Synthesis, spectroscopic, magnetic and thermal properties of copper(II), nickel(II) and iron(II) complexes with some tetradentate ligands: Solvatochromism of iron(II)-L2

Article abstract of DOI:10.1016/j.ica.2012.05.006

The tetradentate azomethines were prepared by condensation of 2-piperazin-1-ylethanamine, (3-morpholin-4-ylpropyl)amine with 3-methylthophene-2-carbaldehyde, salicylaldehyde and 1H-imidazole-5- carbaldehyde. The ligands were characterized based on mass, <

Full text of DOI:10.1016/j.ica.2012.05.006

Inorganica Chimica Acta 391 (2012) 28–35
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, spectroscopic, magnetic and thermal properties of copper(II),
nickel(II) and iron(II) complexes with some tetradentate ligands:
Solvatochromism of iron(II)–L2
Alper Onder a, Murat Turkyilmaz b, Yakup Baran a,
⇑
a Onsekiz Mart University, Art and Science Faculty, Department of Chemistry, Canakkale 17100, Turkey
b Trakya University, Science Faculty, Department of Chemistry, Edirne, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
The tetradentate azomethines were prepared by condensation of 2-piperazin-1-ylethanamine, (3-mor-
pholin-4-ylpropyl)amine with 3-methylthophene-2-carbaldehyde, salicylaldehyde and 1H-imidazole-
5-carbaldehyde. The ligands were characterized based on mass, 1H and 13C NMR, FTIR, and elemental
analyses. New complexes of ligands with copper(II), iron(II) and nickel(II) were synthesized. Metal com-
plexes are reported and characterized by magnetic, conductivity measurements, FTIR, elemental and
thermal analyses (TG–DTA). Spectral analyses show that all the ligands behave as neutral tetradentate
ligands and bind to the metal via azomethine N, piperazine N, salicylaldehyde O, morpholine O, imidazole
N and thiophene S. Results of magnetic measurements and thermal studies show that the geometrical
structures of the nickel(II) complexes are square planar while copper(II) and iron(II) are octahedral.
The thermal behaviors of these complexes show that the hydrated complexes lose the hydration water
molecule in the first step, followed immediately by decomposition of the anion and ligand molecules
in subsequent steps. The solvatochromic behavior of the iron(II)–L2 complex was investigated using
the electronic spectra of 1 Â 10À3 M in four different solvents. The solvatochromism was explained in
terms of MLCT transition and solvent characteristics such as polarity, nature and acceptor–donor
properties.
Received 10 February 2012
Received in revised form 27 April 2012
Accepted 10 May 2012
Available online 19 May 2012
Keywords:
Azomethines
Thermal stability
Spectroscopic
Solvatochromism
Complexes
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
and xanthine have been studied [15,16]. Azomethine metal com-
plexes are also a focus for scientific interest, due to their important
The synthesis of a new ligand is the most important step in the
development of metal complexes with unique properties and novel
reactivity. Four tetradentate azomethines were prepared. L3 and L4
are new and L2 is patented [1]. L1 was prepared and its cadmium(II)
and nickel(II) complexes were reported. These are X-ray structure
reports and solution equilibrium respectively. Azomethines can be
considered an important class of organic compounds which are
good chelating agents because of the presence of both hard nitro-
gen and oxygen, and soft sulfur donor atoms in the backbones of
these ligands [2]. Tetradentate azomethines, with N2O2 donor sets
resulting from the condensation of aliphatic diamines, have been
extensively studied [3–6]. Azomethine complexes are studied for
their antitumor, antimicrobial, antiviral, catalytic, enzymatic and
mesogenic characteristics [7–13]. Nickel–L1 complex has been
studied for planar-octahedral equilibrium in solution [14]. Synthe-
sis, crystal structure, and magnetic properties of copper–L2 were
studied. The inhibitory bioactivities of nickel–L2 against urease
role in biological systems, and represent an interesting model for
metalloenzymes which efficiently catalyze the reduction of oxy-
gen. Thermal decomposition of the metal complexes is used to in-
fer the structures of the metal complexes together with the other
spectroscopic and elemental analysis data [17–19]. Salicylaldehyde
derivatives of azomethine compounds show a variety of biological
activities, such as antibacterial activity [20]. The electronic spectra
of the inorganic compounds can be affected by solvents. These
complexes are usually referred to as solvatochromic substances
and recent papers indicate continuing interest in this field [21–
25]. The solutions of [FeL2Cl2] range in color from yellow to purple
in solvents. These colors are due to intense charge transfer bands
involving electron transfer from the metal t2g orbital in low spin
d6 to low lying p⁄ orbital in the azomethine. This color change
occurs without any structural change in the chromophor. This is
where the MLCT transition between iron(II) and azomethine takes
place. Stronger acceptor properties of the solvent leads to a greater
MLCT blue shift observed.
This work deals with the synthesis, characterization and
thermal behavior of new tetradentate azomethine complexes of
⇑
Corresponding author. Tel.: +90 286 2180018; fax: +90 286 2180533.
E-mail address: yakupbaran@yahoo.com (Y. Baran).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.05.006

A. Onder et al. / Inorganica Chimica Acta 391 (2012) 28–35
29
copper(II), nickel(II) and iron(II). Iron(II)–L2 exhibits significant sol-
vatochromic band shifts in certain solutions. In this paper we re-
port the coordination behavior of azomethines toward these
metal ions, thermal properties, spectroscopic properties of ligand
and complexes, conductivity and solvatochromism of iron(II)–L2.
piperazin); 51.61(CH2 aliphatic). GS–MS (m/z): 234.05 [M+H]+ cal-
culated 233.31. FTIR (KBr, cmÀ1): 3356 (OH), 1632 (C@N).
2.3.2. L2, 2-{(E)-[(3-morpholin-4-ylpropyl) imino]methyl}phenol
Anal. Calc. for C14H20N2O2 (248.32): C, 67.72; H, 8.21; N, 11.33.
Found: C, 67.77; H, 8.33; N, 11.40%. 1H NMR (300 MHz, CDCl3) d
ppm: 8.34 (s, imine); 7.29 (d, H, J = 3 Hz); 7.19 (d, H, J = 3 Hz);
6.83 (double t, 2H, J = 6 Hz); 3.73 (t, 4H, (morpholine, OCH2)
J = 9 Hz); 2.88 (t, 4H, J = 6 Hz); 2.67 (t, 2H, J = 6 Hz); 2.49 (t, 2H,
J = 6 Hz) 13C (CDCl3) d ppm: 178.79 (C@N); 165.25 (C–OH);
161.46; 132.37; 131.36; 118.71; 117.21 (all aromatics), 67.18 (O–
CH2, 2C, morpholine); 57.57 (C, aliphatic); 56.52(N–CH2, 2C, mor-
pholine); 53.90 (CH2, aliphatic); 27.80 (CH2–CH2–CH2–). GS–MS
(m/z): 249.00 [M+H]+ calculated 248.32. FTIR (KBr, cmÀ1): 3343
(OH), 1633 (C@N).
2. Experimental
2.1. Materials
All chemicals used in this study were chemically pure (Aldrich).
They were used without further purification. The organic solvent
(methanol) was spectroscopic grade and all reactions were per-
formed under argon atmosphere.
2.3.3. L3, [(1E)-(3-methyl-2-thienyl)methylene](2-piperazin-1-
ylethyl) amine
2.2. Physical measurements
Anal. Calc. for C12H19N3S (237.37): C, 60.71; H, 8.01; N, 17.74.
Found: C, 60.55; H, 8.14; N, 17.71. 1H NMR (300 MHz, CDCl3) d
ppm: 8.41 (s, H, imine); 7.25 (d, H, aromatic, J = 3 Hz); 6.81 (d, H,
aromatic, J = 6 Hz); 3.69 (t, 2H piperazine, J = 9 Hz); 2.85 (t, 4H ali-
phatic + piperazine, J = 6 Hz); 2.63 (t, 2H, aliphatic, J = 9 Hz); 2.48(s,
3H, CH3); 2.33(t, 4H piperazine), J = 6 Hz). 13C (CDCl3) d ppm:
178.67 (C@N); 154.30; 140.29; 130.88; 128.14 (aromatics);
59.77; 58.63 (N–CH2, 2C, piperazine); 55.04; 46.27 (NH–CH2, 2C,
piperazine); 14.04 (CH3). GS–MS (m/z): 237.99 [M+H]+ calculated
237.37. FTIR (KBr, cmÀ1): 1627 (C@N).
The FTIR spectra of all ligands, which were obtained as oils,
were recorded between KBr disks with a Perkin Elmer BXII FTIR
spectrophotometer in wavenumbers of 4000–400 cmÀ1. A small
drop of the compound was placed on one of the potassium bro-
mide plates and the second plate was placed on top and a quarter
turn made to obtain a nice even film. The complexes were recorded
by applying the KBr disc technique. 1H and 13C NMR spectra of the
ligands were measured with a Varian 300 MHz spectrometer in
CDCl3 and CD3OH, and chemical shifts are indicated in ppm relative
to the solvent peak. The elemental analyses for the compounds
were carried out using a Perkin Elmer PE 2400 C H N elemental
analyzer. The mass spectra of the azomethines were measured by
the EI technique on a Thermo Finnigan Trace DSQ spectrometer.
Thermal stabilities of the complexes were examined using a Seiko
SII TG–DTA 6300 thermal analyzer. The mass loss was measured
from 25 up to 1200 °C at a heating rate of 15 °C minÀ1 in dynamic
nitrogen atmosphere. The molar magnetic susceptibilities of the
complexes were measured from a powdered sample at room tem-
perature using a Sherwood Scientific Magnetic Susceptibility Bal-
ance. Metal analysis was carried out on a Perkin-Elmer 238 AAS.
The effective magnetic moments were calculated as BM. The elec-
tronic spectra of the ligands and complexes were measured by an
Agilent HP 8453 Diode Array UV–Vis spectrophotometer. The con-
ductivity measurement was performed by a WTW inolab 720 con-
ductometer. The residues of the TG–DTA study were analyzed by a
Bruker D2 Phaser XRD.
2.3.4. L4, [(1E)-1H-imidazol-5-ylmethylene](2-piperazin-1-ylethyl)
amine
Anal. Calc. for C10H17N5 (207.28): C, 58.03; H, 8.22; N, 33.82.
Found: C, 57.91; H, 8.13; N, 33.77%. 1H NMR (300 MHz, CDCl3) d
ppm: 8.17 (s, H imine); 7.65 (s, H aromatic) 7.34 (s, H aromatic);
3.70 (double t, 4H aliphatic + piperazine, J = 9 Hz); 2.88 (quartet,
t, 8H aliphatic + piperazine J = 6 Hz). 13C (CDCl3) d ppm: 178.79
(C@N); 152.90; 114.89; 109.81 (aromatics); 60.07; 57.91 (N–CH2,
2C); 54.96; 46.16 (NH–CH2, 2C). GS–MS (m/z): 208.05 [M+H]+ cal-
culated 207.28. FTIR (KBr, cmÀ1): 1632 (C@N).
2.4. Synthesis of the complexes
All the complexes were prepared by the same procedure as fol-
lows: 8 mmol metal chloride was dissolved in 50 mL argon satu-
rated hot water–methanol mixture and the solution of
azomethine 8 mmol in hot methanol was added slowly and stirred
at 50 °C for 5 h to yield the azomethine metal complex, ML, as a
precipitate. The precipitate was filtered and washed with cold eth-
anol several times. The solid was dried in vacuum desiccators and
subjected to FTIR, UV–Vis and elemental analysis.
2.3. Synthesis of the azomethines
All the tetradentate unsymmetrical azomethines were prepared
by a similar method.
A solution of 15 mmol amine was dissolved in 50 mL methanol
and 15 mmol aldehyde, dissolved in 40 mL methanol, was added to
the amine solution on a magnetic stirrer at room temperature for
10 min then stirred for 4 h at 50 °C. The colored solution was con-
centrated in a rotary evaporator which produced a viscous oil. All
the substances were checked for purity by thin layer chromatogra-
phy and then loaded into a silica column for purification.
2.4.1. Nickel–L1 chloride tetrahydrate
Yield: 67%. FTIR (KBr, cmÀ1): 3367, 3033, 1627, 561 (MÀN), 572
(MÀO). UV–Vis (H2O, nm; (
e
, MÀ1 cmÀ1)): 352(1466), 481(566).
Anal. Calc. for C13H27N3O4Cl2Ni: C, 35.92; H, 6.12; N, 9.73. Found:
C, 35.78; H, 5.83, N, 9.68%.
2.4.2. Iron–L1 chloride monohydrate
2.3.1. L1, 2-{(E)-[(2-piperazin-1-ylethyl) imino] methyl}phenol
Anal. Calc. for C13H19N3O (233.31): C, 66.71; H, 8.29; N, 18.09.
Found: C, 66.54; H, 8.33; N, 18.13%. 1H NMR (300 MHz, CDCl3) d
ppm: 8.30 (s, H, imine); 7.25 (d, H, J = 3 Hz); 7.21 (d, H, J = 3 Hz);
6.86 (double t, H, J = 6 Hz); 3.67 (t, 6H, J = 9 Hz); 2.39 (t, 6H,
J = 6 Hz). 13C (CDCl3) d ppm: 180.49 (C@N); 166.02 (C–OH);
161.37, 132.60; 131.52; 118.84; 117.26 (all aromatics), 58.67 (N–
CH2, 2C piperazin); 56.94(CH2 aliphatic); 53.61 (HN–CH2, 2C,
Yield: 66%. FTIR (KBr, cmÀ1): 3399, 3049, 1611, 542 (MÀN), 566
(MÀO). UV–Vis (H2O, nm; (
e
, MÀ1 cmÀ1)): 316(1334), 438(388).
Anal. Calc. for C13H21N3O2Cl2Fe: C, 41.42; H, 5.42; N, 11.14. Found:
C, 41.34; H, 5.33; N, 11.20%.
2.4.3. Copper–L1 chloride monohydrate
Yield: 81%. FTIR (KBr, cmÀ1): 3435, 3022, 1635, 509 (MÀN), 521
(MÀO). UV–Vis (H2O, nm; (
e
, MÀ1cmÀ1)): 357(1240), 641(520).

30
A. Onder et al. / Inorganica Chimica Acta 391 (2012) 28–35
Anal. Calc. for C13H21N3O2Cl2Cu: C, 40.52; H, 5.21; N, 10.94. Found:
C, 40.45; H, 5.27; N, 11.11%. Paramagnetic with 1.81 BM.
2.4.7. Iron–L3 chloride monohydrate
Yield: 53%. FTIR (KBr, cmÀ1): 3019, 1629, 507 (MÀN). UV–Vis
(H2O, nm; (e
, MÀ1 cmÀ1)): 366(1277), 482(388). Anal. Calc. for
C
12H21N3OSCl2Fe: C, 37.82; H, 5.33; N, 11.04. Found: C, 37.73; H,
2.4.4. Nickel–L2 chloride dihydrate
5.23; N 11.20%.
Yield: 47%. FTIR (KBr, cmÀ1): 3367, 3010, 1628, 537 (MÀN), 544
(MÀO). UV–Vis (H2O, nm; (
e
, MÀ1 cmÀ1)): 385(1355), 476(488).
Anal. Calc. for C14H24N2O4Cl2Ni: C, 38.83; H, 5.38; N, 7.04. Found:
2.4.8. Copper–L3 chloride dihydrate
C, 38.74; H, 5.44; N, 6.94%.
Yield: 67%. FTIR (KBr, cmÀ1): 3021, 1652, 510 (MÀN). UV–Vis
(H2O, nm; (e
, MÀ1 cmÀ1)): 281(1322), 510(411). Anal. Calc. for
C
12H23N3O2SCl2Cu: C, 35.42; H, 5.40; N, 10.33. Found: C, 35.29;
2.4.5. Iron–L2 chloride dihydrate
H, 5.34; N, 10.40%. Paramagnetic with 1.96 BM.
Yield: 61%. FTIR (KBr, cmÀ1): 3399, 3025, 1613, 543 (MÀN), 557
(MÀO). UV–Vis (H2O, nm; (
e
, MÀ1 cmÀ1)): 315(1223), 391(401).
Anal. Calc. for C14H24N2O4Cl2Fe: C, 39.32; H, 5.61; N, 7.02. Found:
2.4.9. Nickel–L4 chloride pentahydrate
C, 39.17; H, 5.52; N, 7.10%.
Yield: 67%. FTIR (KBr, cmÀ1): 3035, 1627, 524 (MÀN). UV–Vis
(H2O, nm; (e
, MÀ1 cmÀ1)): 260(1221), 484(377). Anal. Calc. for
C
10H27N5O5Cl2Ni: C, 28.13; H, 5.90; N, 16.53. Found: C, 28.06; H,
2.4.6. Copper–L2 chloride monohydrate
5.82; N, 16.50%.
Yield: 68%. FTIR (KBr, cmÀ1): 3354, 3019, 1640, 556 (MÀN),
568(MÀO). UV–Vis (H2O, nm;
(
e,
MÀ1 cmÀ1)): 355(1113),
556(396). Anal. Calc. for C14H22N2O3Cl2Cu: C, 38.42; H, 5.29; N,
6.93. Found: C, 38.35; H, 5.37; N, 6.96%. Paramagnetic with 1.62
BM.
2.4.10. Iron–L4 chloride monohydrate
Yield: 67%. FTIR (KBr, cmÀ1): 3031, 1629, 535 (MÀN). UV–Vis
(H2O, nm; (e
, MÀ1 cmÀ1)): 345(1123), 485(298). Anal. Calc. for
N
N
N
N
S
N
O
N
O
N
N
O
N
H
NH
N
H
HN
H C
3
H
H
N
L1
L2
L3
L4
Scheme 1. Structures of the ligands.
N
N
N
N
O
N
N
N
O
N
O
Ni
Ni
Ni
N
H
H
H
N
N
[NiL1]Cl2
[NiL2]Cl2
[NiL4]Cl2
Cl
Cl
Cl
Fe
Cl
N
N
N
N
S
Cl
Fe
Cl
N
O
N
O
N
O
N
Fe
Cl
Fe
Cl
N
H
N
H
N
H C
3
H
H
N
[FeL1Cl2]
[FeL2 Cl2 ]
[FeL3Cl2]
[FeL4Cl2]
Cl
Cl
Cl
N
N
S
N
N
N
N
O
N
Cl
N
N
N
O
Cu
Cl
Cu
Cl
Cu
Cl
Cu
Cl
N
H
N
H
O
H C
3
H
H
N
[CuL1Cl2]
[CuL2Cl2 ]
[CuL3Cl2]
[CuL4 Cl2]
Scheme 2. Proposed structures of the complexes.

A. Onder et al. / Inorganica Chimica Acta 391 (2012) 28–35
31
80.0
75
70
65
60
55
50
45
2604.89
2930.12
3399.49
2684.40 2606.44
3056.62
2925.57
40
35
30
25
20
15
10
5
%T
3444.91
2863.73
2609.01
2686.87
2930.56
3367.22
1613.57
1640.37
2949.84
2853.54
1628.40
L2 : ----------
NiL2 : ----------
FeL2 : ----------
2810.13
1633.58
CuL2 : ----------
0.0
4000.0
3600
3200
2800
2400
cm-1
2000
1800
1600
1400.0
Fig. 1. FTIR spectra of the Ni(II), Fe(II) and Cu(II) complexes of L2.
Fig. 2. TG curves of the Cu(II) complexes of L1, L2, L3 and L4.
Fig. 4. TG curves of the Ni(II) complexes of L1, L2, L3 and L4.
C10H19N5OCl2Fe: C, 34.33; H, 4.93; N, 20.04. Found: C, 34.21; H,
4.93; N, 20.13%.
2.4.11. Copper–L4 chloride trihydrate
Yield: 67%. FTIR (KBr, cmÀ1): 3024, 1623, 518 (MÀN). Anal. Calc.
for C10H23N5O3Cl2Cu: C, 30.34; H, 5.92; N, 17.73. Found: C, 30.37;
H, 5.86; N, 17.75%. Paramagnetic with 1.55 BM.
3. Result and discussion
3.1. Elemental analysis of the complexes
The results of the elemental analyses are consistent with the re-
sults calculated from the empirical formulae of each compound.
The structures of the ligands and their complexes are given in
Schemes 1 and 2. The chloride salts of the metal were used in com-
plex preparation. The complexes are stable, non-hygroscopic and
soluble in water.
Fig. 3. TG curves of the Fe(II) complexes of L1, L2, L3 and L4.

32
A. Onder et al. / Inorganica Chimica Acta 391 (2012) 28–35
3.1.1. 1H and 13C NMR spectra
between 58.67 and 51.61 ppm. The other ligands have the same
trends for proton and 13C NMR spectra.
Azomethine protons have singlets at 8.34, 8.30, 8.41 and
8.17 ppm for L1, L2, L3 and L4, respectively. In the region 7.65–
6.68 ppm chemical shifts were assigned to aromatic hydrogens.
There were chemical shifts of aliphatic hydrogen in the region
3.73–1.84 ppm. L1 has seven different carbons in the aromatic re-
gion and four peaks for aliphatic carbons. 13C NMR of this ligand
has seven peaks in between 180.49 and 117.26 and four peaks in
3.2. Mass spectra of the azomethines
The electron impact mass spectra of the azomethines were re-
corded and investigated at 50 eV of electron energy. The important
mass fragmentations and molecular ion peaks for the azomethines
Table 1
Thermal analysis data of the complexes.
Complexes
Step
Onset (°C)
DTG maximum (°C)
Endset (°C)
Leaving group
H2O
Mass loss (%)
Exp
Residue expt. (Calc.)
Calc.
[CuL1Cl2]ÁH2O
[CuL2Cl2]ÁH2O
1
2
1
2
3
1
2
3
4
1
2
3
1
2
3
4
5
1
2
3
4
1
2
3
4
1
2
3
4
5
1
2
3
1
2
3
4
1
2
3
25
279
25
132
280
25
156
302
587
25
282
607
25
145
243
340
653
25
116
275
600
25
171
284
636
25
118
179
298
610
25
197
415
132
162
456
136
170
445
755
177
362
776
145
191
292
455
931
116
142
430
696
171
202
478
729
118
138
191
448
706
166
222
354
157
187
409
542
196
392
756
4.00
67.40
6.80
4.48
75.73
8.20
CuO 28.20 (19.78)
CuO 28.60 (18.66)
344
L1 + Cl2
H2O
146
327
L2 + Cl2
64.40
8.20
75.00
8.48
[CuL3Cl2]Á2H2O
H2O
CuO 28.70 (18.65)
162
362
693
L3 + Cl2
62.80
72.77
[CuL4Cl2]Á3H2O
[FeL1Cl2]ÁH2O
H2O
12.00
54.50
13.11
67.57
CuO 23.50 (19.30)
FeO 24.30 (18.22)
329
704
L4 + Cl2
H2O
6.00
4.56
173
276
366
807
L1 + Cl2
68.40
77.20
[FeL2Cl2]Á2H2O
[FeL3Cl2]ÁH2O
[FeL4Cl2]ÁH2O
H2O
8.30
8.42
FeO 17.40 (16.82)
FeO 21.60 (18.04)
FeO 18.40 (17.38)
126
364
656
L2 + Cl2
73.50
74.75
H2O
4.00
4.52
186
352
683
L3 + Cl2
74.40
77.47
H2O
15.30
15.24
127
187
344
667
L4 + Cl2
71.00
14.40
67.36
14.75
[NiL1]Cl2Á4H2O
[NiL2]Cl2Á2H2O
H2O
NiO 27.00 (16.89)
NiO 25.20 (17.74)
166
320
25
157
272
489
25
197
338
L1 + Cl2
58.2
7.00
68.84
7.16
H2O
170
381
510
L2 + Cl2
67.80
75.77
[NiL4]Cl2Á5H2O
H2O
L4 + Cl2
21.20
59.10
20.36
62.95
NiO 18.80 (17.49)
196
392
392
725
Fig. 5. Electronic spectra of the ligands.

A. Onder et al. / Inorganica Chimica Acta 391 (2012) 28–35
33
Fig. 6. Electronic spectra of the Fe–L2 complex in H2O, acetyl acetone and DMF.
are shown in the spectra. The mass spectra of these ligands are gi-
ven as Supplementary information.
with the complex. This was also confirmed by the thermal and ele-
mental analysis studies. The sharp band at 832, the m(C–S–C) of thi-
L1: m/z = 134 peak was observed for the C8H8NO, OH–C6H4–
CH@N–CH2+. The base peak is observed at m/z = 99 for the
C5H11N2, CH3 attached to piperazine ring. The m/z = 84 for the
C4H8N2 for the piperazine ring. The m/z = 70 for the C3H6N2 for
the piperazine ring fragmentation.
ophene moiety in the L3 ligand, is shifted to 866–877 cmÀ1 for
metal complexes. Therefore, from the IR spectra, it is concluded
that azomethines bind to the metal ions; iron(II), copper(II) and
nickel(II) with azomethine nitrogen, phenolate O, NH, morpholine
oxygen and thiophene sulfur for L3.
L2: m/z = 134 peak was observed for the C8H8NO, OH-C6H4–
CH@N–CH2+. The base peak is observed at m/z = 100 for the
C5H11N2, CH3 attached to morpholine ring. The m/z = 70 for the
C4H6O for the morpholine ring fragmentation.
3.4. Thermal analysis of the complexes
L3: m/z = 111 peak was observed for the C6H7S. The base peak is
observed at m/z = 99 for the C5H11N2, CH3 attached to piperazine
ring. The m/z = 70 for the C3H6N2 for the piperazine ring
fragmentation.
Thermal analysis was performed to confirm the elemental anal-
yses and structure of the complexes. The TG curves of the com-
plexes show several steps of decomposition between 25 and
1200 °C (Figs. 2–4). The TG–DTA results of the thermal decomposi-
tions of azomethine complexes are given in Table 1. These steps in-
volved mass loss of hydration, counter ions and ligands. There is
mass loss up to 200 °C, indicating that either metal bonds or crystal
water molecules exist in these complexes [27]. The first mass loss
corresponds to the removal of the hydrated water from the com-
plex between 25 and 200 °C. On further heating of the dehydrated
complex above 200 °C, the organic part of the complex and counter
ions may decompose in one or two steps. These steps leave metal
oxides as residue. The DTA results show that all the stages of
decomposition were endothermic.
L4: The base peak is observed at m/z = 99 for the C5H11N2, CH3
attached to piperazine ring. The m/z = 70 for the C3H6N2 for the
piperazine ring fragmentation.
3.3. FTIR spectra
There are some guide peaks such as –CH@N–, –OH, NH, thio-
phene S and morpholine oxygen whose position or intensities are
expected to change upon complexation. The IR spectra of azome-
thine L2 and its complexes are shown in Fig. 1. The
mC@N stretching
vibration of the azomethines are found to be between 1627 and
1633 cmÀ1. These bands are shifted to lower wavenumbers upon
complexation for nickel(II) and iron(II) but higher wavenumbers
for Cu(II), indicating coordination of the azomethine nitrogen to
metal ions. It is reasonable to infer that after complex formation,
C@N possibly reflects a slight difference in the respective C@N
bond lengths in copper(II) complexes. FTIR spectra of the ligands
show a broad band between 3256 and 3435 cmÀ1, which can be
attributed to phenolic OH groups. This band shifts in all complexes,
which could be an indication of involvement in metal complexa-
tion. The m
C–O stretching bands are observed at about 560 cmÀ1
in L1 and L2 and these bands shift to lower or higher wave numbers
according to the complexes which is confirmation of M–O involve-
ment [24]. The shift of mC–O to a lower wave number suggests the
weakening of C–O and the formation of strong M–O bonds. The
N–H stretching wave numbers at about 3135–3200 cmÀ1in free
ligands show considerable shift in all complexes, indicating partic-
ipation of N–H in all complexes [26]. The IR spectra of all the com-
plexes exhibit a broad band around 3300–3460 cmÀ1, assigned to
m
(OH) of crystalline or coordinated water molecules associated
Fig. 7. Color of the Fe L2 in DMF Acetyl acetone and water.

34
A. Onder et al. / Inorganica Chimica Acta 391 (2012) 28–35
3.5. Electronic spectra and magnetic susceptibility
complexes of different metals decompose in a multi-step process.
Some complexes possessing octahedral geometry have a similar
mode of degradation to the evolution pattern of inorganic and or-
ganic fragments when heated up to 740 °C. Above this temperature
corresponding metal oxides are left as residue. Iron and nickel
complexes show greater thermal stability, probably owing to less
distortion of the octahedral structure and the size of nickel(II) ions.
On account of the simplicity of the structure of the aromatic tetra-
dentate complexes, they can be considered a model for studying
the relationships between thermal stability, coordination number
and chelate ring size for the same metal. The decomposition reac-
tion of aromatic azomethine metal complexes begins with the scis-
sion of the M–N bond. A correlation was also found between the
thermal stability and the basicity of the ligand. The nature of inter-
action of the crystallization water plays a significant role in the
thermal stability of the metal complexes. The solvatochromic
behavior of the iron(II)–L2 containing N2O2 donor set was studied.
The charge transfer transition band related to the solvent polarity
of the iron(II)–L2 complex is as follows: DMF (398 nm), AAA
(368 nm) and H2O (328 nm). Solvatochromism is strongly depen-
The electronic spectra of ligands were measured in methanol
and are given in Fig. 5. The aqueous UV–Vis spectra of the azome-
thine complexes show two absorption bands. One is the charge
transfer transition which is observed between 260 and 385 nm
and the other one is the d–d transition in between 438 and
641 nm [28]. The measured magnetic moments are in the range
1.55–1.96 BM for the copper complexes indicating the presence
of one unpaired electron. A moderately intense band at 357 nm
is due to the ligand–metal charge transition [29] and a broad low
intensity band at ꢀ500 nm.
The magnetic moment ꢀ1.9 BM falls within the range normally
observed for octahedral copper(II) complexes [30]. The nickel(II)
complexes are diamagnetic; this is supported by their square
planar geometry. Iron(II) complexes are also diamagnetic with
octahedral geometry.
3.6. Molar conductivity
The molar conductance of 1 Â 10À3 M solution of the complexes
was calculated at 20 °C. It is concluded from the results that nick-
el(II) complexes have molar conductance values between 230 and
248 S molÀ1 cm2, indicating the ionic character of these com-
plexes; while iron(II) and copper(II) complexes of these ligands
have low molar conductivity values between 12 and
23 S molÀ1 cm2. The nickel(II) complexes are considered to be 2:1
electrolytes with all ligands and chlorides exist as counter ions in
the complexes. These data show that iron(II) and copper(II) com-
plexes are non-electrolyte in nature.
dent on CT transitions and the nature of
p
conjugated system, p–
con-
p
and interaction in the ligand is also responsible. The p
p
–
p
jugated system is a phenyl ring combined with morpholine
through the azomethine group in L2 ligand.
Acknowledgment
We are grateful to COMU, BAP-2010/55 for financial support of
this study.
Appendix A. Supplementary material
3.7. Solvatochromism
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ica.2012.05.006.
The high solubility of FeL2 complex in various solvents and the
change in the color of its solutions from one solvent to another
yields solvatochromism. As part of the study on the spectroscopic
and thermal characteristics of the azomethines and complexes, the
electronic absorption spectra of this complex was measured in a
range of organic solvents with different polarities. The UV band
of this complex is assigned to the metal-to-ligand charge transfer
(MLCT) transition. The promotion of the electron in the low energy
orbital of the metal(t2g) to the p⁄ orbital of the ligand is the MLCT
transition. The energy of this band may be affected by solvation of
the hydrophobic surface of the azomethine ligand. The position of
this band shifted in different solvents, shown in Fig. 6. In pure sol-
vents, the shifts of the kmax values are found to depend on more
than one of the known solvent parameters. Acceptor number
(AN), donor number (DN), and p⁄ are found to be the most impor-
tant solvent parameters, exerting a considerable effect on the sol-
vatochromic shifts of the complex. The color of the FeL2 complex in
different solvents is illustrated in Fig. 7. It is likely that the solvato-
chromic property of iron(II)–L2 makes it an important candidate for
use in the field of non-linear optics.
References
[1] A Lowson, German patent, DE 2519193 A1, 1975.
[2] A.K. Mishra, N. Manav, N.K. Kaushik, Spectrochim. Acta, Part A 61 (2005) 3097.
[3] K. Nejati, Z. Rezvani, E. Alizadeh, R. Sammimi, J. Coord. Chem. 64 (2011) 859.
[4] O. Kotova, S. Semenov, S. Eliseeva, S. Troyanov, K. Iyssenko, N. Kuzmia, Eur. J.
Inorg. Chem. 23 (2009) 3467.
[5] A.A. Nejo, G.A. Kolawole, M.C. Dumbele, A.R. Opoku, J. Coord. Chem. 63 (2010)
4367.
[6] K.M. Vyas, V.K. Shah, R.N. Jadeja, J. Coord. Chem. 64 (2011) 1069.
[7] A.S. Gaballa, M. S Asker, A.S. Bakarat, S.B. Teleb, Spectrochim. Acta, Part A 67
(2007) 114.
[8] K.P. Balasubramanian, K. Parameswari, V. Chinnusamy, R. Prabhakaran, K.
Natarajan, Spectrochim. Acta, Part A 65 (2006) 678.
[9] E. Keskinoglu, A.B. Gunduzalp, S. Cete, F. Hamurcu, B. Erk, Spectrochim. Acta,
Part A 70 (2008) 634.
[10] V.T. Kasumov, S. Ozalp, E. Tas, Spectrochim. Acta, Part A 62 (2005) 716.
[11] L. Shi, H.M. Ge, S.H. Tan, H.Q. Li, Y.C. Song, H.L. Song, H.L. Zhu, R.X. Tan, Eur. J.
Med. Chem. 42 (2007) 558.
[12] A. Pui, J. Pieere, Polyhedron 26 (2007) 3143.
[13] M.M. Omar, G.G. Mohamed, A.A. Ibrahim, Spectrochim. Acta, Part A 73 (2009)
358.
[14] S. Mukhopadhyay, D. Mandal, D. Ghos, I. Goldsberg, M. Chaudhury, Inorg.
Chem. 42 (2003) 8439.
[15] Y.G. Li, D.H. Shi, H.L. Zhu, H. Yan, S.W. Ng, Inorg. Chim. Acta 360 (2007) 2881.
[16] P.S. Mukherjee, S. Dalai, G. Mostofa, T.H. Lu, E. Rentschler, N.R. Chaudhuri,
New. J. Chem. 25 (2001) 1203.
4. Conclusions
[17] H.L. Boraley, J. Therm. Anal. Calorim. 73 (2009) 358.
[18] A.S.M. Shirif, H.M. Fattah, J. Therm. Anal. Calorim. 71 (2003) 643.
[19] J. Lv, T. Liu, S. Cai, X. Wang, L. Lu, Y. Wang, J. Inorg. Biochem. 100 (2006) 1888.
[20] Y. Fukuda, Inorganic Chromotropism, Kodansha, Springer, 2007.
[21] W. Linert, Y. Fukuda, A. Camard, Coord. Chem. Rev. 218 (2001) 113.
[22] G. Knör, M. Leirer, T.K. Keyes, J.G. Vos, A. Vogler, Eur. J. Inorg. Chem. (2000) 749.
[23] J. Burgess, C.D. Hubbard, Struct. Chem. 21 (2010) 439.
[24] A. Al-Alousy, J. Burgess, A. Samotus, J. Szklarzewicz, Spectrochim. Acta, Part A
47 (1991) 985.
The structural, electronic, spectroscopic and thermal properties
of the ligands and complexes were investigated. The experimental
data suggest that tetradentate ligands coordinate to metals via
phenolate oxygen, azomethine nitrogen, piperazine nitrogen and
morpholine nitrogen and oxygen atoms. The spectroscopic, ther-
mal, conductivity and elemental analysis results indicate that the
coordination geometry around the copper and iron center are octa-
hedral consisting of tetradentate basal plane and two chlorides at
the axial site while nickel(II) complexes are square planar. All the
[25] M.M. Omar, G.G. Mohamed, Spectrochim. Acta, Part A 61 (2005) 929.
[26] C. Chandra, U. Kumar, Spectrochim. Acta, Part A 60 (2004) 2825.
[27] M. El-Beherey, H. El-Twigry, Spectrochim. Acta, Part A 66 (2007) 28.

A. Onder et al. / Inorganica Chimica Acta 391 (2012) 28–35
35
[28] J. Manonmani, R. Thirumurugan, M. Kandaswamy, M. Kuppayee, S.S.S. Raj,
M.N. Ponnuswamy, G. Shanmugam, H.K. Fun, Polyhedron 19 (2000) 2011.
[29] J. Sanmartin, M.R. Bermejo, A.M.G. Deibe, M. Maneiro, C. Lage, A.J.C. Filho,
Polyhedron 19 (2000) 185.
[30] F.A. Cotton, G. Wilkinson, C.A. Murillo, M. Bochmann, Advanced Inorganic
Chemistry, sixth ed., Wiley, New York, 1999.