1846
Z.A. Siddiqi et al. / Spectrochimica Acta Part A 71 (2009) 1845–1850
heated under N2 atmosphere to a melt at 180 ◦C for about 2 h
on an oil bath. The reaction mixture was slowly brought to room
temperature, which gave a dark coloured wax like product. The
wax was extracted with 100 mL methanol, filtered off and the
dark coloured insoluble residue was discarded after washing with
methanol. The methanol extract was dried under vacuum giving
a yellow colour wax type product. It was kept for about 6 weeks
in a desiccator over CaCl2, which changed to a hard mass. The
hard mass was crushed to a fine powder and was recrystallized
from methanol [yellow colour, m.p. 142 ◦C, yield 8.6 g, 79%]. Anal.
calc. for C8H15N5: C, 53.03; H, 8.28; N, 38.67, found for (Im) C,
53.07; H, 8.34; N, 38.65, FAB-mass (m-nitrobenzylalcoho NBA,
matrix): [Im–2H + Bz3]+ (m/z = 333) [Im + 2H + Bz4]+ (m/z = 472)
m/z = 368, [Fe(BIm) + H]+ m/z = 334. [The spectra of the complexes
contained bunch of peaks pertinent with the natural isotopes abun-
dance ratio. The Fe as well as Cl nuclei are known to exhibit two
naturally occurring isotopes with varying natural abundance. The
m/z value of the isotope having highest intensity have been consid-
ered].
2.4. Physico–chemical measurements
IR spectra were recorded on a Perkin–Elmer spectrum GX
automatic recording spectrophotometer as KBr disc. 1H and 13C
NMR spectra of compounds dissolved in CD3OD were recorded
on a Brucker DRC-300 spectrometer using SiMe4 (TMS) as inter-
nal standard. Electronic spectra of 10−3 M solutions in CH3OH
were obtained on a Cintra 5GBS automatic recoding spectropho-
tometer at room temperature. FAB-mass spectra were recorded
on Jeol SX-102/DA-6000 mass spectrometer using argon (6 kV,
10 mA) as the FAB gas. The accelerating voltage was 10 kV and
the spectra were recorded in m-nitrobenzyl alcohol (NBA) matrix.
The matrix peaks appeared at m/z = 136, 137, 154, 289 and 307.
Magnetic susceptibility on the solid complexes were made at RT
by Gouy method using Hg[CoNCS)4] caliberant. The Mössbauer
measurements were performed at IUC-DAE, Indore, India using a
multi-channel analyzer in constant accelerating mode. The source
was Co57 in Rh matrix (15 mci strength) and the instrument was
caliberated with respect to natural Fe. The data were analyzed
using least square program, NORMOS-SITE. Microanalysis for C,
H and N were obtained from Microanalytical Laboratories, CDRI,
Lucknow.
[Im + 2H + Bz5]+
(m/z = 490)
[Im–CH2CH2 + Bz3]
(m/z = 307)
[Im–CH2CH2 + 2H + Bz4]+ (m/z = 444) [Im–NH.CH2CH2.H + Bz1]+
(m/z = 273) [Im–C.NH.N–CH2CH2 + Bz4] (m/z = 413) [Im–C2H4
(NH)N.C.CH2.NH] (m/z = 218); [Fragments for NBA matrix, appear
at m/z = 136 (Bz1), 137 (Bz2), 154 (Bz3), 289 (Bz4) and 307 (Bz5)]. 1
H
NMR (CD3OD, ppm) ı: 3.32 (t, 4H, JH–H = 5.6 cps, –CH2–)im, 3.41 (t,
4H, JH–H = 5.8 cps, –CH2–)im, 4.50 (s, 4H, –CH2–). 13C NMR (CD3OD,
ppm) ı: 161.4 (C N)im, 53.3 (–CH2–N), 34.5, 52.4 (–CH2–)im
.
2.2.2. Synthesis of bis(1H-benzimidazol-2yl-methyl)amine (BIm)
It was prepared in an analogous manner as following: imin-
odiacetic acid (8.0 g, 60.0 mmol) and 1,2-diaminobenzene (13.0 g,
120.0 mmol) were ground and thoroughly mixed in a mortar as a
fine homogeneous mixture. This mixture was taken in a pyrex tube
along with a few drops of o-phosphoric acid. It was sealed under N2
atmosphere then heated at 190 ◦C for 2 h immersed in an oil bath.
On cooling brought to room temperature a dark coloured hard
solid mass was obtained, which was crushed to fine powder. It was
extracted in a magnetically agitated 500 mL of methanol, filtered
off and the black residue was discarded. The brown colour extract
was evaporated to dryness under vacuum to give microcrystalline
solid. The solid was recrystallized from methanol [pink colour, m.p.
160 ◦C, yield 10.80 g, ∼65%]. Anal. calc. for C16 H15N5: C, 69.31; H,
5.41; N, 25.27. Found for (BIm): C, 69.34; H, 5.29; N, 25.29. FAB-mass
of BIm (m-nitrobenzylalcoho NBA, matrix): [BIm + H]+ (m/z = 278),
3. Results and discussion
The ligand, bis(4,5-dihydro-1H-imidazol-2-yl-methyl)amine
(Im) was prepared employing
a ring closure condensation
reaction between iminodiacetic acid, NH–(CH2COOH)2 and 1,2-
diaminoethane, NH2(CH2)2NH2 in presence of ortho-phosphoric
acid under melt condition (∼190 ◦C) in a closed reaction vessel
(Section 2). The substituted analogue, bis(1H-benzimidazol-2yl-
methyl)amine (BIm) was also obtained in an analogous manner
using the aromatic analogue 1,2-diaminobenzene NH2C6H4NH2.
The presence of ortho-phosphoric acid facilitates the condensation
reaction as a catalyst affording a fairly good yield (yield > 60%) of
the final products. The spectral studies presented here confirm the
proposed ring closure mechanism as shown in Figure 1S (Supple-
mental Information) leading to the formation of (Im) or (BIm). The
two imidazoline or benzimidazole rings of (Im) or (BIm) are bonded
to a secondary amine function via methylene (–CH2–) skeleton or
linkage. The ligands provide three potential sites to coordinate Fe3+
ion as tridentate chelating ligand resulting in complexes of stoi-
chiometry FeLCl3 [L = Im (1) or BIm (2)].
[BIm–C6H4(NH)NC]
(m/z = 160),
[BIm–C6H4(NH)N.C.CH2]
(m/z = 146), [BIm–C6H4(NH)N.C.CH2.NH] (m/z = 131), [BIm–C6H4
(NH)N.C.CH2.NH + H]+ (m/z = 132), [C6H4(NH)N + 3H]+ (m/z = 108),
[C6H4(NH)N + 2H + Bz3]+ (m/z = 261), [BIm + Bz3] (m/z = 431).
UV–visible (CH3OH) 390 nm (ε = 1.5 × 103 Lmol−1 cm−1). 1H NMR
(CD3OD, ppm) ı: 7.22 (m, 4H, ring proton), 7.53 (m, 4H, ring
protons), 4.16 (s, 4H, CH2 ). 13C NMR (CD3OD, ppm) ı: 140.5
(C N)im, 115.2, 124.6,140 (C C)ar, 40.7 (–CH2–N).
2.3. Synthesis of [Fe(Im)Cl3] (1) and [Fe(BIm)Cl3] (2)
A methanolic solution (10 mL) of anhydrous ferric chloride
(0.64 g, 4.0 mmol) was dropped to a magnetically stirred solution
of the ligand (4.0 mmol) taken in 60 mL methanol with stir-
ring at room temperature. Reddish-yellow colour solution was
formed after complete addition of the metal salt. The reaction
mixture was stirred for ∼2 days at room temperature, which
gave yellow coloured precipitate. The precipitate was filtered
off, washed with three portions of 2 mL methanol and dried in
vacuo [m.p. 186 ◦C (1); 162 ◦C (2)]. Anal. Calc. for C16 H15N5FeCl3:
C, 27.94; H, 4.36; N, 20.37. Found for (1): C, 27.84; H, 3.31;
N, 20.45. FAB-mass of (1) (m-nitrobenzylalcoho NBA, matrix):
[Fe(Im)Cl3 + H]+ m/z = 343, [Fe(Im)Cl2–H]+ m/z = 306, [Fe(Im)Cl]+
m/z = 272, [Fe(Im) + H]+ m/z = 238. Anal. Calc. for C16 H15N5FeCl3:
C, 47.66; H, 3.72; N, 17.37. Found for (2): C, 47.23; H, 3.64;
N, 17.24. FAB-mass of (2) (m-nitrobenzylalcoho NBA, matrix):
[Fe(BIm)Cl3 + H]+ m/z = 439, [Fe(BIm)Cl2]+ m/z = 403, [Fe(BIm)Cl]+
3.1. Analytical and FAB-mass spectral studies
Analytical data of compounds are consistent with their pro-
posed molecular formulae (Section 2). FAB-mass spectral data
further supported the proposed stoichiometries of the compounds.
FAB-mass spectrum of (BIm) exhibited a strong intensity (99%
abundance) peak at m/z = 278 assignable to the molecular ion
[(BIm) + H]+. However, for (Im) the spectrum peaks did not contain
peaks assignable to any of the various probable molecular ions viz.
[(Im) + 2H]+, [(Im) + H]+, [(Im)]+, [(Im)–H]+ or [(Im)–2H]+, expected
at m/z = 183, 182, 181, 180 or 179, respectively. A low volatility
coupled with a small thermal stability of the expected molecular
ion (s) are usually responsible for an absence of the characteristic
peak. It is possible that the molecular ion is quite reactive adding