Mn(II) and Cu(II) complexes of a bidentate Schiff's base ligand: Spectral, thermal, molecular modelling and mycological studies

Article abstract of DOI:10.1016/j.saa.2013.07.074

Complexes of manganese(II) and copper(II) of general composition M(L) ₂X₂ have been synthesized [L = 2-acetyl thiophene thiosemicarbazone and X = Cl^- and NO3-]. The elemental analysis, molar conductance measurements, magnetic susceptibility measurements, mass, IR, UV, NMR and EPR spectral studies of the compounds led to the conclusion that the ligand acts as a bidentate manner. The Schiff's base ligand forms hexacoordinated complexes having octahedral geometry for Mn(II) and tetragonal geometry for Cu(II) complexes. The thermal studies suggested that the complexes are more stable as compared to ligand. In molecular modelling the geometries of Schiff's base and metal complexes were fully optimized with respect to the energy using the 6-31g(d,p) basis set. The mycological studies of the compounds were examined against the plant pathogenic fungi i.e. Rhizoctonia bataticola, Macrophomina phaseolina, Fusarium odum.

Full text of DOI:10.1016/j.saa.2013.07.074

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 1–8
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Mn(II) and Cu(II) complexes of a bidentate Schiff’s base ligand: Spectral,
thermal, molecular modelling and mycological studies
⇑
Monika Tyagi, Sulekh Chandra , Prateek Tyagi
Department of Chemistry, Zakir Husain Delhi College, University of Delhi, JLN-Marg, New Delhi 110002, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
Synthesis and characterization of
ligand by various spectral methods.
Mn(II) and Cu(II) complexes were
found to octahedral and tetragonal
geometry, respectively.
ꢀ
ꢀ
ꢀ
Thermal data suggested that
complexes are more stable as
compared to ligand.
In vitro antifungal activity of
synthesized compounds were
screened against fungal species.
All the complexes were found to be
more active as compared to parent
ligand.
(a)
(b)
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 17 April 2013
Received in revised form 3 July 2013
Accepted 21 July 2013
Available online 8 August 2013
2 2
Complexes of manganese(II) and copper(II) of general composition M(L) X have been synthesized [L = 2-
ꢁ
ꢁ
acetyl thiophene thiosemicarbazone and X = Cl and NO ]. The elemental analysis, molar conductance
3
measurements, magnetic susceptibility measurements, mass, IR, UV, NMR and EPR spectral studies of
the compounds led to the conclusion that the ligand acts as a bidentate manner. The Schiff’s base ligand
forms hexacoordinated complexes having octahedral geometry for Mn(II) and tetragonal geometry for
Cu(II) complexes. The thermal studies suggested that the complexes are more stable as compared to
ligand. In molecular modelling the geometries of Schiff’s base and metal complexes were fully optimized
with respect to the energy using the 6-31g(d,p) basis set. The mycological studies of the compounds were
examined against the plant pathogenic fungi i.e. Rhizoctonia bataticola, Macrophomina phaseolina, Fusar-
ium odum.
Keywords:
Mn(II) and Cu(II) complexes
Thiosemicarbazone
Spectral characterization
Ths molecular modelling
Mycological studies
Ó 2013 Elsevier B.V. All rights reserved.
Introduction
base having thiosemicarbazide moiety can coordinate to metal as
neutral molecules or after deprotonation as anionic ligands and
The Schiff base contain azomethine group (ACH@NA). They are
used as substrates in the preparation of industrial and biologically
active compounds via ring closure, cycloaddition and replacement
reactions [1]. Schiff’s base ligands are potentially capable of form-
ing stable complexes with most transition metal ions which served
as model compounds for biologically important species [2]. Schiff
can adopt variety different coordination modes. The possibility of
their being able to transmit electronic effects between a reduce
unit and metal centre is suggested by the delocalization of the
bonds in the thiosemicarbazone chain [3]. Thiosemicarbazones
and their metal complexes have considerable interest because of
their biological activities, such as antitumour, antiviral, anticancer,
antifungal, antibacterial and antimalarial [4–10]. They also have
been used as drugs and are reported to possess a wide variety of
biological activities against bacteria, fungi and certain type of
tumors and also are useful model for bioinorganic processes
⇑
Corresponding author. Tel.: +91 1122911267; fax: +91 1123215906.
E-mail addresses: mnk02tyg@yahoo.co.in (M. Tyagi), schandra_00@yahoo.com
(
S. Chandra).
1
386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.07.074

2
M. Tyagi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 1–8
[
11,12]. Taking into consideration the above facts, Mn(II) and Cu(II)
vent and TMS as internal standard. The electronic spectra were re-
corded in DMSO on Shimadzu UV mini-1240 spectrophotometer.
Thermogravimetric analysis (TGA and DTG) were carried out in dy-
namic nitrogen atmosphere (30 ml/min) with a heating rate of
10 C/min using a Schimadzu TGA-50H thermal analyzer. EPR spec-
tra of the Mn(II) and Cu(II) complexes were recorded as polycrys-
talline sample at room temperature on E4- EPR spectrometer
using the DPPH as the g-marker.
complexes of Schiff base derived from condensation of thi-
osemicarbzide and 2-acetyl thiophene were synthesized. The syn-
thesized compounds were characterized using various spectral
techniques and evaluated for their mycological studies against
plant pathogenic fungi i.e. Rhizoctonia bataticola, Macrophomina
phaseolina, Fusarium odum.
Experimental
Molecular modelling studies
Materials and methods
The DFT calculations were performed using the B3LYP three
parameter density functional, which includes Becke’s gradient ex-
change correction [13], the Lee, Yang, Parr correlation functional
All the chemicals used were of Anala R grade and received from
Sigma–Aldrich and Fluka. Metal salts were purchased from E.
Merck and were used as received.
[
14] and the Vosko, Wilk, Nusair correlation functional [15]. The
geometries of Schiff base and metal complexes were fully opti-
mized with respect to the energy using the 6-31g(d,p) basis set
using the Gaussian 09W suite [16].
Synthesis of ligand
Hot ethanolic (20 mL) solution of thiosemicarbazide (0.91 g,
0
(
8
.01 mol) and an ethanolic (20 mL) solution of 2-acetyl thiophene
1.26 g, 0.01 mol) were mixed. This mixture was refluxed at 70–
0 °C for 2–3 h. On cooling the reaction mixture, white product
was precipitated out. It was filtered off, washed with cold EtOH
and dried under vacuum over P 10. Yield 70%, mp 161 °C. Elemen-
tal analyses Found (Calcd.) for C : C, 42.29 (42.21); H, 4.48
4.52); N, 21.05 (21.10)%. Scheme of synthesis of ligand is given in
Biological screening
The Poison food Technique [17,18] was employed to examine
the synthesized compounds against the fungi, i.e. R. bataticola, M.
phaseolina and F. odum for their fungicidal investigations. DMSO
and Bavistin were employed as a control and a standard fungicide,
respectively. The mycelial growth of fungi (mm) in each petriplate
was measured diametrically and growth inhibition (I) was calcu-
lated using the formula: I (%) = (CT)/C ꢃ 100, where I = % Inhibition,
C = Radial diameters of the colony in control, T = Radial diameter of
the colony in test compound.
4
O
7 9 3 2
H N S
(
Scheme 1.
Synthesis of metal complexes
Hot ethanolic solution (10 mL) of metal salt (nitrate or chloride)
1 mmol) were mixed with a hot ethanolic solution (15 mL) of the
(
respective ligand (2 mmol). The reaction mixture was refluxed for
Results and discussion
8
0
–10 h at 80–85 °C. On keeping the resulting mixture overnight at
°C, the coloured product was separated out, which was filtered
The complexes were synthesized by reacting ligand with the
metal ions in 2: 1 M ratio in ethanolic medium. On the basis of ele-
mental analysis, the complexes were found to have the composi-
tion, as given in Table 1. The molar conductance of the
off, washed with cold ethanol and dried under vacuum over
4
P O
10. The purity of the complexes was checked by TLC. TLC anal-
ysis was performed on silica gel using the solvent system benzene/
acetone (1:2) as eluent.
ꢁ
1
2
ꢁ1
complexes in DMSO lies in the range of 07–12
cating their non-electrolytic behaviour [19]. Thus the complexes
may be formulated as [M(L)X ] [where M = Mn(II), and Cu(II),
X
cm mol indi-
Analysis
2
ꢁ
ꢁ
X = Cl , NO ].
3
The carbon and hydrogen were analyzed on Carlo-Erba 1106
elemental analyzer. The nitrogen content of the complexes was
determined using Kjeldahl’s method. Molar conductance was mea-
sured on the ELICO (CM82T) conductivity bridge. Magnetic suscep-
tibilities were measured at room temperature on a Gouy balance
Mass spectrum
The electronic impact mass spectrum of ligand showed a molec-
using CuSO
was recorded on JEOL, JMS – DX-303 mass spectrometer. IR spectra
KBr) were recorded on FTIR spectrum BX-II spectrophotometer.
NMR spectra were recorded with a model Bruker Advance DPX-
4
ꢂ5H
2
O as callibrant. Electronic impact mass spectrum
ular ion peak at m/z = 200 amu corresponding to species [C
7
H
9
N
3-
ꢁ
2
S ]
which confirms the proposed formula. It also shows series of
(
peaks at 16, 60, 75, 101, 123, 132 and 184 amu corresponding to
various fragments. The intensities of these peaks give the idea of
the stabilities of the fragments (Supplementary material).
3
00 spectrometer operating at 300 MHz using DMSO-d6 as a sol-
CH3
H
CH3
S
N
NH2
C
N
C
reflux 2-3 h
H2N
7
0-80º C
S
O
S
HN
C
H2N
S
Scheme 1. Structure of ligand.

M. Tyagi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 1–8
3
Table 1
Analytical data of Mn(II) and Cu(II) complexes.
Complexes
Colour
Yield (%)
M.p. (°C)
Elemental analysis found (calcd.) (%)
leff BM
M
C
H
N
[
Mn(L)
MnC14
Mn(L)
MnC14
Cu(L)
CuC14
Cu(L)
CuC14
2
Cl
2
]
N
Off
White
Off
White
Green
59
62
65
68
178
187
183
192
10.42
(10.50)
9.48
(9.53)
11.79
(11.84)
10.74
(10.77)
32.00
(32.06)
29.07
(29.12)
31.53
(31.58)
28.67
3.00
(3.40)
3.10
(3.12)
3.30
(3.38)
3.02
16.08
(16.03)
19.35
(19.41)
14.31
(14.36)
19.00
5.92
5.95
1.97
1.94
H
18
6
S
4
Cl
]
2
[
2 3 2
(NO )
H
18
N
]
8
O
S
6 4
[
2 2
Cl
H
18
N
6
S
4
Cl
2
[
2
(NO
3
2
) ]
Green
H
18
N
8
O
6
S
4
(28.72)
(3.07)
(19.14)
1
ꢁ1
H NMR spectrum
26,880–28,736 and 31,250–35,087 cm . These bands may be as-
6
4
4
6
4
4
4
signed to the
A
1g ? T1g( G),
A
A
1g ? E
g
,
A
1g ( G) (10B + 5C) and
1H NMR spectrum of ligand (Supplementary material) in DMSO
exhibit following signals: d 8.76 ppm (s) (1H, HN-CS), d 6.42 ppm
6
A
1g ? E
4
( D) (17B + 5C) and
4
6
1g ? T1g( P) transitions, respec-
4
4
g
tively, corresponding to an octahedral geometry [26]. Electronic
spectra of Cu(II) complexes show the d–d transition bands in the
range 12,188–15,479, 18,621–19,132 and 24,402–27,322 cm
(
s) (2H, H
2 3
NA), d 2.3 ppm (s) (3H, CH ) and d 7.1–7.3 ppm (m)
ꢁ
1
(
3H, thiophene ring).
.
,
2
2
These bands correspond to
B
B
1g ? A1g (dx2–y2 ? dz2
1g ? E
)
m
1
2
2
and 2
2
IR spectra
B1g ? B2g (dx2–y2 ? dxy
)
m
2
g
(dx2–y2 ? dxz, dyz
)
m
3
and transitions, respectively [27]. An elongated tetragonal geome-
try has been assigned for Cu(II) complex. The spectra of all the
complexes have been vibronically assigned to D4h symmetry with
a dx2–y2 ground state.
The important IR bands of the compounds along with their
assignments are given in Table 2. In principle, the ligand can exhi-
bit thione-thiol tautomerism since it contains
ideANHAC@S functional group. The (SAH) band at 2565 cm is
absent in the IR spectrum of ligand but (NAH) band at
205 cm is present, indicating that in the solid state, the ligand
remains as the thione tautomer. The position of (C@N) band of
a thioam-
ꢁ
1
m
m
Electronic paramagnetic resonance spectra
ꢁ
1
3
m
EPR spectra of Mn(II) complexes were recorded at room tem-
perature as polycrystalline samples and in DMSO solution. The
polycrystalline spectra give an isotropic signal centered at 1.95–
2.06. In DMSO solution the complexes give well resolved six lines
due to hyperfine interaction between the unpaired electrons with
ꢁ1
the thiosemicarbazone appeared at 1592 cm is shifted towards
lower side in the complexes indicating coordination via the azome-
thine nitrogen [20,21]. This is also confirmed by the appearance of
ꢁ1
new band in complexes in the range of 450–475 cm , which has
been assigned to the (MAN) [22]. In the IR spectrum of ligand
the band appeared at 756 cm corresponding to
5
5
m
the Mn nucleus (I = 5/2). EPR spectra of the Cu(II) complexes
were recorded, at room temperature as polycrystalline samples,
on the X-band at 9.1 GHz under the magnetic field range 3000G.
The analysis of spectra of Cu(II) complexes (Supplementary mate-
rial) give g 2.12–2.21 and g 2.08–2.16. The trend g > g > 2.0023, ob-
served for the complexes, under study, indicate that the unpaired
electron is localized in the dx2–y2 orbital of the Cu(II) ion and the
spectral figures are characteristic for the axial symmetry. Tetrago-
nally elongated geometry is thus confirmed for the afore-said com-
plexes [28]. G = (g ꢁ 2)/(g ꢁ 2), which measure the exchange
interaction between the metal centres in a polycrystalline solid
has been calculated. According to Hathaway and Billing [29] if
G > 4 the exchange interaction is negligible, but G indicates consid-
erable exchange interaction in the solid complexes. The complexes
reported in this paper gives the ‘G’ value (Table 3) in the range
1.31–1.44, which is <4, indicating exchange interaction in the solid
complexes.
1
m
(C@S) is shifted
towards lower side. It indicates that thione sulphur coordinates
to the metal ion [23]. Thus, it may be concluded that behaves as
bidentate chelating agent coordinating through azomethine nitro-
gen and thiolate sulphur. The presence of bands at 1450–1410 (
m
5
),
ꢁ1
1
348–1320 (m ) and 1058–1025 (m ) cm , in the IR spectra of the
1 2
metal complexes suggest that both the nitrate groups are coordi-
nated to the central metal ion in a unidentate fashion [24].
Magnetic moments
The magnetic moment observed for Mn(II) complexes lies in the
range 5.92–5.95 BM corresponding to five unpaired electrons. At
room temperature Cu(II) complexes show magnetic moment in
the range 1.94–1.97 BM corresponding to one unpaired electron
[
25]. The observed magnetic moments of Mn(II) and Cu(II) com-
plexes are given in Table 1.
Thermal analysis
Electronic spectra
Schiff’s base and its metal lexes were studied by thermogravi-
metric analysis from ambient temperature to 800 °C in nitrogen
atmosphere. The TG curves were redrawn as % mass loss vs.
Electronic spectra of Mn(II) complexes exhibit four weak inten-
sity absorption bands in the range 18,182–18,349, 22,883–24,630,
Table 2
Important infrared spectral (cmꢁ1) bands and their assignments.
Compounds
Assignments
(NAH)
Bands due to anions
m
m
(C@N)
m(MAN)
m(MAS)
[
[
[
[
Mn(L)
2
Cl
(NO
2
]
3150
3195
3165
3240
1570
1582
1565
1576
462
450
475
470
318
305
322
312
) = 102 cm 1 indicating unidentate nature
ꢁ
Mn(L)
2
3
)
2
]
m
m
5
5
= 1450,
= 1410,
m
m
1
1
= 1348,
= 1320,
m
2
2
= 1058
= 1025
D
(
m
5
–
m
1
Cu(L)
Cu(L)
2
Cl
2
]
ꢁ
2
(NO
3 2
) ]
m
D
(
m
5
–
m
1
) = 90 cm 1 indicating unidentate nature

4
M. Tyagi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 1–8
Table 3
decomposition reaction are given in Table 4 together with evolved
moiety and the theoretical percentage mass losses thermal tech-
niques, such as thermogravimetric analysis (TGA and DTG), has
been successfully employed for the study of the energetic of inter-
actions of metal cations with biological species, such as amino
acids [30,31]. The weight loss profiles are analyzed the amount
or percent of weight loss at any given temperature, and the tem-
perature ranges of the degradation process were determined. Ther-
mal stability domains, melting points, decomposition phenomena
and their assignments for the Schiff, s base and its complexes are
Electronic spectral bands (cmꢁ1) and EPR spectral data of the complexes.
max (cm 1
ꢁ
)
g
g
g
G
Compounds
k
iso
[
[
[
[
Mn(L)
Mn(L)
Cu(L)
Cu(L)
2
Cl
2
]
18,182, 22,883, 26,880, 31,250
18,349, 24,630, 28,736, 35,087
12,188, 18,621, 24,402
–
–
–
–
1.95
2.06
–
–
2
(NO
3 2
) ]
2
Cl
2
]
2.12 2.08 2.10 1.44
2.21 2.16 2.17 1.31
2
(NO
3
2
) ]
15,479, 19,132, 27,322
temperature (TG) curves. Typical TG curves are presented in Fig. 1
and the temperature ranges and percentage mass losses of the
2 2 2 3 2 2 2 2 3 2
Fig. 1. TGA curves of (A) ligand (L), (B) [Mn(L) Cl ], (C) [Mn(L) (NO ) ], (D) [Cu(L) Cl ], and (E) [Cu(L) (NO ) ] complexes in nitrogen atmosphere.
Table 4
Thermoanalytical results (TG and DTG) for the Schiff’s base and its complexes.
Complexes
Stages
Temp. (K)
DTG max (°C)
Residual species
Decomposition species
Total losses (%)
Found
Calc.
100
C
H
7 9
N S
3 2
(L)
Ist
120–400
400–800
320
–
AC
3
H
5
N
3
S(organic moiety)
99.9
2nd
4 4
C H S (thiophene ring)
[
Mn(L)
2
Cl
2
]
N
Ist
2nd
120–300
300–800
280
435
MnS
AH
4
N
2
(hydrazine molecule)
Cl (organic moiety)
83.4
84.9
82.1
86.4
83.8
84.5
82.1
86.6
MnC14
H
18
6
S
4
Cl
2
C
14
H
14
N
S
4 3
2
[
Mn(L)
2
(NO
)
3 2
]
Ist
2nd
120–420
420–800
290
475
MnO
CuS
2
AC
2
H
4
2
N O
2
(2amido group)
MnC14
H
18
N
8
O
S
6 4
AC12
H
N O S (organic moiety)
14 6 2 4
[
Cu(L)
2
Cl
2
]
Ist
2nd
120–280
280–800
185
452
AH
N
4 2
(hydrazine molecule)
Cl (organic moiety)
CuC14
H
18
N
6
S
4
Cl
2
C
14
H
14
N S
4 3
2
[
Cu(L)
2
(NO
3
2
) ]
Ist
2nd
120–200
200–800
180
432
CuO
C
C
2
H
4
N
2
O
2
(2amido group)
(organic moiety)
CuC14
H
18
N
8
O
6
S
4
12
H
14
N
6
O
3
S
4

M. Tyagi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 1–8
5
Table 5
Optimized geometry of the ligand and metal complexes (bond lengths in Angstroms; bond angles in degrees).
Parametersa
Ligand (L)
[M(L
)XX ]b
0
[M(L
)XX ]
0
c
[M(L
)XX ]d
0
)XX ]e
0
[M(L
2
2
2
2
MAX
MAX
–
–
–
–
–
–
2.491
2.426
2.639
2.000
2.524
2.076
1.732
1.348
1.358
1.429
1.332
1.733
1.352
1.350
1.407
1.317
78.42
81.92
87.04
95.12
84.28
94.60
2.093
1.969
2.620
2.013
2.542
2.033
1.741
1.344
1.366
1.442
1.320
1.745
1.349
1.347
1.410
1.318
77.32
81.99
84.94
89.08
85.62
99.25
2.526
2.367
4.650
2.006
2.654
2.041
1.719
1.361
1.384
1.413
1.317
1.728
1.357
1.360
1.392
1.313
33.92
82.53
95.04
96.36
82.15
2.030
1.979
3.964
2.006
2.618
2.023
1.722
1.355
1.386
1.424
1.316
1.739
1.352
1.356
1.382
1.308
51.32
82.87
79.34
90.7
0
MAS
MAN
1
2
MAS
MAN
3
4
1
S AC
1
1.713
1.365
1.382
1.370
C
C
1
AN
AN
3
1
1
N
1
N
2
AN
AC
2
2
1.305
3
S AC
8
–
–
–
–
–
–
–
–
–
–
–
–
C
C
8
AN
8
AN
6
5
N
N
4
AN
AC
5
4
9
S
S
S
1
MN
MN
MX
2
4
3
1
1
N
2
N
4
MX
MX
2
1
85.16
113.53
144.44
S
X
3
MX
MX
2
110.32
146.84
1
2
174.95
176.23
L = 2-acetyl thiophene thiosemicarbazone.
a
See Scheme 1 for numbering.
b
c
0
0
M = Mn, X = Cl and X = Cl .
0
0
3
M = Mn, X = NO
M = Cu, X = Cl and X = Cl .
3
and X = NO .
d
e
0
0
0
0
3
M = Cu, X = NO
3
and X = NO .
Fig. 2. Geometry optimized structure of (a) Schiff base, (b) [Mn(L)
Cl
2 2
], (c) [Mn(L)
2
(NO
3
2 2 2 2 3 2
) ], (d) [Cu(L) Cl ], (e) [Cu(L) (NO ) ] (colour code: H-White, C-Grey, N-Blue, O-Red,
Mn = Brown, Cu-Black). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
summarized in Table 4. The overall loss of mass from the TG curves
is 83.40% for [Mn(L) Cl ], 84.92 for [Mn(L) (NO ] 82.14% for
Cu(L) Cl ] and 86.49% for [Cu(L) (NO ]. All the complexes show
two essential maxima peaks corresponding to mass loss. The first
sharp endothermic peak corresponding to complexes of [Mn(L)2-
Cl
2
] and [Cu(L)
2
Cl
2
] occurring between 120 and 300 °C may be
) and the second decompo-
2
2
2
3
)
2
due to loss of hydrazine molecule (N H
2 4
[
2
2
2
3
)
2
sition step in the range of 280–800 °C, correspond to the pyrolysis
of organic moiety. In nitrato complexes of Mn(II) and Cu(II) the first
sharp endothermic peak observed between 120 and 420 °C may be

6
M. Tyagi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 1–8
Table 6
Fungicidal screening data of compounds showing growth inhibition (%) at 250, 500
and 750 ppm concentrations after 7 days at 26 ± 1 °C.
CH3
Compounds
R. bataticola
M. phaseolina
F. odum
C
N
250 500 750 250 500 750 250 500 750
S
Ligand (L)
25
48
50
81
70
86
0
35
50
59
90
79
91
0
44 42
65 52
68 57
98 75
85 70
100 68
54
52
68
91
87
78
0
63 32
44
64
53
71
76
82
0
56
74
65
89
94
98
0
X
S
NH2
[
[
[
[
Mn(L)2Cl2]
Mn(L) (NO
Cu(L)2Cl2]
3 2
Cu(L) (NO ) ]
71 53
80 42
100 59
92 68
90 70
HN
C
2
3 2
) ]
C
M
2
Chlorothalonil
DMSO
NH
0
0
0
0
H N
S
2
X
N
C
S
due to loss of amido group and the second decomposition step
corresponding to the pyrolysis of organic moiety.
H C
3
Molecular modelling analysis
-
-
Where X= Cl , NO
3
and M= Mn(II) , Cu(II)
Geometry Optimization was done using B3LYP functional with
-31G(d,p) basis sets as incorporated in the Gaussian 09W pro-
Fig. 4. Suggested structure of Mn(II) and Cu(II) complexes.
6
gramme in gas phase. [Mn(L) Cl ] and [Mn(L) (NO ] complexes
2
2
2
3 2
)
have octahedral geometry with slight distortion. The two axial
positions are occupied by chloride ions/oxygen of nitrate ions
respectively, while the equatorial positions are being occupied by
nitrogen and sulphur atoms of the ligand. The two equatorial
are listed in Table 5. The optimized structure of Schiff base and
metal complexes are given in Fig. 2.
Mulliken population analysis method is used to determine the
Mulliken charges on ligand atoms and metal complexes. The com-
puted charges are given in Table 6. The charge of the Mn2+ ion in
the Free State is +2.0. It is seen that the positive charge of the metal
MnAS distances are 2.639 Å and 2.524 Å in [Mn(L)
while 2.620 Å and 2.542 Å in [Mn(L) (NO ] complex. The MnAN
bond distances are 2.000 Å and 2.076 Å in [Mn(L)
while 2.013 Å and 2.033 Å respectively in [Mn(L) (NO
The axial MnACl bond distances in [Mn(L) Cl
.491 Å and 2.426 Å respectively. Similarly the axial MnAO bond
distances in [Mn(L) (NO ] complex are 2.093 Å and 1.969 Å.
2 2
Cl ] complex
2
3 2
)
2
Cl
2
] complex
] complex.
2 2
ion decreases to +0.810 in [Mn(L) Cl ] complex, which indicates
2
3
)
2
that transfer of electrons from the ligands to the metal ion has oc-
curred and the coordination bonds have formed. To see how the
charge transfer occurs, we compared the values of partial atomic
2
2
] complex are
2
2
3 2
)
charges on the free ligand with that of the Mn(L)
which the charge transfer takes place.
2 2
Cl complex, in
The bond angles in the coordination sphere of Mn(II) complexes
are found approximately near to the perpendicular value. The S1-
2
+
According to Pearson’s HSAB concept, Mn is a hard acid and
AMnAN
are 78.42°, 87.04°, 94.60° and 95.12° respectively. The bond angle
Cl AMnACl is found to be 174.95°. Similar results are obtained
in case of [Cu(L) Cl ] and [Cu(L) (NO ] complexes, all the bond
lengths except CuAS bond have very close value to as compared
to Mn(II) complexes. The CuAS bond lengthens to 4.65 Å in
Cu(L) Cl ] complex and 3.96 Å in Cu(NO complex, which results
in strong distortion from regular octahedral geometry. It is due to
distortion that bond angle S ACuAN reduces to 33.92° in [Cu(L)2-
Cl ] complex and 51.92° in [Cu(L) (NO ]. The calculated bond
length and bond angle for the ligand and their metal complexes
2 1 3 2 2 2
, S AMnACl1, S AMnACl and N AMnACl bond angles
Cl1 is a hard base, while S is a soft base and N comes in bor-
ꢁ
2ꢁ
3ꢁ
derline. This indicates that there should be a stronger interaction
1
2
2
+
1ꢁ
2+
3ꢁ
2+
2ꢁ
between Mn & Cl than between Mn & N and Mn & S
respectively. Our calculations are in accord with this principle, as
2
2
2
3 2
)
1
ꢁ
ꢁ
there is a transfer of 0.862e from two chloride ions and 0.328e
are transferred from the rest if the ligand to Manganese metal. This
shows that a total of ꢄ1.119e is transferred to Mn(II) during the
complexation, and the net charge on the Mn(II) reduces to
ꢄ0.810e. Similar behaviour in charge transfer is noted in case of
1
[
2
2
3 2
)
1
2
2
2
3 2
)
[
2 3 2 2 2 2 3 2
Mn(L) (NO ) ], [Cu(L) Cl ] and [Cu(L) (NO ) ] complexes. The
Fig. 3. Plot of HOMO and LUMO of 2-acetyl thiophene thiosemicarbazone.

M. Tyagi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 1–8
7
Fig. 5. Graph showing the inhibition percentage of synthesized compounds against fungus species.
gree of inhibition; as the concentration increases (Fig. 6) the activ-
ity increases (Table 6).
The activity order for R. bataticola was found to be
Chlorothalonil > [Cu(L)
Mn(L) (NO ] > Ligand
With M. phaseolina the order of activity was
Cu(L) Cl ] > [Cu(L) (NO
Chlorothalonil > [Mn(L) (NO
The order of activity with F. odum was found to be:
Chlorothalonil > [Cu(L) (NO ] > [Cu(L) Cl
[Mn(L) Cl ] > [Mn(L) (NO ] > Ligand.
2 2 2 3 2 2 2
Cl ] > [Cu(L) (NO ) ] > [Mn(L) Cl ] > [-
2
3 2
)
[
2
2
2
3 2
) ]
>
>
2
3 2 2 2
) ] > [Mn(L) Cl ] > Ligand
2
3
)
2
2
2
]
2
2
2
3 2
)
Conclusion
The thiosemicarbazide based Schiff’s base has been synthesized
and its coordination behaviour with Mn(II) and Cu(II) metal ions
has also been studied. On the basis of spectral studies Mn(II) com-
plexes were found to have an octahedral geometry whereas the
Cu(II) complexes have tetragonal geometry. The thermal studies
suggested that the complexes are more stable as compared to li-
gand. Molecular modelling calculations results hold a good com-
parison between the theoretically predicted geometries and the
experimental ones, which is clearly validating our methodology.
Although these calculations pertain to the gas phase, and the
experimental data are for the solid state, in which crystal field ef-
fect may affect the relative energies and geometries. In the biolog-
ical environment, hydrogen bonding with the solvent is also
expected to affect the relative energies and geometries, but the
good correspondence between our calculations and experimental
data suggest that crystal packing and hydrogen bonding effects
are negligible. The fungicidal screening of the compounds led to
the conclusion that metal complexes are more active as compared
to free ligand.
2
Fig. 6. Comparison of the growth of [Cu(L)Cl ] complex against fungus Rhizoctonia
bataticola (a) at 750 ppm, (b) 500 ppm, and (c) control plate.
charge on central metal ion after complexation reduces to 1.104e,
0
.716e and 0.967e respectively.
A noteworthy point is the similarity in trend of charge transfer
in Mn(II) and Cu(II) complexes, as chloride ions acts as a better
electron donor than nitrate ion. There is a transfer of 0.862e from
chloride ion in [Mn(L)
chloride ion in Cu(L) Cl
in case of nitrate ion there is a transfer of only 0.575e and 0.623e in
Mn(L) (NO ] complex and [Cu(L) (NO ] respectively.
We also calculated the energies for Highest occupied molecular
2
Cl
2
] complex and 0.911e are donated by
2
2
complex during complex formation, while
[
2
3
)
2
2
3 2
)
orbital (HOMO) and Lowest occupied molecular orbital (LUMO).
The calculated energies of the HOMO and LUMO for ligand are
ꢁ
0.183 hartree and ꢁ0.081 hartree, respectively. The HOMO of
the ligand is concentrated on S atom, while LUMO is concentrated
on S and C atoms. The 0.020 hartree isovalue contours for the
1
1
1
HOMO and LUMO are displayed in Fig. 3.
On the basis of above discussion following (Fig. 4) can be pro-
posed for the synthesized complexes (see Fig. 4).
Acknowledgements
We thank the Principal, Zakir Husain Delhi College for providing
lab facilities, IIT Bombay for recording EPR spectra, IIT delhi for
recording NMR spectra. Authors are thankful to UGC, New Delhi
for financial assistance.
Antimicrobial studies
The antimicrobial screening data show that the compounds ex-
hibit antimicrobial properties and it is important to note that the
metal chelates exhibit more inhibitory effects than the parent li-
gands (Fig. 5). The increased activity of metal complexes can be ex-
plained on the basis of chelation theory [32]. It has also been
proposed that concentration plays a vital role in increasing the de-
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2013.07.074.

8
M. Tyagi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 1–8
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
References
Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery, Jr., J.E. Peralta, F. Ogliaro,
M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M.
Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth,
P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman,
J.V. Ortiz, J. Cioslowski, D.J. Fox, Gaussian, Inc., Wallingford CT, 2009.
17] A.E. Liberta, D.X. West, Biometals 5 (1991) 121.
[
[
1] C.R. Choudhary, S.K. Mondal, S. Mitra, S.D.G. Mahali, K.M.A. Malik, J. Chem.
Crystallogr. 31 (2002) 57.
2] F.R. Pavan, P.I. da, S. Maia, S.R.A. Leite, V.M. Deflon, A.A. Batista, D.N. Sato, S.G.
Franzblau, C.Q.F. Leite, Eur. J. Med. Chem. 45 (2010) 1898.
3] S. Tardito, L. Marchiò, Curr. Med. Chem. 16 (2009) 1325.
4] M.B. Ferrari, F. Bisceglie, A. Buschini, S. Franzoni, G. Pelosi, S. Pinelli, P.
Tarasconi, M. Tavone, J. Inorg. Biochem. 104 (2010) 199.
5] M.A. Neelakantan, M. Esakkiammal, S.S. Mariappan, J. Dharmaraja, T. Indian, J.
Pharm. Sci. 72 (2010) 216.
[
[
[
[
[
[
[
18] M. Tyagi, S. Chandra, OJIC 2 (2012) 41.
19] S. Chandra, S. Raizada, M. Tyagi, P. Sharma, Spectrochim. Acta A 69 (2008) 816.
20] K.P. Deepa, K.K. Aravindakshan, Synth. React. Inorg. Met. Org. Chem. 30 (2000)
[
[
[
6] T.S. Lobana, R. Sharma, G. Bawa, S. Khanna, Coord. Chem. Rev. 253 (2009) 977.
7] A.G. Quiroga, C.N. Ranninger, Coord. Chem. Rev. 248 (2004) 119.
8] A. Corona-Bustamante, J.M. Viveros-Paredes, A. Flores-Parra, et al., Molecules
1601.
[
[
[
[
[
[
[
21] N.S. Youssef, K.H. Hegab, Synth. React. Inorg. Met.-Org.Chem. 35 (2005) 391.
22] S. Chandra, M. Tyagi, J. Serb. Chem. Soc. 73 (2008) 727.
23] S. Chandra, L.K. Gupta, S. Agrawal, Trans. Met. Chem. 32 (2007) 240.
24] S. Chandra, A.K. Sharma, Spectrochim. Acta A 74 (2009) 271.
25] U. Kumar, S. Chandra, E – J. Chem. 7 (2010) 1238.
1
5 (2010) 5445.
[
9] N. Raja, R. Ramesh, Spectrochim. Acta A 75 (2010) 713.
[
[
10] S.A. Patil, V.H. Naik, A.D. Kulkarni, P.S. Badami, Spectrochim. Acta A 75 (2010)
47.
11] M. Joseph, A. Sreekanth, V. Suni, M.R.P. Kurup, Spectrochim. Acta A 64 (2006)
37.
3
26] M. Tyagi, S. Chandra, J. Indian Chem. Soc. 89 (2012) 147.
27] A.B.P. Lever, Crystal field spectra, in: Inorganic Electronic Spectroscopy, first
ed., Elsevier, Amsterdam, 1968.
6
[
[
[
[
[
12] G. Ibrahim, G. Bouet, I.H. Hall, M.A. Khan, J. Inorg. Biochem. 81 (2000) 29.
13] M A.D. Becke, Phys. Rev. A 38 (1988) 3098.
[
[
[
[
[
28] S. Chandra, U. Kumar, Spectrochim. Acta A 61 (2005) 219.
29] B.J. Hathaway, D.E. Billing, Coord. Chem. Rev. 5 (1970) 143.
30] S. Chandra, M. Tyagi, M.S. Refat, J. Serb. Chem. Soc. 74 (2009) 907.
31] M.S. Refat, S. Chandra, M. Tyagi, J. Therm. Anal. Calorim. 100 (2010) 261.
32] S. Chandra, A. Kumar, Spectrochim. Acta A 68 (2007) 1410.
14] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
15] S.H. Vosko, L. Wilk, M. Nusair, Can. J. Chem. 58 (1980) 1200.
16] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato,
X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M.