Luminescent Mechanochromic 9 Anthryl Gold(I) Isocyanide Complex with an Emission Maximum at 900 nm after Mechanical Stimulation

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1 Supporting Information Luminescent Mechanochromic 9 Anthryl Gold(I) Isocyanide Complex with an Emission Maximum at 900 nm after Mechanical Stimulation Tomohiro Seki, 1* Noriaki Tokodai, 1 Shun Omagari, 2 Takayuki Nakanishi, 2 Yasuchika Hasegawa, 2 Takeshi Iwasa, 3 Tetsuya Taketsugu, 3 Hajime Ito 1* 1 Division of Applied Chemistry & Frontier Chemistry Center, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido , Japan 2 Division of Applied Chemistry, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido , Japan 3 Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo , Japan seki@eng.hokudai.ac.jp; hajito@eng.hokudai.ac.jp Contents 1. General S2 2. Synthesis and preparation of the single crystals S3 3. Optical properties of 2 S6 4. Photographs of 3α, 3β, 3α ground, and 3β ground S8 5. Optical properties of 3α and 3β S9 6. Morphology changes upon grinding S10 7. Photophysical properties of 3 in various forms S11 8. DSC measurements of 3α and 3β S13 9. Data for single-crystal X-ray structural analyses S Theoretical calculations based on the single-crystal structures S Optical properties of 3 in solution S Powder XRD patterns of 3α and 3β S TGA and NMR spectroscopy of 3α, 3β, and 3γ S Crystal structure of 3γ S IR spectroscopy for 3 and other previously reported related complexes (7A 7D) S Polymorph 3δ S References S NMR Charts S38 - S1 -

2 1. General All commercially available reagents and solvents are of reagent grade and were used without further purification unless otherwise noted. Solvents for the synthesis were purchased from commercial suppliers, degassed by three freeze-pump-thaw cycles and further dried over molecular sieves (4 Å). NMR spectra were recorded on a JEOL JNM-ECX400P or JNM-ECS400 spectrometer ( 1 H: 400 MHz; 13 C: 99.5 MHz) using tetramethylsilane and CDCl 3 as internal standards, respectively. Emission and excitation spectra were recorded on a Hitachi F-7000 spectrometer and on a Horiba Fluorolog-3 with a NIR-PMT Hamamatsu R Absorption spectra were recorded on a Hitachi U-2910 spectrometer. The emission quantum yields of the solid samples were recorded on a Hamamatsu Quantaurus-QY Plus spectrometer with an integrating sphere. Emission lifetime measurements were recorded on a Hamamatsu Quantaurus-Tau spectrometer. DSC measurements were recorded on a SII DSC 7020 heat flux meter. TGA traces were recorded on a SII EXSTAR Elemental analyses and low- and high resolution mass spectra were recorded at the Global Facility Center at Hokkaido University. Photographs were obtained using Olympus BX51 or SZX7 microscopes with Olympus DP72, Nikon D5100 or RICOH CX1 digital cameras. Powder diffraction data were recorded at on a Rigaku SmartLab diffractometer with Cu-K α radiation and D/teX Ultra detector covering 5 60 (2θ). Simulated powder patterns of 3α and 3β were generated with Mercury 3.5 from the structures determined by single-crystal and powder X-ray diffraction analyses. Thermal gravimetric analysis profiles were recorded on Bruker TG-DTA2010SAT. - S2 -

3 2. Synthesis and preparation of the single crystals i) Synthesis of 1-naphthylzinc iodide (5). 1 I + LiCl + Zn BrCH 2 CH 2 Br Me 3 SiCl THF 50 C, 12 h 5 ZnI LiCl Anhydrous LiCl (84.8 mg, 2.00 mmol, 1.0 equiv) was placed in a N 2 -flushed flask and dried 25 min at 150 C in vacuo. Zinc powder (196 mg, 3.00 mmol, 1.5 equiv), was added under N 2 and heterogeneous mixture of Zn and LiCl was dried again 20 min at 150 C in vacuo. The reaction flask was evacuated and refilled with N 2 three times. THF (2 ml) was added and Zn was activated by BrCH 2 CH 2 Br (5 mol %) and Me 3 SiCl (1 drop). The powder of 1-iodonaphthalene (508 mg, 2.00 mmol) was added at the room temperature. The reaction mixture was stirred at 50 C. The completion of the insertion reaction was checked by GC analysis of reaction aliquots. After 12 h, an aliquot of organozinc reagent was titrated using iodine. The titrated organozinc solution of 5 in THF was carefully separated from the remaining zinc powder using a syringe and transferred to another dry and N 2 -flushed Schlenk flask. ii) Synthesis of 1-naphthyl(phenyl isocyanide)gold(i) (2). ZnI LiCl + Cl Au C N THF Au C N 4 h, 0 C Chloro(phenyl isocyanide)gold(i) 4 (336 mg, 1.00 mmol) and THF (0.6 ml) were added to a screw-top test tube and stirred at 0 ºC. Then organozinc iodide reagent 5 (1.5 equiv) in THF was added to the flask. After 4 h stirring, the reaction was quenched by addition aqueous NH 4 Cl and then extracted three times with CHCl 3. The combined organic layer was dried by magnesium sulfate. After filtration, the solvents were removed by a rotary evaporator. The residue was purified by column chromatography (SiO 2, CH 2 Cl 2 /hexane 1:3) and crystallized from hexane/ch 2 Cl 2 to give 2 as an analytically pure white solid (282 mg, 0.66 mmol, 66 %). 1 H NMR (400 MHz, CDCl 3, ): 7.34 (m, 7H), 7.49 (m, 1H), 7.61 (d, J = 7.9 Hz, 1H), 7.66 (qd, J = 1.6 Hz, J = 6.6 Hz, 1H), 7.7 (dd, J = 1.4 Hz, J = 8.3 Hz, 1H), 8.52 (dd, J = 1.8 Hz, J = 8.1 Hz, 1H). 13 C NMR (100 MHz, CDCl 3, ): (CH), (CH), (CH), (CH), (CH), (CH), (CH), (CH), (CH), (CH), (C), (C). IR (neat, cm 1 ): 3050 (m), 2205 (s), 1584 (w), 1495 (w). HRMS FAB (m/z): [M] + Calcd for C 17 H 12 AuN, ; Found, Anal. Calcd for C 17 H 12 AuN: C, 47.79; H, 2.83; N, Found: C, 47.62; H, 2.78; N, S3 -

4 iii) Synthesis of 9-anthrylzinc iodide (6). 1 I + LiCl + Zn BrCH 2 CH 2 Br Me 3 SiCl THF 50 C, 36 h ZnI LiCl 6 Anhydrous LiCl (503 mg, 11.9 mmol, 1.0 equiv) was placed in a N 2 -flushed flask and dried 25 min at 150 C in vacuo. Zinc powder (1.17 g, 17.9 mmol, 1.5 equiv), was added under N 2 and heterogeneous mixture of Zn and LiCl was dried again 30 min at 150 C in vacuo. The reaction flask was evacuated and refilled with N 2 three times. THF (25 ml) was added and Zn was activated by BrCH 2 CH 2 Br (5 mol %) and Me 3 SiCl (2 mol %). Then, the powder of 9-iodoanthracene (3.61 g, 11.8 mmol) was added portionwise at the room temperature. The reaction mixture was stirred at 50 C. The completion of the insertion reaction was checked by GC analysis of reaction aliquots. After 36 h, an aliquot of organozinc reagent was titrated using iodine. The titrated organozinc solution of 6 in THF were carefully separated from the remaining zinc powder using a syringe and transferred to another dry and N 2 -flushed Schlenk flask. iv) Synthesis of 9-anthryl(phenyl isocyanide)gold(i) (3). ZnI LiCl + Cl Au C N THF Au C N 3.5 h, 0 C To chloro(phenyl isocyanide)gold(i) (4, g, 1.5 mmol), THF (5 ml) was added under N 2 atmosphere. After cooling to 0 C, a THF solution of organozinc iodide reagent 6 (3.8 ml, 1.71 mmol, M) was added dropwise with stirring. After 3.5 h stirring, the reaction was quenched by the addition of a phosphate buffer solution and then extracted with CH 2 Cl 2 three times and washed with H 2 O and brine. The organic layers were collected and dried over MgSO 4. After filtration, the solvent were removed in vacuo. The resulting solid was purified by reprecipitation with CH 2 Cl 2 /hexane and the precipitate was filtered. The residues were dried under reduced pressure to give 3 as a pale-yellow powder (0.618 g, 1.29 mmol, 86 %). 1 H NMR (400 MHz, CDCl 3, δ): (m, 4H), (m, 5H), (m, 2H), 8.21 (s, 1H), (m, 2H). 13 C NMR (400 MHz, CDCl 3, ): (CH), (CH), (CH), (C), (CH), (CH), (CH), (CH), (CH), (C), (CH), (C), (C). MS-EI (m/z): [M+H] + calcd for C 21 H 14 AuN, ; found, Anal. Calcd for C 15 H 12 AuNO 2 : C, 52.84; H, 2.96; N, Found: C, 52.69; H, 2.82; N, S4 -

5 Crystallization of 3 under various conditions often afforded two or more polymorphs of 3 concomitantly (i.e., 3α and 3β or 3β and 3γ). We described the preparation procedure for obtaining a specific polymorph as a major product as follows (only 3β can be selectively obtained in its pure form by the following crystallization procedure). After the following procedures, complete separation of each pure polymorph was performed by hand using a microscope. Preparation of Polymorph 3α: The polymorph 3α is obtained by rapid crystallization. Typically, 3 (5 mg) is dissolved in 0.5 ml of CH 2 Cl 2 in a vial and methanol (1.5 ml) was carefully layered. After standing for a day at 25 C, blue-emitting crystals 3α are formed. Preparation of Polymorph 3β: The polymorph 3β is obtained by slow crystallization. Typically, 3 (250 mg) is dissolved in 20 ml of CH 2 Cl 2 in a vial and hexane (60 ml) was carefully layered. After standing for several days at 25 C, yellow crystals of 3β are formed. Preparation of Polymorph 3γ: The powder form of polymorph 3γ was obtained by reprecipitation. Typically, 3 (100 mg) was dissolved in CH 2 Cl 2 (1 ml), before this solution was added dropwise to methanol (20 ml) at 0 C. Precipitates were filtered and dried under reduced pressure to give white (3α) or yellow (3γ) powders. Although we cannot control which polymorphs (3α or 3γ) are formed, the resulting polymorph (3α or 3γ) is always obtained in pure form by this method. The single crystal of 3γ can be obtained by the crystallization condition similar to that of 3β. However, 3γ is always formed concomitantly with other polymorphs, i.e., 3α and 3β. - S5 -

6 3. Optical properties of 2 Figure S1. Excitation (dashed lines) and emission spectra (solid lines) of 2 in CH 2 Cl 2 at room temperature. λ ex = 235 nm. λ em = 351 nm. [2] = M. Figure S2. Normalized emission (solid lines) and excitation (dashed lines) spectra of unground (green lines, λ ex = 375 nm, λ em = 488 nm) and ground solids of 2 (orange lines, λ ex = 375 nm, λ em = 599 nm) at room temperature. - S6 -

7 Table S1. Emission maximum wavelength (λ em,max ) of various states of 1, 2 and 3 λ em,max of unground samples / nm λ em,max of ground samples / nm 1 460, , 523, α β 710, 786, γ S7 -

8 4. Photographs of 3α, 3β, 3α ground, and 3β ground Figure S3. Photographs of 3α, 3α ground, 3β, and 3β ground taken under room light. - S8 -

9 5. Optical properties of 3α and 3β Figure S4. Normalized emission (solid lines) and excitation (dashed lines) spectra of 3α (blue lines, λ ex = 365 nm, λ em = 500 nm) and 3α ground (dark blue lines, λ ex = 465 nm, λ em = 894 nm) at room temperature. Figure S5. Normalized emission (solid lines) and excitation (dashed lines) spectra of 3β (red lines, λ ex = 461 nm, λ em = 710 nm) and 3β ground (dark red lines, λ ex = 467 nm, λ em = 898 nm) at room temperature. - S9 -

10 6. Morphology changes upon grinding Figure S6. Optical microscopic (upper) and SEM images (lower) of 3α and 3α ground. - S10 -

11 7. Photophysical properties of 3 in various forms Figure S7. Emission decay profiles of (a) 3α (λex = 375 nm, λem = 448 nm), (b) 3β (λex = 470 nm, λem = 700 nm), (c) 3γ (λex = 470 nm, λem = 800 nm), (d) 3ground (λex = 470 nm, λem = 800 nm), 3 in CH2Cl2 at a concentration of (e) M (λex = 370 nm, λem = 700 nm) and (f) M (λex = 280 nm, λem = 406 nm). 3ground samples were prepared by grinding of the mixture of 3α, 3β, and 3γ. - S11 -

12 Table S2. Photophysical properties of 3 Φ em τ av / μs e,f τ 1 / μs f τ 2 / μs f τ 3 / μs f τ 4 / μs f / % (λ em / nm) (A / -) (A / -) (A / -) (A / -) 3α 0.50 a (445) (0.971) (0.029) - - 3β 0.08 b 1.8 (700) (0.972) (0.025) 1.9 (0.003) - 3γ 0.09 b 1.6 (800) (0.671) (0.303) 0.54 (0.018) 2.2 (0.008) 3 ground g 0.09 b 0.69 (800) (0.972) 0.70 (0.028) in CH 2 Cl 2 c = M 6.0 c 0.14 (406) 0.14 (1.000) in CH 2 Cl 2 c = M 0.5 d 23 (700) 15 (0.510) 28 (0.490) - - a λ ex = 375 nm. b λ ex = 475 nm. c λ ex = 248 nm. d λ ex = 433 nm. e τ av = (A 1 τ A 2 τ ) / (A 1 τ 1 + A 2 τ 2 + ). f λ ex of 3α: 375 nm; λ ex of 3β, 3γ, and 3 ground : 470 nm; λ ex of 3 in a CH 2 Cl 2 solution at a concentration of M: 280 nm; λ ex of 3 in a CH 2 Cl 2 solution at a concentration of M: 370 nm. g 3 ground samples were prepared by grinding of the mixture of 3α, 3β, and 3γ. - S12 -

13 8. DSC measurements of 3α and 3β Figure S8. DSC traces of (a) 3α and (b) 3β at a heating/cooling rate of 10 C min 1. - S13 -

14 9. Data for single-crystal X-ray structural analyses Single-crystal X-ray structural analyses were carried out on a Rigaku R-AXIS RAPID diffractometer using graphite monochromated Mo-K radiation. The structure was solved by direct methods and expanded using Fourier techniques. Non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined using the riding model. All calculations were performed using the CrystalStructure crystallographic software package except for refinement, which was performed using SHELXL Confirmation that Solvent was Not Included: We checked the maximum residual electron density in 3α, 3β and 3γ. The maximum and minimum peaks in the final differential maps were 2.02 e and 2.51 e [Å 3 ], respectively, for 3α; 3.86 e and 2.78 e [Å 3 ], respectively, for 3β; 1.84 e and 2.07 e [Å 3 ], respectively, for 3γ. These values are within the range of ±0.075 e Z max = ±5.9 [Å 3 ] for the complex 3, where Z max denotes the maximum atomic number in the lattice. This indicated that no residual electron density that could be assigned to other molecules, such as solvent, was present in the crystal structure. This is a standard analysis to identify small molecule inclusion in crystal structures. - S14 -

15 Table S3. Summary of X-ray crystallographic data for 3α, 3β, and 3γ. Polymorph 3α 3β 3γ CCDC Name CCDC CCDC CCDC Empirical Formula C 21 H 14 AuN C 21 H 14 AuN C 21 H 14 AuN Formula Weight Crystal System monoclinic monoclinic monoclinic Crystal Size / mm a / Å (4) (7) (5) b / Å (9) (3) (3) c / Å (10) (7) (7) α / β / (2) (10) (11) γ / V / Å (17) (1) (17) Space Group P2 1 /n (#14) P2 1 /n (#14) P2 1 /n (#14) Z value Dcalc / g cm Temperature / K max / (MoK ) / cm No. of Reflections Measured Total: Unique : 3686 (R int = ) Total: Unique : 3649 (R int = ) Total: Unique : 5658 (R int = ) Residuals: R (I > 2.00 (I)) / % Residuals: wr (All reflections) / % Goodness of Fit (GOF) Maximum peak in 2.02 e 3.86 e 1.84 e Final Diff. Map / Å 3 Minimum peak in 2.51 e 2.78 e 2.07 e Final Diff. Map / Å 3 - S15 -

16 Figure S9. Single-crystal structure of 3α. - S16 -

17 Figure S10. Single-crystal structure of 3β. - S17 -

18 10. Theoretical calculations based on the single-crystal structures Spin restricted density functional theory (DFT) calculations on 3α and 3β were carried out at the RI-B3LYP level 3 5 of theory, using the def-sv(p) basis sets 6 with the 60-electron relativistic effective core potential 7 for Au, as implemented in TURBOMOLE. 8,9 Electronic absorption spectra were simulated by time-dependent density functional theory (TDDFT) calculations, in which the line spectra were convoluted by a Lorentzian (width: 10 nm). Initial geometries for the monomer of 3α and 3β were derived from the experimental single-crystal structures, and the positions of the H atoms were optimized using the Spartan 10 MMFF force-field calculation 14 prior to the DFT calculations. It should be noted that the monomers of 3α and differ with respect to the dihedral angle θ (3α: ; 3β: ). The TDDFT calculations indicated that the excitation energies and electronic configurations of S 1 (HOMO LUMO) and S 2 (HOMO LUMO+1/LUMO+2) are similar for 3α and 3β (Figure S11b). In 3α and 3β, the LUMO+1 and LUMO+2 are energetically very close to each other. In contrast, the oscillator strength differs substantially, which is evident from the simulated absorption spectra (Figure S11a). This difference should be attributed to the different dihedral angles of 3α and 3β. In 3α, the S 0 S 1 (HOMO LUMO) transition is optically forbidden (oscillator strength, f = ), due to the almost perpendicular (θ = ) alignment of the two aromatic moieties. Consequently, the S 0 S 2 (HOMO LUMO+1) transition at 419 nm represents the lowest optically allowed transition of 3α (f = 0.192). The absorption of 3α (S 2 ) can be rationalized in terms of a combination of the intra-ligand (anthracene) π π* and ligand-to-metal transitions. In contrast, both the S 0 S 1 (HOMO LUMO; f = 0.052) and the S 0 S 2 (HOMO LUMO+2; f = 0.145) transition are optically allowed in 3β, due to the substantial deviation from the perpendicular alignment (θ = ). For 3β, the S 0 S 1 transition, i.e., the lowest optically allowed transition, can be expressed as a combination of the inter-ligand (anthracene phenyl) and ligand-to-metal charge transfer transitions. Since the average emission lifetime of 3α is relatively short (τ av < 10 9 s, Table S1), the emission characteristics should be similar to the absorption characteristics, and it is thus reasonable to assume that the emission energy of 3α is higher than that of 3β, whose emission should most likely be attributed to the T 1 S 0 transition. - S18 -

19 Figure S11. The results of the DFT and TDDFT calculations on 3α and 3β. a) Simulated absorption spectra; b) lowest-energy optical transitions; c) selected frontier orbitals for 3α and 3β. - S19 -

20 11. Optical properties of 3 in solution Solution-state studies on 3 (Figure S12 S14) indicated that the emission of 3α does not arise from the excimer state. Figure S12 shows the concentration-dependent UV/vis absorption spectra of 3 in tetrachloroethane at room temperature. The results indicate that the absorption properties of 3 in solution remain virtually unchanged upon changing the concentration, i.e., in solution, 3 should exist as monomers in the ground state over the entire concentration range. The absorption of 3 exhibited a vibronic structure, which is typical for anthracene molecules. Thus, the absorption of 3 should be attributed to the π π* transition that is localized on the anthracene moiety. The emission spectrum of 3 at a concentration of M (solid line in Figure S13a) also showed the vibronic structure typical for an anthracene-type emission, and the emission spectrum mirrors the corresponding absorption band (Figure S12a). This result indicates that the emission of 3 in solution (in the 10 6 M range) originates from the π π* excited state. Upon increasing the concentration of 3, the entire emission band gradually red-shifted (Figure S13 and S14), and the emergence of new emission band(s) such as excimer bands at longer wavelengths was not observed. Thus, 3 should not form typical anthracene excimers in solution, not even at high concentrations. 15 As a result of the red-shifted emission band, the emission bands of 3 in solution become comparable to the emission of 3α (Figure S14), which corroborates the notion that the emission of 3α should not originate from the formation of excimers. - S20 -

21 Figure S12. UV/vis absorption spectra of 3 in tetrachloroethane at room temperature; a) [3] = M; b) [3] = M; c) [3] = M; d) [3] = M; e) [3] = M. - S21 -

22 Figure S13. Excitation (dashed lines) and emission spectra (solid lines) of 3 in CH 2 Cl 2 at room temperature; λ ex = 406 nm; λ em = 248 nm; a) [3] = M; b) [3] = M; c) [3] = M; d) [3] = M. Figure S14. Comparison of the concentration-dependent emission spectra of 3 in CH 2 Cl 2 with the emission spectrum of 3α. - S22 -

23 12. Powder XRD patterns of 3α and 3β Figure S15. Simulate powder diffraction patterns of a) 3α and b) 3β. PXRD patterns of a) 3α and b) 3β. PXRD patterns of a) 3α ground and b) 3β ground. - S23 -

24 13. TGA and NMR spectroscopy of 3α, 3β, and 3γ Figure S16. TGA profiles of (a) 3α, (b) 3β, and (c) 3γ at a heating rate of 10 C min 1. - S24 -

25 Figure S17. (a) 1 H NMR spectra of 3α, 3β and 3γ in CDCl 3 and (b) the corresponding enlarged spectra. - S25 -

26 14. Crystal structure of 3γ Figure S18. Photographs of 3γ recorded under illumination with daylight (left) and UV light (right) and single-crystal structure of 3γ. - S26 -

27 Figure S19. Emission spectra of 3α ground, 3β ground, and 3γ normalized with the emission intensity of their λ em,max (excitation wavelength: 365 nm). - S27 -

28 15. IR spectroscopy for 3 and other previously reported related complexes (7A 7D) Figure S20. a) IR spectra ( cm 1 ) for 3α, 3β, 3α ground, and 3β ground. b) Corresponding magnifications for the area cm 1. The IR spectra of 3α and 3β show that their C N stretching vibration shifts to lower wavenumbers upon grinding (3α: 2200 cm 1, 3α ground : 2193 cm 1 ; 3β: 2197 cm 1, 3β ground : 2193 cm 1 ). According to previous reports, 16 we suggest that the observed shift of the C N stretching vibration for 3α and 3β should be attributed to the formation of aurophilic interactions. This notion was experimentally supported in this study in the form of IR absorption studies on the four structurally related gold isocyanide complexes 7A 7D, which have been reported previously F 3 C Au C N CN Au C N 7A 7B O MeO Au C 7C N Au C N 7D 7A 7D can form two different structurally-solved polymorphs, i.e., 7 Au-Off and 7 Au-On. While the former exhibits no aurophilic interaction, the latter does. The IR spectra of these polymorphs are shown in Figure S21 S24. For 7A 7D, only the polymorph with aurophilic interactions (7 Au-On ) shows C N absorption at lower wavenumbers. According to the IR studies on 7A 7D, the observed shift of the C N stretching absorption to lower wavenumbers upon grinding of 3α and 3β (Figure S20) indicates that the resulting amorphous 3α ground and 3β ground exhibit aurophilic interactions. - S28 -

29 Figure S21. Single-crystal structures of a) 7A Au-Off and b) 7A Au-On. 17 c) IR spectra of 7A Au-Off and 7A Au-On. - S29 -

30 Figure S22. Single-crystal structures of a) 7B Au-Off and b) 7B Au-On. 18 c) IR spectra of 7B Au-Off and 7B Au-On. - S30 -

31 Figure S23. Single-crystal structures of a) 7C Au-Off and b) 7C Au-On. 19 c) IR spectra of 7C Au-Off and 7C Au-On. - S31 -

32 Figure S24. Single-crystal structures of a) 7D Au-Off and b) 7D Au-On. 20 c) IR spectra of 7D Au-Off and 7D Au-On. - S32 -

33 Figure S25. a) IR spectrum ( cm 1 ) for 3γ. b) Magnifications of the IR spectra of 3α, 3β, 3α ground, 3β ground, and 3γ for area cm 1. Red star indicates an unassignable peak. - S33 -

34 16. Polymorph 3δ i) Preparation of 3δ The single crystal of 3δ can be obtained by the crystallization condition similar to that of 3β. However, 3δ is always formed concomitantly with other polymorphs, i.e., 3α and 3β. The powder form of 3δ is obtained by reprecipitation: typically, a solution of 3 (100 mg) in 1 ml of dichloromethane is added portion-wise to its poor solvent methanol (20 ml) at 78 C. Precipitates was rapidly filtered and dried under reduced pressure to give 3δ as yellow powder. ii) Photographs of 3δ Figure S26. Photographs of the single crystal and the powder of 3δ taken under room light. iii) DSC measurement of 3δ Figure S27. DSC traces of 3δ at a heating/cooling rate of 10 C min 1. - S34 -

35 iv) Single-crystal X-ray diffraction analyses of 3δ Table S4. Summary of X-ray crystallographic data for 3δ Polymorph 3δ CCDC Name CCDC Empirical Formula C 21 H 14 AuN Formula Weight Crystal System orthorhombic Crystal Size / mm a / Å (2) b / Å (4) c / Å (5) α / 90 β / 90 γ / 90 V / Å (2) Space Group Pbca (#61) Z value 16 Dcalc / g cm Temperature / K max / 54.9 (MoK ) / cm No. of Reflections Measured Residuals: R 1 (I > 2.00 (I)) / % Residuals: wr 2 (All reflections) / % Total: Unique : 7488 (R int = ) Goodness of Fit (GOF) Maximum peak in 2.29 e Final Diff. Map / Å 3 Minimum peak in 1.58 e Final Diff. Map / Å 3 - S35 -

36 v) TGA and NMR spectroscopy of 3δ Figure S28. TGA profile of 3δ at a heating rate of 10 C min 1. Figure S29. a) 1 H NMR spectrum of 3δ in CDCl 3 and b) the corresponding enlarged spectrum. - S36 -

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