On-Surface Synthesis of Chiral Ï-Conjugate Porphyrin Tapes by

Subscriber access provided by University of Glasgow Library

C: Surfaces, Interfaces, Porous Materials, and Catalysis

On-Surface Synthesis of Chiral #-Conjugate Porphyrin Tapes by Substrate-Regulated Dehydrogenative Coupling Feifei Xiang, Yan Lu, Zhongping Wang, Huanxin Ju, Gianluca Di Filippo, Chao Li, Xiaoqing Liu, Xinli Leng, Junfa Zhu, Li Wang, and M. Alexander Schneider J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b06025 • Publication Date (Web): 02 Sep 2019 Downloaded from pubs.acs.org on September 2, 2019

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 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 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.

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 22 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 Journal of Physical Chemistry

On-Surface Synthesis of Chiral π-Conjugate Porphyrin Tapes by Substrate-Regulated Dehydrogenative Coupling Feifei Xiang,†,‡,‖ Yan Lu,† Zhongping Wang,† Huanxin Ju,¶ Gianluca Di Filippo,‖,┴ Chao Li,† Xiaoqing Liu,† Xinli Leng,ξ Junfa Zhu,¶ Li Wang,*,†,‡ and M. Alexander Schneider*, ‖ † Department of Physics, Nanchang University, Nanchang, 330031 (P.R. China) ‡ Nanoscience and Nanotechnology Laboratory, Institute for Advanced Study, Nanchang University, Nanchang 330031, P.R. China ‖ Solid State Physics, University of Erlangen-Nürnberg, Erlangen 91058, Germany ¶ National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, P.R. China ξ Department of Physics, Nanchang Normal University, Nanchang, 330032, (P. R. China)

ACS Paragon Plus Environment

1

The Journal of Physical Chemistry 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 2 of 22

ABSTRACT: On-surface enantioselective covalent coupling of non-functionalized porphyrins is demonstrated without utilizing chirality transfer from a self-assembled enantiopure precursor structure. We achieved to synthesize chiral porphyrin tapes on the Ag (110) surface by thermally induced dehydrogenative coupling using 5,15-diphenylporphyrin (2H-DPP) as a precursor. We employ scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) to study the properties of the precursor molecules and resulting covalently bonded structures. Our analysis shows that the enantioselectivity is due to the specific molecule-substrate interaction confining the orientation of the diffusing molecules and stearic hindrance making non-enantiopure bonds energetically unfavorable.

INTRODUCTION Molecular chirality has been a hot topic over the years due to the extensive applications in pharmaceutical industry,1,2 enantioselective catalysis3 and non-linear optical devices.4,5 Especially in some biochemical systems, two enantiomers can exhibit significantly different pharmacological effects.6 Therefore, how to effectively recognize and separate chiral molecules attracts a lot of concern. In recent decades, the insight that (achiral) molecules can exhibit chirality if deposited on surfaces opened up a new way to study mechanisms of chiral recognition, transfer, and separation.7–10 The identification of the mechanisms remains of great value even though – as is also the case in the present example – the product if detached from the surface loses its chiral property. With the help of in situ surface analysis techniques e.g. scanning probing microscopies, many different kinds of enantiopure structures with well separated chiral domains were found and various driving forces were identified such as hydrogen bonding,11,12 van der Waals interactions13,14 and metal-organic coordination.15 In contrast, enantioselective


2

Page 3 of 22 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


synthesis which can produce more stable covalently bonded chiral structures, is more difficult to achieve as the strong bonds prevent error correction. On-surface synthesis16, using various surface-assisted reactions such as Ullmann coupling,17,18 Bergman cyclization,19 alkynyl-group based Glaser coupling,20,21 and cyclotrimerization,22 has been demonstrated on metal substrates and provides a feasible way for chiral synthesis on surfaces. By carefully designing the precursor skeletons e.g. the molecular configurations21 and functional groups,23,24 or by relying on confinement and catalytic characteristics of different supporting substrates,25 unwanted side products can be suppressed, giving the desired reaction outputs on the surfaces, e.g. conjugated molecular chains, rings, and networks.17,26–29 However, on-surface chiral synthesis requires more delicate control of precursor radicals so that the chirality can be preserved and transferred to the reaction products.30–32 Recent works show that one way to achieve this is by shifting the chiral recognition and selectivity to weakly coupled self-assembly structures that are then converted into enantiopure covalent products.33,34,28 Alternatively, the specific choice of precursor molecules may also guide the enantioselectivity of the coupling reaction.35,36 However, both methods require the special design of the molecular precursors. Instead, using a chiral, kinked substrate may provide an alternative way to separate enantiomers spatially.37–39 Here we demonstrate that enantioselectivity can be reached in a thermally induced reaction on an achiral Ag (110) making use of substrate confinement and catalysis without prior enantioselectivity of a self-assembly structure. We use unfunctionalized 5,15-diphenlyporphyrin (2H-DPP) molecules, which are converted to a planar DPP species (pDPP) via intramolecular dehydrogenation coupling. The pDPP are chiral on Ag(110) and act as precursors for the subsequent formation of chiral π-conjugate porphyrin tapes without the requirement of


3


Page 4 of 22

preliminary chiral separation. Our experimental and theoretical analysis shows the enantioselectivity of the process is due to high rotational energy barriers confining the molecular orientation during diffusion, and to stearic hindrance such that tapes of mixed chirality are rarely formed. METHODS The experiments were carried out in a multi-chamber STM (Aarhus 150, SPECS) operating at room temperature (RT). A Ag(110) single crystal was cleaned by several cycles of bombardment with Ar ions (5×10-5 mbar) and subsequent annealing to 800 K for 5 mins. 5,15diphenylporphyrin (2H-DPP, Frontier Scientific, purity ≥97%) was evaporated from a Knudsen cell at 448 K onto the Ag (110) crystal kept at RT. All STM images were acquired in constant current mode in ~4.0×10-10 mbar at RT. The bias voltage is applied to the sample and hence gives the sample potential with respect to the tip. The STM images were analyzed by the WSxM image analysis software packages.40 The high-resolution synchrotron radiation photoelectron spectroscopy (HR-SRPES) experiments were performed at the catalysis and surface science end station of the BL11U beamline at the National Synchrotron Radiation Laboratory (NSRL) in Hefei, China. This beamline is connected to an undulator and equipped with two gratings that offer soft X-rays from 20 to 600 eV and a VG Scienta R4000 analyzer with a resolution (E/ΔE) of 10000 at 29 eV. The sample was prepared by depositing 2H-DPP onto a clean Ag (110) surface held at 300 K in a separate MBE chamber equipped with a quartz crystal microbalance. Then the sample was heated to different temperatures and subsequently transferred in situ to the analysis chamber. Photon energies of 500 eV and 400 eV were used for N1s and C1s respectively and the binding


4

Page 5 of 22 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


energy was calibrated against the Au 4f signal of a clean gold substrate at the same photon energies. The HR-SRPES spectra were normalized to account for variations of the photon flux. DFT calculations were performed with the Vienna Ab-initio Simulation Package (VASP)41,42 using the projector augmented wave method (PAW)43 and the generalized gradient approximation (GGA).44 An energy cutoff of 400 eV was chosen. Ag (110) slabs of (7×5×4) and (8×6×4) unit cells for the single pDPP and the dimer respectively were used. The calculations employed the gamma point only. Tests performed for the smaller cell with larger k-point sampling did not yield significant differences in total energy. The van der Waals interaction was incorporated by the optB86b-vdW method.45 For the geometry optimizations, all atoms except those of the bottom two Ag layers were fully relaxed until the residual force per atom was less than 0.02 eVÅ-1. The calculation for non-optimal rotational configurations only employed relaxations to residual forces less than 0.1 eVÅ-1. The STM simulations were performed by using the Tersoff–Hamann approximation.46


5


Page 6 of 22

RESULTS AND DISCUSSION

Figure 1. (a) STM image of 2H-DPP self-assembly structure on Ag (110) after heating the sample to 380 K. U = -2.3 V, I = 0.05 nA. (b) STM image of 2H-DPP intramolecular dehydrogenation coupling reaction products after heating the sample to 470 K. The vast majority of molecules do not form bonds with their neighbors. U =-0.76 V, I = 0.05 nA. (c) Molecular model and chosen nomenclature of different pDPP isomers. (d) top row: experimental cutoff


6

Page 7 of 22 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


(left) and simulated (right) STM image of pDPP 2; bottom row: lowest energy structure in which the pDPP coordinates an Ag atom of the [110] substrate row. Depositing 2H-DPP to a clean Ag (110) held at RT and subsequently heating the sample to 380 K, 2H-DPP forms a close-packed self-assembly structure on the surface as shown in Figure 1(a). 2H-DPP (marked by a blue outline) appears as two bright protrusions with a dim center identified as its two phenyl rings and the porphyrin macrocycle respectively.47 Heating the sample to 470 K for 15 mins triggers an intramolecular dehydrogenative coupling reaction between the phenyl rings of a 2H-DPP and its macrocycle ring. The resulting species on the surface is a new planar, chiral DPP (pDPP) species distributed randomly without any long-range order on the surface (Figure 1(b)). Occasionally dimers and short tapes are already formed by an intermolecular coupling reaction. The single pDPP species are very mobile on the surface, imaging at RT is only possible at dense molecular coverage with restricted pDPP diffusion as shown in Figure 1(b). Three different pDPP isomers are found on the surface. The isomers pDPP 1 and 2 are formed by connecting the two phenyl rings in a DPP to the pyrrolic rings from opposite sides. Hence, on the surface pDPP 1 and 2 are mirror symmetric with each other. pDPP 3 is formed by connecting the two phenyl rings to the pyrrolic rings on the same side. (Figure 1(b) and (c)). Different from what we observed on the Cu (111) surface,48 on Ag(110) 2H-DPP shows a strong bias towards forming the pDPP 1 and 2 (82%) rather than pDPP 3, which is also consistent with the observations on Ag (111) done by other groups.49 At 470 K, the pDPP molecules are already metalated with Ag atoms as supported by the XPS measurements which we will discuss below. From extensive DFT calculations (employing configurations where substrate Ag or an additional “lattice gas Ag atom” are coordinated) we find that the lowest energy configuration is a pDPP coordinating a substrate Ag atom from the substrate [110] rows


7


Page 8 of 22

in top position, i.e. where the center of gravity of the four nitrogen atoms sits on top of an Ag atom of the substrate (Figure 1(d)). The corresponding simulations of STM images reproduce the appearance of the single molecules on the surface rather well (Figure 1(d)). The center Ag atom is pulled out 0.6 Å from the substrate and lies ~1.8 Å below the molecular plane demonstrating significant Ag-N bonding (bond length 2.4 Å). An intermolecular reaction is triggered when heating pDPP to and above 470 K. Figure 2(a) shows an overview STM image after heating the sample to 530 K for 15 mins. The pDPP molecules now form tape-like oligomers on the surface. Figure 2(b) and (c) show detailed views of the dominant pDPP oligomer reaction products, growing along [112] and [112] directions, which are purely composed of pDPP 1 and 2, respectively (1-1 and 2-2). Most pDPP in the oligomers link with each other by single C-C bonds via R3β-L1β carbon-carbon bonds (Figure 2(d)) at their bare porphyrin macrocycle sides. The center-to-center distance of a single bonded tape lies along [112] and is measured to be 9.8±0.2Å in agreement with the calculated centercenter distance between a singly bonded dimer from our DFT calculations (Figure 2(d) and (e)).


8

Page 9 of 22 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 2. STM images of pDPP tapes. (a) Overview STM image after thermally induced intermolecular coupling between pDPP at 530 K. U = 0.18 V, I = 0.15 nA. Insert: atomically resolved STM image of the clean Ag (110) surface. U = -0.56 V, I = 0.03 nA. (b) and (c) STM images of pDPP tapes having different orientations and chirality, named as 1-1 and 2-2 tape. (b) U = -0.5 V, I = 0.02 nA. (c) U = -1.7 V, I = 0.04 nA (d) lowest energy structure in which the 2-2 dimer coordinates an Ag atom of the [110] substrate row. (e) Simulated STM image from (d).


9


Page 10 of 22

This distance is slightly smaller than the distance between top sites along [112] (10 Å) which will cause a moiré type modulation of the binding in longer tapes. The short distance excludes any metal-organic bond between molecules.48 Doubly and triply bonded pDPP species are also observed and can be identified by comparison to DFT simulated STM images. They usually appeared as dimer only, sometimes as part of a single bonded tape.

Figure 3 Lateral manipulation of porphyrin tapes. Green overlaid oligomer is manipulated by moving the STM tip along the red arrow with reduced tip-sample distance (U = -0.51 V, I = 4.1 nA). While the rotational motion from (a) to (b) proves covalent bonds between the five molecules making up the manipulated oligomer. Imaging parameters: U = -2.2 V, I = 0.05 nA. The covalent nature of the bonds within the oligomers is also proven by lateral STM manipulation50–52 experiments exemplified in Figure 3. Here the close proximity between tip and surface is used to manipulate a 5-member pDPP oligomer. It is shown that even the most lefthand molecule making up the manipulated oligomer is covalently bound although it connects via its phenyl ring.


10

Page 11 of 22 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 4 N 1s and C 1s XP spectra of 0.8 monolayer 2H-DPP on Ag (110) deposited at room temperature and followed by heating to the indicated temperatures. All the spectra were taken when the sample was at room temperature. The described reaction steps and analysis of the resulting species are supported by XPS measurements. Figure 4 shows N 1s and C 1s core level spectra taken from a Ag (110) surface with 0.8 ML 2H-DPP adsorbed at RT after subsequent heating to the temperatures indicated in the figure. Up to an annealing temperature of 370 K, the N 1s core level spectrum shows two peaks appearing at 399.8 eV and 398 eV caused by the aminic (-NH-) and the iminic (-N=) nitrogen species of 2H-DPP respectively. As expected the ratio of these two peak area is about 1:1 consistent with findings for other non-metalated porphyrin molecules.53 At 420 K, a new, single peak at 398.4 eV appears and the previous two nitrogen peaks can hardly be detected anymore. The single peak is attributed to the deprotonation of the porphyrin that renders the four


11


Page 12 of 22

nitrogen atoms in the porphyrin macrocycle equivalent. On a metal substrate the four nitrogen atoms in a porphyrin are able to coordinate with metal atoms of the substrate as suggested by DFT. C 1s core level spectra show a single peak at 284.6 eV after heating the sample to 340 K, which is assigned to aromatic carbons in 2H-DPP.54 A peak shift of ~0.4 eV to lower binding energy between the spectra taken after heating the sample from 420 K to 470 K is attributed to the intramolecular dehydrogenation coupling between the phenyl rings and the porphyrin core of a DPP molecule. The configuration of DPP becomes flat, the extension of π systems in the new pDPP molecule55 and the reduced distance between the pDPP and the surface increase the screening effect consequently. As evidenced by the STM data, the intramolecular dehydrogenation of pDPP is completed at 470 K. The continuing shift of the C 1s core level by 0.1 eV to lower binding energy by heating to 570 K could be interpreted as a further extension ofthe π system in the created porphyrin tapes.55 Our STM and XPS observations, as well as the STM tip manipulation experiments clearly corroborate the existence of covalently bonded pDPP tape-like oligomers formed by a dehydrogenative coupling process after thermal treatment. This process turns out to be enantioselective if considered entirely as an on-surface process. Looking at the isolated (gas-phase) products it is only stereoselective. Enantioselectivity of surface reactions was mainly reported to start from enantiopure domains in which the molecules are held together by weak self-assembly forces.33,34 This is clearly not the case in the present system where no such precursor state is formed (Figure 1b).


12

Page 13 of 22 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 5. (a) Histogram of the occurrence of porphyrin tapes with different orientations as a function of molecular coverage. The STM image shows examples of the tape classification. U = 0.18 V, I = 0.16 nA. (b) Occurrence of pDPP units of different oligomer length as a function of molecular coverage. All the samples for statistics are heated to 530 K for 15min. In Figure 5 we present a statistical analysis of the growth of the porphyrin tapes. We classify the tapes into enantiopure tapes (i.e. those consisting only of pDPP 1 or 2) that are oriented mainly along [112]and [112] and two other classes “T-shape” and “[110]”, which may be considered as “defects” in the tapes (Figure 5(a)). The former enantiopure tapes incorporate


13


Page 14 of 22

covalent bonds between the phenyl ring and the porphyrin macrocycle. The data is obtained as function of molecular coverage at a fixed annealing temperature of 530 K. Here, 1 ML (monolayer) is defined as the close-packed self-assembly structure of Figure 1(a). The analysis clearly shows that the formation of tapes consisting of the same pDPP isomers is favorable for molecular coverages below 0.6 ML (Figure 5(a)) and that the average tape length increases with coverage in that regime (Figure 5(b)). These facts point to a chain growth by enantioselective monomer attachment, the effectivity of which depends on the diffusion of molecules to their reaction partners which is hindered in the case of a racemic mixture at higher coverages. To further understand the reason behind the enantioselective growth of the tapes, various molecular configurations were calculated by DFT. In Figure 6(a) the lowest energy configuration of a single bonded 2-1 dimer is shown. Due to steric hindrance the phenyl ring of the pDPP 2 coming closest to the meso- position of the pDPP 1 is bent away from the surface. The 2-1 configuration is 230 meV higher in total energy. Note that when forming the 2-2 (or 1-1) dimer, the pDPP 2 (and symmetry related the pDPP 1) may reach the dimer bonding configuration without stearic hindrance and by staying in their most favorite configuration with respect to rotational orientation (Figure 6(b)). In Figure 6(c) the energetic differences of various orientations and adsorption sites of the single pDPP 2 with respect to its lowest energy configuration is calculated. The orientation is defined by the angle between the [001] direction and the iminic group not attached to the phenyl ring. (The mirror symmetric pDPP 1 behaves the same way, only the angle has to be defined in the opposite sense.) It turns out that the most likely diffusion path is along the closed packed rows. In short-bridge position and by turning ~10° a configuration is found that is only 130meV higher in energy. All other configurations not involving an additional Ag atom are within the gray shaded area of Figure 6(c). However, since


14

Page 15 of 22 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 Ag (110) surface is a rather open surface, one has to consider the effect of diffusing adatoms that are certainly present at the preparation temperatures.41,42 The lowest energy configuration involving coordination of an additional Ag atom is that of the Ag-pDPP on the hollow site at 150°. This configuration is only 140 meV away from the pDPP on the top site if no energy has to be provided for the additional Ag atom. (In the DFT calculation this was accounted for by subtraction of the energy of a Ag bulk atom.) However, since this configuration could not be identified in the experiments it is likely that this is a conservative lower energy estimate. All other configurations involving a silver adatom are also within the gray area of Figure 6(c). The major finding is that the monomer experiences a rather steep energetic barrier against rotation that fixes the orientation also during diffusion. In consequence, this effectively hinders the formation of “defective” tapes where the macrocycle of one molecule joins with the phenyl ring of a neighbor. The formation of a 2-1 (or 1-2) dimer is not only energetically less favorable but also the molecule needs either to turn slightly or bend the phenyl ring before coming close to the binding site, both of which have a considerable energy penalty. Conversely, there is no penalty for attaching a pDPP 3 to a pDPP 1 or 2. Also as evidenced by our experiments, the chain cannot continue to grow beyond a pDPP 3 site. For the production of enantiopure tapes it is therefore necessary to keep the fraction of pDPP 3 as low as possible. The arguments also hold for doubly and triply bonded tapes. Here the lowest energy configuration entails turning the constituting molecules away from its most favorable orientation. In consequence the turning angle is larger for a molecule when it has to attach to a tape with opposite chirality. The energetic difference between a doubly bonded 1-1 pDPP dimer and a 1-2-pDPP dimer was calculated to be close to 1 eV.


15


Page 16 of 22

Figure 6. (a) lowest energy configuration of a 2-1 pDPP dimer and side view along [110] demonstrating the distortion of the molecule (lower row). (b) two pDPP 2 monomers may reach their coupling configuration by diffusing along [110] without significant rotation and stearic hindrance by the former phenyl groups (red arrows). Below, the side view of the essentially flat 2-2 pDPP dimer is shown (top view was shown in Fig. 2(d)). (c) Variation of the calculated total


16

Page 17 of 22 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


energy of a single pDPP 2 as function of angle  defined in (b) and for various absorption sites. The three lowest energy configurations are the pDPP coordinating a Ag row atom at 45° in top position, the short bridge configuration on the Ag row at 60° and the Ag-pDPP coordinating an adatom at 150°. All other configurations are found within or above the gray area (see text for details). CONCLUSIONS In conclusion, chiral, one-dimensional π-conjugate porphyrin tapes linked via covalent β-β carbon bonds were successfully synthesized via a surface-supported dehydrogenation coupling without employing the enantioselectivity of a weakly-bound self-assembly structure. It was found that the key ingredient for the observed reaction is the confined diffusion pathway of the precursor molecules where the rotational orientation of the molecules stays fixed and favors the enantioselective coupling. Such a surface regulated chiral π-conjugate porphyrin tape formation found here on the Ag (110) surface demonstrates the relevant aspects for designing and synthesizing large chiral π-conjugate systems directly on a surface template. AUTHOR INFORMATION Corresponding Author Li Wang: [email protected] M. Alexander Schneider: [email protected] Present Addresses ┴Gianluca Di Filippo, Dipartimento di Scienze, Università degli Studi Roma Tre. Via della Vasca Navale 84, 00146 Roma, Italy Notes The authors declare no competing financial interests. ACKNOWLEDGMENTS This work was financially supported by Natural Science Foundation of China (Grant Nos. 61474059 and 11727902). L. W. acknowledges Jiangxi provincial innovation talents of science


17


Page 18 of 22

and technology (20165BCB18003). F.X. acknowledges support from the Deutsche Forschungsgemeinschaft through the research unit FOR1878 funCOS. REFERENCES (1)

Noyori, R. Asymmetric Catalysis: Science And Opportunities. Angew. Chemie Int. Ed. 2002, 41, 2008–2022.

(2)

Blaschke, G.; Kraft, H. P.; Fickentscher, K.; Köhler, F. Chromatographic Separation Of Racemic Thalidomide And Teratogenic Activity Of Its Enantiomers. Arzneimittelforschung. 1979, 29, 1640–1642.

(3)

Yoon, T. P.; Jacobsen, E. N. Privileged Chiral Catalysts. Science (80-. ). 2003, 299, 1691– 1693.

(4)

Haupert, L. M.; Simpson, G. J. Chirality In Nonlinear Optics. Annu. Rev. Phys. Chem. 2009, 60, 345–365.

(5)

Marder, S. R.; Beratan, D. N.; Cheng, L. T. Approaches For Optimizing The First Electronic Hyperpolarizability Of Conjugated Organic Molecules. Science (80-. ). 1991, 252, 103–106.

(6)

Nguyen, L. A.; He, H.; Pham-Huy, C. Chiral Drugs: An Overview. Int. J. Biomed. Sci. 2006, 2, 85–100.

(7)

Ernst, K. H. Molecular Chirality At Surfaces.In Surface and Interface Science; John Wiley & Sons, Ltd, 2016; Vol. 6, pp 695–748.

(8)

Zaera, F. Chirality In Adsorption On Solid Surfaces. Chem. Soc. Rev. 2017, 46, 7374– 7398.

(9)

Dutta, S.; Gellman, A. J. Enantiomer Surface Chemistry: Conglomerate: Versus Racemate Formation On Surfaces. Chem. Soc. Rev. 2017, 46, 7787–7839.

(10)

Ernst, K. H. Stereochemical Recognition Of Helicenes On Metal Surfaces. Acc. Chem. Res. 2016, 49, 1182–1190.

(11)

Barlow, S. M.; Louafi, S.; Le Roux, D.; Williams, J.; Muryn, C.; Haq, S.; Raval, R. Polymorphism In Supramolecular Chiral Structures Of R- And S-Alanine On Cu(1 1 0). Surf. Sci. 2005, 590, 243–263.

(12)

Ortega Lorenzo, M.; Baddeley, C. J.; Muryn, C.; Raval, R. Extended Surface Chirality From Supramolecular Assemblies Of Adsorbed Chiral Molecules. Nature 2000, 404, 376– 379.

(13)

Wang, L.; Kong, H.; Song, X.; Liu, X.; Wang, H. Chiral Supramolecular Self-Assembly Of Rubrene. Phys. Chem. Chem. Phys. 2010, 12, 14682–14685.

(14)

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. Chemie 2005, 117, 5468–5471.


18

Page 19 of 22 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


(15)

Wang, Y.; Fabris, S.; Costantini, G.; Kern, K. Tertiary Chiral Domains Assembled By Achiral Metal−Organic Complexes On Cu(110). J. Phys. Chem. C 2010, 114, 13020– 13025.

(16)

Shen, Q.; Gao, H. Y.; Fuchs, H. Frontiers Of On-Surface Synthesis: From Principles To Applications. Nano Today 2017, 13, 77–96.

(17)

Fan, Q.; Gottfried, J. M.; Zhu, J. Surface-Catalyzed C–C Covalent Coupling Strategies Toward The Synthesis Of Low-Dimensional Carbon-Based Nanostructures. Acc. Chem. Res. 2015, 48, 2484–2494.

(18)

Fan, Q.; Wang, C.; Han, Y.; Zhu, J.; Kuttner, J.; Hilt, G.; Gottfried, J. M. Surface-Assisted Formation, Assembly, And Dynamics Of Planar Organometallic Macrocycles And Zigzag Shaped Polymer Chains With C–Cu–C Bonds. ACS Nano 2014, 8, 709–718.

(19)

Sun, Q.; Zhang, C.; Li, Z.; Kong, H.; Tan, Q.; Hu, A.; Xu, W. On-Surface Formation Of One-Dimensional Polyphenylene Through Bergman Cyclization. J. Am. Chem. Soc. 2013, 135, 8448–8451.

(20)

Zhang, Y.-Q.; Kepčija, N.; Kleinschrodt, M.; Diller, K.; Fischer, S.; Papageorgiou, A. C.; Allegretti, F.; Björk, J.; Klyatskaya, S.; Klappenberger, F.; et al. Homo-Coupling Of Terminal Alkynes On A Noble Metal Surface. Nat. Commun. 2012, 3, 1286.

(21)

Gao, H.-Y.; Wagner, H.; Zhong, D.; Franke, J.-H.; Studer, A.; Fuchs, H. Glaser Coupling At Metal Surfaces. Angew. Chemie Int. Ed. 2013, 52, 4024–4028.

(22)

Xiang, F.; Lu, Y.; Li, C.; Song, X.; Liu, X.; Wang, Z.; Liu, J.; Dong, M.; Wang, L. Cyclotrimerization-Induced Chiral Supramolecular Structures Of 4Ethynyltriphenylamine On Au(111) Surface. Chem. - A Eur. J. 2015, 21, 12978–12983.

(23)

Sánchez-Sánchez, C.; Nicolaï, A.; Rossel, F.; Cai, J.; Liu, J.; Feng, X.; Müllen, K.; Ruffieux, P.; Fasel, R.; Meunier, V. On-Surface Cyclization Of Ortho -Dihalotetracenes To Four- And Six-Membered Rings. J. Am. Chem. Soc. 2017, 139, 17617–17623.

(24)

Wang, X.-Y.; Urgel, J. I.; Barin, G. B.; Eimre, K.; Di Giovannantonio, M.; Milani, A.; Tommasini, M.; Pignedoli, C. A.; Ruffieux, P.; Feng, X.; et al. Bottom-Up Synthesis Of Heteroatom-Doped Chiral Graphene Nanoribbons. J. Am. Chem. Soc. 2018, 140, 9104– 9107.

(25)

Haq, S.; Hanke, F.; Dyer, M. S.; Persson, M.; Iavicoli, P.; Amabilino, D. B.; Raval, R. Clean Coupling Of Unfunctionalized Porphyrins At Surfaces To Give Highly Oriented Organometallic Oligomers. J. Am. Chem. Soc. 2011, 133, 12031–12039.

(26)

Leng, X.-L.; Song, L.-L.; Lu, Y.; Liu, X.-Q.; Wang, L. Observations Of Carbon–Carbon Coupling Of 4,4ʺ-Dibromo-P-Terphenyl On Cu(110) Surface At Molecular Level. Chinese Chem. Lett. 2017, 28, 24–28.

(27)

Ammon, M.; Sander, T.; Maier, S. On-Surface Synthesis Of Porous Carbon Nanoribbons From Polymer Chains. J. Am. Chem. Soc. 2017, 139, 12976–12984.


19


Page 20 of 22

(28)

Held, P. A.; Fuchs, H.; Studer, A. Covalent-Bond Formation Via On-Surface Chemistry. Chem. - A Eur. J. 2017, 23, 5874–5892.

(29)

Xing, S.; Zhang, Z.; Fei, X.; Zhao, W.; Zhang, R.; Lin, T.; Zhao, D.; Ju, H.; Xu, H.; Fan, J.; et al. Selective On-Surface Covalent Coupling Based On Metal-Organic Coordination Template. Nat. Commun. 2019, 10, 70.

(30)

Stetsovych, O.; Švec, M.; Vacek, J.; Chocholoušová, J. V.; Janík, A.; Rybáek, J.; Kosmider, K.; Stará, I. G.; Jelínek, P.; Starý, I. From Helical To Planar Chirality By OnSurface Chemistry. Nat. Chem. 2017, 9, 213–218.

(31)

Mairena, A.; Wäckerlin, C.; Wienke, M.; Grenader, K.; Terfort, A.; Ernst, K. H. Diastereoselective Ullmann Coupling To Bishelicenes By Surface Topochemistry. J. Am. Chem. Soc. 2018, 140, 15186–15189.

(32)

Li, J.; Martin, K.; Avarvari, N.; Wäckerlin, C.; Ernst, K. H. Spontaneous Separation Of On-Surface Synthesized Tris-Helicenes Into Two-Dimensional Homochiral Domains. Chem. Commun. 2018, 54, 7948–7951.

(33)

Yang, B.; Cao, N.; Ju, H.; Lin, H.; Li, Y.; Ding, H.; Ding, J.; Zhang, J.; Peng, C.; Zhang, H.; et al. Intermediate States Directed Chiral Transfer On A Silver Surface. J. Am. Chem. Soc. 2019, 141, 168–174.

(34)

Zhang, H.; Gong, Z.; Sun, K.; Duan, R.; Ji, P.; Li, L.; Li, C.; Müllen, K.; Chi, L. TwoDimensional Chirality Transfer Via On-Surface Reaction. J. Am. Chem. Soc. 2016, 138, 11743–11748.

(35)

Wang, X. Y.; Urgel, J. I.; Barin, G. B.; Eimre, K.; Di Giovannantonio, M.; Milani, A.; Tommasini, M.; Pignedoli, C. A.; Ruffieux, P.; Feng, X.; et al. Bottom-Up Synthesis Of Heteroatom-Doped Chiral Graphene Nanoribbons. J. Am. Chem. Soc. 2018, 140, 9104– 9107.

(36)

Schulz, F.; Jacobse, P. H.; Canova, F. F.; van der Lit, J.; Gao, D. Z.; van den Hoogenband, A.; Han, P.; Klein Gebbink, R. J. M.; Moret, M.-E.; Joensuu, P. M.; et al. Precursor Geometry Determines The Growth Mechanism In Graphene Nanoribbons. J. Phys. Chem. C 2017, 121, 2896–2904.

(37)

Yun, Y.; Gellman, A. J. Competing Forces In Chiral Surface Chemistry: Enantiospecificity Versus Enantiomer Aggregation. J. Phys. Chem. C 2016, 120, 27285– 27295.

(38)

Yun, Y.; Gellman, A. J. Enantioselective Separation On Naturally Chiral Metal Surfaces: D,L -Aspartic Acid On Cu(3,1,17)R&S Surfaces. Angew. Chemie - Int. Ed. 2013, 52, 3394–3397.

(39)

Horvath, J. D.; Gellman, A. J. Enantiospecific Desorption Of Chiral Compounds From Chiral Cu(643) And Achiral Cu(111) Surfaces. J. Am. Chem. Soc. 2002, 124, 2384–2392.

(40)

Horcas, I.; Fernández, R.; Gómez-Rodríguez, J. M.; Colchero, J.; Gómez-Herrero, J.; Baro, A. M. WSXM : A Software For Scanning Probe Microscopy And A Tool For


20

Page 21 of 22 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


Nanotechnology. Rev. Sci. Instrum. 2007, 78, 013705. (41)

Kresse, G.; Furthmüller, J. Efficient Iterative Schemes For Ab Initio Total-Energy Calculations Using A Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169–11186.

(42)

Kresse, G.; Furthmüller, J. Efficiency Of Ab-Initio Total Energy Calculations For Metals And Semiconductors Using A Plane-Wave Basis Set. Comput. Mater. Sci. 1996, 6, 15–50.

(43)

Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials To The Projector AugmentedWave Method. Phys. Rev. B 1999, 59, 1758–1775.

(44)

Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865–3868.

(45)

Klimeš, J.; Bowler, D. R.; Michaelides, A. Van Der Waals Density Functionals Applied To Solids. Phys. Rev. B 2011, 83, 195131.

(46)

Tersoff, J.; Hamann, D. R. Theory Of The Scanning Tunneling Microscope. Phys. Rev. B 1985, 31, 805–813.

(47)

Xiang, F.; Li, C.; Wang, Z.; Liu, X.; Jiang, D.; Leng, X.; Ling, J.; Wang, L. Direct Observation Of Copper-Induced Metalation Of 5,15-Diphenylporphyrin On Au(111) By Scanning Tunneling Microscopy. Surf. Sci. 2015, 633, 46–52.

(48)

Xiang, F.; Gemeinhardt, A.; Schneider, M. A. A. Competition Between Dehydrogenative Organometallic Bonding And Covalent Coupling Of An Unfunctionalized Porphyrin On Cu(111). ACS Nano 2018, 12, 1203–1210.

(49)

Wiengarten, A.; Lloyd, J. A.; Seufert, K.; Reichert, J.; Auwärter, W.; Han, R.; Duncan, D. A.; Allegretti, F.; Fischer, S.; Oh, S. C.; et al. Surface-Assisted Cyclodehydrogenation; Break The Symmetry, Enhance The Selectivity. Chem. - A Eur. J. 2015, 21, 12285– 12290.

(50)

Meyer, G.; Zöphel, S.; Rieder, K. H. Scanning Tunneling Microscopy Manipulation Of Native Substrate Atoms: A New Way To Obtain Registry Information On Foreign Adsorbates. Phys. Rev. Lett. 1996, 77, 2113–2116.

(51)

Swart, I.; Sonnleitner, T.; Niedenführ, J.; Repp, J. Controlled Lateral Manipulation Of Molecules On Insulating Films By STM. Nano Lett. 2012, 12, 1070–1074.

(52)

Grill, L.; Dyer, M.; Lafferentz, L.; Persson, M.; Peters, M. V.; Hecht, S. NanoArchitectures By Covalent Assembly Of Molecular Building Blocks. Nat. Nanotechnol. 2007, 2, 687–691.

(53)

Gottfried, J. M.; Flechtner, K.; Kretschmann, A.; Lukasczyk, T.; Steinrück, H. P. Direct Synthesis Of A Metalloporphyrin Complex On A Surface. J. Am. Chem. Soc. 2006, 128, 5644–5645.

(54)

Lukasczyk, T.; Flechtner, K.; Merte, L. R.; Jux, N.; Maier, F.; Gottfried, J. M.; Steinrück, H. P. Interaction Of Cobalt(II) Tetraarylporphyrins With A Ag(111) Surface Studied With


21


Page 22 of 22

Photoelectron Spectroscopy. J. Phys. Chem. C 2007, 111, 3090–3098. (55)

Schöll, A.; Zou, Y.; Jung, M.; Schmidt, T.; Fink, R.; Umbach, E. Line Shapes And Satellites In High-Resolution X-Ray Photoelectron Spectra Of Large π-Conjugated Organic Molecules. J. Chem. Phys. 2004, 121, 10260–10267.

TOC Graphic


22

On-Surface Synthesis of Chiral Ï-Conjugate Porphyrin Tapes by

Recommend Documents

On-Surface Synthesis of Chiral Ï-Conjugate Porphyrin Tapes by