Radiation Stability of Cations in Ionic Liquids. 1. Alkyl and Benzyl Derivatives of 5-Membered Ring Heterocycles.

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1 2013 American Chemical Society, Shkrob et al. jp Page 1 SUPPLEMENTARY MATERIAL Radiation Stability of Cations in Ionic Liquids. 1. Alkyl and Benzyl Derivatives of 5-Membered Ring Heterocycles. Ilya A. Shkrob* 1, Timothy W. Marin, 1,2 Huimin Luo, 3 and Sheng Dai 4 1 Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL Chemistry Department, Benedictine University, 5700 College Road, Lisle, IL Energy and Transportation Science Division, Oak Ridge National Laboratory, Oak Ridge, TN Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN Abbreviations in the text. Alk Bz BzPy + BR + alkyl benzyl 1-benzylpyridinium general representation for organic cation, where B is the base and R is the arm at the heteroatom electrospray ionization tandem mass spectrometry 1 H- 1 H correlation spectroscopy (two dimensional NMR spectroscopy) bis(2-ethylhexyl) phosphate anion dimethylsulfoxide electron paramagnetic resonance liquid chromatography mass spectrometry nuclear magnetic resonance bistriflimide anion saccharinate anion ESI MS/MS COSY DEHP - DMSO EPR LCMS NMR - NTf 2 Sac - RMeIm + 1-R-3-methylimidazolium cation, see Scheme 1 RMeT R-3-methyl-1,3,4-triazolium cation, see Scheme 1 RMeTh + 1-R-5-methyl-thiazolium cation, see Scheme 1 Ph phenyl PyBz 1-benzylpyridinium Tf CF 3 SO 2 (triflyl) group TMS tetramethylsilane U 5-atom ring heterocycle base (imidazole, 1,2,4-triazole, or 4- methylthiazole)

2 2013 American Chemical Society, Shkrob et al. jp Page 2 List of chemical reactions. (A - ) ** A + e - (1) C + + e - C (2) (C + ) ** C 2+ + e - (3) C 2+ A - C(-H) + + H δ+ A δ- (4) C + H δ+ A δ- CH + + A - (5) A + A - A - 2, (6) C + C + C + 2, (7) {BR + }** BH + + R(-H) (8) {BR }* B + R (9) B + H δ+ A δ- BH + A - (10) {BR + }* B + R + (11) B + R + BR + (12) A - + e - A 2- (13) A 2- + H δ+ A δ- AH - + A - (14)

3 2013 American Chemical Society, Shkrob et al. jp Page 3 List of analyses, by irradiated compound (in this study) cation anion form b EPR, K MS LCMS 1 H NMR 13 C NMR 19 F NMR Bz-h 7 -MeIm Cl l x Bz-h 7 -MeIm DEHP l x Bz-h 7 -MeIm NTf 2 l x x x Bz-h 7 -MeIm Sac l x x x Bz-d 7 -MeIm Sac l x x x Bz-h 7 -MeIm d PF 6 s x x x x x x BuMeIm d PF 6 s x x x x x x BzT134Im d PF 6 s x x x x x x EtT134Im d PF 6 s x x x x x x BuT134Im d PF 6 s x x x x x x BzThIm d PF 6 s x x x x x x BuThIm d PF 6 s x x x x x x a) studied previously. b) solid (s) or liquid (l) at 300 K c) and other isotopomers (other than pulse radiolysis) d) bistriflimide compounds of these cations are known room temperature liquids.

4 2013 American Chemical Society, Shkrob et al. jp Page 4 1S. Synthetic procedures. In a typical synthesis of BzMeIm Cl, 20 mmol of 1-methylimidazole and 20 mmol of benzyl chloride (-h 7 or -d 7 ) were dissolved in 20 ml of acetonitrile and refluxed for 12 h while being vigorously stirred using a magnetic bar. The acetonitrile solvent was removed in vacuum at 80 o C, and the resulting chlorides were dissolved in water for metathesis. These aqueous solutions were treated with activated carbon before the reaction. The yield is 99+% by 1 H NMR. Unless specified otherwise, RMeU + compounds were obtained by combining aqueous solutions of alkali salts of the desired anion and RMeU Cl, with the anion present in 1:1.2 mol/mol stoichiometric excess. The aqueous solution was vortexed for 5 min, and then stirred using a magnetic bar for another 30 min. For crystalline RMeU + compounds (see melting points in Table 1S), the reaction mixture was left to sit for 1-2 h at 5 o C. The crystals were filtered out at reduced pressure, washed with cold water, and then dried in vacuum. Additional purification involved recrystallization from methanol, acetonitrile, or methanol-water mixtures. All compounds were pure by 1 H and 13 C NMR (e.g., Figures 1S and 2S, Tables 2S, and Scheme 2S) and ESI-MS (e.g., Table 3S). The anions were introduced as 0.3 M solutions of Li NTf 2 and KPF 6 and 0.8 M Na Sac. The procedure for synthesis of ILs was similar. If oil condensed from the aqueous solution during the metathesis, it was separated by centrifugation, repeatedly washed with water, and dried in a vacuum oven at o C over 5-12 h. Otherwise, the IL was extracted from the solution by methylene chloride, the organic layer was washed with water, the organic solvent was removed in vacuum, and the resulting oil was dried in a vacuum oven. To obtain saccharinates (Scheme 1), aqueous solutions of the corresponding chlorides and Na Sac were combined. The reaction mixture was stirred for 30 min and reduced to dryness in vacuum at 80 o C. Methylene chloride was added and the suspension was stirred for 2 h at room temperature. The residue was filtered out using a Whatman paper filter followed by 0.5 μm micropore Teflon filter. Methylene chloride was removed in vacuum and the resulting oil was dried in a vacuum oven. The bis(2-ethylhexyl)phosphate (DEHP, Scheme 1) anion was introduced as follows: neat HDEHP acid was stirred with an equivalent of potassium hydroxide in an aqueous suspension for 15 min and the ph was adjusted to a neutral reaction. The BzMeIm Cl was added, and the mixture was stirred for 30 min. An equal volume of methylene chloride was added to this aqueous suspension, the mixture was vortexed, and then stirred for another hour. The organic layer was separated and the aqueous layer was extracted 3x with methylene chloride. The combined organic layers were washed 3x with pure water, separated, and reduced in vacuum. A small amount of methylene chloride was added and this organic phase was washed 3x more with pure water and then the organic layer was separated by centrifugation at 3,000 rpm. The organic solvent was removed and the resulting oil was dried in a vacuum oven.

5 2013 American Chemical Society, Shkrob et al. jp Page 5 All of these ionic compounds were 1 H NMR and chromatographically pure and liquids contained < 300 ppm of water by titration.

6 2013 American Chemical Society, Shkrob et al. jp Page 6 Scheme 1S. Reactions of Reduced and Electronically Excited Cations. + e - exc. X + e - exc. X aliphatic arm benzyl arms? X Y N R X Y N R H X Y N H R X Y N X Y N H X Y N X Y N N Y X Z Z Z Z Ph Z Ph Z Z R Z e - exc. X + e - exc. X aliphatic arm benzyl arms? X Y N R X Y N R H X Y N H R X Y N X Y N H X Y N X Y N N Y X Z Z Z Z Ph Z Ph Z Z R Z

7 2013 American Chemical Society, Shkrob et al. jp Page 7 Scheme 2S. Calculated carbon-13 shifts for derivatives of MeU (to the left) and MeU (to the right), where U is T134 or Th Optimized gas-phase geometry, B3LYP/6-31+G(d,p)), in ppm vs. TMS. Experimental data from Table 2S are indicated in italics N N S N N N N H S N + + H N N N S N N N N S N N

8 2013 American Chemical Society, Shkrob et al. jp Page 8 Table 1S. Melting points (m. p.) for crystalline RMeU PF 6 compounds. R U m.p., o C Et Bu T Bz 115 Bu Th Bz

9 2013 American Chemical Society, Shkrob et al. jp Page 9 Table 2S. Experimentally determined proton and carbon-13 chemical shifts for 5-atom ring cations in dilute solution of hexafluorophosphate salts for listed cations in DMSO-d 6. δ( 1 H) vs. TMS, ppm cation ring ring ring Ph Me α β γ δ BuMeIm no TMS BzMeIm Bz-d 7 -MeIm EtMeT BuMeT BzMeT BuMeTh = BzMeTh , cation ring ring ring δ( 13 C) vs. TMS, ppm a ring (Ph) ring (Ph) Me α β γ δ BuMeIm BzMeIm , EtMeT BuMeT BzMeT , BuMeTh BzMeTh , a) for resonance line attributions, see Scheme 2S.

10 2013 American Chemical Society, Shkrob et al. jp Page 10 Table 3S. Mass peaks a) for selected 1-benzyl-x 7-3-methylimidazolium (x=h,d) compounds. isotopo -mer anion MS + 1, a.m.u. MS 1, a.m.u. (CA) n C + (CA) n A - h 7 Cl PF [0], [1], 625.1, 796 [3], 1006 [4], 1218 [5] [0], [1], NTf [0], [1], 1086 [2] [0], [1], BF [3], 1212 [4], 1472 [5], [6], 1992 [7] Sac [0], 527.8, 627.7, [2] [2], 660 [3], 730, 869 [4], 1079 [5], 1284 [6], 1494 [7], 1703 [8], 1913 [9] 313.1, [1], 598, [2], [3], [4], 1735 [5] [0], 583, 598, [1], [2] 280, 607 [1], 661, 673, 721 d [0], 280.2, 598.8, 734.6, [2] DEHP [0], [1] [0], [1], [2] PF [0], 191, 274.4, 313, 448, 594, 598, [1], [2] NTf [0], [1] [0], 582.9, [1] Sac [0], [1], [0], 280.2, 598.8, 634.8, [2] a) [n] indicates x in (CA) n C + and (CA) n A - series of cluster ions, the m/z is highlighted in bold face.

11 2013 American Chemical Society, Shkrob et al. jp Page 11 Table 4S Symmetry, representation, electronic energy and X-H bond dissociation energy for various ground state species derived from RMeU+ cations with methyl and ethyl arms (optimized gas-phase geometry, B3LYP/6-31+G(d,p) calculation). MeMeIm + type sym. repr. el. energy Hartree D(X-H) ev cation C + C 2v A e - adduct C C s A' dimer radical + C 2 C 2 A cation C 2h A g H 2 CH + C 2v B H 4,5 C 1 A H l@ N 1,3 (α) C(-H) + C s A" EtMeIm + type sym. repr. el. energy Hartree D(X- H) ev cation C + C 1 A e - adduct C C 1 A dimer radical + C 2 C 2 A cation H 2 CH + C s A" (α) C(-H) + C s A" (β) C s A'

12 2013 American Chemical Society, Shkrob et al. jp Page 12 Continued. D(X- MeMeT134 + type sym. repr. el. energy H) Fig. Hartree ev 3S cation C + C s A' e - adduct C C 1 A i dimer radical + C 2 cation C 2 A ii H 2 C s A" iii H 4 CH + C 1 A iv H 5 C s A" v - N 1 C(-H) + C s A" vi - C 6 C s A" vii EtMeT134 + type sym. repr. el. energy D(X-H) Fig. Hartree ev 4S cation C + C 1 A e - adduct C C 1 A i dimer radical + C 2 cation C 2 A ii H 2 CH + C 1 A iii H 5 C 1 A iv - N 1 (α) C 1 A v - C 6 C 1 A vii - N 1 (β) C(-H) + C 1 A vi

13 2013 American Chemical Society, Shkrob et al. jp Page 13 Continued. MeMeTh + type sym. repr. el. energy Hartree D(X-H) ev Fig. 5S cation C + C s A' e - adduct C C i dimer radical cation (C 2 -C 2 ) C 2 A ii + dimer radical C 2 cation (S 3 -S 3 ) C 2 A H 2 C s A" iii H 3 CH + C 1 A iv H 4 C s A" v H 5 C 1 A vi - N 1 C(-H) + C s A" vii - C 6 C s A" viii EtMeTh + type sym. repr. el. energy Hartree D(X-H) ev Fig. 6S cation C + C 1 A e - adduct C C 1 A i dimer radical + C 2 cation C 2 A ii H 2 CH + C 1 A iii H 4 C 1 A iv - N 1 (α) C 1 A v - N 1 (β) C(-H) + C 1 A vi - C 6 C 1 A vii

14 2013 American Chemical Society, Shkrob et al. jp Page 14 Table 5S. Cartesian coordinates, isotropic hfcc s, anisotropic hfc tensors, and Euler angles for these tensors (α(x),β(y),γ(z) convention) for magnetic nuclei in radicals derived from RMeU + cations with 1-methyl and 1-ethyl arms (optimized gas-phase geometry, B3LYP/6-31+G(d,p) calculation) MeMeIm + e- adduct X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H α X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 C(13) N(14) N(14) C(13) H C(13) C(13) C(13) H H H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 C(13) N(14) N(14) C(13)

15 2013 American Chemical Society, Shkrob et al. jp Page 15 5 C(13) C(13) C(13) H H H H H H H H H H dimer radical cation, C 2 symmetry X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H

16 2013 American Chemical Society, Shkrob et al. jp Page 16 Continued. EtMeIm + e- adduct X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H C(13) H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H H H α X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) C(13)

17 2013 American Chemical Society, Shkrob et al. jp Page 17 4 C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H β X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H dimer radical cation, C 2 symmetry X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H C(13) H H H H

18 2013 American Chemical Society, Shkrob et al. jp Page H N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H C(13) H H H H H H H H H H H

19 2013 American Chemical Society, Shkrob et al. jp Page 19 Continued. MeMeT134 + e- adduct X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) H H H H H H H H dimer radical cation, C 2 symmetry X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) N(14) C(13) C(13) C(13) C(13) N(14) N(14) C(13) C(13) C(13) C(13) H H H H H H H H H H H H H H H

20 2013 American Chemical Society, Shkrob et al. jp Page H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) H H H H H H H H H H α X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) H H H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) H H H H H H H

21 2013 American Chemical Society, Shkrob et al. jp Page 21 Continued. EtMeT134 + e- adduct X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H α X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H β X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13)

22 2013 American Chemical Society, Shkrob et al. jp Page 22 6 C(13) C(13) C(13) H H H H H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H

23 2013 American Chemical Society, Shkrob et al. jp Page 23 H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H dimer radical cation, C 2 symmetry X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 N(14) N(14) N(14) N(14) C(13) C(13) C(13) C(13) N(14) N(14) C(13) C(13) C(13) C(13) H H H H C(13) C(13) H H H H H H H H H

24 2013 American Chemical Society, Shkrob et al. jp Page H H H H H H H

25 2013 American Chemical Society, Shkrob et al. jp Page 25 Continued. MeMeTh + e- adduct X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H

26 2013 American Chemical Society, Shkrob et al. jp Page H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H dimer radical cation, C 2 symmetry X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) S(33) N(14) N(14) C(13) C(13) C(13) C(13) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H H H H H H

27 2013 American Chemical Society, Shkrob et al. jp Page 27 Continued. EtMeTh + e- adduct X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H α X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13)

28 2013 American Chemical Society, Shkrob et al. jp Page 28 8 C(13) H H H H H H H H H H β X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H H

29 2013 American Chemical Society, Shkrob et al. jp Page 29 X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) N(14) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H H H H H H dimer radical cation, C 2 symmetry X, Å y, Å z, Å a iao, G B aa, G B bb, G B cc, G α, O β, O γ, O 1 S(33) S(33) N(14) N(14) C(13) C(13) C(13) C(13) C(13) C(13) C(13) C(13) C(13) C(13) H H H H H H C(13) C(13) H H H H H H H H

30 2013 American Chemical Society, Shkrob et al. jp Page H H H H H H

31 2013 American Chemical Society, Shkrob et al. jp Page 31 Table 6S. Summary of (absolute) isotropic hfcc s (Gauss) for 1 H and 14 N nuclei in radicals of specified cations with aliphatic arms. a) base R N (1) 1 H (α,1) 1 H (β,1) 1 H (2) e- adduct, C 1 Me Et Me Et Me Et dimer radical cation, C 2 symmetry, C 2 1 Me Et Me Et Me Et H 2, CH + 1 Me Et Me Et 3 Me Et H loss radical, C(-H) + N1 Me N1, α Et N1 Me N1, α Et N1 Me N1, α Et N1, β Et ? N1, β Et N1, β Et C6 Me C6 Et C6 Me C6 Et N (3) a) the site of loss/addition is indicated sign. Me (3) 14 N (4) 1 H (4) 1 H (5) Me (6)

32 2013 American Chemical Society, Shkrob et al. jp Page 32 Table 7S. Isotropic hfcc's (Gauss) for BzMeIm + derived radicals with C s symmetry in two lowest-energy "propeller" conformations a and b (see the scheme below). The radicals are enumerated as shown in the scheme below. ΔE el indicates electronic energy (E el ) with regard to the lowest energy conformer. BLYP/6-31+G(d,p) method. species -E el, Hartree ΔE el me V 14 N 1 1 H 2 1 N 3 1a b a b a b a b H 4 1 H 5 1 H 6 1 H 1' 2 1 H 3' 2 1 H 4' 1 H 5' 6 1' 2 3 H 1 N 2' + N 5' 4 5 H 1 3' 4' a b N + N N N N N + H N N N + N N + N 4 5

33 2013 American Chemical Society, Shkrob et al. jp Page 33 Table 8S. Mass-spectroscopy (ESI MS 1 + ) analysis of irradiated RMeU PF 6 compounds (R=Et, Bu, and Bz). a) BuMeIm PF 6, 2.77 MGy m/z, a.m.u. attribution 3 METHYLIMIDAZOLIUM CATIONS weight % MS 2 fragments, a.m.u. remainder, a.m.u C C Me C F C Et MeIm C Pr Bu C Bu , , C Bu Me , , C Bu Et C Me MeIm? C PF4? MeIm C C , , C C Me C C Et C C Pr C MeIm PF4? MeIm C C Bu 1.2 BzMeIm PF 6, 3.66 MGy m/z, a.m.u. attribution weight % MS 2 fragments, a.m.u. remainder, a.m.u. LCMS retention time, min LCMS retention time, min C , C Me C F MeIm C MeIm C Bz MeIm C Bz Me? C Bz MeIm , C Bz Bz MeIm Bz d 7 MeIm PF 6, 2.68 MGy C H/D shift

34 2013 American Chemical Society, Shkrob et al. jp Page C Me C F , , , C MeIm MeIm C Bz C Bz Me? MeIm C Bz MeIm , , C Bz Bz MeIm 19

35 2013 American Chemical Society, Shkrob et al. jp Page 35 Continued. EtMeT134 PF 6, 1.85 MGy m/z, a.m.u. attribution 3 METYL 1,3,4 TRIAZOLIUM CATIONS weight % MS 2 fragments, a.m.u. remainder, a.m.u Me loss EtMeT134 (C ) 100 HMeT134 C 2 H C Me 0.95 MeMeT134 C 2 H C F C Bu C Bu Me C T134 F C C , 138, 194 MeT C T134 T , 237 T134, C MeT134 T , 221 HMeT C C MeT HMeT134 BuMeT134 PF 6, 1.83 MGy m/z, a.m.u. weight % MS 2 fragments, a.m.u. remainder, a.m.u. LCMS retention time, min LCMS retention time, min attribution EtMeT PrMeT HMeT134 C 3 H BuMeT134 (C ) 100 HMeT134 C 4 H , HMeT134, C F , 113, 138 HF C Et C Pr C Bu Me Pr C Me MeT T C Bu Bu C Bu T HMeT C C 3 236, 140, 196 MeT C C Me 0.8

36 2013 American Chemical Society, Shkrob et al. jp Page 36 Continued. BzMeT134 PF 6, 2.32 MGy m/z, a.m.u. attribution weight % MS 2 fragments, a.m.u. remainder, a.m.u. LCMS retention time, min Bz Pr 0.38 Bz C 3 H Bz Bu 0.74 Bz C 4 H Ph2CH 0.33 Bz BzMeT134 (C ) 100 Bz MeT ? Ph2CMe Me C Me MeT C F Bz2 Bu 0.8 Bz ? 243 Ph3C MeT C MeT MeT , C Bz MeT C Bz Me MeT C Bz F , 241 MeT134, ? C Bz Bu? MeT ? MeT C Bz MeT , 304 MeT134, , C Bz Bz MeT

37 2013 American Chemical Society, Shkrob et al. jp Page 37 Continued. BuMeTh PF 6, 2.20 MGy m/z, a.m.u. attribution 5 METHYLTHIAZOLIUM CATIONS weight % MS 2 fragments, a.m.u. remainder, a.m.u. LCMS retention time, min BuMeTh Bu C F Bu C Bu Bu 4.10, C BuTh MeTh C C , C C Me? 1.1 BzMeTh PF6, 4.15 MGy m/z, a.m.u. attribution weight % MS 2 fragments, a.m.u. remainder, a.m.u. LCMS retention time, min Ph2CMe Me BzMeTh (C ) C F MeTh C Me F Ph3C C Th MeTh C Bz MeTh C MeTh MeTh 4.14, C BzTh? C Bz Bz? C C MeTh 4.13, 4.59, , , a) The columns give product mass peak (positive mode MS 1 ), peak attribution (where possible), the most prominent MS 2 neutral fragment upon collisional dissociation, the remainder after the dissociation, and retention time for the corresponding peak in the chromatogram.

38 2013 American Chemical Society, Shkrob et al. jp Page 38

39 2013 American Chemical Society, Shkrob et al. jp Page 39 Table 9S. Summary of 19 F and 31 P resonances in proton coupled and decoupled NMR spectra of irradiated RMeU PF 6 compounds (in DMSO-d 6, vs. CFCl 3 for fluorine-19 and vs. H 3 PO 3 for phosphorus-31), where R=Et, Bu, or Bz. X stands for a spin-1/2 nucleus other than proton; J is indirect dipole-dipole coupling constants (J-couplings). BuMeIm PF 6 J ( 19 F- 1 H), Hz δ( 19 F), ppm coupling pattern J( 19 F-X), Hz δ( 31 P), ppm coupling pattern dd 54.2, dd 46.6, dd 46.8, dd 50.1, dd 50.7, dd 52.2, , 57.4, tdd dd 55.3, dd 42.9, dd 57, dd 57.2, dd 42.7, dd 55.7, dd 58.3, dd 55.1, d m(7) - PF td 55.5, td 55.1, td 57.2, td 56.8, d t - PF 2 O t s s s s s s m(8)? s s s s s attributio n

40 2013 American Chemical Society, Shkrob et al. jp Page s broad s s d? s s BzMeIm PF 6 J ( 19 F- 1 H), Hz δ( 19 F), ppm coupling pattern J( 19 F-X), Hz δ( 31 P), ppm coupling pattern dd 48.1, dd 52.2, dd 51.4, dd 56.6, dd 56.8, dd 58.1, dd 41.2, dd 57, d d m(7) - PF d m(5)d 57.9, d t - PF 2 O dt 6.2, m? m? d broad s attributio n

41 2013 American Chemical Society, Shkrob et al. jp Page 41 Continued. EtMeT134 PF 6 δ( 19 F), ppm coupling pattern J( 19 F-X), Hz δ( 31 P), ppm coupling pattern attributio n dd 740.4, dd 776.8, dd 777.2, ddt 760.6, 56.1, d dd 826.9, dd 745.6, dd 739.7, dd 767.5, dd 764.7, s d m(7) - PF dt 887.8, dt 750.8, (qt) d t - PF 2 O s s broad s s

42 2013 American Chemical Society, Shkrob et al. jp Page 42 Continued. BuMeT134 PF 6 δ( 19 F), ppm coupling pattern J( 19 F-X), Hz δ( 31 P), ppm coupling pattern attributio n dd 737.1, dd 777, dd 780.5, ddt 765.3, 57.9, s??? s d ? dd 764.9, s d m(7) - PF s d t - PF 2 O s s s m s s s - BF s - BF s s broad s s s s s d - FPO 3

43 2013 American Chemical Society, Shkrob et al. jp Page 43 Continued. BzMeT134 PF 6 δ( 19 F), ppm coupling pattern J( 19 F-X), Hz J( 19 F- 1 H), Hz δ( 31 P), ppm coupling pattern attributio n dd 56.8, qd 50.7, dd 59.2, dd 57.4, s s d m(7) - PF s s s m(5)d 56.1, d t - PF 2 O m(5)d 60.5, d d d s td 9.5, tt 5.4, td 6.8, s s d s s

44 2013 American Chemical Society, Shkrob et al. jp Page 44 Continued. BuMeTh PF 6 δ( 19 F), ppm coupling pattern J( 19 F-X), Hz δ( 31 P), ppm coupling pattern attributio n d dd 783.1, dd 790.9, d d m(7) - PF d d - FPO d t - PF 2 O s s s d s s s s s s s s s s s d

45 2013 American Chemical Society, Shkrob et al. jp Page 45 Continued. BzMeTh PF6 δ( 19 F), ppm coupling pattern J( 19 F-X), Hz J( 19 F- 1 H), Hz δ( 31 P), ppm coupling pattern attributio n d dd 45.3, dd 52, d dd 55.3, s tdd 13.9, 53.5, d d d dd 55.3, dd 57, d m(7) - PF d d - FPO d t - PF 2 O s dt 6.1, m td 6.2, s broad s s

46 2013 American Chemical Society, Shkrob et al. jp Page 46 Captions for Figures 1S to 33S. Figure 1S. 1 H NMR spectra for (i) BzMeIm Sac, (ii) Bz -d 7 -MeIm Sac, (iii) BzMeIm DEHP, and (iv) BzMeIm PF 6. Figure 2S. 1 H NMR spectra for 1-methylimidazole, BzMeIm Cl, BzMeIm NTf 2 and, and Bz-d 7 - MeIm NTf 2. Figure 3S. Views of geometry optimized structures for gas phase radicals derived from MeMeT134 + : (i) electron adduct, (ii) C 2 symmetrical dimer radical cation, (iii-v) H atom adducts at C 2, N 4, and C 5 atoms, respectively, and H loss radicals centered at (vi) C α and (vii) C 6 atoms. Figure 4S. Views of geometry optimized structures for gas phase radicals derived from EtMeT134 + : (i) electron adduct, (ii) C 2 symmetrical dimer radical cation, H atom adducts at (iii) C 2 and (iv) C 5 atoms, and H loss radicals centered at (vi) C α, (vi) C β, and (vii) C 6 atoms. Figure 5S. Views of geometry optimized structures for gas phase radicals derived from MeMeTh + : (i) electron adduct, (ii) C 2 symmetrical dimer radical cation, (iii-vi) H atom adducts at C 2, S 3, C 4, and C 5 atoms, respectively, and H loss radicals centered at (vii) C α and (viii) C 6 atoms. Figure 6S. Views of geometry optimized structures for gas phase radicals derived from EtMeTh + : (i) electron adduct, (ii) C 2 symmetrical dimer radical cation, H atom adducts at (iii) C 2 and (iv) C 4 atoms, and H loss radicals centered at (v) C 6, (vi) C α, and (vii) C β atoms. Figure 7S. Simulated first-derivative EPR spectra for C radicals (solid lines) and C 2 symmetrical C 2 + dimer radical cations (dashed lines) derived from RMeU + cations (R=Me and Et, color coded as shown in the inset in the plot) shown in Scheme 1. See Tables 5S and 6S for hfcc tensors. Figure 8S. Simulated first-derivative EPR spectra for various C(-H) + radicals. Panel a: at carbon-6 in MeMeT134 + and MeMeTh + (solid line) and EtMeTh + (dashed line). Panel b: for C α and C β centered radicals in the long arms of the EtMeU + cations (U=Im, T134, and Th). Figure 9S.

47 2013 American Chemical Society, Shkrob et al. jp Page 47 Simulated first-derivative EPR spectra for various CH + radicals. Panel a: at carbon-2 in MeMeU + (U=Im, T134, and Th). Panel b: at carbon-2 (solid lines) and carbon-4 or nitrogen-4 for EtMeU +. Figure 10S. Simulated first-derivative EPR spectra for various radicals derived from Bz-x 7 -MeIm + (x=h and D). "Propeller" configurations a and b in Table 7S are indicated by solid and dashed lines, respectively. See the insets for further disambiguation. Figure 11S. First-derivative EPR spectra of irradiated frozen BzMeIm NTf 2 obtained at 50 K, using a microwave power of 0.02 mw (a) and 2 mw (b). Panel a compares the spectra observed for BzMeIm-h 7 NTf 2 and BzMeIm-d 7 NTf 2 isotopomers (solid and dashed lines, respectively). The structure seen in this EPR spectrum is from the benzyl radical (see Figure 1 in the text). Panel b demonstrates a wide sweep EPR spectrum revealing the resonance lines from CF 3 and CF 2 SO 2 NTf - radicals. See the insets for further disambiguation. Figure 12S. First-derivative EPR spectra of (a) Bz-h 7 -MeIm NTf 2 and (b) Bz-d 7 -MeIm NTf 2 obtained during programmed warming (50 K to 150 K) of samples that were irradiated at 77 K (0.02 mw). The features indicated by the two arrows in panel b originate from M( 1 H 2 )=±1/2 lines of the D atom adduct (CD + ) of the parent cation at carbon-2 that is shown in the inset. Figure 13S. First-derivative EPR spectra of irradiated frozen BzMeIm BF 4 containing a protic (presumably, hydronium) impurity (50 K). The features indicated by the two arrows are from the M(2 1 H 2,2 )=±1 lines of the CH + radical. Figure 14S. First-derivative EPR spectra of irradiated frozen EtMeT134 PF 6 (0.02 mw). The progression below shows the transformations of the EPR spectra as the sample is warmed from 50 K to 175 K. In the upper plots, the solid red and dashed black lines (trace i) are EPR spectra obtained at 50 K before and after warming of the sample to 175 K. The difference trace reveals the resonance lines of the C radical. Figure 15S. Like Figure 14S, for BuMeT134 PF 6. Figure 16S. First-derivative EPR spectra of irradiated frozen BuMeTh PF 6 (0.02 mw) obtained as the sample was warmed from 50 K to 200 K. The features indicated by the open circles are attributed to H α loss radicals, and the features indicated by the arrows are the outer resonance lines for the interior C(-H) + radicals. See Figure 8S. Figure 17S.

48 2013 American Chemical Society, Shkrob et al. jp Page 48 First-derivative EPR spectra of irradiated frozen BzMeT134 PF 6 (0.02 mw) obtained as the sample was warmed from 50 K to 200 K. The features indicated by the arrows are attributed to CH + radicals. The upper two traces compare the normalized EPR spectra obtained at 50 K before (solid trace) and after (dashed trace i) warming of the sample to 200 K. It is seen that that the unresolved singlet line originates from the benzyl radical that poorly rotates in the low temperature matrix. Figure 18S. Like Figure 17S, for irradiated BzMeTh PF 6. The arrows indicate the weak outer resonance lines of the H atom adduct. The upper traces have been obtained at 50 K, before (solid line) and after warming of the sample to 200 K (trace i) and 300 K (trace ii). Figure 19S. 1 H NMR spectrum of BzMeIm PF 6 before (i) and after (ii) radiolysis (in DMSO-d 6 ). The chemical shifts δ( 1 H) are given in ppm vs. TMS. Hereafter, the irradiation doses are indicated in Table 8S. The arrows indicate 13 C satellites. Group-A indicates the group of resonance lines for coupled protons as determined using 1 H- 1 H COSY spectroscopy. The clipped lines belong to the parent cation. Figure 20S. 13 C NMR spectrum of irradiated BzMeIm PF 6. Notice the logarithmic vertical scale. The green labels indicate the resonance lines of the parent cation attributed following DFT calculations in Scheme 2S. The red circles indicate the resonances of the highest yield product. The arrow indicates the resonance of the methylene carbon attached to the methyl rings. Figure 21S. Like Figure 19S, for BzMeT134 PF 6. There are several groups of the coupled protons color labeled from A to F, as shown in the inset. Figure 22S. Like Figure 20S, for BzMeT134 PF 6. Figure 23S. Like Figure 19S, for BzMeTh PF 6. The green labels indicate the coupling patterns. Figure 24S. Like Figure 20S, for BzMeTh PF 6. Figure 25S and 26S. Like Figure 19S, for BuMeIm PF 6. The green labels indicate the coupling patterns and J- couplings. Figure 27S. Like Figure 20S, for BuMeIm PF 6. Figure 28S. Like Figure 19S, for EtMeT134 PF 6. The green labels indicate the coupling patterns.

49 2013 American Chemical Society, Shkrob et al. jp Page 49 Figure 29S. Like Figure 20S, for EtMeT134 PF 6. Figure 30S. Like Figure 19S, for BuMeT134 PF 6. The green labels indicate the coupling patterns. Figure 31S. Like Figure 20S, for BuMeT134 PF 6. Figure 32S. Like Figure 19S, for BuMeTh PF 6. The green labels indicate the coupling patterns. Figure 33S. Like Figure 20S, for BuMeTh PF 6.

50 δ

51 δ

52 α α

53 β α α β

54 α α

55 β α α β

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57 α β αβ

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68 δ

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74 α β γ δ δ

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