Iron(III), nickel(II) and zinc(II) complexes based on acetophenone- S -methyl-thiosemicarbazone: Synthesis, characterization, thermogravimetry, and a structural study

Article abstract of DOI:10.1080/00958972.2015.1086760

New complexes, [Fe(L)Cl], [Ni(L)], and [Zn(L)C2H5OH] (1-3), were synthesized by template reaction of 2-hydroxy-acetophenone-S-methyl-thiosemicarbazone with 2-hydroxy-benzaldehyde. The compounds were characterized by elemental analysis, magnetic measurements, FT-IR, ¹H NMR, UV-visible, and ESI-MS spectra. In these complexes, the ligand is coordinated to the metal ion as dinegatively charged tetradentate chelating agents via the N2O2 donor set. The iron(III) and zinc(II) complexes exhibit square pyramidal geometry whereas the nickel(II) complex has a square planar geometry. The crystal structure of 1, determined by X-ray diffraction method, indicates that 1 crystallizes in the monoclinic space group P21/c with Z = 4. Thermal decompositions of the compounds have been investigated using TGA in air.

Full text of DOI:10.1080/00958972.2015.1086760

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Iron(III), nickel(II) and zinc(II) complexes based
on acetophenone-S-methyl-thiosemicarbazone:
synthesis, characterization, thermogravimetry,
and a structural study
Yasemin Kurt & Nahide Gulsah Deniz
To cite this article: Yasemin Kurt & Nahide Gulsah Deniz (2015) Iron(III), nickel(II) and zinc(II)
complexes based on acetophenone-S-methyl-thiosemicarbazone: synthesis, characterization,
thermogravimetry, and a structural study, Journal of Coordination Chemistry, 68:22, 4070-4081,
DOI: 10.1080/00958972.2015.1086760
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Date: 09 October 2015, At: 04:34

Journal of Coordination Chemistry, 2015
Vol. 68, No. 22, 4070–4081, http://dx.doi.org/10.1080/00958972.2015.1086760
Iron(III), nickel(II) and zinc(II) complexes based on
acetophenone-S-methyl-thiosemicarbazone: synthesis,
characterization, thermogravimetry, and a structural study
YASEMIN KURT*† and NAHIDE GULSAH DENIZ‡
†Division of Inorganic Chemistry, Department of Chemistry, Istanbul University, Istanbul, Turkey
‡Division of Organic Chemistry, Department of Chemistry, Istanbul University, Istanbul, Turkey
(Received 1 February 2015; accepted 6 August 2015)
New complexes, [Fe(L)Cl], [Ni(L)], and [Zn(L)C2H5OH] (1–3), were synthesized by template
reaction of 2-hydroxy-acetophenone-S-methyl-thiosemicarbazone with 2-hydroxy-benzaldehyde. The
compounds were characterized by elemental analysis, magnetic measurements, FT-IR, 1H NMR,
UV–visible, and ESI–MS spectra. In these complexes, the ligand is coordinated to the metal ion as
dinegatively charged tetradentate chelating agents via the N2O2 donor set. The iron(III) and zinc(II)
complexes exhibit square pyramidal geometry whereas the nickel(II) complex has a square planar
geometry. The crystal structure of 1, determined by X-ray diffraction method, indicates that 1
crystallizes in the monoclinic space group P21/c with Z = 4. Thermal decompositions of the
compounds have been investigated using TGA in air.
Keywords: Thiosemicarbazone; Acetophenone; N2O2 complex; Crystal structure; Thermogravimetric
analysis
1. Introduction
The chemistry of thiosemicarbazones has attracted interest primarily due to their biological
activities such as antituberculous [1], antitumor [2], antimicrobial [3], antiviral [4], antioxi-
dant [5], and cytotoxic [6] effects. The biological activity of such compounds is related to
their chelating ability with transition metal ions, a consequence of the unique characteristics
of mixed hard–soft NS donors [7].
Thiosemicarbazones have various coordination modes due to their geometrical flexibility
and polydentate nature. Common metal complexes of thiosemicarbazones have bidentate
*Corresponding author. Email: dasdemir@istanbul.edu.tr
© 2015 Taylor & Francis

Complexes based on a thiosemicarbazone
4071
and tridentate functions through the sulfur, azomethine nitrogen, and hetero atom of an
arylidene moiety [8]. Some tetradentate thiosemicarbazones are synthesized by template
condensation in the presence of transition metal ions. Many template compounds synthe-
sized from S-alkyl-thiosemicarbazones with iron(III), nickel(II) [9–14], zinc(II) [15, 16],
copper(II), cobalt(II) [1, 17, 18], vanadyl(IV) [19], and uranyl(VI) [20] ions have been
investigated.
The N2O2-type metal complexes of bis(arylidene)-S-alkyl-thiosemicarbazones are usually
obtained from substituted 2-hydroxy benzaldehydes, but there are a limited number of such
complexes that include an acetophenone moiety. A few N2O2 complexes obtained by
template reaction of acetophenone thiosemicarbazones and 2-hydroxy benzaldehyde with
copper(II), nickel(II), vanadyl(IV), and uranyl(VI) ions have been reported [21–23].
In this study, iron(III), nickel(II), and zinc(II) complexes (1–3) of tetradentate
N1,N4-diarylidene-S-methyl-thiosemicarbazone ligands were synthesized using 2-hydroxy-
acetophenone-S-methyl-thiosemicarbazone and salicylaldehyde as starting compounds
(figure 1). The new complexes and the starting thiosemicarbazone were characterized by
1
elemental analysis, magnetic measurements, FT-IR, H NMR, UV–visible, ESI–MS spectra,
and thermogravimetric analysis (TGA). The crystal structure of chlorido N1-[(2-hydrox-
yphenyl) ethylidene]-N4-[(2-hydroxyphenyl)methylidene]-S-methyl-thiosemicarbazidato-iron
(III) (1) was determined by X-ray diffraction.
2. Experimental
2.1. Materials and physical measurements
All chemicals were reagent grade and used as commercially purchased without
purification. Elemental analyses were determined on a Thermo Finnigan Flash EA 1112
Figure 1. [Fe(L)Cl] (1), [Ni(L)] (2), and [Zn(L)C2H5OH] (3).

4072
Y. Kurt and N.G. Deniz
Series elemental analyzer. Magnetic measurements were carried out at room temperature
with a Sherwood Scientific MK I apparatus using CuSO4·5H2O as calibrant. IR spectra
were measured on an Agilent Technologies Cary 630 FT-IR-spectrophotometer by means
of attenuated total reflection (ATR) techniques. 1H NMR spectra were recorded on a
Bruker Avance-500 model spectrometer relative to SiMe4 using DMSO-d6. Electronic
spectra of the compounds were recorded in 2 × 10−5 M DMF solution with a Shimadzu
UV-2600 UV–vis spectrophotometer from 200 to 900 nm. The ESI–MS analyses were car-
ried out in positive ion mode using a Thermo Finnigan LCQ Advantage MAX LC/MS/
MS. Thermal degradation experiments were carried out on a Shimadzu TGA-50 thermo-
gravimetric analyzer. A constant heating rate of 10 K min−1 was used between room tem-
perature and 900 °C. The air flow rate was 50 mL min−1 for thermo-oxidative degradation
runs. Sample weights were 16–18 mg in all cases.
2.2. Synthesis of the starting ligand
2-Hydroxy-acetophenone-S-methyl-thiosemicarbazone was prepared with small modifica-
tions of the literature method [24].
H2L1. Light yellow, m.p. 100.6–101.0 °C, 70%. Anal. Calcd for C10H13N3OS
(223.29 g mol−1) (%): C, 53.79; H, 5.87; N, 18.82; S, 14.36. Found: C, 53.58; H, 5.69; N,
19.01; S, 13.99. ATR (selected bands, cm−1): ν(NH)asy 3420, ν(NH)sy 3309, ν(2-OH) 3161,
δ(N4H) 1646, ν(C=N1) 1600, ν(N2=C) 1592, ν(C–O) 1130, ν(C–S) 749. 1H NMR
(500 MHz, DMSO-d6, ppm): 13.33, 13.10 (cis/trans ratio: 2/1, s, 1H, 2-OH), 7.54 (ddd,
J = 16.11, 7.81, 1.46, 1H, d), 7.20 (ddd, J = 14.64, 7.32, 1.46, 1H, b), 6.85 (ddd, J = 14.15,
7.32, 1.46, 1H, c), 6.81 (dd, J = 8.29, 1.46, 1H, a), 6.67 (s, 2H, NH2), 2.43 (s, 3H, S-CH3),
2.40 (s, 3H, C-CH3). UV–vis [λmax (log ε), nm (dm3 cm−1 mol−1)]: 260 (4.29), 293 (4.47),
302 sh. (4.45), 335 (3.52). ESI–MS (positive ion mode), m/z: obsv. 224.52, Calcd 224.08
([M + H]+, 100%); obsv. 115.11, Calcd 115.02 ([M–C6H4OH–CH3]+, 12.48%); obsv. 68.48,
Calcd 68.02 ([M–C6H4OH–SCH3–CH3]+, 5.04%).
2.3. Synthesis of the complexes
[Fe(L)Cl] (1). Complex 1 was prepared with the procedure given in a previous article [11].
2-Hydroxy-acetophenone-S-methyl-thiosemicarbazone (0.223 g, 1 mmol) and 2-hydroxy-
benzaldehyde (0.146 g, 1 mmol) were added dropwise to solution of FeCl3·6H2O (0.27 g,
1 mmol) in 10 mL absolute ethyl alcohol. After a week, black precipitate was filtered off,
washed with a small portion of cold ethanol and diethyl ether, and dried in vacuo.
The nickel(II) and zinc(II) complexes (2 and 3) were synthesized in a similar manner
using Zn(CH3COO)2·2H2O and Cu(CH3COO)2·2H2O salts. The analytical and spectro-
scopic data of 1–3 follow:
[Fe(L)Cl] (1). Black, m.p. > 350 °C, yield 19%, μeff: 5.89 BM. Anal. Calcd for
C17H15N3O2SClFe (416.68 g mol−1) (%): C, 49.00; H, 3.63; N, 10.08; S, 7.70. Found: C,
48.88; H, 3.52; N, 9.88; S 7.60. ATR (selected bands, cm−1): ν(C=N) 1607, 1569 br,
ν(C–O)arom 1153, 1130, ν(C–S) 761. UV–vis [λmax (log ε), nm (dm3 cm−1 mol−1)]: 265
(4.45), 278 (4.40), 300 (4.40), 392 (4.08), 462 (3.89). ESI–MS (positive ion mode), m/z:
obsv. 381.02, Calcd 381.10 ([FeLCl–Cl]+, 100%); obsv. 438.90, Calcd 438.98
([FeLCl + Na]+, 6.53%).

Complexes based on a thiosemicarbazone
4073
[Ni(L)] (2). Claret red, m.p. 314.0–315.6 °C, yield 39%, μeff: 0.26 BM. Anal. Calcd for
C17H15N3O2SNi (384.07 g mol−1) (%): C, 53.16; H, 3.94; N, 10.94; S, 8.35%. Found: C,
53.14; H, 3.91; N, 11.00; S, 8.25. ATR (selected bands, cm−1): ν(C=N) 1615, 1607, 1576,
1
ν(C–O)arom 1169, 1146 ν(C–S) 746. H NMR (500 MHz, DMSO-d6, ppm): 8.28 (s, 1H,
N4=CH), 7.75 (d, J = 8.3, 2H, d,d′), 7.45 (tt, J = 6.83, 1.96, 1H, b′), 7.26 (tt, J = 6.83, 1.46,
1H, b), 6.97 (d, J = 8.79, 1.46, 1H, a′), 6.69 (dt, J = 18.54, 6.83, 2H, c,c′), 2.86 (s, 3H,
S-CH3), 2.74 (s, 3H, –C–CH3). UV–vis [λmax (log ε), nm (dm3 cm−1 mol−1)]: 264 (4.70),
302 (4.49), 323 (4.35), 405 (4.42), 487 (4.02), 560 (3.81). ESI–MS (positive ion mode),
m/z: obsv. 384.20, Calcd 384.03 ([NiL + H]+, 100%); obsv. 406.12, Calcd 406.01
([NiL + Na]+, 22.47%).
[Zn(L)C2H5OH] (3). Orange, m.p. > 350 °C, yield 73%, μeff: diamag. Anal. Calcd for
C17H15N3O2SZn·C2H5OH (436.86 g mol−1) (%): C, 53.16; H, 3.94; N, 10.94; S, 8.35.
Found: C, 53.05; H, 4.08; N, 7.72; S, 5.89. ATR (selected bands, cm−1): ν(C=N) 1610,
1
1598, 1574, ν(C–O)arom 1161, 1142, ν(C–S) 746. H NMR (500 MHz, DMSO-d6, ppm):
8.61 (s, 1H, N4 = CH), 7.59 (dd, J = 8.29, 1.95 1H, d), 7.46 (dd, J = 8.30, 1.95, 1H, d′),
7.37 (ddd, J = 8.79, 6.83, 1.95, 1H, b′), 7.16 (ddd, J = 8.30, 6.83, 1.47, 1H, b), 6.72 (d,
J = 8.79, 1H, a′), 6.71 (d, J = 8.29, 1H, a), 6.54 (td, J = 7.81, 0.97, 1H, c′), 6.50 (td,
J = 8.29, 1.46, 1H, c), 4.61 (t, J = 5.36, ethyl alcohol –OH), 3.61–3.63 (m, 2H, ethyl alco-
hol –CH2), 2.72 (s, 3H, S-CH3), 2.62 (s, 3H, –C–CH3), 1.24 (t, J = 6.34, H, ethyl alcohol –
CH3). UV–vis [λmax (log ε), nm (dm3 cm−1 mol−1)]: 264 (4.46), 307 (4.56), 332 (4.45), 430
(4.33), 473 (4.29). ESI–MS (positive ion mode) m/z: obsv. 390.20, Calcd 390.02
([ZnL + H]+, 100%); obsv. 343.20, Calcd 343.02 ([ZnL–SCH3 + H]+, 5.06%); obsv.
328.30, Calcd 328.00 ([ZnL–SCH3–CH3 + H]+, 4.25%).
2.4. Crystal structure determination and refinement
Single black crystals of 1 for X-ray diffraction analysis were obtained by slow evaporation
of ethanol solution at room temperature. In 1, C17H15N3O2S1Cl1Fe1, having approximate
dimension of 0.55 × 0.40 × 0.10 mm was mounted on a glass fiber. The data were collected
at room temperature to maximum θ values of 30.5° for 1. All measurements were made on
a Rigaku R-Axis Rapid-S imaging plate area detector with monochromated Mo Kα radia-
tion (λ = 0.71070 Å). Experimental conditions are summarized in table 1. The crystal struc-
ture was solved by SIR 92 [25] and refined with CRYSTALS software package [26]. The
non-hydrogen atoms were refined anisotropically. Hydrogens were located in geometrically
idealized positions (C–H = 0.95(6) Å) and treated as riding with Uiso(H) = 1.2Ueq(C). The
selected bond distances, bond and torsion angles for 1 are listed in tables 2–4, respectively.
The conformational angles for 1 are given in table 5. Molecular drawing was performed
with the program ORTEP-III [27] with 50% probability displacement ellipsoids for 1 in
figure 2. The intermolecular hydrogen bond parameters of 1 are illustrated in figure 3.
3. Results and discussion
3.1. Synthesis and physical properties
2-Hydroxy-acetophenone-S-methyl-thiosemicarbazone in form of powder crystals is soluble
in common solvents. Reactions of the thiosemicarbazone with 2-hydroxy-benzaldehyde in

4074
Y. Kurt and N.G. Deniz
Table 1. Crystal data and structure refinement for 1.
Empirical formula
Crystal color, habit
Crystal size (mm)
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
C17H15N3O2S1Cl1Fe1
Black, chunk
0.55 × 0.40 × 0.10
416.69
293.5(2)
0.71073
Monoclinic
P21/c
Space group
Cell dimensions
a = 11.6337(5) Å
b = 8.5945(3) Å
c = 18.0493(9) Å
β = 103.708(3)°
1753.27(13)
4
1.579
1.147
852.00
Cell volume (Å3)
Cell formula units (Z)
DCalcd (g cm−3
)
Absorption coefficient (mm−1
F(0 0 0)
)
h, k, l ranges
−16/16, −12/11, −25/25
12,754
5257 [Rint = 0.069]
4881/0/342
1.181
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit (GOF) on F
Final R indices [I>2σ(I)]
R = 0.046, wR = 0.083
0.042 and −0.042
Largest diff. peak and hole (e Å−3
)
Table 2. The iron(III)-centered bond distances of 1 (Å).
Fe1–O1
Fe1–O2
Fe1–N1
1.864(3)
1.910(2)
2.096(3)
Fe1–N3
Fe1–Cl1
2.076(3)
2.221(1)
Table 3. The Fe(III)-centered angles of 1 (°).
Cl1–Fe1–O1
Cl1–Fe1–O2
Cl1–Fe1–N1
Cl1–Fe1–N3
O2–Fe1–O1
O2–Fe1–N3
O2–Fe1–N1
O1–Fe1–N3
110.66(9)
107.01(8)
101.51(8)
104.00(9)
94.6(1)
86.9(1)
149.3(1)
143.1(1)
O1–Fe1–N1
N3–Fe1–N1
C17–O2–Fe1
C1–O1–Fe1
C9–N3–Fe1
C11–N3–Fe1
C7–N1–Fe1
Fe1–N1–N2
85.7(1)
75.1(1)
132.0(2)
129.1(2)
113.4(2)
127.2(2)
129.2(2)
115.0(2)
the presence of iron(III), nickel(II), and zinc(II) in ethyl alcohol yielded stable complexes as
shown in figure 1. The N2O2 complexes (1–3) form as very fine crystal materials, soluble
in common organic solvents. Complex 1 is stable in air and the magnetic susceptibility val-
ues are compatible with high-spin d5 iron(III) center. The low magnetic susceptibility values
of 2 indicate square planar environment of nickel(II) center in the N2O2 chelate.
3.2. Spectroscopic data
1
3.2.1. 1H NMR spectra. In H NMR spectra of H2L1 and template complexes (2 and 3),
the expected chemical shift values are monitored for aromatic, azomethine, and S-methyl
protons [28]. The 2-OH proton of ligand is observed at 13.33 and 13.10 ppm as two

Complexes based on a thiosemicarbazone
Table 4. Selected torsion angles of 1 (°).
4075
Cl1–Fe1–O2–C17
Cl1–Fe1–O1–C1
O1–Fe1–O2–C17
N3–Fe1–O2–C17
N1–Fe1–O2–C17
O2–Fe1–O1–C1
N1–Fe1–O1–C1
Cl1–Fe1–N3–C11
84.0(3)
−65.7(3)
−162.8(3)
−19.7(3)
−73.3(3)
−175.8(3)
35.0(3)
N3–Fe1–N1–C7
C10–S1–C9–N2
N1–N2–C9–N3
C1–C6–C7–N1
N3–C11–C12–C17
N3–Fe1–O1–C1
Cl1–Fe1–N3–C9
O2–Fe1–N3–C9
−169.1(3)
1.8(3)
−0.8(4)
12.2(5)
−5.0(6)
93.2(3)
83.5(2)
14.6(3)
−92.2(3)
Table 5. Conformational angles (°) for 1 and 1a–b.
Fold of ring 1
Fold of ring 2
Fold of ring 3
Angle between mean
Distance of metal
Complex along Oa⋯Na
along Na⋯Nb
along Ob⋯Nb
planes of phenyl rings
from N2O2 plane (Å)
1
1a
1b
8.6
17.8
19.6
11.7
14.7
18.3
17.9
18.7
18.7
3.4
4.0
7.3
0.55
0.53
0.61
Notes: (1): See figure 3 for key to column headings. M : FeCl, R1 : Me, R2 : Me.
(1a): CCDC entry BOZCEY (Ref. [38]), M : FeCl, R1 : H, R2 : Me.
(1b): CCDC entry CAWCIM (Ref. [39]), M : OFe(L4), R1 : H, R2 : Me (su’s unavailable for these values).
Figure 2. Molecular structure of 1. Displacement ellipsoids are drawn at 50% probability level.
singlets in ratio of 2 : 1 because of cis–trans isomerism. The singlet signal at 6.67 ppm is
assigned to the N4H2 proton resonance. As a result of the template reaction, protons of the
1
phenolic hydroxyl and amine disappear in H NMR spectra of 2 and 3. These data show
that phenolic oxygen loses a proton and a new imine forms by condensation of the free

4076
Y. Kurt and N.G. Deniz
Figure 3. Intermolecular hydrogen bonds of 1.
NH2 group with aldehyde. The imine protons of nickel(II) and zinc(II) complexes appear at
8.28 and 8.61 ppm as sharp singlets, respectively [29]. This new ligand system, N1-[(2-hy-
droxyphenyl)ethylidene]-N4-[(2-hydroxyphenyl)methylidene]-S-methyl-thiosemicarbazidato,
coordinates to metal center through the N2O2 donor set. The chemical shift of the
coordinated ethanol of the zinc(II) complex exhibits an –OH resonance at 4.61 ppm, CH2
resonance at ca. 3.62 ppm and CH3 resonance at 1.24 ppm. In spectra of nickel(II) and zinc
(II) complexes, the aromatic proton signals of aldehyde moiety also confirm the template
structure.
3.2.2. FT-IR spectra. In FT-IR spectra of the thiosemicarbazone, the stretching vibration
bands of OH, N4H2, C=N1, and N2=C groups were clearly observed. Template condensation
of the thiosemicarbazones can be easily monitored by infrared spectra. The ν(OH) and
ν(N4H2) bands are absent in the complex spectra due to coordination of phenolic hydroxyl
by losing proton and the formation of a new ν(C=N) band between thioamide and salicy-
laldehyde. The ν(C=N1) and ν(N2=C) vibrations of ligand are observed at 1600 and
1592 cm−1, respectively. In spectra of 1–3, C=N vibrations are observed at 1615–
1574 cm−1 as three bands of medium intensities, attributed to ν(C=N1), ν(N2=C) and
ν(N4=C). It is difficult to distinguish these imine vibrations. The ν(C=N) frequencies of
ligand shift to lower energies ca. 10–15 cm−1 by chelating and the vibrations of new N4=C
bonds at ca. 1574 cm−1 [30]. The spectrum of the zinc(II) complex displays the ν(OH) and
ν(CH) vibrations of the coordinated ethyl alcohol at 3445 and 2926–2887 cm−1, respec-
tively [31]. Medium bands from 1428 to 1498 and 1327 cm−1 are assigned to aliphatic CH3
and CH2 groups of the ethyl alcohol and S-CH3 group [11, 32].

Complexes based on a thiosemicarbazone
4077
3.2.3. UV–vis spectra. The electronic spectrum of H2L1 shows two absorbtion bands at
260 and 293 nm (with a shoulder at 302 nm) which can be assigned to π → π* transitions
of aromatic ring. These absorptions are also present in the spectra of 1–3 at 264–265 nm
and 278–307 nm, respectively. The n → π* transition associated with azomethine and thioa-
mide region of thiosemicarbazone is found at 335 nm [15, 33]. This band in all complexes
has a red shift. In the complexes, the n → π* transition exhibits blue shift, indicating
coordination of azomethine nitrogen. The electronic spectrum of the nickel(II) complex dis-
plays a band at 405 nm which is due to N → Ni and O → Ni (LMCT) charge-transfer
transitions [21]. Square planar Ni(II) complexes show three spin-allowed transitions,
1
1
1A1g → 1A2g, A1g → 1B1g, and A1g → 1Eg [34]. The more intense charge-transfer band
obscures the A1g → 1Eg transition, and only the A1g → 1A2g and A1g → 1B1g transitions
are observed at 487 and 560 nm, respectively [21, 35]. The zinc(II) complex has two
charge-transfer bands at 430 and 473 nm [15, 36]. The moderately intense broad bands for
the iron(III) complex at 392 and 462 nm are assigned to LMCT transitions. The spin forbid-
den d–d transitions bands are not observed in the 500–700 nm region due to the low band
intensities.
1
1
1
3.2.4. ESI–MS spectra. Characteristic peaks were observed in the ESI–MS of the starting
ligand and metal complexes. The mass spectrum of thiosemicarbazone (H2L1) shows peaks
at m/z 224.52, 115.11, and 68.48 which correspond to [M + H]+, [M–C6H4OH–CH3]+, and
[M–C6H4OH–SCH3–CH3]+, respectively. The most intense peak in the spectrum of iron(III)
complex refers to [FeLCl–Cl]+ ion [37]. The weaker signal at m/z 438.9 can be assigned to
[FeLCl + Na]+ ion. The mass spectrum of Ni(II) complex contains two peaks at m/z 384.20
and 406.12, which can be attributed to [NiL + H]+ and [NiL + Na]+, correspondingly. The
spectrum of zinc(II) complex displays an intense peak at m/z 390.2 due to the [ZnL + H]+
ion. The peaks at m/z 343.2 and 328.3 are assigned to [ZnL–SCH3 + H]+ and [ZnL–SCH3–
CH3 + H]+ ions, respectively, as expected.
3.3. Thermogravimetric analysis
The TGA and derivative thermogravimetric analysis curves for H2L1 and 1–3 are repre-
sented in figure S1 in the supplemental material. The data obtained from thermogram are
given in table 6.
The TG curve of the starting ligand shows an initial 40.3% (Calcd 39.8%) weight loss,
which is in agreement with the removal of NC(S-CH3)-NH2 group at 200–261 °C, followed
Table 6. Thermogravimetric data of the compounds.
Compound
H2L1
Step
Temp. range (°C)
DTG (°C)
Weight loss (%) found (Calcd)
Residue
1st
200–261
261–342
342–698
185–350
350–525
230–400
400–693
130–232
232–308
308–653
240
289
567
268
426
336
482
193
275
401
40.30 (39.80)
26.64 (26.80)
33.06 (34.03)
19.49 (19.81)
61.36 (63.10)
21.36 (22.96)
59.64 (61.75)
10.55 (10.52)
13.62 (14.22)
60.77 (60.25)
2nd
3rd
1st
2nd
1st
2nd
1st
2nd
3rd
1
2
3
Fe2O3
NiO
ZnO

4078
Y. Kurt and N.G. Deniz
by second loss from 261 to 342 °C in which the CH3CN + OH groups of the ligand are
separated with 26.64% (Calcd 26.80%) decrease in weight. The last step (342–698 °C)
shows decomposition of phenyl ring with 33.06% (Calcd 34.03%) weight loss.
The thermal decompositions of iron(III) and nickel(II) complexes take place in two steps.
In the iron(III) complex, the 19.49% (Calcd 19.81%) weight loss corresponding to losses of
S-CH3 + Cl groups occurs at 185–350 °C. The second step with weight loss of 61.36%
(Calcd 63.10%) at 350–525 °C is attributed to loss of the remainder of the organic part.
The final residue is Fe2O3 as indicated by the residual weight of 20.16% (Calcd 21.29%),
which is stable above 525 °C. In the first thermal degradation of the nickel(II) complex, NC
(S-CH3) + Cl groups are eliminated at 230–400 °C with 21.36% (Calcd 22.96%) weight
loss. The rest of the organic moiety is removed in the second step from 400 to 693 °C
(59.64% (Calcd 61.75%)).
The TG curve of the zinc(II) complex indicates three steps of decomposition from 130 to
691 °C. The first step at 130–232 °C involves the loss of ethyl alcohol with 10.55% (Calcd
10.52%) weight loss [31]. In the second step, 13.62% loss (Calcd 14.22%) indicates
removal of S-CH3 and CH3 groups at 232–308 °C. The third step is a slow process from
308-691 °C, which is due to the loss of the remainder of ligand, 60.77% (60.25%). The
final residue is ZnO with residual weight 19.98% (Calcd 21.50%).
3.4. X-ray study
Black crystals of iron(III) complex (1) were grown by slow evaporation of the solution of
the complex. Crystal parameters and refinement results of 1 are summarized in table 1.
Complex 1 crystallizes in the monoclinic space group P21/c with Z = 4. The structure of 1
has been solved by direct methods (SIR92) and refined to the residual index R1 = 0.046 for
1. The relevant bond lengths, bond and torsion angles of 1 are presented in tables 2–4.
ORTEP-III drawing with the atom numbering scheme and intermolecular hydrogen bonds
of 1 are illustrated in figures 3 and 4.
The angles of the coordination bonds indicate that the O1–N1–N3–O2 donor is at the
edges of a deformed square plane and iron is over this square base. Chloride is weakly
coordinated to iron, as evidenced by the 2.221(1) Å bond length. The Fe–Cl bond length of
1 agrees well with corresponding distance in similar complexes [20, 28]. The chloride is
closer to N1 compared to other edges of the pyramid base, and the square pyramid is
distorted in three axes.
Figure 4. Schematic of 1, 1a, and 1b as a key to table 5.

Complexes based on a thiosemicarbazone
Table 7. Hydrogen bond parameters in 1 (Å, °).
4079
D–H⋯A
d(D–H)
d(H⋯A)
d(D⋯A)
<(DHA)
C10–H8⋯Cl1
C13–H12⋯Cl1
0.95(6)
0.95(6)
2.88(7)i
2.86(7)ii
3.71(1)
3.74(1)
145.28(1)
159.32(1)
i+x, +y, +z;
iix, 1/2 − y, 1/2 + z.
The condensation of an aldehyde occurs by syn-conformation of the S-methyl-thiosemi-
carbazone backbone, and the obtained ONNO-ligand coordinates to the metal ion (figure 2).
The iron template shown in figure 2 has a square pyramidal geometry with O1, N1, N3,
and O2 of the tetradentate thiosemicarbazone chelating forming a square plane, and chloride
in the apical position. The ligand geometry of 1 agrees well with corresponding ligand
geometry in a similar complex [38].
The crystal structure of 1 shows intermolecular C–H⋯O interactions between hydrogens
of C10 and C13 of three [Fe(L)Cl] in figure 3. The intermolecular hydrogen bond parame-
ters of 1 are given in table 7.
In coordination of the ligand with iron, three metallo rings are formed: one five-mem-
bered FeN2C2 and two six-membered FeNC3O. The Fe1–O1 and Fe1–O2 bonds are rela-
tively short in comparison with Fe1–N1 and Fe1–N3; therefore, five- and six-membered
chelate rings are not regular. The principal distortions of the coordination sphere from ideal
square pyramidal geometry are the small N1–M–N3 (M = V, Mn, Fe) angle resulting from
geometric constraints of the ligand backbone and displacement of the metal from the basal
plane toward the axial ligand. The three chelate rings are not coplanar with the metal but
each of the rings is folded about a line joining its two donor atoms as depicted by the
dashed lines in figure 4. These fold angles in 1 together with the angles between the mean
planes of the phenyl rings and the displacement of the metal from the basal plane are pre-
sented in table 5 with corresponding data for several related complexes 1a [38] and 1b
[39]. In the five-coordinate complexes, there is a rough correlation between both the extent
of displacement of the metal from the N2O2 plane and the folding of the chelate rings and
the length of the bond to the axial ligand with the displacement in the order
X = O > Cl > Br.
4. Conclusion
We present new unsymmetrical N2O2 complexes of iron(III), nickel(II), and zinc(II) synthe-
sized by the template condensation of 2-hydroxy-acetophenone-S-methyl thiosemicarbazone
with 2-hydroxybenzaldehyde. The compounds have been characterized by analytic, spectral,
and TGA. Crystal and molecular structure analyses of [Fe(L)Cl] (1) have been carried out
by X-ray diffraction. The spectral and X-ray studies show that N1-[(2-hydroxyphenyl)ethyli-
dene]-N4-[(2-hydroxyphenyl)methylidene]-S-methyl-thiosemicarbazone is coordinated to
metal ions as a dianionic tetradentate N2O2 donor.
Square pyramidal coordination geometry is observed in [Fe(L)Cl] (1) and [Zn(L)
C2H5OH)] (2). The fifth coordination site is occupied by chloride in 1 and oxygen of ethyl
alcohol in 3. [NiL] (2) shows the expected square planar, a four-coordinate environment
around the nickel center. The thermal decomposition of the complexes by TGA analyses
shows that nickel(II) complex is more stable than 1 and 3. Decomposition temperatures are
185, 230, and 130 °C for 1, 2, and 3, respectively.

4080
Y. Kurt and N.G. Deniz
Supplementary material
Crystallographic data for the structure in this article have been deposited in the Cambridge
Crystallographic Data Center as supplementary publication number CCDC-1005617 for
[Fe(L)Cl] (1). Copies of the data can be obtained, free of charge, via www.ccdc.cam.ac.
uk/conts/retrieving.html or from the Cambridge Crystallographic Data Center, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK [Fax: +44 1223 336033. E-mail: deposit@
ccdc.cam.ac.uk].
Acknowledgment
We would like to thank Dr Gulin S. Pozan-Soylu for TGA (thermogravimetric analysis)
measurements.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the Research Fund of Istanbul University [grant number/project no. 24533].
Supplemental data
Supplemental data for this article can be accessed here [http://dx.doi.org/10.1080/00958972.2015.1086760].
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