General
Melting points were determined using a MEL-TEMP II melting point instrument and were not corrected. Microanalyses were carried out on a Perkin-Elmer 2400 elemental analyzer. 1H-NMR and 13C-NMR spectra were determined with a Lambda JEOL 400 MHz FT-NMR (1H: 400 MHz and 13C: 100.4 MHz) spectrometer. Chemical shifts are given in δ values (ppm) using TMS as the internal standard. The IR spectra were taken with a Perkin-Elmer RX1 FT-IR spectrophotometer.
2-Morpholino-N-(1-(pyridin-2-yl)ethylidene)ethanamine (1): A mixture of 4-(2-aminoethyl)-morpholine (0.65 g, 5 mmol) and 2-acetylpyridine (0.61 g, 5 mmol) in ethanol (50 mL) was refluxed for 2 h followed by addition of few drops of glacial acetic acid. The obtained orange oil was solidified upon standing for 12 h at 55 °C in an oven.
The solid product was recrystallized in methanol. Yield: 61.5%. Molecular formula: C13H19N3O. Analysis Calculated: C, 66.92; H, 8.21; N, 18.01. Found: C, 67.02; H, 8.52; N, 17.99. IR (ATR cm−1) 2972.40 n(C-H), 1690.00, 1642.08 n(C=N), 1588.74, 1568.03 n(C=N)pyr, 1450.89 n(C-C), 1113.20 n(C-N), 1089.21 n(O-C). UV-Vis (DMSO), 281.00 (n→π*); 224.00 (π→π*). 1H-NMR (DMSO-d6), 8.69–7.95 (4H, CH-Ar), 3.79–3.837 (CH2-morph), 2.78–2.58 (NCH2-CH2N), 1.74 (CH3-). 13C-NMR (DMSO-d6). 164.53 [1C, δ(C=N)], 144.45 δ(C), 142.62 δ(CH), 136.40 δ(CH), 123.96 δ(CH), [5C, δ(Ar-pyr)], 61.23 [2C, δ(2CH2)], 52.08, 49.67 [2C, δ(2CH2)], 44.57 [C, δ(CH2)], 31.82 [2C, δ(CH2)], 14.52 [C, δ(CH3)].
2-(Piperazin-1-yl)-N-(1-(pyridin-2-yl)ethylidene)ethanamine (2): A mixture of 4-(2-aminoethyl)-piperazine (0.65 g, 5 mmol) and 2-acetylpyridine (0.61 g, 5 mmol) in ethanol (50 mL) was refluxed for three hours followed by addition of few drops of glacial acetic acid.
The same procedure as for 1 was applied as the prototype in the isolation of other Schiff bases. Yield: 40.3%. Molecular formula: C13H20N4. Analysis Calculated: C, 67.21; H, 8.68; N, 24.12. Found: C, 68.19; H, 8.89; N, 24.48. IR (ATR cm−1) 3308.37 n(N-H), 2945.30 n(C-H), 1640.05 n(C=N), 1586.63 n(C=N)pyr, 1464.94, 1436.55 n(C-C), 1132.42 n(C-N). UV-Vis (DMSO) 281.00 (n→π*); 224.00 (π→π*). 1H-NMR (DMSO-d6) 8.30–7.85 (4H, CH-Ar), 3.98–3.69 (CH2-Pip.), 2.9 (NH-) 2.75–2.55 (NCH2-CH2N), 1.21 (CH3-). 13C-NMR (DMSO-d6) 168.43 [1C, δ(C=N)], 148.47 δ(C), 140.44 δ(CH), 127.93 δ(CH), 123.79 δ(CH), [5C, δ(Ar-pyr)], 51.72 [2C, δ(2CH2)], 44.19 [2C, δ(2CH2)], 42.04 [2C, δ(CH2)], 15.79 [1C, δ(CH3)].
N1,N1-Dimethyl-N2-(1-(pyridin-2-yl)ethylidene)ethane-1,2-diamine (3): An accurately measured amount of 2-acetylpyridine (0.61 g, 5 mmol) and N,N-dimethylethyldiamine (0.44 g, 5 mmol) in ethanol (25 mL) was refluxed for three hours.
Yield: 54%. Molecular formula: C11H17N3 (191.27). Analysis Calculated: C, 69.87; H, 8.80; N, 13.58. Found: C, 68.48; H, 8.98; N, 14.98. IR (ATR cm−1) 2925.46 n(C-H) 1639.70 n(C=N) 1566.34 n(C=N)pyr, 1464.83, 1435.25 n(C-C), 1153.71, 1103.38 n(C-N). UV-Vis (DMSO) 321 (n→π*); 233 (π→π*).1H-NMR (DMSO-d6) 8.28–7.87 (CH2-Ar), 2.76–2.68 (NCH2-CH2N), 1.22 (CH3-), 1.9 (6H, CH3-N). 13C-NMR (DMSO-d6) 166.59 [1C, δ(C=N)], 147.58 δ(C), 145.83 δ(CH), 139.56 δ(CH), 126.82 δ(CH), [5C, δ(Ar-pyr)], 54.43 [2C, δ(2CH2)], 43.44. 43.29 [2C, δ(2CH3)], 14.69 [1C, δ(CH3)].
Aqua{Dithiocyanato-(2-morpholino-N-[1-(2-pyridylethylidene]ethanamine N,N',N''}cadmium(II) (4): A mixture of 2-acetylpyridine (0.20 g, 1.65 mmol) and 4-(2-aminoethyl)morpholine (0.21 g, 1.65 mmol) in ethanol (20 mL) was refluxed for 2 h followed by addition of a solution of cadmium(II) acetate dihydrate (0.44 g, 1.65 mmol) and sodium thiocyanate (0.268 g, 3.30 mmol) in a minimum amount of water. The mixture was refluxed for 2–3 h resulting in the formation of small amount of precipitate. More precipitate was obtained by removal of some solvent.
The product was collected by filtration, washed several times with ethanol until a white colored compound is obtained. It was re-crystallized from the same solvent (ethanol), filtered to remove the suspended impurities. Yield = 75%. Melting point >400 °C. Analysis Calculated: [C, 39.09; H, 4.37; N, 18.23; S, 13.91]. Found: [C, 39.29; H, 4.17; N, 18.13; S, 13.61]. IR (ATR cm−1) 2981.09 n(C-H), 2157.91, 2083, n(N=C=S), 1651.16 n(C=N), 1438.25 n(C-C), 1107.15 n(C-N), 659.88 n(OH2) 565.42 n(M-N). UV-Vis (DMSO) 407 (LMCT), 285 (n→π*); 234 (π→π*). 1H-NMR (DMSO-d6) 8.80 [s, 1H, δ(Ar-H)pyr], 8.29–8.24 [m, 2H, δ(Ar-H)pyr], 7.87–7.85 [t, 1H, δ(Ar-H)pyr], 3.80, 3.76 [d, 4H, δ(2CH2)], 3.69 [s, 4H, δ(2CH2)], 2.79–2.77 [t, 4H, δ(N-CH2)], 2.69 [s, 3H, δ(CH3)]. 13C-NMR (DMSO-d6) 165.80 [1C, δ(C=N)], 149.24 δ(C), 140.55 δ(CH), 132.31 δ(CH), 127.68 δ(CH), 124.29 δ(CH) [5C, δ(Ar-pyr)], 64.76, 57.88 [4C, δ(2CH2) morph], 53.44, 44.36 [2C, δ(2CH2)], 21.98 [δ(SCN)], 15.77 [1C, δ(CH3)].
Aqua{Dichlorido Piperazin-4-ium1-(2-pyridyl)ethylidene]ethanamine N,N′,N′′}cadmium (5): A mixture of 2-acetylpyridine (0.61 g, 5 mmol) and 4-(2-aminoethyl)piperazine (0.65 g, 5 mmol) in ethanol (50 mL) was refluxed for 2 h followed by addition of a solution of cadmium(II) chloride (0.92 g, 5 mmol) in a minimum amount of water was added. The mixture was refluxed for 2–3 h resulting in the formation of white precipitate.
More precipitate was obtained by removal of some solvent. Analysis Calculated: C, 23.61; H, 3.55; N, 10.14. Found: C, 23.65; H, 3.75; N, 10.24. IR (ATR cm−1) 3469.07 n(N-H), 2953.13 n(C-H), 1654.02 n(C=N), 1438.11 n(C-C), 1121.21 n(C-N), 652.14 n(OH2) 557.10 n(M-N). UV-Vis (DMSO) 497 (LMCT), 281 (n→π*); 229 (π→π*). 1H-NMR (DMSO-d6) 8.73–7.83 [m, 4H, δ(Ar-H)pyr], 3.92, 3.81 [d, 4H, δ(2CH2)], 3.3–3.0 [t, 4H, δ(2CH2)], 2.82–2.80 [2H, δ(N-CH2)], 2.76 [2H, δ(NH-)], 2.38–2.36 [t, 2H, δ(CH2=)], 2.30 [sbr, 1H, δ(NH)] 2.23 [s, 3H, δ(CH3)]. 13C-NMR (DMSO-d6) 166.938 [1C, δ(C=N)], 157.942, 146.101, 137.967, 131.059, 124.085 [5C, δ(Ar-pyr)] 108.095, 106.975 [δ(2CH2)], 69.65 [2C, δ(2CH2)], 40.67 [1C, δ(CH2)], 46.00 [1C, δ(CH2)], 18.95 [1C, δ(CH3)].
Chlorido(2-{1-[(2-morpholinoethyl)imino]ethyl}phenolato N,N′,N′′)copper(II) (6): A mixture of 2-acetylpyridine (0.20 g, 1.65 mmol) and 4-(2-aminoethyl) morpholine (0.21 g, 1.65 mmol) in ethanol (20 mL) was refluxed. After 2 h a solution of copper (II) chloride dihydrate (0.28 g, 1.65 mmol) in a minimum amount of ethanol was added. The mixture was refluxed for 2–3 h resulting in the formation of a small precipitate. More precipitate was obtained by removal of some solvent.
The product was collected by filtration, washed several times with ethanol until a green colored compound is obtained. It was re-crystallized from the same solvent (ethanol), filtered to remove the suspended impurities. Yield = 77%. Melting point 375–380 °C. Analysis Calculated: [C, 42.46; H, 5.21; N, 11.43]. Found: [C, 42.19; H, 5.11; N, 11.39]. IR (ATR cm−1) 2949.37 n(C-H), 1654.51 n(C=N), 1443.03 n(C-C), 1144.39 n(C-N), 577.38 n(M-N). UV-Vis (DMSO) 645.50 (d→d*); 337.00 (LMCT); 309.00 (n→π*); 223.00, 219.00 (π→π*).
Dibromido{2-morpholino-N-[1-(2-pyridyl ethylidene ethanamine N,N′,N′′}cadmium (7): A mixture of 4-(2-aminoethyl)morpholine (0.65 g, 5 mmol) and 2-acetylpyridine (0.61 g, 5 mmol) in ethanol (50 mL) was refluxed for 2 h followed by addition of a solution of cadmium(II) acetate dihydrate (0.44 g, 1.65 mmol) and potassium bromide (0.196 g, 1.65 mmol) in a minimum amount of water was added. The mixture was refluxed for 2–3 h resulting in the formation of a white precipitate. More precipitate was obtained by removal of some solvent.
The product was collected by filtration, washed several times with ethanol until a white colored compound is obtained. It was re-crystallized from the same solvent (ethanol), filtered to remove the suspended impurities. Yield = 81%. Melting point >400 °C. Analysis Calculated: C, 37.48; H, 4.60; N, 10.09. Found: C, 37.28; H, 4.45; N, 10.19. IR (ATR cm−1) 296202 n(C-H), 1650.04 n(C=N), 1458.80 n(C-C), 1115.11 n(C-N), 556.01 n(M-N). UV-Vis (DMSO) 398 (LMCT), 279 (n→π*); 229 (π→π*). 1H-NMR (DMSO-d6) 8.69–8.68 [d, 1H, δ(Ar-H)pyr], 8.29–8.24 [m, 2H, δ(Ar-H)pyr], 7.85 [s, 1H, δ(Ar-H)pyr], 3.93, 3.80 [d, 4H, δ(2CH2)], 3.73–3.71 [t, 2H, δ(N-CH2)], 2.81, 2.80, 2.80, 2.72, 2.70 [m, 6H, δ(3CH2) morph], 2.55 [s, 3H, δ(CH3)]. 13C-NMR (DMSO-d6) 166.90 [1C, δ(C=N)], 149.13 δ(C), 147.64 δ(CH), 140.55 δ(CH), 127.72 δ(CH), 124.42 δ(CH), [5C, δ(Ar-pyr)], 64.65 [2C, δ(2CH2)], 53.49 [2C, δ(2CH2)], 36.00 [1C, δ(CH2)], 30.67 [1C, δ(CH2)], 15.95 [1C, δ(CH3)].
Dibromido {2-morpholino-N-[1-(2-pyridyl) ethylidene] ethanamine N,N′,N′′}zinc (8): A mixture of 2-acetylpyridine (0.20 g, 1.65 mmol) and 4-(2-aminoethyl) morpholine (0.21 g, 1.65 mmol) in ethanol (20 mL) was refluxed. After 2 h a solution of zinc (II) acetate dihydrate (0.36 g, 1.65 mmol) and potassium bromide (0.196 g, 1.65 mmol) in a minimum amount of water. The mixture was refluxed for 2–3 h resulting in the formation of a small amount of precipitate. More precipitate was obtained by removal of some solvent.
The product was collected by filtration, washed several times with ethanol until a milky colored compound is obtained. It was re-crystallized from the same solvent (ethanol), filtered to remove the suspended impurities and a single crystal was obtained suitable for x-ray analysis. Yield = 85%. Melting point >400 °C. Analysis Calculated: C, 30.89; H, 3.79; N, 8.31. Found: C, 30.79; H, 3.49; N, 8.28. IR (ATR cm−1) 2959.01 n(C-H), 1649.00 n(C=N), 1439.00 n(C-C), 1114.11 n(C-N), 561.12 n(M-N). UV-Vis (DMSO) 498 (LMCT), 289 (n→π*); 229 (π→π*). 1H-NMR (DMSO-d6) 8.78, 8.77 [d, 1H, δ(Ar-H)pyr], 8.30–8.25 [m, 2H, δ(Ar-H)pyr], 7.89–7.87 [t, 1H, δ(Ar-H)pyr], 3.89 [s, 4H, δ(2CH2)], 3.85–3.83 [t, 2H, δ(CH2)], 2.91–2.90 [t, 6H, δ(N-CH2)], 2.62 [s, 3H, δ(CH3)]. 13C-NMR (DMSO-d6) [1C, δ(C=N)], 168.38 δ(C), 146.49 δ(CH), 140.65 δ(CH), 128.03 δ(CH), 124.05 δ(CH) [5C, δ(Ar-pyr)], 62.88 [2C, δ(2CH2)], 54.55 [2C, δ(2CH2)], 52.09 [1C, δ(CH2)], 44.12 [1C, δ(CH2)], 15.86 [1C, δ(CH3)].
N,N-Dimethyl-N'-[1-(2-pyridyl)ethylidene]ethane-1,2-diamine-3N,N′,N′′}bis(thiocyanate)zinc(II) (9): A mixture of 2-acetylpyridine (0.61 g, 5 mmol) and N,N-dimethylethyldiamine (0.44 g, 5 mmol) in ethanol (50 mL) was refluxed for 2 h followed by addition of a solution of Zinc (II) acetate (0.92 g, 5 mmol) and sodium thiocyanate (0.406 g, 5 mmol) in a minimum amount of water. The mixture was refluxed for 2–3 h resulting in the formation of a white precipitate. More precipitate was obtained by removal of some solvent.
The product was collected by filtration, washed several times with ethanol until a white colored compound is obtained. It was re-crystallized from the same solvent (ethanol), filtered to remove the suspended impurities. Yield = 72%. Melting point 370–375 °C. Analysis Calculated: C, 35.27; H, 4.57; N, 11.22. Found: C, 35.17; H, 4.67; N, 11.21. IR (ATR cm−1) 2949.02 n(C-H), 2070.00 n(N=C=S), 1655.03 n(C=N), 1438.38 n(C-C), 1139.09 n(C-N), 477.06 n(M-N). UV-Vis [λmax (nm) (DMSO)]. UV-Vis (DMSO) 497 (LMCT), 321 (n→π*); 233 (π→π*). 1H-NMR (DMSO-d6) 8.65, 8.64 [d, 1H, δ(Ar-H)pyr], 8.35–8.32 [m, 2H, δ(Ar-H)pyr], 7.95–7.94, 7.93 [m, 1H, δ(Ar-H)pyr], 3.79–3.77 [t, 2H, δ(N-CH2)], 2.77–2.75 [t, 2H, δ(CH2=)], 2.59 [s, 3H, δ(CH3)], 2.39 [s, 6H, δ(2CH3)]. 13C-NMR (DMSO-d6) 168.74 [1C, δ(C=N)], 147.99 δ(C), 147.16 δ(CH), 141.36 δ(CH), 135.03 δ(CH), 128.50 δ(CH) [5C, δ(Ar-pyr)], 56.35 [2C, δ(2CH3)], 44.55 [1C, δ(N-CH2)], 44.32 [1C, δ(CH2=)], 22.75 [δ(SCN)], 15.88 [1C, δ(CH3)].
Aqua {2-morpholino-N-[1-(2-pyridyl)ethylidene] ethanamine N,N′,N′′}bis(thiocyanato) nickel(II) (10): A mixture of 2-acetylpyridine (0.20 g, 1.65 mmol) and 4-(2-aminoethyl)morpholine(0.21 g, 1.65 mmol) in ethanol (20 mL) was refluxed for 2 h followed by addition of a solution of nickel(II) acetate tetrahydrate (0.41 g, 1.65 mmol) and sodium thiocyanate (0.134 g, 1.65 mmol) in a minimum amount of water. The mixture was refluxed for 2–3 h resulting in the formation of a greenish colored precipitate. More precipitate was obtained by removal of some solvent.
The product was collected by filtration, washed several times with ethanol until a green colored compound is obtained. It was re-crystallized from the same solvent (ethanol), filtered to remove the suspended impurities. Yield = 68%. Melting point 365–370 °C. Analytical Calculated: C, 42.27; H, 4.97; N, 16.43; S, 15.05. Found: C, 42.31; H, 4.98; N, 16.43; S, 15.09. IR (ATR cm−1) 2980.11 n(C-H), 2082.19 n(N=C=S), 1651.60 n(C=N), 1441.21 n(C-C), 1106.78 n(C-N), 659.16 n(OH2) 515.83 n(M-N), 461.51 n(M-O). UV-Vis (DMSO) 745.00 (d→d*); 574.00 (LMCT); 279.00 (π→π*).