Supporting Information

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1 Copyright WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, Supporting Information for Adv. Funct. Mater., DOI: /adfm Remarkable Turn-On and Color-Tuned Piezochromic Luminescence: Mechanically Switching Intramolecular Charge Transfer in Molecular Crystals Qingkai Qi, Jingyu Qian, Xiao Tan, Jibo Zhang, Lijuan Wang, Bin Xu,* Bo Zou, and Wenjing Tian*

2 Copyright WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, Supporting Information Remarkable Turn-on and Color-Tuned Piezochromic Luminescence: Mechanically Switching Intramolecular Charge Transfer in Molecular Crystals Qingkai Qi, Jingyu Qian, Xiao Tan, Jibo Zhang, Lijuan Wang, Bin Xu,* Bo Zou and Wenjing Tian* Table of Contents 1. General Information 2. Synthetic route to AD-TPE 3. PL spectra of AD-TPE in THF-H 2 O mixtures of with different water fractions 4. TEM image and DLS measurement of AD-TPE aggregates formed in 90% aqueous mixture 5. Summary of quantum yield and fluorescent lifetime of AD-TPE in the solid state before and after grinding 6. Summary of crystal data and intensity collection parameters of AD-TPE 7. PXRD pattern of the pristine powder sample and the simulated PXRD pattern delineated on the basis of the crystal structure 8. The unit cell structure of AD-TPE crystal 9. ORTEP drawings and selected dihedral angles (deg) in the single crystal 10. Dipole moment µ in the single crystal 11. PL spectra of AD-TPE in the solution, powder and PMMA film 12. Formation of H-aggregates by dipole-dipole interactions and supermolecular interactions 13. Molecular packing modes optimized by DFT calculations at GGA-PBE level under different external stress 14. PL spectra of AD-TPE in different solvents with increasing polarity 15. The ground-state frontier orbitals contribution of AD-TPE in gas state and crystal calculated at B3LYP/6-31G(d, p) ** level 16. Summary of the oscillator strengths of AD-TPE in gas state calculated using B3LYP/6-31G(d, p) ** by Gaussian UV absorption and fluorescence spectra of AD, TPE and AD-TPE in THF solution 18. UV-vis absorption spectra of the pristine and ground powders of AD-TPE performed by diffuse reflectance mode

3 19. PL spectra and CIE1931 coordinates for the ground sample 20. Lifetimes of AD-TPE in the powders before and after grinding HNMR, 13 CNMR and MS spectra of AD-TPE 22. References

4 1. General Information 1 H NMR spectra were recorded on a 500 MHz BrukerAvance in CDCl 3 solutions, using CDCl 3 as solvent and tetramethylsilane (TMS) as an internal standard (δ = 0.00 ppm). 13 C NMR spectra were recorded on a 125 MHz BrukerAvance, using CDCl 3 as a solvent and an internal standard (δ = ppm). The GC/MS were recorded on a Thermo Fisher ITQ1100. The time of flight mass spectra was recorded using a Kratos MALDI-TOF mass system. UV-Vis spectra were measured on a Shimadzu UV-2550 spectrophotometer. Fluorescence spectra were recorded by Shimadzu RF-5301 PC spectrometer and Maya2000Pro optical fiber spectrophotometer. Crystalline state PL efficiencies were measured using an integrating sphere (C-701, Labsphere Inc.), with a 405 nm Ocean Optics LLS-LED as the excitation source, and the light was introduced into the integrating sphere through optical fiber. The powder X-ray diffraction patterns were recorded by Rigaku SmartLab X-ray diffractometer with Cu Kα radiation (λ = Å) at 25 o C (scan range: 4-45 o ). DSC experiments were recorded on a NETZSCH DSC 204 instrument at a scanning rate of 10 K min -1. The morphologies of the nanoaggregates of AD-TPE were investigated using a JEM-2100F TEM at an accelerating voltage of 200 kv. Fluorescence Lifetime and Steady State Spectroscopy were performed using time-correlated single-photon counting (TCSPC) method and collected on an Edinburgh FLS980, with an Edinburgh EPL-375 picosecond pulsed diode laser as the excitation source. DLS measurement was performed using a Malvern ZetasizerNano ZS size analyser at room temperature. High-pressure experiments were carried out using Sapphire-anvil cell. The culet diameter of the sapphire anvils was 0.6mm. Copper gasket was preindented to a thickness of 0.17mm, and center hole of 0.24mm was drilled for the single crystal. A small ruby chip was inserted into the sample compartment for in situ pressure calibration according to the R1 ruby fluorescence method. Silicone oil was used as a pressure-transmitting medium (PTM). The hydrostatic pressure on the single crystal was determined by monitoring the widths and separation of the R1 and R2 lines. The

5 photoluminescence measurements under high pressure were performed on a QuantaMaster 40 spectrometer in the reflection mode. The 380 nm line of a xenon lamp with a power of 60 W was used as the excitation source. The in situ UV-vis absorption measurements under high pressure are performed on an Ocean Optics QE65000 Scientific-grade spectrometer. The images of the single crystal under visible light and 380 nm UV light were taken by putting the Sapphire-anvil cell (SAC) containing the sample on a Nikon fluorescence microscope. All experiments were conducted at room temperature. The sketch of the experimental setup is shown below: Single-Crystal Structure: A single crystal suitable for X-ray structural analysis was obtained by slow evaporation from the chloroform/ethanol solution at room temperature. Single crystal X-ray diffraction intensity data were collected on a Rigaku RAXIS-PRID diffractometer using the ω-scan mode with graphite-monochromator Mo Kα radiation. The structure was solved with direct methods using the SHELXTL programs and refined with full-matrix least squares on F 2. The corresponding CCDC reference number (CCDC: ) and the data can be obtained free of charge from The Cambridge Crystallographic Data Centre via

6 2. Synthetic route to AD-TPE Scheme S1. Synthetic route to AD-TPE Preparation of Materials: Tetrahydrofuran (THF), toluene and ethanol were distilled in the presence of sodium benzophenoneketyl, calcium hydride and magnesium respectively, then, stored under nitrogen immediately prior to use. Dimethylformamide (DMF) was distilled and dried over potassium hydroxide. 1-(4-bromophenyl)-1,2,2-triphenylethene was synthesized according to previous literatures. [1 2] All the other chemicals were purchased from Aladdin and used as received without further purification. 1-(4-Bromophenyl)-1,2,2-triphenylethene. 1 H NMR (500 MHz, CDCl 3 ), δ (TMS, ppm): 7.22 (d, J = 8.5 Hz, 2H), (m, 9H), (m, 6H), 6.90 (d, J = 8.5 Hz, 2H). MS (EI): Calcd for C 26 H 19 Br: , Found: Synthesis of AD-TPE: The synthetic routes were shown in Scheme S1. To a 50 ml dry, three-necked round flask were charged 1-(4-bromophenyl)-1,2,2-triphenylethene (1, 0.82 g, 2 mmol), 9(10H) acridone (0.39 g, 2 mmol), K 2 CO 3 (0.34 g, 2.5 mmol), CuI (0.034 g), 2,2,6,6-tetramethyl-3,5-heptanedione (76 ul), and anhydrous DMF (10 ml). The mixture was degassed and refluxed at 152 under nitrogen atmosphere for 24 h. After cooling to room temperature, the precipitates from the reaction mixture

7 were collected by filtration, washed with 3 M HCl, water and methanol, and dried in air. The crude product was dissolved in CH 2 Cl 2 and purified by column chromatography (silica gel, ethyl acetate/petroleum ether =1/6, v/v, R f = 0.4) to give a white solid (0.89 g, 85%). 1 H NMR (500 MHz, CDCl 3 ) δ (ppm): 8.57 (d, J = 7.9 Hz, 2H), (m, 2H), 7.36 (d, J = 8.2 Hz, 2H), (m, 2H), (m, 17H), 6.72 (d, J = 8.6 Hz, 2H). 13 C NMR (75 MHz, CDCl 3 ) δ (ppm): , , , , , , , , , , , , , , , , , , , , , MS (MALDI-TOF): m/z (M+H, calcd ). 3. PL spectra of AD-TPE in THF-H 2 O mixtures of with different water fractions. Figure S1. PL spectra of AD-TPE in THF-H 2 O mixtures with different water fractions (f w ). Solution concentration: M. Insets: fluorescence images under (365 nm) UV light. 4. TEM image and DLS measurement of AD-TPE aggregates formed in 90% aqueous mixture

8 Figure S2. a) TEM image and b) DLS measurement of AD-TPE aggregates formed in 90% aqueous mixture. Inset of a): corresponding ED pattern. 5. Summary of quantum yield and fluorescent lifetime of AD-TPE in the solid state before and after grinding Table S1. Summary of quantum yield and fluorescent lifetime of AD-TPE before and after grinding. Sample Φ F (%) <τ> (ns) K r (s -1 ) K nr (s -1 ) Pristine crystal Ground sample Abbreviations: Φ F : fluorescence quantum yield determined using a calibrated integrating sphere, average lifetime: <τ> = (A 1 τ 1 2 +A 2 τ 2 2 )/(A 1 τ 1 +A 2 τ 2 ). Radiative transition rate constant: K r = Φ F /<τ>. Non-radiative transition rate constant: K nr = (1 Φ F )/<τ>. 6. Summary of crystal data and intensity collection parameters of AD-TPE Table S2. Summary of crystal data and intensity collection parameters of AD-TPE AD-TPE Empirical formula C 39 H 27 NO Formula weight Crystal dimensions, mm 0.35 x 0.18 x 0.10 Crystal system Triclinic Space group P-1 a, Å 9.551(5) b, Å 9.643(7) c, Å (9)

9 α, deg 78.35(2) β, deg (18) γ, deg 86.45(2) V, Å (15) Z 2 D calcd., g/cm F Temp, (K) 153(2) Μ(Mo Kα), mm θ range, deg No. of collected reflns No. of unique reflns R(int) Data/restraints/parameters 4914/0/370 R 1, wr 2 [obs I> 2σ (I)] , R 1, wr 2 (all data) , Residual peak/hole e. Å / Goodness-of-fit on F CCDC number PXRD pattern of the pristine powder sample and the simulated PXRD pattern delineated on the basis of the crystal structure Figure S3.PXRD pattern of the pristine powder sample and the simulated PXRD pattern delineated on the basis of the crystal structure using the single crystal software Mercury

10 8. The unit cell structure of AD-TPE crystal Figure S4. The unit cell structure of AD-TPE crystal. 9. ORTEP drawings and selected dihedral angles (deg) in the single crystal Figure S5. ORTEP drawings (50% probability ellipsoids) and the selected dihedral angles (deg) in the AD-TPE single crystal. 10. Dipole moment µ in the single crystal

11 Figure S6. Dipole moment µ in the single crystal. 11. PL spectra of AD-TPE in the solution, powder and PMMA film Figure S7. PL spectra of AD-TPE in solution, powder and PMMA film. 12. Formation of H-aggregates by dipole-dipole interactions and supermolecular interactions

12 Figure S8. Formation of H-aggregates by dipole-dipole interactions and supermolecular interactions. 13. Molecular packing modes optimized by DFT calculations at GGA-PBE level under different external stress The single crystal DFT calculations under different hydrostatic pressure were performed by using the CASTEP module in Material Studio [3-5]. The generalized gradient approximation (GGA) with Perdew Burke Ernzerhof (PBE) [6] was used to describe the exchange-correlation (XC) effects. TS scheme was used for dispersion corrections. This calculation was done with plane wave set using Norm-conserving pseudopotentials [7] with 750 ev energy cut off. For geometry optimization, the energy tolerance was ev per atom with the force tolerance of 0.05 ev/å, a maximum displacement of Å, and a maximum stress tolerance of 0.10 GPa. For self-consistent field (SCF) calculation, the energy tolerance was set to ev per atom. According to the structure data of single-crystal diffraction, the initial packing geometry was fully relaxed under external stress of 0.0, 1.0, 2.0 and 3.0 GPa. In the absence of external stress, the optimized structure is in good agreement with that obtained by single-crystal analysis. Table S3. Optimized lattice parameters under external stress of 0, 1, 2 and 3 GPa Stress/GPa a/å b/å c/å α/ o β/ o γ/ o V/Å 3 Exp. Data

13 Table S4. The distances between the molecule planes of AD-TPE in the two H-aggregates, the center distances between AD units, the pitch angles and roll angles of the dimers under external stress of 0, 1, 2 and 3 GPa Stress/GPa d 1 /Å d 2 /Å d 3 /Å d 4 /Å χ 1 /deg χ 2 /deg χ 3 /deg χ 4 /deg Exp. Data GPa GPa GPa GPa Table S5. Dihedral angel (Deg) θ of AD-TPE in optimized unit cell under external stress of 0, 1, 2 and 3 GPa Stress/GPa θ (Deg) Exp. Data PL spectra of AD-TPE in different solvents with increasing polarity Figure S9. PL spectra of AD-TPE in different solvents with increasing polarity.

14 15. The ground-state frontier orbitals contribution of AD-TPE in gas state and crystal calculated at B3LYP/6-31G(d, p)** level. Figure S10. The theoretical calculated ground-state frontier orbitals contribution of AD-TPE in a) gas state and b) crystal using B3LYP/6-31G(d, p)** by Gaussian Summary of the oscillator strengths of AD-TPE in gas state calculated using B3LYP/6-31G(d, p)** by Gaussian 09. Table S6. Summary of the oscillator strengths of AD-TPE in gas state calculated using B3LYP/6-31G(d, p)** by Gaussian 09 Compounds States Abs(nm) f Main Contribution AD-TPE S HOMO LUMO(97%) S HOMO-1 LUMO(53%) HOMO LUMO+1(45%)

15 17. UV absorption and fluorescence spectra of AD, TPE and AD-TPE in THF solution Figure S11. UV absorption and fluorescence spectra of AD, TPE and AD-TPE in THF solution. 18. UV-vis absorption spectra of the pristine and ground powders of AD-TPE performed by diffuse reflectance mode Figure S12. UV-vis absorption spectra of the pristine and ground powders of AD-TPE performed by diffuse reflectance mode. 19. PL spectra and CIE1931 coordinates for the ground sample

16 Figure S13. PL spectra and CIE1931 coordinates for the ground sample. A worthy feature is that, when we applied the mechanical force to AD-TPE molecular crystal, a bright and broad fluorescence with dual emission band can be observed. Such dual and broad emission from the piezochromic luminescence is known to be difficult to be achieved in the case of one molecule through controlling the molecular stacking mode. However, as shown in Figure S13, the emission under the mechanical stimuli turns into cyan with the Commission International de l Eclairage (CIE) coordinates of (0.20, 0.31). Compared with the initial emission with the CIE coordinates of (0.17, 0.11), the mechanical stimuli lead to a tendency for the white light emission which is attracted interest for materials and devices because of their great potential for various applications. 20. Lifetimes of AD-TPE in the powders before and after grinding Figure S14. Lifetimes of the AD-TPE powders measured at different emission peak before and after grinding.

17 21. 1 H NMR, 13 C NMR and MS spectra of AD-TPE Figure S15. 1 H NMR spectrum of AD-TPE in CDCl 3. Figure S C NMR spectrum of AD-TPE in CDCl 3.

18 Figure S17. MS (MALDI-TOF) spectrum of AD-TPE. 22. References: [1] M. Banerjee, S. J. Emond, S. V. Lindeman, R. Rathore, J. Org. Chem. 2007, 72, [2] R. Hu, J. L. Maldonado, M. Rodriguez, C. Deng, C. K. W. Jim, J. W. Y. Lam, M. M. F. Yuen, G. Ramos-Ortiz, B. Z. Tang, J. Mater. Chem. 2011, 22, 232. [3] Delley, B. J. Chem. Phys. 1990, 92, 508. [4] Delley, B. J. Chem. Phys. 2000, 113, [5] Delley, B. J. Chem. Phys. 1991, 94, [6] Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, [7] Bachelet, G. B.; Hamann, D. R.; Schluter, M. Phys. Rev. B, 1982, 26, 4199.