Spectroscopic studies of bimetallic complexes derived from tridentate or tetradentate Schiff bases of some di- and tri-valent transition metals

Article abstract of DOI:10.1016/j.saa.2005.09.010

Two series of new binuclear complexes with Schiff base ligands, H₄L_a or H₂L_b, derived from the reaction of 4,6-diacetylresorcinol and ethylenediamine, in the molar ratio 1:1 and 1:2 have been prepared, respectively. The two ligands react with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Cr(III) and Fe(III)-nitrates to get binuclear complexes. The ligands were characterized by elemental analysis, IR, UV-vis, ¹H NMR and mass spectra. The complexes were synthesized by direct and template methods. Different types of products were obtained for the same ligand and metal salts according to the method of preparation. The H₄L_a ligand behaves as a macrocyclic tetrabasic with two N₂O₂ sits, while the H₂L_b ligand behaves as a dibasic with two N₂O sites. The H₄L_a ligand is a compartmental ligand which hosts the two metal ions at the centers of two cis-N₂O₂ sites, while the metal complexes of H₂L_b ligand are binuclear, where the ligand hosts two metal ions at the centers of two N₂O sites. In both cases, deprotonation of the hydrogen atoms of the phenolic OH groups occur except in the case of the Ni(II), Fe(III) and Cr(III) complexes. Electronic spectra and magnetic moments of the complexes indicate that the geometries of the metal centers are either octahedral or tetrahedral. The structures are consistent with the IR, UV-vis, ESR, ¹H NMR, mass spectra, and thermal gravimetric analysis (TGA/DTA) as well as conductivity and magnetic moment measurements.

Full text of DOI:10.1016/j.saa.2005.09.010

Spectrochimica Acta Part A 64 (2006) 1010–1024
Spectroscopic studies of bimetallic complexes derived from tridentate or
tetradentate Schiff bases of some di- and tri-valent transition metals
Adel A.A. Emaraa,∗, Azza A.A. Abou-Hussenb
a Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo 11341, Egypt
b Department of Chemistry, Girl’s College for Arts, Science and Education, Ain Shams University, Cairo, Egypt
Received 19 July 2005; received in revised form 12 September 2005; accepted 12 September 2005
Abstract
Two series of new binuclear complexes with Schiff base ligands, H4La or H2Lb, derived from the reaction of 4,6-diacetylresorcinol and
ethylenediamine, in the molar ratio 1:1 and 1:2 have been prepared, respectively. The two ligands react with Co(II), Ni(II), Cu(II), Zn(II),
Cd(II), Cr(III) and Fe(III)-nitrates to get binuclear complexes. The ligands were characterized by elemental analysis, IR, UV–vis, 1H NMR and
mass spectra. The complexes were synthesized by direct and template methods. Different types of products were obtained for the same ligand
and metal salts according to the method of preparation. The H4La ligand behaves as a macrocyclic tetrabasic with two N2O2 sits, while the H2Lb
ligand behaves as a dibasic with two N2O sites. The H4La ligand is a compartmental ligand which hosts the two metal ions at the centers of two
cis-N2O2 sites, while the metal complexes of H2Lb ligand are binuclear, where the ligand hosts two metal ions at the centers of two N2O sites. In
both cases, deprotonation of the hydrogen atoms of the phenolic OH groups occur except in the case of the Ni(II), Fe(III) and Cr(III) complexes.
Electronic spectra and magnetic moments of the complexes indicate that the geometries of the metal centers are either octahedral or tetrahedral. The
structures are consistent with the IR, UV–vis, ESR, 1H NMR, mass spectra, and thermal gravimetric analysis (TGA/DTA) as well as conductivity
and magnetic moment measurements.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Binuclear transition metal complexes; Tetradentate N2O2 Schiff base ligands; Tridentate N2O Schiff base ligands
1. Introduction
In the present study, two series of binuclear complexes have
been prepared from Schiff base, H4La and H2Lb ligands derived
from the 4,6-diacetylresorcinol (DAR) and ethylenediamine
(en) in the molar ratio 1:1 and 1:2, respectively. The two ligands
react with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Cr(III) and
Fe(III)-nitrates. The complexes were characterized by elemental
Studies on the coordination chemistry of polydentate chelat-
ing ligands which enable the binding of two metal ions have
increasedconsiderably[1,2]. Recently, muchresearchonmacro-
cyclic complexes have been focused on species containing the
first-row transition metal ions and tetradentate ligands [3]. The
formation of macrocyclic complexes depends significantly on
the dimension of internal cavity, on the rigidity of the macro-
cycles, on the nature of its donor atoms and on the complexing
properties of the anion involved in the coordination [4,5]. The
interest in such species stems from the application of these
complexes ranging from modeling the active sites of many met-
alloenzymes [6,7], to hosting and carrying small molecules [8,9]
or catalysis [10,11].
1
analysis, IR, UV–vis, H NMR, thermal gravimetric analysis
(TGA/DTA) and ESR spectra, as well as the measurements
of conductivity and magnetic moments at room temperature.
Fig. 1 is representative structures of the Schiff base, H4La and
H2Lb ligands.
2. Experimental
2.1. Materials
The nitrate salts of Co(II), Ni(II), Cu(II), Zn(II), Cd(II),
Cr(III) and Fe(III), resorcinol, acetic anhydride, ethylenedi-
amine monohydrate, lithium hydroxide monohydrate, and zinc
chloride were Merck chemicals. Organic solvents were reagent
grade chemicals.
∗
Corresponding author. Tel.: +20 2 4551530; fax: +20 2 4530271.
E-mail addresses: adelaemara@yahoo.com, adelaemara@hotmail.com
(A.A.A. Emara).
1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2005.09.010

A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
1011
Fig. 1. The Schiff base, H4La and H2Lb, ligands.
2.2. Physical measurements
2.3. Synthesis of the Schiff base, H4La and H2Lb, ligands
Electronic spectra of the metal complexes, as DMF solu-
tions, were recorded on a Jasco 550 Spectrophotometer. IR
spectra of the ligand and its metal complexes, as KBr discs,
were recorded on a Perkin-Elmer 1430 Spectrometer. 1H NMR
spectra of the ligands and their Zn(II) and Cd(II) complexes,
as solutions in DMSO-d6, were recorded on a Bruker WP 200
SY Spectrometer at room temperature using TMS as an inter-
nal standard. Mass spectra were recorded at 300 ◦C and 70 eV
on a Hewlett-Packard mass Spectrometer model MS-5988 at
the Microanalytical Center, Cairo University, Egypt. Magnetic
susceptibilities of the complexes were measured at room temper-
ature using a Johnson Matthey, Alfa Products, model MKI mag-
netic susceptibility balance. The effective magnetic moments
were calculated from the expression µeff = 2.828(χMT)1/2 µB,
where χM is the molar susceptibility corrected using Pascal’s
constants for the diamagnetism of all atoms in the compounds
[12]. Thermal analysis studies were carried out by blending
the sample with 1% ␣-alumina. A TGA/DTA thermal analyzer,
manufactured by Theta Industries Inc., NY, USA was used pro-
vided with an electronic analytical balance model ER-180A
manufactured by A&D Company Limited, Texas, USA. Speci-
men holder was alumina–silica of capacity 0.5 g. The data were
collected by a microcomputer model TANDY 2500 via data
acquisition system manufactured by Theta Industries Inc., NY,
USA. TGA/DTA rate, from 25 to 150 ◦C was 10 ◦/min, and
from 150 to 800 ◦C was 5 ◦/min. ESR spectra of the copper
complexes were recorded on a JEOL microwave unit, JES-
FE2XG Spectrometer, at the National Research Centre, Giza,
Egypt. The magnetic field was calibrated with a 2,2-diphenyl-
1-picryl-hydrazyl sample purchased from Aldrich. Molar con-
ductance of 10−3 M solutions of the complexes in DMF were
measured on the Corning conductivity meter NY 14831 model
441 (USA). Microanalyses of carbon, hydrogen and nitrogen
were carried out at the Microanalytical Center, Cairo Univer-
sity, Egypt. Analyses of the metals in the complexes were
carried out by the dissolution of the solid complex in con-
centrated HNO3 acid, neutralizing the diluted aqueous solu-
tions with ammonia and the metal solutions were titrated with
EDTA.
The Schiff base, H4La and H2Lb, ligands were prepared in
two steps. The first step was acetylating of resorcinol (5.00 g,
45.5 mmol) with acetic anhydride (9.28 g, 91.0 mmol) in pres-
ence of excess zinc chloride (10.0 g, 73.4 mmol) at 140 ◦C in
a paraffin oil path. The hot mixture was cooled to room tem-
perature and poured onto 140 mL 50% dilute hydrochloric acid.
Orange precipitate was formed and increased with standing until
1 h. The orange crude product was obtained by filtration with
suction, washed with distilled water till the color of the filtrate
is nearly colorless. Orange needle crystals were obtained by
crystallization using either ethanol or acetic acid/water mixture.
The yield of 4,6-diacetylresorcinol (DAR) was 6.88 g, 78%, m.p.
179 ◦C.
The second step was the addition of a solution of ethylenedi-
amine monohydrate (en) (1.79 g, 22.9 mmol) in ethanol (40 mL)
to 4,6-diacetylresorcinol (DAR) in the molar ratio 1:1 and 2:1,
i.e. (4.45 g, 22.9 mmol, or 2.22 g, 11.4 mmol) for H4La or H2Lb
ligands, respectively, in ethanol (40 mL). The solutions were
refluxed for 3 h. An orange (H4La) or creamy (H2Lb) crystals
were formed on cooling the solutions slowly to room temper-
ature and the precipitates were collected by filtration, washed
with ethanol then diethylether and finally air-dried. The yields
were 2.39 g (75%), m.p. 210 ◦C for H4La and 4.10 g (82%), m.p.
193 ◦C for H2Lb. Fig. 2 illustrates the synthetic scheme of the
Schiff base, H4La and H2Lb, ligands.
2.4. Synthesis of the transition metal complexes of the
Schiff base, H4La and H2Lb, ligands
Two different methods were followed in preparing the metal
complexes.
2.4.1. Non-template method
2.4.1.1. Without adding lithium hydroxide. Two moles of an
ethanolic solution of the metal nitrates were added gradually
with constant stirring to an ethanolic solution of 1 mol of
either the Schiff base, H4La or H2Lb, ligands. The reaction
is refluxed for 2 h, where the solid complexes were precipi-
tated and filtered off, washed with several portions of ethanol,

1012
A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
Fig. 2. Synthetic scheme for the preparation of the Schiff base, H4La and H2Lb, ligands; DAR: 4,6-diacetylresorcinol and en: ethylenediamine.
then diethylether and finally air-dried. The complexes are
air stable in the solid state, soluble in DMF and DMSO.
The following detailed preparations of [Cu2(La)]·3H2O, 2 and
[Co2(Lb)(NO3)2(H2O)2]·4H2O, 9 are given as examples for
these reactions. The other complexes were obtained similarly.
2.4.1.1.1. Synthesis of [Cu2(La)]·3H2O, 2. A solution of
Cu(NO3)2·2.5H2O (2.15 g, 9.25 mmol) in ethanol (20 mL) was
added gradually to a solution of the macrocyclic Schiff base
H4La ligand (2.02 g, 4.62 mmol) in ethanol (40 mL). The solu-
tion was stirred for 30 min and heated to reflux for 2 h. Brown
precipitate was formed on hot. The precipitate was filtered off,
washed with ethanol, then diethylether and finally air-dried. The
yield was 2.328 g (82%).
2.4.1.2. With adding lithium hydroxide. Reactions of the H4La
or H2Lb, ligands with the metal nitrate in the molar ratio 1:2 were
not successful in most cases to afford the corresponding com-
plexes in a pure form. On the other hand, LiOH·H2O was used
as deprotonating agent to the ligands. Then, the deprotonated
ligands react with the metal nitrates to afford the corresponding
complexes. However, the reaction of the deprotonated H2Lb lig-
and with metal nitrates cannot be taken as a general procedure
to afford the corresponding complexes. On the other hand, the
reaction of the deprotonated H4La ligand with the metal nitrates
gave the appropriate metal complexes. An example of this type
of preparation is as follows.
2.4.1.1.2. Synthesis of [Co(Lb)(NO3)2(H2O)2]·2H2O, 9.
A solution of Co(NO3)2·6H2O (2.911 g, 10.00 mmol) in ethanol
(40 mL) was added gradually to a solution of the Schiff base,
H2Lb, ligand (1.392 g, 5.00 mmol) in ethanol (40 mL). The solu-
tion was stirred for 30 min and heated to reflux for 3 h. Yellowish
brown precipitate was formed after cooling to room tempera-
ture. The precipitate was filtered off, washed with ethanol, and
then diethylether and finally air-dried. The yield was 1.860 g
(63%).
2.4.1.3. Synthesis of [Ni2(La)]·H2O (1a). A solution of
LiOH·H2O (0.776 g, 18.493 mmol) in methanol (20 mL) was
added gradually to a solution of the macrocyclic Schiff base,
H4La, ligand (2.018 g, 4.623 mmol) in ethanol (40 mL), to
affectthedeprotonation. AsolutionofNi(NO3)2·6H2O(2.151 g,
9.246 mmol) in ethanol (20 mL) was added gradually to the
above deprotonated ligand. The solution was stirred for 30 min
and heated to reflux for 5 h. Brownish red precipitate was formed
on hot. The precipitate was filtered off, washed with ethanol,
Fig. 3. Reaction of [Cu2(Lb)(NO3)2(H2O)2]·4H2O with 4,6-diacetylresorcinol to afford [Cu2(La)]·3H2O.

A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
1013
then diethylether and finally air-dried. The yield was 1.89 g
(72%).
2.4.2. Template method
A mixture of a solution of ethylenediamine monohydrate
(en) in ethanol (20 mL), 4,6-diacetylresorcinol (DAR) in ethanol
(30 mL) were added gradually to a solution of the metal nitrates
in ethanol (40 mL) in either the molar ratio 1:1:1 to obtain the
metal complexes of the macrocyclic H4La ligand, or in the molar
ratio 2:1:2 to obtain the metal complexes of H2Lb ligand. The
solutionswerestirredfor30 min, andheatedtorefluxfor3 h. The
solid complexes were precipitated and filtered off, washed with
ethanol then diethylether and finally air-dried. The complexes
are air stable in the solid state, soluble in DMF and DMSO.
The following detailed preparations are given as examples for
template reactions to obtain metal complexes of either H4La or
H2Lb, ligands and the other complexes were obtained similarly.
2.4.2.1. Synthesis of [Ni2(La)(H2O)4]·EtOH·4H2O (1b). A
solution mixture of [ethylenediamine monohydrate (0.445 g,
5.705 mmol) in ethanol (20 mL) and 4,6-diacetylresorcinol
(1.118 g, 5.705 mmol) in ethanol (30 mL)] were added gradu-
ally to a solution of the Ni(NO3)2·6H2O (5.703 g, 7.42 mmol) in
ethanol (40 mL) in the molar ratio 1:1:1, to obtain the nickel(II)
complex of the macrocyclic H4La ligand. The solutions were
stirred for 30 min, and heated to reflux for 3 h. The solid com-
plexes were precipitated and filtered off, washed with ethanol
then diethylether and finally air-dried. Green precipitates were
formed which, in both cases of the different molar ratios, gave
products of the same formula [Ni2(La)(H2O)4]·EtOH·4H2O
(1b). The complex is air stable in the solid state, soluble in
DMF. The yields were 1.752 g (83%) and 2.997 g (71%), for the
reactions in the molar ratios 1:1:1 and 2:1:2, respectively.
2.4.2.2. Synthesis of [Cr2(Lb)(NO3)2(H2O)2]·4H2O (11). A
solution mixture of [ethylenediamine monohydrate (0.445 g,
5.705 mmol) in ethanol (20 mL) and 4,6-diacetylresorcinol
(0.559 g, 2.853 mmol) in hot ethanol (30 mL)] were added grad-
ually to a solution of the Cr(NO3)3·9H2O (2.287 g, 5.705 mmol)
in ethanol (40 mL) in the molar ratio 2:1:2 to obtain the
chromium(III) complex of H2Lb ligand. The solution was stirred
for 30 min, and heated to reflux for 3 h. The solid complex
was precipitated and filtered off, washed with ethanol then
diethylether and finally air-dried. The complex is air stable in the
solid state, soluble in DMF and DMSO. The product obtained
has the same molecular formula [Cr2(Lb)(NO3)2]·6H2O, 11.
The yield was 2.235 g (64%).
2.4.3. Condensation reaction of
[Cu2(Lb)(NO3)2(H2O)2]·4H2O with 4,6-diacetylresorcinol
A trial to condense 4,6-diacetylresorcinol (DAR) with
the Cu(II) complex of ligand H2Lb to transfer it to that
of ligand H4La was carried out. This was performed
by adding a solution of 4,6-diacetylresorcinol (0.972 g,
5.00 mmol) in ethanol (30 mL) gradually to a solution of
[Cu2(Lb)(NO3)2(H2O)2]·4H2O (3.178 g, 5.00 mmol) in ethanol
(40 mL). The solution was stirred for 30 min and heated to reflux

1014
A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
for 2 h. A brown precipitate was formed on hot. The precipi-
tate was filtered off, washed with ethanol, and then diethylether
and finally air-dried. The yield was 2.393 g (78%). Fig. 3 rep-
resents the reaction of [Cu2(Lb)(NO3)2(H2O)2]·4H2O with 4,6-
diacetylresorcinol to afford [Cu2(La)]·3H2O.
Mass spectra were performed for H4La and H2Lb, ligands to
determine their molecular weights and fragmentation patterns.
The molecular ion peaks were observed at 436 and 278 m/e con-
firming their formula weights (F.W. 436 and 278) for H4La and
H2Lb ligands, respectively. The schematic fragmentation of the
H2Lb ligand is depicted in Fig. 4.
The 1H NMR spectrum of H4La ligand in DMSO-d6, Table 4
3. Results and discussion
a
shows signals at δ (ppm) 1.34 (s, 6H, 2CH3 ); 2.61 (s, 6H,
b
c
d
2CH3 ); 2.88 (m, 8H, 4CH2 ); 3.53 (m, 8H, 4CH2 ); 6.23
It is worthnoting that the different preparative methods,
mentioned above, leaded in most cases to the formation of
metal complexes with identical molecular formula except the
case of Ni(II) complexes of H4La ligand. The obtained metal
complexes and their physicochemical properties are shown in
Table 1.
(s, 2H, Ar-He); 8.40 (s, 2H, Ar-Hf) and 17.41 (s, br, 4H, Ar-
OHg). The H NMR spectrum of H2Lb in DMSO-d6 showed
1
a
b
signals at δ (ppm) 1.36 (s, 3H, CH3 ); 1.88 (s, 3H, CH3 );
ꢀ
2.10 (m, 2H, CH2 ); 2.44 (m, 2H, CH2c ); 3.01 (m, 2H, CH2 );
c
d
ꢀ
3.35 (m, 2H, CH2d ); 6.25 (s, 1H, Ar-He); 8.24 (s, 1H, Ar-Hf);
11.17 (s, br, 4H, 2NH2) and 17.45 (s, br, 2H, Ar-OHd) [13]
(see Table 4). It is observed that the signals due to the protons
17.41–17.45 ppm (Ar-OHd) and 11.17 ppm (NH2) completely
disappeared on adding D2O while the other signals still persist
at the same positions. Fig. 5 depicts the 1H NMR spectra of the
H4La and H2Lb ligands in DMSO-d6.
3.1. Schiff base, H4La and H2Lb, ligands
The Schiff base ligands were investigated by elemental anal-
ysis, infrared, UV–vis, mass spectra and 1H NMR spectra.
The physicochemical properties are listed in Table 1. The IR
spectra of the ligands, Table 2 shows broad band in the range
(3499–3378 cm−1)duetothestretchingvibrationofthephenolic
groups. The broadness may be due to the intermolecular hydro-
gen bonding between the phenolic groups and the azomethine
groups. The band at 1264–1267 cm−1 is ascribed to the phenolic
ν(C O) stretching vibrations while the strong bands observed at
1584–1602 cm−1 is assigned to the stretching vibrations of the
azomethine group [13].
3.2. Schiff base complexes of H4La and H2Lb ligands
3.2.1. Infrared spectra
The infrared spectra of the complexes exhibit broad bands
around 3499–3378 cm−1 assigned for ν(NH), ν(OH) of the
phenolic-OH group and the ν(OH) of water or ethanol molecules
associated with the complex formation which are confirmed
by elemental analysis. In addition, it is expected that the IR
spectra of all binuclear complexes show a shift of the strong
band of ν(C N) towards lower frequencies within the range of
15–25 cm−1 compared to the free ligand H4La and H2Lb spec-
trum (1584 cm−1 for H4La and 1602 cm−1 for H2Lb), but could
not be resolved due to the deformation of the crystalline water
or ethanol [14]. Therefore, the two-azomethine nitrogen atoms
The electronic spectra of the H4La and H2Lb, ligands
(10−3 M) in DMF, Table 3 shows mainly three bands at 220–230,
323 and 370–375 nm due to (1La → A1) and (1Lb → A1) tran-
sitions of the phenyl ring and ␲ → ␲* transition within the C N
group, in addition to a broad band at 410–412 nm due to the
n → ␲* transition which is overlapping with the intermolecular
CT from the phenyl ring to the azomethine group [13].
1
1
Table 2
Infrared frequencies of the characteristic bands of the Schiff base ligands (H4La and H2Lb) and their transition metal complexes
Ligand/complex
ν(OH) and ν(NH2) ν(C N) and δ(H2O) ν(C O)
ν(CH3) δ(NH2) ν(NO3)
ν(M O) ν(M N)
ꢀ
νs
νs
νas
H4La
H2Lb
3383 s, br
3499 m, 3378 m
3400 s, br
1584 vs
1602 s
1634 s
1636 s
1605 s
1636 s
1638 vs
1636 vs, 1602 s
1264 vs
1267 vs
1384 s, 1360 s 2987 m –
1384 s, 1362 s 3003 m –
1384 s, 1362 s 2924 m –
1384 s, 1360 s 2924 m –
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1533 m –
(1a) [Ni2(La)]·H2O
–
–
498 m
465 m
356 w
345 w
358 w
348 w
370 w
365 w
348 w
376 w
384 w
345 w
364 w
375 w
356 w
357 w
374 w
(1b) [Ni2(La)(H2O)4]·EtOH·4H2O
3400 s, br
(1c) [Ni2(H4La)(NO3)4]·2EtOH·6H2O 3422 s, br
1315 s 1008 s 1415 m 458 w
456 w
(2) [Cu2(La)]·3H2O
3400 s, br
3455 s, br
3496 s, br
–
–
–
(3) [Co2(H2La)(NO3)2]·2EtOH
(4) [Fe2(H2La)(NO3)4]·2H2O
(5) [Cr2(H2La)(NO3)4]·4EtOH
(6) [Zn2(H2La)(NO3)2]·3EtOH
(7) [Cd2(H2La)(NO3)2]·7H2O
(8) [Cu2(Lb)(NO3)2(H2O)2]·4H2O
(9) [Co2(Lb)(NO3)2(H2O)2]·2H2O
(10) [Fe2(H2Lb)(NO3)6]·4H2O
(11) [Cr2(Lb)(NO3)2(H2O)2]·4H2O
(12) [Zn2(Lb)(NO3)2(H2O)2]·4H2O
(13) [Cd2(Lb)(NO3)2(H2O)2]·3H2O
1384 s
2902 m –
1290 s 1008 s 1476 m 465 m
1315 s 1008 s 1410 m 460 m
1315 s 1008 s 1412 m 455 w
1290 s 1008 s 1472 m 465 m
1290 s 1008 s 1470 m 455 w
1384 s, 1366 s 2926 m –
1384 s, 1370 s 2924 m –
3412 s, br, 3350 m 1644 s, 1600 s
3422 s, br
3436 s, br
3428 s, br
3382 m
3382 m
3438 m
1641 vs, 1590 vs
1646 vs, 1590 vs
1586 s
1630 vs, 1590 s
1633 vs, 1591 vs
1640 vs, 1583 s
1604 vs, 1630 vs
1630 vs, 1602 s
1370 s
1381 s
1384 s
1385 s
1384 s
1384 s
1368 s
1368 s
2920 m –
2925 m –
2924 m 1530 s 1290 s 1008 s 1470 m 475 w
2924 m 1536 s 1290 s 1008 s 1475 m 471 w
2920 m 1536 s 1315 s 1008 s 1420 m 454 w
2924 m 1532 s 1315 s 1008 s 1412 m 434 w
2929 m 1534 s 1290 s 1008 s 1470 m 468 w
2925 m 1532 s 1290 s 1008 s 1472 m 475 w
3402 m
3498 m
s: strong, w: weak, m: medium, and br: broad, νs: a single degenerate state which is symmetrical about the principle axis, νas: antisymmetrical state with respect to
ꢀ
the three C2v axis, νs : a symmetrical state with respect to the three C2v axes.

Table 3
Electronic absorption bands (nm), magnetic moments (µB) and molar conductivities (ꢀ−1 cm2 mol−1) of the Schiff base ligands (H4La and H2Lb) and their transition metal complexes
µeff (µB) (ꢁb)
a
Ligand/complex
Electronic absorption bands (nm) and their assignment
d–d Transition assignment
1
1
*
*
1La → A
1Lb → A
␲–␲ (C N) n → ␲ and CT d–d transitioin
(phenyl ring)
(phenyl ring)
H4La
H2Lb
220 (0.95)
230 (0.96)
260 (0.93)
–
–
375 (0.55)
370 (0.54)
370 (0.65)
380 (0.58)
380 (0.52)
365 (0.49)
380 (0.48)
388 (0.33)
410 (0.54)
412 (0.54)
400 (0.33)
–
–
–
–
–
–
–
3.88
3.04
3.11
2.12
–
–
13
17
215
14
323 (0.83)
330 (0.84)
310 (0.88)
325 (0.86)
321 (0.79)
310 (0.81)
320 (0.89)
3
(1a) [Ni2(La)]·H2O
756 (0.13), 707 (0.10)
670 (0.09), 565 (0.07) (sh)
785 (0.08), 675 (0.06) (sh)
590 (0.22)
660 (0.01) (sh), 575 (0.06)
447 (0.02), 557 (0.02), 730 (0.01) Charge transfer tailing from UV to
3T1(P) ← T1(F)
3
(1b) [Ni2(La)(H2O)4]·EtOH·4H2O
3T1g(F) ← A2g(F)
3
(1c) [Ni2(H4La)(NO3)4]·2EtOH·6H2O 266 (0.92)
–
3T1g(F) ← A2g(F)
2
(2) [Cu2(La)]·3H2O
–
420 (0.40)
414 (0.39)
408 (0.42)
2T2g ← Eg
4
4
(3) [Co2(H2La)(NO3)2]·2EtOH
(4) [Fe2(H2La)(NO3)4]·2H2O
210 (0.90)
–
4A2g(F) ← T1g(F), 4T1g(P) ← T1g(F) 5.14
150
174
5.56
visible region.
4
(5) [Cr2(H2La)(NO3)4]·4EtOH
(6) [Zn2(H2La)(NO3)2]·3EtOH
(7) [Cd2(H2La)(NO3)2]·7H2O
(8) [Cu2(Lb)(NO3)2(H2O)2]·4H2O
(9) [Co2(Lb)(NO3)2(H2O)2]·2H2O
(10) [Fe2(H2Lb)(NO3)6]·4H2O
–
309 (0.92)
321 (0.79)
310 (0.81)
315 (0.79)
–
355 (0.40)
380 (0.52)
378 (0.43)
372 (0.50)
357 (0.52)
–
410 (0.38)
420 (0.40)
414 (0.39)
425 (0.34)
415 (0.24)
420 (0.40)
590 (0.34)
–
–
652 (0.24)
662 (0.02) (sh), 578 (0.07)
765 (0.02), 525 (0.01)
4T2g(F) ← A2g(F)
3.84
–
–
189
115
127
120
120
230
230 (0.96)
260 (0.93)
215 (0.92)
216 (0.93)
210 (0.90)
–
–
2T2g ← Eg
1.94
2
4A2g(F) ← T1g(F), 4T1g(P) ← T1g(F) 4.90
4
4
310 (0.81)
Charge transfer tailing from UV to
visible region.
5.83
4
(11) [Cr2(Lb)(NO3)2(H2O)2]·4H2O
(12) [Zn2(Lb)(NO3)2(H2O)2]·4H2O
(13) [Cd2(Lb)(NO3)2(H2O)2]·3H2O
210 (0.97)
230 (0.96)
260 (0.93)
309 (0.88)
310 (0.81)
320 (0.89)
350 (0.54)
378 (0.43)
372 (0.50)
400 (0.35)
414 (0.39)
408 (0.42)
570 (0.32)
–
–
4T2g(F) ← A2g(F)
3.53
–
–
136
140
139
–
–
Values of εmax are in parentheses and multiplied by 10−4 (mol−1 cm−1).
a
µeff is the magnetic moment of one cation in complex.
Molar conductivities were measured in DMF solvent with concentration × 10−3 M. Values are in ꢀ−1 cm2 mol−1
b
.

1016
A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
Fig. 4. Fragmentation of the Schiff base H2Lb ligand.
345–384 cm−1 regions can be assigned to ν(M N) and ν(M O),
respectively [14].
are contributed to form coordinate bonds with the metal. The IR
spectra of the complexes shows strong absorption bands which
are in consistent wit−h the mono- or bi-dentate nitrate vibra-
tions [14]. The NO3 ions are coordinated to the metal ion
as unidentate for the complexes 1c, 4, 5, 10 and 11 with C3v
symmetry. Each unidentate nitrate groups possess three non-
From the infrared spectra, it is apparent that, the chelation
of the divalent metal ions to the ligands occurs from the H4La
and H2Lb ligands through the oxygen atoms of the resorcinol
moiety and the nitrogen atoms of the azomethine groups in the
ligands. The nitrate ions and coordinated water molecules satisfy
the other coordination sites to complete the geometry of the
central metal ion. Fig. 6 is the proposed structure the binuclear
complexes.
ꢀ
degenerate modes of vibrations (νs, νs and νas), which appear−at
(1315, 1008 and 1420–1410 cm−1), respectively. The νs (NO3
)
−
of the unidentate NO3 is markedly shifted to lower frequen-
cies compared to that of the free nitrate (1800–1700 cm−1) [14].
−
In complexes 3, 6, 7, 8, 9, 12 and 13, the NO3 ion behaves
as bidentate ligand. This nitrate possess three non-degenerate
modesofvibrations(ν, νa andνs), whichappearedat1476–1470,
1290 and 1008 cm−1. New bands between 434–498 cm−1 and
3.2.2. TGA and DTA analysis
TGA/DTA studies of the complexes were carried out from 50
to 800 ◦C. Table 5 lists the thermal gravimetric analysis (TGA)

A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
1017
Table 4
1H NMR chemical shifts (δ, ppm) of the Schiff base, H4La and H2Lb, ligands and zinc(II) and cadmium(II) transition metal complexes of H2Lb ligand
Ligand/complex
H4La
Chemical shifts, δ (ppm)
ꢀ
ꢀ
Ha, Ha , Hb and Hb
Hc and Hd
He and Hf
Hg
Hh
1.32 (3H, s), 1.55 (3H, s), 2.44
(3H, s) and 2.74 (3H, s)
2.81 (4H, s) and 3.43 (4H, s)
6.2 (2H, s) and 8.42 (2H, s)
17.3
11.21
H2Lb
1.34 (3H, s) and 2.42 (3H, s)
1.71 (3H, s) and 1.85 (3H, s)
1.92 (3H, s) and 1.97 (3H, s)
2.88 (3H, s) and 3.44 (3H, s)
2.32 (3H, s) and 3.97 (3H, s)
2.07 (3H, s) and 2.23 (3H, s)
6.31 (1H, s) and 8.43 (1H, s)
6.12 (1H, s) and 8.44 (1H, s)
6.12 (1H, s) and 8.45 (1H, s)
17.5
–
–
11.26
11.27
11.26
(12) [Zn2(Lb)(NO3)2(H2O)2]·4H2O
(13) [Cd2(Lb)(NO3)2(H2O)2]·3H2O
data of the complexes of H4La and H2Lb ligands. One of the
features in TGA data concerning the associated water and/or
ethanol molecules within the complexes supports the elemen-
tal analyses [15]. Water and ethanol of crystallization was lost
within the temperature range 80–135 ◦C, whereas the coordi-
nated water molecules were lost within the range 135–220 ◦C.
The following detailed description of the TGA/DTA thermo-
grams of Cu(II) complexes are given as examples and the other
TGA/DTA thermograms were obtained similarly.
3.2.2.1. TGA and DTA of [Cu2(La)]·3H2O (2). The TGA curve
of complex 2, [Cu2(La)]·3H2O, shows that the first stage with
8.79% of the total weight of the complex is due to the removal of
the three lattice water molecules at the range (95–158 ◦C). While

1018
A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
Fig. 5. 1H NMR spectra (δ, ppm) in DMSO-d6, solvent of: (a) Schiff base, H4La, ligand, (b) Schiff base, H4La, ligand after the addition of D2O, (c) Schiff base
H2Lb ligand and (d) Schiff base, H2Lb, ligand after the addition of D2O; (*) suppressed solvent.
the DTA shows that the sharp point at 136 ◦C with endothermic
process which is associated with the loss of water molecules. The
of metal oxide. The thermal decomposition can proceed as
follows:
−3H2O
[Cu2(La)] · 3H2O −→ [Cu2(La)]CH3 C C6H2 C CH3
−→
158–490 ◦C
ꢀ
[CuO(La )CuO]
95–158 ◦C
ꢀ
La
ꢀ
[CuO(La )CuO] −→ 2CuO
550–670 ◦C
second stage (158–490 ◦C) corresponds to the loss of 20.89%
which may be due to the removal of a fragment part of the
ligand. DTA shows that the loss at 235 ◦C with endothermic
process. The last stage (490–670 ◦C), can be ascribed to the
loss of 44.40% of the total weight of the complex which is
due to the decomposition of the complex and formation of cop-
per oxide, which is confirmed by the X-ray powder diffraction.
The residue was 20.70% corresponding to (∼2CuO) (Table 5)
[16]. The DTA curve of the complex shows an exothermic
peak at 515 ◦C, corresponding to the decomposition of anhy-
drous complex through loss of organic molecule and formation
3.2.2.2. TGA and DTA of [Cu2(Lb)(NO3)2(H2O)2]·4H2O (8).
The TGA curve of complex 8, [Cu2(Lb)(NO3)2(H2O)2]·4H2O,
shows that the first stage with 11.33% of the total weight of the
complex is due to the removal of the four lattice water molecules
at the range (113–155 ◦C). While the DTA shows that the sharp
point at 125 ◦C with endothermic process which is associated
with the loss of water molecules, beside an inflection at 179 ◦C
with endothermic process without loss of weight in the TGA
curves. This is may be due to phase transition without weight
loss. The third stage corresponds to the loss of 5.67% which may
be due to the removal of the two coordinated water molecules
Table 5
Thermal gravimetric analysis (TGA) data for transition metal complexes of the H4La and H2Lb ligands
Ligand/complex
M.W.
Weight loss (%) (M.W.)
(A) EtOH/H2O lattice
Residue (%)
%
(B) H2O coord.
(C) NO2
(D) ligand
(1a) [Ni2(La)]·H2O
567.907
740.081
1002.084
613.517
768.369
830.228
970.580
827.443
909.401
635.478
590.268
834.134
612.238
639.183
715.220
3.17 (549.89)
15.96 (621.95)
19.97 (801.94)
8.80 (559.47)
11.99 (676.23)
4.33 (794.20)
18.98 (786.50)
16.70 (689.24)
13.86 (783.30)
11.33 (563.48)
6.10 (554.27)
8.64 (762.07)
11.76 (540.24)
11.26 (567.183)
7.55 (661.22)
–
–
–
70.42 (149.42)
54.12 (149.42)
43.55 (181.42)
65.29 (127.00)
56.53 (149.73)
52.32 (175.69)
44.76 (167.99)
52.50 (162.73)
47.77 (256.80)
43.48 (159.08)
46.81 (149.86)
33.37 (159.27)
42.50 (151.99)
43.23 (162.74)
38.63 (256.80)
26.41
20.19
18.12
20.71
19.51
21.19
17.70
19.69
28.23
25.05
25.41
19.09
24.83
25.47
35.92
2MO
(1b) [Ni2(La)(H2O)4]·EtOH·4H2O
(1c) [Ni2(H4La)(NO3)4]·2EtOH·6H2O
(2) [Cu2(La)]·3H2O
9.73 (549.89)
–
–
–
–
–
–
–
5.67 (527.43)
6.10 (518.21)
–
5.89 (504.15)
5.65 (531.10)
5.04 (625.15)
2MO
2MO2
2MO
2MO
2MO2
2MO2
2MO
2MO
2MO
2MO
M2O3
M2O3
2MO
2MO
18.36 (617.92)
–
(3) [Co2(H2La)(NO3)2]·2EtOH
(4) [Fe2(H2La)(NO3)4]·2H2O
(5) [Cr2(H2La)(NO3)4]·4EtOH
(6) [Zn2(H2La)(NO3)2]·3EtOH
(7) [Cd2(H2La)(NO3)2]·7H2O
(8) [Cu2(Lb)(NO3)2(H2O)2]·4H2O
(9) [Co2(Lb)(NO3)2(H2O)2]·2H2O
(10) [Fe2(H2Lb)(NO3)6]·4H2O
(11) [Cr2(Lb)(NO3)2(H2O)2]·4H2O
(12) [Zn2(Lb)(NO3)2(H2O)2]·4H2O
(13) [Cd2(Lb)(NO3)2(H2O)2]·3H2O
11.97 (584.22)
22.16 (610.18)
18.56 (602.48)
11.11 (597.23)
10.11 (691.29)
14.47 (435.42)
15.58 (426.20)
38.90 (437.62)
15.02 (412.14)
14.39 (439.08)
12.86 (533.13)

A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
1019
Fig. 6. Proposed structure of the binuclear complexes of: (A) H4La ligand and (B) H2Lb ligand.
which is eliminated within the temperature range 158–311 ◦C.
DTA shows that the loss at 240 ◦C with endothermic process.
The fourth stage (311–442 ◦C), can be ascribed to the loss of
14.47% of the total weight of the complex which is due to the
loss of two NO2 molecules. The last stage (442–650 ◦C), can
be ascribed to the loss of 43.48% of the total weight of the
complex which is due to the decomposition of the complex and
formation of copper oxide, which is confirmed by the X-ray
powder diffraction. The residue was 25.05% corresponding to
(∼2CuO) (Table 5) [16]. The DTA curve of the complex shows
an exothermic peak at 550 ◦C, corresponding to the decompo-
sition of anhydrous complex through loss of organic molecule
and formation of metal oxide. The thermal decomposition can
proceed as follows:
−4H2O
−2H2O
[Cu2(Lb)(NO3)2(H2O)2] · 4H2O −→ [Cu2(Lb)(NO3)2(H2O)2] −→ [Cu2(Lb)(NO3)2]
113–155 ◦C
230–311 ◦C
−2NO2
−Lb
[Cu2(Lb)(NO3)2] −→ [CuO(Lb)CuO] −→ 2CuO
394–442 ◦C
510–650 ◦C

1020
A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
are recorded also in Table 4. The d–d transitions of the central
metal ions have lower εmax values than the transition bands of
the ligand. The three bands in all metal complexes located at
230–380 nm region and the shoulder at 390 nm were assigned
3.2.3. Electronic spectra, magnetic moments and molar
conductivity measurements
The d–d transition in the electronic spectral data, measured in
DMF solvent of the Ni(II) and Cu(II), Co(II), Fe(III) and Cr(III)
complexes, is provided in Table 3. The transitions due to the
organic ligands are characterized by their high εmax values and
*
to ␲ → ␲ transitions within the aromatic rings in the ligands.
The absorption band in the range 350–388 nm could be assigned
Fig. 7. Mass fragmentation of the [Ni2(La)(H2O)4]·2EtOH·6H2O complex.

A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
1021
3
to both the C O and C N groups [13]. The bands appeared at
400−425 nm, could be assigned to charge transfer transition
[13].
the T1g(F) spin triplet, thereby allowing the spin-forbidden
transition to gain intensity from the spin-allowed transition.
Another band due to 3T1g(P) ← A2g(F) transition is expected,
3
Electronic spectrum of the Ni(II) (1a) complex showed more
intensedoubletbandsat756and707 nm. Thesebandsweremore
intense than the other electronic spectra of the other Ni(II) Schiff
base complexes under investigation. These bands may be due to
but this is not observed because it is out of the limit of the
instrument, which lies in the near infrared range. The second
main band is overlapped with the n → ␲* band of the ligand
and was not possible to be resolved. The magnetic moment
was measured and showed values at 3.04–3.11 µB, which lie
in the range of octahedral compounds (2.9–3.3 µB). Mass spec-
trum for [Ni(La)(H2O)4]·EtOH·4H2O complex was performed
to determine its molecular weight and fragmentation patterns.
The molecular ion peak was observed at 662 m/e confirming the
formula weight of [Ni(La)(H2O)4]. The schematic fragmenta-
tion of the [Ni(La)(H2O)4]·EtOH·4H2O is depicted in Fig. 7.
Each of the electronic spectra of [Cu2(La)]·3H2O and
[Cu2(Lb)(NO3)2(H2O)2]·4H2O showed one band. The
3
3T1(P) ← T1(F) transition, which could occur in a tetrahedral
d8 arrangement [17,18]. Generally, this band is expected to split
by spin–orbital coupling to an extent which makes unambigu-
ous assignments difficult. The magnetic moment was measured
and equals 3.88 µB, which lie in the range of tetrahedral com-
pounds (3.2–4.1 µB). The electronic spectra of the other Ni(II)
complexes (1b–c), each of them showed the octahedral arrange-
3
3
ment spectra. The main bands due to T2g(F) ← A2g(F) and
3T2g(F) ← A2g(F) transitions. Also, the former band shows a
3
2T2g(G) ← Eg transition in the former complex lies at 590 nm
2
strong shoulder on it. This has been ascribed to the influence
of spin-orbital coupling in “mixing” a spin singlet (1Eg) with
and the latter complex lies at 652 nm. The magnetic moment
Fig. 8. ESR spectra of: (1) [Cu2(La)]·3H2O and (2) [Cu2(Lb)(NO3)2(H2O)2]·4H2O complexes at room temperature.

1022
A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
for the former complex is 2.12 µB, which may be due to
either tetrahedral or square planar structure [17,18]. The
magnetic moment of the latter complex is 1.94 µB which is in
agreement with the value of the octahedral geometry. Besides,
the X-band ESR studies of Cu(II) complexes were recorded in
the solid state at room temperature. [Cu2(La)]·3H2O complex
(µeff = 2.12 µB at room temperature), exhibits one broad band
with geff = 2.1081. The broad band with bad resolution of ESR
spectrum may be due to super exchange interaction between
the two copper ions which lead to a configuration in which the
two electron spins have an antiferromagnetic character, where
the g value and the shape of the spectrum confirm that the
Fig. 9. Mass fragmentation of the [Cu2(Lb)(NO3)2(H2O)2]·4H2O complex.

A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
1023
complex is pseudo tetrahedral geometry [18,19]. On the other
hand, the ESR spectrum of the [Cu2(Lb)(NO3)2(H2O)2]·4H2O
complex, exhibit an intense broad signal, and no obvious
hyperfine splitting. The pattern of geff = 1.9642 for Cu(II)
complex together with the shape of the ESR spectrum indi-
cate the octahedral geometry around the metal ion [19,20].
Fig. 8 shows the ESR spectra of the [Cu2(La)]·3H2O and
[Cu2(Lb)(NO3)2(H2O)2]·4H2O complexes at room temper-
ature. Mass spectrum for [Cu2(Lb)(NO3)2(H2O)2]·4H2O
complex was performed to determine its molecular weight
and fragmentation pattern. The molecular ion peak was
observed at 635 m/e confirming the formula weight of
[Cu2(Lb)(NO3)2(H2O)2]·4H2O. The schematic fragmentation
of the [Cu2(Lb)(NO3)2(H2O)2]·4H2O is depicted in Fig. 9.
The electronic spectra of the Co(II) complexes of H4La and
H2Lb ligands consist of a band in the visible region, often with
other hand, the magnetic moments of Fe(III) complexes were
measured, their values are 5.56 and 5.83 µB, for the two com-
plexes, respectively. These values are too far from its being in
a low spin (t2g5eg ) where the magnetic moment lies closer to
0
2.3 µB. It is expected that the Fe(III) complex is a high spin
octahedral arrangement (t2g3eg ) where the literature magnetic
2
moment values is around 5.92 µB.
Each electronic spectra of the green Cr(III) complexes of
the H4La and H2Lb ligands showed that the complexes are in
octahedral structure. A significant band at 590 and 570 nm,
4
4
respectively, which are due to T2g(F) ← A2g(F) transition
[21]. It is expected that, the spectra show another band due to
4T1g(P) ← A2g(F) transition, but it could be overlapped with
4
the transitions of the ligand in the UV region. The magnetic
moment is expected to be very close to the spin-only value
for three unpaired electrons (3.87 µB) and also because of the
absence of any orbital contribution. In practice, the magnetic
moments in both cases are 3.53 and 3.84 µB, respectively.
Molar conductivities of the complexes were measured in
DMF (10−3 M solution) (see Table 3). The values are in the
range indicating the neutral and ionic complexes. It has been
reported that DMF is a good donor solvent and can be replace
the NO3− from the coordination sphere of the metal complexes
[22]. This leads to the coordinated nitrate ion is exchanged with
the solvent and became free in the solution.
3
a shoulder on the low energy site. Since the 4A2g(F) ← T1g(F)
2
transition is essentially a two electron transition from t2g5eg
to t2g3eg , it is expected to be weak, and the usual assignment
4
4
4
4
4
is a shoulder from A2g(F) ← T1g(F) and T1g(P) ← T1g(F)
transitions [18]. In Co(II) complex of H4La ligand, these bands
are 660 (sh) and 575 nm, while the Co(II) complex of H2Lb
ligand, the bands are 662 (sh) and 578 nm. These transitions
are in agreement with the formation of a high spin octahedral
geometry. Also, the magnetic moment provide a complementary
means of octahedral geometry, the measured magnetic moments
for these complexes are 5.14 and 4.90 µB, respectively, which
lie in the range of octahedral complexes (4.8–5.2 µB).
1
The H NMR spectrum of [Zn2(Lb)(NO3)2(H2O)2]·4H2O
in DMSO-d6 (Table 4) shows signals at δ (ppm) 1.53 (s,
a
b
c
3H, CH3 ); 1.88 (s, 3H, CH3 ); 2.06 (m, 4H, 2CH2 ); 4.06
d
(m, 4H, 2CH2 ); 5.92 (s, 1H, Ar-He); 8.34 (s, 1H, Ar-
The electronic spectra of the Fe(III) complexes of H4La and
H2Lb ligands were observed very weak bands at 447, 557 and
730 nm for the former complex and 525 and 765 nm for the
latter complex. It was not possible to identify the type of d–d
transitions due to strong charge transfer tailing from UV to the
visible region [18]. Generally, from the elemental analysis and
infrared spectra which gives a significant proof for the type of
coordination of the nitrate as unidentate anion, it is expected
that the Fe(III) complexes have octahedral geometry. On the
Hf) and 11.11 (s, 4H, 2NH2). The 1H NMR spectrum of
[Cd2(Lb)(NO3)2(H2O)2]·4H2O in DMSO-d6 (Table 4) shows
a
b
signals at δ (ppm) 1.62 (s, 3H, CH3 ); 2.06 (s, 3H, CH3 );
c
d
2.22 (m, 4H, 2CH2 ); 2.48 (s, 4H, 2CH2 ); 6.13 (s, 1H, Ar-
He); 8.02 (s, 1H, Ar-Hf) and 11.04 (s, 4H, 2NH2) [13]. It is
observed that the signals due to the protons 11.04–11.11 ppm
(2NH2) is completely disappeared on adding D2O while
the other signals still exist at the same positions. Fig. 10
Fig. 10. 1H NMR spectra (δ, ppm) in DMSO-d6 solvent of: (a) [Zn2(Lb)(H2O)2]·4H2O complex, (b) [Zn2(Lb)(H2O)2]·4H2O complex after the addition of D2O, (c)
[Cd2(Lb)(H2O)2]·3H2O complex, and (d) [Cd2(Lb)(H2O)2]·3H2O complex after the addition of D2O; (*) suppressed solvent.

1024
A.A.A. Emara, A.A.A. Abou-Hussen / Spectrochimica Acta Part A 64 (2006) 1010–1024
shows the 1H NMR spectra [Zn2(Lb)(NO3)2(H2O)2]·4H2O and
[Cd2(Lb)(NO3)2(H2O)2]·4H2O complexes in DMSO-d6 before
and after the addition of D2O.
[10] S. Torelli, C. Belle, I. Gautier-Laneau, J.L. Pierre, E. Saint-Aman, J.M.
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