New soluble peripherally tetra-substituted Co(II), Fe(II) phthalocyanines: Synthesis, spectroscopic characterization and their catalytic activity in cyclohexene oxidation

Article abstract of DOI:10.1016/j.dyepig.2013.02.021

New 4-{2-[3-(diethylamino)phenoxy]ethoxy}phthalonitrile 3 was obtained from 2-[3-(diethylamino)phenoxy]ethanol 1 and 4-nitrophthalonitrile 2 with K ₂CO₃ in DMF at 50 C. The novel iron(II) and cobalt(II) phthalocyanine complexes 4 and

Full text of DOI:10.1016/j.dyepig.2013.02.021

Dyes and Pigments 98 (2013) 255e262
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Dyes and Pigments
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New soluble peripherally tetra-substituted Co(II), Fe(II)
phthalocyanines: Synthesis, spectroscopic characterization and their
catalytic activity in cyclohexene oxidation
*
ꢀ
ꢀ
Ece Tugba Saka, Dilek Çakır, Zekeriya Bıyıklıoglu , Halit Kantekin
Department of Chemistry, Faculty of Science, Karadeniz Technical University, 61080 Trabzon, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
New 4-{2-[3-(diethylamino)phenoxy]ethoxy}phthalonitrile 3 was obtained from 2-[3-(diethylamino)
phenoxy]ethanol 1 and 4-nitrophthalonitrile 2 with K2CO3 in DMF at 50 ꢀC. The novel iron(II) and
cobalt(II) phthalocyanine complexes 4 and 5 were prepared by the reaction of the phthalonitrile de-
rivative 3 with n-pentanol in a standard Schlenk tube in the presence of 1,8-diazabicyclo[5.4.0]undec-7-
ene (DBU). These new phthalocyanine complexes were characterized by the spectroscopic methods (IR,
1H NMR, 13C NMR, UVevis and mass spectroscopies) Complexes 4 and 5 are employed as catalyst for the
oxidation of cyclohexene using tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA),
aerobic oxygen and hydrogen peroxide (H2O2) as oxidant. It is observed that iron(II) phthalocyanine
complex can selectively oxidize cyclohexene to give 2-cyclohexene-1-ol as major product, and 2-
cyclohexene-1-one and cyclohexene oxide are minor products. TBHP was found to be the best oxidant
since the minimal destruction of the catalyst, higher selectivity and conversion were observed in the
products.
Received 3 January 2013
Received in revised form
12 February 2013
Accepted 22 February 2013
Available online 16 March 2013
Keywords:
Phthalocyanine
Iron
Cobalt
Cyclohexene
Oxidation
TBHP
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
chains and molecules were studied for diverse purposes [5e15]. The
solubility of phthalocyanines is important for many applications.
Phthalocyanine is a planar 18
p
-electron heterocyclic aromatic
When functional groups such as crown ethers, alkyl, alkoxy, alkylthio,
tertiary butyl groups bound in the periferal benzene rings of the Pc
structure, solubility of phthalocyanines can improve in protic or non-
protic solvents.
systemwith alternating nitrogenecarbon atom ring structure derived
from porphyrin. Phthalocyanines have been known for more than 70
years and have been extensively used as colourants [1e3]. Because of
the low cost and easiness in construction, organic materials are
considered a perfect alternative to inorganic ones. The most versatile
organic materials are porphyrin and phthalocyanine dyes that can
find practical applications in various fields of technology and science
for example: photonics (new organic solar cells, molecular optoelec-
tronics, non-linear optical materials), photomedicine (photodynamic
diagnosis and therapy of cancer) and photosynthesis (in modelling of
electron transfer and charge separation phenomena in reaction cen-
tres) especially due to their high absorption coefficient, easy molec-
ular structure modification by chemical procedure and efficient
photoactivity as photoconverters [4]. A series of free-based porphy-
rins and phthalocyanine dyes and their derivatives complexed with
variousmetallic ions andsubstituted withdifferentperipheralgroups,
Phthalocyanine complexes of transition metals are attractive as
potential oxidation catalysts because of their rather cheap and facile
preparation in a large scale and their chemical and thermal stability.
Their macrocyclic structure resembles that of porphyrin complexes
widely used by nature in the active sites of oxygenase enzymes [16].
Not surprisingly, porphyrin catalytic chemistry is quite well-
documented [17e20]. Extensive efforts have been directed at
modelling catalytic activity using synthetic iron and manganese
porphyrin complexes to elucidate the mechanism of dioxygen
activation and the structure(s) of reactive intermediate(s). Mecha-
nisms of catalytic oxidation of various organic substrates including
alkanes and olefins by cytochrome P-450 and its chemical models
based on porphyrin metal complexes were proposed, evidenced
and now generally accepted. Several intermediate active species in
catalytic cycle were postulated, identified and characterized by
different spectroscopic techniques. There is a stark contrast be-
tween state of art of porphyrin and phthalocyanine oxidation
* Corresponding author. Tel.: þ90 462 377 3664; fax: þ90 462 325 3196.
ꢀ
E-mail address: zekeriya_61@yahoo.com (Z. Bıyıklıoglu).
0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.dyepig.2013.02.021

256
E.T. Saka et al. / Dyes and Pigments 98 (2013) 255e262
chemistry. Although phthalocyanine complexes have been actively
investigated as oxidation catalysts [21e25] their catalytic chemistry
is practically not developed in terms of mechanisms and active
species involved in these catalytic oxidations [25e29].
mp: 95e96 ꢀC. IR (KBr pellet), vmax/cmꢂ1: 3071 (AreH), 2974e2877
(Aliph. CeH), 2229 (C^N), 1613, 1595, 1570, 1499, 1449, 1373, 1355,
1319, 1255, 1221, 1178, 1145, 1081, 1052, 1024, 979, 890, 841, 829, 761,
691, 523. 1H NMR. (CDCl3), (
d
:ppm): 7.74 (d, 1H, AreH), 7.35e7.24 (m,
2H, AreH), 7.13 (t, 1H, AreH), 6.36 (d, 1H, AreH), 6.22 (m, 2H, AreH),
4.39 (m, 4H, eCH2eO), 3.35 (q, 4H, eCH2eN), 1.15 (t, 6H, eCH3). 13
NMR. (CDCl3), ( :ppm): 161.74, 159.38, 149.09, 135.12, 129.94, 119.71,
Additionally, iron and cobalt phthalocyanine complexes have
been applied as catalyst for selective oxidation of olefins [30]. The
oxidation of products such as aldehyde, ketones and alcohols are
widely used in chemical industries and academic field. The oxida-
tion products of cyclohexene that are studied in this work are 2-
cyclohexene-1-one, 2-cyclohexene-1-ol and cyclohexene oxide.
These products are great importance to industrial processes as well
as fine chemical syntheses. Different groups substituted phthalo-
cyanines (especially electron attracting groups such as halogenated,
phenyl groups) have been largely studied for their ability in
oxidation of cyclohexene [31].
Fe(II) and Co(II) phthalocyanines are readily available oxidation
catalysts and found to transfer oxygen from various oxygen donors to
alkanes, alkenes, phenols and thiols in numerous studies [32e45]. In
this work, we have been synthesized new iron(II) (4) and cobalt(II) 5
phthalocyanine substituted with four 4-{2-[3-(diethylamino)phe-
noxy]ethoxy} groups. We have also reported on the comparing of
these complexes 4 and 5 as homogeneous catalysts for the oxidation
of cyclohexene with the aim of improving product selectivity,
increasing the range of products and compare their catalytic activity.
C
d
119.53, 117.22, 115.63, 115.20, 107.33, 105.55, 99.95, 98.68, 67.70,
65.62, 44.27, 12.48. MS (ESþ), (m/z): 336 [MþH]þ.
2.3.2. Iron(II) phthalocyanine (4)
4-{2-[3-(Diethylamino)phenoxy]ethoxy}phthalonitrile 1 (0.2 g,
0.59 ꢁ 10ꢂ3 mol), anhydrous Fe(CH3COO)2 (0.052 g, 0.29 ꢁ 10ꢂ3 mol)
and 0.003 L of n-pentanol were placed in a standard Schlenk tube
in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)
(0.36 ꢁ 10ꢂ3 mL, 0.24 ꢁ 10ꢂ3 mol) under a nitrogen atmosphere and
held at reflux temperature (160 ꢀC) for 24 h. After cooling to room
temperature, the reaction mixture was precipitated by adding it
drop-wise into ethanol. The crude product was collected by filtration
and washed with diethyl ether and then dried. Purification was
achieved using column chromatography with basic alumina as col-
umn material and CHCl3/MeOH (100:2) solvent system as eluent.
Yield: 0.145 g (70%). IR (KBr pellet) vmax/cmꢂ1: 3069 (AreH), 2964e
2868 (Aliph. CeH), 1608, 1571, 1498, 1450, 1396, 1339, 1275, 1213,
1128,1071, 957, 823, 746, 685. 1H NMR (CDCl3), (
d:ppm): 7.99 (m, 8H,
2. Experimental
AreH), 7.23 (m, 8H, AreH), 6.38 (m,12H, AreH), 4.53 (m,16H, eCH2e
O), 3.32 (m, 16H, eCH2eN), 1.14 (m, 24H, eCH3). UVevis (THF),
2.1. Materials
lmaks(log
3
)nm: 596 (4.21), 652 (4.47). MS (ESþ), (m/z): 1436 [MþK]þ.
All reactions were carried under a dry nitrogen atmosphere
using Standard Schlenk techniques. All chemicals, solvents, and
reagents were of reagent grade quality and were used as purchased
from commercial sources. All solvents were dried and purified as
described by reported procedure [46]. 4-Nitrophthalonitrile 2 [47],
2-[3-(diethylamino)phenoxy]ethanol 1 [48] were prepared ac-
cording to the literature procedure.
2.3.3. Cobalt(II) phthalocyanine (5)
4-{2-[3-(Diethylamino)phenoxy]ethoxy}phthalonitrile
(1)
(0.3 g, 0.89 ꢁ 10ꢂ3 mol), anhydrous CoCl2 (0.058 g, 0.44 ꢁ 10ꢂ3 mol)
and 0.003 L of n-pentanol were placed in a standard Schlenk tube in
the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)
(0.55 ꢁ 10ꢂ3 L, 0.36 ꢁ 10ꢂ3 mol) under a nitrogen atmosphere and
held at reflux temperature (160 ꢀC) for 24 h. After cooling to room
temperature, the reaction mixture was precipitated by adding it
drop-wise into ethanol. The crude product was collected by filtra-
tion and washed with diethyl ether and then dried. Purification was
achieved using column chromatography with basic alumina as
column material and CHCl3/MeOH (100:2) solvent system as eluent.
Yield: 128 mg (41%). IR (KBr tablet) vmax/cmꢂ1: 3069 (AreH), 2966e
2869 (Aliph. CeH), 1717, 1610, 1572, 1499, 1480, 1374, 1278, 1214,
2.2. Equipment
The IR spectra were recorded on a Perkin Elmer 1600 FT-IR
spectrophotometer using KBr pellets. 1H and 13C NMR spectra
were recorded on a Varian Mercury 200 MHz spectrometer in
CDCl3. Chemical shifts were reported (d) relative to Me4Si as in-
ternal standard. Mass spectra were measured on a Micromass
Quatro LC/ULTIMA LC-MS/MS spectrometer and Agilent 1100 Series
spectrometer LC/MSD. Melting points were measured on an elec-
trothermal apparatus and are uncorrected. Optical spectra in the
UVevis region were recorded with a Perkin Elmer Lambda 25
spectrophotometer. GC Agilent Technologies 7820A equipment
1131, 1095, 1069, 976, 824, 752, 687. UVevis (THF), lmaks(log )nm:
3
329 (4.65), 607 (4.19), 666 (4.57). MS (ESþ), (m/z): 1401 [MþH]þ.
2.3.4. General procedure for the oxidation of cyclohexene
Experiments were carried out in a thermostated Schlenk vessel
equipped with a condenser and stirrer. The solution of cyclohexene
and catalyst in solvent was purified with bubbling nitrogen gas to
remove the oxygen. A mixture of cyclohexene (0.71 ꢁ 10ꢂ3 mol),
catalyst (3.57 ꢁ 10ꢂ6 mol) and solvent (0.01 L) was stirred in a
Schlenk vessel for few minutes at room temperature. The oxidant
TBHP (1.78 ꢁ 10ꢂ3 mol) was then added and the reaction mixture
was stirred for the desired time. The samples (0.005 L) were taken
at certain time intervals. Each sample was injected at least twice in
(30 m ꢁ 0.32 mm ꢁ 0.50
mm DB Wax capillary column, FID detector)
was used GC measurements.
2.3. Synthesis
2.3.1. 4-{2-[3-(Diethylamino)phenoxy]ethoxy}phthalonitrile (3)
4-Nitrophthalonitrile 2 (1.65 g, 0.009 mol) was dissolved in
anhydrous DMF (0.022 L) under nitrogen and 2-[3-(diethylamino)
phenoxy]ethanol 1 (2 g, 0.009 mol) was added. After stirring for
10 min, finely ground anhydrous K2CO3 (3.96 g, 0.028 mol) was
added in portions over 2 h with stirring. The reaction mixture was
stirred at 60 ꢀC for 96 h under nitrogen. Then water (0.1 L) was added
and the aqueous phase extracted with chloroform (3 ꢁ 0.1 L). The
combined extracts were treated with water and dried over anhy-
drous magnesium sulphate and then filtered. Solvent was evaporated
and the product was crystallized from ethanol. Yield: 1.41 g (44%),
the GC, 1 mL each time. Formation of products and consumption of
substrates were monitored by GC.
3. Results and discussion
3.1. Synthesis and characterization
Fig. 1 shows a brief schematic for the synthesis of peripherally
tetra-substituted iron and cobalt phthalocyanine complexes 4, 5. In

E.T. Saka et al. / Dyes and Pigments 98 (2013) 255e262
257
N
OH
O
1
CN
i
N
O2N
CN
O
CN
O
3
CN
2
ii
N
N
O
O
Fig. 3. UVevis spectrum of iron(II) phthalocyanine
(Concentration ¼ 10 ꢁ 10ꢂ6 mol dmꢂ3).
4
in different solvents.
O
O
N
N
N
N
the 1H NMR spectra of compound 3 the aromatic protons appeared
at 7.74 (d), 7.35e7.24 (m), 7.13 (t), 6.36 (d), 6.22 (m) ppm and
aliphatic protons appeared at 4.39 (m), 3.35 (q), 1.15 (t) ppm. The
13C NMR spectra of compound 3 indicated carbon atoms between at
161.74e12.48 ppm. Also nitrile carbon atoms for compound 3
was observed 115.63, 115.20 ppm. In the mass spectra of compound
3 the presence of molecular ion peak at m/z ¼ 336 [MþH]þ,
confirmed the proposed structures.
Cyclotetramerization of the dinitrile derivative 3 to the iron(II)
and cobalt(II) phthalocyanines 4 and 5 were confirmed by the
disappearance of the sharp C^N vibration of 2229 cmꢂ1. The 1H
NMR spectrum of peripherally tetra-substitued iron(II) phthalocy-
anine 4 was as expected. The 1H NMR spectrum of iron(II) phtha-
locyanine 4 indicated the aromatic protons at 7.99, 7.23, 6.38 ppm
and aliphatic protons at 4.53, 3.32, 1.14 ppm. The 1H NMR spectrum
of cobalt phthalocyanine 5 could not be taken due to the para-
magnetic cobalt(II) centres [49]. In the mass spectrum of iron and
cobalt phthalocyanines 4 and 5, the presence of molecular ion
peaks at m/z 1436 [MþK]þand 1401 [MþH]þ respectively,
confirmed the proposed structures.
The metallophthalocyanines display typical electronic spectra
with two strong absorption regions, one of them in the UV region
at about 300e350 nm (B band) and the other one in the visible
region at 600e700 nm (Q band). The electronic absorption spectra
of the iron and cobalt phthalocyanines 4 and 5, in THF at room
temperature are shown in Fig. 2. UVevis spectra of iron phthalo-
cyanine 4 (in THF) vibronic Q bands appeared at 652, 596 nm. UVe
vis spectra of cobalt phthalocyanine 5 (in THF) vibronic Q bands
appeared at 666, 607 nm, while the split B band remained at
329 nm.
N
M
N
N
N
O
O
O
O
N
4
5
Compound
M
N
Fe Co
Fig. 1. The synthetic route of the phthalonitrile, cobalt phthalocyanine and iron
phthalocyanine. Reagents and conditions: (i) dry DMF, K2CO3, 60 ꢀC, 96 h; (ii) n-
pentanol, DBU, 160 ꢀC, CoCl2, Fe(CH3COO)2.
dry DMF, using K2CO3 as the base, phthalonitrile derivative 3 was
synthesized through base-catalyzed aromatic displacement of 4-
nitrophthalonitrile with 2-[3-(diethylamino)phenoxy]ethanol. The
reaction was carried out at 60 ꢀC under N2 atmosphere for 96 h.
Cyclotetramerization of the phthalonitrile derivative 3 to the
peripherally tetra-substituted iron(II) and cobalt(II) phthalocya-
nines 4 and 5 were accomplished in the presence of anhydrous
Fe(CH3COO)2, CoCl2 in n-pentanol and DBU and the crude product
chromatographed on basic alumina. The structures of the target
compounds were confirmed using UVevis, IR, 1H NMR, 13C NMR,
MS spectroscopic data. The analyses are consistent with the pre-
dicted structures as shown in the experimental section.
The IR spectra clearly indicated the formation of compound 3
with the appearance of absorption band at 2229 cmꢂ1 (C^N). In
Fig. 4. UVevis spectrum of iron(II) phthalocyanine
(Concentration ¼ 10 ꢁ 10ꢂ6 mol dmꢂ3).
4 in different solvents.
Fig. 2. UVevis spectrum in THF for complex 4 and 5.

258
E.T. Saka et al. / Dyes and Pigments 98 (2013) 255e262
Fig. 5. UVevis spectrum of cobalt(II) phthalocyanine
(Concentration ¼ 10 ꢁ 10ꢂ6 mol dmꢂ3).
5
in different solvents.
Fig. 7. UVevis spectrum of cobalt phthalocyanine 5 in DMSO at different concentra-
tions, 12 ꢁ 10ꢂ6, 10 ꢁ 10ꢂ6, 8 ꢁ 10ꢂ6, 6 ꢁ 10ꢂ6, 4 ꢁ 10ꢂ6, 2 ꢁ 10ꢂ6 mol dmꢂ3
.
3.2. Aggregation studies
under similar experimental conditions in DMF (Tables 1e4). In a
typical catalytic reaction, Schlenk tube was charged with cyclo-
hexene (0.71 ꢁ10ꢂ3 mol), complex 4 (3.58 ꢁ 10ꢂ6 mol) or complex 5
(3.57 ꢁ 10ꢂ6 mol) and TBHP (1.78 ꢁ 10ꢂ3 mol) in DMF (0.01 L) and
refluxed at 90 ꢀC with 900 rpm stirring. Control experiments show
that cyclohexene oxidation with TBHP, m-CPBA and H2O2 did not
occur in the absence of the catalyst under the same reaction con-
dition, confirming that the catalyst plays a prominent role in the
oxidation process. As shown in Tables 1e4, comparative studies of
the catalytic activity of 4 and 5 for oxidation of cyclohexene revealed
that both complexes are active catalysts in DMF. The oxidation re-
actions gave cyclohexenol as the main product and 2-cyclohexen-1-
one and cyclohexene epoxide in small yields which are evidently
identified using gas chromatography by both spiking and com-
parison with standards (Fig. 8). In order to obtain maximum con-
version of cyclohexene, the catalytic reactions were carried out
varying the reaction temperature, time and different oxidants,
subst./cat. ratio.
Aggregation is usually depicted as a coplanar association of rings
progressing from monomer to dimer and higher order complexes. It
is dependent on the concentration, nature of the solvent, nature of
the substituents, complexed metal ions and temperature [50e52].
In this study, the aggregation behaviour of the iron and cobalt
phthalocyanine complexes 4 and 5 are investigated in different
solvents (CHCl3, CH2Cl2, THF, DMF, DMSO, EtOAc) (Figs. 3 and 4 for
complex 4, Figs. 5 and 6 for complex 5). While iron phthalocyanine
4 showed little aggregation in CHCl3, CH2Cl2, THF, DMF, EtOAc, full
aggregation in DMSO, the complex 5 showed little aggregation only
in EtOAc. Also, cobalt phthalocyanine 5 did not show any aggre-
gation in CHCl3, CH2Cl2, THF, DMF, DMSO.
The aggregation behaviour of cobalt phthalocyanine complex 5
was also investigated at different concentrations in DMSO. In
DMSO, as the concentration was increased, the intensity of ab-
sorption of the Q band also increased and there were no new bands
(normally blue shifted) due to the aggregated species for all
phthalocyanines (Fig. 7). BeereLambert law was obeyed for all of
the compounds in the concentrations ranging from 12 ꢁ 10ꢂ6 to
The results of the catalytic oxidation of cyclohexene by TBHP in
the presence of 4 and 5 are shown in Fig. 9a and b, which shows the
variation of product yield with reaction time. Higher yield was
obtained for cyclohexenol than cyclohexenone and cyclohexene
epoxide for both catalysts. The yields for cyclohexenone and
cyclohexene epoxide were nearly similar for catalysts 4 and 5. The
yield of the three products increased, but level off with time. This
2 ꢁ 10ꢂ6 mol dmꢂ3
.
3.3. Catalytic studies
3.3.1. Oxidation of cyclohexene with 4 and 5
The catalytic activity and selectivity of 4 and 5 have been studied
for the oxidation of cyclohexene with TBHP as the model compound
Table 1
Amount of substrate effect of cyclohexene oxidation with complex 4 and 5.
Catalyst Subs./Cat. Alcohola Ketoneb Epoxidec Tot. Conv. TONd TOFe
(%)
(hꢂ1
)
4
5
4
5
4
5
4
5
4
5
4
5
200/1
400/1
68
60
63
57
54
48
45
39
38
32
33
28
23
20
16
12
15
10
13
9
11
8
10
6
20
15
11
9
10
7
9
5
7
5
99
85
90
78
79
65
67
53
56
45
49
38
196
169
356
310
470
387
531
421
555
447
583
453
65
56
119
103
156
129
177
140
185
149
194
151
600/1
800/1
1000/1
1200/1
6
4
Conversion was determined by GC.
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexenoxide.
b
c
d
Fig. 6. UVevis spectrum of cobalt(II) phthalocyanine
(Concentration ¼ 10 ꢁ 10ꢂ6 mol dmꢂ3).
5
in different solvents.
TON ¼ mole of product/mole of catalyst.
e
TOF ¼ mole of product/mole of catalyst ꢁ time.

E.T. Saka et al. / Dyes and Pigments 98 (2013) 255e262
259
Table 2
Different oxidant effect of cyclohexene oxidation with complex 4 and 5.
Table 4
Temperature effect of cyclohexene oxidation with complex 4 and 5.
Catalyst Oxidant
Alcohola Ketoneb Epoxidec Tot. Conv. TONd TOFe
Catalyst T (ꢀC). Alcohola Ketoneb Epoxidec Tot. Conv. TONd TOFe
(%)
(hꢂ1
)
(%)
(hꢂ1
)
4
5
4
5
4
5
4
5
TBHP
63
57
26
23
49
45
e
16
12
14
11
15
10
e
11
9
7
9
11
6
90
78
47
43
75
61
e
356
310
186
171
297
242
e
119
103
62
57
99
80
e
4
5
4
5
4
5
4
5
25
50
70
90
25
22
40
38
52
49
68
60
15
11
17
11
19
12
23
20
8
9
48
42
68
59
83
71
99
85
95
83
31
27
44
39
54
47
65
56
H2O2
11
10
12
10
20
15
134
117
164
141
196
169
m-CPBA
Free oxidant
e
e
e
e
e
e
e
Conversion was determined by GC.
Conversion was determined by GC.
a
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexenoxide.
TON ¼ mole of product/mole of catalyst.
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexenoxide.
TON ¼ mole of product/mole of catalyst.
b
b
c
c
d
d
e
e
TOF ¼ mole of product/mole of catalyst ꢁ time.
TOF ¼ mole of product/mole of catalyst ꢁ time.
O
OH
level off is most likely due to the degradation of the FePc and CoPc
catalyst by oxidant, with time.
Oxidant
O
Catalyst (MPc)
To examine the effect of substrate to iron and cobalt, the molar
ratio was carried out in the range of 200e1200 while other pa-
rameters were kept constant. The experimental conditions were
90 ꢀC, 1.78 ꢁ 10ꢂ3 mol TBHP, 0.01 L DMF for 3 h. The results are
shown in Table 1. As expected, decrease the substrate catalyst molar
ratio, the reaction rate increases. At each different substrate/cata-
lyst ratio the oxidation of cyclohexene gives same main product (2-
cyclohexene-1-ol) with selectivity of 68% and 60% for 4 and 5,
respectively.
The nature and the relative yields of the products formed by
catalytic oxidation of cyclohexene using porphyrins vary consid-
erably depending on the catalyst and oxidant. When iron porphyrin
containing nitrate or perchlorate as axial ligands was employed for
the oxidation of cyclohexene using chloroperoxybenzoic acid, large
yields of cyclohexene oxide were obtained (68e78%), but when
chloride axial ligands were employed using the same oxidants, the
yields of cyclohexene oxide were less than 2% [53]. Higher yields of
cyclohexene oxide relative to the other products were observed for
most porphyrins using oxidants such as chloroperoxybenzoic acid
or iodosylbenzene [54,55]. However, photooxygenation of cyclo-
hexene using titanium porphyrins resulted in the formation of
cyclohexene hydroperoxide as a major product, with cyclohexene
oxide being one of the side products [56]. On the other hand, when
cobalt phthalocyanines were used as catalyst on cyclohexene
oxidation with TBHP oxidant, 2-cyclohexene-1-ol was obtained as
Cyclohexene
2-cyclohexene-1-one
2-cyclohexene-1-ol
cyclohexenoxide
Fig. 8. Product formed through oxidation of cyclohexene by TBHP, m-CPBA and H2O2
in the presence of complex 4 and 5.
main product (55% and 67%) [57]. This work shows that the cata-
lysts 4 and 5 with TBHP as oxidant favoured the formation of 2-
cyclohexene-1-ol to the rest of the products.
The effect of oxygen source on the reaction rate of cyclohexene
oxidation was investigated for TBHP, m-CPBA, aerobic oxygen and
H2O2. With the exception of the oxidant, all the experimental
conditions were kept constant for the catalytic reactions. The data
are given in Table 2 and Fig. 10. There is no conversion for both
complexes when the aerobic oxygen was used as oxidant.
2-cyclohexen-1-ol
2-cyclohexen-1-on
cyclohexen oxide
80
70
60
50
40
30
20
10
0
(a)
Table 3
0
50
100
Time (min)
150
200
Amount of oxidant effect of cyclohexene oxidation with complex 4 and 5.
Catalyst Oxidant/ Alcohola Ketoneb Epoxidec Tot. Conv. TONd TOFe
2-cyclohexen-1-ol
2-cyclohexen-1-on
cyclohexen oxide
catalyst
(%)
(hꢂ1
)
70
4
5
4
5
4
5
4
5
4
5
300/1
33
29
42
39
63
57
35
30
27
21
19
16
22
17
16
12
19
17
10
8
14
9
15
14
11
9
14
10
5
65
54
79
70
90
78
68
57
42
35
257
214
313
278
356
310
269
226
166
139
85
71
104
92
119
103
89
75
55
46
(b)
60
50
40
30
20
10
0
400/1
500/1
600/1
900/1
6
Conversion was determined by GC.
a
0
50
100
Time (min)
150
200
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexenoxide.
b
c
d
TON ¼ mole of product/mole of catalyst.
Fig. 9. Time-dependent conversion of cyclohexene oxidation a) for catalyst 4 b) for
catalyst 5.
e
TOF ¼ mole of product/mole of catalyst ꢁ time.

260
E.T. Saka et al. / Dyes and Pigments 98 (2013) 255e262
Table 5
Catalytic activities towards the homogeneous oxidation of cyclohexene of some
previously reported catalyst.
Catalyst
Rxn
time (h)
Rxn
Oxidant
O2
Conv. (%)
Ref.
[60]
Temp. (ꢀC)
rtg
w45
w55
w30
89
93
28
a
Mn(tbpcH2
)
24
a
Fe(tbpcH2
Co(tbpcH2
)
a
)
Fe(TMPb)Cl
10 min
3
16
25
m-CPBA
PhIO
PhIO
[61]
[54]
[62]
Mn(PFTDCPPc)
MnTMpyP
FeTMpyP
nrh
rtg
29
MoTMpyP
MnTTAPP
Cl16FePcd
0
39
45.3
8
nrh
75
TBHP
[32]
FePcd
Fig. 10. The oxidant effect on cyclohexene oxidation.
CoPcd
Co[N ˇ O]2 Cu[N ˇ Oe]2
8
H2O2
O2
27.6
43.50
60
[63]
[64]
[65]
Fast degradation of the phthalocyanine ring 4 and 5 were
observed when H2O2 was employed as an oxidant. In fact, the so-
lution went from the blue-green colour of the 4 or 5 catalyst to
colourless, immediately following addition of this oxidant, hence
oxidation using this oxidant and 4 or 5 was not studied effectively.
A degradation of ring was also observed for m-CPBA, though to a
lesser extent compared to H2O2. Table 2 showed that 4 and 5 exhibit
significantly higher activity with TBHP than the other studied ox-
idants. (TON:356 and 310 for catalyst 4 and 5) The control experi-
ment showed that the cyclohexene was not oxidized in the absence
of oxidant.
The substrate-to-oxidant ratio is another important parameter
influencing the results of this oxidation reaction. The effect of ox./
cat. ratio on the rate of cyclohexene was also studied in the range of
400/1e900/1 (Table 3). The rate of the reaction increased with
increasing ox./cat. ratio up to 500/1. Further increasing in this ratio,
lead to decreased conversion. It is difficult to explain the oxidant
effect at this stage, but, it is possible that the coordination around
the iron and cobalt ion may change and produce inactive inter-
mediate species.
Investigation into the effect of the reaction temperature on the
oxidation of cyclohexene with 4 and 5 showed that as the reaction
temperature was raised the catalyst activity increased. The ex-
periments were conducted in the temperature range of 25e90 ꢀC
with ox./subst./cat. ¼ 500/200/1 and TBHP, in DMF during 3 h
(Table 4). The overall conversion was increased 51% for complex 4
and 43% for complex 5 when the temperature was raised 25 to
90 ꢀC. The highest conversion (99%) was obtained with TOF ¼ 65
for complex 4 and (85%) was obtained with TOF ¼ 56 for complex 5
at 90 ꢀC.
Cu(II)(L-prolinate)2
24
8
22
40
40
20
[Mn(Me2salpnMe2f)]
[Co(Me2salpnMe2f)]
[Cu(Me2salpnMe2f)]
[Ni(Me2salpnMe2f)]
Co(salen)ePOM
TBHP
50.9
42.7
36.9
23.8
91
6
60
H2O2
[66]
a
tbpcH2 ¼ tetra-tert-butylphthalocyanine.
TMP ¼ meso-tetramesitylporphinato.
b
c
PFTDCPP ¼ 5-(pentaflorophenyl)-10,15-20-tri(2,6-dichlorophenyl)porhrin.
Pc ¼ phthalocyanine.
d
e
f
N ˇ O ¼ 2-pyrazinecarboxylic acid.
Me2salpnMe2 ¼ N,N_-bis-(
rt ¼ room temperature.
nr ¼ not reported.
a-methylsalicylidene)-2,2-dimethylpropane-1.
g
h
Degradation of Co-Pc catalysts 5 was proved during the oxidation
process using UVevisible spectroscopy. The spectra of cobalt phtha-
locyanines has been a subject of several reports [58,59]. In the
absence of oxygen, the spectra of Co-Pc catalyst 5 in DMF consists of a
sharp vibronicQ band due to the monomeric species [58]. The spec-
trum in Fig. 11 indicates the typical spectrum of monomeric form of
CoPc with a Q band at 664 and also the electronic spectral changes of
both catalysts over the catalytic reaction in the presence of oxidant.
The Q band shifted from 664 to 671 nm with a decrease in intensity of
the Q band without any new band being formed. The shift in the Q
band is consistent with metal oxidation of Co(II)-Pc to Co(III)-Pc [40].
As shown in Table 5 the performance of the Fe-Pc and Co-Pc
catalyst 4 and 5 towards the cyclohexene oxidation is better com-
pared to some other MPc and M-porphyrin catalyst (like Fe, Zn, Cu
and Mn). We obtained the best reported results in terms of TOF in
literature for homogeneous oxidation of cyclohexene with TBHP in
the presence of FePc and Co-Pc. It is also reported that FePc was found
to be best catalyst on this work when it was compared with Co-Pc.
2
a
b
c
d
1,8
1,6
1,4
1,2
1
4. Conclusion
We have presented the synthesis and characterized of a new
peripherally tetra-substituted Fe(II) and Co(II) phthalocyanines 4
and 5 using spectroscopic methods. The target symmetrical Fe(II)
and Co(II) phthalocyanines 4 and 5 were separated by column
chromatography and characterized by a combination of UVevis, IR,
1H NMR,13C NMR, MS spectroscopic data. This work has determined
catalytic activities of Fe(II) and Co(II) phthalocyanines 4 and 5 on
cyclohexene oxidation. There are few reports about catalytic studies
for Fe(II) and Co(II) phthalocyanines. The results show that cyclo-
hexene was converted to 2-cyclohexene-1-ol as major product and
2-cyclohexen-1-one, cyclohexene oxide as minor products with 99%
and 85% with 4 and 5 respectively, within 3 h with TBHP in DMF at
90 ꢀC. The most promising observation is that cyclohexenol is found
0,8
0,6
0,4
0,2
0
500
550
600
650
Wavelength (nm)
700
750
800
Fig. 11. Time-dependent changes in the visible spectrum of the oxidized complex 5
observed on addition of TBHP (1.78 ꢁ 10ꢂ3 mol) to a reaction mixture containing
0.71 ꢁ10ꢂ3 mol cyclohexene and 3.57 ꢁ 10ꢂ6 mol complex 5 catalyst in 10 mL: (b) 60 min;
(c) 120 min; (d) 180 min after addition of TBHP. All spectra for the oxidized complex 5 were
taken after six fold dilution with DMF. (a) Visible spectrum of (non-oxidized) complex 5.

E.T. Saka et al. / Dyes and Pigments 98 (2013) 255e262
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