Molecules 2020, 25, 2949
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imidazole (97%), 1-chloro-2-methoxyethane (98%), and lithium bis(trifluoromethylsulfonyl)imide (99%)
were purchased from Acros and Sigma-Aldrich (St. Louis, MO, USA).
Imidazole derivatives were dried over solid KOH (1-methylimidazole and 1,2-dimethylimidazole)
or by azeotropic distillation of absolute acetonitrile. All organic solvents used in the synthesis were
previously dried over CaH2 and distilled (see Supplementary Materials).
3.2. Synthesis of ILs with a Symmetrical Linker (1, 2, 4, 5, 10, and 11)
Methods for the synthesis of symmetrical disiloxane dicationic ILs 1, 4, and 10 with a methylene
spacer are described in [19] and with a propylene spacer (ILs 2, 5, and 11) in [18]. The synthesis of
1-(2-methoxyethyl)-2-methylimidazole is described in [19].
10,10,30,30-Tetramethyl-10,30-bis([1,2-dimethylimidazolium-3-yl]methyl)disiloxane bis(trifluoromethylsulfonyl)
1
imide (
1
). The yield of IL 1 was 93%. White solid. H NMR (DMSO-d6, 300.13 MHz)
δ
0.16 (s, 12H),
2.52 s (s, 6H), 3.75 (s 6H), 3.82 (s, 4H), 7.41 (m, 2H), 7.62 (m, 2H). 13C NMR (DMSO-d6, 75.47 MHz)
δ
0.48, 9.74, 35.26, 40.21, 113.05 * (q *, JF = 321.4 Hz), 117.80 *, 121.83, 122.06 *, 122.81, 126.82 *, 143.97.
IRS (ATR) 3184, 3151, 3088, 3049, 2965, 2917, 2853, 1588, 1539, 1515, 1418, 1350,1332, 1326, 1265, 1227,
1176, 1132, 1048, 1035, 841, 823, 792, 763, 740, 714, 693, 664, 655, 613, 599, 580, 569, 508, 469, 435, 406.
Gross formula: C20H32N6O9F12S4Si2, molecular weight 912.92. Calculated, %: C 26.31, H 3.53, N 9.21,
F 24.97, S 14.05, Si 6.15. Found, %: C 26.23, H 3.63, N 9.16, F 24.94, S 13.91, Si 6.26.
10,10,30,30-Tetramethyl-10,30-bis(3-[1,2-dimethylimidazolium-3-yl]propyl)disiloxane bis(trifluoromethylsulfonyl)
1
imide (
2
). The yield of IL 2 was 95%. White solid. H NMR (DMSO-d6, 300.13 MHz)
δ
0.06, (s, 12H),
0.48 (m, 4H), 1.68 (m, 4H), 2.57 (s, 6H), 3.75 (s, 6H), 4.10 (t, J = 7.32 Hz, 4H), 7.62 (m, 4H). 13C NMR
(DMSO-d6, 75.47 MHz) 0.48, 9.53, 14.54, 23.93, 35.05, 50.50, 113.54 * (q *, JF = 321.9 Hz), 117.80 *,
δ
121.21, 122.06 *, 122.75, 126.24 *, 144.61. IRS (ATR) 3186, 3150, 3093, 3053, 2958, 2901, 2810, 1590, 1540,
1467, 1421, 1347, 1330, 1255, 1226, 1176, 1134, 1051, 918, 877, 840, 788, 762, 739, 654, 613, 599, 569, 510,
406. Gross formula: C24H40F12N6O9S4Si2, molecular weight 969.03. Calculated: C 29.75, H 4.16, N 8.67,
F 23.53, S 13.23, Si 5.80. Found: C 29.66, H 4.27, N 8.60, F 23.50, S 13.19, Si 5.87.
10,10,30,30-Tetramethyl-10,30-bis([1-methylimidazolium-3-yl]methyl)disiloxane bis(trifluoromethylsulfonyl)
1
imide (
4
). The yield of IL 4 was 88%. Colorless liquid. H NMR (DMSO-d6, 300.13 MHz)
δ
0.16 (s, 12H),
3.87 (s, 6H), 3.89 (s, 4H), 7.52 (m, 2H), 7.69 (m, 2H), 8.90 (s, 2H). 13C NMR (DMSO-d6, 75.47 MHz) δ −0.96,
36.16, 41.37, 113.52 *(q *, JF = 321.8 Hz), 117.81 *, 122.07 *, 123.54, 124.15, 126.25*, 136.25. IRS (ATR) 3155,
3119, 3100, 2961, 2925, 2853, 1570, 1427, 1347, 1329, 1264, 1226, 1176, 1133, 1050, 1021, 840, 806, 789,
761, 739, 647, 611, 599, 569, 509, 406. Gross formula: C18H28N6O9F12S4Si2, molecular weight 884.87.
Calculated, %: C 24.43, H 3.20, N 9.50, F 25.76, S 14.49, Si 6.35. Found, %: C 24.33, H 3.35, N 9.46,
F 25.73, S 13.51, Si 6.45.
10,10,30,30-Tetramethyl-10,30-bis([1-methylimidazolium-3-yl]propyl)disiloxane bis(trifluoromethylsulfonyl)imide (
5).
1
The yield of IL 5 was 96%. Colorless liquid. H NMR (DMSO-d6, 300.13 MHz)
δ 0.06 (s, 12H), 0.42
(m, 4H), 1.78 (m, 4H), 3.86 (s, 6H), 4.13 (t, J = 7.2, 4H), 7.69 (m, 2H), 7.73 (m, 2H), 9.08 (s, 2H). 13C NMR
(DMSO-d6, 75.47 MHz) δ −0.01, 14.06, 23.79, 35.66, 51.41, 113.08 * (q *, JF = 321.4), 117.34 *, 121.60 *,
122.12, 123.69, 125.87 *, 136.40. IRS (ATR) 3156, 3120, 3102, 2958, 2900, 2808, 1573, 1466, 1431, 1348, 1330,
1256, 1226, 1178, 1133, 1051, 915, 839, 788, 762, 740, 714, 653, 613, 599, 569, 510, 459, 406. Gross formula:
C22H36F12N6O9S4Si2, molecular weight 940.98. Calculated: C 28.08, H 3.86, N 8.93, F 24.23, S 13.63,
Si 5.97. Found: C 27.99, H 3.95, N 8.90, F 24.20, S 13.51, Si 6.07.
10,10,30,30-Tetramethyl-10,30-bis([1-(2-methoxyethyl)-2-methylimidazolium-3-yl]methyl)disiloxane
1
bis(trifluoromethylsulfonyl)imide (10). The yield of IL 10 was 95%. Light yellow liquid. H NMR
(DMSO-d6, 300.13 MHz) δ 0.14 (s, 12H), 2.59 (s, 6H), 3.24 (s, 6H), 3.65 (t, J = 4.9 Hz, 4H), 3.94 (s, 4H),
4.37 (t, J = 5.0 Hz, 4H), 7.61 (m, 2H), 7.75 (m, 2H). 13C NMR (DMSO-d6, 75.47 MHz) δ −0.80, 9.89,
40.23, 48.09, 58.53, 70.39, 113.55 * (q *, JF = 321.9 Hz), 117.81 *, 122.06, 122.08 *, 122.12, 126.34*,
144.04. IRS (ATR) 3182, 3127, 3087, 2959, 2900, 2840, 2821, 1583, 1531, 1436, 1347, 1329, 1258, 1225,