The template synthesis, characterization, and thermal investigation of new heterocyclic binucleating Schiff base complexes

Article abstract of DOI:10.1081/SIM-200026585

1-Ammo-5-benzoyl-4-phenyl-1H-pyrimidine-2-one (L′H₂) reacts with benzil (L″O₂) and salts Cu(AcO)₂· H₂O, NiCl₂·6H₂O, Co(AcO)2·4H ₂O, CdCl₂·2H₂O in 2:1:2 mola

Full text of DOI:10.1081/SIM-200026585

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The Template Synthesis,
Characterization, and
Thermal Investigation
of New Heterocyclic
Binucleating Schiff Base
Complexes
Mehmet Sönmez a & Memet Şekerci b
a Department of Chemistry, Faculty of Science
and Arts , Yüzüncü Yıl University , 65080, Van,
Turkey
b Department of Chemistry, Faculty of Science
and Arts , Fırat University , Elazıgˇ, Turkey
Published online: 16 Nov 2010.
To cite this article: Mehmet Sönmez & Memet Şekerci (2004) The Template
Synthesis, Characterization, and Thermal Investigation of New Heterocyclic
Binucleating Schiff Base Complexes, Synthesis and Reactivity in Inorganic and
Metal-Organic Chemistry, 34:9, 1551-1561, DOI: 10.1081/SIM-200026585
To link to this article: http://dx.doi.org/10.1081/SIM-200026585
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 34, No. 9, pp. 1551–1561, 2004
The Template Synthesis, Characterization,
and Thermal Investigation of New
Heterocyclic Binucleating Schiff Base
Complexes
1,
Mehmet Sonmez and Memet S¸ekerci
2
*
¨
1Department of Chemistry, Faculty of Science and Arts, Yu¨zu¨ncu¨ Yıl
University, Van, Turkey
2Department of Chemistry, Faculty of Science and Arts, Fırat University,
ˇ
Elazıg, Turkey
ABSTRACT
1-Amino-5-benzoyl-4-phenyl-1H-pyrimidine-2-one (L0H2) reacts with
benzil (L00O2) and salts Cu(AcO)2 H2O, NiCl2 6H2O, Co(AcO)2 4H2O,
.
.
.
.
CdCl2 2H2O in 2 : 1 : 2 molar ratio in n-butanol to0 give several solid
00
.
complexes of the general composition [(M)2(L )2(L )(X)4] nH2O.
The precursor and the metal complexes of the Schiff base have been
*
¨
Correspondence: Mehmet Sonmez, Department of Chemistry, Faculty of
Science and Arts, Yu¨zu¨ncu¨ Yıl University, 65080 Van, Turkey; E-mail:
vansonmez@hotmail.com.
1551
DOI: 10.1081/SIM-200026585
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

¨
Sonmez and S¸ekerci
1552
characterized by elemental analyses, molar conductances, IR spectra,
electronic, and thermal studies.
Key Words: Template synthesis; Acyclic; Heterocyclic Schiff base.
INTRODUCTION
Interest in the metal complexes of acyclic compounds and macrocycles by
template reactions developed rapidly due to their biological relevance.[1]
Template reactions lie at the heart of macrocyclic chemistry. The synthesis
of cyclic and acyclic organic substrates that preferentially interact with
particular metal ions is of fundamental importance to many areas of chem-
istry.[2,3] The majority of the ligand systems employed in model studies
are derived from Schiff bases.[4] Condensations between dicarbonyls and
primary diamines, for example, have played an important role in the develop-
ment of synthetic acyclic and macrocyclic ligands. However, compounds
containing the pyrimidine ring are known to be biologically active.[5–7] We
recently reported the synthesis and characterization of heterocyclic complexes
obtained from N-aminopyrimidine-2-one.[8,9]
In this paper, we report our recent research on the template reactions of
N-aminopyrimidine-2-one with benzil in the presence of Cu(II), Ni(II),
Co(II), and Cd(II) ions to form (2 þ 1) Schiff base condensation complexes.
The new binucleating acyclic complexes have been characterized and
thermal investigation made by elemental analyses, UV-VIS, IR, spectra,
magnetic, and TG measurements.
EXPERIMENTAL
Materials and Methods
MeOH, EtOH, CHCl3, DMF, toluene, diethyl ether, n-heptane, and benzil
.
were obtained from Fluka or Aldrich. The metal salts Cu(OOCCH3)2 H2O,
.
.
.
Co(OOCCH3)2 4H2O, CdCl2 2H2O, and NiCl2 6H2O were obtained
from E. Merck. All solvents were dried and purified before use 1-Amino-
5-benzoyl-4-phenyl-1H pyrimidine-2-one was prepared as described
previously.[10]
Elemental analyses (C, H, and N) were performed using a Carlo Erba
1106 elemental analyzer. IR spectra were obtained using KBr discs (4000–
400) cm21 on a Bio-Rad-Win-IR spectrophotometer. Electronic spectra in

New Heterocyclic Binucleating Schiff Base Complexes
1553
the 200–900 nm range were obtained in DMF on a Unicam UV2-100 UV/VIS
spectrophotometer. Magnetic measurements were carried out by the Gouy
method using Hg[Co(SCN)4] as calibrant. Molar conductances of the Schiff
base ligand and its transition metal complexes were determined in DMF
at room temperature using a Jenway model 4070 conductivity meter.
TGA measurements were carried out by a Shimadzu-50 thermal analyzer.
Synthesis of the Complexes
The reaction was carried out in 2 : 1 : 2 molar ratio by combining
1-amino-5-benzoyl-4-phenyl-1H-pyrimidine-2-one (L0H2) (0.582 g, 2 mmol),
benzil (L00O2) (0.21 g, 1 mmol), and Cu(AcO)2 H2O, Co(AcO)2 4H2O,
.
.
.
.
CdCl2 2H2O; or NiCl2 6H2O (0.40 g, 2 mmol; 0.50 g, 2 mmol; 0.44 g,
2 mmol; and 0.48 g, 2 mmol) in n-butanol (70 mL). The mixture was heated
under reflux 3–6 hr. The solution was then cooled and transferred to an
evaporating dish and set aside overnight at room temperature. The solid
products that separated out were collected, washed with dry diethyl ether,
then with cold methanol and dried under vacuo.
RESULT AND DISCUSSION
The template condensation of 1-amino-5-benzoyl-4-phenyl-1H-pyrimidine-
2-one[10] (L0H2) and benzil (L00O2) in the presence of Cu(AcO)2 H2O,
.
.
.
.
Co(AcO)2 4H2O, CdCl2 2H2O, or NiCl2 6H2O produced new acyclic
0
00
.
binuclear metal complexes of the types [(M)2(L )2(L )(X)4] nH2O as shown
in Fig. 1. All the complexes are non-hygroscopic and stable at room tempe-
rature. These complexes are soluble in DMF and DMSO. The molar
conductances of the solution of the complexes in DMF (1 mM) are in the
range 3.60–25.28 S cm2 mol21. These values are lower than those expected
for an electrolyte.[14] Molar conductance value of the Cd(II) complex is
25.28 V21 cm2 mol21. The Cd(II) complex, which contains coordinated chlor-
ide ions, is non-conducting or shows an increasing degree of conductivity
with time which would be due to their replacements by DMF solvent
molecules.[8,14] These observations suggest that all of the complexes are
non-electrolytes in DMF (1 ꢀ 1023 M) at room temperature.
The ligands, (L0H2) and (L00O2), on reaction with Cu(AcO)2 H2O,
.
.
.
Co(AcO)2 4H2O, and NiCl2 6H2O yield complexes corresponding to the
general formula [Cu2(L0)2(L00)(AcO)4] (815 mg, 73%), [Co2(L0)2(L00)(AcO)4]
0
00
0
00
.
(740 mg, 68%), [Ni2(L )2(L )Cl4] 4H2O (706mg, 65%), and [Cd2(L )2(L )Cl4]
(920 mg, 82%), respectively. The analytical data for all of the complexes are

¨
Sonmez and S¸ekerci
1554
Figure 1. Scheme for the preparation of the binuclear Schiff base complexes.
presented in Table 1. The analytical data and spectral results are in good
agreement with the proposed stoichiometry of the complexes.
Infrared Spectral Study
The infrared spectra of the ligand, (L0H2) and (L00O2), and the metal com-
plexes show the absence of uncondensed functional group (NH2 and C55O),
stretching modes of the starting materials and the appearance of bands charac-
teristic of the imine group.[11,12] The bands characteristic of the benzil moiety
appeared in all of the complexes at 1477–1498 cm21 [(nasym C6H5) and
1373–1392 cm21 (nasym C6H5)]. The major changes observed in the spectra
of the binuclear metal complexes are the absence of stretching and defor-
mation vibrations of NH2 groups, indicating their deprotonation and the
appearance of strong bands due to coordinated n(C55N) vibrations[11] in
the range 1626–1605 cm21. Strong and sharp bands for C–H stretching
and banding vibrations appear[11] at ca. 3049–3063 cm21. In the IR spectra
nsym (OCO) appears at 1370 cm21 and nasym (OCO) together with the
imine n(C55N) as an intense brood absorption band in the region 1620–
1640 cm21. Such widely spaced acetate bands are consistent with the mono-
dentate coordination proposed in the metal complexes [Cu2(L0)2L00)(AcO)4]
and [Co2(L0)2(L00)(AcO)4]. The presence of the new bands in the spectra of
the metal complexes in the region at 438–457 cm21 due to the n(M–N)
vibration supports the coordination of the imine nitrogen to the metal ion.[9]
In the Ni(II) and Cd(II) complexes bands at 409 and 413 cm21 are observed
which may be assigned to a coordinated chloro group (Table 2).[11,12]

New Heterocyclic Binucleating Schiff Base Complexes
1555
m

¨
Sonmez and S¸ekerci
1556
l

New Heterocyclic Binucleating Schiff Base Complexes
Electronic Spectra and Magnetic Measurements
1557
Similar UV/VIS spectra are obtained for the complexes in DMF. The
binuclear Cu(II) complex with L0H2 and L00O2, a tetradentate, has been found
to have two acetate groups in the coordination sphere of per copper atom.
The electronic spectra of the binuclear copper complex show two bands in
2
2
the regions 610 and 467 nm which may be assigned to the B1g ! A1g and
2
2B1g ! Eg transitions,[13] respectively, corresponding to square-planar
geometry around the copper ions.
The magnetic moment value, 3.61 BM (300 K) per cobalt atom, obtained
for the milk–brown complex was in the range expected for a cobalt(II)
complex. The electronic spectra of the compound showed d–d transition in
the visible region of the spectrum. The band at 545 nm may be assigned
2
2
to the A1g ! Eg transition as expected for a cobalt(II) square-planar
complex.[13]
Since the ground term 3T1 in the tetrahedral Ni(II) complexes is orbitally
degenerate, the magnetic moment is expected to be raised considerably over
the spin-only value through orbital contribution. The experimental moments
lie within the range 3.2–4.1 BM and are dependent upon the tempe-
rature.[13,14] The binuclear Ni(II) complex is consistent with tetrahedral
geometry shows a magnetic moment of 1.81 BM per nickel atom at room
temperature. The electronic spectrum (DMF) of the Ni(II) complex shows
3
2
one d–d transition band at 660 nm assignable to T1(F) ! A2(F) (n3) and
1
a band at 430 nm, an excited state derived from the G term.[13] n3 appears
as two peaks and a shoulder.
The electronic spectra of the Cd(II) complex which is diamagnetic, has
bands in the 329–297 nm range and these bands may be due to the n ! pꢁ
and p ! pꢁ transitions of the benzene, pyrimidine rings, and azomethine
group.
Thermal Studies
The thermal stability of the complexes was investigated using TGA.
The TGA curves were obtained at a heating rate of 10 8C/min in N2 atmos-
phere over the temperature range of 25–850.0 8C. The Cu(II) complex was
stable up to 185.0 8C and its decomposition started at this temperature and
was completed at 530.0 8C. The Cu(II) complex decomposed and produced
2CuO as residue [(found/calculated), %: 15.00/14.21] in three steps in the
temperature ranges 185.0–268.0, 268.0–305.0, and 305.0–530.0 8C. In the
decomposition process of the Cu(II) complex, the mass losses corresponded
to 2CH3COO, L00 and 2CH3COO, and 2L0 leaving in the first, second, and

¨
Sonmez and S¸ekerci
1558
third stages of the decomposition, respectively. The three stages of the decom-
position of the Cu(II) complex are irreversible. The Ni(II) complex was stable
up to 32.0 8C and its decomposition started at this temperature and was com-
pleted at 613.8 8C. The Ni(II) complex decomposed and produced 2NiO as
residue [(found/calculated), %: 12.53/13.73] in four steps in the temperature
ranges 32.0–120.0, 120.0–278.0, 278.0–280.0, and 280.0–613.08 8C. In the
decomposition process of the Ni(II) complex, the mass losses corresponded to
4H2O, 2Cl, 2Cl and L00, and 2L0 leaving in the first, second, third, and fourth
stages of the decomposition, respectively. The four stages of decomposition of
the Ni(II) complex are irreversible. The Co(II) complex was stable up to
180.0 8C and its decomposition started at this temperature and was completed
at 516.3 8C. The Co(II) complex decomposed and produced 2Co3O4 as residue
[(found/calculated), %: 16.00/14.46] in three steps in the temperature ranges
180.0–250.0, 250.0–400.0, and 400.0–516.3 8C. In the decomposition
process of the Co(II) complex, the mass losses corresponded to 2CH3COO,
2CH3COO and L00, and 2L0 leaving in the first, second, and third stages of
the decomposition, respectively. The three stages of the decomposition of
the Co(II) complex are irreversible.
The Cd(II) complex was stable up to 146.0 8C and its decomposition
started at this temperature and was completed at 629.2 8C. The Cd(II)
complex decomposed and produced 2CdO as residue [(found/calculated),
%: 21.26/22.87] in two steps in the temperature ranges 146.0–481.0
and 481.0–629.2 8C. In the decomposition process of the Cd(II) complex,
the mass losses corresponded to 2L0 and L00 and 2Cl leaving in the first and
second stages of the decomposition, respectively. The two stages of the
decomposition of the Cd(II) complex are irreversible.
The Cu(II) and Co(II) complexes are thermally stable up to 185.0 and
180.0 8C, respectively, whereas the Ni(II) complex is thermally stable up to
32.0 8C. In the TGA curve of the Ni(II) complex, 6.10% weight loss was
observed at 120.0 8C. This shows that the Ni(II) complex contains 4 mol of
water molecules of crystallization per complex molecule. The IR spectra of
the complexes are characterized by the appearance of a broad band in the
region 3410 cm21 due to the n(O–H) frequency of water of crystallization.
This water content was also identified by TG analyses. This decomposition
process of the Cu(II), Ni(II), and Co(II) complexes was also confirmed
by TGA data. As can be seen in Table 3, the most stable complex is the
Cu(II) complex. The weight losses for the Cu(II), Ni(II), Co(II), and Cd(II)
complexes were found to be approximately the same, when expressed as the
percentages calculated stoichiometrically from their chemical formulas
given in Tables 1 and 3. All of these complexes undergo complete decompo-
sition to the corresponding metal oxides, CuO, NiO, Co3O4, and CdO[8,15,16]
(Table 3).

New Heterocyclic Binucleating Schiff Base Complexes
1559

¨
Sonmez and S¸ekerci
1560
Single crystals of the complexes could not be isolated from any solutions,
thus no definitive structure may be described. However, the analytical,
spectroscopic, magnetic data, and thermal investigation enable us to predict
the possible structures as shown in Fig. 1.
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Received June 30, 2003
Accepted April 26, 2004