Investigation of catalytic activity of new Co(II) phthalocyanine complexes in cyclohexene oxidation using different type of oxidants

Article abstract of DOI:10.1016/j.jorganchem.2013.07.013

In this work, the new phthalonitrile derivatives 4, 5 bearing 1,3-bis(naphthalen-1-yloxy)propan-2-ol and 1,3-bis(naphthalen-2-yloxy)propan-2- ol, cobalt phthalocyanine complexes have been synthesized. The new cobalt phthalocyanines have been prepared by cyclotetramerization of phthalonitrile derivatives 4, 5 in the presence of the corresponding CoCl₂ salt in DMAE by using a microwave oven. The new compounds have been characterized by IR, ¹H NMR, ¹³C NMR and MS spectral data. The new complexes have been tested as a catalyst for the oxidation of cyclohexene with different oxidants, such as tert-butylhydroperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA) and hydrogen peroxide (H₂O₂), in DMF. m-CPBA is also found as the most successful oxidant in the other oxygen sources. In this sense, the substrate/catalyst ratio, the influence of temperature, oxidant/cat ratio and type of oxidant have been studied. It is observed three oxidation products. First one is 2-cyclohexene-1-ol as dominant product and the others are 2-cyclohexene-1-one and cyclohexene oxide as minor product.

Full text of DOI:10.1016/j.jorganchem.2013.07.013

Journal of Organometallic Chemistry 745-746 (2013) 18e24
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Investigation of catalytic activity of new Co(II) phthalocyanine
complexes in cyclohexene oxidation using different type of oxidants
a
a
,
a
b
a
_
*
ꢀ
ꢀ
Ays¸e Aktas¸ , Ece Tugba Saka , Zekeriya Bıyıklıoglu , Irfan Acar , Halit Kantekin
a Department of Chemistry, Karadeniz Technical University, 61080, Trabzon, Turkey
b Department of Energy System Engineering, Faculty of Of Technology, Karadeniz Technical University, 61830, Of, Trabzon, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
In this work, the new phthalonitrile derivatives 4, 5 bearing 1,3-bis(naphthalen-1-yloxy)propan-2-ol and
1,3-bis(naphthalen-2-yloxy)propan-2-ol, cobalt phthalocyanine complexes have been synthesized. The
new cobalt phthalocyanines have been prepared by cyclotetramerization of phthalonitrile derivatives 4, 5
in the presence of the corresponding CoCl2 salt in DMAE by using a microwave oven. The new com-
pounds have been characterized by IR, 1H NMR, 13C NMR and MS spectral data. The new complexes have
been tested as a catalyst for the oxidation of cyclohexene with different oxidants, such as tert-butylhy-
droperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA) and hydrogen peroxide (H2O2), in DMF. m-
CPBA is also found as the most successful oxidant in the other oxygen sources. In this sense, the sub-
strate/catalyst ratio, the influence of temperature, oxidant/cat ratio and type of oxidant have been
studied. It is observed three oxidation products. First one is 2-cyclohexene-1-ol as dominant product and
the others are 2-cyclohexene-1-one and cyclohexene oxide as minor product.
Received 15 May 2013
Received in revised form
21 June 2013
Accepted 5 July 2013
Keywords:
Phthalocyanine
Cobalt(II)
Cyclohexene oxidation
Oxidant
m-Chloroperoxybenzoic acid
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
well as their exceptional stability in time and extreme conditions
(temperature, pH, etc.). Furthermore, they are intensively used as
The industrial and environmental preoccupations meet on their
common need for more efficient and cheaper catalysts. These high-
tech catalysts are required for a more effective degradation of
pollutants, which is one of their two main uses, or for high scale
synthetic purposes. Oxidation of different type of molecules such as
alkyl aromatics, alkenes and alcohols are of particular importance
as it lead to small molecules used as starting products for more
complex syntheses in fine chemicals production (pharmaceutics,
cosmetics, polimerization monomers). As the transformed func-
tions can lead to different products, the selectivity of the catalyst is
essential to the overall catalytic system’s efficiency [1].
Bioinspired heme-like catalysts were developed for synthetic
purposes as their natural models are active oxidant catalysts, highly
selective and performing. Porphyrin’s structure common to these
enzymes was therefore used by synthetic chemists aiming at
developing new catalytic structures. Phthalocyanines, tetraaza-
benzoporphyrins analogs of porphyrins, after having been used as
simple dyes and pigments, rise interests since a few decades as
their multi functional structure (large delocalized aromatic system,
metallation, flexibility on a substitution pattern point of view) as
homogenoushomogenous and heterogenous catalyst, liquid crystal,
electro-and photo-chemical sensor, photoconductive materials,
batteries and fuel supplies, photosensitizier in photodynamic
therapy agent [2e7]. They are known to possess better catalytic
properties than the prophyrins, especially thanks to their superior
stability in oxidation conditions.
The higher oxidation states of the central transition metal ions are
more readily accessible in the porphyrin series than in the phthalo-
cyanine series [8]. In other words, phthalocyanine ligand tends to
stabilize the lower oxidation states of metal compared to porphyrin
one. This implies that high oxidation states metallophthalocyanines
should be stronger oxidizing agents than their porphyrin analogs in
the same oxidation state. In porphyrin series the kind of the cleavage
of OeO bond is determined by the structures of porphyrin ligand and
peroxide and the presence of axial ligand, which favors a heterolytic
OeO bond cleavage [9]. In addition, cobalt phthalocyanine complexes
are also used as oxidation catalyst for selective oxidation of olefines
[10]. It is found that Co(II) phthalocyanines can transfer oxygen from
various oxygen donors to alkanes, alkenes, phenols and thiols in
the several studies [11e22]. Condensed aromatic compounds con-
taining naphthalene derivatives are effective functional groups in
photoemission studies [23,24]. Thus, in this paper we have aimed to
synthesize a new class of cobalt phthalocyanines bearing 4-{2-(1-
Naphthyloxy)-1-[(1-naphthyloxy)methyl]ethoxy}, 4-{2-(1-Naphthy
* Corresponding author. Tel.: þ90 462 377 3666; fax: þ90 462 325 3196.
E-mail address: ece_t_saka@hotmail.com (E.T. Saka).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.07.013

A. Aktas¸ et al. / Journal of Organometallic Chemistry 745-746 (2013) 18e24
19
loxy)-1-[(2-naphthyloxy)methyl]ethoxy} groups on the substitue
2.1.4. Cobalt(II) phthalocyanine (7)
nts. Additionally, the present paper also has reported on the appli-
cation of phthalocyanine-based homogenous catalysts in the oxida-
tion of cyclohexene. We have investigated the oxidation process with
the purpose of developing product selectivity and increasing the
range of products. Co(II) phthalocyanine complexes have been
compared as best catalysts for the oxidation.
Synthesized similarly to 6 from 5. Yield: 92 mg (40%). mp:
>300 ꢂC. IR (KBr tablet) nmax/cmꢁ1: 3058 (Ar-H), 2957e2855(Aliph.
CeH), 1727, 1628, 1599, 1510, 1463, 1390, 1254, 1217, 1182, 1120,
1071, 965, 837, 750, 623, 471. UVeVis (THF): lmax, nm (log ): 669
3
(4.32), 604 (3.74), 328 (4.27). MALDI-TOF-MS: m/z: 1941 [M þ H]þ.
2.2. Measurements
2. Experimental
FT-IR spectra were obtained on a PerkineElmer 1600 FT-IR
spectrophotometer with the samples prepared as KBr pellets. Op-
tical spectra in the UVevisible region were recorded with a Perkine
Elmer Lambda 25 spectrophotometer. 1H and 13C NMR spectra were
recorded on a Varian Mercury 200 MHz spectrometer in CDCl3, and
chemical shifts were reported (d) relative toMe4Si as internal
standard. Mass spectra were measured on a Micromass Quatro LC/
ULTIMA LCeMS/MS spectrometer. MALDI-MS of complexes was
obtained in dihydroxybenzoic acid as MALDI matrix using nitrogen
laser accumulating 50 laser shots using Bruker Microflex LT MALDI-
TOF mass spectrometer. Melting points were measured on an
electrothermal apparatus. A domestic microwave oven was used for
all syntheses of phthalocyanines.
All reactions were carried out under a dry nitrogen atmosphere
using standard Schlenk techniques. All chemicals, solvents and
reagent were of reagent grade quality and were used as purchased
from commercial sources. All solvents were dried and purified as
described by a reported procedure [25]. 1,3-Bis(naphthalen-1-
yloxy)propan-2-ol 1 and 1,3-bis(naphthalen-2-yloxy)propan-2-ol
2 were synthesized according to the literature, respectively [26,27].
2.1. Synthesis
2.1.1. 4-{2-(1-Naphthyloxy)-1-[(1-naphthyloxy)methyl]ethoxy}
phthalonitrile (4)
4-Nitrophthalonitrile 3 (0.6 g, 3.5 ꢀ 10ꢁ3 mol) was dissolved in
0.03 L dry DMF under N2 atmosphere, and of 1,3-bis(naphthalen-1-
yloxy)propan-2-ol 1 (1.2 g, 3.5 ꢀ 10ꢁ3 mol) was added to the
mixture. After stirring for 30 min at 60 ꢂC, finely ground anhydrous
K2CO3 (1.45 g, 10.5 ꢀ 10ꢁ3 mol) was added portion wise within 2 h.
The reaction mixture was stirred under N2 at 60 ꢂC for 4 days. At the
end of this time, the reaction mixture was poured into ice-water
and stirred at room temperature for 1 h to yield a crude product.
The mixture was filtered and dried in vacuum over P2O5 for 4 h and
recrystallized from ethanol to give light yellow crystalline powder.
Yield: 0.6 g (35%). mp: 63e67 ꢂC. IR (KBr pellet), nmax/cmꢁ1: 3055e
3019 (Ar-H), 2931e2879 (Aliph. CeH), 2232 (C<ce:glyph
name¼"tbnd"/>N), 1728, 1669, 1600, 1575, 1505, 1400, 1349, 1157,
1143, 1000, 1021, 1024, 973, 873, 769, 667, 571, 524. 1H NMR.
2.3. General procedure for the oxidation of cyclohexene
All reactions were performed in a thermostated Schlenk vessel
equipped with a condenser and stirrer. The solution of cyclohexene
and catalyst in solvent were purified with bubbling nitrogen gas to
remove the oxygen. A mixture of cyclohexene (0.78 ꢀ 10ꢁ3 mol),
catalysts (2.57 ꢀ 10ꢁ6 mol) and solvent mixture (0.01 L) were
stirred in a Schlenk vessel for few minutes at room temperature.
Then, the oxidant TBHP (1.28 ꢀ 10ꢁ3 mol) was added and the re-
action 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 the GC, 1
mL each time. Formation of
products and consumption of substrates were monitored by GC.
(CDCl3), (
Ar-H), 6.89 (d, 2H, Ar-H), 5.41 (t, 1H, OeCH), 4.61 (m, 4H, OeCH2).
13C NMR. (CDCl3), (
: ppm): 162.48, 155.32, 136.74, 134.58, 127.88,
d: ppm): 8.08 (d, 2H, Ar-H), 7.84 (d, 2H, Ar-H), 7.66 (m,11H,
3. Results and discussion
d
127.08, 126.68, 126.12, 124.48, 123.76, 121.22, 117.87, 116.52, 115.91,
3.1. Synthesis and characterization
115.36, 112.57, 107.48, 106.05, 79.85, 67.30. MS (ESI), m/z: 470 [M]þ.
Scheme 1 shows a brief schematic for the synthesis of periph-
erally tetra-substituted cobalt phthalocyanine complexes 6 and 7.
The phthalonitrile derivatives 4 and 5 were synthesized from the
1,3-bis(naphthalen-1-yloxy)propan-2-ol 1 and 1,3-bis(naphthalen-
2-yloxy)propan-2-ol 2 by nucleophilic reaction with 4-nitroph
thalonitrile 3 in the presence of K2CO3 and in dry DMF at 50 ꢂC,
respectively. After, in a microwave oven, cobalt phthalocyanines 6
and 7 were obtained in the presence of metal salt (CoCl2) in DMAE
at 175 ꢂC, 350 Watt in average 6 min.
2.1.2. 4-{2-(2-Naphthyloxy)-1-[(2-naphthyloxy)methyl]ethoxy}
phthalonitrile (5)
Synthesized similarly to 4 from 2. Yield: 0.3 g (15%). IR (KBr
pellet), nmax/cmꢁ1: 3054e3017 (Ar-H), 2928e2877 (Aliph. CeH),
2231 (C<ce:glyph name¼"tbnd"/>N), 1728, 1628, 1596, 1508, 1462,
1317, 1253, 1240, 1178, 1157, 1102, 1020, 972, 874, 836, 792, 771, 667,
570. 1H NMR. (CDCl3), (
d
: ppm): 7.77 (m, 6H, Ar-H), 7.53e7.18 (m,
11H, Ar-H), 5.27 (m, 1H, OeCH), 4.53 (m, 4H, OeCH2). 13C NMR.
(CDCl3), ( : ppm): 162.56, 156.04, 135.51, 134.50, 130.11, 129.57,
d
In the IR spectra, the formation of compounds 4 and 5 was
clearly confirmed by the disappearance of the OH and NO2 band at
w3410 and w1538e1355 cmꢁ1 and appearance of a single intense
127.98, 126.99, 124.47, 121.40, 120.90, 118.61, 117.73, 116.38, 115.61,
112.56, 107.13, 104.72, 79.45, 67.39. MS (ESI), m/z: 470 [M]þ.
peak (C<ce:glyph name¼"tbnd"/>N) at 2232 and 2231 cmꢁ1
,
2.1.3. Cobalt(II) phthalocyanine (6)
respectively. In the 1H NMR spectrum of 4 and 5, OH group of
compounds 1 and 2 disappeared as expected. In the 1H NMR
spectrum of compounds 4 and 5 the aromatic protons appear at
8.08 (d), 7.84 (d), 7.66 (m), 6.89 (d) ppm for compound 4, 7.77 (m),
7.53e7.18 (m) ppm for compound 5. Also nitrile carbon atoms were
observed at 115.36, 112.57 ppm for compound 4, 115.61, 112.56 ppm
for compound 5. The MS spectrum of compounds 4 and 5, which
shows a peak at m/z ¼ 470 [M]þ supports the proposed formula for
these compounds.
A mixture of compound 4 (300 mg, 0.64 mmol), anhydrous CoCl
(41.5 mg, 0.32 mmol) and dry DMAE (3 mL) was irradiated in a
microwave oven at 175 ꢂC 350 W for 7 min. Then dark green
product was filtered and solid raw accomplished by column chro-
matography which is placed aluminum oxide (Al2O3) using
CHCl3:CH3OH (5:1) as solvent system. The yield: 210 mg, (68%) mp:
>300 ꢂC. IR (KBr tablet) nmax/cmꢁ1: 3053 (Ar-H), 2953e2852 (Aliph.
CeH), 1722, 1595, 1579, 1508, 1460, 1385, 1267, 1238, 1178, 1156,
1102, 1020, 967, 790, 770, 570. UVevis (THF): lmax, nm (log
3
): 671
The IR spectra of the cobalt(II) phthalocyanines 6 and 7 which
are very similar each other, show no the sharp C<ce:glyph
(4.59), 605 (4.02), 320 (4.67). MALDI-TOF-MS: m/z: 1941 [M þ H]þ.

20
A. Aktas¸ et al. / Journal of Organometallic Chemistry 745-746 (2013) 18e24
OH
OH
O
O
O
O
2
1
CN
CN
CN
i
i
O2N
O2N
CN
3
3
CN
CN
CN
CN
O
O
O
O
O
O
5
4
ii
ii
R1O
R2O
OR1
OR2
N
N
N
N
N
N
Co
N
N
Co
N
N
N
N
N
N
N
N
OR1
R1O
6
7
OR2
R2O
O
O
O
O
R2=
R1=
Scheme 1. The synthetic phthalonitriles and cobalt phthalocyanine complexes. Reagents and conditions: (i) dry DMF, K2CO3, 60 ꢂC; (ii) CoCl2, DMAE, 175 ꢂC, 350 W.
name¼"tbnd"/>N vibration peak (2232e2231 cmꢁ1) which was
observed in the IR spectra of 4 and 5. The 1H NMR spectra of
metallophthalocyanines 6 and 7 could not be taken because of the
paramagnetic cobalt(II) center. In the mass spectrum of Co phtha-
locyanines, the presence of molecular ion peaks at m/z ¼ 1941
[M þ H]þ, confirmed the proposed structures.
605 nm for 6, 604 nm for 7 and the B bands were observed between
328 and 320 nm.
3.2. Catalytic studies
3.2.1. Oxidation of cyclohexene with complex 6 and complex 7
Cyclohexene (0.77 ꢀ 10ꢁ3 mol), cobalt(II) phthalocyanine com-
plexes (2.57 ꢀ 10ꢁ6 mol), m-CPBA (1.28 ꢀ 10ꢁ3 mol) and DMF
(0.01 L) were mixed in Schlenk vessel and refluxed at 90 ꢂC with
900 rpm stirring (Tables 1e4). The formed oxidized products were
The UV/vis spectra of the cobalt(II) phthalocyanine complexes 6
and 7 in DMF at room temperature are shown in Fig. 1. In UVevis
spectra of the cobalt(II) phthalocyanines Q-bands were observed at
around 671 nm for 6, 669 nm for 7 with the shoulders at around

A. Aktas¸ et al. / Journal of Organometallic Chemistry 745-746 (2013) 18e24
21
Table 2
Temperature effect of cyclohexene oxidation with complexes 6 and 7.
Catalyst T (ꢂC) Alcohola Ketoneb Epoxidec Tot. conv. (%) TONd TOFe (hꢁ1
)
6
7
6
7
6
7
6
7
25
50
70
90
25
24
36
33
47
41
54
49
17
20
27
23
27
23
29
26
5
4
6
14
7
14
8
47
51
69
70
81
78
97
94
141 47
153 51
207 69
210 70
243 81
234 78
291 97
282 94
19
Conversion was determined by GC.
Reacion time ¼ 3 h.
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexene oxide.
b
c
d
TON ¼ mole of product/mole of catalyst (all products).
e
Fig. 1. UVevis spectrum of 6 and 7 in THF.
TOF ¼ mole of product/mole of catalyst ꢀ time(3 h).
monitored with GC by spotting and comparing with standards.
Blank experiments were done without the catalysts to observe vital
mission on the cyclohexene oxidaition. In Tables 1e4, different
operation conditions were evaluated to compare the catalytic ac-
tivity of 6 and 7. Then, the results show that for oxidation of
cyclohexene these complexes are active catalyst in DMF. Three
types of oxidized product were obtained. They are 2-cyclohexene-
1-ol as dominant product and 2-cyclohexen-1-one and cyclo-
hexene epoxide (Fig. 2). To improve the conversion of cyclohexene,
the parameters such as substrate/catalyst ratio, the reaction tem-
perature, oxidant ratio and type of oxidants were investigated.
Surprisingly the conversion was reached the highest value after
3 h when complexes 6 and 7 were used as catalyst. But after 3 h, the
conversion stayed the same value (Fig. 3a and b). Both catalysts were
employed as catalyst to give same oxidized product that is 2-
cyclohexene-1-ol with high yield. Table 1 shows that cyclohexene
oxidation reactions were done with different the substrate/catalyst
ratio (300e1500). The other reaction conditions are 1.28 ꢀ 10ꢁ3 mol
m-CPBA, 0.01 L DMF, 90 ꢂC and 3 h. The low substrate catalyst molar
ratio done a remarkable acceleration effect on the reaction rate of
cyclohexene oxidation. When the substrate concentration de-
creases, the reaction rate increases. Looking at the data inTable 1 it is
easy to realize that 2-cyclohexene-1-ol as dominant product with
selectivity of 54% and 49% for complexes 6 and 7 respectively.
This study shows that the catalyst 6 and 7 with m-CPBA as
oxidant leaned the formation of 2-cyclohexene-1-ol from the other
products.
Table 2 shows experimental results related to effect of tem-
perature on cyclohexene conversion toward the products with
ox./subst./cat. ¼ 500/300/1 and m-CPBA, in DMF during 3 h. For
this parameter, DMF was used as solvent due to its high boiling
point. Whereby, we can study different temperature effect on
cyclohexene oxidation. According to Table 2, we can conclude
that the reaction temperature on the oxidation of cyclohexene
was raised when the catalytic activity of complexes 6 and 7
increased. When the reaction temperature was increased to the
highest temperature, the yield of oxidized products was
increased. The highest conversion at 90 ꢂC was observed that 97%
and 94% with TON ¼ 291 and 282 for complexes 6 and 7
respectively. The overall conversion was increased 50% for
Table 1
Amount of substrate effect of cyclohexene oxidation with complexes 6 and 7.
Catalyst
Subs./cat.
300/1
Alcohola
54
Ketoneb
Epoxidec
8
Tot. conv. (%)
97
TONd
291
TOFe (hꢁ1
97
)
6
29
26
7
49
19
94
282
94
6
7
6
600/1
900/1
48
45
37
29
25
8
10
8
85
80
74
510
480
666
170
160
222
29
25
22
18
19
16
7
6
7
6
7
34
30
27
18
16
10
5
69
57
51
40
36
621
684
612
630
540
207
228
204
210
180
1200/1
1500/1
6
3
4
Conversion was determined by GC.
Reacion time ¼ 3 h.
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexene oxide.
b
c
d
TON ¼ mole of product/mole of catalyst (all products).
e
TOF ¼ mole of product/mole of catalyst ꢀ time(3 h).

22
A. Aktas¸ et al. / Journal of Organometallic Chemistry 745-746 (2013) 18e24
Table 3
O
OH
Different oxidant effect of cyclohexene oxidation with complexes 6 and 7.
Oxidant
Catalyst Oxidant Alcohola Ketoneb Epoxidec Tot.Conv. TONd TOFe
O
Catalyst (MPc)
(%)
(hꢁ1
)
Cyclohexene
2-cyclohexene-1-one
6
7
6
7
6
7
6
7
TBHP
H2O2
33
34
22
14
26
23
22
26
29
26
e
6
10
6
12
8
65
67
50
52
97
94
e
195
201
150
156
291
282
e
65
67
50
52
97
94
e
2-cyclohexene-1-ol
cyclohexenoxide
Fig. 2. Product formed through oxidation of cyclohexene by TBHP, m-CPBA and H2O2
in the presence of complexes 6 and 7.
m-CPBA 54
49
Free
19
e
e
increased from 300 to 500, total conversion was increased from %69
to %97 for complex 6 and %57 to %94 for complex 7. But from this
ratio until to 1200/1, the total conversion tended to decrease. We
cannot easily tell oxidant role at this stage, but this situation may
explain as changing coordination of cobalt and iron ion and create
nonactive species.
Table 5 barely demonstrate that the success of Co(II) phthalocy-
anine catalysts 6 and 7 by comparison of the metallophthalocyanine
and metalloporphyrin catalysts. We obtained the best reported re-
sults in terms of TOF in literature for homogenous oxidation of
cyclohexene with m-CPBA in the presence of Co(II) phthalocyanine
catalysts.
oxidant
Conversion was determined by GC.
Reacion time ¼ 3 h.
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexene oxide.
b
c
d
TON ¼ mole of product/mole of catalyst (all products).
e
TOF ¼ mole of product/mole of catalyst ꢀ time(3 h).
complex 6 and 43% for complex 7, when the temperature was
raised 25e90 ꢂC. The low reaction temperature did not favor the
oxidation of cyclohexene. At the lowest temperature (25 ꢂC),
the conversion of cyclohexene to oxidized products only 47%
for complex 6 and 51% for complex 7.
3.3. Monitoring the oxidation system by UVevis spectroscopy
Table 3 shows that the data were obtained from the results of
oxidation experiments with different types of oxygen sources (such
as TBHP, m-CPBA, aerobic oxygen and H2O2). For these experi-
ments, 1.28 ꢀ 10ꢁ3 mol m-CPBA, TBHP, H2O2 were used. During
these experiments, m-CPBA was found most effective oxidant on
the oxidation of cyclohxene with complexes 6 and 7 (Fig. 4). For the
blank experiments, all reactions were done again without m-CPBA
and we deduced that cyclohexene oxidation reactions did not
progress. The other oxygen sources like TBHP or hydrogen peroxide
were not found suitable oxidant for our catalytic system. The reason
of observation the lowest conversion with H2O2 is fast degradation
of the phthalocyanine ring 6 and 7. The color of solution immedi-
ately turned from the blue-green color of to colorless after adding
H2O2. Because of this, complexes 6 and 7 were not employed
effectively as catalyst during the oxidation. When comparing the
performance of TBHP and H2O2, decomposition of phthalocyanine
ring of complexes 6 and 7 with THBP was lower than H2O2. The
highest activity of complexes 6 and 7 with m-CPBA (TOF:97 and 94)
and other oxidant activity can be seen in Table 3.
Within the UV spectrum of the metallophthalocyanines has been
observed the existence of two absorption bands assigned to the
transition n / p* and
p /
p*. These absorbstion bands, that are
called as B and Q bands, are observed in the UVevis spectra of Co(II)
phthalocyanine complexes [28e39]. Also these bands are to be
found in the spectra of the metallophthalocyanine complexes, but
Table 4 shows the results getting from cyclohexene oxidation
reaction with changinge substrate-to-oxidant ratio. This ratio effect
was worked in the range of 300/1e1200/1. When the ratio was
Table 4
Amount of oxidant effect of cyclohexene oxidation with complexes 6 and 7.
Catalyst Oxidant/ Alcohola Ketoneb Epoxidec Tot. conv. TONd TOFe
catalyst
(%)
(hꢁ1
)
6
7
6
7
6
7
6
7
6
7
300/1
40
22
54
49
49
38
49
33
34
22
22
19
29
26
25
24
20
22
19
20
7
16
8
19
8
17
10
15
9
69
57
97
94
82
79
79
70
62
56
207
156
291
282
246
237
237
210
186
168
69
52
97
94
82
79
79
70
62
56
500/1
700/1
1000/1
1200/1
14
Conversion was determined by GC.
Reacion time ¼ 3 h.
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexene oxide.
b
Fig. 3. Time-dependent conversion of cyclohexene oxidation a) for catalyst 6 b) for
catalyst 7 [Reaction conditions: Cyclohexene (0.77 ꢀ 10ꢁ3 mol), cobalt(II) phthalocy-
anine complexes (2.57 ꢀ 10ꢁ6 mol), m-CPBA (1.28 ꢀ 10ꢁ3 mol), DMF (0.01 L), 3 h and
90 ꢂC].
c
d
TON ¼ mole of product/mole of catalyst (all products).
e
TOF ¼ mole of product/mole of catalyst ꢀ time(3 h).

A. Aktas¸ et al. / Journal of Organometallic Chemistry 745-746 (2013) 18e24
23
Fig. 5. Time-dependent changes in the visible spectrum of the oxidized complex 6
observed on addition of TBHP (1.28 ꢀ 10ꢁ3 mol) to a reaction mixture containing
0.77 ꢀ 10ꢁ3 mol cyclohexene and 2.57 ꢀ 10ꢁ6 mol complex 6 catalyst in 10 ml: (a)
45 min; (d) 90 min; (c) 135 min (d) 180 min after addition of m-CPBA. All spectra for
the oxidized complex 6 were taken after sixfold dilution with DMF. (e) Visible spec-
trum of (non-oxidized) complex 6.
Fig. 4. The oxidant effect on cyclohexene oxidation [Reaction conditions: Cyclohexene
(0.77 ꢀ 10ꢁ3 mol), cobalt(II) phthalocyanine complexes (2.57 ꢀ 10ꢁ6 mol), m-CPBA
(1.28 ꢀ 10ꢁ3 mol), DMF (0.01 L), 3 h and 90 ꢂC].
they broadens and shifts because of m-oxo dimeric species of Co(II)-
Pc to Co(III)ePc [40]. Figs. 5 and 6 indicate spectral changes
observed for the catalysts 6 and 7 during the oxidation reaction with
m-CPBA. The typical monomeric form of Co(II) phthalocyanine
complexes is seen in Fig. 1 before the start of the catalytic reactions.
Q band at 669 nm for complexes 6 and 7 with respectively. With
adding of oxidant (such as TBHP, m-CPBA or H2O2), Q-band de-
creases in intensity and broadens at 666 and 667 nm. Around the B
band religion (w480 nm) there is no peak. Thus addition of m-CPBA
to solutions of Co(II) complexes resulted in only metal and not ring
oxidation of Co-Pc. As catalysis proggressed, there was a prog-
gressive decrease in the intensity of the Q band of the Co(II)
phthalocyanine catalyst, suggesting catalyst degradation as is
typical of MPc catalysts in homogenous catalysis [41]. The reason of
this degradation can be explained as a result of the attack of the
phthalocyanine ring by the alkoxy and alkylperoxide radicals which
are produced from m-CPBA. It is noted the change of reaction color
that from blue to green as catalysis continued. However, the reac-
tion products continued to form even after the catalyst had turned
yellow, suggesting that once reaction intermediates are formed, the
reaction can still progress in the presence or absence of the original
Fig. 6. Time-dependent changes in the visible spectrum of the oxidized complex 7
observed on addition of m-CPBA (1.28 ꢀ 10ꢁ3 mol) to a reaction mixture containing
0.77 ꢀ 10ꢁ3 mol cyclohexene and 2.57 ꢀ 10ꢁ6 mol complex 7 catalyst in 10 ml: (a)
45 min; (d) 90 min; (c) 135 min (d) 180 min after addition of m-CPBA. All spectra for
the oxidized complex 7 were taken after sixfold dilution with DMF. (e) Visible spec-
trum of (non-oxidized) complex.
form of the catalyst. Both phthalocyanine complexes were degra-
gaded by the oxidant. These degradation were monitored changing
color by UVevis spectroscopy. Whenwe used m-CPBA as an oxidant,
the reaction color changed from blue to green and the oxidation
progressed, the catalyst turned yellow. This indicates that com-
plexes 6 and 7 can exist a long time in reaction media and catalyzed
effectively without degradation on cyclohexene oxidation.
Table 5
Catalytic activities toward the homogeneous oxidation of cyclohexene of some
previously reported catalyst.
Catalyst
Rxn
time (h)
Rxn
Oxidant
Conv.
(%)
Ref.
temp. (ꢂC)
a
Co(tbpcH2
)
24
Rth
O2
w45
w55
w30
45.3
27.6
43.50
42.7
91
[42]
CoPcb
8
8
nri
75
TBHP
H2O2
[41]
[43]
4. Conclusion
Co[N^O]2 Cu[N^Oc]2
In conclusion, we have synthesized and characterized a new
metal free phthalocyanine, cobalt(II) complexes and showed their
catalytic activity in the selective oxidation of cyclohexene to 2-
cyclohexen-one as dominant product, 2-cyclohexen-ol and cyclo-
hexene oxide under homogenous conditions with TBHP in DMF. We
have also investigated that UVevis spectrum of new cobalt(II)
phthalocyanine complexes in different solvents (CH2Cl2, CHCl3, THF
and DMF). The high percentage yield of reactions in the presence of
cobalt(II) phthalocyanine complexes seems promising.
[Co(Me2salpnMe2d)]
Co(salen)ePOM
CoPce
8
6
40
60
90
90
TBHP
H2O2
m-CPBA
m-CPBA
[44]
[45]
[10]
[21]
3
3
61
80
45
CoPcf
CoPcg
a
tbpcH2 ¼ tetra-tert-butylphthalocyanine.
Pc ¼ peripherally substituted phthalocyanine.
N^O ¼ 2-pyrazinecarboxylic acid.
b
c
d
e
Me2salpnMe2 ¼ N,N-bis-(
a
-methylsalicylidene)-2,2-dimethylpropane-1.
Pc
¼
4-{2-[3-(diethylamino)phenoxy]ethoxy} group substituted
phthalocyanine.
f
Pc
¼
4-[2-(1,4-dioxa-8-azaspiro[4.5]dec-8-yl)ethoxy group substituted
Acknowledgments
phthalocyanine.
g
Pc ¼ 4-(3,3-diphenylpropoxy) group substituted phthalocyanine.
h
This study was supported by the Research Fund of Karadeniz
Technical University, Project no: 9666 (Trabzon-Turkey).
rt ¼ room temperature.
i
nr ¼ not reported.

24
A. Aktas¸ et al. / Journal of Organometallic Chemistry 745-746 (2013) 18e24
ꢀ
[21] E.T. Saka, Z. Bıyıklıoglu, H. Kantekin, I. Kani, Appl. Organometal. Chem. 27
References
(2013) 59e67.
ꢀ
[22] E.T. Saka, I. Acar, Z. Bıyıklıoglu, H. Kantekin, I. Kani, Synth. Met. 169 (2013)
[1] Umit I, Novel-bridged Diiron Phthalocyanine Complexes Synthesis, Charac-
terization and Application in Oxidation, Ph.D. thesis, Gebze Instıtue of Tech-
nology, 2007.
[2] M. Wainwright, Biotech. Histochem. (2010).
[3] C.C. Leznoff, A.B.P. Lever, Phthalocyanines: Properties and Applications, vols.
1e4, VCH, New York, 1996.
[4] N.B. McKeown, Phthalocyanine Materials Synthesis, Structure and Function,
Cambridge University Press, 1998.
[5] K. Kadish, K.M. Smith, R. Guilard, The Porphyrin Handbook, vols. 15e20, Ac-
ademic Press, Boston, 2003.
[6] M. Durmus¸ , Z. Bıyıklıoglu, H. Kantekin, Synth. Metals 159 (2009) 1563e1571.
[7] A.A. Esenpınar, M. Durmus¸ , M. Bulut, J. Photochem, Photobiol. A: Chem. 213
(2010) 171e179.
12e17.
[23] V.V. Rozhkov, M. Khajehpour, S.A. Inogradov, Inorg. Chem. 42 (2003) 4253e
4255.
_
_
[24] H.Y. Yenilmez, I. Özçes¸ meci, A.I. Okur, A. Gül, Polyhedron 23 (2004) 787e791.
[25] D.D. Perrin, W.L.F. Armarego, Purification of Laboratory Chemicals, second ed.,
Pergamon Press, Oxford, 1989.
[26] S. Liao, C. Soo, H. Ye, S. Valiyaveettil, Polym. Int. 54 (2005) 622e628.
[27] B.I. Mikhant’ev, B.K.H. Kimsanov, Dokl. Akad. Nauk Tadzh. SSR 10 (1967)
39e41.
[28] E.T. Saka, N. Yıldırım, H. Kantekin, Heteroatom Chem. 21 (2010) 456e461.
[29] Z. Bıyıklıoglu, H. Kantekin, I. Acar, Inorg. Chem. Commun. 11 (2008) 1448e1451.
[30] B. Agboola, K.I. Ozoemena, T. Nyokong, Electrochim. Acta 51 (2006) 4379e
ꢀ
ꢀ
4387.
[8] A.B.P. Lever, E.R. Milaeva, G. Speier, Leznoff CC and Lever ABP Phthalocya-
nines: Properties and Applications, vol. 3, VCH, New York, 1993, pp. 1e69.
[9] B. Meunier, Chem. Rev. 92 (1992) 1411e1456.
[31] M. Gulppi, S. Griveau, F. Bediuoi, J.H. Zagal, Electrochim. Acta 46 (2001) 3397e
3404.
ꢀ
[32] Z. Bıyıklıoglu, H. Kantekin, Dyes Pigm. 80 (2009) 17e21.
ꢀ
[10] E.T. Saka, D. Çakır, Z. Bıyıklıoglu, H. Kantekin, Dyes Pigm. 98 (2013) 255e
[33] G. Gümüs¸ , A. Gül, V. Ahsen, New J. Chem. 21 (1997) 589e594.
[34] J. Haber, M. K1osowski, J. Po1towicz, J. Mol. Catal. A: Chem. 201 (2003)
167e178.
262.
[11] B. Basu, S. Satapathy, A.K. Bhatnagar, Catal. Rev. Sci. Eng. 35 (1993) 571e
609.
[35] A.U. Ugur, A. Erdogmus, A. Koca, U. Avcıata, Polyhedron 29 (2010) 3310e3317.
[36] I.A. Akinbulu, T. Nyokong, Polyhedron 29 (2010) 1257e1270.
[37] A. Alemdar, A.R. Ozkaya, M. Bulut, Polyhedron 28 (2009) 3788e3796.
[38] J. Obirai, T. Nyokong, Electrochim. Acta 50 (2005) 5427e5434.
[39] V.B. Sharma, S.L. Jain, B. Sain, Tetrahedron Lett. 44 (2003) 383e386.
[40] N. Sehlotho, T. Nyokong, J. Mol. Catal. A: Chem. 209 (2004) 51e57.
[41] N. Sehlotho, T. Nyokong, J. Mol. Catal. A: Chem. 219 (2004) 201e207.
[42] V.N. Nemykin, V.Ya. Chernii, S.V. Volkov, N.I. Bundina, O.L. Kaliya, V.D. Li,
E.A. Lukyanets, J. Porphyrins Phthalocyanines 3 (1999) 87e98.
[43] M.H. Lim, S.W. Jin, Y.J. Lee, G.J. Jhon, W. Nam, C. Kim, Bull. Korean Chem. Soc.
22 (2001) 93e96.
[12] M. Chibwe, L. Ukrainczyk, S.A. Boyd, T.J. Pinnavaia, J. Mol. Catal. A: Chem. 113
(1996) 249e256.
[13] V.M. Kothari, J.J. Tazuma, J. Catal. 41 (1976) 180e189.
[14] T. Ichinohe, H. Miyasaka, A. Isoda, M. Kimura, K. Hanabusa, H. Shirai, Func.
Poly. 43 (2000) 63e70.
[15] T.V. Rao, K.N. Rao, S.L. Jain, B. Sain, Synth. Commun. 32 (2002) 1151e1157.
[16] M. Ozer, F. Yılmaz, H. Erer, I. Kani, O. Bekaroglu, App. Organomet. Chem. 23
(2009) 55e61.
[17] F. Zhao, J. Zhang, T. Abe, D. Wöhrle, M. Kaneko, J. Mol. Catal. A: Chem. 145
(1999) 245e256.
[18] H. Turk, Y. Cimen, J. Mol. Catal. A: Chem. 234 (2005) 19e24.
[19] Y. Cimen, H. Türk, App. Catal. A: Gen. 340 (2008) 52e58.
[44] E.M. Serwickaa, J. Po1towicza, K. Bahranowskib, Z. Olejniczakc, W. Jones, Appl.
Catal. A: Gen. 275 (2004) 9e14.
[45] C. Pratap, K. Shigeru, K. Toshinori, S. Shigeo, Polyhedron 28 (2009) 370e380.
ꢀ
[20] I. Acar, R. Bayrak, E.T. Saka, Z. Bıyıklıoglu, H. Kantekin, Polyhedron 30 (2013)
345e353.