Synthesis and spectroscopic characterization of Zr(IV) and Th(IV) with chelating containing ONNO donor quadridentate Schiff bases complexes

Article abstract of DOI:10.1080/15533174.2013.862694

New metal complexes of novel Schiff bases derived from the reaction of zirconium (IV) and thorium (IV) ions with N,N′-disalicylidene-l,2-phenylenediamine (H₂dsp), N,N′-disalicylidene-3,4-diaminotoluene (H₂dst), 4-nitro-N,N-disalicyli

Full text of DOI:10.1080/15533174.2013.862694

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Synthesis and Spectroscopic Characterization of Zr(IV)
and Th(IV) With Chelating Containing ONNO Donor
Quadridentate Schiff Bases Complexes
Moamen S. Refatab, Samy M. El-Megharbelac & Abdel Majid A. Adama
a Department of Chemistry, Faculty of Science, Taif University, Al-Haweiah, Taif, Saudi
Arabia
b Department of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt
c Department of Chemistry, Faculty of Science, Zagazig University, Egypt
Accepted author version posted online: 25 Sep 2014.
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To cite this article: Moamen S. Refat, Samy M. El-Megharbel & Abdel Majid A. Adam (2015) Synthesis and Spectroscopic
Characterization of Zr(IV) and Th(IV) With Chelating Containing ONNO Donor Quadridentate Schiff Bases Complexes, Synthesis
and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 45:9, 1300-1306, DOI: 10.1080/15533174.2013.862694
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry (2015) 45, 1300–1306
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2013.862694
Synthesis and Spectroscopic Characterization of Zr(IV)
and Th(IV) With Chelating Containing ONNO Donor
Quadridentate Schiff Bases Complexes
MOAMEN S. REFAT1,2, SAMY M. EL-MEGHARBEL1,3, and ABDEL MAJID A. ADAM1
1Department of Chemistry, Faculty of Science, Taif University, Al-Haweiah, Taif, Saudi Arabia
2Department of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt
3Department of Chemistry, Faculty of Science, Zagazig University, Egypt
Received 7 September 2013; accepted 10 October 2013
New metal complexes of novel Schiff bases derived from the reaction of zirconium (IV) and thorium (IV) ions with N,N0-
disalicylidene-l,2-phenylenediamine (H2dsp), N,N0-disalicylidene-3,4-diaminotoluene (H2dst), 4-nitro-N,N-disalicylidene-1,2-
1
phenylenediamine (H2ndsp) were prepared and characterized based on elemental analyses, IR and H NMR spectroscopy, molar
conductance, and thermal analyses. The complexes are formed in 1:1 [Metal]:[Ligand] ratio. The molar conductance measurements
proved that all these complexes are non-electrolytes. The IR spectra of the ligands and their complexes are used to identify the type
of bonding. The thermogravimetric analysis of the complexes shows metal oxide remaining as the final product.
Keywords: Schiff base, zirconium (IV), thorium (IV)
Introduction
donor atoms[2]; herein, we study the reaction of N,N0-disalicy-
lidene-l,2-phenylenediamine (H2dsp), N,N0-disalicylidene-
Schiff bases are compounds containing an azomethine group 3,4-diaminotoluene (H2dst), 4-nitro-N,N0-disalicylidene-1,2-
(¡CDN¡) have drawn attention for many years ago. They phenylene-diamine (H2ndsp) with Zr(IV) and Th(IV) ions.
are capable of forming coordinate bonds with many metal The products were characterized. The products were structur-
ions through both azomethine group and phenolic group or ally characterized using elemental analysis, infrared (IR), and
via its azomethine or phenolic group.[1–3] Their metal com- 1H NMR. Finally, the thermal behavior of the obtained com-
plexes have been studied, with a variety of transition metal plexes was also investigated.
ions, as they frequently exhibit unusual structural properties.
These properties have resulted in wide applications in the bio-
logical field including antitumor, antibacterial, fungicidal,
and anticarcinogenic properties.[4–6] Some Schiff base com-
plexes are also used as model molecules for biological oxygen
carrier systems as well as having applications in analytical
fields.[7,8] The most important step in the development of
metal complexes was perhaps the preparation of a new
ligand, which exhibit unique properties and novel reactivity.
Because of the electron donor and electron acceptor proper-
ties of the ligand, structural functional groups and the posi-
tion of the ligand in the coordination sphere together with the
reactivity of coordination compounds may be a factor of dif-
ferent studies.[9–14] In continuation of our ongoing research
on the development of new Schiff base complexes derived
from N,N0-bridged tetradentate ligands involving an N2O2
Experimental
Chemicals and Instruments
All of the chemicals used were of high reagent grade and were
used without further purification. Zr(IV) sulfate and Th(IV)
nitrate were purchased from the BDH Chemical Company
and were used without further purification. Carbon, hydro-
gen and nitrogen content were determined using a Perkin
Elmer CHN 2400 in the Microanalytical Unit at the Faculty
of Science, Cairo University, Egypt. The metal content was
found gravimetrically by converting the compounds into their
corresponding oxide. IR spectra were recorded on Bruker
FT-IR spectrophotometer (400–400 cm¡1) in KBr pellets.
Molar conductivities of freshly prepared 1.0 £ 10¡3
mol dm¡3 DMSO solutions were measured using Jenway
4010 conductivity meter. 1H-NMR spectra were recorded on
Varian Gemini 200 MHz spectrometer using DMSO-d6 as
solvent and TMS as an internal reference. Thermogravimet-
ric analysis (TGA and DTG) was carried out in dynamic
Address correspondence to Moamen S. Refat, Box 888, Zip
Code 21974, Taif, Saudi Arabia. E-mail: msrefat@yahoo.com
Color versions of one or more of the figures in the article can be
found online at www.tandfonline.com/lsrt.

ONNO Donor Quadridentate Schiff Bases Complexes
1301
Sch. 1. Chemical Structure of the H2dsp, H2dst and H2ndsp ligands.
nitrogen atmosphere (30 mL/min) with a heating rate of ligand was prepared by dissolving 25 mmol (3.050 g) of 3,4-
10ꢀC/min. using Shimadzu TGA-50H thermal analyzer.
diaminotoluene in 100 mL of ethanol and stirred for 3 h.
After that, 50 mmol (6.106 mL) of salicylaldehyde was mixed
in 150 mL of ethanol. The 3,4-diaminotoluene solution was
added to the salicylaldehyde solution using an overhead
stirred for complete mixing. Some yellow precipitate resulted.
The crude product was re-crystallized from dichlorome-
thane/hexane (1:2) mixed solvent.
Procedures
Synthesis of the ligands
The H2dsp, H2dst, and H2ndsp ligands (Scheme 1) were pre-
pared by Garg and Kumar method.[15,16] All the tetradentate
Table 1. Elemental analysis and physical data of the complexes
Content: (Calcd.) Found (%)
Compound
M (wt%)
C
H
N
Metal
Lm (V¡1 cm¡1 mol¡1
)
[Zr(dsp)(SO4)(H2O)].2H2O
[Th(dsp)(NO3)2].H2O
[Zr(dst)(SO4)(H2O)].4H2O
[Th(dst)(NO3)2].H2O
555.22
688.0
605.22
702.0
733.0
(43.23) 43.29
(34.88) 34.81
(41.64) 41.60
(35.9) 35.77
(32.74) 32.72
(2.5) 2.6
(5.04) 5.0
(16.43) 16.40
(33.72) 33.75
(15.07) 15.0
(33.05) 33.1
(31.65) 31.68
17.40
20.50
18.70
20.40
60.40
(2.33) 2.29
(4.30) 4.33
(2.56) 2.61
(2.05) 2.03
(8.14) 8.17
(4.63) 4.65
(7.98) 7.97
(9.55) 9.51
[Th(ndsp)(NO3)2].H2O
Schiff base ligands except H2dst were prepared by condensa-
tions between diamines and hydroxyaldehydes in ethanol or
methanol and were purified by recrystallization from a
dichloromethane/hexane mixed solvent through the partial
evaporation of the more volatile dichloromethane. The H2dst
Synthesis of the metal complexes
One mmol of each metal salt; Zr(IV) or Th(IV) was dissolved
in methanol, and 1 mmol of requisite ligand was suspended
in hot methanol and stirred for 1 h. The methanolic solutions
Table 2. IR frequencies (cm¡1) of the free ligands and their complexes
Assignment
Compound
nas(OH) H2O
n(OꢁꢁH)
n(CHN)
n(CꢁꢁN)
n(ph-O)
n(MꢁꢁN)
n(MꢁꢁO)
H2dsp
H2dst
H2ndsp
[Zr(dsp)(SO4)(H2O)].2H2O
[Th(dsp)(NO3)2].H2O
[Zr(dst)(SO4)(H2O)].4H2O
[Th(dst)(NO3)2].H2O
[Th(ndsp)(NO3)2].H2O
—
—
—
3400
3390
3430
3400
3420
2500–2680
2550–2750
2650–2750
1614
1617
1635
1615
1617
1630
1610
1627
1403
1401
1372
1464
1380
1420
1383
1447
1325
1350
1313
1307
1304
1320
1302
1379
—
—
—
530
538
530
585
473
—
—
—
444
467
436
467
409
—
—
—
—
-

1302
Refat et al.
Fig. 1. (a) IR spectrum of [Zr(dsp)(SO4)(H2O)].2H2O complex. (b) IR spectrum of [Th(dsp)(NO3)2].H2O complex. (c) IR spectrum of
[Zr(dst)(SO4)(H2O)].4H2O complex. (d) IR spectrum of [Th(dst)(NO3)2].H2O complex. (e) IR spectrum of [Th(ndsp)(NO3)2].H2O
complex.
Table 3. 1H NMR spectral dataa (d, ppm)b of the free H2dsp ligand and [Zr(dsp)(SO4)(H2O)].2H2O
Compound
(OH) phenolic
N D CH
Aromatic protons
H2dsp
12.95
8.58
7.1–7.4, 6.8–7.03
H2dst
H2ndsp
[Zr(dsp)(SO4)(H2O)].2H2O
13.14, 13.08
12.52, 12.45
—
8.58, 8.57
8.73, 8.65
8.72
7.26–7.36, 6.94–7.11, 6.70–6.90
8.14–8.24, 7.30–7.46, 6.90–7.08
7.6–7.0, 6.97–6.4
aSolvent DMSO-d6.
bRelative to TMS.

ONNO Donor Quadridentate Schiff Bases Complexes
1303
Fig. 2. (a) The TGA and DTG of [Zr(dsp)(SO4)(H2O)].2H2O complex. (b) The TGA and DTG of [Th(dsp)(NO3)2].H2O complex. (c)
The TGA and DTG of [Zr(dst)(SO4)(H2O)].4H2O complex. (d) The TGA and DTG of [Th(dst)(NO3)2].H2O complex.
of the metal ion were added to methanolic Schiff base solu- in H2O and most of organic solvents except for DMSO and
tions and the resulting mixtures were refluxed for 3 h and DMF.
evaporate to half. After cooling, the microcrystalline solids
were filtered off, washed with hot methanol, and dried at
60ꢀC.
Molar Conductance Measurements
Conductivity measurements have frequently been used in
structural studies of metal chelates within the limits of their
solubility. They provide a method of testing the degree of ion-
Results and Discussion
ization of the complexes, the molar ions that a complex liber-
ates in solution, the higher will be its molar conductivity and
Elemental Analysis Results
The elemental analysis (C, H, and N) results and some physi- vice versa.[17] The molar conductivities of 1.0 £ 10¡3 mol
cal characteristics of the obtained complexes are shown in dm¡3 solutions (DMSO solvent) of the free ligands and their
Table 1. The results indicate that all complexes are formed in complexes are measured and the data obtained are listed in
1:1 [Metal]:[Ligand] ratio. The complexes are air-stable, Table 1. The molar conductance values of the free ligands
hygroscopic, with higher melting points (>300ꢀC), insoluble were in the range 4.46–6.90 V¡1 cm¡1 mol¡1, while those of

1304
Refat et al.
Table 4. Thermal decomposition data for the complexes
% Weight loss
Complex
Tmax (ꢀC)
Calcd.
Found
Assignment
3H2O
[Zr(dsp)(SO4)(H2O)].2H2O
180
400
—
200
390
—
200
477
560
—
300
590
—
9.7
52.9
37.0
11.6
22.1
66.3
14.1
23.8
11.36
50.44
2.5
32.6
64.8
8.7
44.0
47.4
9.4
52.9
37.1
11.59
22.5
66.2
14.48
23.5
12.0
49.72
1.8
33.0
65.0
8.72
45.7
47.3
C13H14N2O4S
ZrO2 C 7C residue
H2O C NO2
[Th(dsp)(NO3)2].H2O
C4H14N3O4
ThO2 C 16C residue
[Zr(dst)(SO4)(H2O)].4H2O
5H2O
C3H6NO2 C SO2
C3H8N2
ZrO2 C 16C residue
[Th(dst)(NO3)2].H2O
[Th(ndsp)(NO3)2].H2O
H2O
C5H17N4O6
ThO2 C 16C residue
180
240
—
H2O C NO2
C13H14N2O6
ThO2 C7C residue
the complexes were in the range 15–60 V¡1 cm¡1 mol¡1. It is 1H NMR Spectra
concluded from these results that that the complexes are con-
The nuclear magnetic resonance spectra provide evidence of
the complexation pathway. The 400 MHz H NMR spectra
sidered as non-electrolytes. These low molar conductance
values indicate their nonionic nature. The higher values of
the complexes than that of the corresponding ligands indicate
the formation of complexes and the presence of sulfate or
nitrate ion.
1
of the free H2dsp ligand and its complex with Zr(IV) were
measured in DMSO-d6 at room temperature. The chemical
shift (d, ppm) of the different protons has been recorded in
1
Table 3. The H NMR spectrum of all the Schiff bases pro-
vides completing evidence of the presence of either one or
two azomethine groups. Due to different chemical environ-
ments two signals are recorded for the azomethine protons in
the H2dst and H2ndsp ligands, whereas, the H2dsp ligand
gives one signal. By comparing the 1H NMR spectra of
H2dsp ligand and [Zr(H2dsp)(SO4)(H2O)].2H2O complex, it
is noted that there is a downfield sift in the frequency of azo-
methine protons of aromatic bridge and upfield shift in the
aliphatic bridge confirming coordination of the metal ion to
both groups. In the complex, no signal is recorded for pheno-
lic hydrogen in the 12–13.5 ppm region, as in the case of the
Schiff base indicating deprotonation of the orthohydroxyl
group.
Infrared Spectra
The infrared absorption spectra of the free ligand and their
complexes were recorded in the frequency range 4000–
400 cm¡1 using a KBr disc, and their characteristic bands are
provided in Table 2. The full IR spectra of the obtained com-
plexes are shown in Figure 1a–e. All the complexes contain-
ing water molecules, so they exhibited characteristic medium
intensity absorption bands in the region 3200–3500 cm¡1 [18]
.
The spectra of the ligands exhibited broad medium intensity
bands in the 2500–3360 cm¡1 range that are attributed to the
. . .
intramolecular H-bonding vibration (O¡H N), while in the
spectra of the complexes these bands were disappeared.
The vibrations of the azomethine groups of the free ligands
Thermal Analyses
were observed at the range (1610–1640 cm¡1). These bands To determine the formula and structure of the new com-
were shifted to higher frequencies in the complexes, indicat- plexes, thermogravimetric analysis (TG and DTG) was per-
ing that the nitrogen atom of the azomethine group is coordi- formed for these complexes over a temperature range of 25–
nated to the metal ion.[2,19] In the ligands spectra, the bands 700ꢀC under a static air atmosphere. The TG curves were
observed at the range of 1311–1350 cm¡1, which can be redrawn with the mg mass loss as a function of temperature.
assigned to the phenolic (CꢁꢁO) group vibrations,[19] were Figure 2 shows the thermograms for the complexes, whereas
shifted toward higher or lower frequency in the complexes Table 4 provides the thermal analysis data of these com-
spectra, indicating chelation of oxygen to the metal ions. In plexes. The obtained data strongly support the structures
all the complexes, the bands at 473–585 and 409–467 cm¡1 proposed for the complexes. The thermal decomposition of
range can be attributed to the n(M-N) and n(M-O) modes, [Zr(dsp)(SO4)(H2O)].2H2O complex occurs at two steps.
respectively.
The first degradation step take place in the range of 50–

ONNO Donor Quadridentate Schiff Bases Complexes
1305
Sch. 2. Proposed structures of H2dsp, H2dst and H2ndsp complexes (where x D H, CH3 or NO2).
180ꢀC and it is corresponds to the elimination of three water corresponding to the loss of H2O C NO2 molecules. The
molecules due to a weight loss of 9.7% in a good matching second stage representing a weight loss of 45.7% and its
with theoretical value 9.4%. The second step fall in the calculated value is 44%, corresponding to the loss of
range of 180–380ꢀC, which is assigned to loss of C13H14N2O6 (organic moiety). The final product resulted
C13H14N2O4S with a weight loss 52.91%, and the calcu- at 700ꢀC contains of ThO2 polluted with a few carbon
lated value is 52.92%. The ZrO2 (Figure 3) is the final prod- atoms. The reported data dealing in the thermal analysis
uct remains stable until 700ꢀC with few carbon atoms. The within nitrogen atmosphere indicate that the complexes
thermal decomposition of [Th(dsp)(NO3)2].H2O complex decompose to give metal oxide contaminated with carbon
completely occurs in two steps. The first step ranged at 50– atoms as final products. This reason, because of no suffi-
200ꢀC corresponding to the loss of NO2 and H2O mole- ciently of oxygen atoms help to evolved carbon as carbon
cules, representing a weight loss of 11.59% and its calculated monoxide or dioxide.
value is 11.6%. The second step ranged at 200–400ꢀC corre-
sponding to the loss of C4H14N3O4, representing a weight
loss of 22.50% and its calculated value is 22.1%. The ThO2
(Figure 3) is the final product remains stable until 700ꢀC
with few carbon atoms. The [Zr(dst)(SO4)(H2O)].4H2O
complex decomposed in three steps. The first step extended
from 50 to 200ꢀC and can be assigned to the loss of 5H2O
molecules, representing a weight loss of 14.2% and its calcu-
lated value is 15%. The second step occurring at 326–
477ꢀC corresponding to the loss of C3H6NO2 and SO2,
representing a weight loss of 23.5% and its calculated
value is 23.8%. The final step occurring at 477–560ꢀC,
corresponding to loss of C3H8N2 (organic moiety), repre-
senting a weight loss of 12% and its calculated value is
11.36%. The final products resulted at 700ꢀC contain
ZrO2 polluted with some carbon atoms. The thermal
decomposition of [Th(dst)(NO3)2].H2O complex proceeds
approximately with main two degradation step. The
weight loss associated with the first stage is 1.8% and its
calculated value is 2.5%, corresponding to the loss of one
H2O molecule. The weight loss associated with the second
stage is 33% and its calculated value is 32.6%, correspond-
ing to the loss of C5H17N4O6. The final product results at
700ꢀC contains of ThO2 with a few carbon atoms. The
[Th(ndsp)(NO3)2].H2O complex decomposed in two steps.
The weight loss associated with the first stage is 8.72%,
which is very close to the theoretical value of 8.70, sition for (A) zirconium(IV) and (B) thorium(IV) complexes.
Fig. 3. Infrared spectra of the final residual of thermal decompo-

1306
Refat et al.
Structure of the Complexes
3. Hassan, W. M. I.; Zayed, E. M.; Elkholy, A. K.; Moustafa, H.
Mohamed, G. G. Spectrochim. Acta A 2013, 103, 378.
4. Garnovskii, A. D.; Vasil Chenko, I. S. Russ. Chem. Rev. 2002, 71,
943.
5. Ren, S.; Wang, R.; Komatsu, K.; Bonoz-Krause, P.; Zyrianov, Y.;
McKenna, C. E. J. Med. Chem. 2002, 45, 410.
6. Raman, N.; Thangaraja, A.; Kulandaisamy, C. Trans. Met. Chem.
2003, 28, 29.
The structures of the obtained complexes are confirmed by
elemental analysis, molar conductance, IR and 1H NMR
spectra, and thermal analysis. The proposed structures of
these complexes are shown in Scheme 2.
7. Halve, A.; Samadhiya, S. Orient. J. Chem. 2001, 17, 87.
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Conclusion
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Structural studies of new Zr(IV) and Th(IV) complexes with
three Schiff bases (H2dsp, H2dst, and H2ndsp) were carried
out. It is observed that the reaction stoichiometry is 1:1
1
[Metal]:[Ligand] ratio. The IR and H NMR spectra show
that the Schiff bases acted as dianionic tridentate N2O2
donors attached to the metal acceptor centre through the
deprotonated two phenolic oxygen groups and two azome-
thine nitrogen groups. The proposed structure of the resulted
complexes is six-coordinated fashion.
14. Singh, B. K.; Rajour, H. K.; Prakash, A. Spectrochim. Acta A 2012,
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