Coordination compounds of 3D-metals salicylates with thiosemicarbazide

Article abstract of DOI:10.1134/S1070363212090046

Abstract-Complexes of copper(II), nickel(II), cobalt(III), zinc(II), and iron(III) salicylates with thiosemicarbazide were synthesized. The resulting compounds were characterized by the elemental analysis data, infrared spectroscopy, diffuse reflectance s

Full text of DOI:10.1134/S1070363212090046

ISSN 1070-3632, Russian Journal of General Chemistry, 2012, Vol. 82, No. 9, pp. 1481–1484. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © T.V. Koksharova, S.V. Kurando, I.V. Stoyanova, 2012, published in Zhurnal Obshchei Khimii, 2012, Vol. 82, No. 9, pp. 1422–1426.
Coordination Compounds of 3d-Metals Salicylates
with Thiosemicarbazide
T. V. Koksharovaa, S. V. Kurandoa, and I. V. Stoyanovab
a Mechnikov Odessa National University, ul. Dvoryanskaya 2, Odessa, 65026 Ukraine
e-mail: koksharova@farlep.net
b Bogatskii Physicochemical Institute, National Academy of Sciences of Ukraine, Odessa, Ukraine
Received July 5, 2011
Abstract—Complexes of copper(II), nickel(II), cobalt(III), zinc(II), and iron(III) salicylates with thiosemi-
carbazide were synthesized. The resulting compounds were characterized by the elemental analysis data,
infrared spectroscopy, diffuse reflectance spectroscopy, and thermogravimetry.
DOI: 10.1134/S1070363212090046
Salicylic acid H2Sal is a dibasic acid (pK1 2.7, pK2
7.5) [1] capable of forming the HSal– and Sal2– ions.
The salicylate ion can coordinate through the
carboxylate and phenolic oxygen atoms. This anion
can be: (a) monodentate, coordinating to the metal
through the carboxy group; (b) bidentate, coordinating
through the carboxy group; (c) bridging, bonding
different metal ions through the carboxy and phenolic
oxygen atoms simultaneously; (d) bidentate, chelating
through the carboxy and phenolic oxygen atoms. The
coordination mode of the salicylate anion depends
essentially on the presence of the additional ligands.
So, the coordination mode of the anion changes even
when varying the number of the bound water
molecules in salicylate Cu(HSal)2. In the tetrahydrate
the salicylate ion is monodentate, in the monohydrate
it is bidentate through one carboxy group. In the
dihydrate both the monodentate and bidentate-bridging
coordination of salicylate ion is observed [2]. It is
interesting to determine the character of changing
coordination of the salicylate ion when adding the
ligands, which are capable of forming stable
complexes with the metals.
The aim of this work was studying the reaction of
iron(III), cobalt(II), nickel(II), copper(II), and zinc(II)
salicylates with thiosemicarbazide.
The complexes were obtained by the action of an
aqueous solution of thiosemicarbazide on the dry 3d-
metal salicylate (metal:thiosemicarbazide = 1:4).
The elemental analysis data (Table 1) indicate that
the reaction of thiosemicarbazide with copper(II),
nickel(II), and zinc(II) salicylates occurs at the
metal:thiosemicarbazide ratio equal to 1:2, and for
cobalt( III) and iron(III) salicylates, 1:3.
Compared with the spectrum of free thiosemi-
carbazide, in the IR spectra of the complexes I–V the
frequency of a thioamide I band increases, which is
accompanied by a significant decrease in its intensity,
so that in the zinc complex it is manifested as a
shoulder on a more intensive band νs(COO–). An
attention is drawn to the difference in the values of the
shift of the thioamide I band in the case of the unequal
stoichiometry of the complexes. In the complexes
[M(HL)L2](HSal) the thioamide I band frequency
increases more than in [M(HL)2](HSal)2. On
complexing, the thioamide II band is also subjected to
a high-frequency shift. In the spectra of all the
complexes the intensity of thioamide III and the
frequency of thioamide IV bands decrease. According
to [12], this change corresponds to the bidentate
coordination of thiosemicarbazide, which involves the
sulfur and nitrogen atoms.
One of these ligands is thiosemicarbazide NH2NHC
(=S)NH2. Owing to the presence of the donor sulfur
and nitrogen atoms, which are in a favorable position
to form a five-membered ring, thiosemicarbazide
forms sufficiently stable coordination compounds with
3d-metal ions, including a variety of inorganic and
organic anions [3–11].
1481

1482
KOKSHAROVA et al.
Table 1. The elemental analysis data and colors of complexes I–V
Found, %
Calculated, %
Comp.
no.
Color
Formula
M
N
S
M
N
S
Brown
11.9
16.3
12.6
C16H20CuN6O6S2 [Cu(HL)2(HSal)2]
C16H20N6NiO6S2 [Ni(HL)2(HSal)2]
C10H18CoN9O3S3 [Co(HL)L2(HSal)]
C16H20N6O6S2Zn [Zn(HL)2(HSal)2]
C10H18FeN9O3S3 [Fe(HL)L2(HSal)]
12.3
16.2
12.3
I
Green
Brown
White
Brown
11.2
12.2
12.7
12.1
16.1
27.2
15.7
27.1
12.6
20.3
11.9
20.3
11.5
12.6
12.5
12.1
16.3
27.0
16.1
27.2
12.4
20.6
12.3
20.7
II
III
IV
V
Table 2. The IR spectroscopy data (cm–1) of complexes I–V, salicylates, and ligand HL
ν(C=C)
(aromatic ring)
δ(CH)
(out-of-plane)
Compound
HL
ν(OH)(H2O) ν(NH) νas(COO–) νs(COO–)
ν(C–O)
1530
1545
1315 1000 800
3370,
3260,
3170
Cu(HSal)2·4H2O
3444, 3341
3392
1606
1601
1473
1486
1456
1458
1249
1259
754, 745
770а
1382, 944 770а
1354
3409,
3305,
3262,
3177
I
Ni(HSal)2·4H2O
1572
1604
1400
1485
1456
1461
1237
1253
777
765а
1546
1585
1382, 948 765а
1354
3307,
3113
–
II
Co(HSal)2·4H2O
3392
–
1570
1620
1401
1485
1454
1456
1235
1248
776
759а
1339
–
759а
3295,
3140
III
Zn(HSal)2·2H2O
3389
–
–
1571
1604
1404
1492
1452
–
1232
1245
778
1550
(shoulder)
1355 1000 745а
1391а 922 759а
3420,
3321,
3181
–
745а
IV
Fe(HSal)3·4H2O
3393
–
1602
1590
1485
1484
1456
1460
1241
1243
758
759а
1590
3175
V
a Thiosemicarbazide and salicylate anion contribute into the absorption bands.
The IR spectra of the complexes [Co(HL)L2](HSal)
and [Fe(HL)L2](HSal) contain very intensive
absorption bands at 2061 and 2046 cm–1, respectively.
The reactions of some copper(II) aliphatic carboxyates
Cu(CnH2n+1COO)2 with thiosemicarbazide have been
previously studied. When n ≥ 4, the reaction product
lacks the carboxyate anion, and thiosemicarbazide acts
as a deprotonated form to give CuL2 [4]. The spectrum
of this compound also contains the absorption bands at
~2100 cm–1. The range of 2200–1900 cm–1 is charac-
teristic of the stretching vibrations of the cumulated
double bonds [13], in particular, of the thiocyanate
ions. In this case the NCS-group, similar to the SCN
moiety, can appear only when the metal is bound to the
nitrogen atom adjacent to the carbon atom.
Consequently, the deprotonated thiosemicarbazide
forms a four-membered ring, where the metal is co-
valently bound to the nitrogen and coordinated with
the sulfur. Thus, for the cobalt(III) and Fe(III) com-
plexes we should assume the presence of two forms of
thiosemicarbazide in the complex molecule: molecular
and deprotonated.
The IR spectrum of free salicylic acid contains the
absorption bands at 1657 (C=O), 1445 (C=C, aromatic
ring), 1296 [δ(OH)], 1249 (C–O), and 760 cm–1
[δ(CH), out-of-plane bending] [2, 13, 14].
In the IR spectra of salicylates obtained the
absorption band ν(C=O) is absent due to equivalence
of the carboxy oxygen atoms at eliminating the proton
from the carboxy group. This is accompanied by the
disappearance of the absorption band of the carbonyl
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COORDINATION COMPOUNDS OF 3d-METALS SALICYLATES
1483
Table 3. The diffusion reflectance spectroscopy data of
complexes I–III
moiety and the appearance of two new bands in the
ranges of 1550–1610 and 1300–1400 cm–1 [νas,s(COO–)]
[15]. The difference between the νas and νs values is
often used to determine the bond nature of the carboxy
moiety with the complexing agent. We believe that the
difference ΔΔν(COO–), i.e., the difference between the
values Δν(COO–) of the reaction product and the initial
carboxyate, is more acceptable. For all the compounds
obtained the value ΔΔν(COO–) is negative (from –18
to –55 cm–1), probably due to some bond elongation in
the salicylate anion owing to its displacement into the
outer sphere of the complexes.
The absorption band at 1200 cm–1 corresponds to
the stretching vibrations ν(C–O) of the aryl-bonded
OH-group. In the spectra of thiosemicarbazide
complexes the frequencies of these bands increase. In
the spectra of the starting salicylates the absorption
bands at 1460 cm–1 belonging to the “pulsation”
vibrations ν(C=C) of the benzene ring are very inten-
sive and narrow. In the spectra of thiosemicarbazide
complexes these bands are low-intensive and broad. In
the spectra of the coordination compounds the
absorption band of the out-of-plane bending vibrations
δ(CH) are overlapped with the thioamide IV band
which results in a slight increase in their intensity
compared with the initial salicylates.
Compound
λ, nm
460
Assignment
I
385
410
560
460
ν3
II
ν2
ν1
1A1g → 1T1
III
effect of the nickel(II) compounds is significantly
higher than the corresponding temperature for the
other complexes. This allows us an assumption that the
nickel(II) complex is more thermally stable than the
other studied coordination compounds. It can melt
without decomposition, whereas in other cases the
heating to a temperature of the first effect is
accompanied by the destruction of the complexes.
These experiments make it possible to assign the
following structure to the synthesized coordination
compounds.
H2
N
H2N
S
NH
(C6H4OHCOO)2
M
HN
S
N
NH2
H2
The closeness of the frequencies of the absorption
bands of the salicylate anion in the IR spectra of all the
synthesized coordination compounds is obviously due
to the fact that in [M(HL)2](HSal)2 and [M(HL)L2]·
(HSal) the salicylate anion is in the same mono-
deprotonated form. Hence it must be assumed that in
the case of the three-charged complexing agent two of
the three coordinated thiosemicarbazide molecules are
deprotonated.
M = Cu (I), Ni (II), Zn (IV).
H
N
H2N
M
NH2
NH2
S
S
H2N
(C6H4OHCOO)
N
N
S
NH2
NH2
The diffuse reflectance spectra (Table 3) confirm
the octahedral structure of the cobalt(III) complex and
the planar structure of the nickel(II) and copper(II)
complexes [16]. For the iron(III) complex the bands in
the diffuse reflectance spectra do not have a clearly
defined maxima.
M = Co (III), Fe (V).
EXPERIMENTAL
The IR spectra were recorded on a Perkin-Elmer
Spectrum BX II FT-IR System instrument from KBr
pellets. The diffuse reflectance spectra were registered
on a Lambda-9 spectrophotometer (Perkin-Elmer)
relative to MgO (βMgO 100%). The TG analysis was
performed on a Paulik–Paulik–Erdey derivatograph
system in air with the heating rate of 10°C min–1.
The assumptions made for compounds [Cu(HL)2]·
(HSal)2 and [Ni(HL)2](HSal)2 were confirmed by XRD
[17].
In the thermograms of all the complexes (Table 4)
the first effects are endothermic. In addition, only in
the nickel(II) complex this effect is not accompanied
by a mass loss, which obviously corresponds to the
melting. Furthermore, the temperature of the first
Iron(II), cobalt(II), nickel(II), copper(II), and
zinc(II) chlorides, salicylic acid, and thiosemicarbazide
were of analytical grade.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 9 2012

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KOKSHAROVA et al.
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Exo-effects
Total
mass
loss, %
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Δm, %
t, oC
Δm,
%
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78–132(110)
4.5
165–245(193) 39.2
67.5
I
245–305(290)
305–380(340)
6.2
2.2
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80–142(118)
–
195–240(225) 46.9
142–178(170) 20.4
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48.3
53.4
II
7.3
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5.7
no. 2, p. 203.
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55–150(112)
2.7
5.1
170–245(205) 25.9
72.9
41.1
IV
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315–350(340)
3.2
7.0
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V
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6.6
3.7
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The 3d-metal salicylates were obtained via the
exchange reactions between sodium salicylate,
obtained by the salicylic acid neutralization, and a 3d-
metal chloride in water.
14. Lajunen, L.H.J. and Kokkonen, P., Thermochim. Acta,
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The metal content in the isolated compounds was
determined by the chelatometry [18], the nitrogen
content, according to the Dumas method [19], the
sulfur content, by the Schoeniger method [19].
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XXV Mezhdunarodnaya Chugaevskaya konferentsiya po
Synthesis of complexes (I–V). To a solution of
0.91 g (0.01 mol) of thiosemicarbazide in 100 ml of
water was added by portions 0.0025 mol of dry
salicylate of the corresponding metal while stirring.
The mixture was stirred until a homogeneous
precipitate formed, which was filtered off on a glass
frit filter, washed with water, and dried in a desiccator
over calcium chloride to the constant weight.
koordinatsionnoi
khimii
i
II Molodyozhnaya
konferentsiya-shkola “Fiziko-khimicheskie metody v
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tional Chugaev Conference on Coordination Chemistry
and II Young Conf. “Physical-Chemical Methods in
Chemistry of Coordination Compounds”), Suzdal, 2011,
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