820
Rakesh Kumar Gupta et al.
4-impdpm, 4-nimpdpm and 4-bimpdpm were synthe- 2.1c 5-(4-benzimidazol-1-yl-phenyl)-dipyrromethane
sized by the procedure described by Magdolen et al. (4-bimpdpm): It was prepared by following the above
with slight modifications33 and the precursor complex procedure for 1 using 4-impdpm (4.44 g, 0.02 mol).
Cu(acac)2 following literature procedure.34 Elemen- Yield: 50% (3.85 g). Anal. Calc. for C22H18N4: C,
tal analyses for C, H and N were performed on an 78.08; H, 5.36; N, 16.56%. Found: C, 78.15; H, 5.39;
1
Exeter Analytical Inc. Model CE-440 Elemental Ana- N, 16.49%. H NMR (CDCl3, δ ppm): 5.59 (s, 1H,
lyzer. IR spectra (4000–400 cm−1) were acquired on meso-H), 5.60 (s, 2H, pyr-H), 6.18 (s, 2H, pyr-H), 6.77
a Varian 3300 FT-IR spectrometer. Electronic absorp- (s, 2H, pyr-H), 7.35-7.40 (m, 6H), 7.56 (s, 1H), 7.79 (s,
tion and emission spectra were obtained on Shimadzu 1H), 7.82 (s, 1H, imi-H), 8.58 (bs, 2H, NH), IR (KBr
UV-1701 and Varian Cary Eclipse Fluorescence pellet, cm−1): 3256, 3122, 2961, 1676, 1615, 1581
spectro-photometers, respectively. 1H (300 MHz) NMR 1543, 1517, 1492, 1423, 1408, 1350, 1305, 1265, 1120,
spectra was acquired on a JEOL AL300 FT-NMR spec- 1095, 1068, 1025, 823, 773, 730.
trometer using tetramethylsilane (TMS) as an internal
reference. Room temperature magnetic susceptibility
measurements were performed on a Cahn–Faraday
balance using Hg[Co(SCN)4] as a calibrant.
2.1d [Cu3(4-impdpm)2(hfacac)4] (1): To a stirr-
ing ice cooled dichloromethane solution (50 mL)
of 4-impdpm (0.288 g, 0.001 mol), DDQ (0.228 g,
1.0 mmol) dissolved in benzene (30 mL) was added
drop-wise and stirred for an hour. A methanolic (20 mL)
2.1 Syntheses
solution of Cu(hfacac)2·2H2O (0.496 g, 0.001 mol) was
added to it and stirred for 20 min. The reaction mix-
2.1a 5-(4-imidazol-1-yl-phenyl)-dipyrromethane (4-
impdpm): To a flask containing pyrrole (19.34 g),
4-imidazol-1-yl-benzaldehyde (3.44 g, 0.02 mol) was
added and heated at 120◦C with stirring under inert
atmosphere for 24 h. After cooling to ambient tem-
perature it was concentrated to dryness under reduced
pressure and the crude product purified by column chro-
matography [alumina; ethylacetate: dichloromethane
(1 : 1)]. Yield: 38% (2.19 g). Anal. Calc. for C18H16N4:
C, 74.96; H, 5.60; N, 19.44%. Found: C, 75.29; H,
ture was evaporated to dryness and crude product puri-
fied by column chromatography (SiO2: CHCl3 with 1%
MeOH) to afford a red solid. Dichroic reddish-green
crystals of 1 were obtained from CH2Cl2/ hexane (1
: 1) solution. Yield: 30% (0.190 g). Anal. Calc. for
C36H26N8Cu: C, 68.18; H, 4.13; N, 17.67%. Found: C,
68.38; H, 4.30; N, 17.55%. ESI-MS (m/z) obs (calcd.):
634 [M+H]+ (634). IR (KBr pellet, cm−1): 2923, 1606,
1546, 1377, 1335, 1244, 1185, 1109, 1035, 995, 893,
809, 775, 727, 654. UV-Vis. (CH2Cl2, λmax nm; ε,
M−1cm−1): 496 (39880), 332 (15655), 300 (33852).
1
5.47; N, 19.52%. H NMR (CDCl3, δ ppm): 5.54 (s,
1H, meso-H), 5.92 (s, 2H, pyr-H), 6.18 (q, 2H, J =
3.0 Hz, pyr-H), 6.74 (s, 2H, pyr-H), 7.19–7.32 (m, 6H),
7.80 (s, 1H, imi-H), 8.04 (bs, 2H, NH). IR (KBr pellet,
cm−1): 3255, 3115, 2966, 1655, 1567, 1518, 1431,
1305, 1253, 1112, 1058, 819, 774, 724.
2.1e [Cu(4-nimpdpm)(acac)] (2): It was prepared
following the above procedure for 1 using 4-
nimpdpm (0.288 g, 0.001 mol) and Cu(acac)2 (0.288 g,
0.001 mol). Yield: 35% (0.172 g). Anal. Calc. for
C23H19N5O4Cu: C, 56.04; H, 3.88; N, 14.21%. Found:
C, 56.24; H, 4.00; N, 14.33%. ESI-MS (m/z) obs
(calcd.): 492 [M]+ (492). IR (KBr pellet, cm−1): 2906,
1582, 1550, 1406, 1392, 1378, 1336, 1244, 1206, 1178,
1118, 1080, 1028, 994, 892, 818, 770, 732, 654. UV-
Vis. (CH2Cl2, λmax nm; εM−1cm−1 ): 490 (39764), 320
(15770), 233 (21567).
2.1b 5-(4-(4-nitro-imidazol)-1-yl-phenyl)-dipyrromethane
(4-nimpdpm): It was prepared by following the above
procedure for 4-impdpm using 4-(4-nitro-imidazol-
1-yl)-benzaldehyde (4.34 g, 0.02 mol). Yield: 40%
(2.67 g). Anal. Calc. for C18H15N5O2: C, 64.84; H,
4.54; N, 21.01%. Found: C, 65.00; H, 4.62; N, 21.30%.
1H NMR (CDCl3, δ ppm): 5.46 (s, 1H, meso-H), 5.89
(s, 2H, pyr-H), 6.18 (s, 2H, pyr-H), 6.70 (s, 2H, pyr-H),
7.35-7.40 (m, 4H), 7.71 (s, 1H, imi-H), 8.04 (bs, 2H,
NH), 8.06 (s, 1H, imi-H). IR (KBr pellet, cm−1): 3248,
3124, 2968, 1678, 1610, 1590, 1542, 1514, 1490, 1426,
1406, 1350, 1304, 1268, 1122, 1092, 1068, 1024, 822,
774, 732.
2.1f [Cu(4-nimpdpm)(hfacac)] (3): It was synthe-
sized adopting the above procedure for 1 using 4-
nimpdpm and Cu(hfacac)2·2H2O. Yield: 28% (0.168 g).
Anal. Calc. for: C, 46.00; H, 2.18; N, 11.65%. Found: C,
45.88; H, 2.32; N, 11.79%. ESI-MS (m/z) obs (calcd.):
600 [M]+, (600). IR (KBr pellet, cm−1): 2923, 1648,