Supporting Information. Efficient light-induced phase transitions in halogen-bonded liquid crystals

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1 Supporting Information Efficient light-induced phase transitions in halogen-bonded liquid crystals Francisco Fernandez-Palacio,, Mikko Poutanen,, Marco Saccone, *, Antti Siiskonen, Giancarlo Terraneo, Giuseppe Resnati, Olli Ikkala, Pierangelo Metrangolo, *,,, and Arri Priimagi *, Laboratory of Nanostructured Fluorinated Materials (NFMLab), Department of Chemistry, Materials, and Chemical Engineering Giulio Natta, Politecnico di Milano, Via L. Mancinelli 7, Milano, Italy. HYBER Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 15100, FI-02150, Espoo, Finland. Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI Tampere, Finland. VTT-Technical Research Centre of Finland, Biologinkuja 7, Espoo, Finland. These authors contributed equally to this work Single-crystal X-ray diffraction Table S1. Crystal data, data collection and structure refinement details for , and Chemical formula C 24 H 29 F 4 IN 2 O C 22 H 25 F 4 IN 2 O C 20 H 21 F 4 IN 2 O C 14 H 13 NO C 14 H 13 NO C 15 H 15 NO Mr Crystal system, space group Triclinic, Triclinic, Monoclinic, P-1 P-1 P2 1 /c Temperature (K) a, b, c (Å) (6), (8), (19) α, β, γ ( ) (4), (4), (4) (2), (6), (5) (12), (12), (14) (3), (4), (19) (2) V (Å 3 ) (2) (15) (2) Z Radiation type Mo Kα Mo Kα Mo Kα µ (mm 1 ) Crystal size (mm) Tmin, Tmax 0.725, , , No. of meas., independ. and obs [I 34300, 10000, , 28821, , 12504, > 2σ(I)] reflections Rint (sin θ/λ)max (Å 1 ) R[F 2 > 2σ(F 2 )], wr(f 2 ), S 0.039, 0.073, , 0.073, , 0.095, 1.16 No. of reflections No. of parameters Δ ρmax, Δ ρmin (e Å 3 ) 0.64, , , 0.72 CCDC number

2 Figure S1. Partial view of crystal packing of XBs and C-H F contacts are shown as black dotted lines. Geometrical parameters are as follows: N3 I1 distance 2.798(1) Å and C-I1 N3 angle ; N6 I2 distance 2.792(1) Å and C-I2 N6 angle F3 H62 distance Å, F6 H9 distance Å and F5 H13B distance Å. Color code: C, gray; O, red; N, blue; F, yellow; I, purple and H, white. Figure S2. Partial view of crystal packing of Arene-perfluoroarene quadrupolar interactions organize the adjacent supramolecular dimers in an anti-parallel arrangement. Centroids of aromatic rings are shown as red circles and centroid centroid distances are as follows: Cent1 Cent Å and Cent3 Cent Å. Color code as Figure S1. Figure S3. Partial view of crystal packing of Arene-perfluoroarene quadrupolar interactions organize the adjacent supramolecular dimers in an anti-parallel arrangement. Centroids of aromatic rings are shown as red circles and centroid centroid distances are as follows: Cent1 Cent Å. Color code as Figure S1.

3 Figure S4. Partial view of crystal packing of The presence of the long alkyl chain in 1-12 system promoted the segregation of the alkyl chains from the aromatic cores, forming distinct separate layers. Space-fill representation. Color code as Figure S1. Figure S5. Partial view of crystal packing of Weak H and H F contacts and distances in Å are reported. Contacts are in black dotted lines. Color code as Figure S1. Figure S6. Partial view of crystal packing of Weak H and H F contacts and distances in Å are reported. Contacts are in black dotted lines. Color code as Figure S1.

4 Figure S7. Partial view of crystal packing of Weak H O (top) and C-H (bottom) contacts and distances in Å are reported. Contacts are in black dotted lines. Color code as Figure S1.

5 Powder X-ray diffraction (PXRD) Figure S8. Powder patterns of simulated from the single crystal structure (red) and as-synthesized from the bulk materials (black). Figure S9. Powder patterns of simulated from the single structure (red) and as-synthesized from the bulk materials (black).

6 Figure S10. Powder patterns of simulated from the single structure (red) and as-synthesized from the bulk materials (black)

7 Optical studies Figure S11. The absorbance measured during the photoinduced nematic-to-isotropic transition of at different illumination conditions. The illumination is started at 0 s and ended after the time indicated in the graph legend. The same absorbance at the onset of the isotropic-to-nematic transition indicates a threshold value. The combined absorbance measurements from different illumination conditions (correlated to phase transitions with birefringence measurements) show that there is a clear onset fraction of the cis-isomer at the isotropic-to-nematic transition. This is seen in Figure S11: at different illumination wavelengths the absorbance value at which the onset of the isotropic-to-nematic transition occurs (seen as a small bump in the curves in the time window s) is constant. In the following, the cis-isomer fraction at the onset is resolved by determining the spectrum of the cis-isomer at the isotropic state and after that the cis-fraction by assuming that the absorbance is the sum of the trans and cisisomers. The spectrum of the cis-isomer in the isotropic state cannot be directly measured or determined by Fischer's method 1 as the thermal isomerization is significant at the transition temperature (110 C) and affects the photostationary states. Note that due to spectral differences between the solution, LC, and isotropic states, the spectra needs to be specifically measured in the isotropic state of the complex. The photostationary states without thermal isomerization are acquired by a method developed by Rau et al, 2 according to whom the spectrum at the photostationary state is described by the following equation: 1 = ε t φ tc + ε c φ ct A PSS A trans (ε c ε t )A t φ tc + k φ tc 1000(ε c ε t )A trans A PSS 1 10 A PSS where A PSS and A trans are the absorbances of the photostationary state and the all-trans-state, ε c and ε t depict the absorption coefficients of the cis- and trans-isomers, φ tc and φ ct are the quantum yields for the trans-to-cis and cis-totrans isomerization, respectively, k is the rate constant of thermal isomerization and I 0 is the irradiation intensity. The primed quantities correspond to the illumination wavelength and the unprimed to an arbitrary analysis wavelength. In the above equation, the first term on the right hand side corresponds to the photostationary state without thermal isomerization, and the second term describes the influence of the thermal isomerization. Based on the equation, the influence of thermal isomerization can be removed by plotting 1/(A PSS A trans ) as a function of X = A PSS /(1 10 A PSS ) 1/I 0. This results in a linear dependence, and the spectra can be extrapolated to infinite intensity, i.e. X = 0, which gives the photostationary state without the influence of thermal isomerization. The measured spectra for different irradiation intensities with 395 nm and 457 nm light, the linear extrapolation and the determined photostationary states are shown in Figure S12 for complex at 120 C. The photostationary states without thermal isomerization are used to determine the spectra of the cis-isomer in the isotropic state by using Fischer s method. 1 Figure S13 shows the normalized spectrum of the trans-isomer and the determined spectrum of the cis-isomer in the isotropic state at 120 C for the complex With this information, and by assuming that the absorbance is the sum of the absorption from trans and cis-isomers, the fraction of cis-isomers can be determined as long as the absorbance of the all-trans state is known. In the measurements shown in Figure S11, due to spectral differences between the isotropic state and the liquid crystalline states, the onset of the isotropic-tonematic transition prevents the direct measurement of the absorbance of the all-trans state. Therefore, the absorbance of 1, I 0

8 the all-trans state needs to be determined by a fitting procedure. This is done by fitting an exponential curve to the thermal cis-to-trans isomerization observed between the ending of the illumination and the onset of the isotropic-tonematic transition. An example of such a fit is shown in Figure S13. From the absorbance value at the onset, and by knowing the spectra for the trans and cis-isomers, the cis-isomer fraction was calculated by assuming absorbance to be the sum of the two isomers: A = f cis A cis + (1 f cis )A trans. The analysis is done for the wavelength range nm, and the error estimate is given based on the deviation inside the wavelength range and from comparison of different repeats of similar transitions. Note that the spectral changes and the scattering prevent the determination of the cis-isomer fraction in the pure liquid crystal phase, and therefore, only the onset concentration of the isotropic-to-nematic transition can be determined. Figure S12. Extrapolation of the photostationary states to infinite intensity. a) and c) show the spectra measured under different illumination intensities with 395 nm and 457 nm wavelength lights, respectively. The spectra are measured for complex at 120 C, where the complex is isotropic. b) and d) illustrate the linearity of the extrapolation to infinite intensity. The calculated photostationary states without the influence of thermal isomerization are plotted in a) and c).

9 Figure S13. a) The spectra of the photostationary states without the influence of thermal isomerization, the spectrum of the trans-isomer and the spectrum of the cis-isomer as determined by the Fischer s method. b) An example of the fitting of an exponential curve to the relaxation data before the onset of the isotropic-to-nematic transition to determine the absorbance of the all-trans state, i.e. after infinite relaxation time. The sample is irradiated with 395 nm light between s and the onset of the isotropic-to-nematic transition is at T = 210 s.

10 Mesophase analysis The phase-transition temperatures and the transition enthalpies for the 1-m 2-n complexes are given in Table S2. When possible, we used solution-grown single crystals for the mesophase analysis. In the cases where single crystals could not be obtained, the complexes were prepared by melting together equimolar amounts of the starting materials. Both preparation methods yielded identical phase transition temperatures, confirming the validity of the approach. The transition temperatures are collected from the DSC data upon heating with a rate of 10 C/min. Table S2. Thermal data for the LC complexes. Complex Transition T [ o C] H[kJ/mol] I-N (110.5) 14 N-SmA (101) 1 SmA-Cr (90.5) Cr-SmA SmA-N N-I Cr-N N-I Cr-N N-I Cr-N N-I Cr-SmA SmA-N N-I Cr-N N-I Cr-N N-I Cr-N N-I Cr-N N-I Cr-SmA SmA-N N-I Cr-N N-I Cr-N N-I Cr-N N-I Cr-N N-I

11 Computational analysis Figure S14. The optimized molecular structure for the complex. Coordinates for complex: C C C C C C H H H H C C H C H C C N C C H H H H O C H H H I C C C C C C F F F F N N C C C C C C

12 H H H H O C H H H References (1) Fischer, E. Calculation of Photostationary States in Systems A B When Only A Is Known. J. Phys. Chem. 1967, 71, (2) Rau, H.; Greiner, G.; Gauglitz, G.; Meier, H. Photochemical Quantum Yields in the A (+hν) B (+hν, Δ) System When Only the Spectrum of A Is Known. J. Phys. Chem. 1990, 94 (17),