Complexes of iron(III) and chromium(III) salen and salophen Schiff bases with bridging 1,3,5-triazine derived multidirectional ligands

Article abstract of DOI:10.1002/jhet.577

Figure represented. A new synthetic route for preparing multidirectional ligands was developed by using 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride) as core. The reaction included the selective substitutions of 4-aminobenzoic acid onto three chlorides of the triazine ring via a stepwise manner at 1:1, 1:2, or 1:3 equiv. and 0, 25, 130°C, respectively. An efficient synthesis of a novel class of "multidirectional ligands" has been developed based on high-yielding chloride substitutions of 2,4,6-trichloro-1,3,5-triazine by amines. Sixteen new mono-, di-, tri-, and tetra-nuclear Fe(III) and Cr(III) complexes involving tetradenta Schiff bases N,N′-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophenH₂) with two new 1,3,5-triazine derived multidirectional ligands were synthesized and characterized by means of elemental analysis, ¹H NMR, FT-IR spectroscopy, LC-MS analysis, AAS, thermal analysis, and magnetic susceptibility measurements. The complexes were also characterized as low-spin distorted octahedral Fe(III) and Cr(III) bridged by carboxylic acids. It was understood that the [{Fe(salen)/(salophen)}₂O] and [{Cr(salen)/(salophen)} ₂O] containing compounds could be represented by the electronic structure of t_2g⁵e_g⁰ and t _2g³e_g⁰.

Full text of DOI:10.1002/jhet.577

July 2011
Complexes of Iron(III) and Chromium(III) Salen and Salophen
Schiff Bases with Bridging 1,3,5-Triazine Derived
Multidirectional Ligands
769
Ziya Erdem Koc¸*
Department of Chemistry, Faculty of Science, Selcuk University, 42075-Konya, Turkiye
*E-mail: zerdemkoc@gmail.com
Received April 28, 2010
DOI 10.1002/jhet.577
Published online 1 April 2011 in Wiley Online Library (wileyonlinelibrary.com).
A new synthetic route for preparing multidirectional ligands was developed by using 2,4,6-trichloro-
1,3,5-triazine (cyanuric chloride) as core. The reaction included the selective substitutions of 4-amino-
benzoic acid onto three chlorides of the triazine ring via a stepwise manner at 1:1, 1:2, or 1:3 equiv.
and 0, 25, 130ꢀC, respectively. An efficient synthesis of a novel class of ‘‘multidirectional ligands’’ has
been developed based on high-yielding chloride substitutions of 2,4,6-trichloro-1,3,5-triazine by amines.
Sixteen new mono-, di-, tri-, and tetra-nuclear Fe(III) and Cr(III) complexes involving tetradenta Schiff
bases N,N0-bis(salicylidene)ethylenediamine-(salenH2) or bis(salicylidene)-o-phenylenediamine-(salo-
phenH2) with two new 1,3,5-triazine derived multidirectional ligands were synthesized and characterized
1
by means of elemental analysis, H NMR, FT-IR spectroscopy, LC-MS analysis, AAS, thermal analysis,
and magnetic susceptibility measurements. The complexes were also characterized as low-spin distorted
octahedral Fe(III) and Cr(III) bridged by carboxylic acids. It was understood that the [{Fe(salen)/(salo-
phen)}2O] and [{Cr(salen)/(salophen)}2O] containing compounds could be represented by the electronic
structure of t52geg0 and t23ge0g.
J. Heterocyclic Chem., 48, 769 (2011).
INTRODUCTION
other hand, it has been demonstrated that the 1,3,5-tria-
zine ring is a suitable structural element to be incorpo-
rated into thermotropic liquid crystals. Thus, aromatic
esters involving a 1,3,5-triazine moiety have been found
to exhibit calamitic mesophases [3].
The design and synthesis of supramolecular polynu-
clear metal complexes have been an area of rapid
growth for the past 20 years. During the last decade, a
remarkable development in the preparation of self-
assembled architecture through metal ion coordination
has been observed. The motivation behind much of the
studies related with polynuclear metal complexes has
been provided by the prospect of producing a wide
range of purpose-built materials with predetermined
structures and potential applications in separation, gas
storage, molecular recognition, and catalysis [1]. The
preparation of polymetallic complexes can be achieved
using rationally designed polydentate ligands [2]. On the
Sophisticated s-triazine derivatives can be easily pre-
pared from the cheap and readily available cyanuric
chloride (C3N3Cl3), 2,4,6-trichloro-1,3,5-triazine (1)
[4,5]. Cyanuric chloride is definitely an excellent start-
ing compound for the straightforward preparation of
highly structured multitopic molecules. Indeed, each
chloride atom of 2,4,6-trichloro-1,3,5-triazine can be
substituted by any nucleophilic reactant (Fig. 1) [2]. The
first substitution is exothermic. Therefore, the tempera-
ture of the reaction mixture has to be maintained to
C
V
2011 HeteroCorporation

770
Z. E. Koc¸
Vol 48
trichloro-1,3,5-triazine with 1:1, 1:2, or 1:3 equiv and
0ꢀC, 25ꢀC, or 130ꢀC of 4-aminobenzoic acid gave the
desired ‘‘multidirectional ligands,’’ respectively [12–26].
The aim of this work was to make other bridges and try
to as certain their influence on the magnetic behavior of
the prepared complexes. As a future plan of this study,
novel s-triazine Schiff base derivatives and some of
their new multinuclear systems will be formed by the
1,3,5-tricarboxylato bridge.
EXPERIMENTAL
All chemicals were purchased from Aldrich. The linking
agent, 2,4,6-trichloro-1,3,5-triazine (abbreviated as cyanuric
chloride, mp 145–146ꢀC), was obtained from Aldrich. Cyanu-
ric chloride was purified by recrystallizations from pure petro-
leum ether (60–90ꢀC) [24].
Figure 1. Preparation of polyfunctional s-triazine derivatives taking
advantage of the differential reactivity of 2,4,6-trichloro-1,3,5-triazines.
Elemental analyses were performed with Carlo Erba 1106
elemental analyzer. The IR spectra were recorded using KBr
discs (4000–440 cmꢁ1) with Perkin Elmer 1600 series FT-IR
spectrophotometer. Metal contents in complexes were deter-
mined using Unicam 929 AAS spectrometer. Mass spectra of
the compounds were obtained registered on with Varian MAT
711 spectrometer. The 1H NMR spectra in d6-DMSO was
obtained using a Bruker 200 MHz spectrometer. MMM-Med-
center and Einrichtungen GmbH Vacucell 22 were used as
Vacuum Cabinets. Melting points were measured using a
Buchi SMP-20 melting point apparatus. Arex Velp Sci. used
as Heating Magnetic stirrer which is equipped with a contact
Vetex thermostat connection for direct control of the tempera-
ture of the stirred liquid. The thermal analysis was performed
with Shimadzu DTA 50 and TG 50 H models using 10 mg
samples. The DTA and TG curves were obtained recorded at
the heating rate of 10ꢀC minꢁ1. In all cases, the temperature
range between 22 and 750ꢀC was used under dry nitrogen
atmosphere. Magnetic Susceptibilities of metal samples were
determined using a Sheerwood Scientific MX Gouy magnetic
susceptibility apparatus and magnetic measurements were car-
ried out using the Gouy method with Hg[Co(SCN)4] as cali-
0ꢀC. The substitution of the second chloride can be per-
formed at room temperature. Finally, the third position
is functionalized under refiux of the solvent. As a result,
a careful control of the temperature during the substitu-
tion reactions will allow the synthesis of 2,4,6-trisubsti-
tuted-triazines by sequential and very selective addition
of amines, alcohols, thiols, or Grignard reagents (Fig.
1). The yield of each substitution often exceeds 95%,
and the symmetric trisubstituted derivatives can even be
obtained in a one pot synthesis. Various solvents can be
used such as tetrahydrofuran, 1,2-dimethoxy ethane, ace-
tonitrile, and diethyl ether [5].
The magnetochemical properties of the l-oxo-bridged
complexes [{Fe(salen)}2O] [(salenH2 ¼ N,N0-bis(salicy-
lidene) ethylenediamine)] and [{Fe(salophen)}2O] [(sal-
ophenH2 ¼ bis(salicylidene)-2-phenylenediamine)] and
their X-ray studies have widely been presented in the
literature [6]. I have also reported the synthesis and
characterization of 1,3,5-tricarboxylato, dendrimeric-car-
boxylato, single substitute carboxylato, single substitute
catechol, and 1,3,5-tricatechol triazine bridges with
[salenFe(III)], [salophenFe(III)], [salenCr(III)], and [sal-
ophenCr(III)] [7–13].
brant. The effective magnetic moments, leff, per metal atom
pffiffiffiffiffiffi
was calculated from the expression: leff ¼ 2:84 vM TB:M:,
where vM is the molar susceptibility.
Preparation of ligand complexes. [{Fe(salen)/(salophen)}2O]
and [{Cr(salen)/(salophen)}2O] were prepared by adding con-
centrated ammonia solution to stirred hot EtOH solutions of
[Fe(salen)/(salophen)Cl] and [Cr(salen)/(salophen)Cl], respec-
tively, until alkaline [6,27–29].
This article describes the preparation of rationally
designed bidentate, tetradendate, and multidentade
ligands. The relatively simple synthetic pathway to these
multidirectional ligands is based on nucleophilic addi-
tion of 4-aminobenzoic acid to 2,4,6-trichloro-1,3,5-tria-
zine. This method is the first demonstration used for the
synthesis of 1,3,5-triazine-derived ‘‘multidirectional
ligands’’ and its Schiff bases complexes of iron(III) or
chromium(III) due to the direct bond between ACOOH
group [7–26]. Therefore, I have reported here that 1,3,5-
triazine-derived ‘‘multidirectional ligands’’ and its Schiff
bases complexes of iron(III) or chromium(III) have been
synthesized to be a new template. The reaction of 2,4,6-
Synthesis of 2,4-dichloro-6-(4-carboxyanilino)-1,3,5-tria-
zine (2). Previously, this compound was synthesized due to
procedure mentioned in the study of Ragno et al. Typical pro-
cedures for the amination of cyanuric chloride (1) have been
described by using 4-aminobenzoic acid as an example [30]. A
solution of 4-aminobenzoic acid (1.37 g, 10 mmol) in acetone
(50 mL) and deionized water (50 mL) was added dropwise to
a cyanuric chloride (1) suspension made by pouring slurry cya-
nuric chloride (1) (1.84 g, 10 mmol) in acetone (50 mL) into
0–5ꢀC deionised water (50 mL), with stirring, in an ice bath
[31]. NaHCO3 (2.10 g, 25 mmol) in water (50 mL) was added
to maintain the pH between 6.0 and 7.0 during the reaction.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

July 2011
Complexes of Iron(III) and Chromium(III) Salen and Salophen Schiff Bases
with Bridging 1,3,5-Triazine Derived Multidirectional Ligands
771
After 3 h, when no cyanuric chloride (1) could be detected by
TLC (Thin Layer Chromatography) (solvent system: hexane–
ethyl acetate, 1:4, v/v). At these stages, the Fujiwara Test [24]
for dichlorotriazine was positive. The acetone was removed by
vacuum, and the residue was suspended in water (100 mL).
The precipitate was removed by filtration and the water phase
extracted three times by dichloromethane. The product was
then precipitated out of solution by acidifying the water phase
to pH 4.0 with (5M) hydrochloric acid. A white powder solid
product was collected by filtration and was washed with cold
washed with cold water (3 ꢂ 100 mL) to remove the sodium
bicarbonate [32,33]. 1H NMR (d6-DMSO) d 12.93 (br, 3H,
OH), 11.94 (s, 3H, NH), 7.73–7.71 (d, 6H), 8.83–8.80 (d, 6H).
Synthesis of N,N0-{bis[4,6-(4-carboxyanilino)]-1,3,5-triazine}-
ethylenediamine (5). To a stirred solution of (3) (2.31 g, 6
mmol) and N-ethyldiisopropylamine (DIPEA) (0.78 g,
6
mmol) in acetone (50 mL), ethylendiamine (0.20 mL, 3 mmol)
was added and NaHCO3 (0.42 g, 5 mmol) in water (100 mL)
saturated by N2 was added dropwise to the mixture for 1 h.
This mixture was heated to 80ꢀC for 48 h. The acetone was
removed by vacuo, and the residue was suspended in water
(100 mL). The precipitate was removed by filtration and the
water phase extracted three times with dichloromethane. The
product was then precipitated out of solution by acidifying the
water phase to pH 4.0 with (5M) hydrochloric acid. The pre-
cipitate was filtered under reduced pressure, washed with ace-
tone (3 ꢂ 20 mL) [2]. LC-MS data for 5 m/z: 758 6 2, FT-
IR(cmꢁ1) 3315–3295 (NH), 3291 (OH), 2864 (CH), 2860
(CH2), 1710 (C¼¼O), 1560 (C¼¼N triazine). 1H NMR (d6-
DMSO) d 13.05 (br, 4H, OH), 9.93 (s, 4H, NH), 7.49 (s, 2H,
NH), 7.84–7.78 (d, 4H, j ¼ 0.91 Hz), 8.23–8.17 (d, 4H, j ¼
0.92 Hz), 3.52 (s, 4H, CH2).
Synthesis of [H2Lsalen/salophen]Fe(III) or [H2Lsalen/sal-
ophen]Cr(III) complexes. [{Fe(salen)/(salophen)}2O] (0.33,
0.66, 0.99, 1.32 g/0.5, 1, 1.5, 2 mmol – 0.38, 0.76, 1.14, 1.5 g/
0.5, 1, 1.5, 2 mmol) or [{Cr(salen)/(salophen)}2O] (0.33, 0.65,
0.98, 1.3 g / 0.5, 1, 1.5, 2 mmol – 0.36, 0.75, 1.13, 1.5 g / 0.5,
1, 1.5, 2 mmol) were suspended in hot EtOH (50 mL) and a
solution of (2), (3), (4), (5) (0.29, 0.39, 0.49, 0.76 g, 1 mmol)
in EtOH was added by stirring, respectively. The reaction mix-
ture was boiled under reflux for 4h, and the solid formed was
dried under vacuum cabinets (50ꢀC). (2, 3/a, b, c, d) FT-IR
(cmꢁ1) 3427 (NH), 2895 (CH), 1550 (C¼¼N triazine), 1385
(COOꢁ), 840 (CACl), 538 (M-N), 468 (M-O). (4/a, b, c, d)
FT-IR (cmꢁ1) 3430 (NH), 2880 (CH), 1556 (C¼¼N triazine),
1383 (COOꢁ), 619 (M-N), 495 (M-O). (5/a, b, c, d) FT-IR
(cmꢁ1) 3433 (NH), 2873 (CH2), 1553 (C¼¼N triazine), 1398
(COOꢁ), 597 (M-N), 482 (M-O).
1
water (3 ꢂ 100 mL) and acetone [31]. H NMR (d6-DMSO) d
12.80 (br, 1H, OH), 11.37 (s, 1H, NH), 7.70–7.67 (d, 2H),
7.95–7.78 (d, 2H).
Synthesis of 2-chloro-4,6-(4-carboxyanilino)-1,3,5-triazine
(3). To stirred cyanuric chloride (1) (1.84 g, 10 mmol), dis-
solved in acetone (50 mL), was added dropwise a solution of
4-aminobenzoic acid (1.37 g, 10 mmol) in acetone (50 mL)
and deionized water (50 mL) and NaHCO3 (2.10 g, 25 mmol)
in water (50 mL) saturated by N2 at 0–5ꢀC. The reaction mix-
ture was stirred vigorously for 3 h at 0–5ꢀC and for 2 h at 15–
20ꢀC. When no cyanuric chloride could be detected by TLC
(solvent system: hexane–ethyl acetate, 1:4, v/v). At these
stages, the Fujiwara test [24] for dichlorotriazine was positive.
The temperature was allowed to increase to 25ꢀC and main-
tained for 2 h at 25–30ꢀC. When the test was negative, a solu-
tion of 4-aminobenzoic acid (1.37 g, 10 mmol) and NaHCO3
(2.10 g, 25 mmol) in water (100 mL) saturated by N2 was
added dropwise to the mixture for 1 h. After the reaction mix-
ture was stirred for 2 h at 35–40ꢀC, the temperature was
decreased to 0–5ꢀC. The acetone was removed in vacuum, and
the residue was suspended in water (100 mL). The precipitate
was removed by filtration, and the water phase extracted three
times with dichloromethane. Then, the product was precipi-
tated out of solution by acidifying the water phase to pH 4.0
with (5M) hydrochloric acid. A dark grey powder solid product
was collected by filtration and was washed with cold water (3
ꢂ 100 mL) to remove the sodium bicarbonate [31]. The crude
product, 2-chloro-4,6-(4-carboxyanilino)-1,3,5-triazine (3) was
purified by chromatography (solvent system: hexane–ethyl ace-
tate, 1:4, hexane v/v) to afford a dark grey powder solid prod-
uct dried in a vacuum cabinets (50ꢀC) and stored in a desicca-
tor over CaCl2 that decomposes at 348ꢀC in a yield of 65%;
LC-MS data for 3 m/z: 386 6 2, FT-IR(cmꢁ1) 3379 (NH),
3358 (OH), 2809 (CH), 1702 (C¼¼O), 1564 (C¼¼N triazine).
1H NMR (d6-DMSO) d 12.87 (br, 2H, OH), 11.53 (s, 2H,
NH), 7.23–7.19 (d, 4H, j ¼ 0.92 Hz), 8.44–8.40 (d, 4H, j ¼
0.91 Hz).
Different method for the synthesis of complexes (5a, 5b,
5c, 5d). To a stirred solution of (3a, 3b, 3c, 3d) (1.03, 1.13,
1.02, 1.12 g, 1 mmol) and N-ethyldiisopropylamine (DIPEA)
(0.26 g, 2 mmol) in acetone (50 mL), ethylendiamine (0.14
mL, 2 mmol) was added dropwise to the mixture. This mixture
was reflux for 48 h.
RESULTS AND DISCUSSION
Synthesis of 2,4,6-(4-carboxyanilino)-1,3,5-triazine
(4). Cyanuric chloride (1) (1.84 g, 10 mmol) were dissolved
in acetone (75 mL). NaHCO3 (6.30 g, 75 mmol) in water (100
mL) saturated by N2 was added and three necked round bot-
tomed flask was cooled 0ꢀC. 4-aminobenzoic acid (4.11 g, 30
mmol) was added portionwise. After the completion of the
addition, the suspension mixture was warmed to room temper-
ature and then heated under reflux for 48 h. The acetone was
removed by vacuo and the residue was suspended in water
(100 mL). The precipitate was removed by filtration and the
water phase extracted three times with dichloromethane. The
product was then precipitated out of solution by acidifying
the water phase to pH 4 with (5M) hydrochloric acid. Brown
powder solid product was collected by filtration and was
‘‘Multidirectional ligands’’ bearing 1,3,5-triazine-deriv-
ative were prepared by the reaction of cyanuric chloride
(1) with 4-aminobenzoic acid (Scheme 1). The first and
second step have consisted of preparing 2,4-dichloro-6-(4-
carboxyanilino)-1,3,5-triazine (2), 2-chloro-4,6-(4-carbox-
yanilino)-1,3,5-triazine (3), 2,4,6-(4-carboxyanilino)-1,3,5-
triazine (4), and N,N0-{bis[4,6-(4-carboxyanilino)]-1,3,5-tri-
azine}ethylenediamine (5) by substitution of only chloride
atoms of cyanuric chloride, which has been characterized
by their elemental analysis, LC-MS analysis, thermal
1
analysis, H NMR, FT-IR, AAS, and magnetic suscepti-
bility measurements where replacement of the chloro by
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

772
Z. E. Koc¸
Vol 48
Scheme 1. Reactions of cyanuric chloride with 4-aminobenzoic acid.
the amine group causes lowering of the energy of the
NH2 stretch in the FT-IR spectrum, and a shift to higher
azine to amine at 1:1, 1:2, 1:3 equiv. Two 2-chloro-4,6-(4-
carboxyanilino)-1,3,5-triazine (3) units were then bridged
using ethylenediamine as linker where each amino group
substituted the third chloride atom (Scheme 1).
1
field of the NH proton signal in the H NMR spectrum.
All the ligands are soluble in common organic solvents.
The optimization of reaction temperatures and the se-
lectivity of amine substitution on the three chlorides of
cyanuric chloride were studied by using 4-aminobenzoic
acid as the starting amine. This 4-aminobenzoic acid has
only a single ANH2 functionality for substitution on the
triazine ring. To validate the selectivity mode for the sub-
stitutions of three chlorides, the reactions were carried out
with different reaction temperatures and molar ratios of tri-
The results indicate that the reaction temperature is
important parameter in controlling the amine substitu-
tion. Under the reaction temperature of 0–5ꢀC, the first
chloride in the triazine ring was selectively substituted
by first equiv of amine to produce a sole product. The
substitution of second equiv. amines on the second chlo-
ride occurred at 25ꢀC. Only at high temperature such as
130ꢀC does the third chloride in the triazine ring was
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

July 2011
Complexes of Iron(III) and Chromium(III) Salen and Salophen Schiff Bases
with Bridging 1,3,5-Triazine Derived Multidirectional Ligands
773
Table 1
Some physical properties, molecular weight ([g/mol]) data, effective magnetic moments,
elemental analyses, and AAS analyses of the ligands and complexes.
Anal. Found Calc. (%)
Compound
leff (296 K) B.M.
M.p. (ꢀ)
348a
Yield (%)
80
Color MW (g/mol)
C
H
N
Fe
–
Cr
–
C17H12ClN5O4 (3)
–
Dark grey (387.77)
52.88
52.93
56.95
56.99
51.46
51.51
54.98
55.07
51.78
51.84
55.35
55.40
57.19
57.25
60.85
60.90
57.62
57.68
61.26
61.32
59.58
59.65
63.25
63.30
60.08
60.13
63.70
63.76
58.72
58.78
62.35
62.33
59.18
59.23
62.70
62.76
3.07
3.14
3.92
3.99
3.10
3.16
3.01
2.93
3.12
3.18
3.88
2.94
3.67
3.73
3.37
3.41
3.77
3.75
3.45
3.43
3.93
3.96
3.57
3.60
4.03
3.99
3.58
3.63
4.01
4.05
3.68
3.70
4.02
4.08
3.68
3.72
18.17
18.15
22.18
22.15
13.82
13.86
12.78
12.85
13.90
13.95
12.94
12.92
12.28
12.26
11.22
11.21
12.36
12.35
11.26
11.29
10.54
11.59
12.48
10.54
11.82
10.85
10.66
10.62
13.69
13.71
12.48
12.53
11.75
13.81
12.58
12.62
C36H30N12O8 (5)
–
263a
293a
282a
285a
288a
295a
298a
290a
291a
320a
325a
318a
315a
322a
328a
316a
319a
83
60
68
65
55
59
68
72
62
67
59
68
72
60
58
51
55
White (758.23)
–
–
–
–
C26H19Cl2N6O4Fe (2a)
C30H19Cl2N6O4Fe (2b)
C26H19Cl2N6O4Cr (2c)
C30H19Cl2N6O4Cr (2d)
C49H38ClN9O8Fe2 (3a)
C57H38ClN9O8Fe2 (3b)
C49H38ClN9O8Cr2 (3c)
C57H38ClN9O8Cr2 (3d)
C72H57N12O12Fe3 (4a)
C84H57N12O12Fe3 (4b)
C72H57N12O12Cr3 (4c)
C84H57N12O12Cr3 (4d)
C100H82N20O16Fe4 (5a)
C116H82N20O16Fe4 (5b)
C100H82N20O16Cr4 (5c)
C116H82N20O16Cr4 (5d)
1.63
1.65
3.62
3.61
1.67
1.62
3.68
3.70
1.78
1.80
3.72
3.75
1.80
1.83
3.77
3.79
Dark brown (606.22)
Dark brown (654.26)
Orange (602.37)
9.17
9.21
8.62
8.54
–
8.58
8.63
8.03
7.99
–
Orange (650.41)
–
Dark brown (1028.02)
Dark brown (1124.11)
Dark brown (1020.33)
Green (1116.41)
10.87
10.86
9.97
9.94
–
–
10.13
10.19
9.30
9.31
–
–
Dark green (1449.83)
Dark green (1593.96)
Green (1438.28)
10.50
11.56
10.47
10.51
–
–
10.67
11.69
9.82
9.86
–
Green (1582.41)
–
Brown (2043.24)
Brown (2235.40)
Green (2027.83)
10.87
10.93
9.92
9.99
–
–
10.21
10.26
9.31
Green (2220.00)
–
9.37
a Decomposition.
reactive for the third equiv. of amine. The reactions,
using deviated temperatures from the optimized temper-
atures, for example, the reaction of 1:3 molar ratio of
triazine/amine at 25ꢀC instead of 130ꢀC gave rise to a
mixture, di-substituted and unreacted starting material
amine, without a trace of tri-substituted product. This
implies the third chloride was not reacted at 25ꢀC [2].
Finally, ‘‘multidirectional ligands’’ (2–5) are described
(Scheme 1). The temperature-controlled reaction of cyanuric
chloride (1) with 4-aminobenzoic acid exclusively led to the
formation of compound (2–5). This chemo selectivity of the
substitutions is due to the difference of nucleophilicity
between an amine and a carboxylate AOH. Sodium bicar-
bonate was used in that case to avoid deprotonation of the
carboxylate AOH group which would have resulted in
mixed N- and/or O-substitution products [2,21,34].
Synthetic strategy for preparing mono-, di-, tri-, and
tetra-nuclear is to use a complex as a ‘‘ligand’’ that
contains a potential donor group capable of coordinating
to another ligand. We have chosen [{Fe(salen/salo-
phen)}2O] and [{Cr(salen/Salophen)}2O] as ‘‘ligand com-
plexes,’’ because they can coordinate to another ligand
[6,27–29]. These complexes are some of the first exam-
ples multidirectional complexes bridged by carboxylate
anions to the iron and chromium centers (Scheme 1).
The results of the elemental analysis, given in Table 1,
are in a good harmony with the structures suggested
for the ligands and their complexes. The results show
that all complexes are multidirectional (Scheme 1). All
complexes are stable at room temperature, and in only
organic solvent such as DMSO, DMF and are insoluble
in water.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

774
Z. E. Koc¸
Vol 48
Table 2
Decomposition steps with the temperature range and weight loss for ligands 3 and 5 and 2(a-b), 3(b-c), 4(c-d), and 5c complexes.
Molecular formula
Temp. range (ꢀ)
Weight loss, found (calc.) (%)
Fragment
C17H12ClN5O4 (3)
C36H30N12O8 (5)
105–120
220–390
94–114
63.24 (63.43)
18.87 (18.96)
07.52 (07.66)
63.72 (63.85)
07.80 (07.91)
43.73 (43.82)
22.23 (22.40)
11.58 (11.69)
47.85 (47.93)
20.68 (20.76)
10.77 (10.83)
55.77 (55.82)
22.12 (24.17)
03.11 (03.15)
51.87 (51.91)
26.69 (26.74)
03.44 (03.49)
54.10 (54.16)
23.83 (25.20)
03.05 (03.12)
59.30 (59.46)
21.27 (22.91)
02.45 (2.84)
02.75 (02.85)
51.18 (51.23)
25.24 (26.79)
CO2, C6H6, H2, N2, Cl2
CO2, C6H6, H2, N2, C2H2
N2, C2H4, CO2, H2, C6H6, Cl2
N2, CO2, H2, C6H6, Cl2
123–145
232–387
130–200
200–315
330–450
127–215
215–320
325–445
130–223
227–285
315–410
125–235
245–318
325–440
110–218
223–320
325–445
120–222
234–295
305–430
137–248
265–305
316–450
C26H19Cl2N6O4Fe (2a)
C30H19Cl2N6O4Fe (2b)
C57H38ClN9O8Fe2 (3b)
C49H38ClN9O8Cr2 (3c)
C72H57N12O12Cr3 (4c)
C84H57N12O12Cr3 (4d)
C100H82N20O16Cr4 (5c)
N2, CO2, H2, C6H6, Cl2
N2, C2H4, CO2, H2, C6H6, Cl2
N2, CO2, C2H4, CO, NH3,H2, C6H6
N2, CO2, CO, NH3,H2, C6H6
N2, C2H4, CO2, H2, C6H6, C2H2
The final thermal decomposition products are metal oxides.
1
To identify the structures of the (2–5), the H NMR
nuclear complexes which were constructed from [{Fe(sa-
len)/(salophen)}2O] and [{Cr(salen)/(salophen)}2O] either
of (2–5) shows paramagnetic property with a magnetic
susceptibility value per atom: 1.83–1.62 B.M. and 3.79–
3.61 B.M., respectively. It is seen that the [{Fe(salen)/(sal-
ophen)}2O] and [{Cr(salen)/(salophen)}2O] containing
compounds are represented by the electronic structure of
t52ge0g and t23geg0. The magnetic data for the [{Fe(salen)/(sal-
ophen)}2O] and [{Cr(salen)/(salophen)}2O] capped com-
plexes show good harmony with the d5 and d3 metal ion
in an octahedral structure. This consequence is supported
by the results of the elemental analysis suggesting that
these complexes have also an octahedral structure [7–
13,27–30].
1
spectra were recorded in DMSO-d6. H NMR spectra were
also in good correlation with the structures of the synthe-
sized compounds. The 1H NMR spectrum signals of
ligands (2–5) at d 12.80–12.87–12.93–13.05 and 11.37–
11.53–11.94–9.93 ppm correspond to the carboxylate
AOH and ANH proton resonances, respectively [30–34].
The vibrations of the NAH, C¼¼N, and C¼¼O of the
free ligands (2–5) are observed at 3315–3379, 1560–
1564, and 1702–1710 cmꢁ1 range, respectively [7]. In
the complexes, that these bands are, however, shifted to
lower frequencies, has indicated that the nitrogen and
oxygen atoms of the ‘‘multidirectional ligands’’ are
coordinated to the ligand complexes. In the ligands, the
bands at 3291–3358 cmꢁ1 can be assigned to the car-
boxylate AOH group vibrations, respectively. In the
multidirectional complexes, that these bands disappear
has demonstrated chelation of oxygen to the metal.
These may also overlap with vibrations near 1385–1398
cmꢁ1 can be assigned to COOꢁ. In the tripodal-trinu-
clear complexes, the bands in the 538–619 and 468–495
cmꢁ1 ranges can be attributed to the M-N and M-O
stretching modes [7,8].
Thermal stabilities of compounds have also thermally
been investigated, and their plausible degradation [35]
schemes are presented in Table 2. Thermal decomposi-
tion of the anhydrous compounds starts in the range of
94–495ꢀC and completes in the range 550–650ꢀC. The
observed weight losses for all compounds are in good
agreement with the calculated values.
CONCLUSIONS
The magnetic behavior of Fe(III) and Cr(III) com-
plexes is good harmony with proposed octahedral struc-
tures. The magnetic moment per mono-, di-, tri-, and tetra-
In this study, multidirectional cyanuric chloride based
‘‘(2), (3), (4) and (5)’’ were synthesized. Synthetic strategy
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

July 2011
Complexes of Iron(III) and Chromium(III) Salen and Salophen Schiff Bases
with Bridging 1,3,5-Triazine Derived Multidirectional Ligands
775
[14] Jan, J. Z.; Huang, B. H.; Lin, J. J. Polym 2003, 44, 1003.
for preparing mono-, di-, tri-, and tetra-nuclear was used
a complex as a ‘‘ligand’’ that contains a potential donor
group capable of coordinating to the other ligand.
[{Fe(salen/salophen)}2O] and [{Cr(salen/Salophen)}2O]
were chosen as ‘‘ligand complexes’’ because the ligand
complexes can be coordinated with other ligand. These
complexes are the examples of mono-, di-, tri-, and
tetra- nuclear complexes bridged by carboxylate anions
to the iron and chromium centers. Their structures
were characterized by means of FT-IR spectroscopy,
elemental analysis, AAS, thermal analysis, and mag-
netic susceptibility measurements. The magnetic data
for the mono-, di-, tri-, and tetra- nuclear complexes
show well agreement with the d5 and d3 metal ion in
an octahedral structure.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet