Modulation of Coordinate Bonds in Hydrogen-Bonded Trimesic Acid

May 25, 2016 - The STM observations demonstrate that the self-assembled hydrogen-bonded molecular networks of trimesic acid (TMA) have been significan...
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Modulation of Coordinate Bonds in Hydrogen-Bonded Trimesic Acid Molecular Networks on Highly Ordered Pyrolytic Graphite Surface Wei Li,†,§ Jing Jin,† Xinli Leng,† Yan Lu,† Xiaoqing Liu,*,† and Li Wang*,†,‡ †

Department of Physics and ‡Nanoscale Science and Technology Laboratory, Institute for Advanced Study, Nanchang University, Nanchang 330031, P. R. China § Department of Science, Nanchang Institute of Technology, Nanchang 330099, P. R. China S Supporting Information *

ABSTRACT: The modulation effects of metal nitrites on the hydrogen-bonded supramolecular structure of trimesic acid on a graphite surface have been investigated at the liquid−solid interface by scanning tunneling microscopy (STM). The STM observations demonstrate that the self-assembled hydrogenbonded molecular networks of trimesic acid (TMA) have been significantly transformed after the introduction of various metal nitrites. It is found that for the nitrite containing full orbital metals (AgNO3 and Zn(NO3)2), the pristine nitrite molecules are directly embedded into the pores within the TMA networks. In contrast, for the nitrite with vacant orbital metals (Cu(NO3)2, Mn(NO3)2 and Fe(NO3)3), the metal−organic coordination networks with various structures are formed due to the incorporations of the metal ions.

1. INTRODUCTION Surface-assisted self-assembled nanoporous and metal−organic networks are becoming one of the most rapidly developing fields in chemical and materials sciences and emerging as an important family of porous materials.1−4 The inclusion of guest species (e.g., ions or molecules) into host systems by means of noncovalent bonding is that the guest components are bound to the hosts reversibly by weak interactions, such as electrostatic forces, hydrogen bonds,5,6 van der Waals forces,7−9 or metal−ligand coordination.10,11 A variety of surfacesupported molecular network structures have been made available by the general application of a method of surfaceassisted metal coordination to metal centers and aromatic poly(carboxylic acid)s on solid surfaces.12,13 The self-assembly of molecules on surfaces is governed by a combination of molecule−substrate interactions and multiple intermolecular interactions. Usually, the structures of the metal−organic coordination networks are determined by the properties of the ligands (e.g., donor atoms and their spatial arrangement or steric crowding) and the electronic characteristics of the metal ions (e.g., the orbitals involved and the ionization energies). However, under 2D conditions, the realization of a given coordination algorithm might be altered by the presence of the solid substrate, which results in a deviation in coordination geometry as compared with its threedimensional situation. Such a deviation can be attributed to charge-transfer or screening effects and the strict 2D confinement of ligands and metal centers imposed by the substrate, which substantially influences the characteristics of metal− ligand bonding within the 2D coordination network. As a result © XXXX American Chemical Society

of this phenomenon, the investigation of self-assembly processes that are assisted by the underlying surface is an approach of special interest.14,15 The character of the metal− organic coordination network is worth investigating in itself and can give further insight into purely surface-based ways of exploiting real single-molecule information.16,17 The use of metal ions (clusters) to modify the structure of supramolecular networks has recently been demonstrated in 2D molecular systems.18−20 In this article, metal nitrates with different valence state metal ions are used as functional guest molecules to modify the hydrogen-bonded supramolecular network of TMA (as shown in Figure 1). Depending on the valence states of the metal ions, multidimensional host−guest architectures with the incorporation of either pristine nitrite molecules (AgNO3 and Zn(NO3)2) or metal ions (Cu2+, Mn2+, and Fe3+) are formed on HOPG surface.

2. EXPERIMENTAL SECTION Sample Preparation. All chemicals for scanning tunneling microscopy (STM) experiments were purchased from Tokyo Chemical Industry (TCI) and used without further purification. Stock solutions of 30 mL each of TMA and metal nitrates were prepared by dissolving these reagents in n-nonanoic acid at different concentrations and heated to 80 °C in a water bath. The mole ratio of TMA to metal nitrate in the final product was controlled both by the concentrations and the volumes that Received: April 4, 2016 Revised: May 25, 2016

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adopted and the van der Waals interaction was considered with the optB86b-vdW method.24 Four layers of graphite separated by 2.0 nm vacuum range were employed to represent graphite substrate. The 1.62 × 1.62 × 3.09 nm3 slab model was constructed in the calculations of TMA overlayer with the vertical AgNO3 and the horizontal AgNO3. A 1 × 1 × 1 k-mesh was adopted for the geometry optimization. During the geometry optimization processes, all atoms except those of within the bottom one layer of graphite were fully relaxed until the residual force per atom was less than 0.01 eV/Å.

3. RESULTS AND DISCUSSION STM images show that TMA molecules form a uniform monolayer on HOPG with molecules lying flat on the surface. Interestingly, polymorphic self-assembly of TMA molecules appears to occur on HOPG. Figure 2a shows a typical porous chicken-wire structure of TMA on HOPG. The bright spots represent the TMA molecules; it is obvious that the groups of six TMA molecules form a hexagonal network, which is in good agreement with the previous reports.25−27 This chicken-wire structure is composed of hexagon rings of TMA molecules that underwent self-assembly via purely dimeric hydrogen-bonded motifs, and the corresponding molecular model is presented in Figure 2b. The open pores within the chicken-wire network have a diameter of ∼1.1 nm and a periodicity of ∼1.7 nm, which provides nanotemplates to host large guest molecules. When the heated n-nonanoic acid containing TMA and AgNO3 (the concentrations of TMA and AgNO3 were 1.7 × 10−4 and 8.6 × 10−5 M, respectively; the molar ratio was adjusted to 2:1) was deposited on an HOPG surface, a selfassembled structure similar to the chicken-wire structure of TMA is found by STM. However, STM observations clearly show that a bright sphere-shaped spot is embedded into each of the dark pores surrounded by six bright dots in Figure 3a. The high-resolution STM image in Figure 3b demonstrates that six bright spots represent six TMA molecules connected to each other by a pair of hydrogen bonds (O···H−O), and one large darker feature locates at the center of the hexagon pore formed by TMA. Since Ag+ ion cannot form a complex with the carboxyl groups of TMA due to the lack of vacant orbital, it is believed that these large bright spots actually represent pristine AgNO3 molecules locating in the pores. The driving force for the formation of the cocrystal structure may be attributed to the intermolecular hydrogen bonds between TMA and AgNO3. Once the concentration of TMA was adjusted to the same as AgNO3 (1.7 × 10−4 M), there are two spots in the center of a

Figure 1. Schematic representation of three different approaches to generating supramolecular nanostructures on (HOPG) surface (hexagons: TMA molecules; circles: metal nitrates): (A) surfaceassisted self-assembly via hydrogen-bond formation, (B) metal nitrate molecules in a cavity of self-assembled supramolecular architectures, and (C) surface-assisted self-assembly by formation of coordinate bonds.

were deposited. STM samples were prepared by dropping about 0.4 μL of the heated solutions on a freshly cleaved highly oriented pyrolytic graphite (HOPG, grade SPI-2) substrate. Then, the samples were kept at room temperature for about 3 h. After that, the samples were again investigated by STM at the liquid/solid interface. STM Measurements. The STM measurements were performed under atmospheric conditions. All the STM images were acquired on a Pico-SPM (Molecular Imaging, Agilent Technology) scanning tunneling microscope operating in constant-current mode under ambient conditions of about 25 °C. STM tips were made by cutting Pt/Ir (80/20) wire (California Fine Wire Co., Grover Beach, CA). Images were typically obtained at sample biases of −0.9 V to −0.3 V and tunneling currents of 200−700 pA. Scan rates were typically 4.86 lines/s. All STM images presented in this study were extracted from raw data files using Pico Image Basic 6.2 program (Agilent, USA) and all samples to test repeatability and to make sure that there were no artifacts caused by interactions between the tip and the sample. The drift is calibrated using the underlying graphite lattice as a reference. Constructed and Optimization Method. Density functional theory (DFT) as implemented in the Vienna Ab initio Simulation Package (VASP) was applied using the PBE generalized-gradient exchange and correlation functional.21−23 A plane-wave basis set with a kinetic energy cutoff of 400 eV is

Figure 2. STM images of the assembled structure of TMA monolayers on a graphite surface: (a) close-packed structure (I = 0.66 nA, V = 0.1 V); (b) proposed molecular model of the close-packed structure. (c) Schematic diagram of TMA model. The red dashed lines indicate O···H−O H-bonds. B

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Figure 3. (a) STM image of TMA/AgNO3 (TMA:AgNO3 = 2:1) self-assembled network on graphite surface (I = 0.32 nA, V = −0.9 V). (b) Highresolution STM image of 2:1 TMA/AgNO3 network (I = 0.38 nA, V = −0.74 V). (c) Proposed molecular model of 2:1 TMA/AgNO3 network. (d) STM image of TMA/AgNO3 (TMA:AgNO3 = 1:1) self-assembled network on graphite surface (I = 0.28 nA, V = −0.83 V). (e) High-resolution STM image of 1:1 TMA/AgNO3 network (I = 0.33 nA, V = −0.78 V). (f) Proposed molecular model of 1:1 TMA/AgNO3 network.

hexagonal pore in Figure 3d. Careful inspections on the highresolution image in Figure 3e reveal that these two spots in fact stand up on the surface instead of lying down. Our density functional theory simulations have also confirmed that this configuration has a minimum adsorption energy on the HOPG surface. Figure 3f shows the proposed molecular model based on the STM observations. Such unusual configuration of AgNO3 within the pores might be caused by the spatial confinement effect and the dipole interactions between two AgNO3 molecules. Figure 4a shows the self-assembled structure of a mixture of TMA and Zn(NO3)2 with concentration 1.5 × 10−5 M on HOPG. The chicken-wire structure formed by TMA molecules is dominant on the surface although some defects and domains highlighted by the red circles and green rectangles, respectively, are present. It is worth noting that some pores within the TMA chicken-wire structure highlighted by blue circles are filled by large bright features. With the increase of the Zn(NO3)2 concentration (see Table 1 and Figure S1), the pores are gradually filled up until all the pores are full of these bright features, as shown in Figure 4b. The high-resolution STM image in Figure 4d clearly reveals that all the bright spherical spots are indeed surrounded by six TMA molecules. Therefore, these bright spherical spots are believed to represent Zn(NO3)2 since the zinc ions do not have any vacant orbital as the Ag ions do. Careful examinations to these large bright spots demonstrate that that these features are in fact brighter on the sides and darker in the middle. Based on the observations, Figure 4c gives the proposed molecular model in which the Zn(NO3)2 molecules are orientated with the Zn ion side down and the nitrate side up in the pore via stronger multiple hydrogen-bonded interactions. Such multicomponent selfassembled structures are beneficial for reducing surface free energy at liquid−solid interfaces.28−30

Figure 4. (a) STM image of the structure of TMA with a few Zn(NO3)2 molecules on the graphite surface (I = 0.14 nA, V = −0.56 V). (b) STM image of TMA/Zn(NO3)2 network with a higher Zn(NO3)2 concentration (I = 0.18 nA, V = −0.77 V). (c) Proposed molecular model of TMA/Zn(NO3)2 network structure. (d) Highresolution STM image of TMA/Zn(NO3)2 network (I = 0.12 nA, V = −0.76 V). The yellow hexagon highlights functionalized nanopores formed by a cluster of six TMA molecules; the blue circle highlights a Zn(NO3)2 molecule.

In order to obtain metal−organic coordination networks, metal nitrites with vacant orbital metal ions were adopted to codeposit with TMA on HOPG. Figure 5a gives the STM image of a mixture of TMA and Cu(NO3)2 molecules with concentrations 1.7 × 10−4 and 4.1 × 10−5 M, just as a ratio of C

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features are attributed to the complex formed by TMA molecules and Cu ions via metal coordination bonds, as shown in Figure 5d. A mononuclear Cu center is coordinated with two carboxylic groups within the neighboring TMA molecules, and the two carboxylic ligands point directly toward the central Cu; moreover, these building blocks are connected in lines by hydrogen bonds. Similar metal coordination bond network can be also achieved by depositing a mixture of TMA and Mn(NO3)2 on graphite surface, as shown in Figure 6a. It is observed that some conglobations highlighted by blue circles were considered to be the polymers of the reaction. The measured unit cell parameters for this Z-type line structure are a = 3.6 ± 0.1 nm, b = 3.8 ± 0.1 nm, and α = 66 + 1°. Previously, it has been reported that Mn2+ can be coordinated by a carboxylic group.31 Thus, it reveals that one manganese(II) ion is trapped within two carboxylic groups. The high-resolution STM in Figure 6b shows that the big bright spots highlighted by blue circles are attributed to TMA molecules, and the small spots between the big bright spots highlighted by red circles represent Mn ions, indicating that a mononuclear Mn is coordinated by two carboxylic groups of TMA. From the proposed model in Figure 6c, the length of Mn−O bond is 2.1 ± 0.1 Å and the angle of O−Mn−O is 135°, which is consistent with the previous reports.31 Previous studies demonstrate that carboxyl groups can be bound to Fe3+ on a metal surface in an ultrahigh vacuum.32 Figure 7a is an STM image of the structure of TMA and Fe(NO3)3. When the concentrations of TMA and Fe(NO3)3 are adjusted to the same (1.7 × 10−4 M), it is obvious that this structure is completely different from the chicken-wire structure formed by only TMA molecules. The high-resolution STM topography image (Figure 7b) reveals that one bright dot is surrounded by three bright spherical structures with a local 3fold symmetry. As the proposed model in Figure 7c, the central small bright spot is attributed to Fe3+, and the three bright spherical structures are TMA molecules. In this model of TMA/Fe3+ dimers, three carboxyl groups linked with one iron(III) ion through metal−ligand coordination. Once the metal−ligand process is limited to the 2D surface, a dramatically coordinated behavior could happen. Such threecoordinated structures are beneficial to reduce the surface free energy at liquid−solid interfaces. The introduction of KSCN solution into the TMA−Fe3+ network causes a completely different assembled structure in Figure S2, further confirming that the TMA−Fe3+ network is indeed dominated by the coordination bonds between TMA molecules and the Fe ions.

Table 1. Relationship between Zn(NO3)2 Concentrations and the Rates of Filling Pores Zn(NO3)2 concn (M) rates of filling pores (%)

1.5 × 10−5

3.8 × 10−5

1.2 × 10−4

1.7 × 10−4

15

32

78

100

Figure 5. (a) STM image of structures I and II coadsorbed on the graphite surface (I = 0.18 nA, V = −0.72 V). The random lines indicate phase-separated boundaries between Cu-coordinated and TMA selfassembled networks. (b) High-resolution STM image of Cucoordinated and TMA self-assembled networks (I = 0.13 nA, V = −0.79 V). (c) High-resolution STM topography of Cu-coordinated line network (I = 0.17 nA, V = −0.69 V). (d) Proposed molecular model of the dimeric Cu(TMA)2 network structure. Cu atoms are represented by brown spheres.

4:1 on the HOPG surface. As shown in Figure 5a, two distinct structures labeled as I and II can be observed on the same surface area with the green lines as the indicators of phaseseparated boundaries. Close examination in Figure 5b reveals that the structure I is actually the chicken-wire structure formed by TMA molecules, and the symmetry of the structure II is C2 rather C6 for chicken-wire structure. The measured unit cell parameters for this new structure are a = 1.5 ± 0.1 nm, b = 2.3 ± 0.1 nm, and α = 82 ± 1°. The high-resolution STM image in Figure 5c shows that the building block for this new structure is a rectangular-shape feature. Since this new structure emerges after the introduction of Cu(NO3)2, these rectangular-shape

Figure 6. (a) STM image of the Mn-coordinated line structure on graphite surface (I = 0.62 nA, V = −0.5 V); blue circle highlights the polymers. (b) High-resolution STM topography of Mn-coordinated line structure (I = 0.62 nA, V = −0.5 V). (c) Schematic diagram of the [Mn(TMA)2]2+ model. D

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ACKNOWLEDGMENTS This work was financially supported by Natural Science Foundation of China (Grants 61474059 and U1432129) and National Key Basic Research Program of China (2013CB934200). L.W. acknowledges the financial support from Jiangxi Provincial “Ganpo Talents 555 Projects”.

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Figure 7. (a) STM topography image of the trimeric Fe(TMA)3 network on the HOPG surface (I = 0.22 nA, V = 0.72 V). (b) Highresolution STM image of the trimeric Fe(TMA)3 network (I = 0.11 nA, V = 0.64 V). (c) Proposed molecular model of the trimeric Fe(TMA)3 network structure. Fe atoms are represented by blue spheres. (d) Schematic diagram of the [Fe(TMA)3]3+ model. The red dashed lines indicate O···H−O hydrogen bonds, and the blue lines represent metal−ligand coordination between Fe3+ and the three carboxyl groups of the three TMA molecules.

4. CONCLUSIONS In summary, the self-assembled hydrogen-bonded molecular networks of trimesic acid have been significantly transformed after the introduction of various metal nitrites. It is found that for the nitrite containing full orbital metals (AgNO3 and Zn(NO 3)2 ), the pristine nitrite molecules are directly embedded into the pores within the TMA networks. The pores within the self-assembled structure of TMA act as selective adsorption sites for the guest molecules. However, for the nitrite with vacant orbital metals (Cu(NO3)2, Mn(NO3)2, and Fe(NO3)3), the metal ions can incorporate with TMA molecule via metal−organic coordination to form new structures, and the type of the structure is greatly affected by the number of the metal−ligand coordination bond.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcc.6b03434. Report of the relationship between the concentrations of Zn(NO3)2 and the filling rates of the pores as well as the formation of Fe/TMA/SCN− network on the HOPG surface (PDF)

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REFERENCES

(1) Mason, J. A.; Veenstra, M.; Long, J. R. Evaluating metal-organic frameworks for natural gas storage. Chem. Sci. 2014, 5, 32−51. (2) Li, Y. B.; Zhao, K. Q.; Yang, Y. L.; Deng, K.; Zeng, Q. D.; Wang, C. Functionalization of two-component molecular networks: recognition of Fe3+. Nanoscale 2012, 4, 148−151. (3) Shen, J. H.; Zhu, Y. H.; Yang, X. L.; Li, C. Z. Graphene quantum dots: emergent nanolights for bioimaging, sensors, catalysis and photovoltaic devices. Chem. Commun. 2012, 48, 3686−3699. (4) Lin, Z. J.; Lu, J.; Hong, M. C.; Cao, R. Tuning the structure and function of metal-organic frameworks via liner design. Chem. Soc. Rev. 2014, 43, 5867−5895. (5) Griessl, S.; Lackinger, M.; Edelwirth, M.; Hietschold, M.; Heckl, W. M. Self-assembled two-dimensional molecular host-guest architectures from trimesic acid. Single Mol. 2002, 3, 25−31. (6) Chen, F.; Chen, X.; Liu, L. C.; Song, X.; Liu, S. Y.; Liu, J.; Wang, H. P.; Cai, Y. X.; Liu, X. Q.; Pan, H. B.; Zhu, J. F.; Wang, L. Chiral recognition of Zinc Phthalocyanine on Cu(100) surface. Appl. Phys. Lett. 2012, 100, 081602−081604. (7) Wang, L.; Kong, H. H.; Chen, X.; Du, X. L.; Chen, F.; Liu, X. Q.; Wang, H. M. Conformation-induced self-assembly of rubrene on Au(111) surface. Appl. Phys. Lett. 2009, 95, 093102−093103. (8) Spillmann, H.; Kiebele, A.; Stohr, M.; Jung, T. A.; Bonifazi, D.; Cheng, F.; Diederich, F. A two-dimensional porphyrin-based porous network featuring communication cavities. Adv. Mater. 2006, 18, 275− 279. (9) Furukawa, S.; Tahara, K.; De Schryver, F. C.; Van derAuweraer, M.; Tobe, Y.; De Feyter, S. Structural transformation of a twodimensional molecular network in response to selective guest inclusion. Angew. Chem., Int. Ed. 2007, 46, 2831−2834. (10) Stepanow, S.; Lin, N.; Payer, D.; Schilckum, U.; Klappenberger, F.; Zoppellaro, G.; Ruben, M.; Brune, H.; Brune, J. V.; Barth, J. V.; Kern, K. Surface-assisted assembly of 2D metal-organic networks that exhibit unusual threefold coordination symmetry. Angew. Chem., Int. Ed. 2007, 46, 710−713. (11) Xiang, F. F.; Lu, Y.; Li, C.; Song, X.; Liu, X. Q.; Wang, Z. P.; Liu, J.; Dong, M. D.; Wang, L. Cyclotrimerization-induced chiral supramolecular structures of 4-Ethynyltriphenylamine on Au(111) surface. Chem. - Eur. J. 2015, 21, 12978−12983. (12) Classen, T.; Fratesi, G.; Costantini, G.; Fabris, S.; Stadler, F. L.; Kim, C.; De Gironcoli, S.; Baroni, S.; Kern, K. Templated growth of metal-organic coordination chains at surface. Angew. Chem., Int. Ed. 2005, 44, 6142−6145. (13) Xiang, F. F.; Li, C.; Wang, Z. P.; Liu, X. Q.; Jiang, D. F.; Leng, X. L.; Ling, J.; Wang, L. Direct observation of copper-induced metalation of 5,15-diphenyporphyrin on Au(111) by scanning tunneling microscopy. Surf. Sci. 2015, 633, 46−52. (14) Barth, J. V.; Costantini, G.; Kern, K. Engineering atomic and molecular nanostructures at surface. Nature 2005, 437, 671−679. (15) Kurth, D. G.; Severin, N.; Rabe, J. P. Perfectly straight nanostructures of metallosupramolecular coordination-polyelectrolyte amphiphile complexes on graphite. Angew. Chem., Int. Ed. 2002, 41, 3681−3683. (16) Theobald, J. A.; Oxtoby, N. S.; Phillips, M. A.; Champness, N. R.; Beton, P. H. Controlling molecular deposition and layer structure with supramolecular surface assemblies. Nature 2003, 424, 1029− 1031. (17) Wang, L.; Kong, H. H.; Song, X.; Liu, X. Q.; Wang, H. M. Chiral supramolecular self-assembly of rubrene. Phys. Chem. Chem. Phys. 2010, 12, 14682−14685.

AUTHOR INFORMATION

Corresponding Authors

*Tel 86-791-83860108; e-mail [email protected] (X.L.). *Tel 86-791-83860108; e-mail [email protected] (L.W.). Notes

The authors declare no competing financial interest. E

DOI: 10.1021/acs.jpcc.6b03434 J. Phys. Chem. C XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry C (18) Stepanow, S.; Lin, N.; Payer, D.; Schlickum, U.; Klappenberger, F.; Zoppellaro, G.; Ruben, M.; Brune, H.; Barth, J. V.; Kern, K. Surface-assisted assembly of 2D metal organic networks that exhibit unusual three-fold coordination symmetry. Angew. Chem., Int. Ed. 2007, 46, 710−713. (19) Vidal, F.; Delvigne, E.; Stepanow, S.; Lin, N.; Barth, J. V.; Kern, K. Chiral phase transition in two-dimensional supramolecular assemblies of prochiral molecules. J. Am. Chem. Soc. 2005, 127, 10101−10106. (20) Nath, K. G.; Ivasenko, O.; Miwa, J. A.; Dang, H.; Wuest, J. D.; Nanci, A.; Perepichka, D. F.; Rosei, F. Rational modulation of the periodicity in linear hydrogen-bonded assemblies of trimesic acid on surfaces. J. Am. Chem. Soc. 2006, 128, 4212−4213. (21) Kresse, G.; Furthmuller, J. Efficiency of Ab-Initio total energy calculations for metals and semiconductors using a plane-wave basis ste. Comput. Mater. Sci. 1996, 6, 15−50. (22) Kresse, G.; Furthmuller, J. Efficient iterative schemes for ab initio total-energy calculation using a plane-wave basis set. Phys. Rev. B: Condens. Matter Mater. Phys. 1996, 54, 11169−11186. (23) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 1996, 77, 3865. (24) Klimes, J.; Bowler, D. R.; Michaelides, A. Van der Waals density functional applied to solids. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 83, 195131/1−195131/13. (25) Korolkov, V. V.; Allen, S.; Roberts, C. J.; Tendler, S. J. B. Green chemistry approach to surface decoration: trimesic acid self-assembly on HOPG. J. Phys. Chem. C 2012, 116, 11519−11525. (26) Lackinger, M.; Griessl, S.; Heckl, W. M.; Hietschold, M.; Flynn, G. W. Self-assembly of trimesic acid at the liquid-solid interface- a study of solvent-induced polymorphism. Langmuir 2005, 21, 4984− 4988. (27) Zhu, L.; Xu, X. M.; Wang, Y.; Liu, S. Y.; Ling, J.; Liu, L. C.; Wei, S.; Cai, F.; Wang, Z. P.; Liu, X. Q.; Wang, L. Hydrong-bonded structures of trimesic and melamine on highly oriented pyrolytic graphite. Surf. Rev. Lett. 2014, 21, 1450035/1−1450035/7. (28) Seitsonen, A. P.; Lingenfelder, M. A.; Spillmann, H.; Dmitriev, A.; Stepanow, S.; Lin, N.; Kern, K.; Barth, J. V. Density functional theory analysis of carboxylate-bridged di-iron units in two-dimensional metal-organic grids. J. Am. Chem. Soc. 2006, 128, 5634−5635. (29) Li, Y. B.; Liu, C. H.; Xie, Y. Z.; Li, X.; Fan, X. L.; Yuan, L. H.; Zeng, Q. D. Single-molecule observation of the K+-induced switching of valinomycin within a template network. Chem. Commun. 2013, 49, 9021−9023. (30) Li, Y. B.; Deng, K.; Wu, X. K.; Lei, S. B.; Zhao, K. Q.; Yang, Y. L.; Zeng, Q. D.; Wang, C. Molecular arrays formed in anisotropically rearranged supramolecular network with molecular substitutional asymmetry. J. Mater. Chem. 2010, 20, 9100−9103. (31) Katsuda, M.; Mitani, M.; Yoshioka, Y. A B3LYP study on electronic structures of [(X)m Mn(μ-oxo)2 Mn(Y)n]q+ (X, Y = H2O, OH and O) as a Mn cluster model of OEC. J. Biophys. Chem. 2012, 3, 111−126. (32) Lin, N.; Stepanow, S.; Vidal, F.; Barth, J. V.; Kern, K. Manipulating 2D metal-organic networks with diiron units via ligand control. Chem. Commun. 2005, 41, 1681−1683.

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