A two-dimensional polymer prepared by organic synthesis · A two-dimensional polymer prepared by...

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SUPPLEMENTARY INFORMATIONDOI: 10.1038/NCHEM.1265

Supplementary Information for

A two-dimensional polymer prepared by organic synthesis

Patrick Kissel, Rolf Erni, W. Bernd Schweizer, Marta D. Rossell, Benjamin T. King,

Thomas Bauer, Stephan Götzinger, A. Dieter Schlüter & Junji Sakamoto

Table of Contents

1. Materials and methods…………………………………………………page S2

1.1. Synthesis………………………………………………………...… page S2

1.2. Crystallization………………………………………………………page S8

1.3. Solid-state UV/vis spectroscopy……………………………..........page S10

1.4. Photo-polymerization and in situ fluorescence spectroscopy..........page S10

1.5. Exfoliation……………………………………………….………...page S12

1.6. Optical (OM) and polarizing optical microscopy (POM)…………page S12

1.7. Scanning (SEM) and transmission electron microscopy (TEM).....page S12

1.8. Atomic force microscopy (AFM)…………………………………page S13

1.9. Raman spectroscopy………………………………………………page S14

1.10. Computer simulation………………………………………….....page S14

2. Supplementary figures…………………………………….…………..page S15

3. Supplementary discussion on Raman analysis………………………. page S30

4. Supplementary overview of some 2D polymers’ characteristics useful for

applications………………………………...……………….…….…….....page S34

5. Supplementary references…………………………………………….page S34

© 2012 Macmillan Publishers Limited. All rights reserved.



1. Materials and methods

1.1. Synthesis 1.1.1. General All the reactions were carried out under nitrogen by using standard Schlenk techniques and dry solvents. THF was distilled by a solvent drying system from LC Technology Solutions Inc. SP-105 under nitrogen atmosphere (H2O content < 10 ppm as determined by Karl-Fischer titration). All the reagents were purchased from Acros, Aldrich or Fluka, and used without further purification. Diethyl azodicarboxylate (DEAD) was used as a 40% solution in toluene. Compounds 225, 324, 524, 624, 1040 and 1241 were prepared according to the literature procedures (Figure S1). The other compounds except 1, 4, 7 and 13 were purchased from Fluka (for 8) and Aldrich (for 9 and 11) and used without further purification. Column chromatography for purification of the products was performed by using Merck silica gel Si60 (particle size 40-63 µm). NMR was recorded with Bruker AM (1H: 300 MHz, 13C: 75.5 MHz) or Bruker AVANCE (1H: 700 MHz, 13C: 176 MHz) at 80 °C (for 1) or at room temperature (for the others). The signal from the solvents were used as internal standard for chemical shift (1H: δ = 7.24 ppm, 13C: δ = 77.00 ppm for chloroform, 1H: δ = 6.00 ppm, 13C: δ = 74.00 ppm for 1,1,2,2-tetrachloroethane, 1H: δ = 7.00 and 7.26 ppm, 13C: δ = 133.0, 130.6 and 127.8 ppm for o-dichlorobenzene). For centrifugation, a Hermle Z 320 K table centrifuge was used at 25 °C. High resolution mass spectroscopy (HRMS) analyses were performed by the MS-service of the laboratory for organic chemistry at ETH Zurich with spectrometers (ESI- and MALDI-ICR-FTMS: IonSpec Ultima Instrument). Either 3-hydroxypicolinic acid (3-HPA) or trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) was used as matrix in the presence of silver triflate for the latter.




Figure S1. Chemical structures of the compounds used in the present study. 1.1.2. Monomer 1 To a solution of compound 2 (100 mg, 0.065 mmol), triphenylphosphine (51.6 mg, 0.197 mmol) and trimesic acid (13.7 mg, 0.065 mmol) in THF (60 mL) was added dropwise a 40 % solution of DEAD (0.9 mL, 2 mmol) in toluene at 0 °C. The mixture was stirred at room temperature for 5 days. The solvent was removed under




reduced pressure and the residue was dispersed in dioxane/methanol 4/1 (8.0 mL). This dispersion was centrifuged (3500 rpm, 20 min) and the supernatant was removed by decantation. This procedure was repeated twice. The resultant yellowish green solid was dried in vacuo to afford 1 (38.0 mg, 34 %). 1H NMR (700 MHz, C2D2Cl4) δ: 9.52 (s, 3H, anthrylene), 8.96 (s, 3H, cap), 8.39 (s, 3H, anthrylene), 7.96 (d, J = 8.4 Hz, 6H, anthrylene), 7.79 (d, J = 6.6 Hz, 6H, anthrylene), 7.73 (s, 6H, terphenyl), 7.69 (s, 3H, terphenyl), 7.62 (s, 6H, terphenyl), 7.38 (dd, J = 8.4 Hz, 6.6 Hz, 6H, anthrylene), 7.36 (s, 6H, terphenyl), 7.23 (s, 6H, terphenyl), 5.63 (s, 6H, benzyl), 2.10 (s, 18H, Ar-CH3). 13C NMR (176 MHz, C2D2Cl4) δ: 164.8, 140.5, 139.7, 138.8, 137.5, 135.1, 132.1, 131.9, 131.5, 131.33, 131,29, 128.9, 128.0, 127.5, 126.4, 126.3, 125.2, 124.9, 124.0, 123.8, 121.6, 95.3, 87.8, 67.1, 21.0. HRMS (FT-MALDI, 3-HPA): m/z calcd for C126H78O6 [M]+ 1686.5793; found 1686.5769.

(a)

(b)

Figure S2. 1H- (a) and 13C NMR spectra of 1 (b) in C2D2Cl4 at 80 °C. The signal at δ = 7.5 ppm in the former spectrum is due to residual ODCB. The broad peak around 115 ppm in the latter is an artifact. The 1H NMR spectrum can easily be recorded at ambient temperatures as well.




1.1.3. Compound 4 A mixture of compound 3 (200 mg, 0.492 mmol) and diphenylacetylene (4.38 g, 24.6 mmol) was heated at 200 °C for 5 days with stirring. The reaction mixture was then cooled to room temperature and subjected to silica gel chromatography (hexane/dichloromethane 1/020/110/15/1) affording 4 (178 mg, 62 %) as colourless solid. 1H NMR (700 MHz, CHCl3) δ: 7.35 (d, J = 7.3 Hz, 2H), 7.31 (d, J = 7.2 Hz, 2H), 7.24-7.11 (m, 12H), 7.08 (d, J = 7.2 Hz, 2H), 7.02 (d, J = 7.7 Hz, 2H), 7.01 (dd, J = 7.6 Hz, 7.3 Hz, 2H), 6.94 (dd, J = 7.7 Hz, 7.6 Hz, 2H), 6.64 (s, 1H), 5.38 (s, 1H), 2.13 (s, 6H). 13C NMR (176 MHz, CDCl3) δ: 146.9, 146.0, 145.5, 145.2, 138.7, 137.9, 137.8, 132.2, 128.9, 128.8, 128.3, 128.2, 128.03, 128.01, 127.9, 127.0, 126.9, 124.8, 123.0, 122.8, 118.6, 92.9, 86.8, 58.6, 53.9, 21.0 (Of the 31 expected carbon signals 26 were found, 5 are expected to be superimposed with other signals). HRMS (FT-MALDI, DCTB + AgOTf): m/z calcd for C46H32Ag [M + Ag]+ 691.1549; found 691.1549. (a)

(b)

Figure S3. 1H- (a) and 13C NMR spectra of 4 (b) in CDCl3 at room temperature.




1.1.4. Compound 7 To a mixture of chromium(VI)oxide (98.4 mg, 0.984 mmol) in glacial acetic acid/water 10/1 (3.3 mL) was added compound 3 (100 mg, 0.246 mmol) at room temperature. The mixture was stirred for 1 day at room temperature. After removal of the solvent under reduced pressure, the residue was subjected to silica gel chromatography (hexane/ethyl acetate 10/1) to afford 7 (30.0 mg, 28 %) as yellow solid. 1H NMR (300 MHz, CHCl3) δ: 8.24 (dd, J = 7.9 Hz, 1.1 Hz, 2H), 7.85 (dd, J = 7.5 Hz, 1.3 Hz, 2H), 7.51 (dd, J = 7.9 Hz, 7.5 Hz, 2H), 7.33 (s, 2H), 7.27 (d, J = 7.5 Hz, 2H), 7.13 (d, J = 7.5 Hz, 2H), 7.03 (dd, J = 7.5 Hz, 7.5 Hz, 2H), 6.66 (s, 1H), 3.50 (s, 1H), 2.20 (s, 6H). 13C NMR (75 MHz, CDCl3) δ: 183.2, 142.9, 138.2, 137.4, 132.2, 131.4, 129.7, 128.9, 128.7, 128.4, 127.5, 123.9, 122.2, 95.7, 85.7, 63.5, 21.1. HRMS (FT-MALDI, 3-HPA): m/z calcd for C32H22O2 [M]+: 438.1620; found: 438.1621; m/z calcd for C32H21O [M – H2O]+: 421.1587; found: 421.1589. (a)

(b)





1.1.5. Compound 13 A solution of compound 12 (230 mg, 0.62 mmol) in toluene (10 mL) was prepared in a Schlenk tube (Pyrex glass) and purged with argon bubbling for 30 min. The solution was then irradiated by UV (315 nm- 460 nm) for 46 h under nitrogen using a 250 W Ga-doped Hg light source (UV Light Technologies, with a “Blue Band” filter from the same company). The light source was placed at a distance of ca. 20 cm from the solution. The products partially precipitated. The mixture was heated to dissolve the precipitate and kept at 4 °C over night. The resultant crystals were collected by filtration, rinsed with hexane (5 mL) and dried in vacuo to afford 13 (130 mg, 56 %) as colourless needles. 1H NMR (300 MHz, CHCl3) δ: 7.06 (d, J = 6.9 Hz, 4H), 6.97 (d, J = 7.4 Hz, 4H), 6.80 (dd, J = 7.4 Hz, 6.9 Hz, 4H), 5.54 (d, J = 10.7 Hz, 2H), 4.55 (d, J = 10.7 Hz, 2H), 0.39 (s, 36H). 13C NMR (CDCl3, 75 MHz) δ: 144.0, 143.2, 130.1, 126.2, 125.6, 121.7, 104.4, 98.0, 52.1, 48.6, 0.5. HRMS (ESI): m/z calcd for C48H52Si4 [M]+: 741.3219; found: 741.3219. (a)

(b)





1.2. Crystallization Monomer 1 was crystallized into single crystals by two methods. Method 1: A solution of 1 (40 mg) in 1,1,2,2-tetrachloroethane (3 mL) was subjected to vapour diffusion of THF at room temperature in a closed glass vial. The crystal growth required 2-4 weeks. The resultant crystals were collected by filtration through a Teflon membrane with 0.2 µm pore size (Sartorius GmbH, Göttingen, Germany) and rinsed with THF. They were either directly used for the UV irradiation experiment or stored in a closed vial at -18 °C. Method 2: Onto the top of a solution of 1 in 1,1,2,2-tetrachloroethane in a glass tube (diameter: 2-3 mm), a ca. four time larger volume of THF was added, and the glass tube was melt-sealed. The crystal growth required 2-4 weeks. The resultant crystals were used for the UV irradiation experiments either as-is within the mother liquor or after the mother liquor was replaced with hexane and the glass tube was re-sealed. X-ray analysis: Two crystal structure analyses have been done for monomer 1 from different crystallization conditions. Although the compound crystallizes in different space groups with different solvent molecules, monomer 1 shows an isomorphous packing arrangement in the two structures (Structures A & B). Atomic coordinates and structure factors for the crystal structures A and B have been deposited with the Cambridge Structural Database under accession codes CCDC 827388 and 827387, respectively. Structure A was used for all subsequent experiments described in the present paper. Suitable crystals were measured on a Bruker-Nonius Kappa-CCD with MoKα radiation, λ = 0.71073 Å. Structure A: Crystal data for Compound 1 (from 1,1,2,2-tetrachloroethane/THF) at 172K for C126 H78 O6

. 5C4H8O, Mr = 2048.40, yellow crystal with dimensions 0.3x0.3x0.06 mm, rhombohedral space group P-3, ρcalcd = 1.274g cm-3, Z = 2, a = 22.205(3) Å, 22.205(3) Å, c = 12.509 (1) Å, γ = 120°, V = 5341 (1) Å3, absorption coefficient µ = 0.079 mm-1. From the 16095 reflexions measured 6845 unique reflexions were obtained (Rint = 0.15).The structure was solved by direct methods with SHELXS-9742 and refined by full-matrix least-squares analysis (SHELXL-97)42. Because of the low crystal quality and the disordered THF molecules only selected non H-atoms were refined anisotropically, Hydrogen positions from monomer 1 were calculated and included in the structure factor calculation. No H-atoms from the disordered THF molecules were included. Final R(F) = 0.1362, wR(F2) = 0.389 for 535 parameters and 5663 reflections with I > 2σ(I) and 1.1 < θ < 26.35°. Remarks on the CIF checking procedure. The structure contains heavily disordered THF molecules. One on a three-fold axis and one in general position both in the cavity of the molecule have been refined over two positions with constrained geometry. A disordered THF filling the channel between the molecules in the direction of the c-axis were simulated by 5 atom positions around a three-fold axis. The limited data quality did not allow to refine the disorder model further leaving relatively high difference electron density peaks near the solvent molecules and showing high R-factors. The short contacts are distances between different disordered parts and not seen in the real structure.




Figure S6. ORTEP plot of structure A at the 50 % level. Solvent molecules are omitted for clarity. Structure B: Crystal data for Compound 1 (from 1,2-dichlorobenzene/hexane) at 100K for C126 H78 O6

. C6H4Cl2 . 3C6H14, Mr = 2007.36, yellow crystal with dimensions

0.27x0.045x0.03 mm, triclinic space group P-1, ρcalcd = 1.233g cm-3, Z = 2, a = 12.5392(4) Å, 21.8440(5)Å, c = 22.5292(6) Å, α =61.234(2)°, β = 88.29 8(2)°, γ = 89.809(2)°, V = 5406.5(3) Å3, absorbtion coefficient µ = 0.121 mm-1. From the 33553 reflexions measured 19142 unique reflexions were obtained (Rint = 0.15).The structure was solved by the ’charge flipping method’ with OLEX243 and refined by full-matrix least-squares analysis (SHELXL-97)42. All non H-atoms were refined anisotropically, some of the H-atoms were localized from a difference fourier map and refined isotropically. Missing hydrogen positions were calculated and included in the structure factor calculation. Final R(F) = 0.0949, wR(F2) = 0.185 for 1685 parameters and 9918 reflections with I > 2σ(I) and 2.91 < θ < 25.35°. Remarks on the CIF checking procedure. The H-atoms with calculated positions get Uiso proportional to the bonded C-atoms and cannot be compared to the Uiso of refined H-atoms. Unfortunately this distinction gets lost in a CIF file. There is some disorder in the structure but poor high order data does not allow to split atom positions so we get imprecise bond angles and too short bond lengths mostly for methyl groups and hexane solvent molecules.




Figure S7. ORTEP plot of structure B at the 50 % level. Solvent molecules are omitted for clarity. Supplementary crystallographic data for this paper has been deposited with the Cambridge Crystallographic Data Centre (CCDC 827388 and CCDC 827387 for structures A and B, respectively). These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. 1.3. Solid-state UV/vis spectroscopy The solid-state UV/vis absorption spectrum of 1 was recorded with a UV/Vis/NIR spectrophotometer (V-670, Jasco Inc., Tokyo, Japan) equipped with an 150 mm integrating sphere (ILN-725, Jasco Inc., Tokyo, Japan) in a powder holder against white standard barium sulfate. Prior to the measurement, the crystals were grounded. 1.4. Photo-polymerization and in situ fluorescence spectroscopy 1.4.1. Experimental set-up Light emitting diodes (LEDs) with two different wavelengths were purchased from Omicron-Laserage Laserprodukte GmbH, Rodgau-Dudenhofen, Germany (LEDMOD LAB models). The LED which emitted at 470 nm (300 mW) was used as light source for the photo-reaction. Progress of the reaction was monitored by fluorescence spectroscopy for which the second LED with an emission wavelength around 365 nm (250 mW) was used for excitation. A multimode optical fibre (50 µm core size, numerical aperture 0.12 NA, AFW Technology) was used to collect the fluorescence. The fibre and the LED were oriented perpendicular to each other in order to avoid a coupling of the excitation light into the fibre. The other end of the optical fibre was connected to a spectrometer (SP-2556 Acton Research 500 mm Imaging Spectrograph) equipped with a sensitive CCD camera (Princeton Instruments R PIXIS 256E). In our experiments we used the diffraction grating with a groove density of




150 1/mm blazed at 500 nm, which allowed us to obtain a spectral resolution of 1.4 nm. To record the fluorescence spectra, the 470 nm LED was turned off each time and the 365 nm LED was instead turned on for a 30 s integration time. The 470 nm LED was then switched on again to continue the reaction.

Figure S8. The experimental set-up for the photo-polymerization with monitoring by the in situ fluorescence spectroscopy. 1.4.2. Typical experimental procedures Method 1: The crystals (~ 10 mg) were put in a screw-cap glass vial (2 mL) together with a small magnetic stirring bar. The cap had a rubber/PTFE septum (BGB Analytik AG, Boeckten, Switzerland) through which argon gas was supplied into the vial during the reaction. A degassed mixture of methanol/water 1:2 (0.5 mL) was added to the vial. The dispersion was then irradiated with the LED (λ = 470 nm) which was placed at a distance of 2-3 cm to illuminate the entire dispersion. The dispersion was irradiated for 6 days at room temperature and kept stirring during the entire time. The cap was then removed and the solvent was evaporated in the dark at room temperature. Method 2: A sealed glass tube containing the crystals (typically, 0.1-0.2 mg) either in their mother liquor or in hexane was irradiated with the 470 nm LED placed at a distance of 1-2 cm to illuminate the entire crystal mass. The side of the tube opposite to the LED was covered with aluminium foil to reflect the light. The tube was irradiated for 6-11 days at room temperature during which time it was manually




turned every 24 h so as to ensure that the crystals were hit form all sides. After irradiation the crystals were taken out from the glass tube. Because of the heterogeneous nature of solid-state reactions, the duration of irradiation depended on subtle differences in the reaction conditions including quality and size of crystals, the distance between crystals and light source, and how the crystals were turned during the irradiation. Overall, method 1 gave better reproducible results. The conversion in method 2 was checked by Raman spectroscopy. 1.5. Exfoliation The irradiated crystals of monomer 1 were insoluble in the solvents which dissolved the non-irradiated crystals. However, the irradiated crystals could be swollen in solvents such as chloroform, 1,1,2,2-tetrachloroethane (TCE), o-dichlorobenzene (ODCB), and 1-methyl-2-pyrrolidone (NMP). The swelling process was followed by exfoliation which was slow at room temperature but could be promoted by heating to higher temperature or adding pyridine. Exfoliation turned more and more difficult the higher the conversion of the photo polymerization was. Full exfoliation down to monolayered sheets could be achieved when the crystals (with high conversion) were heated in NMP at 150 °C under argon for 3 days. Note that both the polymer and model 4 did not show any back reaction at this temperature by 1H NMR spectroscopy. 1.6. Optical (OM) and polarizing optical microscopy (POM) OM and POM observations were carried out with a Leica DM4000M optical microscope from Leica Microsystems Wetzlar GmbH, Germany. For observation of the exfoliated single sheets, the NMP solution was diluted with chloroform and dropped on an oxidized Silicon wafer (300 nm SiO2, CrysTec GmbH, Berlin, Germany). This wafer was then rinsed with chloroform and dried under ambient conditions for 3 h. 1.7. Scanning (SEM) and transmission electron microscopy (TEM) Scanning electron microscopy was carried out using a FEI NanoSEM 230 operated at 15 and 18 kV. Transmission electron microscopy (TEM) and electron diffraction (ED) were carried out using a Jeol JEM 2200FS operated at 200 kV. To observe the large crystal spacing of the molecule crystals in ED, a large camera length of nominal 200 cm was necessary. In order to rule out the presence of Moiré reflections, diffraction patterns were recorded at large and at small camera lengths. As there is no small, i.e. atomic, crystal spacing observable at small camera length, the reflections observable at large camera length must be due to the 2D polymer structure (see Figure S20). Measurements were carried out at room temperature and at liquid nitrogen temperature. While for the latter significantly more reflections were observed in the diffraction patterns, the imaging performance was lower under cryogenic conditions due to mechanical instabilities. Figure S20(d) shows the cryo-TEM image




corresponding to the diffraction pattern shown in Figure 4(D). Figure S20(a) and (b) show room-temperature diffraction patterns corresponding to Figure 4(B) and (C). As the samples were highly prone to radiation damage, the electron dose was kept below 250 e-/Å2 s. Figs. 4(C) and S20(c) were noise filtered by applying a Wiener filter. The electron irradiation causes thermal excitation and radiation damage. This circumstance limits the observable information transfer (in imaging and diffraction) to about 1 nm, even when the sample is cooled by liquid nitrogen. Spots in the power spectra of the images and Bragg reflections were not observed beyond 1 nm transfer. The lack of any atomic crystal spacing in the diffraction pattern clearly indicates that the cross-linked monomers in the partially exfoliated crystals are highly mobile, such that only the arrangement of the monomer units can be identified as individual entities. For sample preparation, a cupper grid (63 x 63 µm2) coated with a lacy carbon film (Ted Pella, Inc., Redding, Canada, Lacey Formvar/Carbon 01883) were placed on dust-free blotting paper in contact with the coated side. A few drops of dispersions of either irradiated crystals or exfoliated sheets in an organic solvent were deposited onto the grid with a glass capillary (diameter: > 30 µm), whereby the solvent was sucked into the paper through the lacy carbon film. The material on the grid was then washed with 5 drops of chloroform. The sample on the grid was dried for several hours at room temperature. Based on the model structure described in part 1.10 of the supplementary information, multi-slice simulations of TEM images and ED patterns were carried out using WinHREM software. Simulations were done for crystal models with a thickness of 8 layers. This thickness of the model reflects the thickness of the sheets in the experimental images which was assessed by energy-filtered imaging applying the log-ratio technique. The simulations in Figure S21 were done for 200 kV with a beam convergence angle of 0.2 mrad, a defocus spread of 2.5 nm, a defocus of -300 nm and a constant of third order spherical aberration of 1 mm. The images were then convoluted by a Gaussian function to match the experimentally observable information transfer of about 1 nm. 1.8. Atomic force microscopy (AFM) AFM measurements were carried out with a Nanoscope® IIIa Multi Mode Scanning probe microscope (Digital Instruments, San Diego, CA) operated in the tapping mode with an “E” scanner (scan range 10 x 10 µm2) or a “J” scanner (scan range 100 x 100 µm2) and operated in the tapping mode at room temperature in air. Olympus silicon OMCL-AC160TS cantilevers (Atomic Force F&E GmbH, Mannheim, Germany) were used with a resonance frequency between 200 and 400 kHz and a spring constant around 42 N/m. For sample preparation, a cupper grid (63 x 63 µm2) coated with a lacy carbon film (Ted Pella, Inc., Redding, Canada, Lacey Formvar/Carbon 01883) were placed on dust-free paper in contact with the coated side. A few drops of the dispersion of the exfoliated sheets in an organic solvent were deposited onto the grid with a glass capillary (diameter: > 30 µm) whereby the solvent was blotted by the paper through the lacy carbon film. The material on the grid was then washed with 5 drops of chloroform. The grid was then turned over and placed on a freshly cleaved mica substrate (PLANO W. Plannet GmbH, Wetzlar, Germany). In order to transfer the




material from the lacy carbon support onto the mica surface, a few drops of chloroform were added from the back side of the grid through the lacy carbon onto the mica surface. The grid was then removed. The mica plate was rinsed with chloroform and dried at 80 °C in vacuum over night. 1.9. Raman spectroscopy Raman measurements were performed on a Renishaw Raman spectroscopy system 1000 dual laser 633/782 nm equipped with a PULNIX colour camera TMC-312. Measurements were performed using the 782 nm laser at a nominal power of 27 mW. The Stokes intensities were measured. Prior to the measurements, the crystals were powdered by grinding them between two microscopy glass slides. The background of the glass slide was irrelevant.

1.10. Computer simulation The structures were simulated using the Dreiding Force Field44 as implemented in the Forcite Package of Materials Studio version 5.5 (Accelrys, Inc. 10188 Telesis Court, Suite 100, San Diego, CA 92121 USA). Geometries were prepared by adding appropriate bonds to and/or removing solvent molecules from the experimental crystal structure of the TCE/THF solvated monomer. Structures were optimized as full crystal in space group P-3 using ultra-tight convergence criteria.




2. Supplementary figures

Figure S9. Order within the single crystals of monomer 1. (a) The crystals grown from TCE/THF were plate or rod like. Hexagonal faces were found as common feature to which the internal layers were aligned in parallel. (b) Monomer 1 has some conformational freedom in solution owing to the possible rotations around the acetylenic axes. Consequently it can adopt two triangular enantiomeric conformations in the crystal. The two conformers are laterally packed in an alternatingly upside down fashion leading to a dense hexagonal packing (left). The DEA and TPB units are segregated into separate sublayers (right). (c) Each main layer is composed of DEA and TPB sublayers, whereby the DEAs constitute the central sublayer sandwiched by two TPB sublayers. The main layers are interdigitated into one another through the TPB units. The DEA sublayers are thus “insulated” from each other allowing for reactions to take place only within them.




Figure S10. In situ fluorescence (FL) decay upon photo irradiation (470 nm, 300 mW) of monomer crystals under Ar (a). For each FL measurement the excitation wavelength was temporally switched to 365 nm (250 mW). Note that these decays depend on the conditions including quality and size of crystals and whether or not crystals are stirred during irradiation. The UV/vis spectrum of the monomer crystal (b) is red-shifted in comparison to the solution spectrum34,35 and shows absorption at 470 nm (b). The irradiation wavelength was set to this value to allow for an as homogeneous reaction course as possible45.




Figure S11. OM images of non-irradiated monomer crystals on a glass plate with a few drops of TCE at room temperature to prove complete dissolution. The pictures were taken (a) before and (b) 60 s (c) 90 s and (d) 120 s after the addition of TCE. The crystals floated in TCE and changed their positions during the observation as shown by red arrows. The yellow colour is ascribed to the monomer. For irradiated crystals under the same conditions, see Figure S12. Scale bars: 100 µm.




Figure S12. OM images of the irradiated crystals on a glass plate (a) 1 min and (b) 5 min after addition of TCE at room temperature. SEM images of irradiated crystals kept in TCE for 1 h at room temperature and then deposited on a lacy-carbon coated cupper grid (c and d). The remaining hexagonal features and edges show that the irradiated crystals are insoluble. For non-irradiated monomer crystals under the same conditions, see Figure S11. Scale bars: (c) 100 µm; (d) 20 µm.




Figure S13. OM (a,b,c) and POM images (d,e,f) of monomer crystals (a,d) before and (b,e) after photo treatment and (c,f) after the irradiated crystals were kept in chloroform for 7 days. Birefringence remained after the photo treatment (e) but vanished almost completely by the exposure to solvent (f). The curvatures of the rod-like crystals suggest a swelling process. See also Figure 2. Scale bars: 50 µm.




Figure S14. OM images of the irradiated monomer crystals showing the onset of exfoliation: (a) 10 s and (b) 5 min after addition of a few drops of pyridine to crystals in chloroform that had been kept in this solvent for 7 days at 20 °C. Insets are magnification of the hexagons which went out of alignment (a-1 and b-1) and a hexagon which looks already thin enough to be bent (b-2). Scale bars: 100 µm.




Figure S15. SEM images of irradiated crystals exfoliated to varying degrees in chloroform/pyridine. For all images the crystals were kept in chloroform for 1 day at 20 °C and for an additional half hour after the addition of a few drops of pyridine. (a) Swollen crystal with its hexagonal cross-section still maintained; (b) rose-like feature suggesting onset of exfoliation; (c) Sheet-like feature thin enough to see the lacy carbon support through it. Note the crisp edges as well as the overall hexagonal shape of the sheet indicating its originating from a hexagonal crystal. See also Figs. 2 and S18 for comparison. Scale bars: (a) 20 µm; (b) 20 µm; (c) 4 µm.




Figure S16. AFM images on mica of sheets incompletely exfoliated from the irradiated crystals. The crystals were kept in chloroform for 1 day and left for an additional 1 day with some NMP added. (a) Phase image; (b) height image; (c) height profiles along the lines indicated in the height image. Interestingly, not only flat but also creased or overlaid sheets are observed. Note that there are only very few hexagonal features because the crystals used for this particular exfoliation experiment were mechanically ground up into pieces by stirring during the photoreaction. Thickness of the sheets observed varied up to 10 nm. The mica surface was largely covered with a thin layer (2 - 4 nm) on which the sheets rest. The nature of this layer is still unclear but could be due to fragments of sheets. See also Figs. 3 and S19 for comparison.




Figure S17. OM image of sheets exfoliated from irradiated crystals. The crystals were heated at 150 oC in NMP for 3 days and deposited on a SiO2 substrate (2). Remaining hexagonal features could be observed in whole or in parts (see the sheets marked with circles). The majority of the features are not hexagonal but rarther more or less round-shaped. There are several potential reasons for this which includes (a) relaxation by conformational changes of individual repeat units within a sheet after liberation from the tight register in the crystal and (b) mechanical destruction by shear forces the sheets are exposed to at 150 °C in NMP during exfoliation and after. Scale bar: 50 µm.




Figure S18. SEM image of sheets exfoliated from the irradiated crystals. The crystals were heated at 150 oC in NMP for 3 days and then deposited on a lacy-carbon coated cupper grid. The crystals had largely disappeared leaving behind countless thin sheets which can be seen trapped on the support. In an overview image (a), some of them are indicated by yellow arrows. In magnified images (b and c), the sheets are marked with red circles. These sheets are so thin (left) that the contrast was enhanced to identify them (right). Red arrows point to their edges. Note that these thin sheets were found labile to the electron beam; cracks appeared and developed during observation. See Figure S15 for comparison. Scale bars: (a) 200 µm; (b & c) 5 µm.




Figure S18. Continued.




Figure S19. AFM height image of sheets exfoliated from the irradiated crystals (a). The crystals were heated at 150 oC in NMP for 3 days and deposited on mica. Small fragments were filtered off prior to deposition. Height analysis proves a uniform thickness of ~ 2.5 nm. Height profiles along lines A and B are displayed (b). This thickness is in good agreement to the estimated thickness of a monolayer (2.4 nm) (c). For magnification, see Figure 3. Many of the sheets have small blobby features associated with them, whose origin is presently under investigation.




Figure S20. Electron diffraction patterns recorded at room temperature using a nominal camera length of 200 cm (a) and 20 cm (b), respectively. As there is no atomic crystal spacing observable in (b), the weak crystal reflections in (a) must be due to the arrangement of the monomer units in the polymer sheets. The presence of reflections due to a Moiré effect can thus be ruled out. (c) TEM micrograph recorded at cryogenic conditions. Due to mechanical instabilities related to the cryo-holder used, the 2D polymer structure is less clear but the power spectrum in (d) clearly shows the presence of the 2D network.




Figure S21. X-ray single crystal structure of monomer 1 (a) and simulated polymer crystal structures with (b) and without incorporated THF molecules (c) together with the corresponding simulated TEM images and ED patterns. The simulations assume the topochemical [4+2] cycloaddition (see Figure S22). Note that the solvent molecules are not displayed. Unit cell parameters (trigonal, P-3) are: (a) a = b = 22.205, c = 12.509 (b) a = b = 20.980, c = 14.091, (c) a = b = 19.495, c = 16.425 Å. α = β = 90.000, γ = 120.000° for all. The unit cell volumes are 5341, 5371 and 5406 Å3, respectively.




Figure S22. Proposed [4+2]-cycloaddition on the basis of the monomer crystal structure. Note that adjacent monomers are oriented upside down (antiparallel). 50 % of the alkyne moieties are opposed to anthracene moieties of the next neighbor and the other 50 % remain unpaired (and should therefore not undergo a reaction) (a). The distances between the carbon atoms of the anthracene-alkyne pairs suggest a [4+2]-cycloaddition38,39 as the mechanism of the covalent fixation of the translational crystalline order during irradiation (b).




3. Supplementary discussion on Raman analysis

The Raman spectra of irradiated crystals (after rinsing with ODCB), which hereafter is referred to as polymer, was compared with those of monomer 1 and model compounds 3-13 (Figure S1) aiming at structure elucidation of the polymer. First, the polymer was compared with monomer 1 and models 3 and 4 (Figure S23). A signal around 2200 cm-1 (marked as a) is attributed to C≡C stretching and observed for all these three compounds confirming that the polymer still contains alkyne units (as expected). Comparison between 3 and 4 indicates that signals c and d are characteristic of the 1,8-anthrylene unit. These signals disappear if the 1,8-anthrylene unit undergoes a [4 + 2] cycloaddition with the alkyne unit. The intensity of signal b, which is due to C=C stretching, increases at the same time. The same tendency is found when the Raman spectra of monomer 1 and polymer are compared. For the signal of the polymer remaining around the Raman shift d, see below.

Figure S23. Raman spectra of monomer 1 and the polymer in comparison with those of their models 3 and 4, respectively. C≡C and C=C stretching signals are commonly observed at the Raman shifts a and b, respectively. Signals c and d which are characteristic of 1,8-anthrylene are missing in the polymer. Next, the polymer was compared with models 4-9 (Figure S24). Models 4-7 represent the expected [4+2]-cycloaddition product and other conceivable products such as




dimers from [4+4]-cycloaddition of the anthrylenes (anti and syn) as well as a derivative from oxidation, respectively. Comparison between the polymer and models 4-7 shows that the absence of signals c and d (see above) is common to all of them. Models 8 and 9 were considered here to help identify the Raman shift of non-aromatic C=C bonds. Such bonds are characteristic for the [4+2] cycloaddition proposed for the polymer. Unfortunately the broad peak of the polymer around Raman shift b covers the region which includes both aromatic and non-aromatic C=C stretching signals so that they cannot be distinguished from each other. Comparison between models 4 and 8 confirms that the C≡C stretching signal a vanishes once the alkyne has been consumed by the [4 + 2] cycloaddition with the anthrylene. Comparison of polymer with model 7 suggests partial oxidation of the anthrylene units in the polymer (see below). Indicative for this is the very low intense signal in the polymer spectrum right at the wavelength that is characteristic C=O stretching (shift e)

Figure S24. Raman spectra of the polymer in comparison with models 4-7 representing relevant structural fragments of the polymer. Models 8 and 9 were used in an attempt to identify non-aromatic C=C stretching signal which would be characteristic of a [4+2] cycloaddition product.




Further, the polymer was compared with monomer 1 and models 10-12 which represent the TPB, the cap and the DEA parts, respectively (Figure S25). The signal f is common to the polymer, monomer 1 and model 11 suggesting its assignment as C=O stretching of the cap. The polymer exhibits two signals g and h in the region where signal d characteristic of the anthrylene resides in the monomer (see above). They could originate from the TPB or the cap part; it is slightly shifted to the corresponding models. It should be noted that the polymer, monomer 1 as well as models 10 and 11 show a distinct signal i around 1000 cm-1. Because such a signal is absent from models 12 and 13 it should neither be associated with anthrylene units nor with its [4+4] dimerization products. Signal i was therefore assigned to the phenylene units of both TPB and cap and, importantly, should therefore remain largely unaffected by the polymerization. Thus, signal i suggested itself as internal standard for the discussion that follows.

Figure S25. Raman spectra of monomer 1 and polymer in comparison with those of model compounds representing parts of their structures. Models 10-12 correspond to the TPB, the cap and the DEA parts, respectively. Model 13 is used for the assignment of signal i. Finally, Raman spectra were used to estimate the conversion of the photoreaction inside the monomer crystal. For that purpose Figure S26 compares the spectra of the non-irradiated monomer crystal with that of the irradiated crystal before and after rinsing with ODCB. Peak intensities were compared with one another by using signal i as an internal reference. Note that the crystals were ground fine enough to be




isotropic for the Raman analysis. Several different spots (area: ~ 3 µm2) were tested for each sample in order to check the reproducibility. Whenever conversion is below 100%, irradiated crystals before rinsing contain both monomer and polymer. As can be seen, the intensities of signals c and d (characteristic for anthrylene units) decrease as polymerization progresses, confirming that anthrylene units are involved in the polymerization. Concomitantly signal b grows. This finding agrees to what was expected for the anthrylene, namely to react at the 9,10 positions. Furthermore, intensity of the signal a characteristic of the alkyne also decreases steadily with progressing polymerization. This suggests that the alkyne is the counterpart of the reaction with the anthrylene, while it does not unequivocally prove it. Comparison of the polymer (the irradiated crystals after rinsing with ODCB) with the monomer shows that the peak intensity of signal a decreases by 58 %. This reasonably fits the expectation that 50 % of all alkynes should react with anthrylenes in the monomer crystal (Figure S22). This supports the view that the polymerization proceeded with keeping the original crystal order and thus in a topochemical manner. For the irradiated crystals before rinsing, the conversion was estimated to be 66-83 %. Note that any residual anthracene intensity could be removed by rinsing the irradiated crystals with ODCB. Monomers of which at least one anthracene has reacted are an integral part of the formed 2D network and can therefore not be removed by rinsing. It is thus concluded that there are either small domains of unreacted monomers (though it is difficult to imagine how solvent could reach these domains) within the crystal or (more likely) the monomer is outside the crystals as an amorphous aggregate. In this aggregate the monomers are not preorganized and thus could remain unreacted throughout the irradiation. Further investigation is underway.

Figure S26. Raman spectra of the crystals of monomer 1, the polymer and their intermediate. The spectra were compared with one another using the signal i for calibration of peak intensities. It was revealed that the signals characteristic of the anthrylene (c and d) and the alkyne (a) decreased with progress of the polymerization.




This suggests they reacted with each other as expected from the molecular arrangement in the monomer crystal. 4. Supplementary overview of some 2D polymers’ characteristics useful for applications

Figure S27. Illustration of some important aspects of potential applications and the property profile of 2D polymers. Crumpled objects were taken from http://www.flickr.com/photos/tactom/3084925574/ 5. Supplementary references 40. Kissel, P., Breitler, S., Reinmüller, V., Lanz, P., Federer, L., Schlüter, A. D. &

Sakamoto, J. An easy and multigram-scale synthesis of versatile AA- and AB

type m-terphenylenes as building blocks for kinked polyphenylenes. Eur. J.

Org. Chem. 2009, 2953-2955 (2009).

41. Kissel, P., Weibel, F., Federer, L., Sakamoto, J. & Schlüter, A. D. An easy and

multigram-scale synthesis of antracene-1,8-ditriflate. Synlett 2008, 1793-1796

(2008).

42. Sheldrick G. M. A short history of SHELX. Acta Cryst. A64, 112-122 (2008).




43. Dolomanov O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. &

Puschmann, H. OLEX2: a complete structure solution, refinement and analysis

program. J. Appl. Cryst. 42, 339-341 (2009).

44. Mayo, S. L., Olafson, B. D. & Goddard, W. A., III. DREIDING: A generic

forcefield. J. Phys. Chem. 94, 8897-8909 (1990).

45. Novak, K., Enkelmann, V., Köhler, W., Wegner, G. & Wagener, K. B.

Homogeneous photodimerization and thermal back reaction of a

styrylpyrylium triflate. Mol. Cryst. Liq. Cryst. 242, 1-8 (1994).


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