Nickel(II) complexes of biologically active glutathione: Spectroscopic, kinetics of thermal decomposition and XRPD studies

Article abstract of DOI:10.1016/j.saa.2006.08.024

Nickel(II) complexes of reduced glutathione (GSH) of general composition Na[Ni(L)(X)]H₂O, where H₂L = GSH; X = NO₃^-, SCN^-, CH₃CO₂^-, Cl^- have been synthesized and characterized by elemental analysis, infrared spectra, electronic spectra, magnetic susceptibility measurements, thermal and X-ray powder diffraction studies. Infrared spectra indicate deprotonation and coordination of cysteinyl sulphur and carboxylate oxygen of glycine residue with nickel ions. It indicates the presence of water molecule in all the complexes which has been supported by TG/DTA. The thermal behavior of complexes shows that water molecule is removed in first step-followed removal of anions and then decomposition of the ligand molecule in subsequent steps. General mechanisms describing the decomposition of the solid complexes are suggested. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. The room temperature magnetic moment values for all the complexes lie in the range of 2.2-2.4 BM, indicating departure from spin only values due to second order Zeeman effect. The electronic spectra indicate planar coordination geometry for all the complexes. Crystal data for Na[Ni(L)(CH₃CO₂^-)]H₂O: tetragonal, space group P4/m, a = 8.2004 A, b = 8.2004 A, c = 16.0226 A, V = 1077.47 A³, Z = 2. Crystal data for Na[Ni(L)(Cl^-)]H₂O: cubic, space group Pm3, a = 16.1055 A, b = 16.1055 A, c = 16.1055 A, V = 4178.38 A³, Z = 6. Crystal data for Na[Ni(L)(NO₃^-)]H₂O: tetragonal, space group P4/m, a = 7.2121 A, b = 7.2121 A, c = 12.0200 A, V = 625.22 A³, Z = 2.

Full text of DOI:10.1016/j.saa.2006.08.024

Spectrochimica Acta Part A 67 (2007) 719–729
Nickel(II) complexes of biologically active glutathione: Spectroscopic,
kinetics of thermal decomposition and XRPD studies
Bibhesh K. Singh, Parashuram Mishra, Bhagwan S. Garg∗
Department of Chemistry, University of Delhi, Delhi 110007, India
Received 23 May 2006; accepted 16 August 2006
Abstract
Nickel(II) complexes of reduced glutathione (GSH) of general composition Na[Ni(L)(X)]H2O, where H2L = GSH; X = NO3−, SCN−, CH3CO2
−
,
Cl− have been synthesized and characterized by elemental analysis, infrared spectra, electronic spectra, magnetic susceptibility measurements, ther-
mal and X-ray powder diffraction studies. Infrared spectra indicate deprotonation and coordination of cysteinyl sulphur and carboxylate oxygen of
glycine residue with nickel ions. It indicates the presence of water molecule in all the complexes which has been supported by TG/DTA. The thermal
behavior of complexes shows that water molecule is removed in first step-followed removal of anions and then decomposition of the ligand molecule
in subsequent steps. General mechanisms describing the decomposition of the solid complexes are suggested. Kinetic and thermodynamic param-
eters were computed from the thermal decomposition data. The room temperature magnetic moment values for all the complexes lie in the range of
2.2–2.4 BM, indicating departure from spin only values due to second order Zeeman effect. The electronic spectra indicate planar coordination geom-
−
˚
˚
˚
etry for all the complexes. Crystal data for Na[Ni(L)(CH3CO2 )]H2O: tetragonal, space group P4/m, a = 8.2004 A, b = 8.2004 A, c = 16.0226 A,
3
−
3
˚
˚
˚
˚
˚
V = 1077.47 A , Z = 2. Crystal data for Na[Ni(L)(Cl )]H2O: cubic, space group Pm3, a = 16.1055 A, b = 16.1055 A, c = 16.1055 A, V = 4178.38 A ,
Z = 6. Crystal data for Na[Ni(L)(NO3 )]H2O: tetragonal, space group P4/m, a = 7.2121 A, b = 7.2121 A, c = 12.0200 A, V = 625.22 A , Z = 2.
−
3
˚
˚
˚
˚
© 2006 Elsevier B.V. All rights reserved.
Keywords: Glutathione; Nickel(II) complexes; Spectra; Thermal studies; X-ray powder diffraction
1. Introduction
mechanism(s) of nickel carcinogen sis, the issue of intracellular
speciation of Ni(II) ought be considered, to provide a quanti-
tative tool for discrimination between possible and impossible
molecular pathways [3]. The intracellular level of reduced GSH
is an important factor in cellular resistance to Ni(II), which in
turn, depletes cellular GSH stores [8–11].
Glutathione (␥-glu-cys-gly) (Fig. 1) is one of the most abun-
dant small molecules in biosphere. Its main form is the reduced
monomer (GSH) serving to detoxicate xenobiotics and heavy
metals, reduced protein thiols, maintain cellular membranes and
deactivate free radicals [12]. Recently, it is reported to have anti-
cancer activity [13–14] and glutathione enzyme has been used
in antineoplastic chemotherapy treatment [15].
Despite much interest in coordination chemistry of GSH
[16–20], only little work has been done dealing with Ni–GSH
complexation. Because of the presence of potential binding sites
in glutathione, its coordination chemistry is complicated and the
most definitive information has been obtained by using results
from a combination of various techniques. Taking into account
the complexity of the process, spectral characterization and
the kinetic calculations of all thermal decomposition reaction
Nickelcompoundsarehumancarcinogens[1]. Sinceintracel-
lular Ni(II) is responsible for neoplastic transformation, several
divergent concepts in nickel carcinogenesis have been developed
[2–4]. Among these, the oxidative concept proposes that Ni(II)
complexes formed in vivo in the vicinity of DNA catalyze redox
reactions, whose products oxidize DNA. In turn, some of the
products of DNA oxidative damage induce mutations, which
may lead to neoplastic transformation. Such products include
modifiedbases(primarily8-oxoguanine), abasicsites(primarily
depurinated), base adducts of carbon-centered radicals (includ-
ing DNA cross-linked proteins), single and double breaks in
the phospho-sugar backbone of DNA [2–4]. Alternative mech-
anisms also explained, e.g. those of inhibition of DNA repair
enzymes[5]oralterationsofchromatincondensationand/orspe-
cific gene expression [6–7]. However, regardless of the actual
∗
Corresponding author. Tel.: +91 9868359781; fax: +91 2766 6250.
E-mail address: bibheshksingh@yahoo.co.in (B.K. Singh).
1386-1425/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2006.08.024

720
B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
Fig. 1. Structure of glutathione (reduced, GSH).
becomes important tool for the interpretation of structure of
complicated molecules. Powder X-ray diffraction has routinely
been used as a non-destructive fingerprinting technique in labo-
ratory and industry for several decades. Powder diffraction data
is especially useful to deduce accurate cell parameters. The fact
that the three-dimensional reciprocal lattice information is con-
densed onto a one-dimensional intensity profile with respect
to 2θ in powder diffraction is the main concern. This leads to
overlapping of the diffraction peaks, considerable and preferred
orientation among the crystallites.
Therefore, we report herein the synthesis, spectral charac-
terization, magnetic susceptibility measurements, thermal stud-
ies and X-ray powder diffraction studies of glutathione with
nickel(II) ions.
2. Experimental
Nickel(II) salts and glutathione were procured from Aldrich
and were used as received. Solvents used were of analytical
grade and were purified by standard methods.
2.1. Preparation of complexes
Glutathione (0.001 M) and sodium hydroxide (0.001 M)
were dissolved in water (10 ml) added dropwise in solution of
nickel(II) salts (0.001 M) in water (5 ml). There is immediate
formation of dark red colour which gradually changes to dark
brown solid complexes, these were separated out, which were
filtered, washed with water and ethanol and dried over P4O10 in
vaccuo.
2.2. Analysis and physical measurements
The stoichiometric analyses (C, H, N, S) were performed
using Elementar vario EL III (Germany) model. Metal contents
were estimated on a AA-640-13 Shimadzu flame atomic absorp-
tion spectrophotometer in solution prepared by decomposing
the complex in hot concentrated HNO3. Infrared spectra were
recorded on Perkin-Elmer FT-IR spectrophotometer in KBr and
polyethylene pellets. The electronic spectra 900–200 nm of the
complexes in solid state was recorded on Jasco-Unidec-430B
double beam spectrophotometer. Magnetic susceptibility mea-
surements at room temperature were carried out in powdered
state on a vibrating sample magnetometer PAR 155 with 5000G-
field strength, using Co[Hg(SCN)4] (magnetic susceptibility
was assumed to be 1.644 × 10−5 cm3 g−1) as calibrant. Rigaku
model 8150 thermoanalyser (Thermaflex) was used for simulta-
neousrecordingofTG–DTAcurvesataheatingrateof5◦ min−1
For TG, the instrument was calibrated using calcium oxalate
.

B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
721
Fig. 2. IR spectrum of: (a) ligand (GSH); (b) Na[Ni(L)(CH3CO2−)]H2O; (c) Na[Ni(L)(Cl−)]H2O; (d) Na[Ni(L)(NO3−)]H2O; (e) Na[Ni(L)(SCN−)]H2O.
while for DTA, calibration was done using indium metal, both
of which were supplied along with the instrument in ambient
condition. A flat bed type Al-crucible was used with ␣-alumina
(99% pure) as the reference material for DTA. The number of
decomposition steps was identified using TG. The activation
energy (E) and Arrhenius constant of the degradation process
was obtained by Coats and Redfern method. The XRD pow-
der pattern were recorded on a vertical type Philips 1130/00
X-ray diffractometer, operated at 40 kV and 50 Ma generator
˚
using the Cu K␣ line at 1.54056 A as the radiation sources. Each
sample were scanned between 10◦ and 70◦ (2θ) at 25 ◦C. The
crystallographic data were analyzed by using the CRYSFIRE

722
B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
powder indexing software package and the space group was
found by GSAS program, density determined by Archimedes
method.
3. Results and discussion
GSH reacts with Ni(II) salts in basic medium with the forma-
tion of complexes with composition Na[Ni(L)(X)]H2O (Table 1)
where X = CH3CO2−, Cl−, NO3−, SCN− and H2L = GSH.
Complexes were crystalline in nature, insoluble in common
organic solvents.
3.1. Infrared spectra and mode of bonding
Glutathione(GSH)isaligand, whichpossessesthethiolfunc-
tion, –COO−, NH2 coordination groups and various forms of
GSH deprotonation. The infrared spectral data of the ligand and
metal complexes are given in Table 2 and are shown in Fig. 2a–e.
The results indicate that the glutathione shows a strong band
at 2525(s) cm−1 due to ν(SH), which is absent in the spectra of
the complexes indicating the deprotonation and coordination of
the thiol group [21]. This has been confirmed by the appearance
of ν(Ni–S) band at 340–320 cm−1 in all the complexes suggest-
ing the binding of metal through sulphur [22]. In glutathione the
band at 1713 cm−1 is assigned to the C O stretching vibration
of the –COOH group of glycine residue, is disappeared, indicat-
ing the binding of –COOH group of glycine with metal ions in all
the complexes [23]. The band at 1665(m) cm−1 in the ligand is
assigned to the C O stretching of the peptide bonds. This band
has been shifted to lower frequency, indicating the coordination
of the C O group with nickel(II) ion [24]. The doublet peaks,
appearing at 3347(s) cm−1 and 3252(s) cm−1 due to symmet-
ric stretching vibrations of the peptide group [24] merged into
a single band in all complexes in the region 3400–3200 cm−1
.
The peak appearing at 3026(s) cm−1 in the free ligand is due to
+
the N–H stretching in a hydrogen bonded NH3 in zwitter ion
−OOC–C–NH3+ of the amino acid moiety [25]. This band does
not show any considerable shift, indicating the non-participation
in complex formation. A broad diffused band 3400–3500 cm−1
may be assigned to ν(OH) for lattice H2O in complexes [26].
This band is absent in the ligand.
The C O and C–O stretching frequency at 1537(m) cm−1
and 1396(s) cm−1 in glutathione are assigned to νas(CO2) and
νs(CO2) modes of the carboxylate group and these bands shows
considerable shift in all the complexes [27,28].
In addition to the ligand bands modified slightly on account of
coordination, infrared spectra of the nickel nitrate complex with
glutathione show absorption bands at ca. 1276, 1104, 771, 1385,
950, 1035 cm−1 due to coordinated nitrato groups. These bands
are assigned as ν1, ν2, ν3, ν4, ν5, ν6 modes, respectively, and
their frequencies are consistent with those associated with ter-
minally bonded monodentate nitrato groups [29,30]. In addition
to these, two weak bands with a separation of ca. 12 cm−1 appear
in the 1800–1700 cm−1 region indicating clearly the exclusive
presence of terminal monodentate nitrato groups [31,32].
In acetato complex, band at 1618 and 1395 cm−1 can be
assignedtoνas(CO2)andνs(CO2)fundamentalstretchingbands,

B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
723
irreduciblerepresentationofd–dtransition, i.e., dxz,yz → dx2−y2
and S␲x → Ni is charge transfer band from π sulphur orbital to
Ni(II).
3.3. Thermo analytical studies
The correlations between the different decomposition
steps of the ligand/complexes with the corresponding weight
losses are discussed in terms of the proposed formula of the
ligand/complexes.
The ligand glutathione (GSH) (Fig. 4a) with the general
formula (C10H17N3O6S) is thermally decomposed in two suc-
cessive steps. The first decomposition step of estimated mass
loss 34.90% (calculated mass loss = 35.00%) within the tem-
perature range 465–505 K may be attributed to the liberation
of 2CO2 + NH3. The DTA curve gives endothermic peak at
488 K (maximum peak temperature). The second step occurs
within the temperature range 650–810 K with the estimated
mass loss 50.10% (calculated mass loss = 50.51%) are reason-
ably accounted for the decomposition of the rest of the molecule.
The DTA curve gives broad diffused exothermic peak at 729 K
(maximum peak temperature). The ligand is completely decom-
posed at temperature 825 K.
Fig. 3. Electronic spectra of complexes. (a) Na[Ni(L)(CH3CO2−)]H2O
(—); (b) Na[Ni(L)(Cl−)]H2O (ꢀ); (c) Na[Ni(L)(NO3−)]H2O (᭹); (d)
Na[Ni(L)(SCN−)]H2O (ꢁ).
respectively, whichareinagreementwiththeacetategroupbeing
monodentate [22,27] because the difference is 223 cm−1. The
band at 1395 cm−1 is due to νas(CO2) mode of both acetate
and ligand. In chloro complex, ν(M–Cl) band is observed at
388 cm−1, which showed terminal rather than bridging chlorine
[33].
The Na[Ni(L)(CH3CO2−)]H2O complex (Fig. 4b) with
the general formula Na[Ni(C12H18N3O8S)]H2O was thermally
decomposed in three successive decomposition steps. The first
decomposition step of estimated mass loss 4.00% (calculated
mass loss = 3.87%) is due to the elimination of one water
molecule in the temperature range 327–383 K. This dehydration
range indicates the presence of non-coordinated water molecule
in the complex. Infrared studies and the endothermic peak at
369 K (maximum peak temperature) by DTA curve also confirm
this fact. The second step occurs within the temperature range
553–588 K with the estimated mass loss 16.25% (calculated
mass loss 16.60%) may be attributed to the loss of acetate (as
CH4 and CO2 gases) and NH3 molecule of the ligand. The DTA
curve gives endothermic peak at 574 K (maximum peak temper-
ature). The third step of decomposition occurs within the tem-
perature range 723–833 K with an estimated mass loss 53.05%
(calculated mass loss = 52.92%) which corresponds to the loss
of C9H11NO5S molecule of the ligand leaving NiO + NaCN
residue with a total estimated mass loss 73.30% (total calculated
mass loss = 73.39%). The end product (residue) was confirmed
by comparing observed and calculated mass of pyrolysis prod-
uct. The DTA curve shows exothermic peak at 797 K (maximum
peak temperature).
In the complex with NCS− group, it seems to be that
NCS− coordinated through the nitrogen atom since ν(C N),
ν(C–S) and δ(NCS) are observed, respectively, in regions
of 2090–2060 cm−1, 830–810 cm−1, 490–470 cm−1, respec-
tively [34]. In this case Ni–N stretching vibration observed at
272 cm−1
.
3.2. Magnetic susceptibility and electronic spectra
As further structural tools, magnetic and solid reflectance
spectral studies have been used to confirm the geometry of the
complexes. The magnetic susceptibility measurements were car-
ried out in the solid state at 25 ◦C. The results are presented
in Table 1. Magnetic moments for the nickel(II) complexes
lies in the range 2.2–2.4 BM, is lower than that octahedral,
tetrahedral or high spin five coordinate complex, suggesting
square planar geometry. The reason for the departure from
the spin only value lies partly in the existence of the second
order Zeeman effect between the ground and the higher lig-
and field terms [35]. However, it lies mainly in the fact, that
in the presence of spin–orbit coupling, the quenching effect
of the ligand field cannot be complete. The electronic spec-
tra of the complexes are listed in Table 1. The spectrum of
the complexes (Fig. 3a–d) shows, absorption bands in the vis-
ible region 650–635 nm and 590–570 nm may be assigned to
The Na[Ni(L)(Cl−)]H2O complex (Fig. 4c) with the general
formula, Na[Ni(C10H15N3O6SCl)]H2O was thermally decom-
posed in three successive steps. The thermogravimetric decom-
position pattern indicates the loss of lattice water also seen as
in endothermic peak in the DTA in the 330–390 K ranges. This
factor is further confirmed by infrared studies. The first esti-
mated loss is 3.80% (calculated mass loss = 4.10%). The second
step occurs within the temperature range 550–613 K with an
estimated mass loss of 22.00% (calculated mass loss = 22.08%)
which corresponds to the loss of HCl + NH3 + CO2 molecule.
The DTA curve gives endothermic peak at 574 K (maximum
1
1
1
1
the A1g → A2g and A1g → B1g transitions, respectively,
which are consistent with a square planar stereochemistry with
the nickel(II) ions [36,37]. The band at region 410–408 nm,
365–360 nm are due to charge transfer spectra from the tran-
sition E + S␲x → Ni and S␲x → Ni, respectively, where E is

724
B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
Fig. 4. TG/DTA curves of: (a) ligand (GSH); (b) Na[Ni(L)(CH3CO2−)]H2O; (c) Na[Ni(L)(Cl−)]H2O; (d) Na[Ni(L)(NO3−)]H2O; (e) Na[Ni(L)(SCN−)]H2O.

B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
725
peak temperature). The third step involves the decomposition of
the remaining ligand C8H11NO3S with an estimated mass loss
49.32% (calculated mass loss = 49.00%) in the 773–870 K range
within the possibility of formation of nickel oxide and sodium
cyanideasendproduct. Theendproduct(residue)wasconfirmed
by comparing observed and calculated mass of pyrolysis prod-
uct. The DTA curve gives exothermic peak at 821 K (maximum
peak temperature).
ature range 470–511 K with an estimated mass loss 21.45%
(calculated mass loss = 20.90%) which is reasonably accounted
for the loss of CH4 + SO2 + NH3 molecule. The DTA curve gives
endothermic peak at 495 K (maximum peak temperature). The
third step occurs within the temperature range 525–836 K with
an estimated mass loss 49.23% (calculated mass loss = 48.26%),
which is reasonably accounted for the loss of rest of the lig-
and molecule (C9H8N2O3S), leaving NiO + NaCN as residue
with total estimated mass loss 74.48% (total calculated mass
loss = 73.04%). The end product (residue) was confirmed by
comparing observed and calculated mass of pyrolysis product.
The DTA curve gives exothermic peak at 790 K (maximum peak
temperature).
The Na[Ni(L)(NO3−)]H2O complex (Fig. 4d) with the
general formula, Na[Ni(C10H15N4O9S)]H2O was thermally
decomposed again in three stages. The first estimated mass
loss of 16.98% (calculated mass loss = 17.09%) within the
temperature range 330–400 K could be attributed to the
liberation of nitrate group as (NO2 + (1/2)O2) gases along
with H2O molecule. The DTA curve gives endothermic
Accordingly, to these conclusions, the decomposition mech-
anisms proposed for glutathione and these complexes are sum-
marized as follows
1. C10H17N3O6S4−8→8 K2CO2 + NH3 + C8H14N2O2S,C8H14N2O2S7−2→9 KC3H8 + 5C + 2NH3 + SO2
2. Na[Ni(C12H18N3O8S)]H2O3−6→9 KH2O + Na[Ni(C12H18N3O8S)],
Na[Ni(C12H18N3O8S)]5−7→4 KCH4 + CO2 + NH3 + C10H11N2O6SNaNi,
C10H11N2O6SNaNi7−9→7 KC9H11NO5S + NiO + NaCN
3. Na[Ni(C10H15N3O6SCl)]H2O3−7→2 KH2O + Na[Ni(C10H15N3O6SCl)],
Na[Ni(C10H15N3O6SCl)]5−7→4 KHCl + NH3 + CO2 + C9H11N2O4SNaNi,
C9H11N2O4SNaNi8−2→1 KC8H11NO3S + NiO + NaCN
365 K
1
2
4. Na[Ni(C10H15N4O9S)]H2O−→ H2O + NO2 + O2 + Na[Ni(C10H15N3O6S)],
Na[Ni(C10H15N3O6S)]5−7→8 K2CO2 + NH3 + C8H12N2O2SNaNi,
C8H12N2O2SNaNi7−8→8 KC7H12NOS + NiO + NaCN
5. Na[Ni(C11H15N4O6S2)]H2O3−4→8 KH2O + Na[Ni(C11H15N4O6S2)],
Na[Ni(C11H15N4O6S2)]4−6→5 KCH4 + SO2 + NH3 + Na[Ni(C10H8N3O4S)],
Na[Ni(C10H8N3O4S)]7−9→0 KC9H8N2O3S + NiO + NaCN
3.4. Kinetics of thermal decomposition
peak at 365 K (maximum peak temperature). The second
step occurs within the temperature range 523–613 K with an
estimated mass loss 23.22% (calculated mass loss 22.44%),
which is reasonably accounted for the loss of NH3 + 2CO2
molecule. The DTA curve gives endothermic peak at 578 K
(maximum peak temperature). The third step occurs within the
temperature733–853 K, with an estimated mass loss 32.85%
(calculated mass loss = 34.00%) are reasonably accounted for
the decomposition of the remaining part of the ligand molecule
(C9H12NO5S) leaving nickel oxide and sodium cyanide as
residue. The total estimated mass loss 73.05% (total calculated
mass loss = 73.53%). The end product (residue) was confirmed
by comparing observed and calculated mass of pyrolysis prod-
uct. The DTA curve gives exothermic peak at 788 K (maximum
peak temperature).
The two stages of decomposition of the ligand and three-
stage decomposition of the complexes were studied in more
detail. In recent years there has been increasing interest in
determining the rate-dependent parameters of solid-state non-
isothermal decomposition reactions by analysis of TG curves.
Several equations [38–44] have been proposed as means of
analyzing a TG curve and obtaining values for kinetic param-
eters. Many authors [38–42] have discussed the advantage of
this method over the conventional isothermal method. The rate
of a decomposition process can be described as the product
of two separate functions of temperature and conversion [39],
using
dα
The Na[Ni(L)(SCN−)]H2O complex (Fig. 4e) with the
general formula, Na[Ni(C11H15N4O6S2)]H2O was thermally
decomposed in three steps. The first estimated mass loss 3.80%
(calculated mass loss 3.88%) within the temperature range
320–361 K can be attributed to the liberation of water molecule.
The DTA curve gives endothermic peak at 348 K (maximum
peak temperature). The second step occurs within the temper-
= k(T)f(α)
(1)
dt
where α is the fraction decomposed at time t, k(T) is the
temperature-dependent function and f(α) is the conversion func-
tion dependent on the mechanism of decomposition. It has
been established that the temperature-dependent function k(T)
is of the Arrhenius type and can be considered as the rate

726
B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
Fig. 5. Linearization plot of: (a) ligand (GSH); (b) Na[Ni(L)(CH3CO2−)]H2O; (c) Na[Ni(L)(Cl−)]H2O; (d) Na[Ni(L)(NO3−)]H2O; (e) Na[Ni(L)(SCN−)]H2O.
constant k:
where θ is the linear rate dT/dt. On integration and approxima-
tion, this equation can be obtained in the following form
∗
k = A eE /RT
(2)
ꢀ
ꢁ
2.303E∗
RT
AR
θE∗
log g(α) = −
+ log
(4)
where R is the gas constant in (kJ deg−1 mol−1). Substituting
Eq. (2) into Eq. (1), we get
where g(α) is a function of α dependent on the mechanism of
the reaction. The integral on the right hand side is known as
temperature integral and has no closed for solution. So several
dα
dt
A
∗
=
f(α)
(3)
θ eE /RT

B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
727
Table 3
Thermodynamic activation parameters
Serial no.
1
Compound
GSH
Order (n)
E* (J mol−1
)
A (×105 s−1
)
ꢀS* (J K−1 mol−1
)
ꢀH* (J mol−1
)
ꢀG* (kJ mol−1
)
1
31.28
32.86
0.36
0.27
−161.43
−167.25
53.24
431.45
78.99
122.27
2
3
4
5
Na[Ni(L)(CH3CO2−)]H2O
Na[Ni(L)(Cl−)]H2O
1
1
1
1
38.23
52.56
57.34
1.23
1.49
1.27
−148.99
−170.70
−155.08
−144.05
−150.53
−155.63
−142.59
−149.53
−152.47
−140.98
−147.31
−161.46
68.78
70.16
1297.84
55.05
98.05
124.90
34.75
36.32
38.23
2.25
1.59
1.23
29.39
45.62
957.97
53.63
86.43
128.79
Na[Ni(L)(NO3−)]H2O
Na[Ni(L)(SCN−)]H2O
49.15
51.25
58.49
2.64
1.81
1.73
88.22
75.93
1110.58
52.28
119.09
121.41
49.56
50.95
46.32
2.79
2.04
1.54
45.32
68.26
874.86
49.11
72.99
128.43
(Arrhenius constant) was determined from the intercept. From
relevant data, linearization plots have been drawn in Fig. 5a–d
confirms first order kinetics. It has been found that E* values for
complexes > ligand .The calculation of heat of reaction (ꢀH*)
(Table 4) from the DTA curves were done by using relation (6):
techniques have been used for the evaluation of temperature
integral. Most commonly used methods for this purpose are
the differential method of Freeman and Carroll [38], integral
method of Coats and Redfern [40], the approximation method
of Horowitz and Metzger [43]. The kinetic parameters calcu-
lated by the Horowitz–Metzger method revealed no significant
difference with that evaluated by the Coats–Redfern method. So
integral method of Coats–Redfern and using this method various
kinetic parameters calculated is discussed here in detail.
The kinetic analysis parameters such as activation energy
(ꢀE*), enthalpy of activation (ꢀH*), entropy of activation
(ꢀS*), free energy change of decomposition (ꢀG*) were eval-
uated graphically by employing the Coats–Redfern relation
(5):
ꢀH∗ (J mol−1) = ꢀH (muv) × 60 × 10−6M
(6)
where M is the molar mass of the complex and muv = micro unit
volt. The entropy of activation (ꢀS*) and the free energy change
of activation (ꢀG*) were calculated using Eqs. (7) and (8):
ꢀ
ꢂ
ꢃꢁ
Ah
kT
ꢀS∗ (J K−1 mol−1) = 2.303R log
(7)
(8)
ꢀG∗ (J mol−1) = ꢀH∗ − TꢀS∗
ꢀ
ꢁ
ꢀ
ꢁ
log(1 − α)
AR
θE∗(1 − 2RT/E∗)
E∗
log −
= log
−
where k and h are the Boltzman and Plank constant, respec-
tively. The calculated values of E*, A, ꢀS*, ꢀH* and ꢀG*
for the decomposition steps of the ligand and complexes are
given in Table 3. According to the kinetic data obtained from
the TG curves, all the complexes have a negative entropy, which
indicates that the complexes are formed spontaneously. The neg-
ative entropy also indicates a more ordered activated state that
T2
2.303RT
(5)
where α is the mass loss up to the temperature T, R the gas
constant, E* the activation energy in J mol−1, θ the linear heating
*
∼
rate and (1 −2 RT/E ) 1. A plot of left hand side of Eq. (5)
=
against 1/T gives a slope from which E* was calculated and A
Table 4
Crystal data of metal complexes
Empirical formula
Formula weight
Temperature (K)
NaNiC12H20N3O9S
464.05
298
NaNiC10H17N3O7SCl
440.46
298
NaNiC10H17N4O10
467.01
298
S
˚
Wave length (A)
1.54056
Tetragonal
P4/m
1.54056
Cubic
Pm3
1.54056
Tetragonal
P4/m
Crystal system
Space group
˚
˚
˚
˚
˚
˚ ˚
Unit cell dimensions
a = 8.200418 A, b = 8.200418 A,
a = 16.1055 A, b = 16.1055 A,
a = 7.212145 A, b = 7.212145 A,
◦
◦
◦
˚
˚
c = 16.022610 A, α = β = γ = 90
c = 16.1055 A, α = β = γ = 90
c = 12.0200 A, α = β = γ = 90
3
˚
Volume (A )
1077.47
4178.38
625.22
2θ range
12.18–44.91
23.00–58.67
16.00–65.00
Limiting indices
0 ≤ h ≤ 3, 0 ≤ k ≤ 1, 1 ≤ l ≤ 7
3 ≤ h ≤ 10, 1 ≤ k ≤ 6, 3 ≤ l ≤ 10
2 ≤ h ≤ 8, 1 ≤ k ≤ 8, 0 ≤ l ≤ 2
Density (g/cm3)
1.43
1.045
6
2.48
Z
2
2
Rf
0.0000846
0.000016
0.0000696

728
B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
may be possible through the chemisorption of oxygen and other
decomposition products. The negative values of the entropies
of activation are compensated by the values of the enthalpies of
activation, leading to almost the same values for the free energies
of activation [17].
Fig. 7. Proposed structure for Na[Ni(L)(X)]H2O complexes, where
X = CH3CO2−, Cl−, NO3−, SCN− and H2L = GSH.
3.5. X-ray powder diffraction studies
Structure determination by X-ray powder diffraction data
has gone through a recent surge since it has become impor-
tant to get to the structural information of materials, which do
not yield good quality single crystals. The indexing procedures
were performed using (CCP4, UK) CRYSFIRE program [45]
giving tetragonal crystal system for Na[Ni(L)(CH3CO2−)]H2O
(Fig. 6a) having M(9) = 14, F(9) = 7, cubic crystal system for
Na[Ni(L)(Cl−)]H2O (Fig. 6b) having M(6) = 16, F(6) = 6and
tetragonal crystal system for Na[Ni(L)(NO3−)]H2O (Fig. 6c)
having M(6) = 23, F(6) = 9, as the best solutions. Their cell
parameters are shown in Table 4.
Thus on the basis of the above physico-chemical data in con-
junction with consideration of ring strain the proposed square
planar structure of the complexes is shown in Fig. 7.
4. Conclusion
Nickel(II) complexes were found to be monomer and
involved coordination through cystein sulphur and carboxylate
oxygen giving square planar geometry. Infrared spectra indicate
the presence of H2O molecule in the complexes that has been
supported by TG/DTA. Kinetic studies shows the decomposition
follows first order kinetics and proceeds in three-step decom-
position. Magnetic susceptibility measurements and electronic
spectra also support square planar coordination geometry for all
the complexes. The complex crystallizes in the tetragonal/cubic
crystal system.
Acknowledgement
B.K. Singh is thankful to University Grants Commission,
New Delhi, India for financial assistance under research award
scheme.
References
[1] International Agency for Research on Cancer (IARC), Monographs on the
Evaluation of Carcinogenic Risk to Humans, vol. 49, Lyon, 1990, p. 257.
[2] K.S. Kasprzak, G.S. Buzard, in:J. Koropatnick, R. Zalups(Eds.), Molecular
Biology and Toxicology of Metals, Taylor and Francis, London, 2000, p.
477.
[3] W. Bal, H. Kozlowski, K.S. Kasprzak, J. Inorg. Biochem. 79 (2000) 213.
[4] W. Bal, K.S. Kasprzak, Toxicol. Lett. 127 (2002) 55.
[5] A. Hartwig, T. Schwerdtle, Toxicol. Lett. 127 (2002) 47.
[6] E. Denkhaus, K. Salnikow, Crit. Rev. Oncol. Hematol. 42 (2002) 35.
Fig. 6. X-ray diffraction of: (a) Na[Ni(L)(CH3CO2−)]H2O; (b) Na[Ni(L)-
(Cl−)]H2O; (c) Na[Ni(L)(NO3−)]H2O.

B.K. Singh et al. / Spectrochimica Acta Part A 67 (2007) 719–729
729
[7] H. Cangul, L. Broday, K. Salnikow, J. Sutherland, W. Peng, Q. Zhang, V.
Poltaratsky, H. Yee, M.A. Zoroddu, M. Costa, Toxicol. Lett. 127 (2002)
69.
[8] W. Li, Y. Zhao, I.N. Chou, Toxicology 77 (1993) 65.
[9] S. Lynn, F.H. Yew, J.W. Hwang, M.J. Tseng, K.Y. Jan, Carcinogenesis 15
(1994) 2811.
[10] W. Li, Y. Zhao, I.N. Chou, Toxicol. Appl. Pharmacol. 136 (1996) 101.
[11] K. Salnikow, M. Gao, V. Voitkun, X. Huang, M. Costa, Cancer Res. 54
(1994) 6407.
[24] R.M. Silverstein, O.G. Bassler, T.C. Morrill, Spectrophotometic Identifi-
cation of Organic Compounds, Wiley, NewYork, 1974.
[25] H. Shindo, T.L. Brown, J. Am. Chem. Soc. 87 (1965) 1904.
[26] A. Bravo, J.R. Anacona, Trans. Met. Chem. 26 (2001) 20.
[27] G.B. Deacon, R.J. Phillips, Coord. Chem. Rev. 33 (1980) 227.
[28] G.B. Deacon, F. Huber, R.J. Phillips, Inorg. Chim. Acta 104 (1985) 41.
[29] C.C. Addison, D. Sultons, Prog. Inorg. Chem. 8 (1967) 195.
[30] C.C. Addison, N. Logan, S.C. Wallwork, C.D. Garner, Quart. Rev. Chem.
Soc. 25 (1971) 289.
[12] K. Arthur, B. Wojciech, Bioinorg. Chem. Appl. 2 (2004) 293.
[13] K.P. Rice, P.G. Penkth, S. Krishnamurthy, A.C. Sartorelli, Biochem. Phar-
macol. 69 (2005) 1463.
[14] W.H. Ang, I. Khalaida, C.S. Allardycel, L. Juillerat-Jeanneret, P.J. Dyson,
J. Am. Chem. Soc. 127 (2005) 1382.
[15] Z. Kopamski, M. Grabowska, A. Kosiniak-Kamysz, J. Brtrandt, L.
Kolodziejski, W. Opoka, M. Schlegel-Zawadzka, Biofactors 22 (2004) 79.
[16] B.K. Singh, R.K. Sharma, B.S. Garg, Spectochim. Acta A 63 (2006) 97.
[17] B.K. Singh, R.K. Sharma, B.S. Garg, J. Therm. Anal. Calorim. 84 (2006)
593.
[31] A.B.P. Lever, E. Manto Vani, B.S. Ramaswami, Can. J. Chem. 49 (1971)
1957.
[32] M. Choca, J.R. Ferraro, K. Nakamoto, J. Chem. Soc. A (1972) 2297.
[33] P.L. Goggin, R.J. Goodfellow, J. Chem. Soc. A (1966) 1462.
[34] W.J. Barreto, H.D. Santana, F.A.S. Almeida, D.N. Ishikawa, Y. Kawano, J.
Anal. Appl. Pyrol. 70 (2003) 199.
[35] B.N. Figgis, Introduction to Ligand Fields, 1st ed., 1966.
[36] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam,
1968.
[37] K. Nakamoto, S.J. McCarthy, Spectroscopy and structure of Metal Chelate
Compounds, John Wiley and Sons, USA, 1968.
[18] D.N. Kumar, B.K. Singh, B.S. Garg, P.K. Singh, Spectochim. Acta A 59
(2003) 1487.
[19] K. Arthur, S. Wojciech, S. Magdalena, J.B. Malgorzata, B. Wojciech, Chem.
Res. Toxicol. 16 (2003) 855.
[38] E.S. Freeman, B. Carroll, J. Phys. Chem. 62 (1958) 394.
[39] J. Sestak, V. Satava, W. Wendlandt, Thermochim. Acta 7 (1973) 333.
[40] A.W. Coats, J.P. Redfern, Nature 68 (1964) 201.
[20] P.K. Singh, B.S. Garg, D.N. Kumar, B.K. Singh, Ind. J. Chem. A 40 (2001)
1339.
[21] J. Silver, M.Y. Hamed, I.E.G. Morrison, Inorg. Chim. Acta 107 (1985) 169.
[22] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, Wiley, New York, 1978.
[41] T. Ozawa, Bull. Chem. Soc. Jpn. 38 (1965) 1881.
[42] W.W. Wendlandt, Thermal Methods of Analysis, Wiley, New York, 1974.
[43] H.W. Horowitz, G. Metzger, Anal. Chem. 35 (1963) 1464.
[44] J.H. Flynn, A. Wall, Polym. Lett. 4 (1966) 323.
[45] R. Shirley, The CRYSFIRE System for Automatic Powder Indexing: Users
Manual, Lattice Press, 2002.
[23] G. Domazetis, R.J. Megee, B.D. James, J. Organomet. Chem. 173 (1979)
357.