1. Robust hexagonal rings on Cu(111) Figure S1 2. Details of Monte Carlo simulations

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1 Supporting Information for Influence of Relativistic Effects on Assembled Structures of V-Shaped Bispyridine Molecules on M(111) Surfaces where M = Cu, Ag, Au Xue Zhang, 1,ǁ Na Li, 1, Hao Wang, 1 Chenyang Yuan, 1 Gaochen Gu, 1 Yajie Zhang, 1 Damian Nieckarz, 2 Paweł Szabelski, 3 Shimin Hou, 1,4,* Boon K. Teo, 1 Yongfeng Wang 1,4,* 1. Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing , China 2. Supramolecular Chemistry Laboratory,University of Warsaw,Biological and Chemical Research Centre,Zwirki i Wigury 101, Warsaw,Poland 3. Department of Theoretical Chemistry, Maria-Curie Skłodowska University, Pl. M.C. Skłodowskiej 3, Lublin, Poland 4. Peking University Information Technology Institute (Tianjin Binhai), Tianjin , China 1. Robust hexagonal rings on Cu(111) In the case of BPyB molecules coordinated with Cu adatoms on Cu(111), the twofold coordination was so robust that these coordinated structures could maintain almost intact even under severe STM tip manipulations. The coordinated ring marked in Figure S1 only deformed slightly after several harsh tip manipulations (V B = 1 mv, I t = 5 na). Figure S1 Effects of the STM tip lateral manipulation on the six-membered ring on Cu(111): before (a) and after (b) manipulation. The yellow arrow indicates the direction of the STM tip movement. Scanning conditions: constant-current mode, (a) V B = 10 mv, I t = 20 pa; (b) V B = 10 mv, I t = 100 pa. 2. Details of Monte Carlo simulations The BPyB molecules (L) were treated as rigid planar structures comprising three interconnected segments, each of which was able to occupy one site on a triangular lattice (see Figure S2a). The metal atoms (M) were represented by single segments. The only interaction allowed in the considered 2D systems was the M-L interaction, which occurred only when these species occupied neighboring sites on the lattice and the interaction directions (shown as the black arrows) were collinear. The interaction S1

2 between M and L was characterized by the energy parameter ε = -1, while in all of the remaining situations interaction was neglected (set equal to zero). In view of recent experimental findings, 1 to accelerate the simulations and to eliminate possible clustering of linker molecules we assumed herein that the segments of the linkers could not occupy neighboring sites on the lattice. 2 The same assumption was made in the case of the metal atoms. The calculations were performed for the same set of parameters as in Ref. 3, namely 1000 M L adsorbed on a 200 by 200 triangular lattice. In the present study we monitored ten independent system replicas, collected corresponding snapshots of the adsorbed phase and calculated average values of structural parameters. During each simulation run the adsorbed phase was cooled down from T = 1.0 to T = 0.01 with T being temperature expressed in ε / k units. The picture of the adsorbed phase shown in Figure S2a is typical for all of the system replicas resulting in the statistical structural properties which are summarized in Figure S2b. In this figure we plotted amount fractions of metal-organic constructs of a different size that is measured by the number of composite linker molecules (chain length). As it follows from the figure, at moderate temperatures (0.2) the self-assembly is ineffective with most of the molecules being isolated (~77%) and forming bimolecular chains (~18%). When the system is sufficiently cooled down the hexagons dominate on the surface (~74%) but also the larger closed-chain structures emerge: that is the ten-membered dumbbells (~9%) and twelve-membered tripods (~2%). Figure S2 Monto Carlo simulation results of BPyB molecules coordinating to Cu atoms on the (111) surface. (a) Snapshots of the adsorbed overlayer comprising 1000 linker (L) molecules and 1000 metal atoms simulated at T = (b) Chain length distribution obtained for the system (a) at low (T=0.01) and moderate (T=0.20) temperature. 3. Various molecular structures on Au(111) and tip manipulation BPyB molecules on Au(111) formed many kinds of complex structures consisting of both hydrogen bonds and coordinated bonds. In addition to irregular chains, various rings adsorbed at the elbow sites of the herringbone reconstruction. Figure S3 shows these nanostructures formed on Au(111). It can be seen from the high-resolution images that the center-to-center separations of neighboring BPyB S2

3 molecules can be divided into two categories: a smaller one and a larger one. Repeated STM tip manipulations were tried to identify the structural stability. These rings were broken easily under moderate manipulating conditions (e.g. V B = 5 mv, I t = 1 na) at sites where the intermolecular distance was larger and thus were verified as hydrogen-bonded sites. Figures S3c and d depict such a manipulating process of cutting and deforming hydrogen bonds in a four-membered ring while adjacent coordinated bonds are well-conserved. Figure S3 (a) Overview of various complex structures on Au(111). (b) Irregular chains along the elbow sites that were formed by twofold coordinated bonds and hydrogen bonds. (c) A four-membered ring formed by coordinated bonds with a short length and hydrogen bonds with a longer length. (d) The ring in (c) was broken at the hydrogen bond site by a mild tip manipulation. Scanning conditions: (a) constant-current mode, V B = 1 V, I t = 50 pa; (b) constant-current mode, V B = 10 mv, I t = 100 pa; (c) constant-height mode, V B = 10 mv, I t = 100 pa; (d) constant-current mode, V B = 50 mv, I t = 60 pa. The arrows in (a) and (b) indicate the [1 10] direction. 4. Verifying the coordination of BPyB molecules to metal adatoms on Au(111) and Cu(111) by variable-temperature experiments We performed a series of variable-temperature experiments to validate the coordination of BPyB molecules to metal adatoms. On Au(111), when BPyB molecules were deposited onto a substrate that was taken from a liquid helium environment, ligand-metal coordination was rare to see and H-bonds prevailed (Figure S4a). During deposition, the sample temperature is below the room temperature. However, we could not measure the temperature in a precise way. When the sample was further annealed to 350 K, despite of partial desorption, BPyB S3

4 molecules bonded to each other mostly through Au-N coordination bonds (Figure S4b). The phenomena on Cu(111) were similar to that on Au(111). Coexistence of H-bonds and coordinated rings on Cu(111) was observed when deposition occurred on a sample taken from the liquid helium environment (Figure S4c). Only coordinated structures were observed when depositing BPyB molecules onto Cu(111) at room temperature. Figure S4. Variable-temperature depositions on Au(111) and Cu(111). (a) BPyB molecules formed self-assembly patterns mainly through H-bonds when deposition occurred on a sample taken from the liquid helium environment. (b) After further annealing to 350 K, twofold coordination bonds increased dramatically compared to the tiny amount of H-bonds. (c) Coexistence of H-bonds and coordinated rings on Cu(111) when deposition occurred on a sample taken from the liquid helium environment. Scanning parameters: constant-current mode, (a) V B = 1 V, I t = 23 pa; inset: V B = 20 mv, I t = 83 pa. (b) V B = 100 mv, I t = 53 pa; inset: V B = 20 mv, I t = 43 pa. (c) V B = 200 mv, I t = 43 pa; inset: V B = 20 mv, I t = 53 pa. S4

5 5. Various molecular structures on Cu(111) At slightly higher coverages, more complex BPyB-Cu coordinated structures appeared on the Cu(111) surface (Figure S5). Besides deformed 6-, 7- and 8-member rings, some of them are complex polygonal rings consistent with the symmetry of the underlying Cu(111) surface. Figure S5 (a) Overview of some complex BPyB-Cu coordinated structures formed on Cu(111) at high coverage. BPyB-Cu coordinated structures (b) and a schematic diagram (c) of some more complex polygonal rings. (d) Deformed 6-,7- and 8-member rings. Scanning conditions: (a) constant-current mode, V B = 1 V, I t = 30 pa; (b) constant-height mode, V B = 10 mv, I t = 70 pa; (d) constant-current mode, V B = 1 V, I t = 20 pa. S5

6 6. STM images obtained at low and high voltages Figure S6 The yellow and blue arrows mark the coordinated and hydrogen-bonded structures, respectively. In low-voltage STM images (a and c), they look similar. The coordination-bonded BPyB molecules appear much brighter than others in the same areas imaged at the high voltage (b and d). 7. DFT Calculations DFT calculations are performed using the SIESTA code. Figure S6a shows the atomic structures modeling the bonding of the BPyB molecules with noble metal atoms: (I) the metal complexes composed of two BPyB molecules and one individual metal atom (M=Au, Ag, Cu), (II) one BPyB molecule lying on the atomic flat M(111) surface, (III) one BPyB molecule adsorbed at the adatom site of the M(111) surface, and (IV) two BPyB molecules adsorbed at the adatom site of the M(111) surface. The M(111) surface is modeled by three atomic layers with each layer composed of 56 atoms for Au and Ag or 80 atoms for Cu. During the geometric optimization, the positions of atoms in the bottom two layers are fixed, while the positions of atoms in the upmost layer, the metal adatom and the atoms in the BPyB molecules are fully relaxed until the force on each atom is smaller than 0.04 ev/å. S6

7 The binding energy of two BPyB molecules with the metal adatom on the (111) surface is obtained by subtracting the binding energy of one BPyB molecule in structure-ii from that of two BPyB molecules in structure-iv (see Figure S6a). The calculated values are 1.68 ev for Cu, 0.75 ev for Ag and 1.13 ev for Au, almost twice the energy difference between structure-iii and structure-ii. In contrast, the binding energies of two BPyB molecules with individual metal atom are calculated to be 1.94 ev for Cu, 0.87 for Ag and 1.47 ev for Au, indicating that the underlying metal substrate slightly weakens the bonding of the two BpyB molecules with the metal adatom. This is consistent with the changes of the M-N distances (see Figure S6b). Figure S7 (a) Various structure models from left to right: (I) BPyB-M-BPyB complexes (M=Au, Ag, Cu) in the gas phase, (II) one BPyB molecule adsorbed on the flate M(111) surface, (III) one BPyB molecule adsorbed at the adatom site of the M(111) surface and (IV) two BPyB molecules adsorbed at the adatom site of the M(111) surface. (b) Upper panel: the binding energies E b of one or two BPyB molecules bonding with one metal atom or the metal substrate shown in (a); lower panel: the optimized distance D N-M between the N atom in BPyB and the metal atom. Reference 1. Zhang, X.; Li, N.; Gu, G.; Wang, H.; Nieckarz, D.; Szabelski, P.; Lü, J.; He, Y.; Wang, Y.; Xie, C.; Shen, Z.; Tang, H.; Peng, L.; Hou, S.; Wu, K.; Wang, Y. Controlling Molecular Growth between Fractals and Crystals on Surfaces. ACS Nano 2015, 9, Pivetta, M.; Pacchioni, G. E.; Fernandes, E.; Brune, H. Temperature-Dependent Self-Assembly of NC Ph5 CN Molecules on Cu (111). J. Chem. Phys. 2015, 142, Nieckarz, D.; Szabelski, P. Simulation of the Self-Assembly of Simple Molecular Bricks into Sierpiński Triangles. Chem. Commun. 2014, 50, S7