Thermal investigation of iron(III) and manganese(II, III) complexes of dianils derived from 6-formylkhellin: Synthesis, characterization

Article abstract of DOI:10.1023/A:1025875707494

Manganese and iron complexes of Schiff bases derived from 6-formylkhellin were prepared and characterized. Complexes of o-phenylenediamine derivative (ligand (I)) are monomeric or dimeric whereas those of p-phenylenediamine derivative (ligand (II)) are polymeric. The complexes obtained are characterized by a lower magnetic moment values. The complexes also have different solvent of crystallization with different nature of interaction. The thermal behaviour of the ligands and their metal complexes was investigated by means of DTA, TG, IR and X-ray diffraction spectroscopy. Ligand (I) shows different thermal behaviour from that of ligands (II) and (III). The complexes of ligand (II) give abnormal oxides as a final product during their thermal decomposition.

Full text of DOI:10.1023/A:1025875707494

Journal of Thermal Analysis and Calorimetry, Vol. 73 (2003) 987–1000
THERMAL INVESTIGATION OF IRON(III) AND
MANGANESE(II, III) COMPLEXES OF DIANILS
DERIVED FROM 6-FORMYLKHELLIN
Synthesis, characterization
*
A. M. Donia, H. A. El-Boraey and M. F. El-Samalehy
Department of Chemistry, Faculty of Science, Menoufia University, Shebin El-Kom, Egypt
(
Received November 18, 2002; in revised form February 2, 2003)
Abstract
Manganese and iron complexes of Schiff bases derived from 6-formylkhellin were prepared and
characterized. Complexes of o-phenylenediamine derivative (ligand (I)) are monomeric or dimeric
whereas those of p-phenylenediamine derivative (ligand (II)) are polymeric. The complexes ob-
tained are characterized by a lower magnetic moment values. The complexes also have different sol-
vent of crystallization with different nature of interaction. The thermal behaviour of the ligands and
their metal complexes was investigated by means of DTA, TG, IR and X-ray diffraction spectros-
copy. Ligand (I) shows different thermal behaviour from that of ligands (II) and (III). The complexes
of ligand (II) give abnormal oxides as a final product during their thermal decomposition.
Keywords: DTA, 6-formylkhellin, IR spectroscopy, manganese and iron complexes of Schiff
bases, o-phenylenediamine, p-phenylenediamine, TG, X-ray diffraction
Introduction
Since the days of the ancient Egyptians, physicians emphasized on the utility of naturally
occurring drugs. Furochromones can be used in relieving the pain of renal colics and
urterial spasms and in facilitating the passage of urterial stones. Later, it became well
known that some furochromone derivatives possess coronary vasodilating activity [1, 2].
Several substituted furochromones show potential spasmolytic activity [3, 4]. This pro-
nounced activity stimulated the interest in the synthesis of heterocyclic compounds de-
rived from 3-formylkhellin for medicinal chemistry programs. For example,
chromone-3-carboxaldehyde (I) occupies a unique position because it contains
O–C=C–C=O group which is being responsible for its biological activity [5].
On the other hand, furobenzopyrones occupy a position of considerable signifi-
cance as a result of their widespread occurrence in the plants and their potential as
pharmaceuticals [6–9]. One of the members of that important category is 6-
*
Author for correspondence: E-mail: helboraey@yahoo.com
1
388–6150/2003/ $ 20.00
Akadémiai Kiadó, Budapest
©
2003 Akadémiai Kiadó, Budapest
Kluwer Academic Publishers, Dordrecht

9
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DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
formylkhellin (II), which can be obtained from the chemical treatment of the natu-
rally occurring furochromones (khellin).
The carboxaldehyde group in 6-formylkhellin occupies a unique position. So, a
number of heterocyclic compounds can easily be obtained through the chemical reac-
tions with it. For example, when compound (II) was treated with primary aromatic or
heterocyclic amines in (1:1) mole ratio, it gives the corresponding anils (III).
But on treatment with an excess of amines the corresponding 6-(amino-
methylene)-7-amino derivatives (IV) were obtained [10–12].
Literature survey shows no work have been done on the metal complexes of
those anils or their dianils. In the present work, a number of dianils ligands of
6
-formylkhellin and their metal complexes with iron and manganese ions were pre-
pared and characterized. The thermal behaviour of the compounds obtained is also
studied by means of DTA/TG, IR and X-ray, diffraction spectroscopy.
J. Therm. Anal. Cal., 73, 2003

DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
989
Experimental
All reagents were of pure grade and were used as submitted from Aldrich.
Preparation of ligands (Schiff bases)
A chloroform solution of 6-formylkhellin in appropriate molar ratio was added to
o-phenylenediamine (ligand (I)) or p-phenylenediamine (ligands (II) and (III)) in
chloroform. The molar ratios were (1:1) for ligands (I) and (II) and (2:1) for
ligand (III). The reaction mixtures were stirred in air with warming for 3 h. The red or
orange precipitates obtained were collected by filtration, washed by methanol several
times and dried over, CaCl /P O10 mixture for one week before measurements. In the
2 4
case of ligand (III) diethylether was added to assist good precipitation.
The analytical and spectral data (Table 1) suggest the following structures for
the compounds.
Scheme 1
Preparation of complexes
Complexes (1–4) were prepared by the addition of stoichiometric amount of hydrated
metal chloride in methanol to a warm solution of 6-formylkhellin and the appropriate
amine (1:1:1) molar ratio in chloroform. The reaction mixture was stirred in air for
3
h. Diethylether was added to assist good precipitation. The formed precipitates
J. Therm. Anal. Cal., 73, 2003

Table 1a Elemental analysis, molar conductance of the investigated ligands and their complexes
*
C/%
found
H/%
M/%
found
Λ /
mol cm
No.
Compound
Colour
–1
Ω
–1
2
calc.
66.1
63.9
60.5
55.6
50.8
48.4
46.4
calc.
5.0
4.0
4.4
4.2
4.1
4.5
4.2
found
4.8
calc.
–
Ligand (I)
Ligand (II)
orange
66.2
63.8
60.3
55.8
50.9
48.4
46.6
–
–
–
dark orange
red
4.0
–
–
Ligand (III)
I
[MnL Cl
4.3
–
–
–
(1)
(2)
(3)
(4)
2
]
2
⋅2C
2
H
5
OC
OH+0.5C
OH+4H O+2Cl)
OH+10H O+2Cl)
2
H
5
orange
4.2
6.6
6.6
6.0
6.2
6.2
6.5
6.3
6.2
20
129
a
I
[FeL Cl
2
]⋅(2.5CH
3
2
H
5
OC
2
H
5
+Cl)
black
4.3
II
[MnL Cl ] ⋅(7CH
3
2
n
dark brown
dark brown
4.6
2
4 n
II
[Fe L Cl ] ⋅(2CH
3
2
n
4.5
a
2
2
4 n
–
=molar conductance in 10 M DMF
3
*
a=insoluble
I
II
L , L =Schiff bases derived from 6-formylkhellin and o-phenylenediamine

Table 1b IR spectral data of the investigated ligands and their complexes
–1
IR ν/cm
No. Compound
–
OH
NH
2
–CH
2
–OCH
3
C=O
C=N
C=C
M–O M–N M–Cl
3
3
3
480
s)
3220–
3110(m)
2920
(m)
2820
(m)
1640
(vs)
1570
(s)
Ligand (I)
Ligand (II)
–
–
–
–
–
–
–
–
–
–
(
420
br)
2920
(m)
2820
(m)
1665
(m)
1640
(m)
1555
(m)
–
–
(
420
2920
(m)
2820
(m)
1670
(s)
1640
(m)
1565
(m)
Ligand (III)
(
br)
3400
br)
3400
br)
3400
br)
3400
br)
I
1) [MnL Cl
2920
(m)
2820
(m)
1640
(m)
1610
(s)
1590
(s)
520
(m)
410
(m)
310
(m)
(
(
(
(
2
]
2
⋅2C
2
H
5
OC
OH+0.5C
⋅(7CH OH+4H
2 5
H
(
I
2) [FeL Cl
2920
(m)
2820
(m)
1650
(m)
1610
(s)
1550
(m)
530
(m)
450
(m)
300
(m)
2
]⋅(2.5CH
3
2 5 2 5
H OC H +Cl)
(
II
2915
(m)
2820
(m)
1650
(s)
1620
(s)
1570
(m)
520
(m)
410
(m)
320
(m)
3) [MnL
CL
]
3
2
O+2Cl)
n
2
4
n
(
II
2915
(m)
2820
(m)
1640
(m)
1620
(m)
1580
(m)
530
(m)
410
(m)
300
(m)
4) [Fe
L
Cl
]
3 2 n
⋅(2CH OH+10H O+2Cl)
2
2
4
n
(
s=strong; br=broad; m=medium
I
II
L , L =Schiff bases derived from 6-formylkhellin and o-phenylenediamine

9
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DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
were collected by filtration, washed subsequently by chloroform and methanol and
then dried over CaCl /P O . The reactions can be represented as follows:
2
4
10
FeCl3⋅6H2 O (1:1:1)
MnCl2 ⋅4H2 O (1:1:1)
(
2) ← 6-formylkhellin+o-phenylenediamine  (1)
(ligand(I))
FeCl3⋅6H2 O (1:1:1)
MnCl2 ⋅4H2 O (1:1:1)
(
4) ← 6-formylkhellin+ p-phenylenediamine  (3)
ligand(II))
(
Elemental analysis (C, H) were carried out at Microanalytical centre of Cairo
University, metal contents were estimated compleximetrically by back titration using
EDTA and Eriochrome Black-T (EBT) indicator [13]. IR spectra were recorded using
a Perkin Elmer 1430 spectrophotometer and KBr discs. Electronic spectra were mea-
sured in Nujol mulls using a Perkin Elmer Lambda-4B spectrophotometer. The mag-
netic susceptibility measurements were carried out at room temperature using a mod-
ified Goy-type magnetic balance Herts SG8 5HJ, England. Diamagnetic corrections
were calculated from the values given by Selwood and Pascall’s constants [14]. The
–
3
molar conductivity measurements of the complexes were done in DMF (10 M) us-
ing Tacussel conductimeter type CD6N. The thermal analysis (DTA and TG) were
–
carried out by using a Shimadzu DTA/TG-50 with a heating rate 10°C min in nitro-
1
3
gen atmosphere. The flowing rate of N is 30 cm min . X-ray powder diffraction
–1
2
patterns were measured using a Shimadzu XD-3 diffractometer with CuK radiation.
α
Results and discussion
The ligands and their complexes are stable in air at room temperature. Complexes of
ligand (I) have an appreciable solubility in hot dimethylformamide (DMF). Whilst
those of ligand (II) are insoluble in most organic solvents. This behaviour may be at-
tributed to their polymeric nature. The observed lower conductivity value of com-
2
–1
–1
plex (1) in DMF (20 cm Ω mol ) reveals its non-electrolytic nature [15]. Com-
2
–1
–1
plex (2) displays a higher value of molar conductance (129 cm Ω mol ) which is
consistent with that of univalent electrolyte [16, 17]. The complexes are character-
ized by the presence of a large number of solvents of crystallization. This may be at-
tributed to the presence of a high content of oxygen sites in the ligands, that are capa-
ble of formation of hydrogen bonding with the solvents.
Vibrational spectra
When 6-formylkhellin was treated with excess amines the corresponding 6-(amino-
methylene)-7-amino derivatives with the general formula (IV) were obtained [10–12].
The reaction proceeds via the formation of anils which in turns undergoes a nucleophilic
addition of one molecule of amine. The most characteristic (IR) bands of the ligands are
given in Table 1.
J. Therm. Anal. Cal., 73, 2003

DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
993
Ligand (I)
–
Ligand (I) displays bands near 3480, 3220–3110 (split), 2920, 2820 and 1640 cm .
1
These bands are assigned to νOH, νNH, νCH–aliphatic, νOCH and νC=N, respec-
3
tively [16–21]. The appearance of νOH and νNH confirms the nucleophilic addition
of one amine molecule via the conversion of (C=O) of the pyrone ring (appears at
–
1
1
665 cm ) to a hydroxyl group. On the other hand, the disappearance of ν(C=O) of
the aldehydic group, confirms its condensation with another molecule of amine to
form the anil moiety (C=N), (vide the structure of ligand (I)).
Ligands (II) and (III)
Ligands (II) and (III) display bands near 3420, 2920, 2820, 1670–1665), 1640, and
–
1
1
555 cm . These bands are assigned to νOH of water, νCH-aliph. νOCH , νC=O,
3
νC=N and νC=C, respectively [16–21]. The appearance of νC=O of pyrone ring
–
1670–1665 cm ), indicates that the condensation takes place via (–NH ) group of
1
(
2
amine and aldehydic (CHO) group of 6-formylkhellin. The disappearance of νNH2
from the spectrum indicates that two molecule of 6-formylkhellin react with one mol-
ecule of amine to give the dianils. This was also confirmed by elemental analysis
data. The TG mass losses correspond to one molecule of water of crystallization
(
2.8%) for ligand (II) and three molecules (8.2%) for ligand (III).
Complexes
The most characteristic infrared peaks of the investigated complexes are given in Table 1.
–1
The complexes display bands near 3400, 2920–2915, 2820 cm . These bands were as-
signed to νOH of water and/or methanol molecules, νCH-aliph. and νOCH moiety, re-
3
–1
spectively [16–18]. The observed peaks near 1650–1640 and 1620–1610 cm were as-
signed to νC=O of pyrone ring and νC=N of azomethine group, respectively [19–21].
The observed shifts in these bands to lower frequency on comparison with those of the
ligands and the parent 6-formylkhellin indicate the participation of both C=O and C=N
moieties in the mode of coordination [21, 22]. This coordination behaviour indicates that,
ligand (I) (template reaction between 6-formylkhellin, o-phenylenediamine and metal
ion) behaves as a dianil rather than nucleophilic addition to give 6-(aminomethylene)-
–1
7-amino derivative (Scheme I). The spectra also show a band near 1590–1550 cm
which was assigned to νC=C of aromatic ring. The complexes also display bands in the
–1
regions 530–520 and 450–410 cm . These bands are assigned to νM–O and νM–N, re-
spectively [16, 21, 23–25]. The observed bands near 320–300 cm was assigned to ter-
–1
minal νM–Cl [22, 26, 27].
Electronic spectra
Electronic spectral data of the complexes in nujol mulls and their room temperature mag-
netic moments are given in Table 2. The spectrum of Mn(II) complex, (1) displays bands
near 560–520 and 420 nm. These bands suggest an octahedral geometry around Mn(II)
[28]. The lower magnetic moment value (3.0 BM) may be due to the presence of an equi-
J. Therm. Anal. Cal., 73, 2003

9
94
DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
librium between high and low spin states [29] together with a metal–metal interaction.
The spectrum of Mn(III) complex, (3) shows a broad band near 480 nm in both nujol
mulls and DMF solution. This indicates that the complex doesn’t alter its geometry in so-
lution. The appearance of that band can be assigned to Jahn–Teller distorsion in an octa-
hedral geometry around Mn(III) [28, 29]. The observed lowering in the magnetic mo-
ment value (4.3 BM) can be attributed to the presence of some extent of high–low spin
equilibrium in the same solid [29]. The higher value of µ (4.3 BM) of Mn(III) complex
eff
than that of Mn(II) complex (3.0 BM) is consistent with its structure, which shows no
metal–metal interaction. The spectra of iron(III) complexes (2, 4) display absorption
bands near 660–500 and 480 nm. These bands are assigned to octahedral geometry
around Fe(III) [27, 30–32]. The magnetic moment value (5.5 BM) of complex (2) is con-
5
sistent with high spin d configuration in an octahedral field [27]. Whilst that of com-
5
plex (4) is lower than that of high spin d configuration, indicating the probability of an
equilibrium between high and low spin states [33].
Table 2 Magnetic and electronic spectral data of the investigated complexes
Electronic spectra in
Nujol mulls/nm
No. Complex
µeff/BM
I
[MnL Cl
560–520 (w/br),
(
1)
2)
2
]
2
⋅(2C
2
H
5
OC
OH+0.5C
OH+4H
OH+10H
3
H
5
)
3.0
4
20 (m)
600–500 (m/br),
50 (m)
I
[FeL Cl
(
(
(
2
]⋅(2.5CH
3
2
2
2
H
5
OC
2
H
5
+Cl)
5.5
4.3
4.0
4
II
3) [Mn L Cl ] ⋅(7CH
3
O+2Cl)
n
n
480 (br)
2
2
4
n
II
600–520 (m/br),
4
4) [Fe
L
Cl
]
⋅(2CH
3
O+2Cl)
2
2
4
n
80 (br)
br=broad; m=medium; w=weak
Based on the above arguments, together with the elemental analyses, and molar
conductance (Table 1), the following formulae can be suggested.
J. Therm. Anal. Cal., 73, 2003

DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
995
Thermal studies
Ligands
DTA and TG curves of ligands (I), (II) and (III) are shown in Fig. 1. The thermal analysis
data were also collected in Table 3. The DTA curve of ligand (I) shows a broad exother-
mic peak in the temperature range 33–252°C. TG curve shows no mass loss in that tem-
perature range. This DTA peak can be assigned to lattice or chemical rearrangement of
the compound. The observed DTA peak in the temperature range 252–310°C is assigned
to material decomposition via the loss of one molecule of aniline. This assignment was
confirmed by the TG mass losses (Table 3). DTA curve of ligand (II) shows a very weak
endothermic peak in the temperature range 34–90°C. The TG mass loss (2.8%) in that
temperature range confirms a loss of one molecule of water of crystallization. The lower
temperature of dehydration as well as the very weak nature of DTA peak indicate that the
water of crystallization doesn’t participate in the lattice forces [34–37]. The curve dis-
plays also another endothermic peak in the temperature range 90–311°C which can be as-
signed to decomposition of the compound. TG data (Table 3) suggest that the decomposi-
tion takes place through the loss of two molecules of carbon monoxide as a result of the
degradation of the pyrone ring. DTA curve of ligand (III) displays an endothermic peak
in the temperature range 90–150°C. This peak is assigned to loss of three molecules
(8.4%) of water of crystallization. It is seen that the loss of water of crystallization takes
place in one definite step (strong DTA peak). This, in addition to the higher temperature
J. Therm. Anal. Cal., 73, 2003

9
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DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
1
Fig. 1 DTA and TG curves of ligands (L , L , L )
2
3
of dehydration relative to that of ligand (II), indicates the participation of water molecules
in the lattice forces. The dehydration peak was followed by two endothermic peaks with
maxima at 244 and 343°C, respectively. These peaks are assigned to melting (244°C) to-
gether with the loss of two molecules of carbon monoxide in two individual steps as
shown in TG curve. Again, the decomposition takes place via the decomposition of the
pyrone ring. The great similarity between the thermal behaviour of both ligands (II)
and (III) reflects their similarity in room temperature structures. The observed differences
in their thermal stability may be related to the different number and the nature of interac-
tion of water of crystallization. On the other hand, the higher thermal stability and differ-
ent thermal behaviour of ligand (I) relative to that of (II) and (III) can be attributed to their
different structures.
Complexes
DTA and TG curves of the complexes are shown in Fig. 2. The thermal analysis data are
also given in Table 3. DTA and TG curves indicate that the complexes loss their solvent
of crystallization in one or more steps. The desolvation process is generally extended
over a broad temperature range (24–245°C) and mainly starts from room temperature.
This process sometimes overlap with the decomposition process (complexes 2 and 4).
The appearance of different endothermic DTA peaks at different temperature ranges in-
dicates the different nature of interaction of the solvents of crystallization in the lattice.
The lower onset temperature of desolvation process and its extended range of tempera-
ture indicate that the solvents of crystallization are present in the crystal voides and there-
fore play no significant role in the lattice forces [34–38]. The desolvation peaks are fol-
J. Therm. Anal. Cal., 73, 2003

Table 3 DTA and TG data of the investigated ligands and their complexes
Temperature/°C
Mass loss/%
No. Compound
Reaction Assignment
c
DTA
TG
calc.
found
33–252
max. 136)
(
2
(
Ligand (I)
Ligand (II)
52–310°
max. 292)
252–310
18.6
18.7
d
–RNH
2
3
9
4–90
0–311
34–90
90–311
2.8
9.0
2.8
8.8
a
2
–H O
d
–2CO
9
0–150
max. 126)
50–180
max. 244)
80–385
max. 343)
90–150
8.0
8.3
a
–
d
2
–3H O
(
(
(
1
–
meltimg
–2CO
Ligand (III)
2
150–385
8.2
8.3
2
7
4–70
0–140
24–70
70–140
140–190
190–313
313–582
at 582
6.7
1.1
1.1
6.7
1.0
1.0
17.26
67.5
6.5*
b
b
b
d
d
–1.5C
–0.25C
–0.25C
2
H
5
OC
2
H
5
2
2
H
H
5
5
OC
OC
2
2
H
5
I
1) [MnL Cl
140–190
90–313°
13–582
H
5
(
(
2
]
2
2 5 2 5
⋅2C H OC H
1
3
6.6
≡2Mn
3
4–105
105–170
70–245
45–710•
34–105
105–170
170–245
4.1
1.7
7.1
4.0
1.7
7.1
b
b
b
d
2 5 2 5
–0.5C H OC H
–0.5CHOH
–2CHOH
I
2) [FeL Cl
2
3 2 5 2 5
]⋅(2.5CH OH+0.5C H OC H +Cl)
1
2
24–130
200–670°
24–130
130–670
at 670
15.9
10.1
16.0
73.9
10.1*
a+b
d
–(7CHOH+4H
–
≡2MnO2.5
2
O)
II
(
3) [MnL
Cl
]
3 2 n
⋅(7CH OH+4H O+2Cl)
2
4
n
2
6–170
170–470°
70–775
26–170
170–470
at 470
13.5
76.5
9.7
13.5
a
d
–(10H
–
≡2FeO
2 3
O+2CH OH)
II
(
4) [Fe
2
L
2
Cl
4
]
n
⋅(2CH
3
OH+10H
2
O+2Cl)
n
4
9.9*
2
a=dehydration; b=desolvation; c=lattice or chemical rearrangement; d=decomposition; •=splitted; *=final product percent; °=exo

9
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DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
Fig. 2 DTA and TG curves of complexes (1–4)
lowed by a number of exothermic peaks in the temperature range (170–670°C). These
peaks are assigned to material decomposition. Manganese(II) complex, (1) starts its de-
composition at 190°C to give manganese metal as a final product at 582°C. The forma-
tion of manganese metal confirms the reducing behavior of the ligand (I) during its ther-
mal decomposition [39]. Manganese(III) complex, (3) starts its decomposition at 200°C
to give MnO2.5 as a final product (Table 3). The formation of a high oxidation state of
manganese in spite of the reducing properties of the ligand during its decomposition can
be explained on the basis of the very low reducibility of Mn(III) in comparison with that
of Mn(II) [40] and/or the lower reducing properties of ligand (II) during its decomposi-
tion. Iron(III) complex, (2) starts its decomposition at 245°C. The complex doesn’t com-
plete its decomposition up to 800°C, indicating its higher thermal stability. This higher
thermal stability may be attributed to the presence of three fused chelate rings with higher
degree of conjugation around the metal ion. Iron(III) complex, (4) starts its decomposi-
tion at 170°C to give finally FeO
(FeO ) confirms the lower reducing properties of ligand (II) vs. oxidation state(III) of iron
as a final product. The formation of this type of oxide
2
2
and manganese. The final product of the thermal decomposition of complexes (1, 3
and 4) were investigated by means of X-ray and IR spectra. X-ray spectra show that the
oxides obtained are characterized by a lower degree of crystallinity. IR spectra show no
characteristic peaks of the ligand, indicating the complete decomposition of the com-
plexes at the corresponding temperature (Table 3).
On the basis of the above studies, the following points can be outlined:
1] Ligand (I) gives monomeric or dimeric complexes whereas ligand (II) gives
polymeric complexes.
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DONIA et al.: IRON(III) AND MANGANESE(II, III) COMPLEXES
999
2
] The complexes obtained are characterized by the presence of different sol-
vents of crystallization with different nature of interaction.
] Ligand (I) displays a different thermal behaviour from that of ligands (II)
and (III). This may be attributed to their different structures.
] o-phenylenediamine derivative (ligand (I)) displays reducing properties dur-
3
4
ing the thermal decomposition of its metal complexes to give finally the metal. Whilst
p-phenylenediamine derivative (ligand (II)) displays oxidation effect to give abnor-
mal oxides (MnO2.5 and FeO
).
] Ligand (II) stabilized the oxidation state (III) for manganese in the solid complex.
] The thermal behaviour of the ligands and their metal complexes is consistent
2
5
6
with their room temperature structures.
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