Chiral Self-Assembly of Nonplanar 10,10â²-Dibromo-9,9â²-bianthryl

Subscriber access provided by University of Newcastle, Australia

Article

Chiral Self-assembly of Nonplanar 10,10’Dibromo-9,9’-Bianthryl Molecules on Ag(111) Yixian Shen, Guo Tian, Han Huang, Yanwei He, Qiliang Xie, Fei Song, Yunhao Lu, Pingshan Wang, and Yongli Gao Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b00218 • Publication Date (Web): 05 Mar 2017 Downloaded from http://pubs.acs.org on March 5, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Langmuir is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Chiral Self-assembly of Nonplanar 10,10’Dibromo-9,9’-Bianthryl Molecules on Ag(111) Yixian Shen1,2, Guo Tian1, Han Huang1,3*, Yanwei He1, Qiliang Xie1, Fei Song4, Yunhao Lu5, Pingshan Wang2, Yongli Gao1,3,6 1

Hunan Key Laboratory of Super-microstructure and Ultrafast Process, College of

Physics and Electronics, Central South University, Changsha 410083, P. R. China 2

College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China

3

State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, P. R. China

4

Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics,

Chinese Academy of Sciences, 239 Zhangheng Road, Pudong New Area, Shanghai 201204, P. R. China 5

College of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China

1

ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

6

Page 2 of 30

Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA

Key Words: Self-assembly, LT-STM, DBBA, Chirality

ABSTRACT

We report on low-temperature scanning tunneling microscopy (STM) measurements on the self-assembly of nonplanar 10,10’-dibromo-9,9’-bianthryl (DBBA) molecules on Ag(111) combined with density functional theories (DFT) calculations. DBBA molecules have two enantiomorphous adsorption configurations, from which more chiral structures can be formed. At a low coverage (0.4 ML), DBBA forms racemic −

net-like islands consisting of molecular chains along < 1 2 3 >Ag. Moreover, the gliding between molecular chains gives rise to chiral windmill-like patterns in the islands. At 0.8 ML DBBA forms racemic row phase as well as homochiral hexamer phase. The difference in molecular appearance in STM images and DFT calculations reveal a decrease in the dihedral angle of DBBA, which implies an enhancement in the intermolecular interactions via CH…π and halogen bonds. The transition from a racemic packing mode to a homochiral one suggests that the suitability of steric configurations is dominant in close packing mode under enhanced intermolecular interactions.

2


Page 3 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

INTRODUCTION Chirality is simply a geometric property where the mirror transformation of an object is a non-identity operation, i.e. the object and its mirror image are nonsuperimposable by any translation or rotation.1 Chiral structures have wide applications in enantioselective catalysis,2,3 non-linear optical devices,4-7 sensors,8,9 smart coatings10,11 and chiral separations12-14. Not only chiral molecules15 but also achiral molecules16 can form chiral arrangements on a solid surface because of the surface-induced additional symmetry restrictions, such as no inversion center and only perpendicular reflection symmetry planes.17 A classic example is the selfassembly of achiral 1-nitronaphthalene molecules on Au(111) into chiral decamers.18 The self-assembly of nonplanar molecules is more complex than the planar ones, because the coupling motif and the assembled pattern are influenced by steric configurations as well as molecular interactions.19,20 Self-assembly of nonplanar molecules like hexa-cata-hexabenzocoronene,19 2,3,5,6-Tetra(2’-pyridyl)pyrazine,20 rubrene,21 and 6-nitrospiropyran22 were investigated by low temperature scanning tunneling microscopy (LT-STM) in the last decade. All of these molecules have a relatively nonflexible structure, which means the assembled pattern is fixed under certain coverage. The assembly process and intermediate state are unrevealed.

3


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 1. (a) Ball-and-stick model of DBBA. (b) Top view of two mirror symmetric DBBA molecules on Ag(111). The up-tilted phenyl groups are colored in yellow. (c) Side view of the most stable adsorption position of DBBA on Ag(111) surface calculated by DFT. The dihedral angle faced to substrate is 128°. Top view of the most stable adsorption position is indicated by (e) that DBBA adsorbs on top site of −

surface Ag atom with C-Br bond along Ag. (d, e) Side and top views of the 0.0002 Å−3 differential charge density isosurface showing charge transfer between substrate and isolated DBBA molecule. The electron accumulation/depletion region is indicated by yellow/blue color.

10,10’-dibromo-9,9’-bianthryl (DBBA, Figure 1a) molecule has drawn great attention due to its ability to fabricate armchair graphene nanoribbons (AGNRs) with atomically precise edges on noble metal surface.23-28 It has a nonplanar configuration due to the steric hindrance between H atoms. It belongs to D2 point group for having 4


Page 4 of 30

Page 5 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

three twofold rotation axis,20 but adsorbing to a solid surface confines the rotation and thus arises two mirror symmetric adsorption configurations (Figure 1b). The chirality of DBBA can be recognized by the location of up-tilted phenyl groups. The DBBA with up-tilted top left and low right phenyl groups is designated as L-DBBA and the other one as R-DBBA. Although it has a twisted chiral configuration similar to rubrene, its chirality is invertible by rolling odd quarters around the C-Br axis on surface. Besides, the rotatable central C-C bond makes the molecular dihedral angle sensitive to the external force. The signature of increasing in external force decreasing in dihedral angle - expresses as a higher packing density in STM image. These properties make it practicable to investigate the intermediate state and the effect of the equilibrium of intermolecular interactions and molecule-substrate interactions on self-assembly on surface. Herein we present the self-assembly behaviors of nonplanar DBBA molecules on Ag(111) by LT-STM and density functional theories (DFT) calculations. At 0.4 ML DBBA forms racemic net-like islands, while at 0.8 ML it forms racemic row phase as well as homochiral hexamer phase. Here, 1 ML corresponds to 21 Ag atoms per DBBA molecule. All of the patterns have chirality, which has not been discovered on Au(111).23,26 A decrease in molecular dihedral angle is deduced from STM images, suggesting enhanced intermolecular interactions. At last, a packing mode transition from racemic to homochiral and its intermediate phase under high packing density,

5


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

which arise from the rebalance between the enhanced intermolecular interactions and the reduced molecule-substrate interactions, are discussed.

EXPERIMENTAL METHODS All the experiments were carried out in a custom-built multichamber ultra-highvacuum system housing a Quantech LT-STM (Ultrascan LT-100) with base pressure better than 1.0 × 10−10 mbar.29 The clean Ag(111) surface was achieved in situ by several cycles of Ar+ sputtering and subsequent annealing at ∼700 K. The sample’s cleanliness and surface structure were verified by LT-STM and low-energy electron diffraction (LEED) measurements. Sublimation-purified DBBA molecules (Aldrich, 98+%) were evaporated in situ from a K-cell onto Ag(111) in the growth chamber.30,31 The nominal deposition rate of DBBA (0.05 ML/min) was precalibrated by a quartz crystal microbalance. All STM images were recorded in constant-current mode using chemically etched tungsten (W) tips at 77 K. The low temperature used minimized thermal noise to give atomically resolved STM images, which were analyzed using WSxM software.32 First-principles calculations were based on the density functional theory (DFT) within generalized gradient approximation (GGA) with PBE33 formula implemented in the Vienna Ab-initio Simulation Package.34 The projector augmented wave (PAW) pseudopotential method is employed to model ionic potentials.35 Kinetic energy cutoff is set above 400 eV for all calculations. Monkhorst-Pack k-point sampling36 is used for the Brillouin zone integration. The slab containing four Ag atomic layers is used 6


Page 6 of 30

Page 7 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

to simulate Ag(111) substrate with lower two layers fixed at their bulk position. Molecules and upper two Ag layers are fully optimized with respect to the ionic positions until the forces on all atoms are less than 0.02 eV/Å. The minimum vacuum layer thickness is greater than 20 Å, which is large enough to avoid artificial interaction between neighboring images. Tersoff-Hamann formula37 is used to obtain the STM images. RESULTS AND DISCUSSION

Figure 2. Deposition of 0.4 ML DBBA on Ag(111) at room temperature. (a) Large scale STM image (Vtip=1.2V, Iset=100 pA) showing the self-assembled DBBA islands in six orientations. Inset: Corresponding FFT pattern. (b) STM image (Vtip=1.2V, 7


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 30

Iset=100 pA) in submolecular resolution from the black rectangle in (a) showing that the islands are formed by armchair-like chains. Line profiles taken along the white and black lines show the average intermolecular distance of 1.51 ± 0.05 nm and 2.36 ± 0.05 nm, respectively. Green rods represent L-DBBA and blue rods represent RDBBA. Inset: View into the armchair-like chains with molecular models overlaid. (c) −

Tentative model of two mirror domains relative to < 1 1 0 >Ag. At a very low coverage, DBBA molecules preferentially adsorb at the step edges of Ag(111), leaving terraces almost empty (data not shown), as previously reported adsorption of F16CuPc on Ag(111).38 When the coverage increases to ~0.4 ML, DBBA molecules aggregate into single layer high elongated islands on Ag(111) terraces once the edges are fully passivated, as shown in Figure 2a. The large scale STM image in Figure 2a and the corresponding Fast Fourier Transform (FFT) pattern inset at the up right corner reveal that these elongated islands are mainly oriented in −

−

six orientations, which deviate from < 1 1 0 >Ag by angles of ±19° (< 1 2 3 >Ag), suggesting that they are mirror domains. The preferred azimuthal orientation indicates that an epitaxial relationship exists between DBBA overlayer and Ag(111).39 The submolecularly resolved STM image in Figure 2b shows that each island consists of several parallel but glided armchair-like molecular chains. The image in the white square has a higher resolution (see Figure S1 in supporting information for enlarged image). The classical appearance of DBBA molecules in STM images is dumbbell-like protrusions, where a protrusion represents an up-tilted phenyl group.23 8


Page 9 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

The defect pointed out by black arrow shows that a slant pair of protrusions belongs to one DBBA molecule. From the inset line profiles the unit cell parameters are measured to be a=1.51 ± 0.05 nm, b=2.36 ± 0.05 nm and θ=120 ± 2°. There are two DBBA molecules in one unit cell. It is concluded that each molecular chain consists of alternative L- and R-DBBA to appear as armchair, in other words, they are racemic chains. The intermolecular distance along the chain is half of b to be 1.18 nm, much larger than that of 0.86 nm for polyanthracene chains on Au(111),23,26,28 suggesting no polymerization takes place. The orientation of each DBBA molecule is hardly determined from the STM image with the highest resolution. Taking the structural model size (around 1 nm)23 of DBBA molecules into account, the configuration with the C-Br axis of DBBA perpendicular to the chain direction is more favorable, which is very similar to the relaxed chain configuration reported by Han P.27 It is further proved by annealing the sample to 450 K, where a protrusion corresponding to the detached Br atom is observed on each side of the flattened DBBA backbone, as shown in Figure S2 in Supporting Information. Several adsorption sites of DBBA on Ag(111) are considered in DFT calculation and the most stable one is shown in Figure 1c (top view is indicated by Figure 1e). It is found that DBBA molecules prefer to adsorb on Ag(111) with the molecule center on top site of surface Ag atom and C-Br bond along −

< 1 1 2 >Ag. The distance between the lowest C atom and substrate is ~2.7 Å. The dihedral angle faced to substrate is 128°. Because of strong interaction between 9


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

molecule and Ag(111) surface, anthryl plane is slightly distorted and charge transfer occurs strongly between them, as shown by the calculated differential charge density map in Figure 1d and 1e. A deductive arrangement is shown by the overlaid ball-andstick models in Figure 2b. Protrusions of every four molecules form a windmill-like pattern, highlighted by the colored rods in Figure 2b. Generally this pattern belongs to the plane group p2 and has chirality.40-42 Rotating direction of the windmill-like pattern is decided by the direction and distance of gliding between neighbored two molecular chains. A homogenous gliding with a distance of

7 /2 Ag(111) lattice constant along

−

< 1 2 3 >Ag results in homochiral islands (for the bottom island) while an alternative opposite gliding with the same distance leads to heterochiral islands (for the right island). Figure 2c shows a proposed model. The master matrix43 of the overlayer is

 a   6 2  aS    =    . A unit cell contains two heterochiral DBBA molecules, in  b   − 3 6  bS  −

which one adsorbs on top site along < 1 1 2 >Ag and another adsorbs on bridge site with C-Br bond deviates 38° from the other. When a DBBA molecule attaches to an existed armchair-like chain with the same chirality as the front one, due to the steric hindrance, it will rotate by an angle of 22° and lead to a mirror island (Figure S3).

10


Page 10 of 30

Page 11 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 3. STM image (Vtip= 2.0V, Iset=100 pA) of coexisting row phase (left) and hexamer phase (right) at 0.8 ML. Defective hexamers made by five bright protrusions are highlighted by white circle. Symmetric dimer axes are marked with black lines. Inset: Local area scanned at negative bias voltage (Vtip= -2.0V, Iset=100 pA). Green rods represent L-DBBA and blue rods represent R-DBBA. W is for wide-row and N is for narrow-row. The white lines highlight the transition between a wide-row and two narrow-rows. The right end of the white lines shows a 15° angle between row phase and hexamer phase.

With the coverage increasing to ~0.8 ML, DBBA molecules self-assemble into two coexisted phases: row phase (left part of Figure 3) and hexamer phase (right part of Figure 3). Randomly distributed narrow (N-) and wide (W-) rows which run along −

< 1 1 0 >Ag form the row phase. The high symmetric directions of hexamer phase have −

a 15° angle with < 1 1 0 >Ag. While DBBA molecules in hexamer phase appear as 11


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 30

uniform protrusions, those in the row phase exhibit two appearances: triangle-like in N-rows and parallel rod-like in W-rows. It is well known that STM contrast is the convolution of sample morphology and the local electronic density of states at a given bias voltage. Images at different bias voltage may bring deep insights. The inset in the white square shows the corresponding submolecularly resolved STM image under an opposite tip bias polarity of the local area (the enlarged image is put into the supplementary Figure S4). In hexamer phase DBBA molecules appear as more localized protrusions, while those in N-rows show the typical dumb-bell like structures.23,25-28 The herringbone packing pattern in N-rows indicates that a N-row −

consists of dimerized two molecular chains with a glide plane along < 1 1 0 >Ag and normal to the surface.44 Those in W-rows look more complicated: the rods in chains at both edges turn into dumb-bells, while those in two inner chains turn into the same protrusions as in the hexamer phase. Transition between one W-row and two N-rows is highlighted in Figure 3. Thus we can conclude that W-rows consist of four molecular chains and each hexamer consists of six DBBA molecules. The existence of pentamers (marked with white cycle in Figure 3) further confirms that one protrusion represents one DBBA molecule in hexamer phase. The difference in molecular appearance of these three phases indicates that DBBA molecules in each phase may have different dihedral angles with a rotatable central CC bond. At low coverage (0.4 ML), the dihedral angle faced to Ag(111) is enlarged due to the dominated interaction between anthryls and Ag(111). The electronic 12


Page 13 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

density of states locates locally at two far separated up-tilted phenyl groups. Thus DBBA molecule looks like dumbbell at 1.2V in net-like domains (Figure 2b). On the contrary, the dihedral angle faced to Ag(111) reduces at high coverage (0.8 ML) due to the increased intermolecular interactions. Overlap between the electronic density of states of up-tilted phenyl groups happened. Thus, DBBA molecule looks like one protrusion at some bias voltage (2.0V for Figure 3 and 0.5V for Figure 4b) in row phase. Occasionally, four protrusions per molecule in N-row (Figure 4c) can be observed depending on the tip conditions. However, this conjecture requires further confirmation by theoretical works, like DFT calculations.

Figure 4. Row phase. (a) Large scale STM image (Vtip= -2.5V, Iset=100 pA). (b, c) Submolecular resolution STM images of a local area scanned at different bias voltage (Vtip=0.5V, Iset=100 pA for b, Vtip= -2.5V, Iset=100 pA for c). Up-tilted phenyl groups in the cross-shape protrusions in (c) are marked with colored rods, in which green for 13


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 30

L-DBBA and blue for R-DBBA. (d, e) Line profiles of the red/black line in (b)/(a). (f) Tentative model of N-row. The dimer axis is marked with red line.

The large scale STM image in Figure 4a is taken from an area occupied by pure row phase. Among the total 80 rows, only two are W-rows, marked with white dashed lines. The average width of N-rows is measured to be 2.27 ± 0.05 nm, slightly smaller than the unit cell vector of net-like island of 2.36 ± 0.05 nm. It can be explained by that with the coverage increasing a collective phase transition occurs via dimerization accompanied by molecule rotating and gliding, which makes the system more stable.45 Figure 4b and 4c show the STM images in submolecular resolution of an area contained both N-rows and W-rows at different tip bias voltages (see supplementary Figure S5 for enlarged images). The periodicity of parallel dimers is measured to be −

1.47 ± 0.05 nm, which approximates to five lattice constant along < 1 1 0 >Ag. The dimer marked with white circle in Figure 4b suggests the possible orientation of the herringbone pattern, which corresponds to the location of up-tilted phenyl groups. The location is clearer in Figure 4c and the protrusions corresponding to the herringbone pattern are highlighted with colored rods. Since the line profile in Figure 4b reveals that the distance between the molecules in a dimer is only 1.10 ± 0.05 nm, Br atoms are less likely to locate in the dimer between molecules. DFT calculation shows the distance between the lowest C atom and substrate is slightly increased to ~2.9Å, and the dihedral angle faced to substrate is reduced to 124 º , indicating the reduced

14


Page 15 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

molecule-substrate interactions. The overlaid ball-and-stick models in Figure 4c give −

a proposed molecular arrangement with C-Br bond running along < 1 1 2 >Ag. Figure 4f shows a tentative model of N-row with an overlayer master matrix of  a   5 0 aS    =    . A glide with distance of 0.5 lattice constant of Ag exists between  b   4 9  bS 

adjacent N-rows (as shown in Figure S6). Both L- and R-DBBA adsorb with C-Br −

axes along < 1 1 2 >Ag, resulting in an intermolecular angle of 60°. Such a configuration makes the anthryl groups align with the high symmetry direction of Ag(111), which is a favor adsorption configuration of anthracene on Ag(111) and −

Cu(111).46,47 The dimer axes are running along < 1 3 4 >Ag, which has an enclosed −

angle of 74° with < 1 1 0 >Ag, going well with the measured angle of 74° in Figure 3. Thus we conclude that the opposite gliding between single chains in N-rows along −

< 1 1 0 >Ag with a glide distance of one lattice constant of Ag is the reason for mirror dimer axis orientations. The dimerization in N-row phase suggests that directional interactions exist between every two molecules, which lowers the total energy and makes the system more stable. The distance between the nearest Br atoms in the model is measured to be ~5.2 Å, excluding the existence of halogen bond. The H atom at position 4 or 5 (depending on the dimer orientation) is pointing to the lower phenyl group of the other molecule. Thus, a weak CH…π bond is supposed to exist between molecules in the dimer, although the H atom is not pointing to the center of aryl ring vertically.48 Figure S7 in Supporting Information shows the tentative model of W-row, which has a similar adsorption configuration to hexamer phase but 15


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 30

−

assembled like N-row. The tetramer axis has a 66° angle to < 1 1 0 >Ag, in line with the experimental measurement.

Figure 5. Hexamer phase. (a, b) Large scale STM images of L- and R-hexamers, respectively. The white/black arrows show the high symmetry direction of hexamer phase/Ag(111). The insets show high resolution STM images of hexamer structures with molecular models overlaid. The line profile in (a) is for the nearby black line. (Vtip=2.0 V, Iset=100 pA for a, Vtip= -2.5 V, Iset=100 pA for inset in a, Vtip=2.2 V,

16


Page 17 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Iset=100 pA for b, Vtip= -2.0 V, Iset=100 pA for inset in b) (c) Tentative model for Land R-hexamers.

Figure 5a and 5b show large scale STM image of homochiral L- and R-hexamer phases with sixfold symmetry respectively. The angle between the close-packing −

direction of L-/R-hexamer and < 1 1 0 >Ag is -15°/+15°, which suggests that they are mirror domains. The unit cell is measured to be a=b=2.80 ± 0.05 nm, θ=60±1°. The high resolution image inset in Figure 5a/5b reveals that L-/R-hexamer domain consists of counterclockwise/clockwise (CCW /CW) rotating hexamers (see supplementary Figure S8 for enlarged images), which belong to plane group p6, one of the five chiral plane groups.42 Similar pattern also be reported for self-assembly of A-OPV4T,12 A-OPV3T13 and HPF49 at 1-octanoic acid/HOPG interface, which is stabilized by hydrogen bond, a relatively strong and directional van der Waals (vdW) force. Hence there may have similar intermolecular interactions in DBBA hexamers. A tentative molecular arrangement is shown by the models overlaid on the insets of Figure 5a and 5b. Figure 5c gives a tentative model for mirror hexamer phases. The

 a   11 3  aS    . The distance between the central Br atoms in a master matrix is   =   b   − 3 8  bS  hexamer model is measured to be 0.35 ± 0.01 nm, implying the possibility of forming halogen bond48,49 - which is comparable with hydrogen bond in strength50 - to stabilize the DBBA hexamers. Besides, CH…π bond may also exist between the H atom at position 4(5) and the aryl ring of adjacent molecule.

17


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The interactions between DBBA molecules and Ag(111) surface work through the overlap between the π orbital, which is parallel to and localized at the lower phenyl groups, and the d-band of surface Ag atoms. A decrease in the molecular dihedral angle in the close-packing hexamer phase is detrimental for overlapping, leading to the reduced molecule-substrate interactions. It is well known that the self-assembly structure is determined by the cooperation of intermolecular interactions and molecule-substrate interactions. The reduced dihedral angle and the new formed halogen bond imply the rebalance between relatively enhanced intermolecular interactions and reduced molecule-substrate interactions by molecular configuration change. The number of Ag atoms occupied by each molecule in N-row, W-row and hexamer phase is 22.5, 17.5 and 16.2, respectively. In the relatively low-dense N-row phase, DBBA has a large dihedral angle facing the substrate, implying the existence of relatively strong molecule-substrate interactions. VdW force and CH…π bond are considered to be existing between molecules in the dimer, both of which are relatively weak interactions. Thus, the molecule-substrate interactions are dominant in the epitaxial self assembly process. L- and R-DBBA are energetically equivalent and both prefer to adsorb on the most stable position on surface. Owing to equal adsorption probability, they form herringbone-shape dimer and pack parallelly to racemic Nrows.

18


Page 18 of 30

Page 19 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Under high packing density, the enhanced intermolecular interactions squeeze molecules and lead to a small dihedral angle. As the same with N-row, the packing pattern of W-row, a 50:50 racemic mixture, forms with the equal probability of adsorbing L- or R-DBBA. However, the large coverage of hexamer phase suggests that DBBA prefers homochiral packing to racemic one when with a small dihedral angle. A possible explanation is that the strengthened intermolecular interactions force molecules to pack closer. The homochiral adsorption configuration is more suitable in achieving close coupling motif, while the repulsion between lower phenyl groups of heterochiral molecules prevent them get closer. Therefore, the chiral phase transition reveals the rebalance between the intermolecular interactions and the molecule-substrate interactions, indicating the tendency of close packing on surface.42 Noticed that the adsorption probability is not changed; heterochiral DBBA molecules may roll on surface to inverse the adsorption chirality to homochiral in the formation of hexamer phase. Besides, hexamer phase transforms into N-row phase upon annealing at 330 K for 30min, suggesting that the N-row phase is more thermostable. Therefore, the formation of N-row phase is likely driven by thermodynamic factors, which make molecules adsorb on the most stable site, while hexamer phase is more likely a kinetic result.20

19


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

CONCLUSIONS We have shown the chiral structures of non-planar DBBA molecules selfassembled on Ag(111) surface with a coverage less than 1 ML by means of ultrahigh-vacuum STM under 77K and DFT calculations. Unlike the homogeneous and long-range ordered chains on Au(111), DBBA self-assembles into various chiral patterns belonging to p2 and p6 group on Ag(111). The transition from racemic pattern to homochiral pattern, affected by enhanced intermolecular interactions, is also discussed. While intermolecular interactions are weak, molecule-substrate interactions dominate the assembly process and make molecules adsorb on the most stable site of surface. With intermolecular interactions increasing, flexible molecules like DBBA adjust their adsorption configurations through decreasing dihedral angle to form close packing. In this case, the suitability of steric configuration and coupling motif between molecules determine the self-assembly pattern. Molecules like DBBA may even inverse the adsorption chirality to achieve a suitable coupling motif before attaching to an exist domain. The findings here may improve the understanding of the complicate process of nonplanar molecule self-assembly on surface.

AUTHOR INFORMATION

Corresponding Author *E-mail: [email protected]

Notes 20


Page 20 of 30

Page 21 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

The authors declare no competing financial interest.

ACKNOWLEDGMENTS

We acknowledge the financial support from the National Natural Science Foundation (NSF) of China (Grants No. 11304398, 11334014, 11374009, 61574123, and 51173205). Dr. Han Huang acknowledges the support from State Key Laboratory of Powder Metallurgy, Central South University and that from NSF of Hunan province (Grants No. 2016JJ1021).

REFERENCES

(1) Barlow, S. M.; Raval, R. Complex organic molecules at metal surfaces: Bonding, organisation and chirality. Surf. Sci. Rep. 2003, 50, 201-341. (2) Gellman, A. J.; Tysoe, W. T.; Zaera, F. Surface chemistry for enantioselective catalysis. Catal. Lett. 2015, 145, 220–232. (3) Fraile, J. M.; Garcia, J. I.; Herrerias, C. I.; Mayoral, J. A.; Pires, E. Enantioselective catalysis with chiral complexes immobilized on nanostructured supports. Chem. Soc. Rev. 2009, 38, 695–706. (4) Das, D.; Dai, Z.; Holmes, A.; Canary, J. W. Exploring the scope of redoxtriggered chiroptical switches: Syntheses, X-ray structures, and circular dichroism of

21


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

cobalt and nickel complexes of N,N-bis(arylmethyl)methionine derivatives.Chirality,

2008, 20, 585-591. (5) Canary, J. W. Redox-triggered chiroptical molecular switches. Chem. Soc. Rev.

2009, 38, 747–756. (6) Anger, E.; Srebro, M.; Vanthuyne, N.; Toupet, L.; Rigaut, S.; Roussel, C.; Autschbach, J.; Crassous, J.; Reau, R. Ruthenium-vinylhelicenes: Remote metalbased enhancement and redox switching of the chiroptical properties of a helicene core. J. Am. Chem. Soc. 2012, 134, 15628–15631. (7) Schweinfurth, D.; Zalibera, M.; Kathan, M.; Shen, C.; Mazzolini, M.; Trapp, N.; Crassous, J.; Gescheidt, G.; Diederich, F. Helicene quinones: Redox-triggered chiroptical switching and chiral recognition of the semiquinone radical anion lithium salt by electron nuclear double resonance spectroscopy. J. Am. Chem. Soc. 2014, 136, 13045–13052. (8) Basozabal, I.; Gómez-Caballero, A.; Unceta, N.; Goicolea, M. A.; Barrio, R. J. Voltammetric sensors with chiral recognition capability: The use of a chiral inducing agent in polyaniline electrochemical synthesis for the specific recognition of the enantiomers of the pesticide dinoseb. Electrochimica Acta, 2011, 58, 729–735. (9) Gutiérrez-Climente, R.; Gómez-Caballero, A.; Unceta, N.; Goicolea, M. A.; Barrio, R. J. A new potentiometric sensor based on chiral imprinted nanoparticles for the discrimination of the enantiomers of the antidepressant citalopram. Electrochimica

Acta, 2016, 196, 496–504. 22


Page 22 of 30

Page 23 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

(10) Li, G.; Shen, J.; Li, Q.; Okamoto, Y. Synthesis and enantioseparation ability of xylan bisphenylcarbamate derivatives as chiral stationary phases in HPLC. Chirality,

2015, 27, 518–522. (11) Zhang, X.; Wang, L.; Dong, S.; Zhang, X.; Wu, Q.; Zhao, L.; Shi, Y. Nanocellulose 3,5-dimethylphenylcarbamate derivative coated chiral stationary phase: Preparation and enantioseparation performance. Chirality, 2016, 28, 376–381. (12) Katsonis, N.; Xu, H.; Haak, R. M.; Kudernac, T.; Tomović, Ze.; George, S.; Auweraer, M. V.; Schenning, A. P.; Meijer, E. W.; Feringa, B. L.; et al. Emerging solvent-induced homochirality by the confinement of achiral molecules against a solid surface. Angew. Chem. 2008, 120, 5075 –5079. (13) Guo, Z.; Cat, I. D.; Averbeke, B. V.; Lin, J.; Wang, G.; Xu, H.; Lazzaroni, R.; Beljonne, D.; Meijer, E. W.; Schenning, A. P.; et al. Nucleoside-assisted selfassembly of oligo(p-phenylenevinylene)s at liquid/solid interface: Chirality and nanostructures. J. Am. Chem. Soc. 2011, 133, 17764–17771. (14) Xu, H.; Saletra, W. J.; Iavicoli, P.; Averbeke, B. V.; Ghijsens, E.; Mali, K. S.; Schenning, A. P.; Lazzaroni, R.; Amabilino, D. B.; et al. Pasteurian segregation on a surface imaged in situ at the molecular level. Angew. Chem. Int. Ed. 2012, 51, 11981 –11985. (15) De feyter, S.; Gesquiere, A.; Abdel-Mottaleb, M. M.; Grim, P. C. M.; De schryver, F. C. Scanning tunneling microscopy: A unique tool in the study of

23


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

chirality, dynamics, and reactivity in physisorbed organic monolayers. Acc. Chem.

Res. 2000, 33, 520-531. (16) Katano, S.; Kim, Y.; Matsubara, H.; Kitagawa, T.; Kawai, M. Hierarchical chiral framework based on a rigid adamantane tripod on Au(111). J. Am. Chem. Soc.

2007, 129, 2511-2515. (17) Linares, M.; Minoia, A.; Brocorens, P.; Beljonne, D.; Lazzaroni, R. Expression of chirality in molecular layers at surfaces: Insights from modeling. Chem. Soc. Rev.

2009, 38, 806–816. (18) Bohringer, M.; Morgenstern, K.; Schneider, W. D.; Berndt, R. Separation of a racemic mixture of two-dimensional molecular clusters by scanning tunneling microscopy. Angew. Chem. Int. Ed. 1999, 38, 821–823. (19) Treier, M.; Ruffieux, P.; Gröning, P.; Xiao, S.; Nuckolls, C.; Fasel, R. An aromatic coupling motif for two-dimensional supramolecular architectures. Chem.

Commun. 2008, 4555–4557. (20) Li, X.; Li, B.; Ji, Y.; Zhang, J.; Zhao, A.; Wang, B. Adsorption and selfassembly of the 2,3,5,6-tetra(2′-pyridyl)pyrazine nonplanar molecule on a Au(111) surface. J. Phys. Chem. C 2016, 120, 6039–6049. (21) Blüm, M.-C.; Ćavar, E.; Pivetta, M.; Patthey, F.; Schneider, W.-D. Conservation of chirality in a hierarchical supramolecular self-assembled structure with pentagonal symmetry. Angew. Chem. Int. Ed. 2005, 44, 5334 –5337.

24


Page 24 of 30

Page 25 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

(22) Huang, T.; Hu, Z.; Zhao, A.; Wang, H.; Wang, B.; Yang, J.; Hou, J. G. Quasi chiral phase separation in a two-dimensional orientationally disordered system: 6nitrospiropyran on Au(111). J. Am. Chem. Soc. 2007, 129, 3857-3862. (23) Cai, J.; Ruffieux, P.; Jaafar, R.; Bieri, M.; Braun, T.; Blankenburg, S.; Muoth, M.; Seitsonen, A. P.; Saleh, M.; Feng, X.; et al. Atomically precise bottom-up fabrication of graphene nanoribbons. Nature, 2010, 466, 470-473. (24) Huang, H.; Wei, D.; Sun, J.; Wong, S. L.; Feng, Y. P.; Neto, A. H.; Wee, A. T. S. Spatially resolved electronic structures of atomically precise armchair graphene nanoribbons. Sci. rep. 2012, 2, 983. (25) Sanchez-Sanchez, C.; Dienel, T.; Deniz, O.; Ruffieux, P.; Berger, R.; Feng, X.; Mullen, K.; Fasel, R. Purely armchair or partially chiral: Noncontact atomic force microscopy characterization of dibromo-bianthryl-based graphene nanoribbons grown on Cu(111). ACS nano 2016, 10, 8006-8011. (26) Simonov, K. A.; Vinogradov, N. A.; Vinogradov, A. S.; Generalov, A. V.; Zagrebina, E. M.; Martensson, N.; Cafolla, A. A.; Carpy, T.; Cunniffe, J. P.; Preobrajenski, A. B. Effect of substrate chemistry on the bottom-up fabrication of graphene nanoribbons: Combined core-level spectroscopy and STM study. J. Phys.

Chem. C 2014, 118, 12532-12540. (27) Han, P.; Akagi, K.; Canova, F. F.; Mutoh, H.; Shiraki, S.; Iwaya, K.; Weiss, P. S.; Asao, N.; Hitosugi, T. Bottom-up graphene-nanoribbon fabrication reveals chiral edges and enantioselectivity. ACSnano 2014, 8, 9181-9187. 25


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(28) Simonov, K. A.; Vinogradov, N. A.; Vinogradov, A. S.; Generalov, A. V.; Zagrebina, E. M.; Martensson, N.; Cafolla, A. A.; Carpy, T.; Cunniffe, J. P.; Preobrajenski, A. B. Comment on "Bottom-up graphene-nanoribbon fabrication reveals chiral edges and enantioselectivity". ACS nano 2015, 9, 3399-3403. (29) Chen, L.; Liu, C.-C.; Feng, B.; He, X.; Cheng, P.; Ding, Z.; Meng, S.; Yao, Y.; Wu, K. Evidence for Dirac fermions in a honeycomb lattice based on silicon. Phys.

Rev. Lett. 2012, 109, 056804. (30) Zhang, L.; Yang, Y.; Huang, H.; Lyu, L.; Zhang, H.; Cao, N.; Xie, H.; Gao, X.; Niu, D.; Gao, Y. Thickness-dependent air-exposure-induced phase transition of CuPc ultrathin films to well-ordered one-dimensional nanocrystals on layered substrate. J.

Phys. Chem. C 2015, 119, 4217−4223. (31) Huang, H.; Wong, S. L.; Wang, Y.; Sun, J.-T.; Gao, X.; Wee, A. T. S. Scanning tunneling microscope and photoemission spectroscopy investigations of Bismuth on epitaxial graphene on SiC(0001). J. Phys. Chem. C 2014, 118, 24995− 24999. (32) Horcas, I.; Fernandez, R.; Gomez-Rodriguez, J. M.; Colchero, J.; GomezHerrero, J.; Baro, A. M. WSXM: A software for scanning probe microscopy and a tool for nanotechnology. Rev. Sci. Instrum. 2007, 78, 013705. (33) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 1996, 77, 3865-3868.

26


Page 26 of 30

Page 27 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

(34) Kresse, G.; Hafner, J. Ab initio molecular dynamics for liquid metals. Phys.

Rev. B 1993, 47, 558-561. (35) Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 1994, 50, 17953-17979. (36) Monkhorst, H. J.; Pack, J. D. Special points for brillouin-zone integrations.

Phys. Rev. B 1976, 13, 5188-5192. (37) Tersoff, J.; Hamann, D. R. Theory of the scanning tunneling microscope. Phys.

Rev. B 1985, 31, 805-813. (38) Huang, H.; Chen, W.; Wee, A. T. S. Low-temperature scanning tunneling microscopy investigation of epitaxial growth of F16CuPc thin films on Ag(111). J.

Phys. Chem. C 2008, 112, 14913–14918. (39) Hooks, D. E.; Fritz, T.; Ward, M. D. Epitaxy and molecular organization on solid substrates. Adv. Mater. 2001, 13, 227-241. (40) Chen, T.; Chen, Q.; Pan, G. B.; Wan, L. J.; Zhou, Q. L.; Zhang, R. B. Linear dislocation tunes chirality: STM study of chiral transition and amplification in a molecular assembly on an HOPG surface. Chem. Commun. 2009, 2649–2651. (41) Chen, Q.; Chen, T.; Zhang, X.; Wan, L. J.; Liu, H. B.; Li, Y. L.; Stang, P. Twodimensional OPV4 self-assembly and its coadsorption with alkyl bromide: From helix to lamellar. Chem. Commun. 2009, 3765–3767. (42) Plass, K. E.; Grzesiak, A. L.; Matzger, A. J. Molecular packing and symmetry of two-dimensional crystals. Acc. Chem. Res. 2007, 40, 287-293. 27


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(43) Merz, L.; Ernst, K.-H. Unification of the matrix notation in molecular surface science. Surf. Sci. 2010, 604, 1049–1054. (44) Huang, H.; Sun, J. T.; Feng, Y. P.; Chen, W.; Wee, A. T. S. Epitaxial growth of diindenoperylene ultrathin films on Ag(111) investigated by LT-STM and LEED.

Phys. Chem. Chem. Phys. 2011, 13, 20933–20938. (45) Oehzelt, M.; Resel, R.; Suess, C.; Friedlein, R.; Salaneck, W. R. Crystallographic and morphological characterization of thin pentacene films on polycrystalline copper surfaces. J. Chem. Phys. 2006, 124, 054716. (46) Shimooka, T.; Yoshimoto, S.; Wakisaka, M.; Inukai, J.; Itaya, K. Highly ordered anthracene adlayers on Ag single-crystal surfaces in perchloric acid solution: In situ STM study. Langmuir, 2001, 17, 6380-6385. (47) Wan, L. J.; Itaya, K. In situ scanning tunneling microscopy of benzene, naphthalene, and anthracene adsorbed on Cu(111) in solution. Langmuir, 1997, 13, 7173-7179. (48) Sarkar, M.; Samanta, A. 10,10’-Dibromo-9,9’-bianthryl. Acta Cryst. E 2003,

59, 01764–01765. (49) Xu, L.; Miao, X.; Cui, L.; Liu, P.; Miao, K.; Chen, X.; Deng, W. Chiral transition of the supramolecular assembly by concentration modulation at the liquid/solid interface. J. Phys. Chem. C 2015, 119, 17920−17929.

28


Page 28 of 30

Page 29 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

(48) Huang, H.; Tan, Z.; He, Y.; Liu, J.; Sun, J.; Zhao, K.; Zhou, Z.; Tian, G.; Wong, S. L.; Wee, A. T. S. Competition between hexagonal and tetragonal hexabromobenzene packing on Au(111). ACS nano 2016, 10, 3198-3205. (49) Bui, T. T.; Dahaoui, S.; Lecomte, C.; Desiraju, G. R.; Espinosa, E. The nature of halogen...halogen interactions: A model derived from experimental charge-density analysis. Angew. Chem. Int. Ed. Engl. 2009, 48, 3838-3841. (50) Gilday, L. C.; Robinson, S. W.; Barendt, T. A.; Langton, M. J.; Mullaney, B. R.; Beer, P. D. Halogen bonding in supramolecular chemistry. Chem. Rev. 2015, 115, 7118−7195.

29


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

TOC

30


Page 30 of 30

Chiral Self-Assembly of Nonplanar 10,10â²-Dibromo-9,9â²-bianthryl

Recommend Documents

Chiral Self-Assembly of Nonplanar 10,10â²-Dibromo-9,9â²-bianthryl