Full text of DOI:10.4314/bcse.v32i1.10

Bull. Chem. Soc. Ethiop. 2018, 32(1), 111-124.
 2018 Chemical Society of Ethiopia and The Authors
DOI: https://dx.doi.org/10.4314/bcse.v32i1.10
ISSN 1011-3924
Printed in Ethiopia
SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF N-(2-{[(2E)-2-(2-
HYDROXYBENZYLIDENE)HYDRAZINYL]CARBONYL}-PHENYL)BENZAMIDE
(HL) AND ITS Co(II), Fe(III), Cu(II) AND Zn(II) COMPLEXES. X-RAY CRYSTAL
STRUCTURE OF HL
Rasool Khan1*, Aydin Tavman2*, Demet Gürbüz2, Mohammad Arfan3 and Adem Çinarli2
1Institute of Chemical Sciences, University of Peshawar, Peshawar, 25120, Pakistan
2Istanbul University, Faculty of Engineering, Chemistry Department, Avcilar, 34320, Istanbul,
Turkey
3H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological
Sciences (ICCBS) University of Karachi, Karachi, 75270, Pakistan
(Received November 11, 2017; Revised January 21, 2018; Accepted January 23, 2018)
ABSTRACT. N-(2-{[(2E)-2-(2-hydroxybenzylidene)hydrazinyl]carbonyl}phenyl)benzamide (HL) and its
Co(II), Fe(III), Cu(II) and Zn(II) perchlorate complexes were synthesized. The structures of HL and its complexes
were confirmed on the basis of elemental analysis and FT-IR, FT-Raman, 1H-NMR spectra. TGA, magnetic
moment and molar conductivity measurements were carried out for the complexes. In addition, the crystal
structure of HL was determined by X-ray diffraction at room temperature. It crystallizes in the monoclinic, space
group C2/c and Z=4. HL has an interesting structure due to the presence of two intramolecular hydrogen bonds. It
behaves as a bidentate ligand through the C=N nitrogen and OH oxygen atoms in its chelate complexes that they
have 1:2 M:L (metal:ligand) ratio. The Fe(III), Cu(II) and Zn(II) complexes, [Fe(HL)(L)(H2O)2](ClO4)2,
[Cu(HL)2](ClO4)2∙3H2O, [Zn(HL)2](ClO4)2·H2O are 2:1 electrolytes whereas the Co(II) complex,
[Co(HL)(L)(H2O)]ClO4·H2O, is 1:1 electrolyte according to the molar conductivity data.
KEY WORDS: Hydrazine, Hydroxybenzylidene, Benzamide, Metal Complexes, Crystal Structure
INTRODUCTION
Benzamide and its analogues have various application in synthesis of heterocyclic ring skeletons
and are used as intermediate in the synthesis of 2,3-disubstituted quinazolin-4(3H)-one
heterocycles [1]. In addition, benzamides are identified as important structural unit present in
many compounds having potential biological activities, which are extracted from natural
sources. For example, molecules, like proteins which play an essential role in almost all
biological processes such as enzymatic catalysis (nearly all known enzymes are proteins),
transport/storage (haemoglobin), immune protection (antibodies) and mechanical support
(collagen). The benzamide derivatives are also useful for modulation of numerous metabolic
functions including regulation of carbohydrate, protein and lipid metabolism, regulation of
normal growth and/or development, influence on cognitive function, resistance to stress and
mineralocorticoid activity [2, 3].
The hydrazones constitute an important class of biologically active molecules, which have
attracted attention of medicinal chemists due to their wide ranging pharmacological properties
and their potential application as antitumor, antiviral and antiinflammatory agents [4-9]. For
example, several hydrazones and hydrazides of isoniazid had shown good activity against
tubercular, fungal, bacterial and mycobacterial infections [10-15]. Some of hydrazones
exhibited potential in vitro leishmanicidal activity [16]. It was reported that substituted N’-(2-
oxoindolin-3-ylidene)-benzohydrazides, isatin derivatives, had apoptosis inducers as potential
__________
*Corresponding author. E-mail: atavman@istanbul.edu.tr
This work is licensed under the Creative Commons Attribution 4.0 International License

112
Rasool Khan et al.
anticancer agents. Apoptosis, or programmed cell death, plays a crucial role in normal cell
development and tissue homeostasis [17].
Structural characterization of benzohydrazides is important to comprehend their effect
mechanisms because of their considerable biological effects. Recently, the crystal structures of
hydrazone compounds have been widely studied [18-21].
In our previous study, the crystal structure of 2-amino-N'-[(1Z)-1-(4-chlorophenyl)-
ethylidene]benzohydrazide was reported [22]. The structure of the compound also was
characterized by elemental analysis, MS, FT-IR and NMR spectroscopic techniques. In this
study, we synthesized and characterized N-(2-{[(2E)-2-(2-hydroxybenzylidene)hydrazinyl]-
carbonyl}phenyl)benzamide (HL, Figure 1), a new benzohydrazide derivative, and its Co(II),
Fe(III), Cu(II) and Zn(II) complexes. The structure of the compounds is characterized by the
analytical data and FT-IR, FT-Raman, NMR spectroscopy. TGA, magnetic moment and molar
conductivity measurements were carried out for the complexes. In addition, the crystal structure
of HL is determined by X-ray diffraction analysis.
O
O
H
N
N
H
NH
O
Figure 1. The chemical structure of the ligand (HL).
EXPERIMENTAL
Chemicals and apparatus
All chemicals and solvents were of reagent grade from Sigma-Aldrich, Merck, Alfa Easer, Carlo
Erba and Acros Organics and they were used without further purification.
Elemental analysis data were obtained with a Thermo Finnigan Flash EA 1112 analyzer.
Molar conductivity of the complexes was measured on a WTW Cond315i conductivity meter in
DMF at 25 ºC. Magnetic moment measurements for the paramagnetic complexes were carried
out on a Sherwood Scientific apparatus (MK1) at room temperature by Gouy’s method. FT-IR
spectra were recorded on a Bruker Optics Vertex 70 spectrometer using ATR (Attenuated Total
Reflection) techniques. The FT-Raman spectra were also recorded in the same instrument with a
R100/R RAMII Raman module equipped with Nd:YAG laser source operating at 1064 nm line
with 200 mW power and a spectral resolution of ±2 cm–1. Thermogravimetric (TG) study was
made on a TG-60WS Shimadzu, with a heating rate of 10 ºC/min under flowing air at the rate of
1
50 mL/min. H-NMR spectra were run on a Varian Unity Inova 500 NMR spectrometer in
CDCl3.
Synthesis of the compounds
N-(2-{[(2E)-2-(2-Hydroxybenzylidene)hydrazinyl]carbonyl}phenyl)benzamide (HL). To the
well stirred solution of salicylaldehyde (0.1 mL, 0.8196 mmol) in dry ethanol (10 mL) was
added 2-3 drops of sulfuric acid (98%) and stirred with gentle heating for 30 min followed by
addition of ethanolic solution of 2-phenyl-4H-3,1-benzoxazin-4-one (0.2 g, 7.84 mmol, Scheme
1). The mixture was further refluxed with continuous stirring for one hour; the progress of the
reaction was monitored with TLC upon completion of the reaction. The mixture was allowed to
cool to room temperature, and was then poured into ice cold water. The product precipitated was
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N-(2-{[(2E)-2-(2-hydroxybenzylidene) hydrazinyl]carbonyl}-phenyl)benzamide complexes 113
filtered, washed with 5% cold NaHCO3 solution, dried and recrystallized from ethanol (239
mg).
Yield: 81%, m.p.: 224-226 oC. Anal. calcd. for C21H17N3O3 (%): C, 70.18; H, 4.77; N, 11.69;
found (%): C, 70.08; H, 5.07; N, 11.67. MW: 359.4 g/mol. MS (ESI), m/z (%): 358.2 ([M-1]+,
100), 359.2 ([M]+, 23.4), 393.7 (16.0), 420.7 (15.2), 340.1 (5.1), 240.2 (4.0). FT-IR (ATR,
/cm–1): 3284 br, 3198 m, 3054 m, 2849 w, 1667 m, 1650 m, 1605 m, 1519 m, 1450 m, 1282 m,
1254 m, 961 m, 875 m, 758 s, 699 m, 665 m, 617 m, 513 m, 445 w. FT-Raman (/cm–1): 3068
w, 1659 m, 1609 s, 1574 m, 1554 m, 1487 m, 1452 m, 1295 m, 1242 m, 1173 m, 1032 m, 1004
1
m, 926 w, 897 w, 77 s. H-NMR (CDCl3) δH, ppm: 11.19 (s, 2H, –CO–NH–N=C, –CO–NH–
Ph), 11.10 (s, 1H, OH), 9.17 (s, 1H, CH=N), 8.61 (d, 1H, J=8.4), 7.94 (d, 1H, J=7.3), 7.81 (dd,
2H, J = 8.5, 8.7), 7.68 (m, 3H), 7.49 (t, 1H, J = 8.0), 7.21 (d, 1H, J = 8.1), 7.12 (t, 2H, J = 7.6),
6.97 (d, 1H, J = 8.1), 6.93 (t, 1H, J = 8.4).
[Fe(HL)(L)(H2O)2](ClO4)2. 135 mg HL (0.375 mmol) and 173 mg Fe(ClO4)3∙6H2O (0.375
mmol) were dissolved in acetonitrile (20 mL) and the mixture was refluxed for 2 h. The mixture
was filtered and kept at room temperature for slow evaporation. After 2 days, the black crystals
were formed and filtered, dried at room temperature (150 mg).
Yield: 81%, m.p. 200-205 oC (explosion!). Anal. calcd. for C42H37Cl2CuN6O16 (%): C,
50.02; H, 3.70; N, 8.33; Found (%): C, 50.44; H, 4.18; N, 9.26. MW: 1008.52 g/mol; μeff = 4.20
BM; Molar conductivity: 134 –1cm2mol–1 (in DMF, 25±1 ºC). FT-IR (ATR, /cm–1): 3322 m,
br, 3223 m, br, 3065 m, br, 2997 w, 2859 w, 1736 m, 1641 m, 1604 m, 1587 m, 1515 m, 1448
m, 1384 m, 1300 m, 1258 m, 1105 s, 1052 s, 897 m, 755 m, 705 m, 621 s, 518 m, 432 m.
o
Raman data could not be obtained. TGA (temperature, C: weight loss, %): 100: 2.1; 150: 5.3;
200: 7.3; 219: explosion!
[Co(HL)(L)(H2O)]ClO4·H2O. 135 mg HL (0.375 mmol) and 137 mg Co(ClO4)2∙6H2O (0.375
mmol) were dissolved in acetonitrile (20 mL) and the mixture was refluxed for 2 h. The mixture
was filtered and kept at room temperature for slow evaporation. After 2 days, a brown
precipitate was formed. This precipitate was filtered and dried at room temperature (147 mg).
Yield: 78%, m.p. 215 oC. Anal. calcd. for C42H37ClCoN6O12 (%): C, 55.30; H, 4.09; N, 9.21;
Found (%): C, 56.25; H, 4.62; N, 9.68. MW: 912.10 g/mol. μeff = 3.31 BM. Molar conductivity:
87 –1cm2mol–1 (in DMF, 25±1 ºC). FT-IR (ATR, /cm–1): 3325 w, 3235 m, br, 3062 m, br,
3003 w, br, 2850 w, br, 1736 m, 1682 m, 1604 m, 1590 m, 1522 m, 1448 m, 1389 m, 1325 w,
1275 m, 1118 m, 1054 s, 895 m, 761 s, 688 s, 621 s, 515 m, 423 m. Raman data could not be
obtained. TGA (temperature, oC: weight loss, %): 100: 2.1; 150: 3.05; 200: 3.7; 250: 13.05; 300:
23.2; 350: 42.4; 400: 51.1; 450: 54.3; 500: 57.1; 550: 69.5; 600: 92.2; 650: 92.7 (CoO%: 8.38).
[Cu(HL)2](ClO4)2·3H2O. 135 mg HL (0.375 mmol) and 140 mg Cu(ClO4)2∙6H2O (0.375 mmol)
were dissolved in acetonitrile (20 mL). A green turbidity was formed instantly. This mixture
was refluxed for 2 h, then cooled to room temperature and filtered. The green precipitate was
dried at room temperature (155 mg).
Yield: 80%, m.p. 273 oC (explosion!). Anal. calcd. for C42H40Cl2CuN6O17 (%): C, 48.73; H,
3.89; N, 8.12; Found (%): C, 48.13; H, 3.49; N, 8.11. MW: 1035.25 g/mol. μeff = 1.56 BM.
Molar conductivity: 142 –1cm2mol–1 (in DMF, 25±1 ºC). FT-IR (ATR, /cm–1): 3361 m, 3187
w,br, 3062 m,br, 2888 w,br, 1679 m, 1627 m, 1604 m, 1582 m, 1554 m, 1509 s, 1445 m, 1393
m, 1336 m, 1275 m, 1216 m, 1152 m, 1074 m, 1040 s, 904 m, 744 m, 694 m, 621 m, 535 m, 443
o
m. Raman data could not be obtained. TGA (temperature, C: weight loss, %): 100: 4.2; 150:
4.4; 200: 4.4; 270: explosion!
[Zn(HL)2](ClO4)2·H2O. 135 mg HL (0.375 mmol) and 140 mg Zn(ClO4)2∙6H2O (0.375 mmol)
were dissolved in acetonitrile (20 mL). A slightly yellow turbidity was formed at one minute.
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This mixture was refluxed for 2 h, then cooled to room temperature and filtered. The dirty white
precipitate was dried at room temperature (140 mg).
Yield: 74%, m.p. 180-194 oC. Anal. calcd. for C42H36Cl2N6O15Zn (%): C, 50.39; H, 3.62; N,
8.39; Found (%): C, 50.33; H, 4.25; N, 8.39. MW: 1001.08 g/mol; Molar conductivity: 110
–1cm2mol–1 (in DMF, 25±1 ºC). MS (ESI): 781.2 ([(Zn+2HL)-3]+, 100%), 783.2 ([(Zn+2HL)-
1]+, 70.6%), 785.2 ([(Zn+2HL)+1]+, 56.0%), 786.2 ([(Zn+2HL+2)]+, 28.8%), 719.3
([(2HL)+1]+, 17.6%), 360.2 ([HL+1]+, 58.8%), 422.0 ([(HL+Zn)-3]+, 44.1%), 424.0 ([(HL+Zn)-
1]+, 32.1%). FT-IR (ATR, /cm–1): 3342 m, br, 3266 m, 3095 w, br, 2883 w, br, 1686 m, 1666
m, 1616 m, 1590 m, 1560 m, 1518 m, 1448 m, 1398 m, 1280 m, 1110 m, 1074 m, 1038 s, 976
m, 756 s, 705 m, 619 m, 591 m, 515 m. FT-Raman (/cm–1): 3076 w, 1667 w, 1611 s, 1589 m,
1
1561 m, 1455 m, 1326 m, 1281 m, 1168 m, 1138 m, 1052 w, 1003 w, 936 m, 89 m. H-NMR
(CDCl3) δC, ppm: 11.94 s, br (1H, OH), 11.69 s, br (1H, –CO–NH–N=C), 11.10 (s, br, 1H, 1H, –
CO–NH–Ph), 9.64 s, br (1H, CH=N), 8.71 d (1H, J=7.8), 8.47 s, br (1H), 8.06 d (2H, J = 6.8),
7.58 m (5H), 7.07 d, br (1H, J = 9.7), 6.97 t (3H, J = 6.83, 7.32). TGA (temperature, oC: weight
loss, %): 100: 1.6; 150: 2.1; 200: 2.9; 250: 7.8; 300: 20.0; 350: 35.5; 400: 46.1; 450: 49.0; 500:
52.4; 550: 55.3; 600: 79.3; 650: 89.8; 700: 91.3 (ZnO%: 8.0).
O
NH
2
O
NH
O
H
N
C2H5OH / H2SO4
Salicylaldehyde
N
H
NH
O
O
NH
Scheme 1. Synthesis of N-(2-{[(2E)-2-(2-hydroxybenzylidene)hydrazino]carbonyl}phenyl)
benzamide (HL).
Crystallography
Suitable crystal was selected for data collection which was performed on a Bruker SMART
APEX CCD area-detector diffractometer with graphite monochromated Mo-Kα radiation (λ =
0.71073 Å) at 251 oC (298 K). The structures were solved by direct methods using SHELXS-
97 and refined by full-matrix least-squares methods on F using SHELXL-97 [23]. All non-
hydrogen atoms were refined with anisotropic parameters. The H atoms of C atoms were located
from different maps and then treated as riding atoms with C–H distances of 0.96 – 0.97 Å. H
atoms treated by a mixture of independent and constrained refinement. For the structure
solution, 9402 reflections were collected, 3530 were unique (Rint = 0.066); equivalent reflections
were merged. Lorentz-polarization and absorption corrections were applied using Bruker
SAINT [24] and SADABS [25] software. The crystal structure was deposited at the Cambridge
Crystallographic Data Centre under the following deposition number: CCDC 1538433.
RESULTS AND DISCUSSIONS
Discussion of the ligand structure
Synthesis of the ligand (HL) was given in Scheme 1. The structure of HL was confirmed by the
characteristic absorption peaks of amide in IR region, D2O exchangeable amide proton peak in
the 1H-NMR region and further confirmation was done on the basis of molecular ion peak in EI-
MS, FAB-MS and Mass fragmentation pattern. It is important to note that HL did not cyclize
further under the selected reaction conditions.
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N-(2-{[(2E)-2-(2-hydroxybenzylidene) hydrazinyl]carbonyl}-phenyl)benzamide complexes 115
In addition to spectroscopic proof of the structure, crystals of HL were obtained and the
absolute structure was determined with the help of X-ray crystallography, which confirmed the
formation and reactivity of the open chain products.
The crystal data and details of data processing are given in Table 1. Table 2 contains the
hydrogen bond geometry parameters. Selected bond lengths and angles are given in Table 3;
some torsion angles are given in Table 4. The ORTEP III drawing of HL is given in Figure 2
and the unitcell packing diagram with the intermoleculer H-bonding is given in Figure 3.
Table 1. Crystal and experimental data and refinement of the crystal structure of HL.
Empirical formula
C21H17N3O3
Formula weight (g/mol)
Crystal system, Space group
Color, habit
359.38
Monoclinic, C2/c
Colorless, block
a = 21.191(17), b = 8.308 (7)
c = 22.333 (18),  = 113.093 (16)
3617 (5)
Unit cell dimensions (Å, o)
Cell volume (Å3)
Z, dcalc. (g/cm3)
F(000)
8, 1.320
1504
Crystal size (mm)
0.43 × 0.42 × 0.12
1
-
0.09
Linear abs. coefficient (mm 
No. of observations (I>2.00 σ (I))
Refinement method
Goodness of fit indicator
Index ranges
1574
Full-matrix least-squares on F
0.98
-26  h  25, -7  k  10, -27  l  27
1.9  26.0
SMART
0.058
 range for data collection (o)
Data collection
R [F2 > 2σ(F2)]
wR(F2)
0.144
-
3
0.15 and -0.14
Largest diff. peak and hole (e /Å )
Table 2. Hydrogen-bond geometry (Å, °)
D–H···A
D–H
0.85(3)
0.83(3)
0.87(3)
0.93
H···A
1.97(2)
1.85(3)
1.99(3)
2.60
D···A
D–H···A
144(2)
149(3)
164(3)
145
N1–H1A···O2
O3–H3A···N3
N2–H2A···O1i
C4–H4···O3ii
C17–H17···O2iii
2.707(4)
2.597(4)
2.837(4)
3.399(5)
3.291(5)
0.93
2.46
149
Symmetry codes: (i) x+3/2, y+1/2, z; (ii) −x+1/2, −y+1/2, −z; (iii) x, y−1, z.
There are two intra- and three inter-molecular hydrogen bonds in the HL molecule (Table
2). The intermolecular hydrogen bonding distances are 1.99, 2.60 and 2.46 Å, for
N2H2A···O1, C4H4···O3 and C17H17···O2, respectively. The intermolecular H-bonding
values for C4–H4···O3 and C17–H17···O2 (2.60 and 2.46 Å, respectively) are higher than the
ordinary intermolecular H-bonding lengths as expected due to very weak electron-withdrawing
characteristic of the aromatic CH hydrogen atoms. The crystal structure is stabilized by the
intermolecular hydrogen bondings. The intramolecular hydrogen bonding distances,
(N1H1A···O2: 1.97(2) Å; O3H3A···N3: 1.85(3) Å), are in agreement with the literature data
[21, 26-30]. The intramolecular hydrogen bonds cause forming almost two more rings in the
molecule. It is expected that the intramolecular hydrogen bonds affect the physical properties of
HL, significantly. It is not a very common feature that there are hydrogen bonds in a molecule
more than one.
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Rasool Khan et al.
Figure 2. The ORTEP III drawing of HL.
Figure 3. The ORTEP III drawing of HL showing the stability via hydrogen bonding between
the molecules.
The major torsion angles: C1-C6-C7-N1: 25.0(4); C7-N1-C8-C9: 20.4(4); C12-C13-C14-
N2: -36.1(3); N3-C15-C16-C17: -178.8(2)º (Table 4). According to the torsion angles, the
benzamide ring is twisted by 25º according to the phenyl ring at the middle of HL whereas the
phenyl ring is twisted by the angle of 36.1º compared to the benzamide ring. Some of the
considerable bond lengths are: C6-C7-N1: 115.2(2); C7-N1-C8: 129.3(2); C13-C14-N2:
115.0(2); C14-N2-N3: 118.5(2); N2-N3-C15: 118.0(2); N3-C15-C16: 120.5(3)º. The bond
angles at the bridging parts between three rings are varying at the 115.0  129.3º range (Figure
3).
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N-(2-{[(2E)-2-(2-hydroxybenzylidene) hydrazinyl]carbonyl}-phenyl)benzamide complexes 117
Table 3. Selected bond lengths (Å) and angles (º)
Bond lengths, Å
O1–C7
O2–C14
O3–C21
N1–H1A
N3–C15
C1–C6
C6–C7
C11–C12
C15–C16
1.231(3)
1.229(3)
1.350(3)
0.855(10)
1.274(3)
1.350(3)
1.489(4)
1.377(4)
1.442(4)
O3–H3A
N1–C7
N1–C8
N2–C14
N2–N3
C5–C6
C10–C11
C13–C14
C9–H9
0.828(10)
1.346(3)
1.403(3)
1.349(3)
1.370(3)
1.363(4)
1.370(4)
1.476(4)
0.9300
Bond angles, º
C21–O3–H3A
C7–N1–C8
C14–N2–N3
O2–C14–C13
O1–C7–N1
N1–C7–C6
C9–C8–N1
O3–C21–C16
106(2)
C15–N3–N2
O2–C14–N2
N2–C14–C13
N3–C15–C16
O1–C7–C6
C1–C6–C7
C13–C8–N1
O3–C21–C20
118.0(2)
121.5(3)
115.0(2)
120.5(3)
121.7(3)
123.1(3)
117.9(2)
116.5(3)
129.3(2)
118.5(2)
123.5(3)
123.1(3)
115.2(2)
123.1(3)
123.3(3)
The C=O bond lengths are very close to each other: 1.231(3) and 1.229(3) Å for C7O1 and
C14O2, respectively. The C–OH (C21O3) bond length (1.350(3)) is higher than the average
length of C=O bond as expected. The C7–N1 bond length (1.346(3) Å) is shorter than that of the
C8–N1 (1.403(3) Å) due to the C7 carbon atom bonded to the carbonyl oxygen atom (O=C7–
N1). Oxygen atom makes the C7–N1 bond shorter than C8–N1 because of its electron-
withdrawing characteristic. The C14N2 and C15N3 bond lengths are 1.349(3) Å and 1.274(3)
Å, respectively. It is obvious that the second one is a double bond. The bond length of N2N3 is
1.370(3) Å and it is a single bond as expected.
Table 4. Selected torsion angles (º)
C14-N2-N3-C15
N1-C8-C13-C14
N3-N2-C14-C13
C8-C13-C14-N2
C7-N1-C8-C13
N2-N3-C15-C16
C7-N1-C8-C9
174.5(2)
1.4(3)
C12-C13-C14-O2
N3-N2-C14-O2
C12-C13-C14-N2
C1-C6-C7-N1
N3-C15-C16-C17
C5-C6-C7-N1
143.3(3)
-3.7(4)
-36.1(3)
25.0(4)
-178.8(2)
-156.9(2)
175.8(2)
145.7(2)
-161.0(2)
177.0(2)
20.4(4)
Properties of the complexes
Molar conductivity data of the complexes give useful information about the structure of the
complexes. According to the molar conductivity data, the Fe(III), Cu(II) and Zn(II) complexes
(110 – 142 –1cm2mol–1) are considered as 1:2 and the Co(II) complex is acceptable as 1:1 (87
–1cm2mol–1). According to Geary, molar conductivity values for 1:1 and 1:2 electrolyte in
DMF generally fall between 65 – 90 and 130 – 170 –1cm2mol–1, respectively [31]. Elemental
analysis and molar conductivity data shows that one of the ligands releases a phenolic hydrogen
in the Co(II) complex and [Co(HL)(L)(H2O)]ClO4·H2O is suggested for the empirical formula
of the Co(II) complex.
Room temperature magnetic moment values (μeff) of the paramagnetic complexes are 1.65,
4.20 and 3.31 BM for the Cu(II), Fe(III) and Co(II) complexes, respectively. Magnetic moment
value of Cu(II) complex (1.65 BM) is in the expected range for a typical mononuclear d9 Cu(II)
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Rasool Khan et al.
complex. The room temperature effective magnetic moment value of the Fe(III) complex
indicates stabilization of the species having intermediate ferric spin (S = 3/2) state. The
occurrence of such an intermediate spin state is typical for the six and five coordinate ferric
complexes [32-34]. The room temperature magnetic moment value of Co(II) complex, 3.31 BM,
lower than the spin-only value for high spin and higher than the spin-only value for low spin
configurations. This may be considered as a spin equilibrium between two spin states [35] and it
can be attributed a square pyramidal geometry for this complex nearly [36, 37].
The experimental data of the Co(II) and Fe(III) complexes suggest us monodeprotonated
structure in contradistinction to the Cu(II) and Zn(II) complexes. The dark color of the
complexes, especially the Fe(III) and Co(II) complexes, shows that there are charge transfer
transitions ligand to metal ions through phenolic oxygen atom, O→M [38, 39].
Thermogravimetric analysis
The major features of the thermal analysis of the complexes are given in Experimental section.
TGA curves of the Co(II) and Zn(II) complexes are given in Figure 4. The decomposition points
o
of the complexes are in the 180  273 C range. In this range, explosions were occurred in the
Fe(III) and Cu(II) complexes due to presence of the perchlorate anion. Because of the explosion,
TGA analysis could not be performed for these complexes fully. However, we could detect the
coordinated and uncoordinated water molecules in the complexes by means of TGA. The
uncoordinated lattice water molecules were lost through evaporation from 50 to 100 ºC
(dehydration) in the Cu(II) and Zn(II) complexes whereas the coordinated water molecules
(aqua) were removed at temperatures near 150 ºC in the Fe(III) and Co(II) complexes. The full
TGA data of the Co(II) and Zn(II) complexes could be obtained without explosion (Figure 4)
between 40 and 800 oC.
Figure 4. TGA curves of the Co(II) and Zn(II) complexes.
Thermal degradation of the complexes occurred at three stages. Firstly, uncoordinated lattice
water left at the 50 – 100 ºC range as mentioned above. At the second stage, a considerable
weight losses observed between 200 and 400 ºC can be explained in terms of cleavage of
hydroxyl, NHs and carbonyl groups. Above 500 ºC, all other organic parts of complexes are
oxidized to carbon dioxide and water. Complete decomposition of the complexes continues up
to 600 ºC probably to the forming of MO. Molecular weight ratio of the amount of metal oxide
shows very good agreement for the proposed structures according to the TGA data in the Co(II)
and Zn(II) complexes.
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N-(2-{[(2E)-2-(2-hydroxybenzylidene) hydrazinyl]carbonyl}-phenyl)benzamide complexes 119
1H-NMR Spectra
1H-NMR spectral data of the ligand and the Zn(II) complexes are given in Experimental Section.
The phenolic OH and CH=N protons give singlet at 11.10 and 9.17 ppm, respectively, in the
ligand. In the Zn(II) complex, the OH signal shifted to 11.94 ppm from 11.10 ppm; the CH=N
proton shifted to 9.64 ppm from 9.17 ppm with respect to the ligand. These data showed that the
phenolic OH oxygen and the CH=N nitrogen atoms coordinated to the Zn(II) ion, and the OH
proton did not remove on complexation (The other data such as elemental analysis, molar
conductivity, also confirm that the OH proton does not remove on complexation). The hydrazine
(–CO–NH–N=C) and benzamide (–CO–NH–Ph) NH protons of the ligand appear at 11.19 ppm
as a singlet, respectively. These NH protons exhibit different behavior in the Zn(II) complex:
The NH proton of hydrazine that neighbor to the coordinated imine nitrogen (–NH–CH=N)
gives a singlet at 11.69 (from 11.19), whereas the benzamide NH proton (far from the
coordinated imine nitrogen) is slightly affected from coordination (it gives a singlet at 11.10
ppm). This observation is considered as an additional evidence for CH=N nitrogen atom
coordination.
Vibrational Spectroscopy
FT-IR and FT-Raman spectral data of the compounds are given in Experimental section. The
FT-IR spectra of the ligand and the complexes are given in Figure 5. FT-Raman spectra of HL
and the Zn(II) complex were shown in Figure 6. We could not get the FT-Raman spectra of the
Cu(II), Co(II) and Fe(III) complexes (Raman inactive).
In the IR spectra of the ligand, the medium bands at 1650 and 1667 cm–1 must belong to the
C=O groups. The corresponding wavenumbers in the complexes are detected at the 1617 – 1736
cm–1 range. In the Raman spectra, the 1653 cm–1 and 1667 cm–1 bands can be assigned for the
ν(C=O) group of the ligand and the Zn(II) complex, respectively. The medium (IR) and strong
(Raman) bands between 1604 – 1616 cm–1 are attributed to the aromatic ring (CC)
frequencies. There are no considerable changes in these frequencies on complexation as
expected. Similarly the (CN) asymmetric stretching frequency of the ligand is appeared at
1519 cm1, and it was detected at the 1582 – 1590 cm1 range in the complexes. This
considerable shifting shows that the coordination occurs through the C=N nitrogen atom.
The strong bands between 761 and 744 cm–1 (in the ligand: 758 cm–1), and the strong or
medium bands at the 830 – 730 cm–1 range are due to the out-of-plane deformation bands for the
aromatic C–Hs. The bands at 3284 cm–1 (w, br) and 3198 cm–1 (m, br) can be attributed to
(OH) and (NH) in the ligand, respectively. These bands shifted to the 3322 – 3361 cm–1 and
3187 – 3266 cm–1 ranges in the complexes, respectively.
In the FT-IR spectra of all the complexes, the new strong band between 1105 and 1152 cm–1
can be assigned to the stretching vibrations of the uncoordinated perchlorate anion, (Cl=O). In
addition, the medium bands in the complexes near 620 cm–1 are due to ν4 mode of perchlorate
anion [40-42].
The broad band between 3000-2500 cm–1 in the complexes should be belonged to the
hydrogen bonding because of the coordinated and uncoordinated (lattice) water molecules. The
characteristic (C–H) modes of ring residues are observed in the range of 3054 – 3095 cm–1, in
the FT-IR and FT-Raman spectra of the compounds (Figures 5 and 6).
Bull. Chem. Soc. Ethiop. 2018, 32(1)

120
Rasool Khan et al.
Figure 5. FT-IR spectra of HLL and its complexes.
Figure 6. FT-Raman spectra o
f
f
HL and its Zn(II) complex.
CONCLUSION
Benzamide and its analogu
skeletons and are used as inte
benzamide derivatives can be
e
e
s have various applications in synthesis of heterocycli
c
c
ring
some
er
mediate in the synthesis of some heterocycles. In addition
,,
e
xtracted from plants having potential biological activities.
Bull. Chem. Soc. Ethiop. 2018, 32(1)

N-(2-{[(2E)-2-(2-hydroxybenzylidene) hydrazinyl]carbonyl}-phenyl)benzamide complexes 121
In this study,
a new benzamide derivative, N-(2-{[(2E)-2-(2-hydroxybenzylidene)-
hydrazinyl]carbonyl}phenyl)-benzamide (HL) and its complexes with Co(ClO4)2, Fe(ClO4)3,
Cu(ClO4)2 and Zn(ClO4)2 were synthesized and characterized. In addition, the crystal structure
of HL is determined by X-ray diffraction at room temperature. According to the analytical and
spectral data, HL behaves as a bidentate in the chelate complexes; and the complexes have 1:2
M:L ratio. According to the molar conductivity measurements in DMF, the Fe(III), Cu(II) and
Zn(II) complexes are 2:1 electrolytes whereas the Co(II) complex can be considered as 1:1
electrolyte.
As a conclusion, the structures in Figure 7 can be proposed for the complexes. It can be
proposed a tetrahedral geometry for the Cu(II) and Zn(II) complexes; distorted octahedral and
square pyramidal geometries for the Fe(III) and Co(II) complexes, respectively [43-47]. In
addition, the ball-stick structure for the Cu(II) and Zn(II) complexes is shown in Figure 8.
-
ClO4
OH
-
ClO4
N
NH
O
NH
M
O
N
NH
O
NH
O
nH2O
OH
M=Cu, n=3; M=Zn, n=2
-
O
ClO4
H2O
-
N
NH
O
ClO4
NH
Fe
O
NH
N
O
NH
O
OH2
OH
OH
Co+
H2O
N
-
ClO4
H2O
N
NH
O
NH
O
NH
O
NH
O
O
Figure 7. The proposed structures for the complexes.
Bull. Chem. Soc. Ethiop. 2018, 32(1)

122
Rasool Khan et al.
Figure 8. The ball-stick structure for the Cu(II) and Zn(II) complexes (the structures were
obtained by ACD/ChemSketch software program (the H2O molecules and the
perchlorate anions are omitted).
ACKNOWLEDGEMENT
This work was supported by the Scientific Research Projects Unit of Istanbul University and
TUBITAK-BIDEB.
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