Synthesis and characterization of zinc(II) complexes with 3,4-dimethoxybenzaldehyde thiosemicarbazone: The crystal structure of [Zn(34-MBTSC) 2Cl 2]

Article abstract of DOI:10.1080/10426507.2012.738736

The synthesis and characterization of three zinc(II) complexes [Zn(34-MBTSC)₂Cl₂] (1), [Zn(34-MBTSC)₂Br ₂] (2), and [Zn(34-MBTSC)₂I₂] (3) of 3,4-dimethoxybenzaldehyde thiosemicarbazone (34-

Full text of DOI:10.1080/10426507.2012.738736

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Synthesis and Characterization
of Zinc(II) Complexes with
3,4-Dimethoxybenzaldehyde
Thiosemicarbazone: The Crystal
Structure of [Zn(34-MBTSC)2Cl2]
Aliakbar Dehno Khalaji a , Gholamhossein Grivani b , Morteza Rezaei
b , Karla Fejfarova c & Michal Dusek c
a Department of Chemistry, Faculty of Science , Golestan
University , Gorgan , Iran
b School of Chemistry , Damghan University , Damghan , Iran
c Institute of Physics ASCR, v.v.i. , Prague , Czech Republic
Accepted author version posted online: 25 Oct 2012.
To cite this article: Aliakbar Dehno Khalaji , Gholamhossein Grivani , Morteza Rezaei ,
Karla Fejfarova & Michal Dusek (2013) Synthesis and Characterization of Zinc(II) Complexes
with 3,4-Dimethoxybenzaldehyde Thiosemicarbazone: The Crystal Structure of [Zn(34-
MBTSC)2Cl2], Phosphorus, Sulfur, and Silicon and the Related Elements, 188:8, 1119-1126, DOI:
10.1080/10426507.2012.738736
To link to this article: http://dx.doi.org/10.1080/10426507.2012.738736
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Phosphorus, Sulfur, and Silicon, 188:1119–1126, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.738736
SYNTHESIS AND CHARACTERIZATION OF ZINC(II)
COMPLEXES WITH 3,4-DIMETHOXYBENZALDEHYDE
THIOSEMICARBAZONE: THE CRYSTAL STRUCTURE
OF [ZN(34-MBTSC)2CL2]
Aliakbar Dehno Khalaji,1 Gholamhossein Grivani,2
Morteza Rezaei,2 Karla Fejfarova,3 and Michal Dusek3
1Department of Chemistry, Faculty of Science, Golestan University, Gorgan, Iran
2School of Chemistry, Damghan University, Damghan, Iran
3Institute of Physics ASCR, v.v.i., Prague, Czech Republic
GRAPHICAL ABSTRACT
H3C
O
X
H
N
O
S
CH3
N
NH2
Zn
NH2
N
X
H3C
N
S
O
H
O
CH3
Abstract The synthesis and characterization of three zinc(II) complexes [Zn(34-MBTSC)2Cl2]
(1), [Zn(34-MBTSC)2Br2] (2), and [Zn(34-MBTSC)2I2] (3) of 3,4-dimethoxybenzaldehyde
thiosemicarbazone (34-MBTSC) are reported. Elemental analysis (CHN) and spectral (FT-
IR and 1H-NMR) measurements have been used to characterize the complexes. In addition,
the structure of the complex 1 has been determined by X-ray diffraction methods. In these
complexes, the zinc(II) ion is bonded to two thioketonic sulfur donors in η1-S bonding mode
and to two halide ions in tetrahedral geometry.
Supplementary materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental
files: Additional figures.
Keywords Zinc(II) complexes; thiosemicarbazone; X-ray diffraction; tetrahedral
INTRODUCTION
Thiosemicarbazone N,S donor ligands and their transition metal complexes have been
studied because of their fungicidal, bactericidal, antiviral and antitumoral activities,1–6
Received 10 July 2012; accepted 8 October 2012.
We acknowledge Golestan University (GU) and Damghan University (DU) for partial support of this work,
the institutional research plan No. AVOZ10100521 of the Institute of Physics and the project Pramium Academiae
of the Academy of Sciences of the Czech Republic.
Address correspondence to Aliakbar Dehno Khalaji, Department of Chemistry, Faculty of Science, Golestan
University, Gorgan, Iran. Tel/Fax: +98-171-2245882. E-mail: ad.khalaji@gu.ac.ir
1119

1120
A. D. KHALAJI ET AL.
H3C
O
X
Zn
H
N
O
S
CH3
N
NH2
NH2
N
X
H3C
N
H
S
O
O
CH3
Scheme 1 Chemical structure of zinc(II) complexes [Zn(34-MBTSC)2×2] (X = Cl (1), X = Br (2) and X = I
(3)).
and interesting chemical and structural properties.7–12 The biological activity of these
compounds is strongly dependent on the nature of the heteroaromatic ring and the position
of substituent to the ring, as well as the form of the thiosemicarbazone moiety.13 They have
been used for metal analyses;14 and for device applications related to optical computing,
storage, and information processing.15 Thiosemicarbazones have a propensity to react with
a wide range of transition metal ions.7–12,16–21 They can bind to a metal ion via a variety of
coordination modes in their neutral and anionic form.7–12,16–21 They usually act as chelating
N,S ligands with transition metal ions such as Zn(II), Hg(II), Ni(II), Co(II), Cu(II), and
Cd(II), bonding through the sulfur and hydrazine nitrogen atoms16–19 and as η1-S bonding
mode with Cu(I) and Ag(I) ions.7,8,20,21 Only a few reports exist on η1–S bonding mode of
thiosemicarbazone ligands with Zn(II) ion.22,23
We describe here three zinc(II) complexes obtained from 3,4-dimethoxybenzaldehyde
thiosemicarbazone (34-MBTSC) as a ligand (Scheme 1).
RESULTS AND DISCUSSION
The ligand 34-MBTSC was prepared by condensation of thiosemicarbazide with
3,4-dimethoxybenzaldehyde following the literature method.24 The reaction of ZnX2 with
34-MBTSC in ethanol-acetonitrile solvent mixture at r.t. results in monomeric zinc(II)
complexes as shown in Scheme 1. The solubility of thiosemicarbazone ligand 34-MBTSC
and its zinc(II) complexes was determined by adding the solvent to a known amount of
compound until complete dissolution. It was found that all compounds are moderately
soluble in common organic solvents, insoluble in water, and completely soluble in DMF
and DMSO. In order to confirm the chemical composition of the synthesized complexes,
1
CHN, XRD, FT-IR, and H-NMR analyses were carried out with results are presented in
the experimental section.
FT-IR Spectra
The main infrared vibration bands are reported in the experimental section. The
presence of the ν(N–H) band at 3181 cm−1 shows that neutral thio-ligand is coordinated
to zinc(II) metal center through thione sulfur.19,23,25 In addition, the spectrum of the ligand
shows a strong band at 1643 cm−1 due to the –C N– stretching vibration.19,23
In complexes, the ν(C N) vibration band shifted to lower wavenumbers, whereas
ν(N–H) vibration bands shifted to higher wavenumbers. The two bands corresponding to
ν(C S) in complexes are significantly modified when compared to the free ligand. In

SYNTHESIS AND CHARACTERIZATION OF ZN(II) COMPLEXES
1121
addition, the spectrum of the zinc(II) complexes 1–3 shows the vibration band ν(Zn–S)
at 412 cm−1 (1), 411 cm−1 (2), and 409 cm−1 (3), which corresponds to the coordination
bonds.19,23,29
1H-NMR Spectra
1
The H-NMR spectral data of the ligand 34-MBTSC and its zinc(II) complexes
were recorded in DMSO-d6 with tetramethylsilane as an internal standard and are reported
in the experimental section. The 1H-NMR spectra of zinc(II) complexes suggest that they
have similar structure (Figure 1), they also agree with the thione tautomer as indicated on
the basis of FT-IR data. However, they are slightly modified, with some multiplicity of the
signals and some small changes in the chemical shifts with respect to the free ligand.23
Spectra for 1, 2, and 3 can be found in the Supplemental Materials (Figure S5)
Crystal and Molecular Structure of 1
An ORTEP view of [Zn(34-MBTSC)2Cl2] (1) with the atoms numbering scheme
is given in Figure 2. Table 1 lists the selected bond lengths and angles. In the complex
[Zn(34-MBTSC)2Cl2] (1), the thiosemicarbazone ligand 34-MBTSC is neutral and S-
monodentate. Zinc(II) is coordinated by two chlorine ions and the thione sulfur atoms of
two independent ligands. The two ligands are in Z position relative to C8–N2 and C8i–N2i
bonds, respectively. The tetrahedral geometry around the zinc(II) ion in 1 is distorted
because of the different bond distances and angles. The greatest angular distortion from an
ideal tetrahedral geometry (109.5 ◦) occurs in the angles Cl1–Zn1–Cl1i [120.59(2) ◦] and
Figure 1 1H-NMR spectrum of zinc(II) complex [Zn(34-MBTSC)2×2] (1).

1122
A. D. KHALAJI ET AL.
Figure 2 An ORTEP view of 1, showing 50% probability displacement ellipsoids and the atom-numbering.
Dashed lines indicate intramolecular N–H···S and N–H···Cl hydrogen bonds. Symmetry codes: (i) −x, y, −z+1/2.
Cl1–Zn1–S1 [98.404(17) ◦]. The Zn–S and Zn–Cl distances (Table 1) are similar to those
found in other zinc(II) complexes with thiol sulfur atoms.22,23 Additional representations
of the structure are shown in the Supplemental Materials (Figures S 2 and S 3).
The length of the N2–C8 bond is 1.329(2) Å, the C7–N1 bond is 1.280(3) Å, and the
N1–N2 bond is 1.384(2) Å. These distances are typical of a C–N single bond, C N double
bond, and N–N single bond, respectively. In addition, the bond length of the C8–S1 bond
is 1.7209(19) Å, which is in between a single and a double bond as it has been already
observed in the cases of the zinc(II) complexes with similar ligands.22,23 The molecules
of the two ligands are planar and the angle between the planes of the two phenyl rings is
87.969(50) ◦.
Complex 1 shows an intramolecular N–H···S and N–H···Cl hydrogen bonding via
hydrogen atoms of NH2 with chlorine and sulfur atoms (Figure 2, Table 2), while in the
Table 1 Selected bond distances (Å) and angles (◦) of 1
Zn1–Cl1
2.2594(5)
Zn1–S1
N2–C8
2.3461(5)
N1–N2
N1–C7
1.384(2)
1.280(3)
1.329(2)
1.317(3)
N3–C8
S1–C8
1.7209(19)
120.59(2)
98.404(17)
114.592(17)
114.92(16)
119.11(16)
121.03(18)
Cl1–Zn1–Cl1i
Cl1–Zn1–S1
Cl1–Zn1–S1i
N2–N1–C7
N1–N2–C8
N1–C7–C1
Cl1i–Zn1–S1
Cl1i–Zn1–S1i
S1–Zn1–S1i
S1–C8–N2
S1–C8–N3
N2–C8–N3
114.592(17)
98.404(17)
110.87(2)
116.14(14)
124.27(14)
119.59(17)
Symmetry codes: (i) −x, y, −z+1/2.

SYNTHESIS AND CHARACTERIZATION OF ZN(II) COMPLEXES
1123
Table 2 Geometric parameters of hydrogen bond for 1
Distance, Å
D–H···A
D–H
H···A
D···A
D–H···A, deg
N3–H3b···S1
N3–H3b···Cl1
C6–H6···S1
N2–H2n···O2
C7–H7···O2
0.817
0.817
0.960
0.866
0.960
3.168
2.964
2.943
2.085
2.724
3.717
3.687
3.840
2.941
3.496
126.947
148.834
156.038
169.694
137.873
crystal packing of 1, the monomer units are linked to each other via several classical and
non-classical intermolecular hydrogen bonds (N–H···O, C–H···O and C–H···S) (Table 2).
EXPERIMENTAL
All organic solvents used are commercially available and used as received without
further purifications. The 3,4-dimethoxybenzaldehyde, thiosemicarbazide, ZnI2, ZnBr2,
and ZnCl2 were purchased from Merck Chemical Company. Fourier Transform Infrared
spectra were recorded as a KBr disk on a FT-IR Perkin–Elmer spectrophotometer. Elemental
analyses were carried out using a Heraeus CHN-O-Rapid analyzer. 1H NMR spectra were
measured on a BRUKER DRX-500 AVANCE spectrometer at 500 MHz for the Schiff-
base ligands and its complexes. All chemical shifts are reported in δ units downfield from
TMS. X-ray powder diffraction pattern of the complex was recorded on a Bruker AXS
Table 3 Crystallographic data and structure refinement for 1
Empirical formula
C20H2662Cl2O4S2Zn
Formula weight
614.9
Temperature
150
Crystal system, space group
Unit cell dimensions
Monoclinic, C2/c
a = 19.0691(3) Å
a = 9.9920(2) Å
a = 14.2504(2) Å
β = 91.7482(13)º
2717.83(8)
Volume, Å3
Calculated density, Z
Absorption coefficient
F(000)
4, 1.5022 Mg/m3
4.85 mm−1
1264
Theta range for data collection
Limiting indices
4.65–63.67 º
–21 ≤ h ≤ 21
–11 ≤ k ≤ 11
–16 ≤ l ≤ 16
33279 / 2144 [Rint = 1.84]
Reflections collected/unique
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R-indices [I > 3σ(I)]
R-indices (all data)
2236/3/168
1.84
R1 = 0.0293, wR2 = 0.1032
R1 = 0.0304, wR2 = 0.1046
0.71 and –0.33 eÅ−3
Largest diff. peak and hole

1124
A. D. KHALAJI ET AL.
diffractometer D8 ADVANCE with Cu-Kα radiation with nickel beta filter in the range 2θ =
10–80 ◦.
Preparation of 34-MBTSC
The ligand 34-MBTSC (Figure S 1, Supplemental Materials) was obtained from 3,4-
dimethoxybenzaldehyde and thiosemicarbazide (1:1 molar ratio) in ethanol (10 mL) follow-
ing the literature method.24 Yield: 83%. Colorless crystals. Anal. Calc. for C10H13N3O2S:
C, 50.20; H, 5.48; N, 17.56%. Found: C, 50.11; H, 5.35; N, 17.56%. IR (KBr pellet, cm−1):
3352, 3262, and 3181 (N–H), 1643, 1618, 1602, 1576 (C N, C C), 1161, 753 (C S), 952
(N–N). 1H-NMR (DMSO-d6, δ(ppm)): 3.76 (s, 3H7), 3.78 (s, 3H8), 6.93 (d, J = 8.55 Hz,
H6), 7.11 (dd, H5), 7.50 (d, J = 1.35 Hz, H9), 7.94 (s, H1), 8.0 (s, H2), 8.14 (s, H4), 11.30
(s, H3).
Preparation of [Zn(34-MBTSC)2Cl2] (1)
To a stirring ethanolic (5 mL) solution of the 34-MBTSC ligand (0.408 g, 0.2 mmol)
was added ZnCl2 (0.028 g, 0.2 mmol) in acetonitrile (10 mL) and the mixture was stirred
for 10 min in air at r.t. and was then left at r.t. for several days without disturbance yielding
suitable crystals of 1 that subsequently were filtered off and washed with Et2O. Yield: 72%.
Colorless crystals. Anal. Calc. for C20H26N6Cl2O4S2Zn: C, 39.07; H, 4.26; N, 13.67%.
Found: C, 38.98; H, 4.11; N, 13.64%. IR (KBr pellet, cm−1): 3438, 3317, and 3217 (N–H),
1611, 1597, 1579, 1561 (C N, C C), 1165, 751 (C S), 956 (N–N), 412 (Zn–S). 1H-NMR
(DMSO-d6, δ(ppm)): 3.76 (s, 3H7), 3.79 (s, 3H8), 6.93 (d, J = 8.42 Hz, H6), 7.11 (dd, H5),
7.50 (d, J = 1.29 Hz, H9), 7.96 (s, H1), 8.02 (s, H2), 8.15 (s, H4), 11.32 (s, H3).
Preparation of [Zn(34-MBTSC)2Br2] (2)
This complex was prepared in a similar way as 1 using ZnBr2. Yield: 71%. Colorless
crystals. Anal. Calc. for C20H26N6Br2O4S2Zn: C, 34.13; H, 3.72; N, 11.94%. Found: C,
33.96; H, 3.59; N, 12.03%. IR (KBr pellet, cm−1): 3439, 3316, and 3218 (N–H), 1610,
1
1595, 1580, 1557 (C N, C C), 1164, 751 (C S), 955 (N–N), 411 (Zn–S). H-NMR
(DMSO-d6, δ(ppm)): 3.77 (s, 3H7), 3.80 (s, 3H8), 6.94 (d, J = 8.48 Hz, H6), 7.12 (dd, H5),
7.55 (d, J = 1.38 Hz, H9), 7.95 (s, H1), 8.01 (s, H2), 8.15 (s, H4), 11.31 (s, H3).
Preparation of [Zn(34-MBTSC)2I2] (3)
This complex was prepared in a similar way as 1 using ZnI2. Yield: 68%. Colorless
crystals. Anal. Calc. for C20H26N6I2O4S2Zn: C, 30.11; H, 3.28; N, 10.53%. Found: C,
29.99; H, 3.20; N, 10.66%. IR (KBr pellet, cm−1): 3431, 3311, and 3224 (N–H), 1605,
1
1592, 1577, 1547 (C N, C C), 1164, 750 (C S), 955 (N–N), 409 (Zn–S). H-NMR
(DMSO-d6, δ(ppm)): 3.77 (s, 3H7), 3.80 (s, 3H8), 6.94 (d, J = 8.51 Hz, H6), 7.12 (dd, H5),
7.50 (d, J = 1.31 Hz, H9), 7.95 (s, H1), 8.00 (s, H2), 8.14 (s, H4), 11.30 (s, H3).
X-Ray Structure Determination
Single crystal of the dimensions 0.31 mm × 0.22 mm × 0.17 mm of 1 was chosen for
X-ray diffraction study. Crystallographic measurements were done at 150 K with four circle

SYNTHESIS AND CHARACTERIZATION OF ZN(II) COMPLEXES
1125
CCD diffractometer Gemini (Oxford Diffraction) with mirrors-collimated Cu Kα radiation
(λ = 1.54184 Å), using the area detector atlas. The crystal structures were solved by direct
methods with program SIR200226 and refined with the Jana2006 program package27 by
full-matrix least-squares technique on F2. The molecular structure plots were prepared by
ORTEP III.28 Hydrogen atoms were mostly discernible in difference Fourier maps and could
be refined to reasonable geometry. According to common practice they were nevertheless
kept in ideal positions during the refinement except the ones bounded to nitrogen. The
isotropic atomic displacement parameters of all hydrogen atoms were evaluated as 1.2Ueq
of the parent atom. Crystallographic data and details of the data collection and structure
solution and refinements are listed in Table 3.
SUPPLEMENTARY DATA
Crystallographic data (excluding structure factors) for the structures reported in this
paper have been deposited with the Cambridge Crystallographic Center, CCDC No. 821654
(1). Copies of the data can be obtained free of charge on application to The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, fax: +44 1223 336 033, E-mail:
deposit@ccdc.cam.ac.uk or website: http:www.ccdc.cam.ac.uk.
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