New Co(II) and Cu(II) Phthalocyanine Catalysts Reinforced by Long Alkyl Chains for the Degradation of Organic Pollutants

Article abstract of DOI:10.1007/s10562-017-2054-0

Abstract: The need to develop sustainable, low-cost, earth abundant catalyst is becoming paramount for overcoming environmental problems. Toward this goal, new cobalt(II) and copper(II) phthalocyanine complexes used as catalyst for degradation of organic pollutants (such as 2,3-dichlorophenol, 4-methoxyphenol, 4-nitrophenol, 2,3,6-trimethylphenol) with different oxygen source. This catalytic system with these complexes showed high conversion rates for degradation of organic pollutants and could easily be recovered by recycling reactions. Graphical Abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s10562-017-2054-0

Catal Lett
DOI 10.1007/s10562-017-2054-0
New Co(II) and Cu(II) Phthalocyanine Catalysts Reinforced
by Long Alkyl Chains for the Degradation of Organic Pollutants
Ece Tugba Saka1 · Yasemin Çağlar2
Received: 29 December 2016 / Accepted: 9 April 2017
© Springer Science+Business Media New York 2017
Abstract The need to develop sustainable, low-cost, earth
abundant catalyst is becoming paramount for overcoming
environmental problems. Toward this goal, new cobalt(II)
and copper(II) phthalocyanine complexes used as catalyst
for degradation of organic pollutants (such as 2,3-dichlo-
rophenol, 4-methoxyphenol, 4-nitrophenol, 2,3,6-trimeth-
ylphenol) with different oxygen source. This catalytic sys-
tem with these complexes showed high conversion rates
for degradation of organic pollutants and could easily be
recovered by recycling reactions.
Keywords Phthalocyanine · Cobalt · Copper · Organic
pollutants · Degradation
1 Introduction
Environmental problems are normally recounted to waste
and toxic organic with inorganic pollutants released in
water bodies. The majority of the coloured and uncoloured
effluents originated in contaminated waters contain organic
dyes and phenolic compounds from textiles, dyestuff, dye-
ing industries, fertilizers and chemical production indus-
tries [1–3]. Phenolic compounds are a major class of envi-
ronmental pollutants and are potential human carcinogens.
They are widely used in the manufacturing processes of
plastics, dyes, drugs, pesticides and papers. Their disposal
may contaminate soil and water. Because of increasing
public health concerns and stricter regulations on treatment
and disposal, it becomes more important to develop newer
and efficient methods for removing these compounds from
wastewaters [4–8] The reported methods for removing phe-
nolics from wastewaters include activated carbon adsorp-
tion [9], microbial degradation [10], chemical oxidation
[11], corona discharge [12], enzymatic degradation [13],
etc. The toxic and bio-resistant organo chlorine compounds
in aqueous systems need to be transformed into harmless
species. Various abatement techniques including biologi-
cal, thermal and chemical treatments have been developed
in the last few years for the detoxification of organic pol-
lutants [14]. Metallophthalocyanines (MPc) are very sta-
ble metal complexes of macrocyclic tetraazaporphyrin.
Thanks to their chemical and thermal stability, low cost,
easy preparation, metallophthalocyanines have found many
applications in medical and industrial areas such as gas and
chemical sensors, molecular solar cells, industrial catalytic
Graphical Abstract
Electronic supplementary material The online version of this
article (doi:10.1007/s10562-017-2054-0) contains supplementary
material, which is available to authorized users.
* Ece Tugba Saka
ece_t_saka@hotmail.com
1
Department of Chemistry, Faculty of Sciences, Karadeniz
Technical University, 61080 Trabzon, Turkey
2
Department of Bioengineering, Faculty of Engineering,
Giresun University, 28200 Giresun, Turkey
Vol.:(0123456789)
1 3

E. T. Saka, Y. Çağlar
systems, electrochromic display devices, optical switching,
nanotechnology and light-emitting devices in recent years
[15]. Due to the fact that cobalt and copper phthalocya-
nines immediately interact with oxidant and transfer oxy-
gen to substrate (such as alcohols, alkenes, thiols, phenols
etc.), they are widely used as oxidation catalysts in oxida-
tion process [16–23]. They can oxidize different phenolic
compounds to quinones and aldehydes as major product.
Selective oxidation of phenol to quinones is the key step
in the preparation of many vitamins and valuble synthetic
precursors [24].
(Ar–H), 2922, 2963, 2855 (Aliph. C–H), 2231 (C≡N),
1667–1596 (C–O), 1505, 1486, 1473, 1458, 1349, 1285,
1255, 1211, 1169, 1152, 1086, 1035, 969, 944, 907, 851,
1
839, 754, 742, 713. H-NMR. (CDCl3), (δ:ppm): 7.90 (d,
7.0, 1H, Ar–H), 7.45 (m, 7.2, 2H, Ar–H), 4.79 (d, 6.8, 2H,
CH2-O), 2.20–2.14 (t, 6.4, 2H, CH2-C), 1.48–1.33 (m, 10H,
–CH2), 0.90–0.81 (t, 6.6, 3H, –CH3). 13C-NMR. (CDCl3),
(δ:ppm): 161.88(C1), 135.22(C3), 122.70(C2), 122.38(C6),
120.43(C5), 117.30 (C7≡N), 112.54 (C8≡N), 106.46(C4),
88.64(C11), 76.81(C10), 56.96(C9), 32.10(C16), 30.04(C15),
29.85(C14), 29.12(C13), 22.90(C17), 19.08(C12), 14.83(C18).
MALDI-TOF-MS, (m/z): Calculated: 280.36; Found:
298.40 [M+H2O]+ C18H20N2O: calcd. C 77.11; H 7.19; N
9.99%; found: C 77.40; H 7.10; N 10.01.
In this paper, 2-decyn-1-oxi substituted cobalt(II) 4 and
copper(II) 5 phthalocyanine have been synthesized. Solu-
bility of phthalocyanines in water or polar solvents can
be improve by attaching sulfo [25] or quaternary ammo-
nium groups [26], crown ethers [27], long substituted alkyl
[28], alkoxy [29], alkylthio [30], macrocyclic groups [31]
peripherally or non-peripherally position on the phthalo-
cyanine ring. Thanks to the long alkyl chain substituent
groups, Co(II) and Cu(II) phthalocyanine complexes 4 and
5 can readily dissolve in some polar solvents [32]. Herein,
it has been reported that the successfull application of
Co(II) and Cu(II) phthalocyanines as oxidation catalysts for
oxidation of 2,3-dichlorophenol, 4-methoxyphenol, 4-nitro-
phenol, 2,3,6-trimethylphenol using with biphasic solvent
system. The catalyst and the oxidation products were easily
recovered and reused in the reaction media.
2.2.2 General Procedure of Metal Phthalocyanines 4–5
To give the metal phthalocyanies, the mixture of phthaloni-
trile compound 3 (0.5 g, 1.78 mmol), the related anhydrous
metal salt (CoCl2) (57.61 mg, 0.445 mmol) for compound
4, CuCl2 (59.87 mg, 0.445 mmol) for compound 5 and
two drops of DBU was heated at 160°C in dry n-pentanol
(3 mL) in a sealead tube, and stirred for 24 h. At the end
of the reaction, green product was precipitated by addition
of ethanol (20 mL) and filtered off. Along 2 h, the green
solid product was refluxed with ethanol (30 mL), filtered
off again and washed with hot ethanol, distilled water and
diethyl ether. After drying under vacuum, the product was
purified on basic alumina column with chloroform–metha-
nol (92:8) for compound 4, (95:5) for compound 5 solvent
system as eluent.
2 Experimental
2.1 Materials
2.2.2.1 Synthesis of Cobalt(II) phthalocyanine (4) Yield:
250 mg (47%). Mp>300°C. Anal.calc. for C72H80O4N8Co
FT-IR νmax/cm−1 (KBr pellet): 3076, 3009 (Ar–H), 2986,
2953, 2841 (Aliph. C–H), 1720, 1612, 1508, 1461, 1427,
1393, 1336, 1267, 1216, 1149, 1086, 1035, 994, 944, 816,
771, 741, 713. UV–Vis (CHCI3): λmax, nm (log ε): 674
(4.88), 609 (4.55), 332 (4.75). MALDI-TOF-MS, (m/z): Cal-
culated: 1179.57; Found:1181.38 [M+H]+ C72H80O4N8Co:
calcd. C 77.11; H 7.19; N 9.99%; found: C 77.56; H 7.21;
N 10.03.
The used materials, equipments and catalysis procedure
were supplied as supplementary information.
2.2 Synthesis
2.2.1 Synthesis of 4‑(dec‑2‑yn‑1‑yloxy)phthalonitrile (3)
4-Nitrophthalonitrile (2) (2.24 g, 12.94 mmol) was dis-
solved in 10 mL dry DMF under N2 atmosphere, and of
2-decyn-1-ol (1) (2.0 g, 12.94 mmol) added to mixture.
After stirring for 30 min at 60°C, finely ground anhy-
drous K2CO3 (5.357 g, 38.82 mmol) was added portion
wise within 2 h. The reaction mixture was stirred under
N2 at 60°C for 3 days. At the end of this time, the reac-
tion mixture was poured into ice-water and stirred at room
temperature for 3 h to yield a crude product. The mixture
was filtered and dried in vacuum over P2O5 for 4 h and
recystallized from ethanol to give bright brown crystal-
line powder. Yield: 2.45 g (72%). mp: 42–43°C. Anal.calc.
for C18H20N2O IR (KBr pellet), νmax/cm−1: 3086, 3046
2.2.2.2 Synthesis of Copper(II) phthalocyanine (5) Yield:
240 mg (45%). Mp>300°C. Anal.calc. for C72H80O4N8Cu
FT-IR νmax/cm−1 (KBr pellet): 3081, 3022 (Ar–H), 2974,
2943, 2840 (Aliph. C–H), 1750, 1602, 1510, 1442, 1437,
1373, 1355, 1287, 1213, 1156, 1091, 1042, 997, 939, 835,
787, 751, 726. UV–Vis (CHCI3): λmax, nm (log ε): 686
(5.02), 615 (4.38), 330 (4.68). MALDI-TOF-MS, (m/z): Cal-
culated:1184.17; Found:1185.20 [M+H]+ C72H80O4N8Cu:
calcd. C 73.03; H 6.81; N 9.46%; found: C 73.00; H6.82;
N 9.42.
1 3

New Co(II) and Cu(II) Phthalocyanine Catalysts Reinforced by Long Alkyl Chains for the…
mixtures as eluents, respectively. The structures of the
3 Results and Discussion
1
target compounds were confirmed using UV–Vis, IR, H-
NMR, 13C-NMR, mass (MALDI-TOF technique) spectro-
scopic data and elemental analysis.
3.1 Synthesis and Characterization
In the IR spectrum of compound 3, stretching vibra-
tions at 2231 cm−1 for C≡N groups, at 3086 and 3046 cm−1
for aromatic CH groups, at 2922–2855cm−1 for aliphatic
The synthetic pathways for new cobalt(II) and copper(II)
phthalocyanine compounds were outlined in Fig. 1. The
substituted phthalonitrile compound 3 was obtained by the
aromatic nucleophilic substitution reaction between 2 and
1. Cobalt(II) and Copper(II) phthalocyanines 4 and 5 were
purified by column chromatography on basic alumina using
[(CHCl3:CH3OH, 92:8) or (CHCl3:CH3OH, 95:5)] solvent
1
CH groups appeared at expected frequencies. In the H
NMR spectrum of compound 3, the aromatic protons were
obtained at 7.90 (d), 7.45 (m) ppm and aliphatic protons
were obtained at 4.79 (d), 2.20–2.14 (t), 1.48–1.33 (m),
N
O2
CN
CN
2
i
OH
1
72%
17
18
15
16
13
7
14
CN
11
9
5
6
2
12
10
O
CN
8
1
4
3
3
ii
R
R
N
Compound:
4
5
N
N
M: C o C u
Yield: 47% 45%
M
N
N
N
N
N
R
R
R=O
Fig. 1 The synthetic route of the phthalonitrile, cobalt phthalocyanine and copper phthalocyanine. Reagents and conditions: (i) dry DMF,
K2CO3, 60°C, 96 h; (ii) n-pentanol, DBU, 160°C, CoCl2, CuCl2
1 3

E. T. Saka, Y. Çağlar
0.90–0.81 (t) ppm. The 13C-NMR spectra of compound 3
indicated carbon atoms between at 161.88–14.83 ppm. The
nitrile carbon atoms for compound 3 were also observed at
117.30 and 112.54 ppm. In the mass spectum of compound
3, the presence of molecular ion peak at m/z=298.40
[M+H2O]+, confirmed the proposed structures. The results
of the elemental analysis also confirmed the structure of
compound 3. The cyclotetramerization of the phthalonitrile
compound 3 to the cobalt(II) and copper(II) phthalocya-
nine 4 and 5 can be seen clearly by the disappearance of the
peaks at 2231 cm−1 belonging to the C≡N vibrations. The
IR spectra of 4 and 5 showed similar characteristics. The
NMR spectra of peripherally tetra-substituted cobalt(II) and
copper(II) phthalocyanines 4 and 5 were not be able to take
into precluded owing to their paramagnetic nature [33]. The
mass spectra of compounds 4 and 5, which showed peaks
at m/z=1181.38 [M+H]+and 1185.20 [M+H]+respectively
support the proposed formula for these compounds. The
results of the elemental analysis also confirmed the struc-
ture of complexes 4 and 5.
Fig. 2 UV–Vis spectrum of complex 4 and 5 in chloroform
medium. All substrate, major products, catalysts within the
oxidation processes are summarized in Table 1. According
the results of this table, both catalysts showed the highest
activity producing 2,3,6-trimethyl-1,4-benzoquinone as
major product in 2,3,6-trimethylphenol oxidation reaction.
Then, optimization of the reaction conditions were
carried out by selectively evaluating effects of different
2,3,6-trimethylphenol-to-catalysts molar ratios, oxidant-to-
catalysts molar ratios, the oxidant and temperature used.
Additionally, in the blank reactions (without catalysts or
oxidants) there were no product detectable. It is proved
that presence of the catalyst and oxidant are essential for
the oxidation (Table 2). As the other parameters were kept
constant, the molar ratio was carried out in the range of
500–1500 to determine the influence of substrate to metal
ions. As we expected, the reaction rate increased with
decreasing of the substrate/catalyst molar ratio (Table 2).
Substrate/catalyst ratio on the oxidation course gave same
main product (TMBQ) with TON and TOF values (493 for
4, 389 for 5 and 164 for 4, 129 for 5).
The electronic spectra of the phthalocyanines have two
strong absorption bands in UV/Vis spectroscopy. One of
them is in the visible region at 600–700 nm (Q Band) due
to electronic transitions from π-highest occupied molecular
orbital (HOMO) to π*-lowest unoccupied molecular orbital
(LUMO) energy levels, and the other one is in the UV
region at about 300–500 nm (B or Soret Band) due to tran-
sitions from deeper π-HOMO and π*-LUMO energy levels
[34]. The Q-band of the phthalocyanines is more intense
than Soret band. While the Q bands of the metal-free phth-
alocyanines are splitted two bands, owing to D2h symme-
try and the lifting of degeneracy of the LUMO level, as
Qx, Qy bands that of metallophthalocyanines are observed
as a single band owing to D4h symmetry [35]. The Q-band
absorptions of π–π* transition for both phthalocyanines in
chloroform were observed as a single band of high intensity
at 674 nm for 4, 686 nm for 5. There was also a shoulder
at the slightly higher energy side of the Q band for each
phthalocyanine. B band absorptions of the metallophthalo-
cyanines 4–5 were observed at 330, 332 nm respectively
(Fig. 2).
To determine oxygen source effect, H2O2, m-CPBA,
TBHP and air oxygen were used as oxidant. The results in
Table 2 show that TBHP is the best oxidant for 2,3,6-tri-
methylphenoloxidation in the presence of complex 4 and
5. Moreover, H2O2 and m-CPBA can serve as an oxidant
but low conversion for both complexes. Adding H2O2 or
m-CPBA in the reaction media, the reaction color changed
from blue to brown. This clue explains that complex 4 and
5 was degraded immediately with H2O2 or m-CPBA [36].
The results of studies for complex 4 and 5 using with air
oxygen show that there is no formation of products during
the oxidation process. The another important parameter
is oxidant/catalyst ratio to find the optimal conditions of
2,3,6-trimethylphenol oxidation. When the increasing oxi-
dant/catalyst ratio from 300/1 to 800/1, the rate of the reac-
tion increased. In contrast, while the catalytic oxidation was
3.2 Catalytic Studies
The main product as 2,3,6-trimethyl-1,4-benzoquinone,
the key intermediate in the synthesis of vitamin E, the side
′
′
′
′
product as 2,2 ,3,3 ,5,5 -hexamethyl-4,4 -biphenyldiol (BP)
were determined in the oxidation of 2,3,6 trimethyphe-
nol oxidation reaction (Fig. 3). These preliminary results
exhibited that these complexes could facilitate the oxida-
tion of 2,3,6 trimethylphenol and serve as selective and
efficient catalyst. Hexane-acetonitrile (1:1) solvent mixture
is used in all oxidation reactions to form biphasic reaction
1 3

New Co(II) and Cu(II) Phthalocyanine Catalysts Reinforced by Long Alkyl Chains for the…
OH
O
Catalyst 4 and 5
Oxidant, 90 oC
HO
OH
O
2,3,6-Trimethylphenol
(TMP)
2,3,6-Trimethyl-1,4-benzoquinone
(TMBQ)
2,2',3,3',5,5'-hexamethyl-4,4'-biphenyldiol
(BP)
Fig. 3 The oxidation products of 2,3,6-trimethylphenol
Table 1 Oxidation of
Substrate
Major product
Total conver- Product
TON
TOF (h−1
)
substituted phenols catalyzed by
complex 4 and 5 using biphasic
solvent system
sion (%)
selectivity
(%)
4
5
4
5
4
5
4
5
O
99
78
95
89
493
389
164
129
OH
O
OH
OH
68
55
85
69
337
274
112
91
OH
NO2
Cl
NO2
73
45
70
30
59
97
40
50
364
225
349
149
121
74
116
49
OH
Cl
O
Cl
Cl
O
OH
O
O
OCH3
O
TON=mole of product/mole of catalyst
TOF=mole of product/mole of catalyst×time
Conversion was determined by GC
Catalyst/substrate/oxidant ratio=1/300/500, reaction time=3 h
processing from 800/1 to 1200/1, the conversion inclined to
decrasing. At this stage, it is possible that the coordination
around the cobalt and copper ion can change and produce
inactive intermediate species [37]. The results in Table 2
show that as the reaction temperature was upgraded, the
catalytic activity of complex 4 and 5 increased. When
the temperature was reduced from 90 to 25°C, the total
conversion was changed from 99 to 45% for complex 4 and
78–38% for complex 5, therefore 90°C is the optimum tem-
perature of 2,3,6-trimethylphenol oxidation with TBHP in
3 h.
Recyclability is an important and essential feature for
any catalyst to be considered in large-scale catalytic reac-
tions. As shown in Fig. 4, after completion of the oxidation
1 3

E. T. Saka, Y. Çağlar
TOF (h−1
Table 2 Selective oxidation
of 2,3,6-trimethylphenol with
catalysts 4 and 5 using different
oxidant and temperature
Subs./Ox./Cat
Oxidant
Tempera- Conversion Selectivitya TON
)
ture (°C)
(%)
4
(%)
4
5
5
4
5
4
5
500/300/1
500/500/1
800/500/1
1200/500/1
1500/500/1
500/800/1
500/1000/1
500/1200/1
500/800/1
500/800/1
500/800/1
500/800/1
500/800/1
500/800/1
300/500/free cat
300/free ox./1
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
m-CPBA
H2O2
Air oxygen
TBHP
TBHP
TBHP
TBHP
TBHP
90
90
90
90
90
90
90
90
90
90
90
75
50
25
90
90
48
68
70
75
83
99
74
49
34
67
–
36
57
62
68
71
78
52
33
21
47
–
61
58
82
77
75
95
76
68
78
88
–
58
57
66
72
69
89
66
52
60
85
–
190
339
558
897
1242
493
369
244
169
334
–
107
284
494
814
1062
389
259
164
104
234
–
63
36
94
164
271
354
129
86
55
35
78
–
113
186
299
414
164
123
81
123
111
–
146
96
74
–
–
88
58
45
–
72
47
38
7
80
59
55
–
80
56
49
–
438
289
224
–
359
234
189
–
119
78
63
–
–
–
–
–
–
–
–
TON=mole of product/mole of catalyst
TOF=mole of product/mole of catalyst × time
Conversion was determined by GC
Reaction conditions: 500/800/1: 2.04×10−3 mol/3.27×10−3 mol/ 4.09×10−6 mol and solvent mixture
(hegzane: acetonitrile) (0.01 L)
aSelectivity of TMBQ reaction time=3 h
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 blue 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 2,3,6-trimethylphenol. This
finding indicates that some unproductive decomposition
of TBHP by the catalyst and/or degradation of catalysts by
Fig. 4 Recycle experiments of compound 4 on oxidation of 2,3,6-tri-
methyphenol. Reaction conditions: 2.04×10−3 mol 2,3,6-trimethyl-
phenol, 3.27×10−3 mol TBHP, 4.09×10−6 mol compound 4 and sol-
vent mixture (hegzane:acetonitrile) (0.01 L)
TBHP occurred [36].
4 Conclusion
As a result, 4-(dec-2-yn-1-yloxy)phthalonitrile 3, Co(II)
and Cu(II) phthalocyanines 4 and 5 were successfully syn-
reaction, the catalyst can easily be separated from the reac-
tion mixture. The recovered catalyst was re-activated by
adding CH2Cl2 three times and further reused directly in
a subsequent oxidation of 2,3,6-trimethylphenol reaction.
Oxidation products of 2,3,6-trimethylphenol from the first
cycle were exracted and the reaction was going on 10 h.
GC analysis indicated less than 8% conversion of 2,3,6-tri-
methylphenol after the fourth cycle with complex 4 and
second cycle with complex 5 (Fig. 4). We observed after
each cyclic experiment, the conversion of 2,3,6-trimeth-
ylphenol decreased substantially. The fast deactivation of
1
thesized with the spectral data (UV–Vis, IR, H-NMR,
13C-NMR, MS spectroscopic data, elemental analysis).
2,3,6-trimethylphenol oxidation reactions are catalyzed by
both catalysts with high conversion and selectivity among
the all substrates. Co(II) phthalocyanine shows excellent
catalytic activity on 2,3,6-trimethylphenol oxidation with
high TON and TOF values in 3 h. The optimal conditions
are deteremined in 2,3,6-trimethylphenol oxidation with
catalyst 4 and 5. Converting from environmentally harmfull
1 3

New Co(II) and Cu(II) Phthalocyanine Catalysts Reinforced by Long Alkyl Chains for the…
16. Saka ET, Bıyıklıoğlu Z, Kantekin H, Kani İ (2013) Appl Orga-
phenolic compounds into less harmfull oxidation products
by Co(II) and Cu(II) phthalocyanines makes this study
attractive. These catalytic works are feasible, time-saving in
terms of procedure and determined the best oxidation con-
ditions with high TON and TOF values.
nomet Chem 27:59
17. Sorokin AB, Tuel A (2000) Catal Today 57:45
18. Sorokin AB, Kudrik EV (2011) Catal Today 159:37
19. Isci U, Dumoulin F, Sorokin AB, Ahsen V (2014) Turk J Chem
38:923
20. Wana Y, Lianga Q, Li Z, Xua S, Hub X, Liuc Q, Luc D (2015) J
Mol Catal A 402:29
Acknowledgements This study was supported by the Research
Fund of Karadeniz Technical University, (Project no: 5369),
Trabzon-Turkey.
21. Sen P, Kara Simsek D, Yıldız SZ (2015) Appl Organomet Chem
29:509
22. Cimen Y, Türk H (2008) Appl Catal 340:52
23. Acar I, Bayrak R, Saka ET, Bıyıklıoglu Z, Kantekin H (2013)
Polyhedron 50:345
24. Sehlotho N, Nyokong TJ (2004) J Mol Catal A-Chem 219:201
25. Sorokin AB (2013) Chem Rev 113:8152
26. Voronina AA, Kuzmin IA, Vashurin AS, Shaposhnikov GP, Puk-
hovskaya SG, Golubchikov OA (2014) Rus J Gen Chem 84:1540
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