Supplementary Information for

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1 Supplementary Information for Elucidating the Solvent Effect on the Switch of the Helicity of Poly(quinoxaline-2,3-diyl)s: A Conformational Analysis by Small-Angle Neutron Scattering Yuuya Nagata, *1 Tsuyoshi Nishikawa, 1 Michinori Suginome, *1 Sota Sato, 2,3 Masaaki Sugiyama, *4 Lionel Porcar, 5 Anne Martel, 5 Rintaro Inoue, 4 and Nobuhiro Sato 4 1. Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto , Japan 2. JST, ERATO Isobe Degenerate π-integration Project and Advanced Institute for Materials Research, Tohoku University, Aoba-ku, Sendai, Miyagi Department of Chemistry, The University of Tokyo, Bunkyo-ku, Hongo, Tokyo, Research Reactor Institute, Kyoto University, Osaka , Japan 5. Institut Laue-Langevin, 6, rue Jules Horowitz, Grenoble 38042, France nagata@sbchem.kyoto-u.ac.jp, suginome@sbchem.kyoto-u.ac.jp, and sugiyama@rri.kyoto-u.ac.jp S1

2 1. General UV-vis absorption spectra were recorded on JASCO V-770 spectrometers equipped with a JASCO type ETC-505T temperature/stirring controller at 20 C. Circular dichroism (CD) spectra were recorded on a JASCO J-1500 spectrometer equipped with a JASCO type PTC-510L temperature/stirring controller at 20 C. Poly((R,R)-5,8-dimethyl-6,7- di(2octyloxymethyl)quinoxaline-2,3-diyl) 100mer (2oct) was prepared according to our previous report. 1 Tetrahydrofuran-d8 (THF-d8) and 1,1,2-trichloroethane-d3 (1,1,2-TCEd3) were purchased from the commercial sources and were used without further purification. 2. UV-vis absorption and CD spectra of 2oct As preliminary experiments, UV-vis absorption and CD spectra of 2oct were measured in mixed solvents of 1,1,2-trichloroethane (1,1,2-TCE) and tetrahydrofuran (THF) with various ratio (Figures S1 and S2). When pure 1,1,2-TCE was used as the solvent (1,1,2- TCE/THF = 10/0), broad UV absorption peaks and a distorted CD spectrum were observed due to low solubility of 2oct in 1,1,2-TCE. In pure THF and the mixed solvent of 1,1,2-TCE/THF (8/2, i.e., 4/1), 2oct showed good solubility and typical UV-vis absorption and CD spectra of single-handed poly(quinoxaline-2,3-diyl)s. The gabs values (Kuhn s dissymmetry factor, Δε/ε) of 2oct in THF or 1,1,2-TCE/THF (4/1) were determined as or , respectively. According to our previous report, 1 these values suggested that 2oct adopted almost pure right-handed helical conformation in THF, while the main chain was inverted to almost pure left-handed helical conformation in 1,1,2-TCE/THF (4/1). S2

3 Figure S1 UV-vis absorption spectra of 2oct in mixed solvents of 1,1,2-TCE and THF with various ratio. ( g/l, 20 C, light path length = 10 mm) Figure S2 CD spectra of 2oct in mixed solvents of 1,1,2-TCE and THF with various ratio. ( g/l, 20 C, light path length = 10 mm) S3

4 3. Theoretical calculations Conformational analyses and geometry optimizations with molecular mechanics (MM) calculations were carried using the Forcite module of Materials Studio 8.0 with the COMPASS II force field at ultra-fine quality (the displacement of the standard enthalpy of formation (SEF) was less than 10-5 ). 2 The solvent excluded surfaces (SES) of (P)-δ1-2oct and (M)-λ4-2oct with 2.0 Å of the probe sphere radius were calculated using the Maximal Speed Molecular Surface (MSMS) program. 3 The calculated surfaces were colored from blue to red according to the distance from the main chain axis (radius) using the CueMol program. 4 Figure S3 Anti-comformers of (R,R)-5,8-dimethyl-6,7-di(2- octyloxymethyl)quinoxaline with dihedral angles, and ψ. Table S1 Dihedral angles ( and ψ) and standard enthalpy of formation (SEF) of δ1 5 and λ1 5. Relative SEF to δ-1 Conformer (deg) ψ (deg) SEF (MM, kj/mol) (MM, kj/mol) δ δ δ δ δ λ λ λ λ λ S4

5 Table S2 SEF of (P)-δ1 5, (P)-λ1 5, (M)-δ1 5, and (M)-λ-1 5. SEF values estimated by single-point semi-empirical calculations using MOPAC with the PM6 Hamiltonian were also presented. Conformer SEF SEF (MM, kj/mol) (PM6, single point, kj/mol) (P)-δ1-2oct (P)-δ2-2oct (P)-δ3-2oct (P)-δ4-2oct (P)-δ5-2oct (P)-λ1-2oct (P)-λ2-2oct (P)-λ3-2oct (P)-λ4-2oct (P)-λ5-2oct (M)-δ1-2oct (M)-δ2-2oct (M)-δ3-2oct (M)-δ4-2oct (M)-δ5-2oct (M)-λ1-2oct (M)-λ2-2oct (M)-λ3-2oct (M)-λ4-2oct (M)-λ5-2oct S5

6 Figure S4 SES of (P)-2oct. The surfaces were colored according to the distance from the main chain axis (radius). Figure S5 SES of (M)-2oct. The surfaces were colored according to the distance from the main chain axis (radius). S6

7 4. SANS experiments SANS experiments were performed using the D22 SANS spectrometer installed at the Institut Laue-Langevin (ILL), Grenoble, France. The high-flux and high-quality neutron beam on the D22 was important to obtain accurate SANS patterns of the polymer solutions. To characterize the whole size, shape and local structure of the polymer, a wide q-range from to 0.8 Å 1 was measured using a combination of three optical settings: 6.0 Å neutron and sample-to-detector distance (SDD) of 17.6 m, 4.6 Å neutron and SDD of 8.0 m, and 4.6 Å neutron and SDD of 1.5 m. The observed SANS intensity was corrected for background, empty cell and buffer scatterings, and transmission factors and put into an absolute scale using the direct beam measurement. All the data reduction was performed using GRASansP software. 6 2oct was dissolved in THF-d8 or 1,1,2-TCEd3/THF-d8 (4/1), whose concentrations are set to 4.0 mg/ml. The temperature was maintained at 313 K during the measurements. 5. SANS analysis SANS intensity, ID(q), of randomly oriented molecules in vacuum is given the following Debye formula, I D (q) = [ b j ] 2 sin (q r jk ) + 2 b j b k j J>k r jk, where bj and rjk are scattering length of j-th atom and distance between j-th and k-th atoms, respectively. Because the polymer was dissolved in the solvent, the solvent effect on the scattering intensity should be considered, i.e., it is essential to determine the volume and shape of the domain where the polymer excludes the solvent for the calculation of the SANS intensity in solution. The zero-angle scattering intensity, I(0), in absolute unit (cm -1 ), is given as the following formula I(0) = N(b all V ex ρ solvent ) 2 S7

8 , where N, ball, Vex, and ρsolvent are the number density of molecule, the total scattering length of molecule, the volume excluded by polymer and the scattering length density of solvent, respectively. Here, I(0) can be experimentally obtain through a Guinier analysis for the scattering profile in the low-q region, and N, ball, and ρsolvent can be calculated with the densities and the constitutions of the polymer and the solvent. These variables were determined as follows. For 2oct in THF-d8: I(0) = cm -1, N = cm -3, ball = cm, ρsolvent = cm -2, and Vex = cm 3 ; for 2oct in 1,1,2- TCE-d3/THF-d8 (4/1): I(0) = cm -1, N = cm -3, ball = cm, ρsolvent = cm -2, and Vex = cm 3. Next, space including the structural model of 2oct was discretized into an array of cubic cells. It should be noted here that the size of the cell plays an important role to precisely reproduce the size and the shape of the polymer in solution. The size of the cell was set to be Å 3 (20.12 Å 3 ) for every structural model, which was determined to be consistent with Vex. The scattering intensity of 2oct in solution was calculated using the Debye formula by exchanging atomic scattering length with the cell contrast. The contrast of the j-th cell, Cj, is given as, C j = b k ρ solvent v cell k,where bk is the scattering length of k-th atom in the cell and vcell is the cell volume. After the calculation with the Debye function, the calculated ID(q) was convoluted with an instrumental function reflecting the error of q, E(q). The simulated scattering intensity IS(q) was as follows, I S (q) = E(q q )I D (q )dq IS(q) was calculated for 10 P-helical conformers in THF-d8 and 10 M-helical conformers in 1,1,2-TCE-d3/THF-d8 (4/1) as shown in Figures S6 and S7. Finally, the residual sum of squares (RSS) between the observed SANS pattern, IO(q), and IS(q), and χ 2 values of RSS were calculated to determine the conformations of 2oct in these solvents. IS(q) of S8

9 (P)-δ1-2oct and (M)-λ4-2oct showed the best agreement with IO(q) of 2oct in THF-d8 and 1,1,2-TCE-d3/THF-d8 (4/1), respectively. Figure S6 SANS and simulated patterns of (P)-2oct. a, Observed SANS patterns of (P)-2oct in THF-d8 and simulated SANS patterns of (P)-δ1-2oct to (P)-δ5-2oct. b, Observed SANS patterns of (P)-2oct in THF-d8 and simulated SANS patterns of (P)-λ1-2oct to (P)-λ5-2oct. χ 2 values of the residual sum of squares between the observed and simulated SANS patterns were also presented. Note that (P)-δ3-2oct and (P)-λ5-2oct with low χ 2 values also have "extended" conformations similar to (P)-δ1-2oct as shown in Fig. S4. Figure S7 SANS and simulated patterns of (M)-2oct. a, Observed SANS patterns of (M)-2oct in 1,1,2-TCE-d3/THF-d8 (8/2) and simulated SANS patterns of (M)-δ1-2oct to (M)-δ5-2oct. b, Observed SANS patterns of (M)-2oct in 1,1,2-TCE-d3/THF-d8 (8/2) and simulated SANS patterns of (M)-λ1-2oct to (M)-λ5-2oct. χ 2 values of the residual sum of squares between the observed and simulated SANS patterns were also presented. S9

10 6. Comparison of SAXS with SANS The SANS and SAXS profiles of (M)-λ4-2oct in 1,1,2-TCE-d3/THF-d8 (4/1) were calculated (Figure S5). The SANS profile showed good agreement with that of SAXS in the lower q-range (q < 0.06 Å -1 ). Both profiles showed the power low of q -1 in the q- ranges from Å -1, corresponding to the cylindrical shape. On the other hand, the SANS and SAXS profiles showed a significant difference in the higher q-range, reflecting their difference in the scattering contrasts of the detailed structure. Especially, the remarkable feature was only observed in the SANS profile that display a distinct peak around q = 0.35 Å -1, which enabled to determine the detailed structure of the chiral side chains as described in the main text. Figure S8 Simulated SANS (blue) and SAXS (red) profiles of (M)-λ4-2oct in 1,1,2- TCE-d3/THF-d8 (4/1). S10

11 7. References (1) Nagata, Y.; Yamada, T.; Adachi, T.; Akai, Y.; Yamamoto, T.; Suginome, M. J. Am. Chem. Soc. 2013, 135, (2) BIOVIA, D. S. Materials Studio 8.0 including Forcite module; Dassault Systèmes BIOVIA: (3) Sanner, M. F.; Olson, A. J.; Spehner, J. C. Biopolymers 1996, 38, (4) Ishitani, K. CueMol: Molecular Visualization Framework; 1.1; Ishitani, K.: (5) Stewart, J. J. P. MOPAC2016; Stewart Computational Chemistry: (6) Dewhurst, D. GRASansP; Dewhurst, D., Institut Laue-Langevin (ILL): S11