A new cyclic ligand and complexes of its open-chain tautomer with Co(III) and Ni(II) ions: Synthesis, characterization and thermal properties

Article abstract of DOI:10.1080/15533174.2012.756029

A new ligand, 2-(p-tolyl)-1,2,3,4-tetrahydroquinazoline-2 -carbaldehyde oxime, was synthesized from a condensation reaction of oxo-p-tolyl-acetaldehyde oxime with 2-aminobenzyl- amine and then amine-imine-oxime complexes of this compound that formed with Co(III) and Ni(II) ions were obtained. All structures were characterized by spectral methods, elemental analysis, magnetic susceptibility, molar conductivity, and thermal analyses. The results that were obtained show that the cyclic ligand, HL, undergoes a ring-opening reaction upon complexation with metal ions. The Co(III) and Ni(II) complexes have a metal-ligand ratio of 1:2 and the imine ligand coordinates through the amine, imine, and oxime groups nitrogen atoms with metal ions. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2012.756029

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A New Cyclic Ligand and Complexes of Its Open-Chain
Tautomer with Co(III) and Ni(II) Ions: Synthesis,
Characterization and Thermal Properties
G. Şirikçi a , H. Mutlu Gençkal a & G. İrez a
a Department of Chemistry, Faculty of Arts and Sciences, Uludağ University, Bursa, TURKEY
Accepted author version posted online: 03 Apr 2013.
To cite this article: G. Şirikçi , H. Mutlu Gençkal & G. İrez (2013): A New Cyclic Ligand and Complexes of Its Open-Chain
Tautomer with Co(III) and Ni(II) Ions: Synthesis, Characterization and Thermal Properties, Synthesis and Reactivity in
Inorganic, Metal-Organic, and Nano-Metal Chemistry, DOI:10.1080/15533174.2012.756029
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A New Cyclic Ligand and Complexes of Its OpenChain Tautomer with Co(III) and Ni(II)
Ions: Synthesis, Characterization and Thermal Properties
G. Şirikçi, H. Mutlu Gençkal* and G. İrez
Department of Chemistry, Faculty of Arts and Sciences, Uludağ University, Bursa, TURKEY
* Corresponding Author
Dr. Hasene MUTLU GENÇKAL
Email : hasenem@uludag.edu.tr
Tel: +90 224 2941734
Fax: +90 224 2941899
ABSTRACT
In this study, a new ligand, 2(ptolyl)1,2,3,4tetrahydroquinazoline2carbaldehyde
oxime, was synthesised from a condensation reaction of oxoptolylacetaldehyde oxime with
2aminobenzylamine and then amineimineoxime complexes of this compound that formed
with Co(III) and Ni(II) ions were obtained. All structures were characterised by spectral
methods, elemental analysis, magnetic susseptibility, molar conductivity and thermal analyses.
The results that were obtained show that the cyclic ligand, HL, undergoes a ringopening
reaction upon complexation with metal ions. The Co(III) and Ni(II) complexes have a metal
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ligand ratio of 1:2 and the imine ligand coordinates through the amine, imine and oxime groups
nitrogen atoms with metal ions.
Keywords: 2(pTolyl)1,2,3,4tetrahydroquinazoline2carbaldehyde oxime; Ringchain
tautomerism, Amineimineoxime; Co(III) complex; Ni(II) complex
INTRODUCTION
Quinazoline is composed of two fused sixmembered simple aromatic rings, a benzene
ring and a pyrimidine ring. Studies of the quinazoline compounds began only with discovery of
febrifugine, a quinazolinone alkaloid, possessing antimalarial potential[1]. At present,
quinazoline derivatives are used in the pharmaceutical industry because of wide variety of
activities such as, antitumor[2], antiinflammatory[3], anticonvulsant[4] and antimicrobial[5,6]. For
example, 3phenyl2,4dithioxo1,2,3,4tetrahydroquinazoline is a PDE7 inhibitor and new
therapeutic agent for neuroprotection[7]. Doxazosin mesylate is an α1selective alpha blocker
that is used to treat high blood pressure and urinary retention[8].
1,2,3,4tetrahydroquinazolines include the benzene ring and the hexahydropyrimidine
ring. The formation of tetrahydroquinazoline is a synthesis of a Schiff base from aldehydes[9] and
2aminobenzylamines; there is a ringchain tautomeric equilibrium between the
tetrahydroquinazoline and the Schiff bases[912]. According to Sinkkonen and coworkers, in
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1,3−unsubstituted tetrahydroquinazolines can exist ringchain tautomeric equilibria containing
cyclic form, aniline type and benzylamine type chain forms[11]. According to GarcíaDeibe and
coworkers, the tetrahydroquinazoline compound is the most stable form of the two tautomers,
and the ringchain tautomerism of a 2aryl1,2,3,4tetrahydroquinazoline can be exploit to
induce reversible changes in the aminalimine equilibrium, as desired, by coordination of a
suitable metal ion[13]. Recently, a few 2subsitituted1,2,3,4−tetrahydroquinazoline derivatives,
containing substituted oxime, have been synthesised from a condensation reaction of αcarbonyl
oxime with 2aminobenzylamine (2ABA), characterised in detail by us and used for
complexation with some transition metal ions, i.e., Ni(II)[14,15] and Co(III)[15-18] complexes. The
2subsitituted1,2,3,4tetrahydroquinazoline oxime compounds are good chelating agents
owing to the presence of three nitrogen atoms. Despite the fact that there are different
substituents at 2position in these ligands, the aniline type chain form is maintained in the
complexes[15-18]
.
In this work, the new cyclic ligand, 2(ptolyl)1,2,3,4tetrahydroquinazoline2
carbaldehyde oxime, HL, and the complexes of its openchain tautomer with Co(III) and Ni(II)
metal ions were synthesised and characterised. These compounds have been characterised by
spectral (1HNMR, 13CNMR, FTIR, mass, AAS) methods, elemental analyses, molar
conductivity, magnetic susseptibility and thermal analysis (TG, DTG and DTA) techniques.
The studies described here allow us to conclude that Co(III) and Ni(II) coordination can
be used to induce opening reactions of a tetrahydroquinazoline ring.
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EXPERIMENTAL
Materials and measurements
All chemicals and solvents were purchased from Merck, Aldrich or Lachema and were
used without further purification.
Melting points were determined on a BÜCHI B540 digital melting point apparatus and
remained uncorrected. The molar conductivities of the complexes were measured by using a
WTW model inoLab 730 conductivity meter. Magnetic susceptibility measurements were
performed at room temperature with a Sherwood Scientific MK1 model Magnetic Susceptibility
Balance. C, H and N microanalyses, metal analyses and mass spectra were carried out at the
Technical and Scientific Research Council of Turkey, TUBITAK Bursa Test and Analysis
Laboratory. FTIR spectra were recorded in the 4000400 cm1 region with a ThermoNicolet
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6700 FourierTransform Infrared Spectrometer by using KBr pellets. The HNMR and C
NMR solution spectra were recorded at 25 °C on a Varian Mercury Plus 400 MHz spectrometer,
utilising deuterated dimethylsulphoxide (DMSOd6) as a solvent. Thermal analysis curves (TG,
DTG and DTA) were obtained using a Seiko Exstar 6200 thermal analyser in a dinamic dry air
atmosphere (flow rate of 200 mL min-1) at a heating rate of 10 °C min1 in the temperature range
of 251000 °C using platinum crucibles.
Oxoptolylacetaldehyde oxime, pMeINAP
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Oxoptolylacetaldehyde oxime (pmethyl isonitrosoacetophenone), pMeINAP, was
prepared according to a literature method[19] with little modification. Nitrosation of
1ptolylethanone with butyl nitrite afforded the corresponding α-carbonyl oxime, pMeINAP.
Structure of pMeINAP was inferred from its FTIR and NMR spectral data. The bands
observed at 3422, 2905, 1676, 1598 and 979 cm−1 were attributed to the
α–carbonyl
oxime ν(O−H), ν(H–C=N), ν(C=O), ν(C=N) and ν(N−O) groups stretching vibrations,
1
respectively. The HNMR spectrum of pMeINAP displayed signals at δ 12.63 (s, 1H, OH,
disappeared upon addition of D2O), 8.01 (s, 1H, CH=N), 7.88 (d, J=8 Hz, 2H, CHaromatic), 7.31
(d, J=8.4 Hz, 2H, CHaromatic) and 2,36 (s, 3H, CH3) ppm. In the 13C−NMR spectrum of
pMeINAP, the signals appeared at δ 188.70, 148.13 and 21.64 ppm were attributed to the
carbon atoms of carbonyl, azomethine and methyl groups. The pMeINAP displayed a range of
aromatic carbon resonances between δ 144.72–129.42 ppm.
Synthesis of 2(ptolyl)1,2,3,4tetrahydroquinazoline2carbaldehyde oxime, HL
A solution of 2-aminobenzylamine (2ABA), (10.0 mmol, 1.22 g) in 5 mL of absolute
ethanol was added dropwise to a solution of pMeINAP (10.0 mmol, 1.63 g) in 15 mL of
absolute ethanol. The reaction mixture was stirred for 2 h at room temperature and left for one
day at room temperature. The reaction product was filtered, washed with cold ethanol and finally
dried under vacuum (Scheme 1). Yield: 1.68 g, 63 % (white crystals). m.p.: 152 °C
(decomposition). Anal. Calc. for C16H17N3O (267.3 g mol1) (%): C, 71.88; H, 6.41; N, 15.72.
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Found: C, 71.60; H, 6.48; N, 16.03. FT–IR (KBr pellet) νmax cm–1: 3393, 3213 s, sh (N–H); 2748
1
(O–H---N); 2915 (H–C=N); 1607 (C=Noxime); 940 m, sh (N–O). H–NMR (DMSO–d6) δ ppm, J
Hz: 10.80 s, 1H (OH, disappeared upon addition of D2O); 7.38 s, 1H (H–C=N); 7.43 d (J=8.0),
2H (CHaromatic); 7.11 d (J=7.6), 2H (CHaromatic); 6.89 dt (J=8.0, 1.6), 1H (CHaromatic); 6.72–6.69
m, 2H (CHaromatic); 6.43 dt (J=7.2, 1.2), 1H (CHaromatic); 6.58 s, 1H (N(1)H); 3.68 dd (J=18.6,
13
4.8), 1H (CH2); 3.46 dd (J=16.0, 8.4), 1H (CH2); 3.03 b, 1H (N(3)H); 2.24 s, 3H (CH3). C–
NMR (DMSO–d6) δ ppm: 152.69 (H–C=N); 143.50 (C–C<N ); 140.71–114.75 (Caromatic); 70.82
N
(>C<N ); 42.80 (CH2); 21.05 (CH3). m/z: 267.8 [HL]+.
N
H C
3
H C
3
1
HN
O
H N
2
2
3
+
N
H
-H2O
H N
2
H
N
H
N
OH
OH
Scheme 1. Synthesis of HL.
Synthesis of [Co(L)2]Cl
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A solution of CoCl2⋅6H2O (1.50 mmol, 0.37 g) in ethanol (10 mL) was added dropwise
while stirring at room temperature to a solution of HL (3.00 mmol, 0.80 g) in ethanol (20 mL).
Airoxidation was achieved by stirring vigorously on air for 5 h. After 5 h, the precipitated
orangecoloured compound was filtered, washed with cold ethanol several times, and dried
under vacuum. The complex was named bis{(2aminobenzylimino)ptolylacetaldehyde
oximato}cobalt(III) chloride (Figure 1). Yield: 0.21 g, 22 %. m.p.: 212 °C (decomposition).
Anal. Calc. for C32H32N6O2CoCl (627.0 g mol1) (%): C, 61.30; H, 5.14; N, 13.40; Co, 9.40.
Found: C, 61.00; H, 5.09; N, 12.87; Co, 9.06. FT–IR (KBr pellet) νmax cm–1: 3422 (NH2); 2917
1
(H–C=N); 1612 w (C=Nimine); 1583 w (C=Noxime); 1029 w (N–O); 454 w (M–N). H–NMR
(DMSO–d6) δ ppm, J Hz: 6.87 s, 2H (H–C=N); 7.52–7.42 m, 8H (CHaromatic); 7.24–7.04 m, 10H
(CHaromatic); 6.54 2H (NH2); 4.86 d (J=14.4), 2H (CH2); 4.77 d (J=14.4), 2H (CH2); 2.43 s, 6H
(CH3). 13C–NMR (DMSO–d6) δ ppm: 174.54 (Ph–C=N); 140.82 (H–C=N); 139.69–123.25
(Caromatic); 53.55 (CH2); 21.57 (CH3). m/z: 626.7 [Co(L)2Cl]+. µeff: diamagnetic. Molar
conductance (methanol, ΛM ohm−1cm2mol−1): 83.
Synthesis of [Ni(HL)2]Cl2
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A solution of NiCl2·6H2O (3.00 mmol, 0.71 g) in ethanol (10 mL) was added dropwise
while stirring at room temperature to a solution of HL (3.00 mmol, 0.80 g) in ethanol (20 mL).
The mixture was then stirred for 3 h at room temperature. After 3 h, the precipitated
pinkcoloured compound was filtered and washed with cold ethanol several times, and dried.
The complex was named bis{(2aminobenzylimino)ptolylacetaldehyde oxime}nickel(II)
chloride (Figure 1). Yield: 0.63 g, 62 %; m.p.: 208 °C (decomposition). Anal. Calc. for
C32H34N6O2NiCl2 (664.2 g mol1) (%): C, 57.86; H, 5.16; N, 12.66; Ni, 8.84. Found: C, 57.60;
H, 5.11; N, 12.30; Ni, 8.92. FT–IR (KBr pellet) νmax cm–1: 3412 (NH2); 3190 (OH); 2949 (H–
C=N); 1611 w (C=Nimine); 1580 w (C=Noxime); 958 w (N–O); 478 w (M–N). m/z: 591.7
[Ni(L)2]+; 396.8 [Ni(HL)Cl2]+. µeff: 2.90. Molar conductance (methanol, ΛM ohm−1cm2mol−1):
148.
Figure 1
RESULTS AND DISCUSSION
The principal ligand HL was synthesised by the direct condensation of pMeINAP with
2ABA and reacted with Co(II) and Ni(II) chlorides, one compound was obtained in each
reaction, [Co(L)2]Cl and [Ni(HL)2]Cl2, respectively. The FTIR spectrum of the solid form of
HL and the NMR spectra of the HL in DMSOd6 solution indicate that the ligand remains in ring
form. The heterocyclic ring of the ligand was opened during the complexation and an aniline
type chain form occurred within the complexes. The overall results conclude that the complexes
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consist of two openchain ligand and the openchain amineimineoxime acts as a tridentate
ligand through amine, imine and oxime nitrogen atoms. It was determined that cobalt(II) is
becoming oxidised to cobalt(III) in the [Co(L)2]Cl compound.
The molecular structure of new ligand and its amineimineoxime complexes have been
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13
characterized by HNMR, CNMR, FTIR, mass spectra, AAS, elemental analyses, thermal
analyses, molar conductivity and magnetic susseptibility measurements and the results are given
in the Experimental Section.
Elemental Analysis, AAS, Magnetic Susceptibility and Conductance
The elemental analyses and AAS results are in reasonably good agreement with the
proposed structures. The magnetic susceptibility measurement of the cobalt(III) complex reveals
that the compound is diamagnetic, confirming the oxidation of cobalt(II) to cobalt(III) and
structure’s octahedral geometry[15,17,18]. The effective magnetic moment of [Ni(HL)2]Cl2 is 2.90
B.M. for per nickel(II) ion, which corresponds to two unpaired electrons of a mononuclear
octahedral Ni(II) complex. The molar conductance values of [Co(L)2]Cl and [Ni(HL)2]Cl2,
measured in methanol solutions (~1 x 103 M), show that the Co(III) and Ni(II) complexes are
1:1 and 1:2 electrolytes, respectively[20]
.
Mass Spectra
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The mass spectra of the ligand and open–chain tautomer Co(III) complex of this ligand
confirmed the suggested formula by their molecular ion peaks. The mass spectrum of the free
ligand that shows a molecular ion peak at m/z = 267.8 [HL]+ indicates the formation of the
desired structure. The peak at m/z = 626.7 at the mass spectrum of the cobalt(III) complex can be
attributed to the [Co(L)2Cl]+ ions. The mass spectrum of the nickel(II) complex shows peaks at
m/z = 591.7 and 396.8 corresponding to [Ni(L)2]+ and [Ni(HL)Cl2]+ ions, respectively.
FT-IR Spectra
The FT−IR spectrum of HL exhibited fairly strong bands at 3393, 3213 cm−1 attributable
to the ν(N−H) vibration. The bands observed at 2915, 1607 and 940 cm−1 were attributed to the
oxime ν(H–C=N), ν(C=N) and ν(N−O) groups stretching vibrations, respectively. The oxime (
OH) stretching vibration of HL appeared as a broad peak maximum at 2748 cm–1, which was
assigned to the intramolecular hydrogen bonding vibration (N····H–O–). In addition, in the FT
IR spectrum of the carbonyl oxime derivative pMeINAP, the (C=O) stretching frequency of
the carbonyl group appeared at 1676 cm1 but disappeared in the presence of the 1,2,3,4–
tetrahydroquinazoline oxime, HL, demonstrating the formation of the new ligand.
In the FT–IR spectrum of the complexes, the bands at 3422 and 3412 cm−1 are attributed
to ν(NH2) of the amineimineoxime ligand for [Co(L)2]Cl and [Ni(HL)2]Cl2, respectively. In
the FT–IR spectrum of the Co(III) complex, there is no ν(O–H) band belonging to the oxime
group, providing evidence for its deprotonation. On the other hand, in the FT–IR spectrum of the
Ni(II) complex, the band at 3190 cm–1 was associated with the (O–H) stretching vibrations. A
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band around 1612–1611 cm–1 is attributable to the (C=Nimine) stretching vibration in the spectra
of the Co(III) and Ni(II) complexes, which is absent in the spectra of the free ligand, indicating
the coordination in the chain form. When the FT–IR spectra of the complexes are compared with
those of the free ligand, the new ν(C=Nimine) band is appeared and the ν(C=Noxime) band is shifted
to a lower frequency. These situations indicate that the imine and oxime nitrogen atoms must be
coordinated to the metal ion. The (N–O) of the oxime group vibration in the Co(III) complex is
situated at a frequency significantly higher (~89 cm1) than that of the free ligand, owing to the
coordination of the N atom and the increase in bond order of the N–O bond upon deprotonation.
NMR Spectra
13
1H and CNMR spectra of the HL and openchain tautomer Co(III) complex of this
1
ligand are summarised in Experimental Section. The HNMR spectrum of the ligand showed
three peaks as singlets at δ 10.80, 3.03 ppm and δ 6.58 ppm, which disappeared upon addition of
D2O and were assigned to the proton of the oxime group, the NH proton adjacent to the –CH2
group and the other NH proton, respectively. The signals of the phenyl groups of the ligand are
determined at ca. δ 7.43−6.43 ppm, the aldehyde proton adjacent to the oxime group resonated at
δ 7.38 ppm and the signal corresponding to the resonance of methyl group protons showed at
2.24 ppm as a singlet. The resonances observed at 3.68 ppm and 3.46 ppm as an AB system was
assigned to the –CH2 group in the heterocyclic ring.
In the 13C−NMR spectrum of pMeINAP, the signal of the carbon atom of carbonyl
group appeared at 188.70 ppm but disappeared in the 13C−NMR spectrum of the
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1,2,3,4−tetrahydroquinazoline oxime, which was evidence for the formation of new ligand. In
addition, the ligand showed a signal corresponding to the quaternary carbon atom of the
heterocyclic ring at δ 70.82 ppm, suggesting that the 1,2,3,4tetrahydroquinazoline ring is
formed[14, 15, 17,18]. In the 13C−NMR spectrum of the HL, the signal at δ 152.69 ppm is attributed
to the carbon atoms of HC=NOH group. The HL displayed a range of aromatic carbon
resonances between δ 143.50114.75 ppm. As for the carbon atoms of methylene and methyl
groups in the ligand, they were observed at δ 42.80 ppm and δ 21.05 ppm, respectively.
1
A comparison of the HNMR and 13CNMR spectra of the ligand with the Co(III)
complex confirms the coordination of the aniline-type chain form of the ligand. In the 1H−NMR
spectrum of the Co(III) complex, the signal due to the –NOH group is absent and evidence for
deprotonation of oxime group.
The chemical shift belonging to the –NH adjacent to the –CH2 group in the HL
1
disappeared from the HNMR spectrum of the Co(III) complex. After the complexation, the
1
integrated HNMR spectrum of the Co(III) complex indicated proton resonances at ca. δ 6.54
ppm due to the presence of the –NH2 group of imine oxime. The D2O exchangeable peak was
assigned by the formation of the aniline-type chain form in the Co(III) complex (Figure 1). In the
Co(III) complex, the peaks due to the HC=N group and methylene group of the HL showed an
upfield shift and a downfield shift upon complexation with Co(III)[15,17,18], respectively. This
finding confirmed that the nitrogen atoms of the oxime group and imine group were coordinated
to the metal ion. Additionaly, the phenyl and methyl protons are seen as multiplets at δ
7.52−7.04 ppm and as a singlet at δ 2.43 ppm, respectively.
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The chemical shift due to the quaternary carbon atom in HL disappeared from the
13C−NMR spectrum of Co(III) complex. However, after complexation a new resonance at δ
174.54 ppm was observed. The new resonance shows us that the heterocyclic ring of the ligand
was opened during the complexation and the aniline type chain form occured in the Co(III)
complex15. The chemical shifts belonging to the carbon atoms of oxime group and methylene
group in the HL showed an upfield shift and a downfield shift on complexation with Co(III).
1
These results substantiate the conclusion obtained by the HNMR study and demonstrate the
involvement of the oxime nitrogen and the nitrogen adjacent to the –CH2 group in coordination.
Thermal Analyses
Thermal stability data of the ligand and the complexes of its openchain tautomer are
listed in Table 1. The HL is stable up to 105 °C and then exhibits three exothermic
decomposition stages. Decomposition is completed at 636 °C (Figure 2).
The Co(III) and Ni(II) complexes don't contain hydrated or lattice water molecules,
which are consistent with the analytical and spectroscopic data. The Co(III) complex is thermally
stable up to approximately 131 °C (Figure 3). After exceeding this temperature, the organic
ligands start to decompose. Decomposition occurs in the temperature range of 131–604 °C in
three steps, as shown by exothermic DTA peaks at 209, 431 and 530 °C. The mixture of
Co3O4/CoO is caused by the removal of the organic ligands and halogen. The decomposition
product Co3O4 is converted to CoO between 604 and 961 °C (DTAmax: 898 °C)[21]. The weight
loss of 90.0 % suggests that the final product may be CoO.
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TGDTA curves for the Ni(II) complex are given in Figure 4. The complex shows three
exothermic stages in the decomposition process. The total mass loss of the decomposition steps
amounts to 87.8 % (calcd.: 88.7 %) for the Ni(II) complex. It corresponds to the removal of the
HL ligands and chlorides leaving NiO as a residue.
ACKNOWLEDGEMENT
This work was supported by the Technical and Scientific Research Council of Turkey,
TUBITAK (Project No. 106T371) and the Research Foundation of Uludağ University (Project
No. 2006/66).
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Table 1. TG–DTA data of HL and the complexes of its open-chain tautomer.
Compound
Temperatur DTAmax, °C
Total weight loss
Calculated,
Assignment
e
Found, 
range, °C

*
**
**
HL
105  180
180  401
154()
343()
495()
545()
578()
13.3
52.6
*
100

401  636
100
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[Co(L)2]Cl
131  221
221  464
464  604
604  961
148  216
209()
431()
530()
898(+)
201()
309()
448()
525()
23.5
34.8
88.9
90.0
16.1
*
*
**
**
*
Co3O4/CoO
CoO
88.1
*
[Ni(HL)2]Cl2
**
216  461
461  555
34.0
87.8
*
**
88.7
NiO
(+): endothermic, (): exothermic, * :not computed, **: unknown
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FIGURE CAPTIONS
Figure 1. Suggested structures for the Co(III) and Ni(II) complexes.
H3C
1
H2N
3
N
1 NH2
2
.Cln
M
3
N
N
H
2
N
(HO)O
(HO)O
CH3
H
Figure 2. TG, DTG and DTA curves of HL.
3.000
100.0
200.0
150.0
100.0
50.0
2.500
80.0
2.000
60.0
1.500
1.000
40.0
0.500
20.0
0.000
0.0
0.0
-0.500
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
Temperature (C)
Figure 3. TG, DTG and DTA curves of [Co(L)2]Cl.
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110.0
6.000
100.0
250.0
200.0
150.0
100.0
50.0
5.000
90.0
80.0
4.000
70.0
3.000
60.0
50.0
2.000
40.0
1.000
30.0
0.0
20.0
0.000
10.0
-50.0
-1.000
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
Temperature (C)
Figure 4. TG, DTG and DTA curves of [Ni(HL)2]Cl2.
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120.0
10.00
250.0
200.0
150.0
100.0
50.0
9.00
100.0
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
80.0
60.0
40.0
20.0
0.0
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
Temperature (C)
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