers are randomly placed over the large surface lattice. As the Schiff-base condensations are spontaneous reactions in the experimental conditions, the coupling probability is set to be 1 in all Monte Carlo simulations. Then, we randomly and successively select the monomer molecules and let them rotate or translate with a probability of 50%. When the monomers form dimers, trimers, and tetramers over Au(111) surfaces, their mobility decreases due to the increased molecular weight. In our simulations, the mobility (rotations, translations) of dimers, trimers, and tetramers was defined as 30%, 20%, and 10%, respectively. As seen in Figure 6a, when the stoichiometric ratio of DATP to TAPB is 1:2, dominated bowtie-like products are formed. This phenomenon can be simply interpreted in this way: At the initial stage, dimers are formed via the coupling of TFPB and DATP monomer. However, the increment of molecular weight of the dimers suppresses their mobility on the surface, which decreases the dimer−dimer coupling probability. When all the DATP monomer has reacted into such dimers, the dimers will couple with the excess provided TFPB, resulting in the bowtielike trimers (Figure 1d). When the stoichiometric ratios of DATP to TAPB are increased from 1:2 to 2:3 and to 3:1, bowtie-like species, hexagonal ring, and triangle-shaped figures are formed (Figure 6a−c), in nice agreement with the experimental observations. As a consequence, it is this dynamic behavior that leads to the formation of diverse products when changing the stoichiometric ratio of the reactants on surfaces. Usually, long-range porous networks are constructed in solution or on a gas−solid interface in ambient condiE


Article

ACS Nano

Figure 7. Representative STM images after annealing the TFPB and TAPB co-deposited Au(111) sample at 400 K for 20 min. The TFPB to TAPB precursor ratio is 4:1 (a), 2:1 (b), 1:1 (c), and 1:2 (d). The size of all the images is 10 nm × 10 nm. (e) Statistical counting of n/N versus the TFPB to TAPB ratio, where n is the number of perfect pores and N is the number of total constituent monomers.

oligomers on the surfaces. Our finding demonstrates the importance of chemical composition during the on-surface reaction, thus providing a strategy for the controlling of the reaction products on surfaces.

tions.35,36,38,39 In UHV, kinetics of the precursors would prevent the formation of defect-free frameworks during the cross-coupling.17,40 The above work then demonstrates that the synthesis of desirable products on surfaces requires not only the adjustment of the experimental parameters but also the careful tuning of the stoichiometric compositions of the precursors. With this knowledge, we designed two precursors, TAPB and TFPB, both of which possess 3-fold symmetry. The 2D networks were synthesized by co-deposition of the two constituent molecules onto the Au(111) surface held at room temperature and then annealing to 400 K for 20 min. Figure 7a−d give the representative STM images of the reaction products when the TAPB to TFPB stoichiometric ratio is tuned to 4:1, 2:1, 1:1, and 1:2. It is quite obvious that a porous structure tends to be formed in all the conditions, which arises from both the reactants’ symmetry and the directionality of the newly formed bonds. The pore to pore distance is about 2.7 nm, in nice agreements with previous reports;38 thus the products can be ascribed to the aldehyde−amine crosscoupling. In addition, it is quite clear from the STM images that highest quality 2D networks were prepared when the TAPB to TFPB stoichiometric ratio is set to 1:1 (details of the self-assembly and reaction products can be found in Figure S1). A similar conclusion is deduced by the statistical analysis. To characterize the structures quantitatively, we count the number of perfect pores (n, a perfect pore means a pore formed by the polymerization of three TAPBs and three TFPBs) and the number of constituent molecules (N) in each condition. Then the value n/N can be utilized to characterize the quality of the porous networks. As shown in Figure 7e, n/N equals 0.12 when the TAPB to TFPB ratio is 1:1, much higher than the other three conditions. This series of systematical experiments further confirmed the importance of the component ratio to the reaction products.

METHODS Sample preparation and STM measurements were performed in an ultra-high-vacuum system (base pressure is better than 1 × 10−10 Torr). Experiments were conducted with a commercial Unisoku lowtemperature scanning tunneling microscopy (USM-1500S). In the present paper, if not otherwise mentioned, all the STM measurements are performed at 77 K. The Au(111) surface was cleaned by standard argon sputtering−annealing cycles before deposition of organic molecules. A commercial Pt−Ir tip was carefully prepared by e-beam heating before loading to the STM head. The STM images were analyzed using WsXM. DATP (purity higher than 98%) was purchased from TCI Company, and TAPB (purity higher than 98%) was purchased from J&K Company. For the synthesis of TFPB, tribromobenzene (1.0 g, 3.2 mmol), 4-formylphenylboronic acid (1.45 g, 95.3 mmol), bis(triphenylphosphine)palladium(II) dichloride (300 mg, 0.4 mmol), and an aqueous solution of potassium carbonate (2 M, 0.2 mol) were added to tetrahydrofuran (200 mL) in a 500 mL roundbottom flask equipped with a stirring bar and a condenser. The flask was evacuated and backfilled with N2 three times. The reaction mixture was then heated to reflux for 12 h. After cooling, the solution was extracted with dichloromethane (3 × 100 mL). The combined organic layer was successively washed with H2O and brine and then dried with MgSO4 and filtered, and the solvent was removed in vacuo. The crude product was then dissolved in dichloromethane and run through a short silica gel column. The resulting solid was recrystallized from MeCN to afford a white solid of TFPB (600 mg, 48%). The 1H NMR spectrum matches well with that previously reported (see Supporting Information Figure S2 for details). The first-principles calculations were carried out in the framework of DFT and with the VASP code. The electron−ion interactions were described with the projector augmented wave method with a kinetic energy cutoff of 400 eV. The exchange and correlation energy was calculated with the Perdew−Burke−Ernzerhof functional. The nonlocal effects were taken into account using the vdw-DF functional of Langreth and Lundqvist.41,42 The Au(111) surface was modeled using a periodic slab consisting of two atomic layers and a vacuum of 20 Å. The bottom layer was kept fixed, while the other atoms were fully relaxed until the force on each atom was smaller than 0.01 eV per angstrom.

CONCLUSIONS In summary, we have performed an STM study of the Schiffbase condensation between TFPB and DATP/TAPB on Au(111) under UHV. Desirable oligemer products and regular SCOFs via on-surface chemistry were synthesized through the rational adjustment of stoichiometric compositions of the reaction precursors. The underlying mechanisms that lead to the diverse surface patterns are investigated by Monte Carlo simulations. The selective products are a result of the balance of coupling rate of precursors and the mobility of monomers or F


Article

ACS Nano

(12) Zhang, X.; Liao, L.; Wang, S.; Hu, F.; Wang, C.; Zeng, Q. Polymerization or Cyclic Dimerization: Solvent Dependent HomoCoupling of Terminal Alkynes at HOPG Surface. Sci. Rep. 2014, 4, 3899−3904. (13) Grill, L.; Dyer, M.; Lafferentz, L.; Persson, M.; Peters, M. V.; Hecht, S. Nano-architectures by Covalent Assembly of Molecular Building Blocks. Nat. Nanotechnol. 2007, 2, 687−691. (14) Lipton-Duffin, J. A.; Ivasenko, O.; Perepichka, D. F.; Rosei, F. Synthesis of Polyphenylene Molecular Wires by Surface-Confined Polymerization. Small 2009, 5, 592−597. (15) Cai, J.; Ruffieux, P.; Jaafar, R.; Bieri, M.; Braun, T.; Blankenburg, S.; Muoth, M.; Seitsonen, A. P.; Saleh, M.; Feng, X.; Müllen, K.; Fasel, R. Atomically Precise Bottom-up Fabrication of Graphene Nanoribbons. Nature 2010, 466, 470−473. (16) Huang, H.; Wei, D. C.; Sun, J. T.; Wong, S. L.; Feng, Y. P.; Castro Neto, A. H.; Wee, A. T. S. Spatially Resolved Electronic Structures of Atomically Precise Armchair Graphene Nanoribbons. Sci. Rep. 2012, 2, 983. (17) Bieri, M.; Nguyen, M. T.; Gröning, O.; Cai, J.; Treier, M.; AïtMansour, K.; Ruffieux, P.; Pignedoli, C. A.; Passerone, D.; Kastler, M.; Müllen, K.; Fasel, R. Two-Dimensional Polymer Formation on Surfaces: Insight into the Roles of Precursor Mobility and Reactivity. J. Am. Chem. Soc. 2010, 132, 16669−16676. (18) Lipton-Duffin, J. A.; Miwa, J. A.; Kondratenko, M.; Cicoira, F.; Sumpter, B. G.; Meunier, V.; Perepichka, D. F.; Rosei, F. Step-by-Step Growth of Epitaxially Aligned Polythiophene by Surface-Confined Reaction. Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 11200−11204. (19) Fan, Q.; Wang, C.; Han, Y.; Zhu, J.; Hieringer, W.; Kuttner, J.; Hilt, G.; Gottfried, J. M. Surface-Assisted Organic Synthesis of Hyperbenzene Nanotroughs. Angew. Chem., Int. Ed. 2013, 52, 4668− 4672. (20) Chen, Y. C.; de Oteyza, D. G.; Pedramrazi, Z.; Chen, C.; Fischer, F. R.; Crommie, M. F. Tuning the Band Gap of Graphene Nanoribbons Synthesized from Molecular Precursors. ACS Nano 2013, 7, 6123−6128. (21) Zhang, H.; Lin, H.; Sun, K.; Chen, L.; Zagranyarski, Y.; Aghdassi, N.; Duhm, S.; Li, Q.; Zhong, D.; Li, Y.; Müllen, K.; Fuchs, H.; Chi, L. On-Surface Synthesis of Rylene-Type Graphene Nanoribbons. J. Am. Chem. Soc. 2015, 137, 4022−4025. (22) Basagni, A.; Sedona, F.; Pignedoli, C. A.; Cattelan, M.; Nicolas, L.; Casarin, M.; Sambi, M. Molecules−Oligomers−Nanowires− Graphene Nanoribbons: A Bottom-Up Stepwise On-Surface Covalent Synthesis Preserving Long-Range Order. J. Am. Chem. Soc. 2015, 137, 1802−1808. (23) Dienstmaier, J. F.; Gigler, A. M.; Goetz, A. J.; Knochel, P.; Bein, T.; Lyapin, A.; Reichlmaier, S.; Heckl, W. M.; Lackinger, M. Synthesis of Well-Ordered COF Monolayers: Surface Growth of Nanocrystalline Precursors versus Direct On-Surface Polycondensation. ACS Nano 2011, 5, 9737−9745. (24) Zhang, Y. Q.; Kepčija, N.; Kleinschrodt, M.; Diller, K.; Fischer, S.; Papageorgiou, A. C.; Allegretti, F.; Björk, J.; Klyatskaya, S.; Klappenberger, F.; Ruben, M.; Barth, J. V. Homo-Coupling of Terminal Alkynes on Noble Metal Surface. Nat. Commun. 2012, 3, 1286. (25) Eichhorn, J.; Heckl, W. M.; Lackinger, M. On-Surface Polymerization of 1,4-Diethynylbenzene on Cu(111). Chem. Commun. 2013, 49, 2900−2902. (26) Zhou, H.; Liu, J.; Du, S.; Zhang, L.; Li, G.; Zhang, Y.; Tang, B. Z.; Gao, H. J. Direct Visualization of Surface-Assisted TwoDimensional Diyne Polycyclotrimerization. J. Am. Chem. Soc. 2014, 136, 5567−5570. (27) Wiengarten, A.; Seufert, K.; Auwarter, W.; Ecija, D.; Diller, K.; Allegretti, F.; Bischoff, F.; Fischer, S.; Duncan, D. A.; Papageorgiou, A. C.; Klappenberger, F.; Acres, R. G.; Ngo, T. H.; Barth, J. V. SurfaceAssisted Dehydrogenative Homocoupling of Porphine Molecules. J. Am. Chem. Soc. 2014, 136, 9346−9354. (28) Haq, S.; Hanke, F.; Sharp, J.; Persson, M.; Amabilino, D. B.; Raval, R. Versatile Bottom-Up Construction of Diverse Macro-

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsnano.5b07601. Co-assembly structure of TFPB and TAPB and its corresponding dI/dV mapping; NMR spectrum of TFPB (PDF)

AUTHOR INFORMATION Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Author Contributions ⊥

Z. Gong, B. Yang, and H. Lin contributed equally to this work.

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS We acknowledge the Collaborative Innovation Center of Suzhou Nano Science & Technology, the Priority Academic Program Development of Jiangsu Higher Education Institutions. This work was supported by the National Science Foundation of China (No. 91227201, No. 21527805, No. 91545127, and No. 21403149), Major State Basic Research Development Program of China (No. 2014CB932600), and National Science Foundation of Jiangsu Province (No. BK20140305 and No. BK20150305). REFERENCES (1) Geim, A. K.; Novoselov, K. S. The Rise of Graphene. Nat. Mater. 2007, 6, 183−191. (2) Mak, K. F.; Lee, C.; Hone, J.; Shan, J.; Heinz, T. F. Atomically Thin MoS2: A New Direct-Gap Semiconductor. Phys. Rev. Lett. 2010, 105, 136805. (3) Li, L.; Yu, Y.; Ye, G. J.; Ge, Q.; Ou, X.; Wu, H.; Feng, D.; Chen, X. H.; Zhang, Y. Black Phosphorus Field-Effect Transistors. Nat. Nanotechnol. 2014, 9, 372−377. (4) Yang, L. Y. O.; Chang, C. Z.; Liu, S. H.; Wu, C. G.; Yau, S. L. Direct Visualization of An Aniline Admolecule and Its Electropolymerization on Au(111) with in Situ Scanning Tunneling Microscope. J. Am. Chem. Soc. 2007, 129, 8076−8077. (5) Gourdon, A. On-Surface Covalent Coupling in Ultrahigh Vacuum. Angew. Chem., Int. Ed. 2008, 47, 6950−6953. (6) Matena, M.; Riehm, T.; Stöhr, M.; Jung, T. A.; Gade, L. H. Transforming Surface Coordination Polymers into Covalent Surface Polymers: Linked Polycondensed Aromatics through Oligomerization of N-Heterocyclic Carbene Intermediates. Angew. Chem., Int. Ed. 2008, 47, 2414−2417. (7) Zwaneveld, N. A. A.; Pawlak, R.; Abel, M.; Catalin, D.; Gigmes, D.; Bertin, D.; Porte, L. Organized Formation of 2D Extended Covalent Organic Frameworks at Surfaces. J. Am. Chem. Soc. 2008, 130, 6678−6679. (8) Perepichka, D. F.; Rosei, F. Extending Polymer Conjugation into the Second Dimension. Science 2009, 323, 216−217. (9) Li, Q.; Han, C.; Fuentes-Cabrera, M.; Terrones, H.; Sumpter, B. G.; Lu, W.; Bernholc, J.; Yi, J.; Gai, Z.; Baddorf, A. P.; Maksymovych, P.; Pan, M. Electronic Control over Attachment and Self-Assembly of Alkyne Groups on Gold. ACS Nano 2012, 6, 9267−9275. (10) Li, Q.; Owens, J. R.; Han, C.; Sumpter, B. G.; Lu, W.; Bernholc, J.; Meunier, V.; Maksymovych, P.; Fuentes-Cabrera, M.; Pan, M. SelfOrganized and Cu-Coordinated Surface Linear Polymerization. Sci. Rep. 2013, 3, 2102−2108. (11) Lin, T.; Shang, X. S.; Adisoejoso, J.; Liu, P. N.; Lin, N. Steering On-Surface Polymerization with Metal-Directed Template. J. Am. Chem. Soc. 2013, 135, 3576−3582. G


Article

ACS Nano molecules on a Surface Observed by Scanning Tunneling Microscopy. ACS Nano 2014, 8, 8856−8870. (29) Sun, Q.; Cai, L.; Ding, Y.; Xie, L.; Zhang, C.; Tan, Q.; Xu, W. Dehydrogenative Homocoupling of Terminal Alkenes on Copper Surfaces: A Route to Dienes. Angew. Chem., Int. Ed. 2015, 54, 4549− 4552. (30) Zhong, D.; Franke, J. H.; Podiyanachari, S. K.; Blömker, T.; Zhang, H.; Kehr, G.; Erker, G.; Fuchs, H.; Chi, L. Linear Alkane Polymerization on a Gold Surface. Science 2011, 334, 213−216. (31) Weigelt, S.; Busse, C.; Bombis, C.; Knudsen, M. M.; Gothelf, K. V.; Lægsgaard, E.; Besenbacher, F.; Linderoth, T. R. Surface Synthesis of 2D Branched Polymer Nanostructures. Angew. Chem., Int. Ed. 2008, 47, 4406−4410. (32) Yang, B.; Björk, J.; Lin, H.; Zhang, X.; Zhang, H.; Li, Y.; Fan, J.; Li, Q.; Chi, L. Synthesis of Surface Covalent Organic Frameworks via Dimerization and Cyclotrimerization of Acetyls. J. Am. Chem. Soc. 2015, 137, 4904−4907. (33) Weigelt, S.; Busse, C.; Bombis, C.; Knudsen, M. M.; Gothelf, K. V.; Strunskus, T.; Wöll, C.; Dahlbom, M.; Hammer, B.; Lægsgaard, E.; Besenbacher, F.; Linderoth, T. R. Covalent Interlinking of an Aldehyde and an Amine on a Au(111) Surface in Ultrahigh Vacuum. Angew. Chem., Int. Ed. 2007, 46, 9227−9230. (34) Tanoue, R.; Higuchi, R.; Enoki, N.; Miyasato, Y.; Uemura, S.; Kimizuka, N.; Stieg, A. Z.; Gimzewski, J. K.; Kunitake, M. Thermodynamically Controlled Self-Assembly of Covalent Nanoarchitectures in Aqueous Solution. ACS Nano 2011, 5, 3923−3929. (35) Liu, X. H.; Guan, C. Z.; Ding, S. Y.; Wang, W.; Yan, H. J.; Wang, D.; Wan, L. J. On-Surface Synthesis of Single-Layered TwoDimensional Covalent Organic Frameworks via Solid−Vapor Interface Reactions. J. Am. Chem. Soc. 2013, 135, 10470−10474. (36) Xu, L.; Zhou, X.; Tian, W. Q.; Gao, T.; Zhang, Y. F.; Lei, S.; Liu, Z. F. Surface-Confined Single-Layer Covalent Organic Framework on Single-Layer Graphene Grown on Copper Foil. Angew. Chem., Int. Ed. 2014, 53, 9564−9568. (37) Liu, X. H.; Guan, C. Z.; Wang, D.; Wan, L. J. Graphene-Like Single-Layered Covalent Organic Frameworks: Synthesis Strategies and Application Prospects. Adv. Mater. 2014, 26, 6912−6920. (38) Liu, X. H.; Guan, C. Z.; Zheng, Q. N.; Wang, D.; Wan, L. J. Molecular Engineering of Schiff-Base Linked Covalent Polymers with Diverse Topologies by Gas-Solid Interface Reaction. J. Chem. Phys. 2015, 142, 101905. (39) Tanoue, R.; Higuchi, R.; Ikebe, K.; Uemura, S.; Kimizuka, N.; Stieg, A. Z.; Gimzewski, J. K.; Kunitake, M. In Situ STM Investigation of Aromatic Poly(Azomethine) Arrays Constructed by “on-Site” Equilibrium Polymerization. Langmuir 2012, 28, 13844−13851. (40) Jensen, S.; Greenwood, J.; Früchtl, H. A.; Baddeley, C. J. STM Investigation on the Formation of Oligoamides on Au(111) by Surface-Confined Reactions of Melamine with Trimesoyl Chloride. J. Phys. Chem. C 2011, 115, 8630−8636. (41) Klimeš, J.; Bowler, D. R.; Michaelides, A. Van der Waals Density Functionals Applied to Solids. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 83, 195131. (42) Dion, M.; Rydberg, H.; Schröder, E.; Langreth, D. C.; Lundqvist, B. I. Van der Waals Density Functional for General Geometries. Phys. Rev. Lett. 2004, 92, 246401.

H


Structural Variation in Surface-Supported Synthesis by Adjusting the

Recommend Documents