Spectral and thermal studies of new Co(II) and Ni(II) hexaaza and octaaza macrocyclic complexes

Article abstract of DOI:10.1007/s10973-007-8609-3

The macrocyclic complexes of Co(II) and Ni(II) having chloride or thiocyanate ions in the axial position have been synthesized and characterized. These complexes are synthesised by the template condensation of o-phenylenediamine or 2,3-butanedionedihydraz

Full text of DOI:10.1007/s10973-007-8609-3

Journal of Thermal Analysis and Calorimetry, Vol. 91 (2008) 3, 957–962
SPECTRAL AND THERMAL STUDIES OF NEW Co(II) AND Ni(II)
HEXAAZA AND OCTAAZA MACROCYCLIC COMPLEXES
M. Gaber*, A. F. Rehab and D. F. Badr-Eldeen
Chemistry Department, Faculty of Science, Tanta University, Tanta, Egypt
The macrocyclic complexes of Co(II) and Ni(II) having chloride or thiocyanate ions in the axial position have been synthesized and
characterized. These complexes are synthesised by the template condensation of o-phenylenediamine or
2,3-butanedionedihydrazone with the appropriate aldehydes in NH4OH solution in the presence of the metal ions, Co(II) and Ni(II).
The complexes were characterized by spectroscopic methods (IR, UV-Vis and ESR) and magnetic measurements as well as thermal
analysis (TG and DTA). The results obtained are commensurate with the proposed formulae. Spectral studies indicate that these
complexes have an octahedral structure. From conductivity measurements the complexes are non-electrolytes. The kinetic of the
thermal decomposition of the complexes was studied and the thermodynamic parameters are reported.
Keywords: Co(II), Ni(II), macrocyclic complexes, template condensation, thermal analysis
Introduction
Macrocyclic cobalt(II) complex
An alcoholic solution of o-phenylenediamine (0.02 mol)
was degassed by passing purified nitrogen in a
three-necked flask and a degassed ethanolic solution of
Co(II) chloride (0.01 mol) was added slowly with stir-
ring followed by the addition of (0.04 mol) of formalde-
hyde to the mixture. The reaction mixture was warmed
and stirred, then ammonia solution (0.02 mol) was
added dropwise with stirring. The mixture was stirred
for 8 h, cooled and the product was filtered off, washed
with petroleum ether then dried in vacuum over P2O5.
Yield is found to be about 80%.
The development of the field of bioinorganic chemistry
plays an important generating interest in macrocyclic
compounds and their metal complexes. Transition metal
macrocyclic complexes have received much attention as
an active part of metalloenzymes [1] as biomimic model
compounds [2]. In recent years, a great deal of interest
has been directed towards the metal-controlled template
synthesis of macrocyclic species [3–5]. Very few sys-
tems have been reported for the macrocyclic metal com-
plexes showing the correlation btween the thermal sta-
bility and the structures of the macrocyclic metal
complexes [6, 7].
In this paper, we report the synthesis and charac-
terization of new hexaaza- and octaaza-macrocyclic
complexes prepared by template condensation reac-
tions of o-phenylene-diamine or 2,3-butanedione
dihydrazone with formaldehyde and glutaraldehyde
respectively, in the presence of Co(II) and Ni(II) ions.
The complexes were characterized based on elemen-
tal analyses, IR, UV-Vis, ESR, magnetic moments
and molar conductance measurements. The thermal
behaviour of these complexes was studied by TG and
DTA. The kinetics of the thermal decomposition was
studied and the kinetic thermal parameters were cal-
culated.
Attempts to prepare the thiocyanate and per-
chlorate derivatives by the addition of potassium
thiocyanate solution and perchloric acid to the Co(II)
complex were unsuccessful.
Macrocyclic nickel(II) complexes
Hexaaza macrocyclic complex
An ethanolic solution of the o-phenylene diamine
(0.02 mol in 20 mL) was degassed with nitrogen in a
three-necked flask. A degassed solution of Ni(II)
chloride (0.01 mol) in 10 mL ethanol was added
dropwise with stirring. The mixture was stirred, then
(0.02 mol) of formaldehyde was slowly added fol-
lowed by the addition of (0.02 mol) ammonia solu-
tion. The mixture was warmed and stirred for 12 h.
The brown precipitate obtained was filtered off,
washed with petroleum ether and dried in vacuum
over P2O5. Yield was found to be 80%.
Experimental
All chemical used were of chemically pure grade.
2,3-butanedione dihydrazone was prepared according
to the published procedure [8].
*
Author for correspondence: abuelazm@yahoo.com
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2008 Akadémiai Kiadó, Budapest

GABER et al.
Attempts to prepare Cu(II) macrocyclic complex
Kinetic data
was unsuccessful. Also, attempts to prepare the nickel
thiocyanate and perchlorate derivatives were unsuc-
cessful.
All the well-defined stages were selected for the study
of the kinetics of decomposition of the complexes.
The kinetic parameters like the activation energy (E)
and the pre-exponential factor (A) were calculated us-
ing Coats–Redfern equation [9];
Octaaza macrocyclic complex
ln[g(a)/T2]=ln(AR/QE)[1–(2RTc/E)]–E/RT
Firstly, an alcoholic solution of 2,3-butanedione
dihydrazone (0.02 mol in 20 mL) was warmed and a
degassed ethanolic solution of Ni(II)acetate (0.02 mol
in 10 mL) was then added dropwise with stirring fol-
lowed by the addition of glutaraldehyde (0.02 mol).
The mixture was degassed by passing purified
nitrogen in a three-necked flask and stirred for about
12 h; then an aqueous solution of KNCS (0.02 mol)
was slowly added and the mixture was stirred for 6 h.
The formed precipitate was filtered off, washed with
petroleum ether and dried in vacuum over P2O5. Yield
was 55%.
The metal content in the macrocyclic complexes
was determined by digesting an accurately weighed
amount of the solid complex in (1:1) HClO4 until all
the fumes of HClO4 had ceased to evolve, then trans-
ferred into a measuring flask and titrating a known
volume with EDTA. The results were further con-
firmed from the TG data.
where T is the temperature, Q is the heating rate
(10°C min–1), R is the gas constant and Tc is mean
temperature of the original data.
A plot of ln[g(a)/T2] vs. 1/T gave straight lines
whose slopes and intercepts were used to evaluate E and
A, respectively. The goodness of fit was checked by cal-
culating the correlation coefficient. The assignment of
the mechanism of the thermal decomposition is based
on the assumption that the form of g(a) depends on the
reaction mechanism. In the present study, the nine forms
of g(a) suggested by Satava [10 ] were used to enunci-
ate the mechanism of thermal decomposition in each
step. The value of g(a) with highest correlation coeffi-
cient is taken as the mechanism of thermal decomposi-
tion. The entropy of activation (DS), enthalpy of activa-
tion (DH) and the free energy change of activation (DG)
were calculated using the following equations:
DS=2.303Rlog(Ah/kT)
DH=E–RT
Instrumental methods
Microanalysis C, H and N for the complexes were car-
ried out using Heraeus CHN elemental analyzer. The
molar conductance of the solid complexes in DMF
(10–3 M) were also measured using conductance bridge
of the type 523 conductance meter. The IR spectra were
recorded on a Perkin Elmer 1430 spectrometer in a KBr
matrix within the 4000–200 cm–1 region.
DG=H–TDS
where k and h are the Boltzman and Plank constants,
respectively.
Results and discussion
The thermal analysis (TG and DTA) were recorded un-
der N2 flow (20 mL min–1) on Shimadzu TG-50 equip-
ment at heating rate 10°C min–1. The electronic absorp-
tion spectra were recorded by the aid of Shimadzu 240
spectrophotometer. Magnetic susceptibilities were mea-
sured by the Gouy method at room temperature using a
magnetic susceptibility balance (Johnson Matthey Alfa
Product, Mod. MKI). Diamagnetic corrections were cal-
culated from Pascal’s constants. The ESR spectra were
recorded on a JEOL JEX-FE 2XG spectrometer.
All the prepared complexes were subjected to elemental
analysis. The complexes were found to be of low molar
conductance values (14.4, 12 and 13.6 ohm–1 cm2 mol–1
for complexes 1, 2 and 3, respectively) indicating the
coordination nature of Cl– or NCS– ions and confirming
the nonelectrolyte nature of these complexes [11]. The
analytical and spectral data for all complexes are listed
in Tables 1 and 2, respectively.
Table 1 Elemental analysis of new synthetic macrocyclic complexes
Microanalysis results/Calc. (found)
No.
Suggested formula
Colour
C/%
H/%
N/%
M/%
1
2
3
[CoLCl2]·2(H2O)
[NiLCl2]·2(H2O)
[NiL(SCN)2]·(H2O)
dark brown
dark brown
olive green
41.29 (41.57)
41.41 (41.09)
43.11 (43.00)
5.59 (5.78)
5.61 (5.43)
6.83 (6.25)
18.07 (18.46)
18.12 (17.96)
25.15 (25.22)
12.69 (12.35)
12.66 (12.23)
10.54 (10.41)
958
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NEW Co(II) AND Ni(II) HEXAAZA AND OCTAAZA MACROCYCLIC COMPLEXES
Table 2 IR, electronic absorption, ESR spectral data and magnetic moment values of new synthetic macrocyclic complexes
IR spectra/cm–1
ESR spectra
lmax
nm
/
meff/
BM
No
a
OH
NH
CH2
C–Nb
C–N
M–N
g||
g^
geff
1
2
3
3548
3544
3546
3416
3247
3326
1461
1468
–
1240
1263
–
1104
1043
1097
425
448
–
410, 550
430, 580
440, 560
2.608
1.992
2.197
4.30
3.17
3.01
–
–
–
–
–
–
ain ring formation; baromatic
Fig. 1 TG and DTA curves for complexes 1–3
Co(II) complex
(which corresponds to cylindrical shapes). So, the prob-
able mechanism is D3. The kinetic parameters are listed
in Table 4. There is no definite trend observed in the
values of E and DS for the different stages of decompo-
sition. The –ve values of entropy of activation indicate
that the activated complex has a more ordered structure
than the reactants [12, 13].
For the anhydrous Co(II) complex, the value of
E is higher for the third stage of decomposition com-
pared to that of the second stage indicating that the
third stage is more ordered than the second one. This
may be expected due to the decreased steric strain
when the ligand molecule is decomposed. The activa-
The thermal analysis of the Co(II) complex is shown
in Fig. 1. The observed mass loss within the tempera-
ture range 100–150°C associated with an endother-
mic peak at 130°C could be correlated with the re-
moval of the non-coordinated water molecules; hence
the number of water molecules was calculated and
found to be two. The chloride ions were lost within
the temperature range 220–400°C. Above 400°C the
mass loss associated with an exothermic peak at
390°C corresponded to the decomposition of the com-
plex with the formation of Co2O3 from which the
metal content was calculated and found to be in
confirmity with that obtained from elemental analy-
sis. Based on the thermal analysis, the decomposition
of Co(II) complex can be represented as follows:
–15-
–16-
–17-
100–150°C 220–400°C
[CoLCl2 ]×2H2O¾¾¾®[CoLCl2 ]¾¾¾®
>400°C, oxidation
CoL¾¾¾¾®Co2O3
The plot of ln[g(a)/T2 ] functions vs. 1/T was
drawn for Co(II) complex 1 (Fig. 2) as an example; it
was found that the first stage could be best described by
R3 mechanism, where chemical decomposition con-
trols. The second stage showed extremely close maxi-
mum values of correlation coefficients R for all mecha-
nisms (>0.99), so that it was possible to decide which is
controlling (Table 3). The third step showed two close
maximum values for mechanisms D2 and D3. Since the
latter corresponds to diffusion through spherical product
shell, it was thought to be more probable than the former
st
1
–18-
–19-
nd
2
3
rd
1.0
1.5
2.0
2.5
1000/T/K–1
3.0
3.5
4.0
Fig. 2 Coats–Redfern plots for the decomposition steps of
complex 1, Y=lng(a)/T2
J. Therm. Anal. Cal., 91, 2008
959

GABER et al.
Table 3 Correlation coefficients calculated for Co(II) and Ni(II) complexes using nine forms of g(a)
Complex 1
Complex 2
Complex 3
Function Forms of (a)
I
II
III
I
II
III
I
II
III
D1
D2
D3
R2
R3
F1
a2
–0.984 –0.9993 –0.986
–0.9992 –0.987
–0.986 –0.9999 –0.988
–0.727
–0.991
–0.865
–0.969
–0.961
–0.947
–0.998
–0.996
–0.936
–0.978
–0.984
–0.848
–0.681
0.299
0.985
0.815
0.989
0.987
0.989
»–1.0
0.987
0.997
–0.47
0.977
0.974
0.977
0.976
0.976
–0.98
0.967
0.959
0.947
–0.982
–0.981
0.984
–0.993
–0.996
0.996
(1–a)ln(1–a)+a
[1–(1–a)1/3 2
1–(1–a)1/2
1–(1–a)1/3
–ln(1–a)
–ln(1–a)1/2
–ln(1–a)1/3
–ln(1–a)1/4
–
]
–0.986
–0.989
–0.985
–0.982
–0.974
–0.998
–0.993
–0.997
–0.993
–0.999
–0.977
–0.982
–0.984
–0.969
–0.897
0.9785
–0.983
–0.987
–0.974
–0.965
–0.944
–0.995
–0.998
–0.995
–0.947
0.777
A2
A3
A4
0.991
–0.999
–0.962 –0.9998 –0.888 –0.9998 –0.998
0.954
Table 4 Kinetic parameters obtained by the Coats–Redfern equation
No.
Stage
Fun.
E/kJ mol–1
A/s–1
–DS/J K–1 mol–1
DH/kJ mol–1
DG/kJ mol–1
1
I
II
III
I
R3
D3
D3
A4
A3
F1
38.98
24.4
84.9
5.3
3.6´105
1.2´1010
4.8´104
3.2´109
8.3´109
5.6´105
8.1´104
6´106
146.3
53.4
161.4
65.3
61.4
142.6
152
32.7
21.43
78.9
2.07
1.97
33.9
41.3
82.9
9.62
143.3
40.6
179.4
27.6
2
3
II
III
I
7.3
46.5
40.1
44
146.5
93.3
F1
II
III
F1
87.54
15.2
120
150.3
63.54
R3
8.8´108
80.4
(Fun.): F1 – random nucleation; D3 – three-dimensional diffusion, spherical symmetry Jander equation; R3 – phase boundary
reaction contracting volume spherical symmetry; A3 and A4 – random nucleation Avrami equation II (n=3) and (n=4), respectively
tion energy of decomposition reaction is in the range
24.4–84.9 kJ mol–1 which indicates that the
metal-ligand bond is very weak [14].
g-value was found to be 2.197 i.e. above the free ion
value (2.0023) which indicates that the metal-ligand
bond is more covalent than ionic [16].
The IR spectrum of the Co(II) macrocyclic com-
plex showed a shoulder at 3548 cm–1 and a band at
3416 cm–1 attributable to stretching vibration of
non-coordinated water molecules and bonded NH
group, respectively. The spectrum showed strong ab-
sorption bands at 1461 and 845 cm–1 which are caused
by CH2 deformation and rocking modes. The absorp-
tion band at 425 cm–1 can be assigned to the stretching
vibration of Co–NH.
The Co(II) complex has a magnetic moment
value equals to 4.13 BM which is consistent with the
reported value for the octahedral Co(II) complex [15].
The electronic spectrum, in Nujol mull, exhibited two
bands at 410 and 550 nm which may be assigned to
4T1g(F)®4T1g(P) (u3) and 4T1g(F)®4T2g(F) (u2) transi-
tions, respectively indicating the octahedral environ-
ment. The ESR spectrum of the solid Co(II) complex
at room temperature showed hyperfine splitting with
g-values of g||=2.608 and g^=1.992. The average
Ni(II) complexes
The analytical data of the Ni(II) complexes 2 and 3
along with other physical properties are listed in Ta-
ble 1. The conductance values in DMF solution show
the non-ionic nature of the complexes [11].
The curves of the Ni(II) complex 2 showed that
the mass loss step takes place between 50–150°C cor-
responding to loss of two molecules of hydration wa-
ter. This step is associated with an endothermic peak
at 200°C. The second mass loss step occurring be-
tween 300–400°C with an exothermic peak at 400°C
is due to the loss of Cl– ions. The final mass loss stage
between 400–510°C associated with a strong exother-
mic peak at 510°C is attributed to the decomposition
of the complex along the chelate bond leading to the
final product (NiO) from which Ni(II) content can be
calculated.
960
J. Therm. Anal. Cal., 91, 2008

NEW Co(II) AND Ni(II) HEXAAZA AND OCTAAZA MACROCYCLIC COMPLEXES
bands are assigned to 3A2g®3T1g(F) and
3A2g(F)®3T1g(P) transitions of the Ni(II) in an octahe-
dral configuration.
50–150°C 300–400°C
[NiLCl2 ]×2H2O¾¾¾®[NiLCl2 ]¾¾¾®
400–510°C
NiL¾¾¾®NiO
For the Ni(II)–complex 3 there is a loss of
hydration water molecule below 100°C. This step is
associated with a weak endothermic peak at ~100°C.
The second mass loss is associated with a strong exo-
thermic peak at 300°C corresponding to the loss of
NCS– ions. The third mass loss step takes place within
the temperature range 350–700°C associated with
exothermic peaks at 400–500°C. This temperature
range corresponds to the decomposition of the com-
plex with the formation of NiO as a final product.
Conclusions
The results of elemental, thermal analysis, conduc-
tance and magnetic moment measurements as well as
the spectral data reveal that the bonding of the metal
ion to the ligands in the macrocyclic complexes can
be represented as follows:
H
N
H
N
25–100°C 250–300°C
[NiL(NCS)2 ]×H2O¾¾¾®[Ni(NCS)2 ]¾¾¾®
>300
NiL¾¾®NiO
H
H
H
H
H
H
H
H
N
N
Cl
Ni
Cl
Cl
Co
Cl
N
N
N
N
N
N
2(H2O)
2(H2O)
The results of the kinetic analysis for the thermal
decomposition of the Ni(II)–complex 2 show that the
linear correlation coefficients are better when the proba-
ble mechanism functions are used; A4 for the first, A3
for the second and F1 for the third stage of decomposi-
tion. The significance of A4, A3 and F1 is listed in Ta-
ble 4. For Ni(II)–complex 3 the most probable mecha-
nisms are F1, F1 and R3 for the first, second and third
stage of decomposition, respectively. The kinetic pa-
rameters are listed in Table 4. The –ve values of DS indi-
cate that the reactions are slow in nature, hence assisted
by the wide range of decomposition temperature [17].
The IR spectra of Ni(II) complexes showed
broad bands at 3544 and 3564 cm–1 for Ni(II) com-
plexes 2 and 3, respectively, attributable to non-coor-
dinated water molecule. There are strong absorption
bands at 3247 and 3326 cm–1 for complexes 2 and 3,
respectively, which are assigned to uNH of the second-
ary amine. The IR spectrum of the thiocyanate Ni(II)
complex 3 shows a strong band at 2091 cm–1 and me-
dium intensity bands at 787 and 470 cm–1, attributed
to uC=N, uC=S and uNCS bending vibration, respectively
[18]. The position of these bands suggest the
monodentate behaviour of N-bonded thiocyanate
group [18]. The absence of the stretching and defor-
mation frequencies for NH2 and C=O groups of the
o-phenylenediamine and formaldehyde, respectively
indicates the formation of macrocyclic complex via
the nitrogen atoms of NH group for complex 2. For
complex 3, the presence of a new strong band at
1587 cm–1 confirm the formation of macrocyclic com-
plex via the nitrogen atom of the azomethine group.
The room temperature magnetic moment mea-
surements indicated that the Ni(II) complexes are
paramagnetic (meff=3.17 and 3.01 BM) for com-
plexes 2 and 3 respectively, hence the Ni(II) would
acquire octahedral geometry. The Nujol mull elec-
tronic spectra of these complexes are characterized by
two bands at 430 and 580 nm for Ni(II)–complex 2
and 440 and 560 nm for Ni(II)–complex 3. These
N
H
N
H
(CH2)5
Complex (2)
Complex (1)
H
H
N
N
N
N
NCS
Ni
H3C
H3C
CH3
(H2O)
N
N
N
N
CH3
NCS
H
H
(CH2)5
Complex (3)
All the complexes undergo a three-stage decom-
position pattern. The values of the activation energies
indicate that the metal-ligand bond is very weak. The
mechanism for the solid-state thermal decomposition
for the different decomposition stages is suggested.
The kinetic parameters of the decomposition steps are
affected by the nature of the metal ion as well as the
structural formula of the ligand. The entropy of acti-
vation observed with respect to the dehydration steps
has small negative values. This can be explained on
the premise that the first degradation step involves
two simultaneous processes; the first is volatilization
of the water molecules from the solid complex with
positive DS and the second is the formation of more
ordered anhydrous complex with negative DS. The
determined values result from both processes.
References
1 A. Chaudhary, S. Dave, S. R. Swaroop and R. V. Singh,
J. Ind. Chem. Soc., 79 (2002) 371.
2 R. D. Yones, D. A. Summerville and F. Basolo, Chem.
Rev., 79 (1979) 139.
3 A. Kumar Singh, R. Singh and R. Saxena, Transition Met.
Chem., 29 (2004) 867 and references therein.
4 O. V. Mikhailov, M. A. Kazymova, T. A. Shumilova and
S. S. Solovieva, Transition Met. Chem., 29 (2004) 732.
5 S. K. Gupta and D. Raina, Transition Met. Chem.,
22 (1997) 225.
J. Therm. Anal. Cal., 91, 2008
961

GABER et al.
6 W. Yan, C. Ma, J. Wu, W. Zhang and D. Jang, J. Therm.
Anal. Cal., 85 (1999) 393.
15 B. N. Figgis and J. Lewis, ‘Progress in Inorganic Chemis-
try’, Interscience, New York 1964, 6, p. 37.
7 Z. Vargova, K. Györyová and V. Zelenák, J. Therm. Anal.
Cal., 76 (2004) 97.
16 I. Fidone and K. W. Stevens, Proc. Phys. Soc., London,
73 (1959) 116.
8 D. H. Busch and J. C. Bailar, J. Am. Chem. Soc.,
78 (1956)1137.
17 M. M. Omar, J. Therm. Anal. Cal., 68 (2002) 1003.
18 K. Nakamoto, Infrared Spectra of Inorganic and Coordina-
tion Compounds, Wiley, Interscience, New York 1970.
9 A. W. Coats and J. P. Redfern, Nature, 20 (1964) 68.
10 V. Satava, Thermochim. Acta, 2 (1971) 423.
11 W. J. Geary, Coord. Chem. Rev., 7 (1971) 81.
12 M. K. M. Nair and P. K. Radhakrishnan, J. Thermal Anal.,
52 (1998) 475.
Received: June 16, 2007
Accepted: July 11, 2007
13 C. R. Vinodkumar, M. K. M. Nair and
P. K. Radhakrishnan, J. Therm. Anal. Cal., 61 (2000) 143.
14 T. Ganga Devi, K. Muraleedharan and M. P. Kannan,
Thermochim. Acta, 191 (1991) 105.
DOI: 10.1007/s10973-007-8609-3
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J. Therm. Anal. Cal., 91, 2008