Thermal degradation studies on some metal hydrazinic complexes

Article abstract of DOI:10.1007/s10973-008-9102-3

The paper deals with the characterization of three hydrazinic complexes with Ni, Cu and Cr respectively, by means of non-isothermal thermal methods, TG, DTG and DTA, under nitrogen atmosphere in order to investigate the structure-thermostability-thermal d

Full text of DOI:10.1007/s10973-008-9102-3

Journal of Thermal Analysis and Calorimetry, Vol. 94 (2008) 2, 329–334
THERMAL DEGRADATION STUDIES ON SOME METAL HYDRAZINIC
COMPLEXES
1
Lucia Odochian , Anca Mihaela Mocanu , C. Moldoveanu , Gabriela Carja and C. Oniscu
*
2
1
2
2
1
‘Al. I. Cuza’ University, Faculty of Chemistry, 11 Carol I Bd, Iassy, Romania
2
‘Gh. Asachi’ University, Faculty of Chemical Engineering, 71A D. Mangeron Bd, Iassy, Romania
The paper deals with the characterization of three hydrazinic complexes with Ni, Cu and Cr respectively, by means of non-isother-
mal thermal methods, TG, DTG and DTA, under nitrogen atmosphere in order to investigate the structure–thermostability–thermal
degradation mechanism correlation. The thermal analysis made evident the degradation mechanisms characteristic of every sample
in accordance with the chemical structure. The quantitative analysis by TG-DTG afforded the estimation of the metal amount in the
complex on the basis of the resulting metallic oxide nature as well as of some aspects of the thermal degradation mechanism sup-
ported by mass spectral measurements. The melting points given by DTA and confirmed by the Boetius method and the initial tem-
peratures of thermal degradation from TG-DTG-DTA afforded to ascertain the temperature range proper for using and storing the
complexes under study which show potential practical applications as drugs.
Keywords: DTA, DTG, hydrazinic complexes with Ni, Cu, Cr, mass spectrometry, TG
Introduction
previously synthesized [8, 9] in order to follow the
structure–thermostability–thermal degradation
mechanism correlation [14–16].
The studies on the biologically active products have
much been extended in recent years [1, 2]. Among the
organic compounds with potential practical applications
the hydrazides are particularly important [3, 4]. Signifi-
cant progresses were noticed since the phenoxyacetic
acids synthesized firstly by Baltazzi and Delavegne in
The characterization by thermal methods indi-
cate the temperature range proper for using and stor-
ing the compounds under study, the thermostability
series being correlated with their structure and the na-
ture of the bound metal.
1
955 [5] were taken in therapeutical uses.
The quantitative analysis by TG-DTG [17–20]
under nitrogen atmosphere afforded a discussion on
the thermal degradation mechanism. A similarity be-
tween the degradation mechanisms of the Cu and Cr
complexes in comparison with the Ni complex is no-
ticed which is indicative of the major influence of the
substituents.
The condensation of hydrazides with some transi-
tional metals gives metallic complexes showing effi-
ciency against a lot of diseases. Thus, the drugs contain-
ing copper hydrazinic complexes are indicated for treat-
ing inflammatory processes, ulcer, convulsions, cancer,
diabetes, being also beneficial to bone growing and tis-
sue regeneration. The chrome complexes show growing
stimulating action on the organism, the iron complexes
act as catalysts in some processes in living organism,
protect and maintain the functions of the immunity sys-
tem and the manganese ones activate the destructive
processes of the proteins, regulate the glucose level and
contribute to the formation of bones and tissues [6].
The hydrazinic complexes with transitional me-
tals show a dual action given by both the hydrazine
moiety and the metal in their structure [7].
The conclusions on the thermal degradation
mechanisms drawn by TG-DTG-DTA were con-
firmed and completed by mass spectra under the con-
ditions of chemical ionization.
The melting points estimated from DTA data un-
der nitrogen atmosphere are in very good agreement
with those measured by the Boetius method.
Experimental
Methods
By taking the practical importance of these com-
pounds into account as well as their easiness of metal
releasing the present study is aimed to go on with our
previous researches in the field [8, 9] by performing
the characterization by thermal methods [10–13] of
some new Ni, Cu and Cr complexes starting from the
hydrazides of sulphonamidated phenoxyacetic acids
Thermal analysis
The thermogravimetric (TG) and differential thermal
analysis (DTA) were performed by using a
Perkin-Elmer Pyris Diamond TG/DTA thermo-
*
Author for correspondence: lodochian@yahoo.com
1
388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
©
2008 Akadémiai Kiadó, Budapest

ODOCHIAN et al.
balance which records simultaneously the T, TG and
complexes were separated by using a water–ethanol
mixture (b.p.»78–100°C) as a solvent.
TG and DTG curves of the complexes a, b, c ob-
DTA curves. The DTG curves were obtained by nu-
merical differentiation of the TG curves. The working
conditions were the following: sample mass 12 mg,
tained under N (nitrogen) atmosphere within the
2
–
heating rate 10°C min , temperature range 30–900°C
1
30–900°C temperature range are presented in Figs 1a–c.
The examination of the TG-DTG curves indi-
cates complex degradation mechanisms specific to
the compounds under study [18–21].
–
in nitrogen stream (800 mL min ).
1
Mass spectrometry
The complexes are thermally degraded in one
nd
main stage (the II stage) within the 218–900°C tem-
The mass spectra were recorded on a GCMS
Shimadzu QP2010 mass spectrometer with DI (direct
inlet) and CI (chemical ionization). Reagent gas was
CH4.
perature range, a similarity being noticed between the
samples b and c whose TG and DTG curves show two
distinct inflexion points unlike the sample a showing
a single inflexion point only.
The thermal degradation is preceded by a stage
of solvent removal within the 63–171°C range
Results and discussion
(
stage I) where the evaporation points of the solvents
lie (78, 100°C).
The DTA curves for the thermal degradation of
The structure of the studied complexes, their chemi-
cal formula, IUPAC denominations, molecular
masses and melting points measured by the Boetius
method are presented in Scheme 1.
the complexes a, b and c depicted in Fig. 2 also con-
firm the developing of a complex and specific mecha-
nism with the same stages as resulted from TG-DTG.
Thus, during the endothermic processes proceed-
ing between 60–160°C the solvent mixtures retained in
the samples are eliminated, their evaporation tempera-
tures being situated within this range (78, 100°C).
The synthesis of these complexes and their char-
acterization by elemental analysis and FTIR and
NMR spectral measurements were presented in previ-
ous papers [8, 9]. The mention has to be made that the
Scheme 1 Samples under study (structure, molecular mass and melting points)
330
J. Therm. Anal. Cal., 94, 2008

SOME METAL HYDRAZINIC COMPLEXES
Fig. 2 DTA curves of samples a, b, c
ing to the sample thermal degradation which are also
to be found in TG-DTG.
Table 1 presents characteristic amounts resulting
from TG-DTG-DTA and the colour and residue per-
centage.
The mention has to be made that the percentage
mass loss by thermal degradation was referred to the
complex amount with no solvent included.
The quantitative analysis from TG gives a good
agreement of the theoretical and experimental values for
the resulting residue and the retained metal under the as-
sumption that the metal oxides – NiO, Cu O, CrO
2
– re-
3
sulted by the thermal degradation in N
2
atmosphere
which was also confirmed by the residue colour [23].
The experimental and theoretical values for the
residue and the metal retained in the sample under
study given in Table 2 support the formation of these
complexes.
The initial temperatures of the thermal degradation
resulting from both TG-DTG-DTA (Table 1) are indica-
tive of the following thermostability series: a>c>b.
Since the metal–ligand bond strength obeys the
order: b>c>a [23, 24] it follows that the stronger
metal-ligand bond the lower the stability is [23]. It is
known [25, 26] that the peripheral bonds which can
be influenced by the substituents in their proximity
are thus weakened.
Fig. 1 TG and DTG curves of the a – complex a,
b – complex b, c – complex c
The complexes remaining after the solvent re-
moval show an endothermic process within the
1
80–260°C range where the masses of the samples b
Consequently, the end functional groups are ex-
pected to be the first detached and removed being
then followed by the thermal degradation proceeding
from the external to the internal parts of the complex
molecule.
and c in TG-DTG remain constant corresponding to
the melting peak.
The sample melting points were estimated from
the temperatures corresponding to the DTA-melting
peak maximum [22] excepting for the sample a where
the degradation process is overlapped with the melt-
The fact can also be noticed in Table 1 that with
the complexes b and c the initial degradation temper-
atures as well as those corresponding to the first in-
flection are very close which would suggest the split-
ting of the same bond type. This conclusion is also
confirmed by the presence of the same end functional
ing and the T °C was estimated from the inflexion
i
point temperature of the melting–degradation peak.
The melting points obtained by the DTA and
Boetius methods are in very good agreement
(
Scheme 1).
Within the 260–900°C temperature range the
group, –NH
2
–SO
2
– in the structures of the samples b
N–SO
and c unlike the sample a where the (C
4
H
9
)
2
–
2
DTA curves show endothermic processes correspond-
J. Therm. Anal. Cal., 94, 2008
331

ODOCHIAN et al.
group is the end functional group and the initial deg-
Thus, the fact is noticed that with the complexes b
and c the mass loss (%) corresponding to the first
inflexion point at Tinf corresponds to the elimination
radation temperature is different from that of the sam-
ples b and c.
The mass losses corresponding to the inflexion
point in TG (%) as well as the residue content (%) in
correlation with the complex structures afford a dis-
cussion on their thermal degradation mechanism.
of 2NH followed by the elimination of 2SO between
2 2
¢
T –Tinf
.
inf
With the complex a, the mass loss (%) till Tinf
corresponds to the elimination of 2SO2 in the
N–SO – end functional group which is differ-
(
C
4
H
9
)
2
2
Table 1 Characteristic amounts from TG-DTG-DTA curves
ent from that of the complexes b and c.
The results are given in Table 3.
Sample
Thermal
Stage
These findings from TG-DTG are confirmed by
the mass spectra obtained under the conditions of
method
a
b
c
T
T
T
i
/°C
/°C
/°C
78.70
90.50
63.40
chemical ionization with CH
The mass spectra of the three complexes indicate
the occurrence of fragments of the mass value 64 cor-
responding to the SO group, detached probably by
4
as ionization gas.
m
109.44 139.49 78.72
121.00 171.50 90.20
Stage I
f
2
W
¥
/%
3.44
4.08
1.36
the splitting of the S–N and S–C end bonds. Thus, in
the spectra of the complexes a, b, c this fragment oc-
curs corresponding to the intensities: 3.5% a, 5.73% b
and 1.74% c.
T
i
/°C
258.00 218.00 241.00
¢
T /°C
inf
-
-
255.50
4.66
258
¢
W
in/%
5.28
¥
Since the mass spectra were recorded within the
m/z domain situated between 40–800 the fragment
TG-
T
inf/°C 280.30 294.06 311.04
DTG
Stage II
¢
¥
W
in/% 11.56
19.38
17.00
m/z=16 corresponding to the NH group resulting
2
¢
T /°C
m
289.92 318.56 330.24
probably from the complexes b and c by the N–S
bond splitting could not be made evident. However,
this breaking up is made evident by the signal m/z=64
previously mentioned as well as by the absence of the
T
f
/°C
900
900
900
W
¥
/%
73.34
10.00
57.16
22.44
42.84
17.68
%
signal at m/z=80 corresponding to the NH –SO
2 2
Residue nature
colour
NiO
Cu
2
O
CrO
3
group which would has been released by the splitting
of the S–C bond only with no involvement of the N–S
bond. The fact that the N–S bond is firstly broken is
better revealed with the complex a whose spectrum
shows both the fragment m/z=64 of the 3.5% intensity
green
red
green
T
t
/°C
/°C
257.50 219.90 201.40
257.50 224.00 225.00
DTA
T
i
T
t
– melting point, T
i
– initial degradation temperature,
¢
inf
corresponding to the SO
m/z=128 of the 20.41% intensity corresponding to the
–N(C group.
The advanced degradation mechanism proceed-
ing from the external to the internal pact of the mole-
2
group and the fragment
T
, Tinf – temperatures corresponding to the inflexion
points, T
m
– temperature corresponding to the
– final degradation
– mass losses at the
inflexion point temperatures and the subsequent mass
loss, respectively
maximum degradation rate, T
f
H )
4 9 2
¢
inf
temperature,W , Winf and W
¥
Table 2 Experimental and theoretical values for the residue and metal content
Experimental
residue/%
Theoretical
residue/%
Retained metal
experimental/g
Retained metal
theoretical/g
Sample
Residue nature
NiO
–4
–4
a
b
c
10.00
22.44
17.68
9.00
21.29
17.606
11.6·10
2.29·10
1.087·10
8.204·10
–
3
–3
Cu
2
O
2.17·10
–
3
–3
CrO
3
1.082·10
Table 3 Experimental and theoretical mass losses (%) for 2NH
NH
2
and 2SO
2
in complexes under study
SO
2
2
Molecular
mass
Sample
¢
W /
inf
W
theoretical/%
Temperature
range/°C
W
inf
/
W
theoretical/%
Temperature
range/°C
%
(2NH
2
)
%
2
(2SO )
a
b
c
840.00
671.53
567.99
–
–
–
16.66
15.74
19.88
15.24
19.04
22.53
258–280.3
255.5–294.06
258–311.04
4.66
5.28
4.76
5.63
218–255.5
241–258
332
J. Therm. Anal. Cal., 94, 2008

SOME METAL HYDRAZINIC COMPLEXES
Scheme 2 Thermal degradation mechanism of the complexes
Conclusions
The examination of the TG-DTG-DTA curves of the
complexes under study indicates complex and spe-
cific degradation mechanisms which confirm the
structure influence. The complex thermostabilities es-
timated by means of the initial degradation tempera-
tures respect the following order: a>c>b. The
thermostability is correlated with the chemical struc-
ture and the metal ligand bond nature affording the
temperature range proper for using and storing these
complexes to be ascertained.
The theoretical and experimental values of the
amounts of resulting residue and bound metal are in
very good agreement which confirms the formation of
the complexes.
Fig. 3 Mass-spectrum of the complex c
cule is also supported by the high or very high signals
corresponding to some groups including the metallic
ion and the chelatic ring in the three complexes.
Thus, the following main signals are to be found
in the spectra of the three complexes along with other
The thermal analysis and the mass spectral mea-
surements afforded the most probable degradation
mechanism to be advanced, namely the degradation
development from the external to the internal part of
the complex molecule.
fragments
discussed
above:
m/z=242
(I=
3
3.93) – complex a; m/z=314 (I=100%) – complex b;
m/z=300 (I=100%) – complex c. Figure 3 presents as
an example the mass spectrum of complex c.
The most probable thermal degradation mecha-
nism of the three complexes advanced on the basis of
thermal analysis data correlated to the mass spectral
measurements is depicted in Scheme 2.
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DOI: 10.1007/s10973-008-9102-3
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