Synthesis of 1,3,5-tris(4-(4-nitrophenyliminomethyl)phenoxymethyl)benzene as a new Schiff base and its complexation properties with the (salen and salophen)-bridged Fe/Cr(III)

Article abstract of DOI:10.1007/s10847-009-9708-5

In the present study, we discussed to synthesis of a new Schiff base with nitro groups and its complexation properties with Fe/Cr(III) salen/salophen capped complexes. For this, 1,3,5-tris (formylphenoxymethyl)benzene (1, TRIPOD) involving aldehyde groups was converted to the Schiff base derivative (2, TNPIM-TRIPOD) using 4-nitroaniline. The synthesized compound 2 were reacted with four new trinuclear Fe(III) and Cr(III) complexes involving tetradenta Schiff bases N,N-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophenH₂). Characterization of all compounds was made with elemental analysis, infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nuclear magnetic resonance (¹H-NMR), and magnetic susceptibility measurement. The complexes can also be characterized as low-spin distorted octahedral Fe(III) and Cr(III) bridged by nitro groups. Springer Science+Business Media B.V. 2009.

Full text of DOI:10.1007/s10847-009-9708-5

J Incl Phenom Macrocycl Chem (2010) 67:287–293
DOI 10.1007/s10847-009-9708-5
ORIGINAL ARTICLE
Synthesis of 1,3,5-tris(4-(4-nitrophenyliminomethyl)phenoxymethyl)
benzene as a new Schiff base and its complexation properties
with the (salen and salophen)-bridged Fe/Cr(III)
•
Ozcan Kocyigit Ersin Guler
Received: 8 September 2009 / Accepted: 13 November 2009 / Published online: 3 December 2009
Ó Springer Science+Business Media B.V. 2009
Abstract In the present study, we discussed to synthesis
of a new Schiff base with nitro groups and its complexation
properties with Fe/Cr(III) salen/salophen capped com-
plexes. For this, 1,3,5-tris (formylphenoxymethyl)benzene
(1, TRIPOD) involving aldehyde groups was converted
to the Schiff base derivative (2, TNPIM-TRIPOD) using
4-nitroaniline. The synthesized compound 2 were reacted
with four new trinuclear Fe(III) and Cr(III) complexes
involving tetradenta Schiff bases N,N-bis(salicylidene)
ethylenediamine-(salenH2) or bis(salicylidene)-o-phenyl-
enediamine-(salophenH2). Characterization of all com-
pounds was made with elemental analysis, infrared
spectroscopy (FT-IR), thermogravimetric analysis (TGA),
nuclear magnetic resonance (1H-NMR), and magnetic
susceptibility measurement. The complexes can also be
characterized as low-spin distorted octahedral Fe(III) and
Cr(III) bridged by nitro groups.
various applications, e.g., electrical conductivity, magne-
tism, host guest chemistry, ion exchange, catalysis, non-
linear optics, etc. [1–3]. Synthesis of new Schiff bases
and their metal complexes still the aim of many recent
investigations.
Schiff bases have played an important role in the
development of coordination chemistry as they readily
form stable complexes with most of the transition metals.
They show interesting properties, e.g., their ability to
reversibly bind oxygen [4], catalytic activity in hydroge-
nation of olefins [5] and transfer of an amino group
[6], photochromic properties [7], and complexing ability
towards toxic metals [8].
Condensation of salicylaldehydes or salicylaldehyde
derivatives with 1,2-diamines leads to the formation of one
extremely important class of ligands, generally known as
‘‘Salens’’ (accordingly with o-phenylenediamine, Salo-
phen). Schiff base complexes of either salen or salophen
type ligands with transition and main groups metal ions
have been attracting increasing attention because of their
importance in different fields, such as catalysis and mate-
rial chemistry. The bridged complexes of salen–salophen
are especially attractive by latest studies in inorganic
chemistry [9–11]. The role of the metal center in deter-
mining the characteristics of these complexes is manifold.
For example, it has been shown that catalytic and fluo-
rescent properties of complexes are strictly related to the
coordinated metal [12–15].
Keywords Synthesis ꢀ Trisaldehyde ꢀ Schiff base ꢀ
4-Nitroaniline
Introduction
Investigation on metal organic complexes represents one of
the most active areas of material science and chemical
research. Major advances have been made in these mate-
rials due to their interesting properties and potential in
Salen/salophen ligands can be used to achieve this
coordination number for soluble, stable, and higher-coor-
dinate main group compounds [16]. For example, some
five-coordinate compounds of aluminum [17–21], gallium
[22, 23], indium [24] have been reported. Some of these
can act as precursors to six-coordinate cations [25, 26].
Beyond their fundamental interest and novelty, these high
O. Kocyigit (&) ꢀ E. Guler
Department of Chemistry, Selcuk University,
42031 Konya, Turkey
e-mail: okocyigit40@gmail.com
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1,3,5-Tris(4-(4-nitrophenyliminomethyl)phenoxymethyl)-
benzene (2, TNPIM-TRIPOD)
coordinate Salen-main group compounds are finding
applications in catalysis [27–30]. For example, the asym-
metric addition of diorgano-H-phosphonates to carbonyls
(the phospho-aldol reaction) has been found to be catalyzed
by chiral complexes of aluminum containing the salycen
ligand framework, [(R,R)-Salcyen]AlX (XMe, OSi-Me2
tBu) [31].
The solution of 1,3,5-Tris(formylphenoxymethyl)benzene
(1.0 mmol, 0.48 g) in methanol was added drop by drop
upon the solution of 4-aminonitrobenzene (3.0 mmol,
0.51 g) in 50 mL methanol. The mixture was refluxed
24 h. Then, the mixture was precipitated with 1.0 N HCl
solution and the residue was filtered. The crude product
was extracted with ethyl acetate/water mixture (1:1)
(3 9 30 mL). The organic phase was separated and dried
with Na2SO4. The solvent was removed in a rotary evap-
orator. The resulting solid was dried in 70 °C. For
C48H36N6O9, Yield; 63%, FT-IR (KBr); 1,684 cm-1
Tripodal ligands have long been used in both coordi-
nation and organometallic chemistry [32, 33]. Tripodal
ligands have also long been used in both coordination and
bioinorganic chemistry; typical examples include the tri-
podal ligands, tripyridylalkylamine, triazine and polypyr-
idylamine [34–36].
The aim of the present study is to synthesis of new
Tripodal-Trinuclear systems formed by the 1,3,5-tri nitro
bridges and to present their effects on magnetic behaviour
of Fe/Cr(III) salen/salophen capped complexes.
1
(C=N), H-NMR (CDCl3): d = 5.20 (s, 6H, CH2–O), 6.61
(d, 6H, Ar–H, J = 8.6 Hz), 7.21–7.24 (m, 6H, Ar–H), 7.83
(s, 3H, Ar–H), 7.85–7.89 (m, 6H, Ar–H), 8.06 (d, 6H, Ar–
H, J = 8.6 Hz), 8.35 (s, 3H, CH=N).
Preparation of [TNPIM-TRIPOD-{Fe(III)(salen/salophen)
(3,4)}] and [TNPIM-TRIPOD-{Cr(III)(salen/salophen)
(5,6)}] complexes
Experimental
Materials and methods
A solution of TNPIM-TRIPOD (0.84 g, 1 mmol) and [{Fe/
Cr(salen)}2O] (1.03 g, 1.5 mmol) or [{Fe/Cr(salophen)}2O]
(1.02 g, 1.5 mmol) in 20 mL of absolute ethanol were
refluxed for 3 h. The mixture was allowed to cool to
room temperature. Then the mixture was filtered and dried
in vacuum. Elemental analysis, magnetic and physical
properties of the synthesized complexes are given in
Table 1. Molecule formulas of complex 3,4,5 and 6 are
Fe3C102H87N12O15CI3ꢀ3H2O, Fe3C114H87N12O15CI3ꢀ3H2O,
Cr3C102H87N12O15CI3ꢀ3H2O and Cr3C114H87N12O15CI3ꢀ
3H2O respectively.
All starting materials and reagents used were of standard
analytical grade from Fluka, Merck as well as from Aldrich
and used without further purification. [{Fe(salen)2}O],
[{Fe(salophen)2}O], [{Cr(salen)2}O] and [{Cr(salophen)2}O]
were prepared according to previously published methods
[37, 38]. Melting points were measured using a Buchi B-540
melting point apparatus. 1H-NMR spectra were recorded on
a Varian 400 MHz spectrometer at room temperature.
Thermal gravimetric analysis (TGA) was carried out with
Seteram thermogravimetric analyzer. The sample weight
was 15–16 mg. Analysis was performed from room tem-
perature to 900 °C at heating rate of 15 °C/min in argon
atmosphere with a gas flow rate of 20 mL/min. The ele-
mental analysis for the ligand and the bridged complexes
were carried out at on a Hewlett-Packard 185 analyzer. FT-
IR spectra were recorded using a Mattson-1000 FT-IR using
KBr pellets. Magnetic susceptibilities of metal complexes
were determined using a Sheerwood Scientific MX Gouy
magnetic susceptibility apparatus 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 = 2.84.(vM)1/2, where vM is the molar
susceptibility.
Results and discussion
The complexation with [{Fe/Cr(salen)}2O] and [{Fe/
Cr(salophen)}2O] of TNPIM-TRIPOD ligand was observed
in this manuscript. For this, we have synthesized to TRIPOD
(1) using 1,3,5-trisbromomethylbenzene and 4-hydroxy-
benzaldehyde in presence of K2CO3 according to literature
[10]. Then, the Tripodal Schiff base (TNPIM-TRIPOD, 2)
was synthesized using TRIPOD (1) and 4-aminonitroben-
zene in methanol media (Scheme 1). The synthesized
1
compounds were characterized with H-NMR, FT-IR and
elemental analysis. The synthesis of TNPIM-TRIPOD (2) as
new a Schiff base was confirmed by the disappearance of
aldehyde protons (9.89 ppm) in TRIPOD and the appear-
ance of imine protons (CH=N) at 8.35 ppm belong to
Synthesis
1,3,5-Tris(formylphenoxymethyl)benzene (1,TRIPOD) used
in this study was synthesized in previously our study [39].
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289
Table 1 Elemental analysis, magnetic and physical properties of the compounds
Compound
Colour
leff (B.M.)
298 °C
M.p.
(°C)
Yield Found (Calcd.) (%)
(%)
C
N
H
M
TRIPOD
Cream
–
155 85
74.99 (74.95)
–
5.03 (5.02)
4.32 (4.30)
4.35 (4.32)
–
–
TNPIM-TRIPOD
Yellow
–
100 63
310 60
68.56 (68.60) 9.99 (9.94)
63.80 (63.76) 9.30 (9.27)
[{Fe(salen)3(TNPIM-TRIPOD)] Tile red
Cl3ꢀ3H2O
[{Cr(salen)3(TNPIM-TRIPOD)] Light green
Cl3ꢀ3H2O
[{Fe(salophen)3(TNPIM-
1.66
9.27 (6.58)
8.69 (8.62)
8.59 (8.55)
8.04 (8.00)
3.40
1.70
3.52
298 65
325 70
64.21 (64.16) 9.36 (9.37)
66.47 (66.39) 8.61 (8.64)
66.87 (66.80) 8.66 (8.63)
4.38 (4.32)
4.03 (4.00)
4.05 (4.01)
Brick red
TRIPOD)]Cl3ꢀ3H2O
[{Cr(salophen)3(TNPIM-
Dark green
[400 65
TRIPOD)]Cl3ꢀ3H2O
Scheme 1 Synthesis of
TNPIM-TRIPOD (2)
TNPIM-TRIPOD compound. The TNPIM-TRIPOD pre-
pared in the way have been obtained in nearly quantitative
yield and high purity. Synthetic strategy for preparing Tri-
podal-Trinuclear uses a complex as a ‘‘ligand’’ that contains a
potential donor group capable of coordinating to another
ligand. The [{Fe(salen)}2O] and [{Fe(salophen)}2O] as
‘‘ligand complex’’ have been chosen because it can coordi-
nate to another ligand [40]. These complexes are the first
examples of Tripodal-Trinuclear complexes bridged by nitro
groups to the iron and chromium centers (Scheme 2). The
complexation with ligand of salen or salophen complexes
does not occur with CH=N-system, because CH=N region of
ligand has steric hindrance for salen or salophen groups and
six-coordination is more stable than five-coordination for
Fe(III) and Cr(III) complexes. Therefore, salen or salophen
groups prefers to complexation with nitro groups instead of
CH=N-system. Prepared complexes are stable at room tem-
perature in the solid state. The results of the elemental anal-
yses presented in Table 1 are in a good agreement with the
structures suggested for the ligand and their complexes. In
addition, the prepared salen and salophen based capped
complexes were characterized with elemental analysis, ther-
mal gravimetric analysis, magnetic susceptibility and FT-IR.
The magnetic moments of the prepared all complexes
were measured at room temperature (Table 1). On the basis
of spectral evidence, the Tripodal Fe(III) and Cr(III)
complexes have trinuclear structures in which the Fe(III)
and Cr(III) cations have an approximately octahedral
environment. The magnetic behavior of Fe(III) and Cr(III)
complexes is in accord with proposed trinuclear structures
[41]. The magnetic moment per trinuclear complexes
which were constructed from [{Fe(salen)}2O], [{Fe(salo-
phen)}2O], [{Cr(salen)}2O] and [{Cr(salophen)}2O] either
of 1,3,5-Tris(4-(4-nitrophenyliminomethyl)phenoxymethyl)
benzene (TNPIM-TRIPOD) shows paramagnetic property
with a magnetic susceptibility value per atom: 1.66–1.70
B.M. and 3.40–3.52 B.M., respectively. It is seen that the
[{Fe(salen)}2O], [{Fe(salophen)}2O], [{Cr(salen)}2O] and
[{Cr(salophen)}2O] containing compounds are represented
by the electronic structure of t2g5eg0 and t2g3eg0. The
magnetic data for the [{Fe(salen)}2O], [{Fe(salophen)}2O],
[{Cr(salen)}2O] and [{Cr(salophen)}2O] tripodal com-
plexes indicate good agreement with the d5 and d3 metal
ion in an octahedral structure. This magnetic data are
supported by the results of the elemental analyses sug-
gesting that these Tripodal complexes have also an octa-
hedral structure [37].
The FT-IR spectrums of the ligand and salen and salo-
phen based capped complexes were presented in Figs. 1
and 2. The Fig. 1 shows TRIPOD, TNPIM-TRIPOD,
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Scheme 2 Complexation
between TNPIM-TRIPOD and
Fe(III)–Cr(III) salen/salophen
groups
Fig. 1 The FT-IR spectra of
TRIPOD, TNPIM-TRIPOD,
[{Fe(salen)}3(TNPIM-
TRIPOD)]Cl3ꢀ3H2O and
[{Fe(salophen)}3(TNPIM-
TRIPOD)]Cl3ꢀ3H2O
[{Fe(salen)}3(TNPIM-TRIPOD)Cl3ꢀ3H2O] and [{Fe(salo-
phen)}3(TNPIM-TRIPOD)Cl3ꢀ3H2O]. The Fig. 2 shows
TRIPOD, TCPIM-TRIPOD, [{Cr(salen)}3(TCPIM-TRI-
POD)Cl3ꢀ3H2O] and [{Cr(salophen)}3(TCPIM-TRIPOD)
Cl3ꢀ3H2O]. The vibrations of the aldehyde C=O of TRI-
POD, N=O and imine C=N of TNPIM-TRIPOD have been
observed at 1707, 1570 and 1684 cm-1 respectively. In the
complexes, although the C=N bands shifted to higher
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J Incl Phenom Macrocycl Chem (2010) 67:287–293
291
Fig. 2 The FT-IR spectra of
TRIPOD, TNPIM-TRIPOD,
[{Cr(salen)}3(TNPIM-
TRIPOD)]Cl3ꢀ3H2O and
[{Cr(salophen)}3(TNPIM-
TRIPOD)]Cl3ꢀ3H2O
frequencies (1,692 cm-1 for 3,4 and 1690, 1684 cm-1 for
5,6), the N=O bands shifted to lower frequencies (1538,
1539 cm-1 for 3,4 and 1514, 1540 cm-1 for 5,6), and
reduced intensity of these bands. These results indicate that
the nitrogen and oxygen atoms of the Tripodal Schiff base
ligands are coordinated to the ligand complexes [41]. In the
Tripodal-Trinuclear complexes, the bands in the 540–550
and 470–488 cm-1 range can be attributed to the M-N and
M-O stretching modes.
The thermal stability of prepared some complexes
([{Cr(salen)}3(TNPIM-TRIPOD)]Cl3ꢀ3H2O) and ([{Fe(sa-
lophen)}3(TNPIM-TRIPOD)]Cl3ꢀ3H2O) was evaluated by
thermal gravimetric analysis (TGA). It was found that
[{Cr(salen)}3(TNPIM-TRIPOD)]Cl3ꢀ3H2O undergoes
a
three-step thermal degradation (Fig. 3). At 50–350 °C,
decomposition is due to the loss of crystal water and NO2
from main structure. Also, the C6H6, C2H4, CN and CO
groups leaves from structure at 350–700 °C. Although the
Fig. 3 TG and its 1st
derivatives (dTG) of
[{Cr(salen)}3(TNPIM-
TRIPOD)]Cl3ꢀ3H2O
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J Incl Phenom Macrocycl Chem (2010) 67:287–293
Fig. 4 TG and its 1st
derivatives (dTG) of
[{Fe(salophen)}3(TNPIM-
TRIPOD)]Cl3ꢀ3H2O
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total weigh lost was theoretically calculated to be 36.05%,
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Fig. 4 shows thermal stability of [{Fe(salophen)}3
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C6H6, C2H4 and CO groups. For this complex, although the
total weigh lost was theoretically calculated to be 34.97%,
it was observed experimentally to be 39.60%.
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