Four new trinuclear Fe(III) complexes involving tetradenta Schiff bases N,N1-bis(salicylidene) ethylenediamine- (salenH2) or bis(salicylidene)-o-phenylenediamine-(salophH2) with 2,4,6-tris(2,5-dicarboxyphenylimino-4-formylphenoxy)- 1,3,5-triazine (DCPI-TRIPOD) or 2,4,6-tris(4-carboxyphenylimino-4¢-formylphenoxy)-1,3,5-triazine (CPI-TRIPOD) have been synthesized and characterized by means of elemental analysis carrying out 1H-n.m.r., i.r. spectroscopy, thermal analyses and magnetic susceptibility measurements. The complexes can also be characterized as high-spin distorted octahedral FeIII bridged by carboxylic acids. The tricarboxylic acids play a role as bridges for weak antiferromagnetic intramolecular exchange.

1. Complexes of iron(III) salen and saloph Schiff bases with bridging 2,4,6-tris(2,5-
dicarboxyphenylimino-4-formylphenoxy)-1,3,5-triazine and 2,4,6-tris(4-carboxyphen-
ylimino-4¢-formylphenoxy)-1,3,5-triazine
Ziya Erdem Koc* and H. Ismet Ucan
Department of Chemistry, Selcuk University, 42031 Selcuklu, Konya, Turkey.
Received 13 December 2006; accepted 16 February 2007
Abstract
Four new trinuclear Fe(III) complexes involving tetradenta Schiff bases N,N1
-bis(salicylidene) ethylenediamine-
(salenH2) or bis(salicylidene)-o-phenylenediamine-(salophH2) with 2,4,6-tris(2,5-dicarboxyphenylimino-4-formyl-
phenoxy)-1,3,5-triazine (DCPI-TRIPOD) or 2,4,6-tris(4-carboxyphenylimino-4¢-formylphenoxy)-1,3,5-triazine
(CPI-TRIPOD) have been synthesized and characterized by means of elemental analysis carrying out 1
H-n.m.r., i.r.
spectroscopy, thermal analyses and magnetic susceptibility measurements. The complexes can also be characterized
as high-spin distorted octahedral FeIII
bridged by carboxylic acids. The tricarboxylic acids play a role as bridges for
weak antiferromagnetic intramolecular exchange.
Introduction
An important class of compounds consists of substi-
tuted s-triazine derivatives which have anticancer, anti-
tumor, antiviral and antifungal activity. These
compounds have been used in the treatment of depres-
sion and hence gained a considerable importance. These
are valuable bases for estrogen receptor modulators and
are also used as bridging agents to synthesize herbicides
and in the production of drugs or polymers [1, 2].
We have reported here that a trialdehyde and its
Schiff bases have been synthesized to become a new
template. The reaction of trimeric cyanuric chloride
(C3N3Cl3) with 3 equiv of 4-hydroxybenzaldehyde in
benzene has given the desired trialdehyde in a single
step, coded to be TRIPOD. Trialdehyde [3, 4] was
then reacted under reflux with 5-aminoisophthalic acid
or 4-aminobenzoic acid and 2,4,6-tris(2,5-dicarboxy-
phenylimino-4-formylphenoxy)-1,3,5-triazine (DCPI-
TRIPOD) or 2,4,6-tris(4-carboxyphenylimino-4¢-form-
ylphenoxy)-1,3,5-triazine, respectively. It may be useful
to stress at this point that the new products mentioned
above are the main result of this work. These are the
first in the literature and we call them ‘‘Oxy-Schiff
Bases’’ due to literature [1].
Schiff bases of iron(III) have been known since
1938. The magnetochemical properties of the l-oxo-
bridged complexes [{Fe(salen)}2O] [(salenH2 = N,N1
-
bis(salicylidene)ethylene diamine)] and [{Fe(sal-
oph)}2O] [(salophH2 = bis(salicylidene)-2-phenylenedi-
amine)] and their X-ray studies have widely been
presented in the literature [5–9]. Kessel and Hendrick-
son [10] have studied Schiff base complexes of iron(III)
incorporating p-quinone bridges. The reactions of
[{Fe(salen)}2O] with carboxylic acids have been given
by Wollmann and Hendrickson [11]. They used tri-
chloroacetic, trifloroacetic, salicylic and picric acids,
and characterized the prepared complexes as dimers of
composition [Fe(salen)X]2, where X is the monoanion
of the appropriate acid. The complexes [{Fe(salen)}2L]
and [{Fe(saloph)}2L] (where L = terephthalate, fuma-
rate, oxalate and succinate dianion) have been pre-
pared. The crystal and molecular structure of
[{Fe(salen)}2ter] (H2ter = terephthalic acid) have been
reported [12]. Other complexes of composition [{Fe(sa-
len)}2L] (where L = glutarate, adipate, pimelate, su-
berate and dithiooxamidedianion) were prepared by
Smekal et al. [13]. Therefore, in this work, we have
aimed to make other 1,3,5-tricarboxylato bridges and
to present their certain influences on the magnetic
behaviour of the prepared complexes. We are also
interested in Tripodal-Trinuclear systems formed by
the 1,3,5-tricarboxylato bridges because no satisfactory
work dealing with this bridge and associated data have
appeared in the literature.
Experimental
Elemental analyses were performed on a Carlo Erba
1106 elemental analyzer. The IR spectra were recorded
using KBr discs (4000–440 cm)1
) on a Perkin Elmer
1600 series FT-IR spectrophotometer. The 1
H-NMR
spectra in CDCl3, d6-DMSO was obtained using a
Bruker 200 MHz spectrometer. MMM-Medcenter,
* Author for correspondence: E-mail: zkoc@selcuk.edu.tr
Transition Metal Chemistry (2007) 32:597–602 Springer 2007
DOI 10.1007/s11243-007-0213-7

2. Einrichtungen GmbH Vacucell 22, Vacuum Cabinets.
Melting points were measured using a Buchi SMP-20
melting point apparatus. The thermal analyses were
performed on Shimadzu DTA 50 and TG 50 H mod-
els using 10 mg samples. The DTA and TG curves
were obtained at a heating rate of 10 C min)1
. In all
cases, the 22–750 C temperature range was studied
under a dry nitrogen atmosphere. All the other chemi-
cals were purchased from Aldrich and used as
received. The trialdehyde (TRIPOD) [2,4,6-tris(p-form-
ylphenoxy)-1,3,5-triazine] were prepared by established
literature procedures [3]. Magnetic Susceptibilities of
metal samples were determined using a Sheerwood Sci-
entific MX Gouy magnetic susceptibility apparatus
and magnetic measurements were carried out using the
Gouy method with Hg[Co(SCN)4] as calibrant. The
effective magnetic moments, leff, per metal atom was
calculated from the expression: leff ¼ 2:84
ffiffiffiffiffiffi
vM
p
, where
vM is the molar susceptibility.
Preparation of ligand complexes
[{Fe(salen)}2O] and [{Fe(saloph)}2O] were prepared by
adding concentrated ammonia solution to stirred hot
EtOH solutions of [Fe(salen)Cl] and [Fe(saloph)Cl],
respectively, until they became alkaline [5, 14].
The synthesis procedure for 2,4,6-tris(2,5-
dicarboxyphenylimino-4-formylphenoxy)-1,3,5-triazine
(DCPI-TRIPOD)
Solid K2CO3 (18 mmol 3.10 g or 9 mmol 1.55 g and
25% excess) was added to a solution of 5-aminoiso-
phthalic (3 mmol, 0.68 g) or 4-aminobenzoic acid
(3 mmol, 0.51 g) in 20 ml AcOEt with stirring. After
the suspension of TRIPOD (0.44 g, 1 mmol) in 10 ml
AcOEt was added dropwise with stirring. The mixture
was then boiled under reflux for 24 h. The reaction
solution was left stirring overnight. The mixture was
dissolved in water and, then, the solution was filtered
to remove some insoluble impurities. The 0.5 N HCl
was added to solution until pH = 5 and the filtrate
was evaporated slowly over the day. The precipitated
yellow crystals were filtered. The solvent was removed
and the resulting solid was filtered off and then recrys-
tallized with EtOH, dried in a vacuum cabinet and
stored in a desiccator over CaCl2 DCPI-TRIPOD FT-
IR (cm)1
) 3258 (OH), 2845 (CH), 1715 (C=O), 1610
(CH=N), 1567 (C=N triazine), 1470 (N=N triazine),
1366 (COC). 1
H-NMR (CDCl3) d 13.92 (s, 3H), 9.08
(s, 3H), 8.64 (d, 6H, j = 8.50 Hz), 7.72, (d, 6H,
j = 8.50 Hz), 7.62 (s, 3H), 5.79 (d, 6H).
The synthesis procedure for 2,4,6-tris(4-
carboxyphenylimino-4¢-formylphenoxy)-1,3,5-triazine
(CPI-TRIPOD)
2,4,6-Tris(4-carboxyphenylimino-4¢-formylphenoxy)-
1,3,5-triazine (CPI-TRIPOD) was prepared following
the same procedure described above for 2,4,6-tris(2,5-
dicarboxyphenylimino-4-formylphenoxy)-1,3,5-triazine
(DCPI-TRIPOD). CPI-TRIPOD FT-IR (cm)1
) 3234
(OH), 2840 (CH), 1700 (C=O), 1605 (CH=N), 1560
(C=N triazine), 1466 (N=N triazine), 1359 (COC).
1
H-NMR (CDCl3) d 12.49 (s, 3H), 8.75 (s, 3H), 8.50,
(d, 6H, j = 7.50 Hz) 7.72 (d, 6H, j = 7.50 Hz), 7.60
(d, 6H, j = 7.00 Hz), 6.79 (d, 6H, j = 7.00 Hz).
[{Fe(salen)}6(DCPI-TRIPOD)] Æ 3H2O or
[{Fe(salen)}3(CPI-TRIPOD)] Æ 3H2O complexes
[{Fe(salen)}2O] (3 mmol, 1.98 g or 1.5 mmol 0.99 g)
was suspended in hot EtOH (25 ml) and a solution of
2,4,6-tris(2,5-dicarboxyphenylimino-4-formylphenoxy)-
1,3,5-triazine (DCPI-TRIPOD) (0.93 g, 1 mmol) or
2,4,6-tris(4-carboxyphenylimino-4¢-formylphenoxy)-
1,3,5-triazine (CPI-TRIPOD) (0,80 g, 1 mmol) in
ETOH was added by stirring. The reaction mixture
was boiled under reflux for 4 h, and the dark brown
solid formed was dried under vacuum. [{Fe(sa-
len)}6(DCPI-TRIPOD)] Æ 3H2O FT-IR (cm)1
): 3480
(OH), 2835 (CH), 1595 (CH=N), 1560 (C=N tri-
azine), 1440 (N=N triazine), 1534 (COC), 534 (M–N),
468 (M–O). [{Fe(salen)}3(CPI-TRIPOD)] Æ 3H2O
FT-IR (cm)1
): 3474 (OH), 2833 (CH), 1590 (CH=N),
1549 (C=N triazine), 1445 (N=N triazine), 1550
(COC), 540 (M–N), 470 (M–O).
[{Fe(saloph)}6(DCPI-TRIPOD)] Æ 3H2O or
[{Fe(saloph)}3(CPI-TRIPOD)] Æ 3H2O complexes
The [{Fe(saloph)}2O] complexes were prepared in the
same way as mentioned above for the [{Fe(salen)}2O]
complexes using EtOH as solvent for [{Fe(sal-
oph)}6(DCPI-TRIPOD)] Æ 3H2O or [{Fe(saloph)}3
(CPI-TRIPOD)]. [{Fe(saloph)}6(DCPI-TRIPOD)] Æ
3H2O FT-IR (cm)1
): 3461 (OH), 2831 (CH), 1598
(CH=N), 1556 (C=N triazine), 1443 (N=N triazine),
1533 (COC), 545 (M–N), 475 (M–O). [{Fe(sal-
oph)}3(CPI-TRIPOD)] Æ 3H2O FT-IR (cm)1
): 3477
(OH), 2825 (CH), 1593 (CH=N), 1545 (C=N tri-
azine), 1448 (N=N triazine), 1544 (COC), 555 (M–N),
480 (M–O).
Results and discussion
2,4,6-tris(p-formylphenoxy)-1,3,5-triazine (TRIPOD)
was prepared through the reaction of cyanuric chloride
and 4-hydroxybenzaldehyde (Figure 1). The structural
formula of the 2,4,6-tris(4-formylphenoxy)-1,3,5-tri-
azine (1) was verified by elemental analyses, 1
H-
n.m.r., i.r. and mass spectral data [3] (Figure 1). Con-
densation of 2,4,6-tris(p-formylphenoxy)-1,3,5-triazine
(1) with amines (2–3) was readily furnished and as a
result of this reaction, ‘‘Tripodal Oxy-Schiff bases’’
have been obtained. Tripodal Oxy-Schiff bases
obtained were characterized by their elemental analy-
598

3. ses and thermal analyses, 1
H-n.m.r. and i.r., where
replacement of the carbonyl by the imine group causes
lowering of the energy of the C=O stretch in the IR
spectrum and a shift to higher field of the CH=N
proton signal in the 1
H-n.m.r. spectrum. The ‘‘Oxy-
Schiff bases’’ prepared in this way have been obtained
in nearly quantitative yields and high purity
(Scheme 1). All the ligands are soluble in common
organic solvents. Synthetic strategy for preparing Tri-
podal-Trinuclear uses a complex as a ‘‘ligand’’ that
contains a potential donor group capable of coordinat-
ing to the another ligand. We have chosen [{Fe(sa-
len)}2O] and [{Fe(saloph)}2O] as ‘‘ligand complex’’
because it can coordinate to another ligand [15]. These
complexes are the first examples of Tripodal-Trinucle-
ar complexes bridged by carboxylate anions to the
iron centres (Scheme 1 and Figure 2). All compounds
are stable at room temperature in the solid state. The
results of the elemental analyses, given in Table 1, are
in a good agreement with the structures suggested for
the ligands and their complexes. The results show that
all complexes are trinuclear (Figure 2). All complexes
are also stable at room temperature and they are only
soluble in organic solvents such as DMSO, DMF and
insoluble in water.
The vibrations of the azomethine C=N, triazine
C=N and C=O of the free ligands have been ob-
served at 1610–1605, 1567–1560 and 1715–1700 cm)1
range, respectively, [16, 17]. In the complexes, these
bands are, however, shifted to lower frequencies, indi-
cating that the nitrogen and oxygen atoms of the
Tripodal Oxy-Schiff bases ligands are coordinated
to the ligand complexes. In the ligands 2,4,6-tris(2,5-
dicarboxyphenylimino-4-formylphenoxy)-1,3,5-triazine
(DCPI-TRIPOD) or 2,4,6-tris(4-carboxyphenylimino-
4¢-formylphenoxy)-1,3,5-triazine (CPI-TRIPOD) the
band at 3258–3234 cm)1
can be assigned to the
carboxylate OH group vibrations [18]. In the Tripodal-
Trinuclear complexes, these bonds disappear, suggest-
ing chelation of oxygen to the metal. In the complexes,
broad bands in the 3480–3461 cm)1
range are assigned
to the OH stretch of hydrated water molecules. In the
Tripodal-Trinuclear complexes, the bands in the
555–534 and 468–480 cm)1
ranges can be attributed to
the M–N and M–O stretching modes [19].
In order to identify the structures of solutions of the
Tripodal Oxy-Schiff bases ligands, the 1
H-n.m.r. spec-
tra were recorded in DMSO-d6 [20]. 1
H-n.m.r spectra
also confirmed the structures of the synthesized com-
pounds. The signals in the 1
H-n.m.r. spectrum of
2,4,6-tris(2,5-dicarboxyphenylimino-4-formylphenoxy)-
1,3,5-triazine (DCPI-TRIPOD) at d 13.92 and
9.08 ppm correspond to the carboxylate –OH and
Oxy-Schiff base HC=N proton resonances, respec-
tively. The 1
H-n.m.r. spectrum of 2,4,6-tris(4-carboxy-
phenylimino-4¢-formylphenoxy)-1,3,5-triazine (CPI-
TRIPOD) is similar to that of 2,4,6-tris(2,5-dicarboxy-
phenylimino-4-formylphenoxy)-1,3,5-triazine (DCPI-
TRIPOD).
The magnetic moments of the complexes given in
Table 1 were measured at room temperature. On the
basis of spectral evidence, the Tripodal FeIII
complexes
have trinuclear structures in which the FeIII
cation has
an approximately octahedral environment. The mag-
netic behaviour of FeIII
complexes is in accord with
proposed trinuclear structures [21]. The magnetic mo-
ment per trinuclear complexes which constructed be-
tween two of [{Fe(salen)}2O], [{Fe(saloph)}2O] and
either of 2,4,6-tris(2,5-dicarboxyphenylimino-4-formyl-
phenoxy)-1,3,5-triazine (DCPI-TRIPOD) and 2,4,6-
N
N
N
O
O
O
CHO
CHO
OHC
TRIPOD
5-aminoisophithalic acid
4-aminobenzoic acid
4-b, [{Fe(saloph)}2O]
H2N
COOH
COOH
H2N COOH
,
(1)
(2)
(3)
4-a, [{Fe(salen)}2O] and
(4)
Fe
O
O
N
N
Fe
O
O
N
N
and
,
Fig. 1. Structure of TRIPOD, amines and ‘‘ligand complexes’’.
599

4. N
N
N
O
O
O
N
N
N
COOH
COOH
HOOC
COOH
HOOC COOH
(DCPI-TRIPOD)
N
N
N
O
O
O
N
N
N
COOH
HOOC
COOH
(CPI-TRIPOD)
O
O
Fe O
O
N
N
N
N
N
O
O
O
N
N
N
O
O
Fe
O
O
N
N
O
O
Fe
O
O
N
N
O
O
Fe
O
O
N
N
O
O
Fe O
O
N
N
O
O
Fe
O
O
N
N
O
O
Fe
O
O
N
N
N
N
N
O
O
O
N
N
N
O
O
Fe
O
O
N
N
O
O Fe
O
O
N
N
(1)
(2) (3)
(4-a, 4-b)
[{Fe(saloph)}6(DCPI-TRIPOD)]
[{Fe(salen)}6(DCPI-TRIPOD)]
[{Fe(saloph)}3(CPI-TRIPOD)]
[{Fe(salen)}3(CPI-TRIPOD)]
R
R
R
R
R
R
R
R
R
R = -CH2-CH2- ,
(4-a, 4-b)
Scheme 1. Synthesis of DCPI-TRIPOD, CPI-TRIPOD and tripodal-trinuclear complexes.
2
3
4-a ,4-b
Fig. 2. Proposed structures of the Tripodal Oxy-Schiff base ligands and Tripodal-Trinuclear complexes.
600

5. tris(4-carboxyphenylimino-4¢-formylphenoxy)-1,3,5-tri-
azine (CPI-TRIPOD) are paramagnetic with a mag-
netic susceptibility value per atom: 1.55–1.59 B.M. and
1.69–1.70 B.M., respectively. It is seen that the
[{Fe(salen)}2O] and [{Fe(saloph)}2O] containing com-
pounds are represented by the electronic structure of
t2g
5
eg0
. The magnetic data for the [{Fe(salen)}2O] and
[{Fe(saloph)}2O] tripodal complexes show good agree-
ment with the d5
metal ion in an octahedral structure.
This consequence is supported by the results of the
elemental analyses suggesting that these Tripodal com-
plexes have also an octahedral structure [5].
All the ligands and complexes also have thermally
been investigated and their plausible degration
schemes are presented in Table 2 [22]. It has been well
known that there is a strong relation between tempera-
ture range for the dehydration process and the binding
mode of the water molecules of the respective metal
complexes. The elimination of water took place in a
single step process attributed to the release of the hy-
drated water molecules (in the 60–120 C range) [23].
Thermal decomposition of the anhydrous [{Fe(sa-
len)}2O] and [{Fe(saloph)}2O] complexes of the ligands
DCPI-TRIPOD and CPI-TRIPOD starts in the range
of 200–450 C and completes in the range 550–700 C.
The final decomposition products are metal oxides.
The observed weight losses for all ligands and com-
plexes are in good agreement with the calculated val-
ues.
Acknowledgements
The authors are please to acknowledge the Scientific
Research Projects (BAP) of Selçuk University for
grant with grant number No 2003/034.
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335–450
CPI-TRIPOD 295–385 35.3 (38.5) CO2, H2
60–122
[{Fe(salen)}3(CPI-TRIPOD)] Æ 3H2O 200–295 55.3 (58.7) H2O, CO2, N2, C2H4
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60–125
[{Fe(saloph)}3(CPI-TRIPOD)] Æ 3H2O 215–320 52.9 (54.8) H2O, CO2, N2
325–435
601

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TMCH 6726
602