Synthesis and characterization of iron(III), manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of salicylidene-N-anilinoacetohydrazone (H2L1) and 2-hydroxy-1-naphthylidene-N-anilinoacetohydrazone (H2

Article abstract of DOI:10.1016/j.saa.2006.07.052

Salicylidene-N-anilinoacetohydrazone (H₂L¹) and 2-hydroxy-1-naphthylidene-N-anilinoacetohydrazone (H₂L²) and their iron(III), manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes have been sy

Full text of DOI:10.1016/j.saa.2006.07.052

Spectrochimica Acta Part A 67 (2007) 737–743
Synthesis and characterization of iron(III), manganese(II),
cobalt(II), nickel(II), copper(II) and zinc(II) complexes of
salicylidene-N-anilinoacetohydrazone (H2L1) and
2-hydroxy-1-naphthylidene-N-anilinoacetohydrazone (H2L2)
S.A. AbouEl-Enein∗, F.A. El-Saied, T.I. Kasher, A.H. El-Wardany
Department of Chemistry, Faculty of Science, El-Menoufia University, Shebin El-Kom, Egypt
Received 13 February 2006; received in revised form 12 July 2006; accepted 31 July 2006
Abstract
Salicylidene-N-anilinoacetohydrazone (H2L1) and 2-hydroxy-1-naphthylidene-N-anilinoacetohydrazone (H2L2) and their iron(III), man-
ganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes have been synthesized and characterized by IR, electronic spectra, molar
conductivities, magnetic susceptibilities and ESR. Mononuclear complexes are formed with molar ratios of 1:1, 1:2 and 1:3 (M:L). The IR studies
reveal various modes of chelation. The electronic absorption spectra and magnetic susceptibility measurements show that the iron(III), nickel(II)
and cobalt(II) complexes of H2L1 have octahedral geometry. While the cobalt(II) complexes of H2L2 were separated as tetrahedral structure. The
copper(II) complexes have square planar stereochemistry. The ESR parameters of the copper(II) complexes at room temperature were calculated.
The g values for copper(II) complexes proved that the Cu O and Cu N bonds are of high covalency.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Mononuclear complexes; Magnetism; Spectra; Hydrazone shiff bases
1. Introduction
2. Experimental
Acid hydrazides exhibit a broad spectrum of biologi-
cal, bactericidal and fungicidal activities [1,2]. The com-
plexes of hydrazide and other hydrazine derivatives have
great interest due to their analytical, industrial and phar-
macological importance [3,4]. The group 12 metal ions in
concentration less than 10−8 M can be detected and deter-
mined using Ru(II) (di-2-pyridylketone-p-nitrophenyl hydra-
zone [Ru(pby)2(dpknph)]Cl2 [5]. The coordination chemistry of
these ligands is also of interest because they behave differently
toward transition metal ions depending on the reaction condi-
tions and the anions [6]. In this paper, we report the syntheses
as well as magnetic and spectral properties of Fe(III), Mn(II),
Co(II), Ni(II), Cu(II) and Zn(II) complexes of salicylidene-N-
anilinoacetohydrazone (H2L1) and 2-hydroxy-1-naphthylidene-
N-anilinoacetohydrazone (H2L2).
Reagent grade chemicals were used without further purifica-
tion. The hydrazone schiff bases H2L1 and H2L2 were prepared
by adding equimolar amounts of salicylaldehyde or 2-hydroxy-
1-naphthaldehyde to N-anilinoacetylhydrazide in 50 ml absolute
ethanol. The mixture is magnetically stirred and heated for an
hour. The formed solid product was filtered off, washed with
ethanol, crystallized from ethanol and finally dried under vac-
uum over anhydrous CaCl2. The metal complexes were prepared
by stirring magnetically at ca 70 ◦C, the solution of 0.02 mol of
metal salts with 0.02 or 0.04 mol of the appropriate ligand (H2L1
and H2L2) in ca. 50 ml EtOH for a period of hours. The result-
ing solid complexes were filtered off, washed several times with
ethanol and dried under vacuum over P4O10. Elemental anal-
yses (C, H, Cl) were estimated by the microanalytical unit in
CairoUniversity. IRspectrawereperformed asKBrdiscs usinga
Perkin-Elmer 1430 recording spectrophotometer. The electronic
spectra were carried out in N,N1-dimethylformamide (DMF)
solution using a Perkin-Elmer Lambda 4B spectrophotome-
ter. The electron spin resonance spectra (ESR) were recorded
using a varian E104 spectrophotometer and calibrated with
∗
Corresponding author.
E-mail address: dr.saeyda elenein@yahoo.com (S.A. AbouEl-Enein).
1386-1425/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2006.07.052

Table 1
Colour, molar conductivities, molar ratios of preparation (M:L), magnetic moments and elemental analyses of ligands and their metal complexes
No.
Compound
Colour F.W
Salt and molar ratios
of M:L preparation
Found, % (calculated)
ΛMa
μeff, per metal
ion (BM)
C
H
Cl
H2L1C15H15N3O2
Yellow 269.31
Brown 860.91
Orange 591.60
–
67.4 (67.2)
63.3 (63.0)
61.8 (61.1)
5.3 (5.2)
3.7 (4.6)
3.8 (4.4)
–
–
–
–
–
5.60
4.50
1
2
[Fe(HL1)3]C45
H42FeN9O6
FeCl3 (1:1) or (2:1)
Mn(OAc)2 (1:1) or
(2:1)
23.50
17.00
[Mn(HL1)2]C30
H28MnN6O4
3
4
5
6
7
8
9
10
11
12
13
14
[Co(HL1)2]C30H28CoN6O4
Blue 595.54
CoCl2 (1:1)
60.9 (60.7)
55.7 (54.9)
60.4 (60.7)
49.2 (48.5)
55.3 (54.9)
57.1 (57.2)
60.3 (60.7)
44.7 (44.7)
50.6 (50.1)
60.4 (60.3)
44.1 (43.8)
60.9 (60.1)
72.3 (71.5)
66.6 (66.5)
66.9 (66.0)
62.9 (62.3)
66.0 (65.6)
63.9 (64.0)
62.1 (62.4)
58.4 (58.8)
60.4 (60.5)
65.3 (65.2)
51.5 (52.2)
64.4 (65.1)
3.8 (4.4)
4.2 (4.1)
4.5 (4.4)
4.4 (4.8)
4.5 (4.1)
4.8 (4.3)
4.3 (4.4)
3.5 (3.5)
4.3 (4.4)
4.9 (4.4)
3.9 (3.7)
3.5 (4.3)
5.3 (5.3)
4.8 (4.9)
4.9 (4.7)
5.0 (4.5)
4.3 (4.6)
4.4 (4.8)
5.3 (4.96)
3.9 (4.5)
4.7 (5.08)
4.7 (4.6)
4.6 (4.1)
4.9 (5.1)
26.00
33.5
17.80
13.20
30.70
24.0
18.1
24.00
11.8
13.00
24.00
10.3
–
18.7
20.4
34.6
22.0
21.74
24.52
21.30
18.6
13.00
23.00
15.00
3.40
4.30
4.60
4.60
2.70
2.5
3.60
1.63
1.86
2.20
1.60
–
[Co(HL1)(H2L1)(NO3)]C30H29CoN7O7
[Co(HL1)2]C30H28CoN6O4
Brown 658.55
Brown 595.54
Brown 422.19
Green 658.35
Green 681.84
Green 595.33
Brown 403.85
Green 408.84
Green 600.14
Green 393.85
Yellow 601.97
Yellow 319.37
Brown 1029.08
Yellow 691.72
Green 732.16
Brown 695.65
Brown 713.65
Green 731.42
Green 776.37
Orange 833.44
Brown 700.17
Brown 437.23
Yellow 702.09
Co(NO3)2 (1:1)
Co(OAc)2 (2:1)
Co(OAc)2 (1:1)
Ni(NO3)2 (1:1)
NiCl2 (1:1)
Ni(OAc)2 (2:1)
CuCl2 (1:1)
Cu(OAc)2 (1:1)
Cu(OAc)2 (2:1)
Cu(NO3)2 (1:1)
Zn(OAc)2 (2:1)
[Co(HL1)(OAc)(H2O)2]C17
H22CoN3O6
[Ni(HL1)(H2L1)(NO3)]C30H29NiN7O7
[Ni(HL1)(H2L1)Cl]C30H29ClNiN6O4
[Ni(HL1)2]C30H28NiN6O4
–
5.5, 5.6
–
16.7 (17.6)
–
–
–
[Cu(H2L1)Cl2]C30H30Cl2NiN6O4
[Cu(HL1)(OAc)]·H2OC17H19CuN3O5
[Cu(HL1)2]C30H28CuN6O4
[Cu(HL1)NO3]C15H14CuN4O5
[Zn(HL1)2]C30H28ZnN6O4
H2L2C19H17N3O2
–
–
–
15
16
17
18
19
20
21
22
23
24
25
[Fe (HL2)3]·H2OC57H50FeN9O7
FeCl3 (2:1)
Mn(OAc)2 (1:1)
CoCl2 (1:1)
Co(NO3)2 (1:1)
Co(OAc)2 (1:1)
NiCl2 (1:1)
Ni(NO3)2 (1:1)
Ni(OAc)2 (2:1)
CuCl2 (1:1)
6.10
5.50
4.20
3.20
3.80
2.90
3.10
4.10
2.20
–
[Mn(HL2)2]C38H32MnN6O4
[Co(HL2)(H2L2)Cl]C38H33ClCoN6O4
[Co(HL2)2]C38H32CoN6O4
5.0 (4.8)
–
–
[Co(HL2)2]·H2OC38H34CoN6O5
[Ni(HL2)2]·2H2OC38H36NiN6O6
[Ni(HL2)(H2L2)(NO3)]·H2OC38H35NiN7O8
[Ni(H2L2)(OAc)2]·H2OC42H42NiN6O9
[Cu(HL2)2]C38H32CuN6O4
[Zn(HL2)Cl(H2O)]C19H18ClZnN3O3
[Zn(HL2)2]C38H32ZnN3O2
ZnCl2 (1:1)
Zn(OAc)2 (1:1)
–
–
a in ꢀ−1 cm2 mol−1
.

S.A. AbouEl-Enein et al. / Spectrochimica Acta Part A 67 (2007) 737–743
739
Table 2
Infrared spectral bands for the ligands and their metal complexes
No.
Compound
ν(O H)
ν(N H)
ν(C O) ν(C N)
1620
ν(C OH)
δ(O H)
ν(M O) ν(M N) ν(M Cl)
H2L1
3400(br)
3300(s)
3420(s)
3400
3410, 3370(s)
3420
3310, 3270 1680
1275
1145
1145
1155
1145
–
500
525
455
–
435
405
425
420
420
450
–
–
–
–
–
–
-
1
2
3
4
5
6
[Fe(HL1)3]
3130
3150
3200
3170
3200
3220
–
–
–
1620
–
1622, 1603 1275
1620, 1600 1290
1615, 1600 1275
1615, 1605 1275, 1265 1145, 1155 485
1620, 1600 1285
[Mn(HL1)2]
[Co(HL1)2]
[Co(HL1)(H2L1)(NO3)]
[Co(HL1)2]
1150
1150
485
505
[Co(HL1)(OAc)(H2O)2]
3400(br)
–
1615,
1600
1285
7
8
9
10
11
12
13
14
[Ni(HL1)(H2L1)(NO3)]
[Ni(HL1)(H2L1)Cl]
[Ni(HL1)2]
3410, 3370
3410(sh), 3370(s) 3180
3200(br)
1620
1620
–
1615, 1605 1275, 1265 1145, 1155 450
1615, 1605 1275, 1265 1145, 1155 490
1620, 1605 1280
420
420
420
470
475
400
465
420
–
–
355
–
325
–
–
–
–
–
3410
3340
3420a
–
3400
3420
3460(br)
3350
3410
3390
–
3190
3150
3310, 3290 1615
3310, 3250 1620
3200
–
3330, 3290, 1680(s) 1620
3150
3200
3330, 3290 1670
3330, 3290 1670
3290
3150
3200
3200
1155
1155
–
495
495
505
520
515
455
–
[Cu(H2L1)Cl2]
[Cu(HL1)(OAc)]·H2O
[Cu(HL1)2]
1680
1600
1600
1600
1280
–
–
–
[Cu(HL1)(NO3)]
[Zn(HL1)2]
–
–
1605, 1585 1280
1620, 1610 1280
1150
1155
1050
1050
1090
1080
–
H2L2
1205
15
16
17
18
19
20
21
22
23
24
25
[Fe(HL2)3]·H2O
–
–
1623, 1605 1205
1620, 1605 1215
1625, 1605 1205
520
505
525
505
505
510
470
450
425
425
410
425
420
425
425
425
425
–
–
350
–
–
–
–
–
–
[Mn(HL2)2]
[Co(HL2)(H2L2)Cl]
[Co(HL2)2]
1605
–
[Co(HL2)2]·H2O
3350
3400, 3350a
–
–
1620, 1605 1205
1620, 1605 1225
1080
1090
[Ni(HL2)2]·2H2O
[Ni(HL2)(H2L2)(NO3)]·H2O 3380
1620
1618
1620, 1605 1225, 1205 1185, 1080 480
[Ni(H2L2)(OAc)2]·H2O
3420, 3350a
1605
1605
1610
1605
1210
1145
455
500
475
455
[Cu(HL2)2]
–
3330, 3290 1680
3330, 3130 1680
3330, 3290 1620
–
–
–
–
–
–
[Zn(HL2)Cl(H2O)]
[Zn(HL2)2]
3500a
–
350
–
a
ν(H2O).
diphenyl-picrylhydrazide. The 1H NMR spectra were recorded
in deutrated chloroform (CDCl3) using a 300 MHz Varian NMR
spectrophotometer. Magnetic susceptibilities were measured at
27 ◦C using the modified Gouy method with a Jahnson Matthay
balance. The molar conductivity measurements were made in
DMF solution (10−3 M) using a type CD-6N Tacussel conduc-
tometer.
ands show signals within 13.03–11.39, 9.67–8.71, 9.2–7.4 and
7.9–6.95 (multiple signals) ppm range assigned to OH proton
in intramolecular hydrogen bonding OH· · ·N, NH, CH and
aromatic protons, respectively. The spectra of H2L1 and H2L2
display signals at 3.99 and 4.33 ppm due to CH2 protons.
The infrared spectra of ligands (Table 2) reveal bands at
3460–3400; 3330–3310, 3290–3270; 1680; 1620; 1275–1205
and 1145–1080 cm−1, assigned to intramolecular hydrogen
bonded hydroxy group ν(OH· · ·H); ν(NH); ν(C O); ν(C N);
ν(C OH) and δ(O H), respectively. The elemental analyses and
3. Results and discussion
The colours, the metal salts and molar ratios of preparation,
molar conductivities, stoichiometries, and elemental analyses
of the prepared complexes are listed in Table 1. The analyti-
cal data show that the reaction of ligands with different salts;
Fe(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) ions in differ-
ent appropriate molar ratios give mononuclear complexes with
different stoichiometries 1:1, 1:2 and 1:3 (M:L). The 1:1 and
1:2 molar ratio reactions of iron(III) chloride with the ligands
separate the complex [Fe (HL)3]·nH2O. The elemental analy-
ses support the formation of metal complexes represented in
Table 1. These air stable metal complexes are non-hygroscopic,
partially soluble in most organic solvents but freely soluble in
DMF and DMSO. The molar conductivities in DMF (10−3 M)
solution show that the complexes behave as non-electrolytes,
1
indicating coordination of anions [7]. The H NMR spectra
of H2L1 and H2L2 ligands have been carried out in deutrated
chloroform (CDCl3) at room temperature. The spectra of lig-
Fig. 1. The chemical structure for H2L1 and H2L2.

740
S.A. AbouEl-Enein et al. / Spectrochimica Acta Part A 67 (2007) 737–743
Table 3
Solution (DMF) electronic spectra (cm−1) of the ligands and their metal complexes
Compound
Intraligand and charge transfer bands
d–d bands
H2L1
35,020
34,650
29,410
30,420
27,240
29,850
[Fe(HL1)3]
24,630
23,809
25,000
23,760
23,620
24,210
23,940
24,100
23,970
23,980
24,220
23,950
24,390
19,940
19,230
20,200
16,950
17,100
17,240
16,420
16,540
16,620
15,560
14,970
15,950
15,500
15,600
17,857
15,480
14,650
14,920
14,870
[Mn(HL1)2]
[Co(HL1)2]
[Co(HL1)(H2L1)(NO3)]
[Co(HL1)2]
34,910
34,970
34,840
34,960
33,740
34,150
33,780
34,120
34,950
33,740
34,540
34,840
34,620
31,060
30,600
29,720
30,100
29,870
30,200
30,150
30,100
30,240
30,760
30,660
30,120
29,850
29,940
29,640
28,780
29,650
28,800
28,750
29,940
29,870
29,920
29,740
28,760
27,170
29,410
[Co(HL1)(OAc)(H2O)2]
[Ni(HL1)(H2L1)(NO3)]
[Ni(HL1)(H2L1)Cl]
[Ni(HL1)2]
[Cu(H2L1)Cl2]
[Cu(HL1)(OAc)]·H2O
[Cu(HL1)2]
[Cu(HL1)(NO3)]
H2L2
[Fe(HL2)3]·H2O
22,730
23,809
23,420
24,680
23,950
23,750
23,780
24,120
23,780
20,000
20,325
19,940
19,870
20,420
15,390
16,325
14,980
14,870
15,200
16,430
16,520
16,500
14,980
[Mn(HL2)2]
[Co(HL2)(H2L2)Cl]
[Co(HL2)2]
33,970
34,480
34,200
33,500
34,220
33,970
34,150
31,220
30,970
31,420
30,790
29,920
29,780
29,970
30,400
29,960
30,650
29,870
30,140
30,170
30,120
[Co(HL2)2]·H2O
[Ni(HL2)2]·2H2O
[Ni(HL2)(H2L2)(NO3)]·H2O
[Ni(H2L2)(OAc)2]·H2O
[Cu(HL2)2]
spectral data for H2L1 and H2L2 verified the structure shown in
Fig. 1.
The IR spectra of complexes 4, 7, 8 and 21 show bands cor-
responding to coordinated and uncoordinated hydroxy group,
coordinated carbonyl oxygen, coordinated azomethine nitrogen
and HC N N C O. This can only achieved when the metal
ion combines with a neutral and anionic ligands, the anionic one
behaves as a monoanionic tridentate ligand and coordinates via
theprotonatedphenolicoxygen, deprotonatedenolicoxygenand
the azomethine nitrogen. The neutral one behaves as a bidentate
one and coordinates via the azomethine nitrogen and carbonyl
oxygen atom. The IR spectra of complexes 18, 23 and 24 show
that the bands corresponding to OH frequencies disappear upon
coordination, the ν(C N) appears at lower frequency compared
to those of the free ligands and the νC O) does not show any
shift because it does not participate in coordination. This reveals
that the ligands behave as a monoanionic bidentate one and coor-
dinate via the azomethine nitrogen and deprotonated phenolic
oxygen atom. The IR spectrum of complex 10 shows the band
corresponding to ν(C N) at lower frequency compared to that of
the ligand. The frequencies of phenolic OH group display shift
to lower or higher frequencies. The ν(C O) appears at the same
frequency compared to that of the free ligand. This may be con-
sidered as evidence that the ligand behaves as a neutral bidentate
The most important IR spectral bands of metal complexes
are listed in Table 2. The IR spectra of complexes 1, 2, 3, 5, 6,
9, 13, 14, 15, 16, 19 and 20 reveal that, the ν(C N) shows a
shift to lower frequency ca.15 cm−1 compared to those of the
free ligands, indicating that the azomethine nitrogen involved
in coordination. The spectra of these metal complexes show
also that the ν(C O) disappears upon coordination and a new
band appears at 1620 cm−1, assigned to ν(N N C O), indi-
cating that the ligands in these complexes coordinate in their
enol-form via the enolic oxygen atom. The ν( OH), ν(C OH)
and δ( O H) bands in the spectra of this group of complexes
except 1, 3, 15 and 19 display a shift to lower or higher fre-
quencies, indicating that the O H group coordinated without
a deprotonation. The above arguments and elemental analyses
indicate that the ligands behave as tridentate monobasic ligands
and coordination occurs via the azomethine nitrogen, deproto-
nated enolic oxygen and the hydroxy oxygen atom. Whereas in
case of complexes 1, 3, 15 and 19, the OH frequencies appear
at the same positions as those of the free ligands, indicates
that the OH group does not participate in coordination. The
ligands in these complexes (1, 3, 15, 19) react with the metal
ion as a monobasic bidentate ligands. The coordinations occur
via the azomethine nitrogen and enolic oxygen atom. The IR
spectra of complexes, 11, 12 and 25 show that the ν(C O) and
ν(C N) bands shift to lower frequencies compared to those of
the free ligands, indicates the involvement of the azomethine
nitrogen and the carbonyl oxygen in coordination. The spectra
also show that the frequencies of OH group disappear, indi-
cating the deprotonation of the OH group upon coordination.
Table 4
Solid state ESR spectral parameters of the copper(II) complexes
Compound
g11
g1
gav or giso
[Cu(H2L1)Cl2]
[Cu(HL1)(OAc)]·H2O
[Cu(HL1)(NO3)]
[Cu(HL2)2]
2.125
2.116
2.114
2.113
2.223
2.059

S.A. AbouEl-Enein et al. / Spectrochimica Acta Part A 67 (2007) 737–743
741
one and coordinates via the azomethine nitrogen and protonated
phenolic oxygen atom. The IR spectrum of complex 17 shows
bands corresponding to ν(C O), ν(OH), ν(C OH) and δ(OH)
at the same frequencies as that of the free ligand. The spec-
trum also shows two bands at 1625 and 1602 cm−1, assigned to
ν( N N C O) and ν(C N), respectively. This would be ful-
filled if Co(II) bonded with two ligand molecules one of them
behaves as a monoanionic bidentate and coordinates via the
azomethine nitrogen and deprotonated enolic oxygen atom and
the second molecule of ligand behaves as a neutral monodentate
coordinating through the azomethine nitrogen. The fourth coor-
dination site is achieved by a chloride atom. The IR spectrum
of complex 22 shows that the ligand in this complex behaves
as a neutral bidentate ligand and coordination takes place via
the azomethine nitrogen and the carbonyl oxygen atom. This is
evidenced by the appearance of ν(C O) and ν(C N) at lower
frequencies compared to that of the free ligand and the bands due
to hydroxy group appear at the same positions as that of the free
ligand.
The IR spectra of all metal complexes show two new bands
at 525–450 and 475–400 cm−1, assigned to ν(M O) [8] and
ν(M N) [8,9], respectively. The IR spectra of chloro complexes
display an additional new band at 355–325 cm−1, assigned to
ν(M Cl) [10,11]. The IR spectra of the acetato complexes
exhibit the νasym(COO−) and νsym(COO−) near 1570 and
1390 cm−1, respectively, which is consistent with monodentate
acetate coordination [12]. The IR spectra of nitrate-complexes
show two strong bands at 1385 and 1285 cm−1 assigned to
νasym(NO3−) and νsym(NO3−), respectively, indicate the pres-
ence of a terminally bonded monodentate nitrate group [13,14].
4. Magnetic and electronic spectral studies
Solution spectral data (DMF) of H2L1 and H2L2 ligands
and their metal complexes as well as d–d bands in solution
are represented in Table 3. H2L1 and H2L2 exhibit, a band at
35,020 and 43,840 cm−1, respectively, assignable to phenyl ring
*
transition ␲–␲ which remain nearly unchanged in the spectra
Scheme 1. Chemical formulae of the solid complexes.

742
S.A. AbouEl-Enein et al. / Spectrochimica Acta Part A 67 (2007) 737–743
Scheme 1. (Continued ).
4
and 4T1g → T1g (p) (ν3) transition, indicated to an octahedral
stereochemistry around cobalt [12]. The calculated values of Dq,
B, β and ν2/ν1 lie in the same range reported for an octahedral
structure. Also, the values of magnetic moments (4.3–4.6 BM)
are in good agreement with those reported for the octahedral
structure [6]. However, the cobalt(II) separated from H2L2 lig-
of their metal complexes. The ligands show bands in range
*
24,410–30,120 and 27,170–27,240 cm−1, due to n–␲ transi-
tion which shifted to higher energy on complexation.
The electronic spectra of Mn(II) complexes 2 and 16
in DMF solution display bands 16,949–17,857 and 19,230–
20,325 cm−1. These bands assigned to octahedral geometry
around Mn(II). The lower magnetic moment value 4.5–5.5 BM
may be due to the presence of equilibrium between high and low
spin state together with metal–metal interaction [2,9].
and exhibit one main band at ca 15,500 cm−1 due to 4A2 → T1
4
(P) transition (ν3) in tetrahedral ligand field, there is also a shoul-
der at about 20,000 cm−1 due to spin–orbital coupling. Also, the
values of μeff (4.2–3.2 BM) is an additional evidence for tetra-
hedral geometry [8].
The electronic spectral data of [Fe(HL1)3] and [Fe(HL2)3]·
H2O in DMF solution show bands at 19,940 and 15,600 cm−1
4
which arises from 6A1g to 4T1g and 6A1g → T2g transitions in
The nickel complexes were found to be paramagnetic which
excludes the possibility of square planar configuration. The mea-
sured magnetic moment values for all nickel(II) complexes,
2.5–4.1 BM, fall in the range reported for both octahedral
and/or tetrahedral structures. The spectra of the nickel(II) com-
plexes, Table 3, show one absorption band at ca. 16,500 cm−1
octahedral structures. The values of μeff per iron(III) atom 5.6
and 6.1 BM, respectively, are compatible with high-spin octahe-
dral iron(III) complexes [2,15].
The electronic spectra of cobalt(II) complexes derived
from H2L1 show two broad bands in the 14,500–15,000 and
4
4
16,600–17,300 cm−1 regions assignable to T1g → A2g (ν2)
3
3
which is considered to be due to A2g (F) → T1g (F) tran-

S.A. AbouEl-Enein et al. / Spectrochimica Acta Part A 67 (2007) 737–743
743
sition of six coordinated nickel(II) complexes [16,17]. The
Kivelson and Neiman [20] have suggested that the g11 value
in the Cu(II) complex can be used as a measure of covalent
character of the metal–ligand bond. For the ionic environment,
the g11 value is normally 2.3 or higher and for the covalent
environment, it is less than 2.3. Using this criterion, the data
show considerable covalent character of the metal–ligand bond
in the present complexes.
3
3
ν3{ A2g (F) → T1g (P)} band expected in the range of
26,000–28,000 cm−1. The calculated value of ν2/ν1 at about
1.7 which is consistent with an octahedral configuration [18].
These assigned energies were used to calculate the spec-
tral parameters Dq = ca. 1015, B = ca. 920 and β = 0.82 [18].
These values agree well with those reported for octahedral
nickel(II) complexes. The value of the nephelauxetic parameter,
B, indicate the covalent character of the metal–ligand bond is
low.
Based on the above arguments the chemical structures of the
complexes are shown in Scheme 1.
The magnetic moment values of the copper(II) complexes
under study (Table 3), lie in the range observed for Cu(II)
complexes with one unpaired spin (∼1.73 BM). The electronic
spectra of copper(II) complexes give one broad band with a max-
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2
imum in the 15,000–16,000 cm−1 range due to the 2B1g → A1g
transition in a square planar geometry [8].
5. Electron spin resonance spectroscopy (ESR)
The powder ESR parameters of the copper(II) complexes
measured at room temperature are collected in Table 4. The
ESR spectra of [Cu(H2L1)Cl2] and [Cu(HL1)(OAc)]·H2O and
[Cu(HL2)2] complexes display only one broad signal with no
appearance of hyperfine structure. The broad universal spectral
signal could be attributed to super exchange interaction between
copper centers in the solid state [19]. The inhomogeneity of the
signals is due to the anisotropic exchange interaction. These
spectral features are consistent with the magnetic data for these
complexes. The spectrum of [Cu(HL1)(NO3)] is anisotropic
with a parallel and perpendicular spin being assignable. The
low g-value of complex [Cu (HL2)2], indicating more covalent
planar bonding and two ligands are likely bidentate, N, O, donor.
From the observed g-values, it is clear that the unpaired elec-
2
tron lies predominantly in the dx2–y2 and implying a B1g as
a ground state. The g-value for copper(II) complexes is greater
than 2 indicating to the presence of Cu O and Cu N bonds in
these chelates.
[18] A.B.P. Lever, Coord. Chem. Rev. 3 (1986) 119.
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