Electronic, epr and magnetic studies of Co(II), Ni(II) and Cu(II) complexes with thiosemicarbazone (L1) and semicarbazone (L2) derived from pyrole-2-carboxyaldehyde

Article abstract of DOI:10.1016/j.saa.2006.07.051

Co(II), Ni(II) and Cu(II) complexes are synthesized with thiosemicarbazone (L¹) and semicarbazone (L²) derived from pyrole-2-carboxyaldehyde. These complexes are characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, mass, IR, electronic and EPR spectral studies .The molar conductance measurements of the complexes in DMSO correspond to non-electrolytic nature except Co(L¹)₂(NO₃)₂ and Ni(L¹)₂(NO₃)₂ complexes which are 1:2 electrolytes. All the complexes are of high-spin type. On the basis of spectral studies an octahedral geometry may be assigned for Co(II) and Ni(II) complexes except Co(L¹)₂(NO₃)₂ and Ni(L¹)₂(NO₃)₂ which are of tetrahedral geometry. A tetragonal geometry may be suggested for Cu(II) complexes.

Full text of DOI:10.1016/j.saa.2006.07.051

Spectrochimica Acta Part A 67 (2007) 697–701
Electronic, epr and magnetic studies of Co(II), Ni(II) and Cu(II) complexes
with thiosemicarbazone (L1) and semicarbazone (L2) derived
from pyrole-2-carboxyaldehyde
Sulekh Chandra∗, Anil Kumar
Department of Chemistry, Zakir Husain College, J.L.N. Marg, New Delhi 110002, India
Received 20 May 2006; accepted 25 July 2006
Abstract
Co(II), Ni(II)andCu(II)complexesaresynthesizedwiththiosemicarbazone(L1)andsemicarbazone(L2)derivedfrompyrole-2-carboxyaldehyde.
These complexes are characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, mass, IR, electronic and EPR
spectral studies .The molar conductance measurements of the complexes in DMSO correspond to non-electrolytic nature except Co(L1)2(NO3)2
and Ni(L1)2(NO3)2 complexes which are 1:2 electrolytes. All the complexes are of high-spin type. On the basis of spectral studies an octahedral
geometry may be assigned for Co(II) and Ni(II) complexes except Co(L1)2(NO3)2 and Ni(L1)2(NO3)2 which are of tetrahedral geometry. A
tetragonal geometry may be suggested for Cu(II) complexes.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Anti HIV; Molar conductance; IR spectrum
1. Introduction
2. Experimental
Thiosemicarbazones usually act as chelating ligands with
transition metal ion, bonding through the sulphur and hydrazine
nitrogen atom. Thiosemicarbazones and their complexes have
received considerable attention because of their pharmacologi-
cal activities [1]. The metal complexes show more activities as
compared to the free thiosemicarbazones and semicarbazones.
Theymayhavenumerousapplications, e.g. anticancer[2], fungi-
cides, antibacterial [3,4], antiviral [5,6], antifungal [7,8], anti
HIV [9], antitumour [10] and other biological activities [11–13].
Particularly first row of transition metal complexes with such
ligands have a wide range of biological activities [14–18].
In view of the above applications it is highly desirable to syn-
thesize and characterize transition metal complexes with such
ligands. In the present paper we report the synthesis and charac-
terization of complexes with thiosemicarbazone (L1) and semi-
carbazone (L2) (Fig. 1) derived from pyrole-2-carboxyaldehyde.
All the chemicals used were of analytical grade and procured
form Sigma–Aldrich. Metal salts were purchased from E. Merck
and were used as received.
2.1. Preparation of ligands
Ligands L1 and L2 were prepared by following methods.
2.1.1. Ligand L1
Hot ethanolic solution (20 mL) of a pyrole-2-carboxyal-
dehyde (0.95 g, 0.01 mol) was mixed with hot ethanolic solu-
tion of thiosemicarbazide (0.95 g, 0.01 mol). The contents were
refluxed for about 2–3 h on a water bath. On cooling the con-
tents the white colored compound separated out. The same was
filtered, washed with 50% ethanol and dried in vacuum over
P4O10. Yield 72%, mp 153–155 ◦C. Elemental analysis found
% C 43.0, H 4.6, N 33.5 calculated for C6H8N4S (molecular
mass 168 amu) % C 42.8, H 4.8, N 33.31.
2.1.2. Ligand L2
∗
Corresponding author.
An aqueous solution (20 mL) of semicarbazone HCl (1.11 g,
0.01 mol) was added to a ethanolic solution (20 mL) of pyrole-
E-mail addresses: schandra 00@yahoo.com (S. Chandra),
anil sharma957@yahoo.com (A. Kumar).
1386-1425/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2006.07.051

698
S. Chandra, A. Kumar / Spectrochimica Acta Part A 67 (2007) 697–701
Fig. 2. Mass spectrum of the ligand L1.
Fig. 1. Structure of ligands: Y = S, for L1; Y = O, for L2.
169 amu corresponding to the molecular ion (M+ + 1) C6H8N4S.
It also shows a peak at 108 amu corresponding to loss of
(–CSNH2) and various other fragments (Fig. 2).
2-carboxyaldehyde (0.95 g, 0.01 mol) in the presence of sodium
acetate (1.36 g, 0.01 mol). The reaction mixture was stirred vig-
orously for around an hour. The crystalline white product which
formed was collected by filtration, washed several times with
hot water and dried in vacuum over P4O10. Yield 78%, mp
203–206 ◦C. Elemental analysis found % C 47.8, H 5.0, N 36.9
calculated for C6H8N4O (molecular mass 152 amu) % C 47.36,
H 5.3, N 36.8.
3.2. Ligand L2
The IR spectrum of ligand L2 shows bands at 3380 and
3171 cm−1 which may be assigned to –NH2 and –NH group,
respectively. The band ν(–C N) appeared at 1601 cm−1. The
mass spectrum of free ligand L2 confirm the proposed formula
by showing a peak at 153 amu corresponding to the molecu-
lar ion (M+ + 1) C6H8N4O. It also shows a peak corresponding
to loss of (–CONH2) at 108 amu and various other fragments
(Fig. 3).
2.2. Synthesis of complexes
Hot ethanolic solution (20 mL) of corresponding metal salts
(0.005 mol for each case) was mixed with hot ethanolic solution
of the respective ligand (0.01 mol) and refluxed for 3–4 h on a
water bath. On cooling the contents, the colored complex sepa-
rated out in each case. The same was filtered, washed with 50%
ethanol and dried in vacuum over P4O10. Purity of the complexes
was checked by TLC.
3.3. Complexes
On complexation the bands corresponding to ν(–C N) and
ν(–C S) (in case of thiosemicarbazone) shifted towards lower
side (around Ca 20–30 cm−1) suggest that the ligand acts
as bidentate chelating agent coordinating through nitrogen of
ν(–C N) group and sulphur of ν(–C S) group. In case semi-
carbazone the band of ν(–C N) and the band of ν(–C O)
shifted towards lower side (around Ca 20–30 cm−1) suggests
that the ligand also acts as bidentate chelating agent coordinat-
ing through nitrogen of ν(–C N) group and oxygen of ν(–C O)
group.
2.3. Physical measurements
The C, H, N was analyzed on a Carlo-Erba1106 ele-
mental analyzer. Molar conductance was measured on the
Eleco (CM82T) conducting bridge. Magnetic susceptibility
was measured at room temperature on a Gouy balance using
CuSO4·5H2O as a calibrant. Mass spectra were recorded on
JEOL, JMS.DX-303 Mass spectrophotometer. IR spectra (KBr)
were recorded on a FTIR spectrum BX-II spectrophotometer.
The electronic spectra were recorded in DMSO on Shimadzu
UVmini-1240spectrophotometer. EPRspectraofthecomplexes
were recorded as polycrystalline sample at LNT for Co(II) com-
plexes and at room temperature for Cu(II) complexes on E4-EPR
spectrometer using DPPH as the g-marker.
On the basis of elemental analysis the complexes were
found to have the composition as shown in Table 1.
3. Results and discussion
3.1. Ligand L1
The IR spectrum of ligand L1 shows bands at 3380 and
3171 cm−1 which may be assigned to –NH2 and –NH groups,
respectively. The bands due to ν(–C S) and ν(–C N) groups
appeared at 1107 and 1597 cm−1. The mass spectrum of free
ligand L1 confirms the proposed formula by showing a peak at
Fig. 3. Mass spectrum of the ligand L2.

S. Chandra, A. Kumar / Spectrochimica Acta Part A 67 (2007) 697–701
699
Table 1
Elemental analysis and molar conductance data of complexes
Complex
Molar conductance
Color
mp (◦C)
Yield (%)
Elemental analysis data found (calculated)
(ꢀ−1 cm2 mol−1
)
M
C
H
N
Co(L1)2Cl2
11
120
15
10
14
150
12
145
22
13
16
Purple
Black
Black
Pink
Bluish brown
Dark brown
Brown
Light green
Brown
Black
Dark green
Black
195
200
243
245
200
205
245
238
190
187
235
227
67
65
62
60
60
62
62
61
62
59
62
60
12.40 (12.64)
10.25 (10.73)
13.35 (13.58)
12.36 (12.10)
12.43 (12.60)
11.55 (11.31)
13.31 (13.53)
12.28 (12.06)
12.88 (12.69)
12.36 (12.13)
14.24 (14.48)
12.68 (12.92)
30.72 (30.90)
26.00 (26.23)
33.41 (33.18)
29.23 (29.57)
30.70 (30.92)
27.59 (27.76)
33.53 (33.20)
29.34 (29.58)
22.54 (28.76)
27.77 (27.50)
32.71 (32.83)
29.52 (29.29)
3.20 (3.43)
2.68 (2.91)
3.46 (3.68)
3.53 (3.28)
3.60 (3.43)
3.29 (3.08)
3.42 (3.68)
3.03 (3.28)
3.42 (3.19)
3.23 (3.05)
3.40 (3.64)
3.50 (3.25)
24.27 (24.03)
25.28 (25.50)
26.08 (25.81)
28.53 (28.75)
24.28 (24.04)
26.73 (26.99)
25.58 (25.82)
28.53 (28.76)
22.59 (22.37)
26.57 (26.74)
25.30 (25.53)
28.69 (28.48)
Co(L1)2(NO3)2
Co(L2)2Cl2
Co(L2)2(NO3)2
Ni(L1)2Cl2
Ni(L1)2(NO3)2
Ni(L2)2Cl2
Ni(L2)2(NO3)2
Cu(L1)2Cl2
Cu(L1)2(NO3)2
Cu(L2)2Cl2
Cu(L2)2(NO3)2
175
IR spectra of Co(L1)2(NO3)2 and Ni(L1)2(NO3) complexes
showsharpandstrongbandat1384 cm−1 indicatethatthenitrate
group is uncoordinated. IR spectra of nitrate complexes of Co(II)
and Ni(II) with L2 display three absorption bands around at
1415–1440, 1290–1320 and 1020–1050 cm−1 suggesting that
both the nitrate groups are coordinated to the metal ion (Fig. 4)
[20–23].
The molar conductance measurements of the complexes in
DMSO correspond to non-electrolytic nature [19] except
Co(L1)2(NO3)2 and Ni(L1)2(NO3)2 complexes which are 1:2
electrolyte. Thus all the complexes may be formulated as
[M(L)2X2] where M = Cu(II), Co(II) and Ni(II) and X = Cl−,
−
NO3 [L = L1 and L2] except [Co(L1)2](NO3)2 and [Ni(L1)2]
(NO3)2.
Fig. 4. IR spectral bands of the anions.

700
S. Chandra, A. Kumar / Spectrochimica Acta Part A 67 (2007) 697–701
3
3
3
3
3
Table 2
transitions A2g(F) → T2g, A2g(F) → T1g(F), A2g(P) →
3T1g (P) corresponding to an octahedral geometry The nitrato
complex of Ni(II) with L1 under study have medium inten-
sity band around at 9000 cm−1 assigned as ν1. The band at
10,000–15,000 cm−1 corresponds to ν2 and it is not split, as
the excited state is orbitally non-degenerates. The ν3 tran-
sition appears at 14,000–25,000 cm−1 indicates tetrahedral
geometry.
Magnetic moment (BM) and electronic spectral data (cm−1) of complexes
Complex
μ eff BM
Electronic spectral data
ν1
ν2
ν3
Co(L1)2Cl2
4.87
4.91
4.88
4.90
2.92
2.95
3.01
3.98
2.06
1.98
1.88
1.90
9,400
5,590
9,396
6,115
9,620
7,900
9,770
9,620
13,280
13,220
15,742
15,290
14,380
14,890
14,420
15,500
14,560
14,640
15,250
14,525
16,680
16,640
16,600
19,400
21,090
21,000
21,360
21,150
25,060
24,000
24,600
24,000
–
Co(L1)2(NO3)2
Co(L2)2Cl2
Co(L2)2(NO3)2
Ni(L1)2Cl2
Ni(L1)2(NO3)2
Ni(L2)2Cl2
3.6. Cobalt(II) complexes
Ni(L2)2(NO3)2
Cu(L1)2Cl2
At room temperature all the complexes under study show
magnetic moment in the range 4.87–4.91 BM (Table 2) corre-
sponding to three unpaired electrons. The electronic spectra of
Co(II) complexes (except nitrate complex with L1) display elec-
tronic spectral bands in the range 7000–9500, 14,000–17,000
and 20,000–21,500 cm−1. These may be assigned to the
Cu(L1)2(NO3)2
Cu(L2)2Cl2
–
–
–
Cu(L2)2(NO3)2
4
4
4
4
following transitions T1g(F) → T2g(F), T1g(F) → A2g(F),
3.4. Copper (II) complexes
4T1g(F) → T1g(P) characteristic to an octahedral geometry
4
whereas the nitrate complex with L1 show three electronic
spectral bands around 5000, 8000 and 19,000 cm−1 correspond-
Magnetic moment of all the Cu(II) complexes at room tem-
perature lie in the range 1.88–2.06 BM corresponding to one
unpaired electron (Table 2). The electronic spectra of six coor-
dinated Cu2+ complexes have either D4h or C4v symmetry and
the Eg and T2g levels of the 2D free ion term will split into B1g,
A1g, B2g, Eg levels, respectively. Thus three spin allowed transi-
tion are expected in the visible and near IR region. But only a few
complexes are known in which such bands are resolved either by
“Gaussian analysis” or by “single crystal polarization” studies.
These Cu(II) complexes under study give rise absorption spec-
4
4
4
4
ing to the following transitions A2 → T2(F), A2 → T1(F),
4A2 → T1(P) characteristic to tetrahedral geometry. The F
State of d7 in an octahedral crystal field is split into three states.
Since these states are connected by the spin orbit coupling the
spin lattice relaxation times are short making epr measurements
possible only at very low temperature. EPR spectra of the com-
plexes recorded as polycrystalline sample at liquid nitrogen
temperature and g values are given in Table 3.
4
4
tral band in the range 13,220–15,750 and 16,260–20,000 cm−1
.
3.7. Ligand field parameters
These bands have been assigned to the following transition in
order of increasing energy [24,25]:
Various ligand field parameters are calculated for the com-
plexes. The value of Dq in Co(II) complexes were calculated
from transition energy ratio diagram using the ν3/ν2 ratio[30].
The Nephelauxetic parameter β was readily obtained by using
the relation β = B (complex)/B (free ion), where B free ion
for Ni(II) is 1041 cm−1 and for Co(II) is 1120 cm−1 [31,32].
The β lies in the range of 0.61–0.95 (Table 3). These values
indicate the appreciable covalent character of metal ligand σ
bond.
2
2
2B1g → A1g,
2B1g → A2g.
EPR spectra of Cu(II) complexes were recorded as poly-
crystalline sample on X-band at frequency 9.5 GHz under the
magnetic field strength 3400 Gauss. All the complexes show
anisotropic EPR spectra [26]. The g values have been calcu-
lated by Kivelson’s method [27]. G = (g11 − 2)/(g1 − 2), which
measures the exchange interaction between copper centers in
the polycrystalline solid sample of the complex have also been
calculated. According to Hathaway [28,29] if the value of G
is above four then exchange interaction is negligible, if how-
ever the value of G is less than four it indicates considerable
exchange interaction in the solid complexes. In the complexes
reported here the G value are less than 4 indicating the exchange
interaction in solid complexes.
Table 3
Ligand field parameter and g value of complexes
Complex
g
LFSE (K J mol−1
)
Dq (cm−1
)
β
Co(L1)2Cl2
1.95
1.87
1.88
1.83
–
–
–
–
1.98
2.00
2.07
2.04
134
80
134
87
137
113
140
137
–
940
559
939
611
962
790
977
962
–
0.84
0.76
0.86
0.70
0.68
0.95
0.67
0.61
–
Co(L1)2(NO3)2
Co(L2)2Cl2
Co(L2)2(NO3)2
Ni(L1)2Cl2
3.5. Nickel(II) complexes
Ni(L1)2(NO3)2
Ni(L2)2Cl2
The value of magnetic moments for the complexes under
study lies in the range from 2.92 to 3.98 BM (Table 2).
Under study electronic spectra of the chloro and nitrate com-
plexes (except nitrate complex with ligand L1) show elec-
tronic bands in the range 8580–13,000, 11,000–20,000 and
19,000–27,000 cm−1 and may be assigned to the spin allowed
Ni(L2)2(NO3)2
Cu(L1)2Cl2
Cu(L1)2(NO3)2
Cu(L2)2Cl2
–
–
–
–
–
–
–
–
–
Cu(L2)2(NO3)2

S. Chandra, A. Kumar / Spectrochimica Acta Part A 67 (2007) 697–701
[15] A.M. Dhiman, K.N. Wododkar, Ind. J. Chem. B 40 (2001) 636.
701
Acknowledgements
[16] E.M. Jouad, A. Riou, M. Allian, M.A. Khan, G.M. Bouet, Polyhedron 20
(2001) 67.
We are thankful to DRDO, New Delhi for financial assis-
tance, RSIC, IIT Bombay for recording EPR spectra. We are
also thankful to ACBR, USIC Delhi University for recording IR
and mass spectra.
[17] S. Chandra, K. Gupta, Trans. Met. Chem. 27 (2002) 196.
[18] Z. Xinde, C. Wang, Z. Lu, Y. Dang, Trans. Met. Chem. 22 (1997) 13.
[19] W.G. Geary, Coord. Chem. Rev. 7 (1971) 81.
[20] K. Nakamoto, Infrared and Raman Spectra of Coordination Compounds,
Wiley–Interscience, New York, 1970.
[21] C.R.K. Rao, P.S. Zacharias, Polyhedron 16 (1977) 1201;
S. Chandra, L.K. Gupta, Spectrochim. Acta A 60 (2004) 3079.
[22] M. Shakir, S.P. Varkey, P.S. Hameed, Polyhedron 12 (1993) 2775;
S. Chandra, L.K. Gupta, Spectrochim. Acta A 60 (2004) 2767.
[23] M. Shakir, O.S.M. Nasman, A.K. Mohamed, S.P. Varkey, Ind. J. Chem.
(1996) 710.
References
[1] N.K. Singh, A. Srivastava, Trans. Met. Chem. 25 (2000) 133.
[2] M. Wang, L.F. Wang, Y.Z. Ligands, Q.X. Li, Trans. Met. Chem. 26 (2001)
307.
[3] N.N. Gulerman, S. Rollas, H. Erdeniz, M. Kiraj, J. Pharm. Sci. 26 (2001)
1.
[24] V.V. Pavlishchuk, S.P. Kolotilov, A.W. Addison, R.J. Butche, E. Sinn, J.
Chem. Soc., Dalton Trans. (2000) 335.
[4] S.D. Dhumwad, K.B. Gudasi, T.R. Goudar, Ind. J. Chem. A 33 (1994) 320.
[5] P. Tarasconi, S. Capacchi, G. Pelosi, M. Cornia, R. Albertini, A. Bonati,
P.P. Dall, P. Luunghi, S. Pinelli, Bioorg. Med. Chem. 8 (2000) 154.
[6] K.H. Reddy, P.S. Reddy, P.R. Babu, Trans. Met. Chem. 25 (2000) 154.
[7] D.X. West, S.L. Dietrich, I. Thientanavanich, C.A. Brown, A.E. Liberta,
Trans. Met. Chem. 19 (1994) 320.
[25] A.B.P. Lever, Inorganic Electronic Spectroscopy, 2nd ed., Elsevier, Ams-
terdam, 1984.
[26] S. Chandra, K. Gupta, S. Sharma, Synth. React. Inorg. Met. Org. Chem. 31
(2001) 1205.
[27] D. Kivelson, R. Neiman, J. Chem. Phys. 35 (1961) 149.
[28] R.S. Drago, Physical Method in Chemistry, W.B. Saunders Company, Lon-
don, 1977, p. 647.
[29] B.J. Hathaway, D.E. Billing, Coord. Chem. Rev. 6 (1970) 143;
B.J. Hathaway, R.J. Dudley, Br. J. Chem. Soc. (1970) 1725.
[30] A.B.P. Lever, Crystal Field Spectra, Inorganic Electronic Spectroscopy, 1st
ed., Elsevier, Amsterdam, 1968, p. 249.
[8] H. Singh, L.D.S. Yadav, S.B.S. Mishra, J. Inorg. Nucl. Chem. 43 (1981)
1701.
[9] S. Chandra, Sangeetika, Spectrochim. Acta Part A 60 (2004) 147;
L. Mishra, A.K. Singh, Y. Maeda, J. Ind. Chem. Soc. 82 (2005) 879.
[10] S. Chandra, L.K. Gupta, K.K. Sharma, J. Saudi Chem. Soc. 9 (2005) 131;
M.A. Akbar, H.A. Mirza, A. Monsur, M. Nazimuddin, Polyhedron 20
(2001) 1045.
[11] D. Jamal, M.A. Quaraishi, J. Electrom. Soc. India 49 (2000) 56.
[12] N.K. Singh, S.B. Singh, Ind. J. Chem. 40A (2001) 1070.
[13] V. Mishra, S.N. Pandeya, S. Anathan, Acta Pharm. Turc. 42 (2000) 139.
[14] S. Chandra, K. Gupta, Trans. Met. Chem. 27 (2002) 329.
[31] S. Chandra, L.K. Gupta, K. Gupta, J. Ind. Chem. Soc. 81 (2004) 833.
[32] R.R. Fenton, R. Gauci, P.C. Junk, L.F. Lindoy, R.C. Luckay, G.V. Mee-
han, J.R. Price, P. Turner, G. Wei, J. Chem. Soc., Dalton Trans. (2002)
2185;
C.C. Silviacarvelho, R. Delgado, M.G.V. Drew, V. Felix, B.J. Goodfellow,
J. Chem. Soc., Dalton Trans. (2003) 3172.