Peripherally tetra-{2-(2,3,5,6-tetrafluorophenoxy)ethoxy} substituted cobalt(II), iron(II) metallophthalocyanines: Synthesis and their electrochemical, catalytic activity studies

Article abstract of DOI:10.1016/j.jorganchem.2016.11.022

In this study, new electron-withdrawing peripherally tetra {2-[2,3,5,6-tetrafluorophenoxy]ethoxy} groups substituted Co^IIPc and Fe^IIPc have been synthesized for the first time and their structures have been characterized by using IR,

Full text of DOI:10.1016/j.jorganchem.2016.11.022

Journal of Organometallic Chemistry 828 (2017) 59e67
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Peripherally tetra-{2-(2,3,5,6-tetrafluorophenoxy)ethoxy} substituted
cobalt(II), iron(II) metallophthalocyanines: Synthesis and their
electrochemical, catalytic activity studies
Ay s¸ e Akta s¸ Kamilo gꢀ lu , Irfan Acar , Zekeriya Biyiklioglu , Ece Tu gꢀ ba Saka a
a
b
,
*
a
_
a
Department of Chemistry, Faculty of Sciences, Karadeniz Technical University, 61080, Trabzon, Turkey
Department of Energy Systems Engineering, Of Faculty of Technology, Karadeniz Technical University, 61830, Of, Trabzon, Turkey
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 August 2016
Received in revised form
In this study, new electron-withdrawing peripherally tetra {2-[2,3,5,6-tetrafluorophenoxy]ethoxy}
II
II
groups substituted Co Pc and Fe Pc have been synthesized for the first time and their structures have
1
been characterized by using IR, H NMR, mass and UVeVis spectroscopy techniques. Electrochemical
8
November 2016
II
II
properties of Fe Pc and Co Pc were investigated by using cyclic voltammetry (CV) and square wave
voltammetry (SWV) techniques. Voltammetric analyses of phthalocyanines supported the proposed
structure of the synthesized complexes. Iron and cobalt phthalocyanines showed metal and ligand based
reduction reactions as expected. Also Co(II) and Fe(II) phthalocyanine complexes (1,2) were examined as
a catalyst for the oxidation of benzyl alcohol with changing different parameters to determine the
optimal conditions.
Accepted 11 November 2016
Available online 14 November 2016
Keywords:
Phthalocyanine
Cobalt
Iron
© 2016 Elsevier B.V. All rights reserved.
Cyclic voltammetry
Electrochemistry
Benzyl alcohol
1. Introduction
[16], electrochemical and spectroelectrochemical studies [17], as
catalysts in various chemical reactions [18], liquid crystals [19] and
Phthalocyanines (Pcs) having conjugated 18
p
electron system,
chemical sensor [20].
exhibit growing attention as a subject for their excellent physical
and chemical properties which highly resist to heat, light, non-
oxydizing acids and bases [1]. Unsubstituted phthalocyanines are
insoluble in organic solvents [2]. Solubility of phthalocyanines in
water or polar solvents can be improve by attaching sulfo [3] or
quaternary ammonium groups [4], crown ethers [5], long
substituted alkyl [6], alkoxy [7], alkylthio [8], macrocyclic groups
Fluorine substituted phthalocyanines affect the electronic
structure, reactivity and application of phthalocyanines [21e23].
Additionally, electron withdrawing effect of fluorine atoms in
substituted groups affects the electrochemical properties of
phthalocyanines. Introducing electron withdrawing fluorine
groups to the peripheral position of the phthalocyanines generally
shifts the redox processes of the complexes towards positive po-
tentials [24,25]. A positive shift of the redox processes of phthalo-
cyanines are important in electrocatalytic applications of the
complexes [26].
[9] peripherally or non-peripherally position on the Pc ring. Espe-
cially, fluorinated metallophthalocyanines are known good solu-
bility different solvent for example polar and apolar solvents
[
10e13]. In recent years, to enhance the solubility of Pcs in protic
Oxidation of alcohols to corresponding aldehydes and ketones
as representative functional group transformations plays vital role
in organic synthesis [27]. The selective oxidation of alcohols using
different types of oxidants has been proposed to replace the pre-
sent oxidation processes that use stoichiometric quantities of
inorganic oxidants to reduce environmental impact [28e30]. Con-
version of benzyl alcohol into aldehydes, quionones and acids by
catalytic oxidation with homogeneous catalysts has been widely
concerned and researched [31e34]. As a typical product of alcohol
oxidation, benzaldehyde (BzA) is widely used for the
or non-protic organic solvents, many axially substituted phthalo-
cyanines have been synthesized [14,15]. Soluble phthalocyanines
have gained considerable importance for a number of their medical
or industrial application areas such as, photodynamic therapy
(
PDT) for treatment of the cancer cells as a photodynamic agent
*
Corresponding author.
E-mail address: acar_irfan_2000@yahoo.com (I. Acar).
_
http://dx.doi.org/10.1016/j.jorganchem.2016.11.022
022-328X/© 2016 Elsevier B.V. All rights reserved.
0

60
A.A. Kamilo gꢀ lu et al. / Journal of Organometallic Chemistry 828 (2017) 59e67
manufacturing of odorant, pharmaceutical intermediates, dyestuff
and agrochemicals.
2. Experimental
In this study, benzyl alcohol is converted to benzaldehyde (as
major product) and the other products by metallophthalocyanine
complexes with an oxygen source. Halogenated substituents of
metallophthalocyanine complexes become important in several
fields of science and industry. Halogen substituents can partici-
pate in intermolecular interactions and control molecular recog-
nition processes [35]. Due to these electron attraching
substituents, Co(II) and Fe(II) phthalocyanine complexes
employee the active catalysts during the benzyl alcohol oxidation
reactions. In this paper, we have aimed the synthesis and char-
acterization of new fluorine substituted cobalt(II) and iron(II)
complexes. Then, we have examined catalytic activity on benzyl
alcohol oxidation and electrochemical properties of cobalt(II) and
iron(II) phthalocyanines.
2.1. Materials
4-{2-[2,3,5,6-tetrafluorophenoxy]ethoxy}phthalonitrile were
synthesized according to the literature [36]. All reagents and sol-
vents were of reagent grade quality and were obtained from
commercial suppliers. All solvents were dried and purified as
described by Perrin and Armarego [37].
2.2. Equipment
The IR spectra were recorded on a Perkin Elmer 1600 FT-IR
spectrophotometer using KBr pellets. H NMR spectra was recor-
ded on a Varian Mercury 400 MHz spectrometer in CDCl
shifts were reported (
1
3
. Chemical
d
) relative to Me Si as internal standard. Mass
4
ꢀ
Fig. 1. The synthetic route of the Co(II) and Fe(II) meallophthalocyanines. (i) n-pentanol, DBU, 160 C.

A.A. Kamilo gꢀ lu et al. / Journal of Organometallic Chemistry 828 (2017) 59e67
61
Fig. 2. UVeVis spectrum of Co(II)
1 and Fe(II) 2 phthalocyanines in THF
ꢂ6
ꢂ3
(
Concentration ¼ 10 ꢁ 10 mol dm ).
Table 1
Voltammetric data of the phthalocyanines. All voltammetric data were given versus
SCE.
Complexes
Redox processes
aE1/2
bD
E
p
(mV)
cD
E
1/2
II
II 2ꢂ
I
2ꢂ 1ꢂ
Fe Pc
[Fe Pc ]/[Fe Pc
]
ꢂ0.57
ꢂ0.93
ꢂ1.17
0.59
142
168
148
214
212
148
172
117
1.16
I
2ꢂ 1ꢂ
I
3ꢂ 2ꢂ
[
[
[
[
Fe Pc
]
/[Fe Pc
]
I
3ꢂ 2ꢂ
I
4ꢂ 3ꢂ
Fe Pc
]
/[Fe Pc
]
II 2ꢂ
III 2ꢂ 1þ
Fe Pc ]/[Fe Pc
]
III 2ꢂ 1þ
III 1ꢂ 2þ
]
Fe Pc
]
/[Fe Pc
1.08
II
II 2ꢂ
I
2ꢂ 1ꢂ
Co Pc
[Co Pc ]/[Co Pc
]
ꢂ0.29
ꢂ1.10
0.74
1.03
I
2ꢂ 1ꢂ
I
3ꢂ 2ꢂ
[
[
Co Pc
]
/[Co Pc ]
II 2ꢂ
II 1ꢂ 1þ
]
Co Pc ]/[Co Pc
a
ꢂ1
E
D
D
1/2 values ((Epa þ Epc)/2) were given versus SCE at 0.100 Vs scan rate in DCM.
¼ Epa ꢂ Epc
1/2 ¼ E1/2 (first oxidation) ꢂ E1/2 (first reduction).
b
c
E
E
p
.
II
-1
Fig. 3. (a) Cyclic voltammogram of Fe Pc recorded at 0.100 Vs scan rate on a Pt
II
working electrode in DCM/TBAP. (b) Cyclic voltammogram of Co Pc recorded at
spectra were measured on a MALDI-MS of complexes were ob-
tained in dihydroxybenzoic acid as MALDI matrix using nitrogen
laser accumulating 50 laser shots using Bruker Microflex LT MALDI-
TOF mass spectrometer. Optical spectra in the UVeVis region were
recorded with a Perkin Elmer Lambda 25 spectrophotometer. GC
Agilent Technologies 7820A equipment (30 m ꢁ 0.32 mm x
1
0
.100 Vs- scan rate on a Pt working electrode in DCM/TBAP.
was stirred in a Schlenk vessel for few minutes at room tempera-
ꢂ3
ture. The oxidant TBHP (1.78 ꢁ 10 mol) was then added and the
reaction mixture was stirred for the desired time. The samples
0
.50
mm DB Wax capillary column, FID detector) was used GC
(
0.0005 L) were taken at certain time intervals. Each sample was
injected at least twice in the GC, 1 L each time. Formation of
products and consumption of substrates were monitored by GC.
measurements.
m
2.3. Electrochemical measurements
2.5. Synthesis
All electrochemical measurements were carried out with Gamry
Interface 1000 potentiostat/galvanostat utilizing a three-electrode
2.5.1. General procedures for metallophthalocyanine derivatives
(1,2)
ꢀ
configuration at 25 C. The working electrode was a Pt disc with a
2
surface area of 0.071 cm . A Pt wire was served as the counter
A mixture of 4-{2-[2,3,5,6-tetrafluorophenoxy]ethoxy}phthalo-
nitrile (0.15 g, 0.45 mmol), anhydrous metal salts CoCl2 (0.030 g,
0.23 mmol), Fe(CH COO) (0.040 g, 0.23 mmol)] and six drops of
electrode and saturated calomel electrode (SCE) was employed as
the reference electrode and separated from the bulk of the solution
by a double bridge. Electrochemical grade tetrabuthylammonium
perchlorate (TBAP) in extra pure dichloromethane (DCM) was
3
2
1.8-diazabicyclo[5.4.0]undec-7-ene (DBU) in 2 ml of dry n-pentanol
ꢀ
was heated and stirred at 160 C in a Schlenk tube for 24 h under N .
2
employed as the supporting electrolyte at a concentration of
After cooling to room temperature the reaction mixture was
refluxed with ethanol to precipitate the product which was filtered
ꢂ3
0
.10 mol dm
.
2 5
off and dried in vacuo over P O .
2.4. Performance of the catalysts
2.5.2. Cobalt(II) phthalocyanine (1)
Experiments were carried out in a thermostated Schlenk vessel
Compound 1 was accomplished by the general procedure for
equipped with a condenser and stirrer. The solution of benzyl
metallophthalocyanines. The obtained green solid product was
alcohol and catalyst in solvent was purified with bubbling nitrogen
purified with column chromotography over the aluminium oxide
gas to remove the oxygen.
A
mixture of benzyl alcohol
by using of chloroform as eluent. Yield: 0.075 g (48%). IR (KBr
ꢂ3
ꢂ6
ꢂ1
(
2.14 ꢁ 10 mol), catalyst (3.56 ꢁ 10 mol) and solvent (0.01 L)
Tablet),
n/cm : 3076 (AreH), 2926e2874 (Aliph. CeH), 1738, 1640

62
A.A. Kamilo gꢀ lu et al. / Journal of Organometallic Chemistry 828 (2017) 59e67
TOF-MS m/z: 1403.1 [M þ H]þ.
2.5.3. Iron(II) phthalocyanine (2)
Compound 2 was accomplished by the general procedure for
metallophthalocyanines. The obtained green solid product was
chromatographed on silicagel plate with chloroform:methanol
ꢂ1
(100:8) as eluents. Yield: 0.083 g (53%). IR (KBr Tablet),
n
/cm
:
3
1
077 (AreH), 2927e2879 (Aliph. CeH), 1640 (C]N), 1607 (C]C),
511, 1484, 1452, 1397 (Ar CeF), 1367, 1336, 1270, 1227, 1172 (CeO),
1
1067, 938, 823, 745, 712. H-NMR (CDCl
3
), (
d:ppm): 7.42e7.24 (m,
4H, AreH), 7.12e6.60 (m, 12H, AreH), 4.49 (m, 8H, eCH
2
eO), 4.12
(
(
m, 8H, eCH
2
eO). UVeVis (THF):
l
max, nm (log ε): 698 (4.95), 561
þ
4.36), 363 (4.94). MALDI-TOF-MS m/z: 1400 [M þ H] .
3. Results and discussion
3.1. Synthesis and characterization
The synthetic pathways and structure of metallophthalocyanine
complexes (1,2) were shown in Fig. 1. Metallophthalocyanines (1,2)
were synthesized by the reaction of phthalonitrile derivative with
corresponding metal salts CoCl
2 3 2
and Fe(CH COO) in n-pentanol
and DBU under N atmosphere. The characterizations of all new
2
compounds were carried out by the combination of several
1
methods such as UVeVis, IR, H NMR spectra and mass (MALDI-TOF
technique) spectrometries.
In the IR spectrum, after the conversion of the dinitrile deriva-
tive to the metallophthalocyanine (1,2) was clearly consist of by the
ꢂ1
disappearance of the intense C^N stretching band at 2229 cm
.
The NMR measurements of the compound 1 was not be able to take
1
into precluded owing to its paramagnetic nature [38]. In the
H
NMR spectra of the compound 2 were recorded in deuterated
chloroform. The resonance of aromatic protons were appeared
between 7.42 and 6.60 ppm and the aliphatic protons were
observed between 4.49 and 4.12 ppm for compound 2. In the
MALDI-mass spectrum of phthalocyanine complexes (1,2) were
confirmed the presence of molecular ion peaks at m/z ¼ 1403.1
þ
þ
[
M þ H] Fig. S1 and 1400 [M þ H] Fig. S2, respectively.
II
Fig. 4. (a) The plot of square root of scan rate versus peak current for Fe Pc. (b) The
The electronic spectra of the phthalocyanines have two strong
II
plot of square root of scan rate versus peak current for Co Pc.
absorption bands in UVeVis spectroscopy. One of them is in the
visible region at 600e700 nm (Q band) due to electronic transi-
*
tions from
p
-highest occupied molecular orbital (HOMO) to
p
-
(
1
(
C]N), 1608 (C]C), 1512, 1486, 1453, 1409 (Ar CeF), 1368, 1343,
278, 1236, 1172 (CeO), 1086, 1071, 939, 870, 822, 750, 712. UVeVis
THF): max, nm (log ε): 662 (5.03), 601 (4.52), 329 (4.98). MALDI-
lowest unoccupied molecular orbital (LUMO) energy levels, and
the other one is in the UV region at about 300e500 nm (B or Soret
l
*
band) due to transitions from deeper
p
-HOMO to
p
-LUMO energy
Table 2
Amount of substrate effect of benzyl alcohol oxidation with complex 1 and 2.
Catalyst
Subs./Cat.
600/1
Aldehydea
Quinoneb
Acidc
Tot. conv. (%)
TONd
TOFe (hꢂ1
)
1
2
1
2
1
2
1
2
74
73
67
58
57
49
48
45
40
30
e
5
8
5
8
4
6
4
6
4
6
e
16
11
13
9
8
7
6
5
5
5
95
92
85
75
69
62
58
56
49
41
e
570
552
680
600
690
620
696
672
784
656
e
190
184
226
200
230
206
232
224
261
218
e
800/1
1000/1
1200/1
1600/1
600/1
1
2
Without catalysts
e
Conversion was determined by GC.
a
Yield of Benzaldehyde.
Yield of Benzoquinone.
Yield of Benzoic Acid.
b
c
d
TON ¼ mole of product/mole of catalyst.
e
TOF ¼ mole of product/mole of catalyst ꢁ time.

A.A. Kamilo gꢀ lu et al. / Journal of Organometallic Chemistry 828 (2017) 59e67
63
Table 3
Amount of oxidant effect of benzyl alcohol oxidation with complex 1 and 2.
Catalyst
Oxidant/catayst
500/1
Aldehydea
Quinoneb
Acidc
Tot. conv. (%)
TONd
TOFe (hꢂ1
)
1
2
1
2
1
2
1
2
1
2
1
2
77.8
79.3
77.7
73.7
86.1
83.7
86.6
85.0
86.2
82.3
e
5.2
8.7
4.9
8.7
5.5
8.7
5.4
10
7.1
10
e
16.8
11.9
14.8
11.2
13.8
10.1
12.7
12
95
92
81
80
72
69
55
50
42
38
e
570
552
486
480
432
414
374
300
252
228
e
190
184
162
160
144
138
124
100
84
800/1
1200/1
1600/1
2000/1
11.9
10.5
e
76
e
Without
oxidant
e
e
e
e
e
e
Conversion was determined by GC.
a
Selectivity of Benzaldehyde.
Selectivity of Benzoquinone.
Selectivity of Benzoic Acid.
b
c
d
TON ¼ mole of product/mole of catalyst.
e
TOF ¼ mole of product/mole of catalyst ꢁ time.
Table 4
Temperature effect of benzyl alcohol oxidation with complex 1 and 2.
ꢀ
Aldehydea
Quinoneb
Acidc
TONd
TOFe (hꢂ1
)
Catalyst
T ( C)
25
Tot. conv. (%)
1
2
1
2
1
2
1
2
61.4
63.5
77.8
79.3
67.7
63.9
55.3
52.6
e
10.8
9.6
16.8
11.9
15.2
9.8
63
65
95
92
59
61
47
38
378
390
570
552
354
366
282
228
126
130
190
184
118
122
94
5.2
5.2
8.7
5.0
8.1
e
50
70
90
10.6
7.9
7.8
76
Conversion was determined by GC.
a
Selectivity of Benzaldehyde.
Selectivity of Benzoquinone.
Selectivity of Benzoic Acid.
b
c
d
TON ¼ mole of product/mole of catalyst.
e
TOF ¼ mole of product/mole of catalyst ꢁ time.
Table 5
Different oxidant effect of benzyl alcohol oxidation with complex 1 and 2.
Catalyst
Oxidant
TBHP
Aldehydea
Quinoneb
Acidc
Tot. conv. (%)
TONd
TOFe (hꢂ1
)
Selectivity (% aldehyde)
1
2
1
2
1
2
1
2
74
73
34
29
43
38
e
5
8
4
e
12
6
16
11
10
8
95
92
48
37
55
49
e
570
552
288
222
330
294
e
190
184
96
74
110
98
74
73
70.8
78.3
78.2
77.5
e
H
2
O
2
m-CPBA
e
5
e
Air oxygen
e
e
e
e
e
e
e
e
e
Conversion was determined by GC.
a
Yield of Benzaldehyde.
Yield of Benzoquinone.
Yield of Benzoic Acid.
b
c
d
TON ¼ mole of product/mole of catalyst.
e
TOF ¼ mole of product/mole of catalyst ꢁ time.
Fig. 5. Product formed through benzyl alcohol oxidation by an oxidant in the presence of catalysts 1 and 2.

64
A.A. Kamilo gꢀ lu et al. / Journal of Organometallic Chemistry 828 (2017) 59e67
levels [39]. The Q band of the phthalocyanines is more intense
than Soret band. While the Q bands of the metal-free phthalocy-
anines are splitted two bands, owing to D2h symmetry and the
lifting of degeneracy of the LUMO level, as Q
metallophthalocyanines are observed as a single band owing to
4h symmetry [40]. UVeVis spectral data of phthalocyanine
x y
, Q bands that of
D
complexes (1,2) in THF, the characteristic split Q band was
exhibited with absorptions at 662 nm for compound 1 and 698 nm
for compound 2, B band absoption of phthalocyanine complexes
(
1,2) were observed at 329 nm for compound 1 and 363 nm for
compound 2, respectively (Fig. 2).
3.2. Electrochemical studies
II
II
Voltammetric analyses of Fe Pc and Co Pc were carried out in
dichloromethane (DCM)/tetrabutylammoniumperchlorate (TBAP)
electrolyte system on a Pt working electrode with (CV) and (SWV)
techniques. Voltammograms of the complexes were analyzed to
derive fundamental electrochemical parameters including the half-
wave peak potentials (E1/2), peak to peak potential separations
p
(DE ), the difference between the first oxidation and reduction
processes (
D
E
1/2). The results of voltammetric analyses are given in
Table 1.
II
Fig. 3a shows cyclic voltammogram response of Fe Pc in DCM/
2
þ
TBAP electrolyte. Metallophthalocyanines bearing Fe metal cen-
ters are rare in the literature due to the difficulty of the syntheses
and instability of these complexes [41e43]. As shown in Fig. 3a,
II
Fe Pc gives three reduction processes within the cathodic potential
II
window of DCM/TBAP. Fe Pc gives three reductions, R
1
at ꢂ0.57 V
at ꢂ1.17 V
at 0.59 V
(
(
(
D
D
D
E
E
E
p
p
p
¼ 142 mV), R
¼ 148 mV), and two oxidation reaction O
¼ 214 mV), O at 1.08 V ( ¼ 212 mV) within the potential
2
at ꢂ0.93 V (
DE
p
¼ 168 mV), R
3
1
2
D
E
p
Fig. 6. Time-dependent conversion of benzyl alcohol oxidation a) for catalyst 1, b) for
window of DCM/TBAP electrolyte system. According to the
D
E
p
ꢂ3
ꢂ3
catalyst 2. [Reaction conditions: Benzyl alcohol (2.14
ꢁ
10
mol), complex 1
II
ꢂ6
ꢂ6
values of reduction and oxidation, Fe Pc gives two reversible (R
), one quasi-reversible (R ) reduction and two irreversible
oxidation (O , O ) reactions. Electrochemical behaviors of CoPc is in
1
,
(3.56 ꢁ 10 mol), complex 2 (3.57 ꢁ 10 mol), TBHP (1.78 ꢁ 10 mol), DMF(0.01 L),
ꢀ
R
3
2
3 h and 50 C].
1
2
agreement with the similar CoPc complexes reported in the liter-
ature [44e46], which support the proposed structure of the com-
plex synthesized here. It is known that Co ion in the core of Pc ring
can behave as redox active. Redox activity of the metal of the metal
ions in the core of Pc ring depends on the energy level of empty and
occupied d orbitals of metal ions and HOMO and LUMO energy level
of Pc ring, metal ion transfers electron before the Pc ring [47]. As
phthalocyanines as a catalyst was tested in the oxidation of benzyl
alcohol. All the oxidation reactions data were given in Tables 2e5.
In experiments maintained 3 h oxidant and auxiliary chemicals on
the conversion and yields were determined. The influence of
various parameters on the percentage conversion and selectivity of
products were studied. The major product detected by GC was
benzaldehyde while benzoquinone, benzoic acid and benzyl ben-
zoate were detected by-products (Fig. 5). In the blank reactions
II
shown in Fig. 3b, CoPc gives a reduction reaction (R
1
) at ꢂ0.29 V in
DCM/TBAP electrolyte system. This process could not be assigned to
Pc based reduction reactions. Since, metallophthalocyanines
generally gives Pc based reductions after ca. ꢂ0.60 V vs. SCE [48].
Thus this reduction might be assigned to the metal based reduction
II ꢂ2
I
ꢂ2 ꢂ1
of [Co Pc ]/[Co Pc ] species. In addition to the first reduction
at ꢂ0.29 V, one Pc based reduction is also observed at ꢂ1.10 V.
During the anodic potential scans CoPc illustrate one oxidation
1 1 2
process, O at 0.74 V. Moreover, R of CoPc has reversible, R of CoPc
quasi-reversible and the oxidation process has irreversible char-
II
II
acter. As shown in Fig. S3a for Fe Pc, Fig. S3b for Co Pc, the peak
currents increased linearly with the square root of the scan rates for
ꢂ1
scan rates ranging from 25 to 500 mV s , indicating purely
diffusion-controlled behavior [49,50]. This linearity was confirmed
by the graphics of square root of scan rate versus peak current
II
II
(
Fig. 4a for Fe Pc and Fig. 4b for Co Pc). Also, in Fig. 4a and b the
1
/2
linear variation in Ip
c
versus
n
suggests a diffusion-controlled
electrode reaction which confirm the reversibility.
3
.3. Catalytic studies
Fig. 7. The oxidant effect on benzyl alcohol oxidation [Reaction conditions: Benzyl
ꢂ3
ꢂ6
ꢂ6
alcohol (2.14 ꢁ 10 mol), complex 1 (3.56 ꢁ 10 mol), complex 2 (3.57 ꢁ 10 mol),
ꢂ3
ꢀ
The effectiveness of the prepared Co(II) and Fe(II)
TBHP (1.78 ꢁ 10 mol), DMF(0.01 L), 3 h and 50 C].

A.A. Kamilo gꢀ lu et al. / Journal of Organometallic Chemistry 828 (2017) 59e67
65
ꢀ
(
(
using no catalysts or oxidants) there were no product detectable
Tables 2 and 3). It is proved that presence of the catalyst and
varing the substrat/catalyst molar ratio from 600 to 1600 at 50 C.
The results indicate that the conversion of benzyl alcohol decreased
with an increasing subs/cat ratio. Lower conversion of benzyl
alcohol with higher mass of substrate and lower mass of catalyst
was due to the fewer catalytic sites. This study shows that only 600
subs/cat ratio was needed for the reaction to reach an optimum
conversion of benzyl alcohol (95% for complex 1 and 92% for
complex 2) compared the our works in previous.
oxidant are essential for the oxidation. The conversion of benzyl
alcohol and the selectivity to benzaldehyde with Co(II) and Fe(II)
phthalocyanines at 50 C are shown in Table 2, which indicated that
the conversion of benzyl alcohol increased with the reaction pro-
cessing and reached the high conversion of 95% with complex 1
ꢀ
(Fig. 6a) and 92% with complex 2 (Fig. 6b) after reaction for 180 min,
and then remained stable with a slight increased. On the other
hand, the obvious decrease in selectivity to benzaldehyde is due to
a further oxidation of benzaldehyde to benzoic acid. Based on the
results of conversion and selectivity, 180 min was selected as the
optimal reaction time.
The amount of oxidant (TBHP) is an important factor that in-
fluences the conversion and selectivity in selective oxidation re-
actions. The influence of the substrate to oxidant molar ratios was
next examined and the results are presented in Table 3. The con-
version of benzyl alcohol decreases from 95% to 42% for complex 1
and 92%e38% for complex 2 on increasing the TBHP:benzyl alcohol
Table 2 shows the changes in the conversion of benzyl alcohol by
Table 6
Catalytic activities towards the homogeneous oxidation of benzyl alcohol of some previously reported catalyst.
ꢀ
Catalyst
Rxn time (h)
Rxn temp. ( C)
Oxidant
Conv. (%)
Ref.
CuPcb
30 min
5.5
24
70
70
50
60
TBAOX
TBHP
m-CPBA
25
26.6
31.3
43
42
45
32
47
[57]
[58]
CoPca
PdPca
c
Ru(TPP)Cl
30 min
O
2
[59]
Co(TPP)Clc
Mn(TPP)Cl
Fe(TPP)Clc
c
d
MnTEPyP
4
60
60
TBHP
[60]
[61]
NaIO
NaIO
3
16
84
4
CuTPPe
nri
O
40(in toluene)
2
35(in benzene)
Trace(in acetonitril)
f
CoPc
3
3
3
70
50
50
TBHP
TBHP
TBHP
94
89
97
94
95
92
[62]
[63]
e
FePcf
g
CoPc
FePc
CoPc
g
h
FePch
a
Pc ¼ Perfluoroalkylphthalocyanine.
Pc ¼ Un-substituted phthalocyanine.
b
c
d
e
f
(
TPP)Cl ¼ meso-tetraphenylporphyrinchloride.
TEPyP ¼ water soluble metalloporphyrins.
TPP ¼ Copper meso tetraphenylporphyrin.
Pc ¼ 2-{2-[3-(dimethylamino)phenoxy]ethoxy}ethoxy substituted phthalocyanine.
Pc ¼ 2-{2-[2,3,5,6-tetrafluorophenoxy]ethoxy}ethoxy substituted phthalocyanine.
Pc ¼ 2-(2,3,5,6-tetrafluorophenoxy)ethoxy substituted phthalocyanine.
nr ¼ not reported.
g
h
i
Scheme 1. Proposed mechanism of the formation of active species from Co(II)Pc and Fe(II)Pc and TBHP.

66
A.A. Kamilo gꢀ lu et al. / Journal of Organometallic Chemistry 828 (2017) 59e67
mole ratio from 0.83 to 3.3. Benzyl alcohol conversion reaches 95%
for complex 1 and 92% for complex 2, when the substrate to oxidant
ratio is increased to 0.83 with the highest TON and TOF values (570,
respectively. It is reasonable to assume that iron phthalocyanine
would be able to react with t-BuOOH in the same way to give
PcFe ¼ O or PcFe ¼ O according to Scheme 1 [53e56].
IV
V
190 for complex 1 and 552, 184 for complex 2) The above result
clearly points out that an increase in the TBHP content significantly
decreases the benzyl alcohol conversion [51]. The selectivity for
benzaldehyde is about 77.8% for complex 1 and 79.3% for complex
4. Conclusion
In this study, the synthesis, electrochemical and catalytic ac-
tivity properties new peripherally tetra-substituted phthalocyanine
complexes bearing fluoro-functionalized groups. All compounds
2
at this oxidant content. When still more oxidant is used, the
selectivity decreases at TBHP:BzOH mole ratio of 3.3. Therefore, a
molar ratio of TBHP/BzOH of 0.83 was used in further studies
presented below.
1
were characterized by a combination of IR, H-NMR, UVeVis and
II
II
MS spectral data. Electrochemistry of Fe Pc and Co Pc are studied
in DCM solution with voltammetric measurements. Electro-
chemical responses of the compounds support the proposed
The effect of reaction temperature was tested for both catalyst
ꢂ3
precursors, using 1.58 ꢁ 10 mol TBHP, substrate/catalyst ratio of
II
II
6
00 and 3 h reaction time in DMF system (Table 4). For complex 1,
structure of the complexes. Since Fe Pc and Co Pc gives metal
based electron transfer reactions in addition to the Pc based redox
reactions, which enrich the possible usage of the complex in
various electrochemical technologies. In conclusion 2-[2,3,5,6-tet-
rafluorophenoxy]ethoxy group substituted Co(II) and Fe(II) phtha-
locyanines are excellent biomimetic catalysts for activation of TBHP
towards oxidation of alcohols to carbonyl compounds in high
conversion and selectivity. The impressive turnover numbers ob-
tained in this catalytic system demonstrate high efficiency and also
relative stability of catalyst towards the oxidative degradation.
the activity remains almost constant around 32% (average
ꢀ
TON ¼ 759) between 25 and 50 C and markedly decrease to 48% at
ꢀ
9
0 C with 55.3% selectivity of benzaldehyde. The maximum con-
version was obtained (95%, TON ¼ 570) with the product distri-
bution of 74% benzaldehyde, 5% benzoquinone and 16% benzoic
ꢀ
ꢀ
acid at 50 C for complex 2. It appears that 50 C is the optimum
reaction temperature for the maximum yield of benzaldehyde for
both complexes.
In Table 5 different oxidants were used benzyl alcohol oxidation
with catalyst 1 and 2. H
low conversion for both complexes. Adding H
2
O
2
and m-CPBA can serve as an oxidant but
or m-CPBA in the
2
O
2
Acknowledgements
reaction media, the reaction color changed from green to brown.
This clue explains that complex 1 and 2 was degraded immediately
with H O or m-CPBA. On the other hand, the results clearly proved
2 2
This study was supported by the Research Fund of Karadeniz
Technical University, project no: 10440.
that TBHP is the best oxidant in this system for both complexes
with high conversion and benzaldehyde selectivity. Adding TBHP in
the reaction media, the reaction color changed from blue to green
and then light green. At the end of the reaction, the reaction color
turned to yellow. The reaction results in the open air, there is no
sufficient oxygen in the air for oxidation was observed. Fig. 7 was
summarized the effect of oxygen source on the reaction rate benzyl
alcohol oxidation with complex 1 and 2.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2016.11.022.
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