Co(II) and Fe(II) phthalocyanines: Synthesis, characterization and catalytic activity on cyclohexene oxidation with different oxygen source

Article abstract of DOI:10.1016/j.jorganchem.2013.07.018

Peripherally tetra-substituted cobalt(II) and iron(II) phthalocyanines bearing [2-(4-methoxyphenoxy)ethoxy] groups have been synthesized and their structures have been verified by IR, ¹H and ¹³C NMR, mass and UV-vis spectroscopy tech

Full text of DOI:10.1016/j.jorganchem.2013.07.018

Journal of Organometallic Chemistry 745-746 (2013) 50e56
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Co(II) and Fe(II) phthalocyanines: Synthesis, characterization and
catalytic activity on cyclohexene oxidation with different oxygen
source
*
ꢀ
ꢀ
Ece Tugba Saka , Zekeriya Bıyıklıoglu
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:
Peripherally tetra-substituted cobalt(II) and iron(II) phthalocyanines bearing [2-(4-methoxyphenoxy)
ethoxy] groups have been synthesized and their structures have been verified by IR, 1H and 13C NMR,
mass and UVevis spectroscopy techniques. Fe(II) and Co(II) phthalocyanine complexes were tested as
catalyst for the oxidation of cyclohexene using tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic
acid (m-CPBA), aerobic oxygen, hydrogen peroxide (H2O2) and oxone (potassium peroxomonosulfate) as
oxidant. Catalytic activity of Fe(II) and Co(II) phthalocyanine complexes was compared and Fe(II)
phthalocyanine was found as the best catalyst with higher product yields and selectivity. Both catalysts
can selectively oxidize cyclohexene to give 2-cyclohexene-1-ol as major product, 2-cyclohexene-1-one
and cyclohexene oxide are minor products. The influence of substrate/catalyst ratio, temperature,
oxidant ratio and oxidant type were also investigated to find optimal reaction on cyclohexene oxidation
for getting the highest conversion. All catalytic reactions were carried out using biphasic system
(hexane:acetonitrile).
Received 18 May 2013
Received in revised form
18 June 2013
Accepted 5 July 2013
Keywords:
Phthalocyanine
Iron
Cobalt
Cyclohexene oxidation
Biphasic system
Tert-butyl hydroperoxide
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
semiconductors [2e6] in recent years. Also their use as efficient
photosensitizers in obtaining singlet oxygen is becoming especially
Phthalocyanines, formally known as tetrabenzo [5,10,15,20]-
tetraazaporphyrins, are more stable analogs of the porphyrins
and are more commonly used in industry. Phthalocyanine (Pc)
important in photodynamic therapy (PDT) of tumors [7].
Due to the oxidation products that are 2-cyclohexene-1-ol, 2-
cyclohexene-1-one and cyclohexene oxide oxidation of cyclo-
hexene has an important position among the oxidation of aromatic
compounds. These products are great importance to industrial
processes as well as fine chemical syntheses [8].
Additionally, iron(II) and cobalt(II) have been widely used as
central metal ion in metallophthalocyanine complexes to investigate
catalytic behavior on oxidation of aromatic compounds [9]. As well
as their easy preparation and low cost, iron(II) and cobalt(II)
phthalocyanine complexes show interesting catalytic activity,
because they contain redox active central metal ion. Iron(II) phtha-
molecules have a conjugated system of 18
p electrons and possess a
very high thermal and chemical stability. The structure of the
phthalocyanine ring resembles the naturally occurring porphyrins
with the only basic difference being the aza groups instead of
methine corner link [1].
The synthesis of phthalocyanine compounds has established
themselves as blue and green dyestuffs par excellence. They are
important industrial commodity, used primarily in inks, coloring
for plastics and metal surfaces, and dyestuffs for jeans and other
clothing. Although phthalocyanine molecules are widely used as
dyes and pigments the early years of discovery of them, they (Pcs)
are one of the major types of tetrapyrrole derivatives showing a
wide range of applications in various areas such as liquid crystals,
electronic devices, gas and chemical sensors, electrochromic and
electroluminescent displays, non-linear optics, photovoltaics and
locyanine complexes can react with oxygen to form
phthalocyanine complexes (PcFeIIIeOeFeIIIPc) via intermediate for-
mation of -peroxo dimer. But this dimer molecule cannot be formed
m-oxo diiron
m
for sterical reason. Then, homolytical cleavage of OeO bond pro-
duces PcFeIV ¼ O complex. Cobalt(II) phthalocyanine complexes can
also react with oxygen to achieve OeO bond formation. Because of
this, highly active cobalt(II) phthalocyanine catalysts are used for
transferring oxygen from various oxygen donors to alkanes, alkenes,
phenols and thiols in numerous studies [10e26]. Different groups
substituted phthalocyanines (especially electron withdrawing
* 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.2013.07.018

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51
groups such as halogenated, phenyl groups) have been also largely
studied for their ability in oxidation of cyclohexene [27].
CN
CN
OH
CH3O
O
In this work, we have synthesized new peripherally tetra-
substituted iron(II) (4) and cobalt(II) 5 phthalocyanines contain-
ing [2-(4-methoxyphenoxy)ethoxy] groups. We have reported on
the catalytic behavior of these complexes 4 and 5 for the cyclo-
hexene oxidation with the aim of improving product selectivity,
increasing the range of products and compare their catalytic ac-
tivity. We have used biphasic reaction system during the all the
catalytic processes to reuse these catalysts. Finally, Fe(II) and Co(II)
phthalocyanine complexes 4 and 5 are also employed as catalysts
for recycling and degradation of catalyst.
O2N
2
1
i
O
CN
CH3O
O
CN
3
2. Experimental
ii
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 [28]. 2-(4-Methoxyphenoxy)
ethanol 1, 4-nitrophthalonitrile 2 [29,30], were prepared according
to the literature procedure.
CH3O
CH3O
O
O
O
O
N
2.1. Equipment
N
N
N
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 400 MHz spectrometer in
N
N
M
N
N
CDCl3, DMSO-d6 and chemical shifts were reported (d) relative to
Me4Si as internal standard. Mass spectra were measured on a
Micromass Quattro LC/ULTIMA LCeMS/MS spectrometer. MALDIe
MS of complexes were obtained in dihydroxybenzoic acid as MALDI
matrix using nitrogen laser accumulating 50 laser shots using
Bruker Microflex LT MALDIeTOF mass spectrometer. Optical
spectra in the UVevis region were recorded with a Perkin Elmer
Lambda 25 spectrophotometer. GC Agilent Technologies 7820A
O
O
O
O
4
5
Compound
M
CH3O
Fe
Co
CH3O
equipment (30 m ꢀ 0.32 mm ꢀ 0.50
mm DB Wax capillary column,
FID detector) was used GC measurements.
Scheme 1. The synthesis of the compounds 3, 4 and 5. Reagents and conditions: (i) dry
DMF, K2CO3, 50 ꢁC, 72 h; (ii) n-pentanol, DBU, 160 ꢁC, Fe(CH3COO)2, CoCl2.
2.2. Synthesis
2.2.1. 4-[2-(4-Methoxyphenoxy)ethoxy]phthalonitrile (3)
the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (1.02 ꢀ
10ꢂ3 L, 0.68 ꢀ 10ꢂ3 mol) under a nitrogen atmosphere and held at
reflux temperature (160 ꢁC) for 24 h. After cooling to room temper-
ature, 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 column ma-
terial and chloroform as eluent. Yield: 243 mg (45%). IR (KBr pellet)
nmax/cmꢂ1: 3066 (AreH), 2919e2849 (Aliph. CeH), 1606, 1505, 1451,
1398,1337,1213,1125,1065,1031, 958, 930, 818, 744.1H NMR (CDCl3),
4-Nitrophthalonitrile 2 (1.53 g, 0.009 mol) was dissolved in
anhydrous DMF (0.025 L) under nitrogen and 4-2-(4-methoxy
phenoxy)ethanol 1 (1.51 g, 0.009 mol) was added. After stirring for
10 min, finely ground anhydrous K2CO3 (3.72 g, 0.027 mol) was
added in portions over 2 h with stirring. The reaction mixture was
stirred at 50 ꢁC for 72 h under nitrogen. Then the solution was
poured into the ice water (0.1 L). The precipitate formed was filtered
off, washed first with water until the filtrate was neutral and then
with diethyl ether and dried under vacuum over P2O5. The crude
product was recrystallized from methanol. Yield: 1.85 g (70%), mp:
142e143 ꢁC. IR (KBr pellet), nmax/cmꢂ1: 3095 (AreH), 2962e2863
(Aliph. CeH), 2234 (C^N), 1599, 1561, 1508, 1492, 1455, 1430, 1311,
1255, 1231, 1177, 1099, 1067, 1028, 969, 922, 824, 738. 1H NMR
(d: ppm): 7.48 (m, 8H, AreH), 7.05e6.78 (m, 20H, AreH), 4.22 (m,
16H, eCH2eO), 3.78 (s, 12H, OeCH3). UVevis (DMF), lmaks(log 3) nm:
358 (4.86), 610 (4.42), 704 (4.84). MALDIeTOFeMS: m/z: 1234
[M þ H]þ.
(DMSO-d6), (
1H, AreH), 6.86 (m, 4H, AreH), 4.46 (m, 2H, eCH2eO), 4.26 (m, 2H, e
CH2eO), 3.67 (s, 3H, OeCH3). 13C NMR (DMSO-d6), (
: ppm): 162.41,
d: ppm): 8.06 (d, 1H, AreH), 7.82 (d, 1H, AreH), 7.51 (d,
2.2.3. Cobalt(II) phthalocyanine (5)
d
Synthesized similarly to 4 from 3 by using anhydrous CoCl2.
Purification was achieved using column chromatography with
basic alumina as column material and chloroform:methanol (9:1)
154.22, 152.75, 136.46, 121.06, 120.84, 116.97, 116.93, 116.45, 116.07,
115.27, 106.83, 68.52, 66.92, 55.99. MS (ESþ), (m/z): 294 [M]þ.
solvent system as eluent. Yield: 0.219 g (42%). IR (KBr tablet) vmax
/
2.2.2. Iron(II) phthalocyanine (4)
cmꢂ1: 3049 (AreH), 2924e2872 (Aliph. CeH), 1609, 1508, 1479,
1453, 1344, 1229, 1126, 1096, 1068, 1033, 963, 821, 750. UVevis
(DMF), lmaks(log 3) nm: 326 (5.03), 605 (4.58), 666 (5.09).
MALDIeTOFeMS: m/z: 1237 [M þ H]þ.
4-[2-(4-Methoxyphenoxy)ethoxy]phthalonitrile (3) (0.5 g, 1.69 ꢀ
10ꢂ3 mol), anhydrous Fe(CH3COO)2 (0.073 g, 0.42 ꢀ10ꢂ3 mol)
and 0.005 L of n-pentanol were placed in a standard Schlenk tube in

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52
2.3. General procedure for the oxidation of cyclohexene
methoxyphenoxy)ethoxy]phthalonitrile 3. Second step is the
cyclotetramerization of the phthalonitrile derivative 3 in a high-
boiling solvent (n-pentanol) in the presence of a few drops DBU
as a strong base and Fe(CH3COO)2, CoCl2 at reflux temperature
under a nitrogen atmosphere afforded the iron and cobalt phtha-
locyanines 4 and 5, respectively. The structures of the target com-
pounds were confirmed using UVevis, IR, 1H NMR, 13C NMR, MS
spectroscopic data.
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 (1.21 ꢀ10ꢂ3 mol),
catalyst (4.04 ꢀ10ꢂ6 mol) and solvent mixture (0.01 L) were stirred
in a Schlenk vessel for few minutes at room temperature. Then, the
oxidant TBHP (2.02 ꢀ 10ꢂ3 mol) was 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
In the IR spectrum of 3, stretching vibrations of C^N groups
appeared as a single intense peak at 2234 cmꢂ1 as expected. In 1
H
NMR spectrum of 3, the disappearance of the OH peak of compound
1, besides presence of additional aromatic protons indicated that
nucleophilic aromatic nitro displacement was achieved. In 13C NMR
spectrum of 3 was observed the new peaks at (116.07, 115.27 ppm)
for compound 3, belonging to nitrile carbons. The molecular ion
peak of 3 was found at m/z 294 [M]þ.
least twice in the GC, 1 mL each time. Formation of products and
consumption of substrates were monitored by GC.
3. Results and discussion
The synthesis of the iron(II) and cobalt(II) phthalocyanines 4 and
5 were achieved by cyclotetramerization of dinitrile derivative 3.
Cyclotetramerization of compound 3 to the iron(II) and cobalt(II)
phthalocyanines 4 and 5 were confirmed by the disappearance of
3.1. Synthesis and characterization
The synthesis of the iron(II) and cobalt(II) phthalocyanines are
shown in Scheme 1. The first step is the synthesis of 4-[2-(4-
Fig. 1. Mass spectrum of complexes 4 and 5.

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E.T. Saka, Z. Bıyıklıoglu / Journal of Organometallic Chemistry 745-746 (2013) 50e56
53
the C^N vibration at 2234 cmꢂ1. The 1H NMR spectrum of iron(II)
O
OH
phthalocyanine 4 was similar and the integral ratio of the aromatic
protons to aliphatic protons were similar to corresponding phtha-
lonitrile derivative 3. The 1H NMR spectrum of iron(II) phthalocy-
anine 4 indicated the aromatic protons at 7.48, and 7.05e6.78 ppm
and aliphatic protons at 4.22 and 3.78 ppm. The 1H NMR spectrum
of cobalt phthalocyanine 5 could not be taken due to the para-
magnetic cobalt(II) centers [31]. In the mass spectrum of iron and
cobalt phthalocyanines 4 and 5, the presence of molecular ion
peaks at m/z 1234 [M þ H]þ and 1237 [M þ H]þ respectively (Fig. 1),
confirmed the proposed structures.
The electronic absorption spectra of the iron and cobalt phtha-
locyanines 4 and 5, in DMF at room temperature are shown in Fig. 2.
The iron and cobalt phthalocyanines 4 and 5 showed intense single
Q-bands at 704 and 666 nm, and B-bands at 358 and 326 nm,
respectively in DMF.
Oxidant
O
Catalyst (MPc)
Cyclohexene
2-cyclohexene-1-one
2-cyclohexene-1-ol
cyclohexenoxide
Fig. 3. Product formed through oxidation of cyclohexene by TBHP, m-CPBA, H2O2 and
oxone in the presence of complex 4 and 5.
maximum conversion of cyclohexene, the oxidation reactions were
carried out varying, substrate/catalyst ratio, the reaction tempera-
ture, oxidant ratio and oxidant type. Fig. 4a and b shows that the
changing of product yield with reaction time on the oxidation of
cyclohexene by TBHP with complex 4 and 5. When complex 4 was
used as catalyst in oxidation reactions, cyclohexene converted to 2-
cyclohexene-1-ol (68%) as main product and 2-cyclohexene-1-one
(18%) and cyclohexene oxide (12%). In addition 2-cyclohexene-1-
ol (51%) as main product and 2-cyclohexene-1-one (28%) and
cyclohexene oxide (8%) were produced by using complex 5 in the
reactions. That is mean; complex 4 (98%) had higher total conver-
sion than complex 5 (87%). These results show that, the central
metal ion of the catalysts could be effect the catalytic oxidation
reactions. The important role played by these catalysts is also
evident from the any conversion found in the control experiment
carried out in the absence of the catalyst. Although the yield of the
three products increased during 3 h, there was no raising
the product conversion after 3 h. This constant conversion is due to
the degradation of the Co(II)Pc and Fe(II)Pc catalyst by oxidant,
with time.
As the other parameters were kept constant, the molar ratio was
carried out in the range of 300e1500 to determine the influence of
substrate to metal ions. The experimental conditions were 90 ꢁC,
2.02 ꢀ 10ꢂ3 mol TBHP, 0.01 L solvent mixture (hexane:acetonitrile;
6:4) for 3 h. As we expected, the reaction rate increased with
decreasing of the substrate/catalyst molar ratio (Table 1). Substrate/
catalyst ratio on the oxidation course gave same main product (2-
cyclohexene-1-ol) with selectivity of 68% for complex 4 and 51%
for complex 5.
3.2. Catalytic studies
3.2.1. Oxidation of cyclohexene with 4 and 5
The catalytic activities of complex 4 and 5 were examined in
hexane:acetonitrile biphasic system. Cyclohexene as substrate is
in hexane phase, complex 4 or 5 as catalyst is in acetonitrile phase.
Two phase mixture is magnetically stirring at 900 rpm to provide
optimum contact between these phases. Due to verifying an
essential role of the catalysts on the oxidation course, some re-
actions indicate that substrate oxidation with oxidants did not
realize when the catalysts were not added in the reaction. After the
addition of TBHP, the air inside the Schlenk tube was discharged
under vacuum and refluxed at different temperatures (25, 50, 70
and 90 ꢁC). Above 20 ꢁC, the deep blue color of solution changed to
pale brown. At the end of the reaction, the oxidation products were
isolated from the acetonitrile layer by cooling the reaction mixture
below 20 ꢁC followed by phase separation of the resulting biphasic
system. While the cyclohexene and its oxidation products were in
hexane phase, complex 4 or 5 were stayed in the acetonitrile
phase. The upper colorless hexane phase was removed using a
syringe. The acetonitrile phase was extracted with dichloro-
methane (2 ꢀ 3 mL). All catalytic reactions were carried out at least
twice. Samples taking from the reaction media show that 2-
cyclohexene-1-ol as major product, 2-cyclohexen-1-one and
cyclohexene epoxide minor products to identifying the products
with using gas chromatography by both spiking and comparison
with standards (Fig. 3). The absence of both catalysts 4 and 5 in
hexane phase was controlled by UVevis absorption, due to the
phthalocyanine complexes have strong B and Q-band in UVevis
religion (about 300e800 nm).
The influence of the reaction temperature on the oxidation of
cyclohexene was investigated for both catalysts 4 and 5 using in the
temperature range of 25e90 ꢁC with ox./subst./cat. ¼ 500/200/1
and TBHP, 0.01 L solvent mixture (hexane:acetonitrile; 6:4) during
3 h (Table 2). According to the results of Table 2, as the reaction
temperature was raised the catalyst activity increased. It is notable
that the increasing temperature could influence the conversion of
Table 1
All comparative studies of the catalytic activity of 4 and 5 for
cyclohexene oxidation are shown in Tables 1e4. In order to obtain
Amount of substrate effect of cyclohexene oxidation with complex 4 and 5.
Catalyst Subs./cat. Alcohola Ketoneb Epoxidec Tot.
conv. (%)
TONd TOFe
(hꢂ1
)
1,4
4
5
4
5
4
5
4
5
4
5
300/1
600/1
68
51
63
48
57
44
39
23
30
20
18
28
18
20
15
18
15
15
11
8
12
8
7
7
7
5
4
3
3
1
98
293
259
680
448
709
600
694
489
658
433
98
87
87
88
75
79
67
58
41
44
29
4
5
1,2
1
226
149
236
200
231
163
219
144
900/1
0,8
0,6
0,4
0,2
0
1200/1
1500/1
Conversion was determined by GC.
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexenoxide.
b
300
350
400
450
500
550
600
650
700
750
800
c
Wavelength (nm)
d
TON ¼ mole of product/mole of catalyst.
e
Fig. 2. UVevis spectrum of 4, 5 in DMF.
TOF ¼ mole of product/mole of catalyst ꢀ time.

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Table 2
Table 4
Temperature effect of cyclohexene oxidation with complex 4 and 5.
Different oxidant effect of cyclohexene oxidation with complex 4 and 5.
Catalyst T (ꢁC) Alcohola Ketoneb Epoxidec Tot. conv. (%) TONd TOFe (hꢂ1
)
Catalyst Oxidant )
Alcohola Ketoneb Epoxidec Tot. conv. (%) TONd TOFe (hꢂ1
4
5
4
5
4
5
4
5
25
50
70
90
22
19
38
33
50
47
68
51
11
9
5
5
7
38
33
63
55
81
72
98
87
113 38
98 33
4
5
4
5
4
5
4
5
4
5
TBHP
68
51
19
15
30
28
18
28
15
12
18
16
e
12
8
11
7
14
15
e
98
87
45
37
62
59
e
680 226
448 149
134 27
110 36
185 61
176 58
18
13
20
15
18
28
188 63
164 55
242 81
215 72
293 98
259 87
H2O2
9
11
10
12
8
m-CPBA
Air oxygen e
e
e
e
e
e
e
e
e
Oxone
17
13
14
15
9
5
40
31
119 40
92 31
Conversion was determined by GC.
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexenoxide.
b
Conversion was determined by GC.
c
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexenoxide.
d
b
TON ¼ mole of product/mole of catalyst.
e
c
TOF ¼ mole of product/mole of catalyst ꢀ time.
d
TON ¼ mole of product/mole of catalyst.
e
TOF ¼ mole of product/mole of catalyst ꢀ time.
2-cyclohexene-1-ol. The overall conversion was increased 60% for
complex 4 and 54% for complex 5 when the temperature was raised
25e90 ꢁC. The maximum conversion (98%) was obtained with
TON ¼ 293 for complex 4 and (87%) was obtained with TON ¼ 259
for complex 5 at 90 ꢁC.
The other significant parameter to impressing the oxidation of
cyclohexene is the oxidant ratio. The influence of oxidant/catalyst
ratio in the range of 500/1e1200/1 was also worked (Table 3).
When the increasing oxidant/catalyst ratio from 500/1 to 700/1, the
rate of the reaction increased. In contrast, while the catalytic
oxidation was processing from 700/1 to 1500/1, the conversion
inclined to decreasing. At this stage, it is possible that the coordi-
nation around the iron and cobalt ion can change and produce
inactive intermediate species.
To study the oxygen source effect, the experiments were carried
out using with TBHP, m-CPBA, H2O2, aerobic oxygen and oxone
(Table 4 and Fig. 5). The results indicated that catalysts 4 and 5
show the highest activity with TBHP (TOF: 226 and 149 for catalyst
4 and 5). When we use oxone as an oxidant, it is monitored that fast
degradation of the phthalocyanine ring 4 and 5 were observed.
Actually, the color of reaction went from the dark blue color of the 4
or 5 catalyst to colorless, suddenly following addition of this
oxidant, therefore oxidation was not worked efficiently using this
oxidant and complex 4 or 5. By the checking the conversion, we
could explain that the degradation of ring with m-CPBA is said that
is a lower degree compared to H2O2. There was no conversion for
complex 4 and 5 when the air oxygen was used as an oxidant.
Similar situation has been reported for the cyclohexene oxidation
with Fe(II) and Co(II) phthalocyanine catalysts [26].
Oxidation state of the cobalt ion in CoPc is 2þ. During the cat-
alytic cycle both CoPc and FePc complexes form high-spin octahe-
drally coordinated complexes due to the low coordination
capabilities of axially coordinated species. Consequently, Feþ3 ion in
FePc (d5,eg2, t23g) has almost no crystal field stabilization energy
where as Coþ2 ion in CoPc (d7,eg2, t25g) has some. Therefore, Feþ3 ion-
ligand breaking process to form an oxo-iron complex, which is the
catalytically active species, requires less energy than Coþ2 ion-
ligand breaking process. This is the reason why FePc is more cata-
lytically active [20].
For the recycling experiments, cyclohexene (1.21 ꢀ10ꢂ3 mol),
complex 4 (4.05 ꢀ10ꢂ6 mol) or complex 5 (4.04 ꢀ10ꢂ6 mol) and
Table 3
Amount of oxidant effect of cyclohexene oxidation with complex 4 and 5.
Catalyst Oxidant/catalyst Alcohola Ketoneb Epoxidec Tot.
conv. (%)
TONd TOFe
(hꢂ1
)
4
5
4
5
4
5
4
5
4
5
500/1
700/1
68
51
54
44
40
35
27
24
18
15
18
28
17
20
17
17
17
14
10
7
12
8
10
6
7
5
4
4
3
2
98
293 98
87
81
70
64
57
48
42
31
24
259 87
242 81
209 70
191 64
170 56
143 48
125 42
92 31
900/1
1200/1
1500/1
71 24
Conversion was determined by GC.
a
2-Cyclohexene-1-ol.
2-Cyclohexene-1-one.
Cyclolohexenoxide.
b
c
d
TON ¼ mole of product/mole of catalyst.
Fig. 4. Time-dependent conversion of cyclohexene oxidation a) for catalyst 4 b) for
catalyst 5.
e
TOF ¼ mole of product/mole of catalyst ꢀ time.

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E.T. Saka, Z. Bıyıklıoglu / Journal of Organometallic Chemistry 745-746 (2013) 50e56
55
Table 5
Catalytic activities toward the homogenous oxidation of cyclohexene of some pre-
viously reported catalyst.
Catalyst
Rxn
time (h)
Rxn
temp. (ꢁC)
Oxidant
Conv. (%)
Ref.
rth
O2
w55
w30
89
29
45.3
[35]
a
Fe(tbpcH2
)
)
24
a
Co(tbpcH2
Fe(TMPb)Cl
FeTMpyP
Cl16FePcc
FePcc
10 min
16
8
25
rtf
m-CPBA
PhIO
TBHP
[36]
[37]
[10]
nri
CoPcc
Co[N^O]2 Cu[N^Od]2
8
75
H2O2
27.6
43.50
42.7
91
92
85
[38]
[Co(Me2salpnMe2e)]
Co(salen)ePOM
Co(II)Pcf
8
6
3
3
40
60
90
90
TBHP
H2O2
TBHP
TBHP
[39]
[40]
[24]
[26]
Fig. 5. The oxidant effect on cyclohexene oxidation.
Co(II)Pcg
TBHP (2.02 ꢀ10ꢂ3 mol) in 10 mL of hexane:acetonitrile solution
(6:4) and the reaction was started. Oxidation products of cyclo-
hexene from the first cycle were extracted and the reaction was
going on ten hours. GC analysis indicated less than 8% conversion of
cyclohexene for the third cycle with complex 4 and second cycle
with complex 5 (Fig. 6). We observed after each cyclic experiment,
the conversion of cyclohexene decreased substantially. The fast
deactivation of catalysts was due to the oxidative degradation of
catalysts in the presence of TBHP. Moreover, the degradation of the
catalysts was also evidenced by lighter green solutions after each
cycle. We also found that there was almost no TBHP remaining in
the reaction medium at the end of reactions in which the number of
initial moles of TBHP exceeded the number of initial moles of
cyclohexene. This finding indicates that some unproductive
decomposition of TBHP by the catalyst and/or degradation of cat-
alysts by TBHP occurred.
Table 5 indicate that the successful performance of the complex
4 and 5 on the oxidation catalysis when it is compared to some
other containing iron and cobalt metal catalyst. We have also
recorded the best results in terms of TOF in literature for homog-
enous oxidation of cyclohexene with TBHP. FeePc was also deter-
mined as the best successful catalyst on this work.
UVevis spectra of the metallophthalocyanine complexes have
been a subject of several works [32,33]. Their spectra consist of
sharp characteristic Q-band because the monomeric forms in the
a
tbpcH2 ¼ tetra-tert-butylphthalocyanine.
TMP ¼ meso-tetramesitylporphinato.
Pc ¼ phthalocyanine.
b
c
d
e
f
N^O ¼ 2-pyrazinecarboxylic acid.
Me2salpnMe2 ¼ N,N-bis-(
a-methylsalicylidene)-2,2-dimethylpropane-1.
Pc ¼ (1,4-dioxa-8-azaspiro[4.5]dec-8-yl)ethoxy]phthalocyanine.
Pc ¼ 4{2-[3-(diethylamino)phenoxy]ethoxy}phthalocyanine.
rt ¼ Room temperature.
g
h
i
nr ¼ Not reported.
phthalocyanine complex with sharp Q-band at 671 and 664 nm,
before the starting catalytic reactions. After addition of oxidant,
these Q-bands decrease intensity, broaden and finally disappear. As
we interpreted by the decrease in the Q-band intensity, it can be
said that the oxidation is likely accompanied by some degradation
of the catalysts. Fig. 8 shows that the Q-band shifted from 664 to
669 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)ePc to Co(III)ePc [18]. There was no peak around
480 nm suggests ring oxidation both spectra of these complexes 4
and 5. Thus addition of TBHP to solutions of MePc (M:Co(II) and
Fe(II)) resulted in only metal and not ring oxidation of MePc. As
catalysis progressed there was a gradual decrease in the intensity of
the Q-band of the MePc catalyst, suggesting catalyst degradation as
is typical [34] of MPc catalysts in homogenous catalysis. The
decomposition of the phthalocyanine complex during the oxidation
of cyclohexene is probably a result of the attack of the phthalocy-
anine ring by the ROꢃ and ROOꢃ radicals (Fig. 9). The color of the
absence of oxygen source. Due to the formation of m-oxo dimeric
species (PcFeIIIeOeFeIIIPc), the spectra broaden and shift with us-
ing oxygen source. Figs. 7 and 8 show that spectral changes of these
catalysts 4 and 5 during the catalytic processes. In the spectrum of
Fig. 7 shows that Q-band split 668 and 704 nm before adding the
oxidant. Immediately after adding the oxidant, this Q-band reduces
and finally disappears. Fig. 8(a) is typical the monomeric form of
Fig. 7. Time-dependent changes in the visible spectrum of the oxidized complex 4
observed on addition of TBHP (2.02 ꢀ 10ꢂ3 mol) to a reaction mixture containing
1.21 ꢀ10ꢂ3 mol cyclohexene and 4.05 ꢀ10ꢂ6 mol complex 4 catalyst in 10 mL solvent
mixture: (b) 90 min; (c) 180 min after addition of TBHP. All spectra for the oxidized
complex 4 were taken after sixfold dilution with DMF. (a) Visible spectrum of (non-
oxidized) complex 4.
Fig. 6. Conversion of cyclohexene catalyzed by Fe(II)Pc in three and Co(II)Pc in two
recycling experiments after addition of new portions of cyclohexene
(1.21 ꢀ10ꢂ3 mmol) and TBHP (2.02 ꢀ 10ꢂ3 mmol).

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56
E.T. Saka, Z. Bıyıklıoglu / Journal of Organometallic Chemistry 745-746 (2013) 50e56
Acknowledgment
This study was supported by The Research Fund of Karadeniz
Technical University, Project no. 9666, Trabzon, Turkey.
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