Bis(N,N-diethylnicotinamide) p-chlorobenzoate complexes of Ni(II), Zn(II) and Cd(II) : SSynthesis and characterization

Article abstract of DOI:10.1007/s10973-008-9150-8

Three novel mixed ligand complexes of Ni(II), Zn(II) and Cd(II) with p-chlorobenzote and N,N-diethylnicotinamide were synthesised and characterized on the basis of elemental analysis, FTIR spectroscopic analysis, solid state UV-Vis spectrometric and magne

Full text of DOI:10.1007/s10973-008-9150-8

Journal of Thermal Analysis and Calorimetry, Vol. 95 (2009) 1, 247–251
Bis(N,N-DIETHYLNICOTINAMIDE) p-CHLOROBENZOATE
COMPLEXES OF Ni(II), Zn(II) AND Cd(II)
Synthesis and characterization
D. A. Köse1,2*, G. Gökçe2, S. Gökçe2 and . Uzun3
1Hacettepe University, Department of Chemistry, Beytepe Campus, 06532 Ankara, Turkey
2Kafkas University, Faculty of Art and Science, Department of Chemistry, PaêaçayÏrÏ, 36100 Kars, Turkey
3Kýrýkkale University, Department of Mechanical Engineering, Faculty of Engineering, 71450 Kýrýkkale, Turkey
Three novel mixed ligand complexes of Ni(II), Zn(II) and Cd(II) with p-chlorobenzote and N,N-diethylnicotinamide were synthe-
sised and characterized on the basis of elemental analysis, FTIR spectroscopic analysis, solid state UV-Vis spectrometric and mag-
netic susceptibility data. The thermal behavior of the complexes was studied by simultaneous TG–DTA methods in static air atmo-
sphere and the mass spectra data were recorded.
According to microanalytical results, formulas of complexes are C34H40N4O8ClNi, C34H40N4O8ClZn and C34H44N4O10ClCd.
The complexes contain two moles of coordination waters, two moles p-chlorobenzoate and two mole N,N-diethylnicotinamide
(dena) ligands per formula unit. In these complexes, the p-chlorobenzoate and N,N-diethylnicotinamide behave as monodentate
ligand through acidic oxygen and nitrogen of pyridine ring. The decomposition pathways and the stability of the complexes are in-
terpreted in the terms of the structural data. The final decomposition products were found to be as metal oxides.
Keywords: p-chlorobenzoate N,N-diethylnicotinamide, mixed ligand complexes, thermal decomposition, transition metal complexes
Introduction
The N,N-diethylnicotinamide (dena) ligand has been
coordinated by hetero nitrogen atom of pyridine ring.
These types of complexes are resembled to in literature
[11–17]. It is not surprising; therefore, that many
authors have investigated heterocyclic compounds
and also examined them as ligands in coordination
compounds of several central atoms. The presence of
pyridine ring in numerous naturally abundant com-
pounds, adducts of dena are also scientific interest.
Therefore, the structure of dena has been the subject
of many studies [18–22]. The thermal decomposition
properties of title compounds are compatible with
literature [23–29].
The diversity of inorganic compounds and their applications
in medicine encompass cancer chemotheraphy, arthritis,
antimicrobial agents, metalloenzyme inhibitors, antimanic
agents and many others [1]. The carboxylates play an
important role in inorganic chemistry, and then again
many metal cations in a great number of various
biological processes, especially six-membered ring
system, are components of several vitamins and
drugs [2]. Also some carboxylate compounds
(e.g. benzoates) are known to have antibacterial activ-
ity. Benzoic acid is used in combination with salicylic
acid in dermatology as a fungicidal treatment for
fungal skin diseases [3, 4]. Metal complexes of
biologically important ligands are sometimes more
effective than the free ligands [5]. It is well docu-
mented that heterocyclic compounds play a signi-
ficant role in many biological systems, especially
N-donor ligand systems being a component of several
vitamins and drugs [6–9]. In the coordination com-
pounds of some transition metals of aryl carboxylic
acid and derivatives of halogeno, the bonding occurs
by acidic –OH group of carboxylic acid as
monodentate [10]. According to X-ray structures in
literature, halogeno group of aryl carboxylic acid has
not participated to coordination and it is to free.
In the present paper, we reported the synthesis,
spectroscopic and thermal properties of some new
mixed-ligand complexes of Ni(II), Zn(II) and Cd(II)
containing p-chlorobenzoate-N,N-diethylnicotinamide.
The structures of the ligands are shown in Fig. 1.
Fig. 1 Structures of the ligands
*
Author for correspondence: dkose@hacettepe.edu.tr
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2008 Akadémiai Kiadó, Budapest

KÖSE et al.
Experimental
Methods
Materials
Elemental analyses (C, H, N) were performed by
standard methods in Tubitak Laboratory (Scientific
and Technical Research Council of Turkey). Magnetic
susceptibility measurements at room temperatures
were determined on a Sherwood Scientific MXI model
magnetic balance (Gouy Method) using Hg[Co(SCN)4].
IR spectra were recorded in 4000–400 cm–1 region
with a Perkin Elmer 1000 FTIR spectrophotometer as
KBr pellets.
All chemicals used were analytical reagent products.
NiSO4·6H2O, ZnSO4·6H2O, CdSO4·6H2O and
p-chlorobenzoic acid were obtained from Merck
(Darmstadt, Germany). Diethylnicotinamide was
purchased from Darmitsa Chemicals Union (Kiev,
Ukraine).
Preparation of p-chlorobenzoate complexes
Thermal analysis curves (TG-DTA) were re-
corded simultaneously in a static air atmosphere with
a Schimadzu DTG 60 thermal analyzer. The samples
weighed approximately 10 mg and highly sintered
a-Al2O3 was used as a reference material. The heating
rate was 10°C min–1 and the DTG sensitivity is
0.05 mg s–1. Schimadzu UV3600/UV-VIS-NIR model
spectrophotometer was used for solid state ultravio-
let-visible range studies. Mass spectrum data were re-
At the first step, p-chlorobenzoic acid sodium salts
were prepared according to the following equation:
2p-Clba+2NaHCO3®2Na(p-Clba)+2CO2+2H2O
where p-Clba=p-chlorobenzoic acid.
At the second step, M(II)-p-Clba salts were syn-
thesized from Na(p-Clba) salt by substitution reaction:
2Na(p-Clba)+MSO4·6H2O®
®M(p-Clba)2·nH2O+Na2SO4
corded
Agilent
with
Technologies
5973
spectrophotometer using DIP-MS method.
where M=Ni(II), Zn(II) and Cd(II).
The compounds of M(p-Clba)2·nH2O were occurred
in aqua media.
Results and discussion
The complexes were synthesized with high purity.
The results of the elemental analysis indicated that the
complexes contain two moles of p-chlorobenzoate,
two moles N,N-diethylnicotinamide ligands and two
moles of coordinated water per mole formula units.
The two moles of hydrate waters is bonded to Cd(II)
complex by hydrogen bonds, but Ni(II) and Zn(II)
complexes has not any hydrate water. Analytical results,
compositions of the complexes and confirmation the
proposed formula of the complexes are given in Table 1.
In the complexes, octahedral coordination of the
Ni(II), Zn(II) and Cd(II) ions are formed by
carboxylic acid oxygen atoms from two moles of
p-chlorobenzoates as monoanonic monodentate
ligand and two donor nitrogen atoms from two
N,N-diethylnicotinamides and two moles of coordinated
waters. The suggested coordination of metal was
compatible with literature [15, 22, 23, 30].
Synthesis of mixed-ligand complexes
A solution of dena (2 mmol) in distilled water (30 mL)
was added dropwise with stirring to a solution of
M(p-Clba)2(H2O)n (1 mmol) in hot distilled water
(50 mL). The solutions were heated to 50°C in a tem-
perature-controlled bath and stirred for 4 h and then
cooled to room temperature and allowed to stay
10–12 days for crystallization. The crystals formed
were filtered and washed with cold water and acetone
and dried in vacuo. The mixed-ligand complexes
were prepared according to the following equations:
M(p-Clba)2(H2O)n+2dena®
®M(p-Clba)2(dena)2(H2O)n
where dena:N,N-diethylnicotinamide.
Table 1 Analytical data of the metal complexes
Found (calcd.)/%
Complex
M/g mol–1
762.29
Yield/%
75
C
H
N
[Ni(p-Clba)2(dena)2(H2O)2]
53.51
5.09
7.43
C34H40N4O8ClNi
(53.56)
(5.25)
(7.35)
[Zn(p-Clba)2(dena)2(H2O)2]
768.99
86
52.89
5.01
7.26
C34H40N4O8ClZn
(53.09)
(5.27)
(7.20)
[Cd(p-Clba)2(dena)2(H2O)2]·2H2O
852.01
90
47.83
4.85
6.65
C34H44N4O10ClCd
(47.92)
(5.16)
(6.58)
adecomposition point p-chlorobenzic acid (p-Clba), N,N-diethylnicotinamid (dena)
248
J. Therm. Anal. Cal., 95, 2009

bis(N,N-DIETHYLNICOTINAMIDE)-p-CHLOROBENZOATE COMPLEXES OF Ni(II), Zn(II) AND Cd(II)
Due to the low solubility, solid sample record
satisfactory UV-Vis spectra for the complexes was
studied. The electronic spectrum of the Ni(II) complex
acid is that the C=O stretching vibration of the
carboxyl group at 1730–1708 cm–1 is shifted to lower
frequency (1623, 1619 and 1620 cm–1, respectively) in
all the metal complexes. This may be a consequence
of coordination takes place through the carboxyl group
by deprotonation of the p-Clba molecule during
coordination. When the metal-p-Clba-dena mixed
ligand complexes are produced, the peak of acidic
COOH group at 1688 cm–1 disappears [16]. At the
same time, in the complexes, the (COO–)as are located
at 1548 cm–1 for Ni(II), 1550 cm–1 for Zn(II) and
1546 cm–1 for Cd(II) complexes. (COO–)s peaks are
observed at 1397 cm–1 for Ni(II), 1392 cm–1 for Zn(II)
and 1391 cm–1 for Cd(II) complexes. The splitting of
the nas and ns bands of COO– groups are for Ni(II),
Zn(II) and Cd(II) complexes almost identical (151,
158 and 155 cm–1, respectively) and slightly than for
the sodium salts of these acids (134 cm–1) [31] that
monodentate carboxylate group exists [32]. For
monodentate geometry of carboxylate group, the
bands of nas(COO–) ns(COO–) in synthesized complexes are
shifted to higher and lower region or nas(COO–)prepared
complex>ns(COO–)sodium salt. The band of nC–Cl is almost in
the same position in the FTIR spectra of prepared
complexes (780 cm–1 for Ni(II) and Zn(II), 778 cm–1
for Cd(II)) as in the spectrum of sodium salt
(780 cm–1). This result is supported since, the
p-chlorobenzoate ligand do not coordinate to metal
atom via halogen group [33]. The low intensity bands
in the region of 710–450 cm–1 are attributed to M–N for
dena ligand and M–O for p-Clba vibrations [22, 34–37].
3
shows absorption bands at about 7500 cm–1 (3A2g® T2g),
3
15400 cm–1 (3A2g® T1g)(3F) and 25300 cm–1
3
(3A2g® T1g)(3P). The Zn(II) and Cd(II) complexes do
not show any absorption peak in UV bands. The
*
peaks belonging to the p®p transitions are shifted to
a longer wavelength as a consequence of coordination
when binding with metal, confirming the formation of
p-Clba–dena metal complexes. The Ni(II) complex is
paramagnetic while, Zn(II) and Cd(II) complexes are
diamagnetic. These values suggest octahedral coordination
around the metal ions.
FTIR spectra
Characteristic FTIR spectrum peaks of the complexes
are given in the Table 2. When investigation of FTIR
spectra of complexes –OH absorption bands of aqua
ligands are presence in the range of 3600–2900 cm–1
correspond to the asymmetric and symmetric stretching
vibration of water molecules. Pyridine ring vibrations
of free diethylnicotinamide at 1580 cm–1 shifts to
lower frequencies in the spectrum of the metal
complexes. These shifts are shown in range of
1420 cm–1 for Ni(II), 1415 cm–1 for Zn(II) and
1413 cm–1 for Cd(II), it may indicate that the pyridine
ring is coordinated. Conjugation between the
carbonyl group and the amide nitrogen causes small
frequency shifts. The strong bands observed at around
1580 cm–1 for Ni(II), 1582 cm–1 for Zn(II) and
1585 cm–1 for Cd(II) are assigned to this mode. The
main difference in the spectrum of p-chloro-benzoic
Thermal data
[Ni(p-Clba)2(dena)2(H2O)2]
Table 2 Characteristic FTIR peaks of metal complexes
TG-DTA curves for the Ni(II) complex are given in
Fig. 2. Two moles of coordinated water of this complex
are removed in the interval of 100–167°C and at
133°C gives max. DTA peak (exp. 5.23%;
calc. 4.73%). After then at this temperature, organic
Gruplar
Ni(II)
Zn(II)
Cd(II)
n(–OH)H2O
n(C–H)
3550–2900
3056
1623
1548
1472
1397
151
3500–3100
3067
1619
1550
1470
1392
158
3600–2900
3090
1620
1546
1465
1391
155
n(C=O)ester
n(COO–)as
d(H2O)
n(COO–)s
Dn
n(C–O–C)
n(C–H)CH3
n(C–N)py
n(C–N)amid
nC=O)amid
n(C–halogen)
nMe–N
1170
1319
1420
1271
1580
780
1171
1319
1415
1293
1582
780
1195
1312
1413
1281
1585
778
646
644
635
nMe–O
480
470
475
Fig. 2 TG-DTA curve of the [Ni(p-Clba)2(dena)2(H2O)2]
J. Therm. Anal. Cal., 95, 2009
249

KÖSE et al.
ligands start to decompose together. The decomposition
occurs in the temperature range of 175–605°C at four
steps by giving endothermic DTA peaks at 224, 296
and 356°C. At the result of the removing organic
ligands, NiO is the residue (exp. 10.55%; calc. 9.84%).
The final decomposition product, by IR spectroscopy
with corresponding spectra obtained under the same
conditions as the pure oxides
[Zn(p-Clba)2(dena)2(H2O)2]
Firstly, dehydration of two moles of crystal water occur
at 107 and 150°C in two steps by giving endothermic
DTA peak (Fig. 3) (exp. 5.02%; calc. 4.68%). The
anhydrous Zn(II) complex is not stable and after the
dehydration fortwith organic parts start to decompose
in the range of 170–522°C by giving endothermic
DTA peaks at 223, 294 350 and 448°C. Lastly,
decomposition of the complex, the residue ZnO
was identified by IR spectroscopy (exp. 10.11%;
calc. 10.47%). The experimental values for the mass
loss of the dehydration stage are well consistent with
the calculated values.
Fig. 4 TG-DTA curve of the [Cd(p-Clba)2(dena)2(H2O)2]·2H2O
temperature range of 202–697°C (endothermic DTA
peaks at 217, 412, 566 and 675°C). The final
decomposition product is CdO (exp. 14.150%;
calc. 15.27%). Similar decompositions behaviors are
shown in literature [15, 23, 27–30, 34].
Mass spectra
To conclude the thermal decomposition pathway of
the [Ni(p-Clba)2(dena)2(H2O)2] complex mass spectrum
was recorded (Fig. 5) using direct insertion probe
pyrolysis mass spectrometry method. The molecular
ion peak is not detected in the recorded mass
spectrum. The obtained mass spectrum is relatively
complex and exhibits a large number of peaks that
extend to m/z value above 750. These peaks belong to
decomposition products of complex and ligands.
Fig. 3 TG-DTA curve of the [Zn(p-Clba)2(dena)2(H2O)2]
[Cd(p-Clba)2(dena)2(H2O)2]·2H2O
The thermal decomposition of Cd(II) complex starts
at the 65–102°C temperature range with the release of the
two moles of hydrate waters (exp. 4.23%; calc. 4.21%).
The decomposition is occurred one-step by giving
endothermic DTA peak at 91°C. The coordinated
aqua ligands of Cd(II) complex are dehydrated in the
one-step temperature in the interval of 168–197°C
giving endothermic DTA peak at 186°C (exp. 4.67%;
calc. 4.23%). The decomposition of the complex
associated with the complete pyrolysis of the organic
part of the compound starts above this temperature.
The thermoanalytical responses of the complex is
shown in Fig. 4. The organic part of the comlex
decomposes with the release of CO2 molecules. The
descending continuous TG curve is obtained in the
Fig. 5 Mass spectrum of [Ni(p-Clba)2(dena)2(H2O)2] complex
Conclusions
The IR spectra of the intermediate products show similar re-
sults. In the complexes, all ligands are coordinated to the
metal ion as monodentate and their structures are octahe-
dral that in each complex, two moles aqua, two moles
p-chlorobenzoate and two moles dena ligands coordi-
nate to metal ion. The p-chlorobenzoate ligand was
bonded to concerned metal atoms via acidic oxygen
atom and N,N-diethylnicotinamide via nitrogen atom of
250
J. Therm. Anal. Cal., 95, 2009

bis(N,N-DIETHYLNICOTINAMIDE)-p-CHLOROBENZOATE COMPLEXES OF Ni(II), Zn(II) AND Cd(II)
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G. V. Tsintzade and V. S. Segienko, Koord. Khim.,
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6 (1980) 1606.
ands remove almost in the same temperature range from all
22 E. F. Öztürkkan, D. A. Köse, H. NecefoÈlu and I. Uzun,
of the metal complexes. The complexes lose crystal water
Asian J. Chem., 19 (2007) 4880.
molecules in one-step. There is a study about determina-
tion of [Zn(p-Clba)2(dena)2(H2O)2] structure in [38]
supports probable structures proposed of our results.
After the dehydration process, decomposition stages
of the anhydrous complexes are related to release
N,N-diethylnicotinamide and the partial decomposition of
p-chlorobenzoate involving the release of CO2. Previous
studies show that the benzoate-metal complexes decom-
pose by releasing of CO2 [39–43]. The order of com-
plexes according to changing of stabilities are
Ni(II)>Zn(II)>Cd(II), anhydrous complexes are limited
Zn(II)>Cd(II)>Ni(II). The final decomposition products
were concerned as metal oxides in the 700–900°C tem-
perature intervals. The mass spectrum shows that m/z
molecular ion peaks belong to organic parts of Ni(II)
complex. For example; at 177m/z, 120m/z may belong
to N,N-diethylnicotinamide, benzoate ion respectively.
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DOI: 10.1007/s10973-008-9150-8
J. Therm. Anal. Cal., 95, 2009
251