Synthesis and characterization of divalent transition metal complexes containing thiosemicarbazone ligands

Article abstract of DOI:10.13005/ojc/290453

Complexes of divalent transition metals Co(II), Ni (II) and Cu(II) with ligand 2 - hydroxy - 4 - nitro acetophenone thiosemicarbazone have been synthesized. The complexes were characterized on the basis of elemental analysis, magnetic studies, electrical

Full text of DOI:10.13005/ojc/290453

ISSN: 0970-020 X
CODEN: OJCHEG
2013, Vol. 29, No. (4):
Pg. 1651-1656
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Synthesis and Characterization of Divalent Transition Metal
Complexes Containing Thiosemicarbazone Ligands
PREM MOHAN MISHRA1, MANOJ KUMAR JHA2,
RAM SUbHAg CHAUDHARY3 and CHANDAN KUMAR4
1Department of Chemistry, (MLSM College), L. N. Mithila University, Darbhanga - 846 004, India.
2At-Dighiwest, PO-lalbag, Darbhanga, Bihar, India.
3Department of Chemistry, M M T M College, Darbhanga, India.
4At+ PO- Kharajpur, Darbhanga, Bihar, India.
http://dx.doi.org/10.13005/ojc/290453
(Received: October 31, 2013; Accepted: December 12, 2013)
AbSTRACT
Complexes of divalent transition metals Co(II), Ni (II) and Cu(II) with ligand 2 – hydroxy – 4
– nitro acetophenone thiosemicarbazone have been synthesized.The complexes were characterized
on the basis of elemental analysis, magnetic studies, electrical conductance and IR and electronic
spectra.The complexes of Co(II) and Ni(II) were found to be octahedral where as Cu(II) complexes
has square planer geometry.
Key words: Thiosemicarbazone, Schiff’s bases, Transition metals, complex compounds.
INTRODUCTION
EXPERIMENTAL
Preparation of Ligand
4.8g of 2-hydroxy – 4 nitro – acetophenone
was dissolved in methanol and treated with a
solution containing 3.8 g BDH Anal R grade thio
semicarbazide hydrochloride in water.
Thiosemicarbazones posses considerable
biological properties and have medicinal applications
such as antiT.B. and leprosy1-2, antiviral properties3,
antitumour4, anticancer5,6. Literature survey reveals
that the presence of a metal ion increases the activity
of or mitigate the side effects of the parent organic
compounds7-10
.
The mixture was stirred well and refluxed
for half an hour on a water bath and cooled. Pale
yellow crystals was separated. The crude yellow
product was recrystallised from alcohol as colourless
needles. Melting point of the compound was
determined by Kjeldahl’s method and was found
to be 491 K. The pure and dried compound was
chemically analysed. It is slightly soluble in alcohol
but highly soluble in DMF but insoluble in water.
In continuation of our previous work in this
communication we are going to report synthesis and
characterization of complexes of Co(II), Ni(II) and
Cu(II) with ligands containing thio semicarbozone
of substituted aromatic ketones.

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MISHRA et al, Orient. J. Chem., Vol. 29(4), 1651-1656 (2013)
gives some important information regarding the
Preparation of complexes
Calculated quantity of metal salts (0.482 nature of the lignad as well as the co-ordination sites
g cobalt chloride CoCl2.6H2O) was dissolved in through which metal ion has co-ordinated with the
methanol while the ligand (HNAPTS) was dissolved ligand.
in DMF. Both the solution were mixed together and
1.0 g sodium acetate was added to it. The solution
The band at 3195 cm-1 in the ligand
was refluxed for about three hours and left overnight. assignable to phenolic O – H (hydrogen bonded)
The grey precipitate was obtained. It is filtered and stretching frequency11 disappears in the Ni(II), Co
washed with methanol and ice cold water.The pure (II) complexes showing deprotonation of phenolic
complexes was dried in air.
proton. The ligand also shows strong band at
1260 cm-1 which may be attributed to the phenolic
0.520g of nickel (II) chloride was dissolved C – O vibration. A shift of this band to higher
in water while 0.820 g ligand was dissolved in DMF. frequency (~ 1300 cm-1) in the complexes indicate
Both the solution were mixed. 1.0 g sodium acetate chelation of the ligand to metal ion through phenolic
was added and refluxed for about three hours and oxygen.
left to stand for an hour.The red coloured precipitate
was obtained. It was filtered and washed with water
and ethanol and dried in air.
The sharp band at 1580 cm-1 in the free
ligand due to C=N of Schif’s base residue shifts to
the lower frequency at (~1565 cm-1) in the complexes
An ammoniacal solution of 0.256 g copper showing co-ordination through the nitrogen atom.
(II) chloride was treated with a solution of 0.348 g The lowering may be very small in some cases.
ligand (HNAPTS) dissolved in DMF.The red coloured The ligand band at 1165 cm-1 may be assigned to
precipitate separated was digested on the water C=S group and shows downward shifting in metal
bath for two hours and then left to stand for an hour. complexes, indicating participation of this group in
It was filtered washed with water and dried in air. All co-ordination.
the three complexes were analysed chemically.
The absorption band at 3380 cm-1 due to
RESULTS AND DISCUSSION
N-H group in the free ligand remains unaltered in the
complexes, indicating non-participation of this group
Probable structure of ligand 2-hydroxy-4-nitro in co-ordination.
acetophenone thiosemicarbazone (HNAPTS)
The interpretation of I. R. spectra is quite
A band present at 1385 cm-1 in the I. R.
complicated due to the presence of various similar spectra of the ligand is assigned12 to C-N group due
groups and hence presence of many absorption to nitro group. This band remains unchanged in all
bands. However, comparison of the spectral bands the complexes, suggesting non – participation of nitro
of the ligand (HNAPTS), with those of its complexes group in co-ordination.
Table 1: Elemental analysis data of ligand and complexes
Compound
% Observed (calculated)
C
H
N
O
M
HNAPTS
[Co(HNAPTS)2]
37.98
(38.23)
38.43
(38.25)
31.80
(32.36)
3.76
(3.16)
3.28
(3.18)
3.95
(3.60)
20.05
(19.83)
19.47
(19.84)
20.18
(20.97)
16.73
(17.0)
17.83
(16.97)
15.96
(14.40)
11.16
(11.38)
17.83
(16.97)
15.96
(14.40)
10.32
(10.40)
10.16
(10.38)
18.96
(19.40)
[Ni(HNAPTS)2]
[Cu(HNAPTS)NH3]

MISHRA et al, Orient. J. Chem., Vol. 29(4), 1651-1656 (2013)
1653
Thus, we come to a conclusion that the
good agreement with our previous observation17-24
.
ligand, 2 – Hydroxy – 4 – nitro acetophenone
thiosemicarbazone (HNAPTS) behaves as a
tridentate ligand for the metal ions, co-ordinating
through (i) phenolic oxygen (C – O), (ii) nitrogen
atom of (C = N), of azomethine group and (iii) ketonic
sulphur of C = S, as enolic group. Similar kind of
situation has been reported by S. K.Thampy.13 This
ligand is monoprotic in all the cases except Ni(II) and
Cu (II) at higher pH (pH = 9). It has been observed
that in these cases a band present at 1165 cm-1 in the
free ligand disappears, perhaps due to deprotonation
of the C = S (enolic ) proton.
The ligand may be assumed to be tautomer of the
following two probable structures.
Structure of complexes
Themolarconductancevaluesofcomplexes
18.78 for Co(II), 16.80 for Ni(II) and 18.6 for Cu(II)
suggest non–electrolytic nature of all the complexes
[Co(HNAPTS)2], [Ni(HNAPTS)2] and [Cu(HNAPTS)
NH3] .
Electronic Spectra
These Ni (II) complexes show four bands
in their reflectance spectra favouring an octahedral
stereochemistry25.Out of these four bands, three can
be assigned to spin allowed d – d transition, eg. 3A2g
Many workers14-20 havepreparedcomplexes
with Schiff’s base derived from substituted
salicylaldehyde and reported non-participation
of the substituents in the co-ordination. However,
stability of the complex is certainly influenced by the
presence of the substituents. These results are in
3
3
3
(F) → T2g (F), 3A2g(F) → T1g(F) and 3A2g(F) → T1g
(P). The fourth band near 10750 cm-1 is probably
spin forbidden25 and may be assigned to 2B1g → Eg
2
transition.
Table 2: Melting point, Decomposition temperature, magnetic
moment & electrical conductivity data of complexes
Compounds
M. P(K)
D.T. (K)
µeff (bM)
Ohm cm² mol-1
HNAPTS
491
-
-
-
[Co(HNAPTS)2]
[Ni(HNAPTS)2]
[Cu(HNAPTS) NH3]
-
-
473
533
513
4.15
3.05
1.83
18.78
16.80
18.6
503
* M.P - Melting point;D.T. - Decomposition temperature ,
µeff=Magnetic moment
= molar conductivity
Table 3: Electronic spectral data
of complexes and their assignment
Compound Assignment
(in cm-1)
9390
4
[Co(HNAPTS)2]
4T1g→ T2g (F)
4
19900
22085
11560
17380
26864
11385
20,000
4T1g → A2g (F)
4
4T1g → T1g (P)
3
[Ni(HNAPTS)2]
3A2g → T2g(F)
3A2g(F) → T1g(F)
3
3A2g(F) → T1g(F)
3
Spin forbidden
2B1g→2A1g, 2Eg
[Cu(HNAPTS) NH3]

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MISHRA et al, Orient. J. Chem., Vol. 29(4), 1651-1656 (2013)
Table 4: IR Spectral bands (cm-1) of ligand and complexes
Ligand
Complexes
HNAPTS
[Co(HNAPTS)2]
[Ni(HNAPTS)2]
[Cu(HNAPTS)NH3] Assignment
3380
3195
3090
1580
3380
3385
3380
N – H
stretching
O – H
(H- bonded)
C – H
stretching
C=N
3105
1575
3100
1570
3105
1580
stretching
N – H bending
C – N stretching
C – O
1405
1385
1260
1415
1395
1305
1400
1390
1285
1410
1395
1285
(phenolic)
Skeletal in
plane
1195
1175
1205
1175
vibrations
C=S stretching
Characteristic vibration
of 1,2,4 –
1155
1135 1065
1045
1145
11401070
1050
1140
11301070
1040
1135
11251075
1030
trisubstituted
benzene ring
C – N bending
Skeletal
910-920
820
920-930
820
915-925
820
910-920
820
vibrations
M – N bond
M – O bond
M – S bond
530
505
375
540
480
330
535
495
285
Copper (II) has d9 configuration which
Because of the relatively low symmetry
makes Cu (II) subject to John – Teller distortion, of the environments in which the Cu2+ ion is
if placed in an environment of cubic like regular characteristically found, detailed interpretation of
octahedral or tetrahedral symmetry and this has a spectra and magnetic properties are somewhat
profound effect on all its stereochemistry27.
complicated even though one is dealing with the
equivalent of a one – electron case.
The typical distortion is an elongation along
one four fold axis, so that there is planar array of four
The molar conductance values suggest
short Cu-L bonds with two trans long ones. In the non – electrolytic nature of this complex while I.R.
limit of course, the elongation leads to a situation band near 655 cm-1 suggests M – NH3 bonding.
indistinguishable from square co – ordination as
found in many discrete complexes of Cu (II) . Thus
The magnetic moment of Cu (II) complex
the cases of tetragonally distorted “Octahedral” co correspond well with the presence of one unpaired
– ordination and square co - ordination cannot be electron and gives on specific information about their
sharply differentiated.
stereochemistries. The µeff value of Co(II) complex
(4.15 BM) indicate the presence of three unpaired
electron in the complex whereas µeff for Ni(II) complex

MISHRA et al, Orient. J. Chem., Vol. 29(4), 1651-1656 (2013)
1655
Fig. 1: 2 – Hydroxy – 4 – nitro aceto phenone thiosemicarbazone
3 T1g(P)
3 T1g(F)
Field Strength
Fig. 2: Orgel diagram of Ni(II) complex
Fig. 3: bis - (2- hydroxy - 4 - nitro
acetophenone thio semicarbazone) Co (II)
Fig. 4: bis - (2- hydroxy - 4 - nitro
acetophenone thio semicarbazone) Ni(II)
Fig. 5: Mono ammine 2- hydroxy - 4 - nitro
acetophenone thio semicarbazone Cu(II)
(3.05 BM) suggests presence of two unpaired
electron in the complex.
CONCLUSION
Thiosemicarbazone metal complexes have
been studied for a long time. The crystallographic
data available to date is also very large but the study
of the way thiosemicarbazone metal complexes
interact with biological systems requires much
attention. More light is needed on the grey zone
between chemistry and molecular biology.
Taking all these facts into consideration,
along with their elemental analysis data the most
probable structures of these complexes are given
below in figure 3, 4 & 5.

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