The (salophen)-bridged Fe/Cr (III) capped complexes with triphenylene core: Synthesis and characterization

Article abstract of DOI:10.1016/j.jorganchem.2011.06.020

This article describes synthesis of the difference carboxylic acid derivatives of triphenylene and its complexation properties with Fe/Cr (III)-salophen. For this purpose, the carboxylic acid derivatives of 2,3,6,7,10,11-hexahydroxytriphenylene were synthesized and then reacted with four new Fe(III) and Cr(III) complexes involving tetradenta Schiff bases bis(salicylidene)-o-phenylenediamine-(salophenH₂). The prepared compounds were characterized by means of elemental analysis carrying out infrared spectroscopy (IR), thermogravimetric analysis (TG), nuclear magnetic resonance (¹H NMR), elemental analysis and magnetic susceptibility measurement. The complexes can also be characterized as low-spin distorted octahedral Fe(III) and Cr (III) bridged by carboxylic acids.

Full text of DOI:10.1016/j.jorganchem.2011.06.020

Journal of Organometallic Chemistry 696 (2011) 3106e3112
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
The (salophen)-bridged Fe/Cr (III) capped complexes with triphenylene core:
Synthesis and characterization
*
Ozcan Kocyigit , Ersin Guler
Selcuk University, Department of Chemistry, 42031 Konya, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
This article describes synthesis of the difference carboxylic acid derivatives of triphenylene and its
complexation properties with Fe/Cr (III)esalophen. For this purpose, the carboxylic acid derivatives of
2,3,6,7,10,11-hexahydroxytriphenylene were synthesized and then reacted with four new Fe(III) and
Cr(III) complexes involving tetradenta Schiff bases bis(salicylidene)-o-phenylenediamine-(salophenH2).
The prepared compounds were characterized by means of elemental analysis carrying out infrared
spectroscopy (IR), thermogravimetric analysis (TG), nuclear magnetic resonance (1H NMR), elemental
analysis and magnetic susceptibility measurement. The complexes can also be characterized as low-spin
distorted octahedral Fe(III) and Cr (III) bridged by carboxylic acids.
Received 2 March 2011
Received in revised form
18 May 2011
Accepted 14 June 2011
Keywords:
Complexation
Triphenylene
Carboxylic acid
Salophen
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
Condensation of salicylaldehydes or salicylaldehyde derivatives
with 1,2-diamines leads to the formation of one extremely impor-
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 materials due to their inter-
esting properties and potential in various applications, e.g., elec-
trical conductivity, magnetism, host guest chemistry, ion exchange,
catalysis, nonlinear optics, etc. [1e3]. 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 hydrogenation of
olefins [5], transfer of an amino group [6], photochromic properties
[7] and complexing ability toward toxic metals [8].
Schiff base ligands are considered “privileged ligands” because
they are easily prepared by the condensation between aldehydes
and imines. The Schiff base ligands with nitrogen, oxygen and sulfur
donor atoms in their structures act as good chelating agents for the
transition and non-transition metal ions [9,10]. As is known, tran-
sition metal complexes of Schiff bases are compounds which are
becoming increasingly important in the pharmaceutical, dye and
plastic industries as well as for liquid-crystal technology and
mechanistic investigations of the drugs used in pharmacology,
biochemistry and physiology [11,12]. Schiff bases a class of chelators
capable of forming coordinate bonds with many of metal ions
through both azomethine and phenolic groups [13e16].
tant class of ligands, generally known as “Salens”(accordingly with
o-phenylenediamine, Salophen). Salen-type and Salophen-type
ligands with N and O donor atoms are important since their metal
complexes find widespread applications as homogeneous and
heterogeneous catalysts in various organic transformation reactions
[17]. The bridged complexes of salenesalophen are especially
attractive by lastest studies in inorganic chemistry [18e20].
Triphenylene with a disc structure was first described in 1935
[21]. Chandrasekhar et al. [22] reported that a disc-shaped mole-
cule is able to organize into a liquid-crystalline structure. Now,
triphenylene derivatives, especially symmetrically substituted
hexaethers, have developed into an important class of discotic
liquid-crystalline structures. These fascinating discogens may find
commercial applications in quasi-one-dimensional conductors
[23,24], photoconductors [25], and light-emitting diodes [26].
Many efforts have been directed toward triphenylene-related areas
during the past two decades [27,28].
In the present study, we synthesized the carboxylic acid deriv-
atives of triphenylene as ligand and their Fe/Cr(III) salophen capped
complexes. In addition, the characteristic properties, FT-IR and TG/
dTG results of these complexes were presented and evaluated in
this study.
2. Results and discussion
In order to evaluate the complexationwith [{Fe/Cr(salophen)}2O]
of the carboxylic acid derivatives of triphenylene as ligand, firstly we
* Corresponding author. Tel.: þ90 3322233878; fax: þ90 3322230106.
E-mail address: kocyigit76@gmail.com (O. Kocyigit).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.06.020

O. Kocyigit, E. Guler / Journal of Organometallic Chemistry 696 (2011) 3106e3112
3107
have synthesized compounds 3, 4 and 5 using ethyl bromoacetate,
methyl 5-bromovalerate or methyl (4-bromomethyl) benzoate in
presence of K2CO3 (Fig. 1). After then, the prepared ester derivatives
of triphenylene was converted to the carboxylic acid derivatives (5, 6
and 7) with NaOH in ethanol media (Fig. 1). These compounds were
characterized with 1H NMR, FT-IR and elemental analysis. The 1H
NMR values of the synthesized compounds was given in experi-
mental part. In addition to this, the 1H NMR spectrums of compound
2 and 5 were presented in Figs. 2 and 3. The formation of 2
(2,3,4,6,7,10,11-Hexakis(ethoxycarbonylmethoxy)triphenylene)was
confirmed by the disappearance of the phenoliceOH at 9.26 ppm in
HHTP and the appearance of the eOCH2 and eCH3 protons at 4.33
Fig. 1. Synthesis of the carboxylic acid derivatives of triphenylene.

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O. Kocyigit, E. Guler / Journal of Organometallic Chemistry 696 (2011) 3106e3112
Fig. 2. The 1H NMR spectrum of compound 2.
and 1.32 ppm in 2, respectively (Fig. 2). As seen Fig. 3, the synthesis of
5 was confirmed by the disappearance of eOCH2 and eCH3 protons
belong to compound 2. All of compounds prepared in the way have
been obtained in nearly quantitative yield and high purity. The
obtained carboxylic acid derivatives were converted to complexes
bridged bycarboxylate anions to the chromium and iron center with
[{Fe/Cr(salophen)}2O] as “ligand complex”. We have chosen [{Fe/
Cr(salophen)}2O] as “ligand complex” because it can coordinate to
another ligand [29]. These complexes are the first examples of
complexes bridged by carboxylate anions to the iron and chromium
Fig. 3. The 1H NMR spectrum of compound 5.

O. Kocyigit, E. Guler / Journal of Organometallic Chemistry 696 (2011) 3106e3112
3109
Fig. 4. Synthetic routes for complexation between Fe/Cr(III)esalophen and compound 5, 6 or 7.
centers (Fig. 4). 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. In addition, the synthesized Fe/Cresalophen
capped complexes were characterized with elemental analysis,
thermal gravimetric analysis, magnetic susceptibility and FT-IR.
The magnetic moments of the complexes presented in Table 1
were measured at room temperature. The results shows that the
Fe(III) and Cr(III) complexes have hexanuclear 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 hexanuclear structures. The magnetic
moment per hexanuclear complexes which were constructed from
[{Fe(salophen)}2O] and [{Cr(salophen)}2O] either of 5, 6 and 7
indicates paramagnetic property with a magnetic susceptibility
value per atom: 1.98, 3.42 B.M. for 5, 1.79, 3.42 B.M. for 6 and 1.85,

3110
O. Kocyigit, E. Guler / Journal of Organometallic Chemistry 696 (2011) 3106e3112
Table 1
Elemental analysis, magnetic and physical properties of the compounds.
Complex
Color
meff (B.M.)
298 ꢁC
m.p (ꢁC)
Yield (%)
Found (Calcd.) (%)
C
N
H
M
5a
5b
6a
6b
7a
7b
Orange
Brown-green
Tile red
Red-green
Tile red
Brown-green
1.98
3.42
1.79
3.42
1.85
3.52
312
387a
350a
>400
279
80
65
64
61
78
67
62.26 (62.20)
62.76 (62.71)
64.14 (61.10)
64.61 (64.59)
66.68 (66.60)
67.15 (67.20)
5.81 (6.85)
5.86 (5.80)
5.34 (5.31)
5.38 (5.34)
5.02 (4.98)
5.05 (5.00)
3.76 (3.74)
3.79 (3.75)
4.61 (4.64)
4.65 (4.69)
3.97 (3.95)
4.00 (4.05)
11.58 (11.55)
10.87 (10.80)
10.65 (10.60)
9.99 (9.93)
10.00 (9.90)
9.38 (9.34)
394
a
Decomposition.
Table 2
Characteristic FT-IR bands (cmꢀ1) of the prepared Fe/Cresalophen complexes.
The FT-IR spectra of the complexes have different absorption bands,
compared with that of the ligands. The vibrations of the carboxylic
acid C]O of 5, 6 and 7 ligands have been observed at 1735,1740 and
1707 cmꢀ1, respectively. In the complexes, these bands are,
however, shifted to lower or higher frequencies indicating that the
oxygen atoms of 5, 6 and 7 are coordinated to the ligand complexes.
The C]O band in complexes 5a, 5b, 6a, 6b, 7a and 7b shift to 1738,
1715, 1723, 1730, 1750 and 1753 cmꢀ1 depending on the electron
density of the C]O group, respectively. Also, in the FT-IR analysis of
the complexes, the bands in the 556e533 and 465e478 cmꢀ1 range
can be attributed to the MeN and MeO stretching modes [31].
The thermal stability of the prepared complexes was evaluated
by thermal gravimetric analysis (TG). TG curve of complex 5b was
depicted in Fig. 5. It was found that 5b undergoes a three-step
thermal degradation. The first step (50e200 ꢁC) is due to the loss
of moisture. At the second and third decomposition step, CO2 and
C6H6 groups left from the main structure at 250e450 ꢁC and
450e850 ꢁC, respectively [32]. Although the total weigh lost was
theoretically calculated to be 42.33%, it was observed experimen-
tally to be 37.11%. Moreover, the thermal behaviors of the obtained
other complexes are summarized in Table 3.
Compounds
OH
C]O
CeN
CeCar
CeHaliph
5a
5b
6a
6b
7a
7b
3438
3392
3446
3430
3430
3407
1738
1715
1723
1730
1750
1753
1607
1623
1623
1628
1623
1630
1584
1605
1615
1600
1605
1600
3076
3056
3069
3046
3053
3069
3.52 B.M. for 7. It is seen that the [{Fe(salophen)}2O] and [{Cr(sa-
lophen)}2O] containing compounds are represented by the elec-
tronic structure of t2g5eg0 and t2g3eg0. The magnetic data for the
[{Fe(salophen)}2O] and [{Cr(salophen)}2O] complexes demonstrate
well agreement with the d5 and d3 metal ion in an octahedral
structure. This consequence is supported by the results of the
elemental analyses suggesting that these complexes have also an
octahedral structure [30,31].
The characteristic FT-IR bands for the prepared Fe/Cr(III)esalo-
phen complexes (5ae5b, 6ae6b and 7ae7b) were given Table 2.
Fig. 5. TG curve of compound 5b.

O. Kocyigit, E. Guler / Journal of Organometallic Chemistry 696 (2011) 3106e3112
3111
Table 3
Thermal analysis of the prepared Fe/Cresalophen complexes.
4.2. Synthesis of compounds 2, 3 and 4
2,3,6,7,10,11-hexahydroxytriphenylene 1 (HHTP) was prepared
according to the reported procedure [34]. To give compounds 2, 3
and 4, the mixture of HHTP (1 mmol) and K2CO3 (8 mmol) in
50.0 mL of dry acetone was refluxed for 1 h. Then, ethyl bromoa-
cetate, methyl 5-bromovalerate or methyl (4-bromomethyl)
benzoate (8 mmol) upon this solution were added and refluxed for
24 h. The reaction was monitored by TLC. The resulting solution was
allowed to warm up to room temperature. At the end of the reac-
tion, the reaction mixture was filtered and the organic layer was
removed under reduced pressure. The observed solid product was
dissolved in CHCl3 and washed twice with 0.2 N HCl and water. The
combined organic phase was dried over Na2SO4 filtered, and
concentrated under reduced pressure to afford the desired pure
product (2, 3 and 4).
Complexes
TG range (ꢁC)
Fragments
Weight loss found
(Calcd.) (%)
5a
50e100 ꢁC
200e425 ꢁC
500e875 ꢁC
50e200 ꢁC
250e450 ꢁC
450e850 ꢁC
50e150 ꢁC
200e450 ꢁC
575e800 ꢁC
50e150 ꢁC
250e475 ꢁC
600e700 ꢁC
750e850 ꢁC
50e150 ꢁC
250e375 ꢁC
400e700 ꢁC
50e140 ꢁC
200e425 ꢁC
450e750 ꢁC
Moisture
CO2
C6H6 groups
Moisture
CO2
C6H6 groups
Moisture
H2, CO2
C2H4, C6H6, CN
Moisture
H2, CO2
45.58 (42.34) (%)
42.33 (37.11) (%)
32.03 (35.67) (%)
29.75 (32.17) (%)
5b
6a
6b
C2H4
CN, C6H6 groups
Moisture
CO2
CN, C6H6
Moisture
CO2
7a
7b
41.75 (45.13) (%)
40.62 (45.43) (%)
Compound 2; Yield 75%; mp: 154 ꢁC; FT-IR: 1750 (C]O) cmꢀ1
;
1H NMR (CDCl3):
d
1.32 (t, 18H, eCH2CH3), 4.33 (q, 12H, eCH2CH3),
4.91 (s, 12H, OCH2), 7.69 (s, 6H, AreH). Anal. Calcd for C42H48O18: C,
59.99%; H, 5.75%. Found: C, 60.10%; H, 5.62%.
CN, C6H6
Compound 3; Yield 60% (oil); FT-IR: 1755 (C]O) cmꢀ1; 1H NMR
(CDCl3): d 1.65e1.75 (m,12H, eCH2),1.88e2.02 (m,12H, eCH2), 2.49
3. Conclusion
(t, 12H, CH2CO), 3.68 (s, 18H, OCH3), 4.25 (t, 12H, OCH2), 7.81 (s, 6H,
AreH). Anal. Calcd for C54H72O18: C, 64.27%; H, 7.19%. Found: C,
63.02%; H, 7.12%.
The design and synthesis of novel the carboxylic acid derivatives
of triphenylene as ligand and their Fe/Cr(III)esalophen complexes
have been demonstrated in this report. These complexes are the
examples of complexes bridged by carboxylate anions to the iron
and chromium centers. Their structures were characterized by
means of elemental analysis, 1H NMR, FT-IR spectroscopy, thermal
analysis and magnetic susceptibility measurements. The magnetic
data for the complexes show well agreement with the d5 and d3
metal ion in an octahedral structure. It may be possible to try to test
these triphenylene based Fe/Cresalophen complexes as antibacte-
rial, antitubercular, antifungal and anticoagulant activity. In other
words, further studies on the complexation reactions and catalytic
activity of the prepared complexes on model reactions will be
carried out soon.
Compound 4; Yield 72%; mp: 105 ꢁC; FT-IR: 1723 (C]O) cmꢀ1
;
1H NMR (CDCl3):
d 3.94 (s, 18H, eOCH3), 5.43 (s, 12H, OeCH2), 7.52
(d, 12H, AreH), 8.09 (d, 12H, AreH), 8.10 (s, 6H, AreH). Anal. calcd.
for C72H60O18: C, 71.28%; H, 4.98%. Found: C, 72.02%; H, 4.82%.
4.3. Synthesis of compound 5, 6 and 7
A mixture of compounds 2, 3 or 4 (1.0 mmol) and 15% aqueous
sodium hydroxide (13 mL, 6 mmol) in ethanol (50 mL) was refluxed
for 24 h. Ethanol was distilled off and the residue was diluted with
water (50 mL). HCl (3 mol Lꢀ1) was added to the resulting
suspension until pH 1 was reached. The solid was filtered off and
dissolved in chloroform (50 mL). This solution was washed with
HCl (3 mol Lꢀ1, 30 mL) and brine (30 mL). The organic layer was
dried over MgSO4 and concentrated to afford compounds 5, 6 or 7.
4. Experimental
Compound 5; Yield 85%; mp: 255 ꢁC; FT-IR: 1735 (C]O) cmꢀ1
;
4.1. Materials and methods
1H NMR (DMSO):
d
5.01 (s, 12H, OCH2), 8.00 (s, 6H, AreH) Anal.
Calcd for C30H24O18: C, 53.58%; H, 3.60%. Found: C, 54.10%; H, 3.62%.
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(salophen)}2O] and [{Cr(salo-
phen)}2O] were prepared according to previously published
methods [30,33]. 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 (TG) was carried out with Seteram thermog-
ravimetric analyzer. The sample weight was 15e16 mg. Analysis
was performed from room temperature to 900 ꢁC at heating rate of
15 ꢁC/min in argon atmosphere with a gas flow rate of 20 mL/min.
The elemental analysis for the ligand and the bridged complexes
were carried out at on a HewlettePackard 185 analyzer. FT-IR
spectra were recorded using a Mattson-1000 FT-IR using KBr
pellets. Magnetic susceptibilities of metal complexes were deter-
mined using a Sheerwood Scientific MX Gouy magnetic suscepti-
bility apparatus carried out using the Gouy method with Hg
Compound 6; Yield 50% (oil); FT-IR: 1740 (C]O) cmꢀ1; 1H NMR
(DMSO):
d 1.72e1.84 (m, 24H, eCH2), 2.34 (t, 12H, CH2CO), 4.23 (t,
12H, OCH2), 7.95 (s, 6H, AreH). Anal. Calcd for C48H60O18: C, 62.33%;
H, 6.54%. Found: C, 62.12%; H, 6.23%.
Compound 7; Yield 60%; mp: 340 ꢁC (decomp.); FT-IR: 1707 (C]
O) cmꢀ1 1H NMR (DMSO):
; d 5.47 (s, 12H, OeCH2), 7.66e7.73 (m,
12H, AreH), 7.94 (s, 6H, AreH), 7.91e7.98 (m, 12H, AreH), Anal.
Calcd for C66H48O18: C, 70.21%; H, 4.29%. Found: C, 70.02%; H, 4.31%.
4.4. Preparation of the (salophen)-bridged Fe/Cr (III) capped
complexes (5a,5b, 6a,6b, 7a,7b)
A solution of compounds 5, 6 or 7 (1 mmol) and [{Fe/Cr(salo-
phen)}2O] (3.0 mmol) in 80 mL of absolute ethanol were refluxed
for 4 h. The mixture was allowed to cool to room temperature. Then
the mixture was filtered off, washed with ethanol and dried in
vacuum. Elemental analysis, magnetic and physical properties of
the synthesized complexes are given in Table 1.
[Co(SCN)4] as calibrant. The effective magnetic moments, meff, per
1/2
metal atom was calculated from the expression: meff ¼ 2.84$(cM
)
,
where cM is the molar susceptibility.

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O. Kocyigit, E. Guler / Journal of Organometallic Chemistry 696 (2011) 3106e3112
[13] E. Guler, H.C. Sevindir, S. Kurbanov, R. Mirzaoglu, Synth. React. Inorg. Met. Org.
Acknowledgment
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K. Natarajan, Spectrochim. Acta Part A 68 (2007) 50e54.
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We thank the Scientific Research Projects Foundation of Selcuk
University (SUBAP-Grant Number 2006-06101042) for financial
supportof this workproduced froma partof O. Kocyigit’s PhDThesis.
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