The synthesis and characterization of single substitute melamine cored Schiff bases and their [Fe(III) and Cr(III)] complexes

Article abstract of DOI:10.1007/s10847-010-9762-z

In this study, firstly, two single substitute novel ligands have been synthesized by reacting melamine with 3,4,-dihydroxybenzaldeyhde or 4-carboxybenzaldehyde. Then, eight new mono nuclear single substitute [Salen/Salophen Fe(III) and Cr(III)] complexes

Full text of DOI:10.1007/s10847-010-9762-z

J Incl Phenom Macrocycl Chem (2010) 68:165–173
DOI 10.1007/s10847-010-9762-z
ORIGINAL ARTICLE
The synthesis and characterization of single substitute melamine
cored Schiff bases and their [Fe(III) and Cr(III)] complexes
_
S¸aban Uysal H. Ismet Uc¸an
•
Received: 16 October 2009 / Accepted: 18 February 2010 / Published online: 5 March 2010
Ó Springer Science+Business Media B.V. 2010
Abstract In this study, firstly, two single substitute novel
ligands have been synthesized by reacting melamine with
3,4,-dihydroxybenzaldeyhde or 4-carboxybenzaldehyde.
Then, eight new mono nuclear single substitute [Salen/
Salophen Fe(III) and Cr(III)] complexes have been synthe-
sized by reacting the ligands [2-(3,4-dihydroxybenzimino)-4,
6-diamimo-1,3,5-triazine and 2-(4-carboxybenzimino)-4,
6-diamimo-1,3,5-triazine)] with tetradentate Schiff bases
N,N0-bis(salicylidene)ethylenediamine-(salenH2) or bis(sali-
cylidene)-o-phenylenediamine-(salophen H2). And then, all
ligands and complexes have been characterized by means of
elementel analysis, FT-IR spectroscopy, 1H NMR, LC–MS,
thermal analyses and magnetic suscebtibility measurements.
Finally, metal ratios of the prepared complexes were deter-
mined using AAS. The complexes have also been character-
ized as disorted octahedral low-spin Fe(III) and Cr(III)
bridged by catechol and COO- groups.
electrical properties [4]. Phenolic melamine is a good non-
flammable resin owing to its nitrogen content in the
chemical structure [5].
The magnetochemical properties of the l-oxo-bridged
complexes and their X-ray studies have widely been pre-
sented in the literature [6–13]. The reaction of [{Fe(sa-
len)}2O] with carboxylic acids has been described by
Wollmann and Hendrickson [14]. Koc¸ and Uc¸an [15] have
reported the synthesis and characterization of 1,3,5-tri-
carboxylato bridges with [SalenFe(III)] and [Salo-
phenFe(III)]. In our previous studies, we also reported the
synthesis and characterization of 1,3,5-tricarboxylato and
1,3,5-tris(catechol) bridges with [SalenFe(III)], [Salo-
phenFe(III)], [SalenCr(III)] and [SalophenCr(III)] [16, 17].
The anion of the Schiff base N,N0-ethylene-bis-(salicy-
lideneiminato) (Salen) or ‘Salen-type’ ligands and their
complexes have been considered as interesting species in
many fields of chemical research because of some specific
properties. Fe(Salen) complexes have been extensively
studied in the solid state and in solution. Barone et al. [18]
show a catalytic activity toward the blend oxidation of
hydrocarbons and undergo electron transfer reactions,
mimicking the catalytic functions of peroxidases. Geta-
chew et al. synthesized a water soluble Fe(III)-salen
complex and studied its biochemical effects on DNA
in vitro and on cultured human cells. They showed that
Fe(III)-salen produces free radicals in the presence of the
reducing agent, dithiothreitol (DTT), and induces DNA
damage in vitro. Their results demonstrated that Fe(III)-
salen not only damages DNA in vitro, but also induces
apoptosis in human cells via a mitochondrial pathway [19].
We have especially prefered chromium complexes
because chromium is a unique transition metal ion, which
has been established to be biologically significant at all the
levels of living organisms [20]. Out of the two stable
Keywords Melamine ꢀ Salen ꢀ Salophen ꢀ Schiff bases ꢀ
Catechol
Introduction
Melamine (2,4,6-triamino-1,3,5-triazine) resins have been
used in many applications. 1,3,5-Triazine derivatives are
widely used as herbicides [1], drugs [2] or polymers [3]
like melamineformaldehyde that has excellent thermal and
_
S¸. Uysal (&) ꢀ H. I. Uc¸an
Department of Chemistry, Faculty of Science, Selcuk University,
42075 Konya, Turkey
e-mail: uysal77@hotmail.com
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J Incl Phenom Macrocycl Chem (2010) 68:165–173
pffiffiffiffiffiffi
oxidation states of chromium, -VI and -III, trivalent chro-
mium has been shown to play a positive role in controlling
carbohydrate and lipid metabolism [21]. Chromium(III)
Schiff base complexes (especially [Cr(salen)(OH2)2]?)
have been found to enhance insulin activity, and similarly
insulin derivatives have been found to exhibit higher
activity in glucose metabolism in animal models when
compared to both free insulin and other derivatives [22,
23]. A broad range of asymmetric catalytic reactions have
been described including oxidations, additions and reduc-
tions such as the epoxidation of olefins, epoxide ring
opening [24–28]. Various metal-Salen complexes such as
manganese(III) [29], chromium(III) [30] and nickel(II)-
Salen [31] have been used for the epoxidation of olefins
[32].
calculated from the expression: leff: ¼ 2:84 vMT B.M.,
where vM is the molar susceptibility.
Preperation of ligand complexes
[Fe(salen)]2O, [Fe(salophen)]2O, [Cr(salen)]2O and
[Cr(salophen)]2O were prepared by adding concentrated
ammonia solution (26% w/w) till alkaline to hot EtOH
solutions of [Fe(salen)]Cl, [Fe(salophen)]Cl, [Cr(salen)]Cl
and [Cr(salophen)]Cl, respectively [33–35].
Synthesis of 2-(3,4-dihydroxybenzimino)-4,6-diamimo-
1,3,5-triazine L1 (II)
A suspension of melamine (6.30 g, 50 mmol) in 200 mL
dry benzene was stirred at room temperature for 1 h. An
equivalent amount of 3,4-dihydroxybenzaldehyde (6.90 g,
50 mmol) was added to suspension portion by portion. The
mixture was stirred for 48 h. The white product was col-
lected by filtration and then dried in vacuo. The obtained
mixture was purifed using Combi Flash Chromatography
and using 1:1 acetone/chloroform mixture as eluent. The
product was recrystallized from a mixture of methanol and
water (1:1). Yield: 90% (11.07 g). The characterization
data for II are given in Tables 1, 2 and 3.
The aim of the present study is to synthesize novel
single substitute mononuclear systems and to present their
effects on magnetic behaviour of [salen/salophenFe(III)]
and [salen/salophenCr(III)] capped complexes. We are
thinking of synthesizing polymer systems out of the single
substitute mononuclear systems in near future.
Experimental
Materials and methods
The synthesis of 2-(4-carboxybenzimino)-4,6-diamimo-
1,3,5-triazine L2 (III)
Melamine, 3,4-dihydroxybenzaldehyde, 4-carboxybenzal-
dehyde and all other reagents were purchased from Merck
and used without further purification. [Fe(salen)]2O,
[Fe(salophen)]2O, [Cr(salen)]2O and [Cr(salophen)]2O
were prepared according to previously published methods
[31–33]. L1FeSalen(IV), L1FeSalophen(V), L1CrSalen(VI),
L1CrSalophen(VII), L2FeSalen(VIII), L2FeSalophen(IX),
L2CrSalen(X) and L2CrSalophen(XI) complexes were
A suspension of melamine (6.30 g, 50 mmol) in 200 mL of
dry benzene was stirred at room temperature for 1 h. An
equivalent amount of 4-carboxybenzaldehyde (7.50 g,
50 mmol) was added to suspension portion by portion. The
mixture was stirred for 48 h. The white product was col-
lected by filtration and then dried in vacuo. The obtained
mixture was purified using Combi Flash Chromatography
and using 1:1 acetone/chloroform mixture as eluent. The
product was recrystallized from a mixture of methanol and
water (1:1). Yield: 92% (11.88 g). The characterization
data for III are also given in Tables 1, 2 and 3.
1
synthesized according to the following methods. H-NMR
spectra were taken using a Varian-Mercury 200 NMR
spectrometer. The chemical shifts for NMR spectra are
ascribed in relation to the external standard of TMS. IR
spectra were recorded using a Perkin-Elmer 1600 FT-IR
spectrometer and through KBr pellets. Elemental analyses
were carried out using a Hewlett-Packard 185 analyzer.
Metal contents in complexes were determined using Uni-
cam 929 AAS spectrometer. Mass spectra of the com-
pounds were obtained through Varian MAT 711
spectrometer. pH values were measured through a WTW
pH, 537 pH meter. The purification of the products
obtained at the end of the reaction was carried out using
Combi Flash Chromatography. Magnetic susceptibilities of
metal complexes were determined using a Sheerwood
Scientific MX Gouy magnetic susceptibility apparatus
using the Gouy method with Hg[Co(SCN)4] as calibrant.
The effective magnetic moments, leff, per metal atom were
Preparation of L1FeSalen(IV), L1FeSalophen(V),
L1CrSalen(VI) and L1CrSalophen(VII) complexes
A solution of L1 (0.49 g, 2.0 mmol) and [Fe(salen)]2O or
[Fe(salophen)]2O or [Cr(salen)]2O or [Cr(salophen)]2O
(1.0 mmol) in 100 mL of absolute ethanol were refluxed
for 3 h. The mixture was allowed to cool down to room
temperature. Then, the mixture was filtered and dried in
vacuum. Yield: 80% (0.90 g), 81% (1.00 g), 64% (0.85 g),
60% (0.73 g) for IV, V, VI and VII, respectively. The
characterization data for IV, V, VI and VII are given in
Tables 2–3.
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167
1
Table 1 The H-NMR data of
?
Compounds
NH2
–
NH3
C–Harom.
HC=N–
ligands in DMSO-d6
C10H10N6O2
L1 (II)
6.06 (6H, s)
6.89–6.92 (1H, d)
7.23–7.26 (1H, dd)
7.28–7.29 (1H, d)
6.89–6.92 (1H, d)
7.23 (1H, dd)
9.70 (1H, s)
C
10H10N6O2
3.91 (4H, s)
–
9.66 (1H, s)
L1 (II), D2Oex
7.29–7.30 (1H, d)
7.98–8.02 (2H, dd)
8.12–8.16 (2H, d)
7.97–8.00 (2H, d)
8.01–8.13 (2H, d)
C
11H10N6O2
L2 (III)
11H10N6O2
L2 (III), D2Oex
–
6.36 (6H, s)
–
10.10 (1H, s)
10.06 (1H, s)
C
3.76 (4H, s)
Table 2 Some physical properties, molecular weight (g/mol) data and elemental analyses, AAS analyses of the ligands and complexes
No
Compounds
lB
M.p. (°C)
Color MW (g/mol)
Found calculated % of
C
N
H
Fe
–
Cr
–
II
C10H10N6O2
L1
–
158a
220
White [246.2]
48.69
48.73
51.07
51.12
54.92
54.99
58.44
58.50
47.00
47.02
58.81
58.86
55.88
55.92
59.24
59.29
56.25
56.29
59.61
59.65
34.08
34.11
32.50
32.53
19.71
19.74
18.15
18.20
16.84
16.88
18.29
18.31
19.29
19.33
17.81
17.85
19.41
19.46
17.92
17.96
4.04
4.06
3.85
3.87
4.04
4.05
3.73
3.74
3.44
3.47
3.74
3.76
3.96
3.97
3.64
3.67
3.98
4.00
3.66
3.69
III
IV
V
C11H10N6O2
–
White [258.2]
–
–
–
–
L2
C26H23N8O4Fe
1.88
1.85
3.45
3.52
1.89
1.86
3.61
3.41
220a
290a
291a
291a
252a
337a
330a
304a
D. brown [567.3]
Red [615.4]
9.84
9.84
9.06
9.07
–
L1FeSalen
C
30H23N8O4Fe
L1FeSalophen
26H23N8O4Cr
L1CrSalen
30H23N8O4Cr
L1CrSalophen
27H23N8O4Fe
L2FeSalen
31H23N8O4Fe
L2FeSalophen
27H23N8O4Cr
L2CrSalen
31H23N8O4Cr
L2CrSalophen
VI
VII
VIII
IX
X
C
D. green [663.5]
Brown-green [611.6]
D. brown [579.4]
Red [627.4]
7.81
7.84
8.48
8.50
–
C
–
C
9.62
9.64
8.88
8.90
–
C
–
C
Green [575.5]
9.01
9.03
8.32
8.34
XI
C
D. green [623.5]
–
a
Decomposition
Preparation of L2FeSalen(VIII), L2FeSalophen(IX),
L2CrSalen(X) and L2CrSalophen(XI) complexes
Results and discussion
The target ligands were synthesized in one step from mel-
amine. The conversion of melamine into mono-substituted-
melamine derivatives was accomplished in more than 70%
yield. The characterization of both of the ligands 2-(3,4-
dihydroxybenzimino)-4,6-diamino-1,3,5-triazine L1 (II)
and 2-(4-carboxybenzimino)-4,6-diamino-1,3,5-triazine L2
A solution of L2 (0.52 g, 2.0 mmol) and [Fe(salen)]2O or
[Fe(salophen)]2O or [Cr(salen)]2O or [Cr(salophen)]2O in
100 mL of absolute ethanol were refluxed for 3 h. The
mixture was allowed to cool down to room temperature.
Then, the mixture was filtered and dried in vacuum. Yield:
81% (0.94 g), 80% (1.00 g), 65% (0.75 g), 62% (0.78 g)
for VIII, IX, X and XI, respectively.The characterization
data for VIII, IX, X and XI are given in Tables 2 and 3.
1
(III) was accomplished by elemental analyses, H NMR,
FT-IR and mass spectral data [36] (Scheme 1; Tables 1, 2,
3). Both of the ligands are soluble in common organic
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Table 3 Characteristic FT-IR bands (cm-1) of complexes in KBr pellets
No
II
Compounds
C=N
C–N
1119
C–Har
3130
C–Hal
2825
O–H
COph
1277
C=O
–
COO
–
N–Hst
C10H10N6O2
L1
1588a
1654b
1607a
1654b
1580a
1670–1619b
1542c
1386w
3470s
–
3333
3419
3344
3427
3420
3468
III
IV
C
11H10N6O2
1128
1122
3128
3131
2858
–
1654
–
1394
–
L2
C
26H23N8O4Fe
2940
2972
1380w
3326s
1254
1288
L1FeSalen
V
C30H23N8O4Fe
L1FeSalophen
1579a
1605–1657b
1537c
1571a
1647b
1543c
1607a
1651b
1549c
1599a
1646–1631b
1543c
1580a
1607–1653b
1535c
1636a,b
1542c
1595a
1115
1118
1114
1207
1125
3130
3131
3120
3130
3132
2828
1371w
3404s
1281
1300
–
–
3420
3420
VI
C26H23N8O4Cr
L1CrSalen
2938
2976
3219
3344
1289
1286
–
–
–
VII
VIII
IX
C30H23N8O4Cr
L1CrSalophen
2828
1397w
–
–
3337
3419
C27H23N8O4Fe
L2FeSalen
2857
2935
–
–
1698
1695
1386
1379
3344
3378
3343
C31H23N8O4Fe
L2FeSalophen
2859
–
X
C27H23N8O4Cr
L2CrSalen
1117
1128
3131
3120
2813
2931
2857
–
–
–
–
1684
1695
1372
1378
XI
C
31H23N8O4Cr
3335
3420
L2CrSalophen
1618b
1547c
O-
Scheme 1 Synthetic routes for
the preparation of ligands II and
III
OH
OH
+H3N
N
O
O-
N
N
N
N
II
Benzene, -H2O
H2N
N
NH2
+H3N
O
I
N
N
+H3N
N
OH
O
O
NH2
N
N
O-
Benzene, -H2O
III
+H3N
solvents. Synthetic strategy was adopted in preparing a
single substitute mononuclear iminocatechol and/or imi-
nocarboxylate that could be used in a complex formation as
a ‘‘ligand’’ and contain a potential donor group capable of
coordinating with another ligand. Previously, we chose
[Fe(salen)]2O, [Fe(salophen)]2O, [Cr(salen)]2O and
[Cr(salophen)]2O as ‘‘ligand complex’’ [37]. These
complexes are the first examples of single substitute
mononuclear complexes bridged to the iron/chromium
centers by carboxylate anions and catechol group. Other
examples of complexes bridged to the iron centers by cat-
echol group were published in 2008 by Uysal et al. [38].
Other examples of complexes bridged to the iron/chromium
centers by carboxylate [16] and catechol [17] groups were
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169
1
Fig. 1 The H-NMR spectra of
2-(3,4-dihydroxybenzimino)-
4,6-diamino-1,3,5-triazine (a),
1
the H-NMR spectra (D2O
exchange) of 2-(3,4-
dihydroxybenzimino)-4,6-
diamino-1,3,5-triazine (b)
1
Fig. 2 The H-NMR spectra of
2-(4-carboxy benzimino)-4,6-
diamino-1,3,5-triazine (a), the
1H-NMR spectra D2O exchange
of 2-(4-carboxybenzimino)-4,6-
diamino-1,3,5-triazine (b)
published in 2009 by Uysal and Uc¸an. All compounds are
stable at room temperature in the solid state. They are
insoluble in water but, soluble in organic solvents such as
ethylacetate, DMSO and DMF. The results of the elemental
analyses, given in Table 2 are in a good harmony with the
structures suggested for the ligands and their complexes.
The results show that all complexes are mononuclear.
spectra (Figs. 1a, 2a) of both ligands also confirmed their
structures by showing a singlet for a single proton which
corresponds to –N=CH– groups at 9.70 and 10.10 ppm for
II and III respectively [16, 17, 39]. Besides this, in case of
II monosubstitution could be visualized through a singlet at
1
6.06 and 6.36 ppm for two –1NH3 groups in the H-NMR
spectra of II and III respectively. This was supported by
the deuterium-exchanged 1H-NMR spectra showing the
disappearance of signals at 6.06 and 6.36 ppm for two
1
In order to identify the structure of II and III, the H-
NMR spectra were recorded in DMSO-d6. 1H-NMR
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Fig. 3 The single substitute
[Fe(salen/salophen)] and
[Cr(salen/salophen)] complexes
of L1 and L2
H2N
O
M
O
N
N
N
H
N
b
N
O
R
1/2
O
II
+
O
N
2
a
H2N
N
M
O
R
N
O
c
IV : R = -CH2CH2- ; M = Fe(III)
: R = ; M = Fe(III)
V
VI :R = -CH2CH2- ; M = Cr(III)
VII :R =
; M = Cr(III)
H2N
N
O
N
N
O
N
N
b
N
O
III
1/2
R
M
O
O
+
M
O
2
a
R
N
H2N
O
N
c
VIII : R = -CH2CH2- ; M = Fe(III)
IX : R = ; M = Fe(III)
X
:R = -CH2CH2- ; M = Cr(III)
XI :R = ; M = Cr(III)
–1NH3 and appearance of new peaks at 3.90 and 3.76 ppm
for –NH2 groups of both the ligands respectively (Fig. 1b,
2b). Because the deuterium-exchangeable protons of phe-
nolic-OH groups could migrate to –NH2 groups, forming
two equivalent –?NH3 groups after the intramolecular
conversion, the signals disappeared at 3.90 ppm for –NH2
the IR spectra of IV–VII, whereas they had been observed
at 1,277 cm-1 for L1. It has been interpreted that a
downward shift of 12–10 cm-1 for phenolic C–O stretch-
ing vibration in the complexes indicates coordination
through the oxygen atoms. A downward shift from 1,560–
1,567 cm-1 for C=N (c) to 1,543–1,537 cm-1 also indi-
cated that capped coordination was formed [15–17, 34, 38–
42]. The FT-IR spectra of IV–VII bands observed between
3,468 and 3,337 cm-1 was obviously assigned to the pres-
ence of the two NH2 groups on the main structure. The bands
at 1,698–1,684 cm-1 for complexes VIII–XI were assigned
to C=O groups due to the coordination of Fe(salen), Fe(sa-
lophen), Cr(salen) and Cr(salophen) to COO group. Fur-
thermore, the bands at 1,386–1,372 cm-1 were assigned to
COO- ions of those complexes [15, 16, 34]. In the FT-IR
spectra of complexes VIII–XI, two bands were obviously
observed between 3,420 and 3,335 cm-1 assigned to the
presence of the two NH2 groups on the main structure. In the
single substitute mononuclear complexes, the bands in the
558–532 and 466–483 cm-1 ranges can be attributed to the
M–N and M–O stretching modes [39].
1
and reappeared at 6.06 ppm for –1NH3 in the H-NMR
spectra of II (Fig. 1a). Likewise, because the deuterium-
exchangeable protons of carboxylic-OH groups could
migrate to –NH2 groups forming –?NH3 groups after the
intramolecular conversion, the signals disappeared at
3.76 ppm for –NH2 and reappeared at 6.36 ppm for
–1NH3 in the 1H-NMR spectra of III (Fig. 2a). If the
linkage had come true as three substitutes, the phenolic-OH
protons couldn’t have migrated (Fig. 3).
IR bands at 1,579–1,636 cm-1 were assigned to triazine
ring C=N (a) stretching vibrations for complexes IV–XI.
Bands at 1,653–1,605 cm-1 for complex IV–XI were
assigned to C=N (b) stretching vibrations, and bands at
1,535–1,549 cm-1 were assigned to C=N (c) stretching
vibrations for complexes IV–XI, respectively, whereas
C=N (c) stretching vibration bands were found at 1,560–
1,567 cm-1 for [Fe(salen)]2O, [Fe(salophen)]2O, [Cr(sa-
len)]2O and [Cr(salophen)]2O complexes [15–17, 38, 40,
41]. Aromatic stretching vibrations are between 1,481 and
1,433 cm-1 for IV–VII. Phenolic C–O stretching vibra-
tions at 1,254–1,300 cm-1 have clearly been observed at
The magnetic moments of the complexes given in
Table 2 were measured at room temperature. On the basis
of spectral evidence, the Fe(III) and Cr(III) complexes have
mononuclear structures, in which the Fe(III) and Cr(III)
cations have an approximately octahedral environment.
The magnetic behaviour of Fe(III) and Cr(III) complexes is
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J Incl Phenom Macrocycl Chem (2010) 68:165–173
171
in accord with the proposed mononuclear structures. The
magnetic moment of mononuclear complexes which were
composed of [Fe(salen)]2O, [Fe(salophen)]2O, [Cr(sa-
len)]2O and [Cr(salophen)]2O of (L1 and L2) shows para-
magnetic properties with a magnetic susceptibility value:
The magnetic moments of all Fe(III) complexes are
between 1.85 and 1.89 B.M., and all Cr(III) complexes are
between 3.41 and 3.61 B.M. [15–17, 35, 38, 42, 43]. It is
seen that the Fe(salen), Fe(salophen), Cr(salen) and
Cr(salophen) containing compounds are represented by the
electronic structure of t52geg0 and t23geg0. The magnetic data
for the FeSalen, FeSalophen, CrSalen and CrSalophen
capped complexes of L1 and L2 show good harmony with
the d5 and d3 metal ions in an octahedral structure. This
result is supported by the results of the elemental analyses,
suggesting that these mononuclear complexes have also an
octahedral structure [15–17, 33, 35, 38, 42, 43].
be 5.65% and measured experimentally to be 7.46%. When
the sample was heated up to 290.79 °C, it was calculated
theoretically and measured experimentally that the weight
loss was 43.29 and 35.35%, respectively.
In TGA-DTA diagram (Fig. 5) of [Fe(salen)] capped
complexes of 2-(4-carboxybenzimino)-4,6-diamino-1,3,5-
triazine (VIII), the first decomposition step was started at
251.99 °C. Although the weight loss was theoretically
calculated to be 9.64%, it was experimentally observed to
be 8.01%. While CO2 gases left the medium, [Fe(salen)]
group also left the main structure. At the second decom-
position step, C2H2 and N2 gasses went away from the
main structure at 392 °C. Although the weight loss was
theoretically calculated to be 11.86%, it was experimen-
tally observed to be 13.44%. At the third decomposition
step, C6H6 left the main structure at 565 °C. Although the
weight loss was theoretically calculated to be 27.9%, it was
experimentally observed to be 35.1%.
Samples (VI, VIII and XI) chosen from all the com-
plexes were thermally investigated. It is well known that
there is a strong relation between temperature range for the
dehydration process and the binding mode of the water
molecules to the respective metal complexes [44]. That the
elimination of water took place in a single-step process
attributed to the release of the hydrated water molecules (in
the range of 60–120 °C) [15–17, 38, 42, 45]. Thermal
decomposition of the anhydrous [Fe/Cr(salen)] and [Fe/
Cr(salophen)] complexes left the ligands L1 and L2 started in
the range of 290–392 °C and completed in the range of 565–
650 °C. The final decomposition products were metal oxi-
des and triazine ring. The observed weight losses for com-
plexes were in good harmony with the calculated values.
In TGA-DTA diagram (Fig. 4) of [Cr(salen)] capped
complexes of 2-(3,4-dihydroxybenzimino)-4,6-diamino-
1,3,5-triazine (VI), decomposition of [Cr(salen)] capped
complexes of L1 was determined in two steps. At the ther-
mal decomposition steps, H2O firstly left the main structure
at 90.75 °C and weight loss was theoretically calculated to
In TGA-DTA diagram (Fig. 6) of [Cr(salophen)] capped
complexes of 2-(4-carboxybenzimino)-4,6-diamino-1,3,5-
triazine (XI), while CO2 gases left the medium,
Fig. 5 Thermal decomposition diagram of L2FeSalen (VIII)
Fig. 4 Thermal decomposition diagram of L1CrSalen (VI)
Fig. 6 Thermal decomposition diagram of L2CrSalophen (XI)
123

172
J Incl Phenom Macrocycl Chem (2010) 68:165–173
4. Hoog, P., Gamez, P., Lu¨ken, M., Roubeau, O., Krebs, B.,
Reedijk, J.: Hexanuclear copper(II) complex of
[Cr(salophen)] the group was also left the main structure at
93.7 °C. At first decomposition when CO2 was leaving,
weight loss was both theoretically calculated and experi-
mentally observed to be 7.0%. The decomposition of the
[Cr(salophen)] group also occured at 303 °C at the second
step, and the weight loss was theoretically calculated to be
53.6% and experimentally measured to be 56.0%. The third
decomposition was completed at around 650 °C. It was
theoretically obtained 14.0% and experimentally 12.0%,
indicating the loss of C6H6 and N2 gasses from the
medium.
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V.N.: Crystal and molecular structure and magnetic anisotropy of
From the investigation of LC–MS spectra of all com-
pounds, it was seen that the molecular weights of ligands
and complexes were in good harmony with the intensively
observed values in LC–MS spectras (Table 2).
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Conclusion
In this study, novel single substitute and melamine cored
Schiff bases ‘‘2-(3,4-dihydroxybenzimino)-4,6-diamino-
1,3,5-triazine and 2-(4-carboxybenzimino)-4,6-diamino-
1,3,5-triazine’’ were synthesized. Synthetic strategy for
preparing mononuclear complexes uses a complex as a
‘‘ligand’’ that contains a potential donor group capable of
coordinating with the other ligand. We have chosen
[Fe(salen)]2O, [Fe(salophen)]2O, [Cr(salen)]2O and
[Cr(salophen)]2O as ‘‘ligand complexes’’ because they can
coordinate with the other ligand. These complexes are the
examples of single substitute mononuclear complexes
bridged by carboxylate anions and catechol group to iron
and chromium centers. Their structures were characterized
13. Kopel, P., Sindelar, Z., Klicka, R.: Complexes of iron(III) salen
and saloph Schiff bases with bridging dicarboxylic and tricar-
boxylic acids. Transit. Met. Chem. 23, 139 (1998). doi:10.1023/
A:1006990925318
14. Wollmann, R.G., Hendrickson, D.N.: Reaction of.mu.-oxo-
bridged iron(III) complexes with organic acids: a characterization
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10.1021/ic50182a026
1
by elemental analysis, H NMR, FT-IR spectrscopy, LC–
MS, thermal analyses and magnetic susceptibility mea-
surements. The magnetic data for the single substitute
mononuclear melamine complexes show good harmony
with the d5 and d3 metal ions in an octahedral structure.
_
15. Koc¸, Z.E., Uc¸an, H.I.: Complexes of iron(III) salen and saloph
Acknowledgment The authors would like to acknowledge the
Scientific Research Projects (BAP) of Selcuk University for sup-
porting this study through a grant: 2005/5201005.
Schiff bases with bridging 2,4,6-tris(2,5-dicarboxyphenylimino-
4-formylphenoxy)-1,3,5-triazine and 2,4,6-tris(4-carboxyphe-
nylimino-40-formylphenoxy)-1,3,5-triazine. Transit. Met. Chem.
32, 597–602 (2007). doi:10.1007/s11243-007-0213-7
_
16. Uysal, S¸., Uc¸an, H.I.: The synthesis and characterization of
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