Electrospun nylon 6 nanofibers incorporated with 2-substituted N-alkylimidazoles and their
silver(I) complexes for antibacterial applications
Phumelele Kleyi, Carminita L. Frost, Zenixole R. Tshentu, Nelson Torto*
Supplementary Information
1.1 Synthesis of N-alkylimidazoles
Imidazole (0.088 mol) was dissolved in 50 mL acetone and powdered KOH (0.10 mol) was
added and the mixture allowed to stir for 2 h. Thereafter, alkylbromide (0.090 mol) was
added dropwise and the solution stirred overnight. The white precipitate was removed by
filtration and the filtrate evaporated. The resulting brown oil was distilled under vacuum
(158°C, 4.7x10-2 mbar) to afford clear oil.
1.1.1 Synthesis of N-alkylimidazole-2-carboxaldehydes
To a suspension of 1-alkylimidazole (0.020 mol) in dry diethyl ether (50 mL) was added 2.5
M butyllithium (0.021 mol) at -78C (dry ice/acetone slurry). After stirring for 1 h, DMF
(0.030 mol) was added and the resulting solution was stirred overnight. After completion of
the reaction, water (2 mL) was added followed by 15 mL of 4 N HCl. The aqueous layer was
made basic by the addition of potassium carbonate, subsequently; the product was extracted
into chloroform. The organic layer was concentrated and the product was distilled at 3.0x10-1
mbar and 80°C to yield a brownish crystalline solid after cooling.
N-Octylimidazole-2-carboxaldehyde (octImCHO)
Yield 53.3%. Brown oil. 1H NMR (400MHz, CDCl3) δ 0.90 (3H, t, J 8.0, N(CH2)7CH3), 1.30
(10H, m, N CH2CH2(CH2)5), 1.79 (2H, m, NCH2CH2), 4.40 (2H, t, J 8.0, NCH2) 7.16, 7.29
(2H, s, Im-H), 9.83 (1H, s, CHO); 13C NMR (400 MHz, CDCl3) δ 14.39, 22.96, 26.78, 29.41,
29.45, 48.19, 126.55, 131.91, 143.82, 182.39. IR (cm-1, KBr disk): 1687, ν(C=O). Anal.
Calcd (found) for C12H20N2O: C, 69.19 (69.12); H, 9.68 (9.87); N, 13.45 (13.25).
N-Decylimidazole-2-carboxaldehyde (decImCHO)
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Yield 54.2%. Brown oil. 1H NMR (400MHz, CDCl3) δ 0.85 (3H, t, J 8.0, N(CH2)9CH3), 1.24
(14H, m, NCH2CH2(CH2)7), 1.76 (2H, m, NCH2CH2), 4.46 (2H, t, J 8.0, NCH2) 7.14, 7.25
(2H, s, Im-H), 9.78 (1H, s, CHO); 13C NMR (400 MHz, CDCl3) δ 14.50, 23.05, 26.78, 29.48,
29.65, 29.86, 31.42, 32.24, 48.22, 126.67, 131.90, 143.71, 182.38. IR (cm-1, KBr disk) 1687,
ν(C=O). Anal. Calcd (found) for C14H24N2O: C, 71.14 (71.24); H, 10.23 (10.26); N, 11.85
(11.90).
1.1.2 Synthesis of 2-hydroxymethyl-N-alkylimidazoles
To a stirred solution of the 1-alkylimidazole-2-aldehyde (3.4 mmol) in methanol (10 mL) at
0°C was added NaBH4 (3.4 mmol). After stirring at 0°C for 2.5 h the solution was
concentrated. The residue was taken up in Et2O and extracted three times with H2O. The
ethereal solution was dried with Na2SO4, filtered and Et2O removed in vacuo to obtain a pure
product.
2-Hydroxymethyl-N-octylimidazole.2H2O (ocImCH2OH)
Yield 68.6%. Clear oil. 1H NMR (400MHz, CDCl3) δ 0.88 (3H, t, J 8.0, N(CH2)7CH3), 1.29
(10H, m, NCH2CH2(CH2)5), 1.78 (2H, m, NCH2CH2), 3.99 (2H, t, J 8.0, NCH2), 4.62 (2H, s,
CH2OH), 6.85, 6.82 (2H, s, Im-H);
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C NMR (400 MHz, CDCl3) δ 14.17, 22.74, 26.83,
29.26, 29.29, 31.88, 46.29, 55.74, 119.95, 126.77, 147.97. IR (cm-1, KBr disk) 3602 ν(O-H);
1638 ν(C=N); 1494 ν(C=N-C=N). Anal. Calcd (found) for C12H26N2O3: C, 58.51 (58.55); H,
10.64 (10.63); N, 11.37 (11.59).
2-Hydroxymethyl-N-decylimidazole (decImCH2OH)
Yield 79.2%. Clear oil. 1H NMR (400MHz, CDCl3) δ 0.88 (3H, t, J 8.0, N(CH2)9CH3), 1.22
(14H, m, NCH2CH2(CH2)7), 1.78 (2H, m, NCH2CH2), 3.99 (2H, t, J 8.0, NCH2), 4.63 (2H, s,
CH2OH), 6.83, 6.86 (2H, s, Im-H);
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C NMR (400 MHz, CDCl3) δ 14.30, 22.86, 26.86,
29.37, 29.46, 29.66, 46.32, 55.17, 120.05, 126.80, 147.88. IR (cm-1, KBr disk) 3636 ν(O-H);
1637 ν(C=N); 1494 ν(C=N-C=N). Anal. Calcd (found) for C14H26N2O: C, 70.54 (69.96); H,
10.99 (10.43); N, 11.75 (11.48).
1.1.3 Synthesis of N-alkylimidazole-2-carboxylic acids
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1-Alkylimidazole-2-aldehyde (0.003 mol) was dissolved in water (1 mL). To the solution was
added 30% H2O2 (1 mL). The solution mixture was allowed to stir overnight, followed by the
removal of water using a high vacuum pump to produce a pure white crystalline product.
N-Octylimidazole-2-carboxylic acid.H2O (octImCOOH )
Yield 99.9%. White fatty solid, m.p. <40°C, 1H NMR (400MHz, D2O) δ 0.85 (3H, t, J 8.0,
N(CH2)7CH3), 1.25 (10H, m, NCH2CH2(CH2)5), 1.82 (2H, m, NCH2CH2), 4.60 (2H, t, J
8.0,NCH2), 7.18, 7.49 (2H, s, Im-H), 8.29 (1H, s, COOH); 13C NMR (400 MHz, D2O) δ
14.39, 22.95, 26.78, 29.43, 29.45, 31.13, 32.10, 49.77, 119.93, 123.36, 140.23, 157.59. IR
(cm-1, KBr disk) 3140 ν(OH); 1639 ν(C=O); 1508 ν(C=C); 1464 ν(C=N-C=N). Anal. Calcd
(found) for C12H22N2O3: C, 59.48 (59.71); H, 9.15 (9.51); N, 11.56 (11.51).
N-Decylimidazole-2-carboxylic acid.H2O (decImCOOH)
Yield 99.9%. White paste. 1H NMR (400MHz, CDCl3) δ 0.88 (3H, t, J 8.0, N(CH2)9CH3),
1.25-1.33 (14H, m, NCH2CH2(CH2)7), 1.88 (2H, m, NCH2CH2), 4.71 (2H, t, J 8.0, NCH2),
7.06, 7.41 (2H, s, Im-H), 9.34 (1H, s, COOH); 13C NMR (400 MHz, CDCl3) δ 14.26, 22.83,
26.55, 29.27, 29.58, 29.79, 29.85, 31.07, 32.01, 49.44, 119.37, 122.23, 141.07, 156.05. IR
(cm-1, KBr disk) 3137 ν(OH); 1672 ν(C=O); 1508 ν(C=C); 1464 ν(C=N-C=N). Anal. Calcd
(found) for C14H26N2O3: C, 62.19 (62.15); H, 9.69 (9.64); N, 10.36 (10.33).
1.2 Synthesis of silver(I) complexes containing 2-hydroxymethyl-N-alkylimidazoles
To a solution of AgNO3 (1 mol equivalent) in ethanol (15 ml) was added 2-hydroxymethylN-alkylimidazole (2 mol equivalents). The reaction mixture was stirred at room temperature
for 24 h. The reaction mixture was filtered, ethyl acetate (15 ml) was added to the mother
liquor and the solvent evaporated slowly at atmospheric pressure to obtain a pure product in
good yield.
[Ag2(2-hydroxymethyl-N-octylimidazole)4](NO3)2 (Ag-octImCH2OH)
Yield 89.3%. Colourless oil. Anal. Calc. (found) for C48H88Ag2N10O10 (%): C, 48.82 48.32);
H, 7.51 (6.88); N, 11.86 (11.73). IR (cm-1) 3485, 3123, 2925, 2855, 1520, 1454, 1331, 1287,
1237, 1113, 1091, 1030, 948, 819, 738, 655.
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[Ag2(2-hydroxymethyl-N-decylimidazole)4](NO3)2 (Ag-decImCH2OH)
Yield 84.4%. Grey needle-like solid. M.p. 75-77°C. Anal.
Calc. (found) for
C56H104Ag2N10O10 (%): C, 52.01 (52.19); H, 8.11 (7.85); N, 10.83 (10.51). IR (cm-1) 3384,
3122, 2919, 2851, 1498, 1466, 1351, 1318, 1284, 1153, 1115, 1039, 975, 827, 772, 743, 689,
657.
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