Symmetrical and difunctional substituted cobalt phthalocyanines with benzoic acids fragments: Synthesis and catalytic activity

Article abstract of DOI:10.1142/S108842461750002X

Difunctional and symmetric phthalonitriles were synthesized by nucleophilic substitution of brome and nitro-group in 4-bromo-5-nitro-phthalonitrile for residues 4-amino-, 4-hydroxyl- and 4-sulfanyl benzoic acid. Symmetrical and difunctional substituted cobalt phthalocyanines were obtained by template synthesis based on mentioned phthalonitriles. Their spectral properties and catalytic activity in aerobic oxidation of sodium N,N-carbomoditiolate were investigated.

Full text of DOI:10.1142/S108842461750002X

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2017; 21: 37–47
DOI: 10.1142/S108842461750002X
Published at http://www.worldscinet.com/jpp/
Symmetrical and difunctional substituted cobalt
phthalocyanines with benzoic acids fragments: Synthesis
and catalytic activity
Artur Vashurin*a,c◊, Vladimir Maizlishb, Ilya Kuzmina, Serafima Znoykob,
Anastasiya Morozovab, Mikhail Razumova,c and Oscar Koifmana
a Research Institute of Macroheterocycles of Ivanovo State University of Chemistry and Technology,
Ivanovo 153000, Russia
b Department of Technology of Fine Organic Synthesis, Ivanovo State University of Chemistry and Technology,
Ivanovo 153000, Russia
c Kazan Federal University, Kazan, 420008, Russia
Received 4 July 2016
Accepted 22 October 2016
ABSTRACT: Difunctional and symmetric phthalonitriles were synthesized by nucleophilic substitution
of brome and nitro-group in 4-bromo-5-nitro-phthalonitrile for residues 4-amino-, 4-hydroxyl- and
4-sulfanyl benzoic acid. Symmetrical and difunctional substituted cobalt phthalocyanines were obtained
by template synthesis based on mentioned phthalonitriles. Their spectral properties and catalytic activity
in aerobic oxidation of sodium N,N-carbomoditiolate were investigated.
KEYWORDS: 4-bromo-5-nitro-phthalonitrile, benzoic acids, synthesis, cobalt phthalocyanines,
catalysis, oxidation.
molecules containing fragments of primary amines
INTRODUCTION
[11], immobilization on polymer surface, for example
Carbon acids of metal complexes tetrapyrrolic
silica [12] or nanotubes [13] that may be used to create
macroheterocyclic compounds have solubility in water
novel materials for purposes mentioned above. Thus,
and buffer media. This fact combined with ability to
investigations of phthalocyanine macrocycle structure
coordinatively interact with biomolecules is used in novel
expansion are actively continuing at the moment [14, 15].
methods of PDT, for example sonodynamic therapy [1]
The possibility to synthesize non-symmetrical difunc-
where joint action of sensitizer and supersonic waves is
tional phthalocyanines with specific location of substi-
used. Non-covalent interaction between biopolymers and
tuents on the periphery allows to control their physical
phthalocyanines containing hydrophobic and hydrophilic
and chemical properties and consequently significantly
groups is promising for creation of novel sensitizers for
expand the applications range.
PDT [2, 3]. Besides, catalytic activity in redox processes
There is data about carboxyl-substituted metallo-
of mercaptans and olefins of these compounds is also
phthalocyanines, in which the carboxyl-group is linked
promising [4–7].
directly with isoindole fragment and via phenoxy-,
Catalysts obtained by immobilization of metallo-
phenylamino- or phenylsulfanyl groups in literature
phthalocyanines on solid-phase carriers, carbon nano-
[16–19]. However, they are primarily concerned the
tubes, organic polymers are also perspective [8–10].
tetrasubstituted and octasubstituted phthalocyanines
Carbon residues of phthalocyanine molecule may be
containing symmetrical substituents.
used as anchoring groups for linking with biological
Meanwhile, the study of influence of the substituent
located in ortho-position towards benzoic acid fragment
electronic and structural effects on physical and chemical
◊ SPP full member in good standing
*Correspondence to: Artur Vashurin, email: asvashurin@mail.ru
properties of these phthalocyanine derivatives is beneficial.
Copyright © 2017 World Scientific Publishing Company

38
A. VASHURIN ET AL.
Introduction of the substituent may lead to cardinal
changes in the catalytic activity of the compounds.
Current work is devoted to the synthesis and study
of catalytic properties of symmetric and difunctionally
substituted derivatives of cobalt phthalocyanine contai-
ning four to eight fragments of carbon acids included in
peripheral substituents.
3195 cm-1 and deformation 1613 cm-1 vibrations of
secondary amino N–H bond are observed. Valent vibration
of Ar–O–Ar bond in range of 1245–1254 cm-1 is registered
in IR spectrum of compound 2 that is in agreement with
known data [20].
13C NMR spectra of all studied compounds have signals
of carbon atoms on 167–168 ppm, which, in accordance
with theoretically calculated spectra (Table 1) and known
literature [21], have to be attributed to the carbon atoms
of the carboxyl groups. Besides, there are signals of cyano
carbon atoms on 109–115 ppm and on 107–115 and
120–126 ppm is cyano-substituted carbon atoms.
RESULTS AND DISCUSSION
Synthesis of asymmetrical nitriles
The influence of the bridge-group nature on position
of carbon atom signal located in ortho-position towards
the benzoic acid fragment is detected. Thus, the signals of
nitro-substituted carbon atoms are situated on 120 ppm for
the compounds 2 with hydroxyl-benzoic acid fragment,
on 131 ppm for the compound 4 with amino-benzoic acid
fragment and on 134 ppm in the NMR spectrum of the
compound 3 with sulfanylphenyl-benzoic acid fragment.
The nature of bridge-group also has an effect on
the position of C9 carbon atom signal (Table 1). Thus,
the C9 atom has a shift from 145 to 159 ppm under
the transformation from the phthalonitrile contain-
ing residue of para-sulfanylbenzoic acid (3) to the
compound (2) having 4-carboxyphenoxy-group. para-
Carboxyphenylaminosubstituted phthalonitrile has an
intermediate position (150 ppm).
Nucleophilic substitution of bromine atom in 4-bromo-
5-nitrophthalonitrile (1) on benzoic acid fragment was
used to synthesize compounds (2–4) (Scheme 1).
The synthesis was carried out in DMF in presence of
anhydrous potassium carbonate under the temperature
of 25–35°C for 2 h. Reaction for 4-((4,5-dicyano-2-
nitrophenyl)amino)benzoic acid (4) was performed in
presence of triethylamine. Extraction of compounds
2 and 3 was carried out by acidification of reaction
mixture with 5% solution of hydrochloric acid. The
formed precipitate was filtered and washed with the
solution of water and HCl (0.7%). During the synthesis
the precipitate of dinitrile 4 was formed and then filtered
off. Additional precipitation of the dinitrile 4 from the
reaction mixture was done by transfer of the filtrate to
bidistilled water, wherein the nitrile precipitate was
formed and then filtered. Next the desired product
was washed with acidificated water. The yields of 2–4
compounds were 34–63%. Composition and structure of
1H NMR spectra of the compounds (2–4) have signals
of the protons of phthalonitrile fragment benzyl rings
and residue of corresponding benzoic acid in the range
of weak field (Table 1). There is no proton signal of
carboxyl-group in 1H NMR spectrum for the compounds
(3, 4) due to exchange of the proton on deuterium atom
of the solvent.
1
nitriles (2–4) were confirmed by elemental analysis, H
and 13C NMR and IR spectroscopies, mass-spectrometry.
IR spectra of all phthalonitriles have the band of cyano-
groups valent vibrations in range of 2227–2237 cm-1 [20].
IR spectra of all synthesized compounds have vibration
bands of –OH and –C=O bonds of benzoic acids carboxyl
fragments in range of 3413–3418 cm-1 and 1708–1725 cm-1
respectively.Therearebandsofsymmetrical1346–1383cm-1
andasymmetrical1523–1558cm-1 vibrationsofnitro-groups
N=O bonds for compounds (2–4). There is band of valent
vibrations of theAr–S–Ar bond on 1117 cm-1 in IR spectrum
of phthalonitrile 3. For the phthalonitrile 4 containing
para-aminobenzoic acid fragment the bands of valent
Synthesis of symmetric nitriles
The 4-bromo-5-nitrophthalonitrile (1) was used as init-
ial compound to obtain 4,4′-((4,5-dicyano-1,2-phenylene)
bis(oxy))dibenzoic acid (5), 4,4′-((4,5-dicyano-1,2-pheny-
lene)bis(sulfanediyl))dibenzoic acid (6) and 4,4′-((4,5-
dicyano-1,2-phenylene)bis(azanediyl))dibenzoic acid (7).
Reaction was performed by nucleophilic substitution of
the brome atom and nitro-group according to the
Scheme 2. Synthesis was carried out in aqueous DMF 3:5
in presence of anhydrous potassium carbonate. Reaction
was done under 100°C during 24 h for simultaneous
substitution of brome atom and nitro-group contained in 1
on benzoic acid fragment. Triethylamine was used in case
of the compound 7 containing para-aminobenzoic acid
fragment as substituent.
COOH
HX
COOH
50 °C, 2 h
X
Br
CN
CN
CN
CN
Extraction of the compounds 5 and 6 was performed
by pouring of the reaction mixture into 5% aqueous
solution of hydrochloric acid. The formed precipitate was
filtered off and washed with distilled water. The yields of
the compounds 5 and 6 were 72 and 88% respectively.
O2N
O2N
1
X = O (2); S (3); NH (4)
Scheme 1. General scheme of bifunctional nitriles synthesis
Copyright © 2017 World Scientific Publishing Company
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SYMMETRICAL AND DIFUNCTIONAL SUBSTITUTED COBALT PHTHALOCYANINES WITH BENZOIC ACIDS FRAGMENTS
39
Table 1. Chemical shift in 13C и 1H NMR spectra of bifunctional-
COOH
substituted phthalonitriles, DMSO (d6), standart TMS
HX
COOH
100 °C, 24 h
X
X
Br
CN
CN
CN
CN
O2N
1
COOH
X = O (5); S (6); NH (7)
Number
d, ppm
Scheme 2. General scheme of symmetrical nitriles synthesis
X = O (2)
X = S (3)
X = NH (4)
Calcd. Exp. Calcd. Exp. Calcd.
Exp.
intermediate that increases duration of the synthesis and
leads to additional losses during purification. Synthesis
of the compound 7 from 4-((4,5-dicyano-2-nitrophenyl)
amono)benzoic acid (4) was failed.
C1
C2
112
110
121
109
128
143
160
123
157
118
131
124
168
8.85
7.78
7.87
8.08
11.72
—
115
109
120
109
131
144
160
120
159
116
131
128
168
8.83
7.61
7.85
8.07
9.10
—
114
110
121
113
129
129
147
133
145
129
131
131
169
9.10
7.70
7.83
8.15
11.72
—
115
113
126
115
131
131
146
134
145
131
129
128
167
9.00
7.74
7.95
8.07
—
115
110
115
111
120
107
111
150
138
131
150
120
120
120
168
8.85
8.07
7.61
7.85
—
C3
120
IR spectra of all phthalonitriles have the bond of
valent vibrations in range of 2229–2237 cm-1 indicating
cyano-groups. There is dependence of the position of this
band from the nature of the bridge-group consisting of its
shift in the field of increase in wave numbers according
to the following order: 6 < 7 < 5. For bifunctional
phthalonitriles the position of the valent vibrations band
of cyano-group also depends on nature of the bridge-
group and represents in a different sequence: 2 < 3 < 4.
Besides, spectra of all synthesized compounds have
bands of valent vibrations of O–H and C=O bands of
carboxy-groups in range of 3417–3457 cm-1 and 1706–
1710 cm-1 respectively. There are no bands of N=O
vibrations in IR spectra of symmetrically substituted
phthalonitriles that indicates completed nucleophilic
substitutionofnitro-groupinthecompound1.IRspectrum
of the compound 6 shows band of valent vibrations
of Ar–S–Ar bond on 1104 cm-1. For the compound 7
containing para-aminobenzoic acid fragment bands of
valent 3195 cm-1 and deformation 1604 cm-1 vibrations of
N–H bond of the secondary amino-group are registered.
IR spectrum for the compound 5 has band of valent
vibrations of Ar–O–Ar bond on 1220 cm-1.
C4
107
C5
112
C6
150
C7
137
C8
130
C9
150
C10
C11
C12
C13
H1
H2
H3
H4
H5
–NH
124
124
122
168
9.13
8.05
7.34
7.77
10.20
10.20
—
8.83
In case of phthalonitrile 7 the reaction mixture was
poured in water, the desired product was extracted by
chloroform and then the organic layer was exposed
to liquid column chromatography on silicagel using
chloroform as eluent. The phthalonitrile 7 was dried in
vacuum under 70°C after removing of the solvent. The
yield of the desired product was 40%.
It should be noted that the compounds 5 and 6 may be
obtained by the introduction of the second fragment of
the corresponding derivative of the benzoic acid in the
molecules 2 and 3 respectively instead of nitro-groups.
Such synthesizes were done and characterized by lower
yields of the final product. Herewith, implementation
of the synthesis in two steps needs isolation of the
Synthesis of phthalocyanine cobalt complexes
Cobalt complexes of substituted phthalocyanines
were obtained by template method under heating of
corresponding phthalonitrile (2–7) with cobalt chloride
in presence of urea under the temperature of 190°C
for solidification of the reaction mixture according to
Scheme 3.
Reaction mixture was cooled after the finish of the
process, then stirred and transferred on filter, where
it was washed first with acidified water to remove the
products of interaction of urea and excess of cobalt
chloride, then with acetone. Next the precipitate was
Copyright © 2017 World Scientific Publishing Company
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40
A. VASHURIN ET AL.
HOOC
X
R
COOH
R
X
N
O
N
N
N
HOOC
X
R
CN
CN
Co
N
N
N
H N
2
NH2
CoCl2x6H2O, 190 °C
COOH
N
X
R
2-7
Co(X)Pc
R = NO2 X = O (Co(O)Pc1); S (Co(S)Pc2); NH (Co(NH)Pc3)
X
R
X
X = O (Co(O)Pc4); S (Co(S)Pc5); NH (Co(NH)Pc6)
COOH
or R =
COOH
Scheme 3. General scheme of phthalocyanines synthesis
dried. Desired compounds were extracted by DMF, the
solvent was removed. Obtained products are powders
of dark-green color, insoluble in acetone, chloroform,
partially soluble in water and well-soluble in aqueous-
alkaline solutions. Solubility in DMF of Co(X)Pc4-6 is
higher than Co(X)Pc1-3 caused by presence of additional
centers of solvation presented by four carboxyl groups.
The band of valent vibrations of cyano-groups in range
of 2225–2240 cm-1 [20] in IR spectra of synthesized
cobalt phthalocyanines is not registered. This fact
indicates absence of impurity of the starting compounds in
investigated samples. There are bands of valent vibrations
of functional groups bonds in all spectra of the synthesized
macroheterocycles, which were registered under analysis
of initial phthalonitiles (2–7) IR spectra. It suggests that
they are still contained in molecules of obtained cobalt
phthalocyanines. The shift of the C=O bonds position
under transformation from phthalonitriles to phthalo-
cyanines towards lower wave numbers is observed.
Electronic absorption spectra of Co(X)Pc in aqueous
mediums (Fig. 1) have diffuse character that is character-
istic for associated macrocycle forms. Previously [22]
we have studied tetraderivative analogues of investigated
compounds, which have no peripheral substituent in fifth
position of annulated benzene ring. It was established that
the nature of hetero-bridge affects aggregation processes
in water-alkali media. Thus, there was no association
for tetracarboxyl derivative containing amino-bridge
observed, whereas it is predominant for phthalocyanine
containing thio-bridge [22].
Figure 1. UV-vis spectra of Co(X)Pc (c 4.5 × 10-6 M) in DMF:
(1) Co(O)Pc4, (2) Co(S)Pc5, (3) Co(NH)Pc6 at 298.15 K
shift of long-wavelength absorption bands. Comparison of
UV-vis spectra of phthalocyanines combining fragments
of benzoic acids and nitro-groups have showed that the
value of bathochromic shift of Q-band under transition
from DMF to concentrated sulfuric acid depends on
the nature of bridge hetero-atom binding benzoic acid
fragment and phthalocyanine molecule. The value of
bathochromic shift of Q-band decreases in the following
order Dl Co(S)Pc2 > Co(NH)Pc3 > Co(O)Pc1.
An apparent aggregation of Co(NH)Pc3 leads
to the conclusion about redistribution of electronic
effects of substituents towards conjugated macrocycle
p-system in case of octa-substituted phthalocyanines in
contradistinction to tetra-derivatives. Intensification of
dimerization of macrocycles containing nitro-groups as
peripheral substituents is caused by electron acceptor
properties of nitro-group introduced in ortho-position
The nature of bridge heteroatom (X) has almost no
influence on the position of long-wavelength absorption
bands Co(X)Pc (Table 2).
Transition from aqueous and organic solutions to
concentratedsulfuricacidisaccompaniedbybathochromic
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SYMMETRICAL AND DIFUNCTIONAL SUBSTITUTED COBALT PHTHALOCYANINES WITH BENZOIC ACIDS FRAGMENTS
41
Table 2. Position of long-wavelength absorption bands
(lmax, nm) in UV-vis spectra of Co(X)Pc solutions at
298.15 K
Macrocycle
Solvent
DMF
675
NH4OH (5%)
651, 701
H2SO4
772
Co(O)Pc1
Co(S)Pc2
Co(NH)Pc3
Co(O)Pc4
Co(S)Pc5
Co(NH)Pc6
608, 680
609, 676
680
705
700
813
807
813
993
829
671
Figure 2. UV-vis spectra of Co(X)Pc (c 5.5 × 106 M) in NH4OH
5% aqueous solution: (1) Co(O)Pc4, (2) Co(S)Pc5 at 298.15 K
673
660; 700
651; 701
687
UV-visspectraofammoniawatersolution(5%)forCo(S)
Pc5 (Fig. 2) has splitting of Q-band and two maximums
registered, which have to be attributed to H-aggregates
(660 nm) and monomer forms of phthalocyanine (700 nm).
The monomer-associate equilibrium for Co(NH)Pc6 is
shifted towards molecular forms of macrocycle evidenced
by not broadened Q-band at 700 nm.
The position of maximums of Q-band for investigated
macrocycles in sulfuric acid is bathochromic shifted.
It is found that replacement of CoP(S)c2 nitro-groups
by one more fragment of mercaptobenzoic acid under
transformation to Co(S)Pc5 causes bathochromic shift
for 180 nm. The shift is not so big in case of compounds
having hydroxyl- and aminobenzoic acids fragments and
it is 40 and 22 nm, respectively.
relatively to the second substituent namely, the constri-
ction of the electron density from the macrocyclic system
and amplification of p–s contraction and p–p repulsion
processes. Obviously, this effect is not observed without
strong electron acceptor group in macrocycle.
Based on these considerations we can conclude that
these effects have to be aligned in phthalocyanines
containing symmetrical peripheral substituents.
The law of Lambert–Bouguer–Beer is not observed
in UV-vis spectra (Fig. 1) of Co(X)Pc4-6 solutions
that also indicates aggregation of these compounds in
solutions. The nature of bridge-heteroatom in that case
significantly affects the position of absorption long-
wavelength of the compounds (Table 2). Thus it was
found that on condition of equal concentrations of the
macrocycles in DMF solution the Q-band undergoes a
bathochromic shift in the following order: Co(S)Pc5 >
Co(O)Pc4 > Co(NH)Pc6. Aggregation degree of Co(O)
Pc4 is higher compared to other studied compounds that
is in agreement with our previous results [22] for their
tetra-derivative analogues.
Catalytic activity in oxidation
of N,N-carbomodithiolate
In our previous works [22, 23] it was established that
tetra-derivative analogues of investigated compounds
(Fig. 3) containing no substituents in ortho-position
HOOC
X
X
N
N
N
N
N
HOOC
Co
N
N
N
COOH
X
X
X = O (CoT(O)Pc); S (CoT(S)Pc); NH (CoT(NH)Pc)
COOH
Figure 3. Cobalt complexes with tetrasubstituted phthalocyanines
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42
A. VASHURIN ET AL.
 K1 →
← 
i
I
II
RS- + (CoIIPc)2
.
RS Co Pc + Co Pc
(1)
(2)
 K2 →
←
i
I
i
II
−
2
.
.
.
RS Co Pc + O2
RS Co Pc O
k
3 , slowly
i
II
-
i
III
2-
.
.
.
.
RS Co Pc O 2 + H2O → RS + H2O Co Pc O2
(3)
(4)
k4
III
2-
II
-
.
.
2H2O Co Pc O2  → 2Co Pc + H2O2 + 2OH
2RSi Instantaneous→ RSSR
(5)
Based on this mechanism the influence of the
peripheral substituent nature on catalytic activity of the
macrocycle is definitely depends on heteroatom effects
affecting metal cation of phthalocyanine molecule,
which in turn determines the stability of triple complex
and aggregation degree of macrocycles in solution.
Kinetic equation obtained using Michaelis-Menten
formal kinetic describes these systems well and it is
linearized in Lineweaver–Burke coordinates giving
Equation 6.
Figure 4. Kinetic dependences of DTC oxidation (c 2.6 ×
10-3 M) in presence of homogeneous phthalocyanine catalysts
(c 5.6 × 10-5 M) (1) Co(NH)Pc6, (2) Co(O)Pc4, (3) Co(S)Pc5 in
water-alkali solution (pH 11) at 298.15 K. The dotted line: the
result of the formal processing of the kinetic equation
towards benzoic acid fragments are catalytically active in
oxidation of sulfur compounds.
k3K1K2c(ꢀCoPc) cOꢀ
The mechanism of the process was suggested and
approved. The limiting step is formation of RS∙ radicals
according to the scheme RS• ⋅ CoIIPc ⋅ O-2 + H2O → RS• +
H2O ⋅ CoIIIPc ⋅ O22-. It was established that increase of
electron acceptor ability of spacer bridge in the substituent
on periphery of phthalocyanine leads to increase in
catalytic activity [22, 23].
As it is seen from the data of Fig. 4 the kinetic
curves of sodium N,N-carbomodithiolate (DTC)
oxidation in presence of symmetrical octa-substituted
phthalocyanines are described by formal kinetic
equation of first order in substrate. Obtained kinetic data
allowed us to calculate activation parameters for this
process (Table 3). It should be noted that the reaction
rate increases up to 80 times compared to non-catalytic
oxidation [24].
2
2
.
(6)
r =
cRS-
1+ K1cRS-
It should be noted that introduction of four additional
benzoic acid fragments leads to intensification of specific
solvation of the macrocycle on periphery. Besides,
ionization of the macromolecule is strengthened. It
leads to decrease of process rate because of competing
interaction of the substrate and solvent with active
centers of the catalyst. DTC oxidation rate constant
decreases in the folloing order of catalysts Co(NH)Pc6
> Co(S)Pc5 ≥ Co(O)Pc4. The order is different from
tetra-substituted one CoT(S)Pc > CoT(NH)Pc > CoT(O)
Pc that is probably caused by difference in macrocycle
association degree. Thus, CoT(NH)Pc in solution is
monomeric and all its reaction centers are permanently
occupied by solvent [22]. Whereas, there is possibility to
compete for active center in associate Co(NH)Pc6.
Analysis of obtained results and literature data [25–27]
suggests that for Co(X)Pc4-6 the mechanism including
triple complex formation with followed elimination
of RS∙ radical from it is realized. The mechanism is
presented by Equations 1–5.
The catalyst forms intermediate in solutions of high
ionization degree of the macrocycle and high containing
of OH-. The intermediate has oxidized thiocarbamic acid
Table 3. Kinetic dependences of DTC oxidation (c 2.6 × 10-3 M) in presence of Co(X)Pc
phthalocyanine catalysts (c 5.6 × 10-5 M) in water-alkali solution (pH 11)
Catalyst
kw298 × 102, L.(mol.s)-1
E≠, kJ.mol-1
DS≠ J.(mol.K)-1
-lnA
c
Co(O)Pc1
Co(S)Pc2
Co(NH)Pc3
Co(O)Pc4
Co(S)Pc5
Co(NH)Pc6
7.01
26.91
9.57
-22.09
-12.82
-22.95
10.1
-378
-339
-375
-281
-236
-245
8.7
7.3
8.5
9.1
9.2
7.7
69.05
89.42
67.43
57.71
68.02
53.86
3.82
4.58
22.4
17.56
12.1
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SYMMETRICAL AND DIFUNCTIONAL SUBSTITUTED COBALT PHTHALOCYANINES WITH BENZOIC ACIDS FRAGMENTS
43
in outer coordination sphere forming hydrogen bond
with coordinated oxygen molecule. Then there is transfer
of the charge from the metal to oxygen. Increase of pH
leads to competing of DTC coordination processes and
dimerization due to intensification of last one. This
complicates the electron transfer. That is why the authors
Wherein, the concentration of associated macrocycle
forms participated in reaction (1) decreases under
temperature increase. Decrease of dimer concentration
is faster than increase of reaction (3) rate constant that
leads to decrease of the total rate of the process. The
total process rate changes in order CoT(S)Pc > CoT(NH)
Pc > CoT(O)Pc, which correlates to the series of tetra-
substituted CoT(X)Pc.
[28] suggested that electron transfer is implemented in
-
reaction of CoPcII OH complex with other hydroxyl-ion
…
(CoPcII OH )2 + OH → CoPc CoPc OH + O + H2O.
CoPcI + O2 → CoPcII + O2-, CoPcII + O2 → CoPcIII + O2-.
There is permanent formation of O2– and CoPcIII oxidized
forms under excess of oxygen in water-alkali system that
complicates the triple complex formation on condition
of high content of hydroxyl ions in the solution and
consequently reduces the activity of the phthalocyanine as
a catalyst. It is also a characteristic of investigated by us
systems.
-
-
I
II
…
-
-
…
…
EXPERIMENTAL
Equipment
Elemental analysis has been carried out by means
of chromatographic analyzer Flash HCNS-OEA 1112
(Germany). The flowrates of helium and oxygen were
140mL/minand250mL/min,respectively;thetemperature
of the reactor was 1173 K, oxygen was supplied into the
reactor for 250 mL/min with 12 s time delay.
FT-IR spectra were recorded using IR-Fourier
spectrophotometer Avatar 360 (USA) in 400–4000 cm-1
frequency range.
NMR spectra of the solutions were recorded by means
of NMR spectrometer Bruker AVANCE-500 (Germany)
at operating frequency 500 MHz (1H) and 100 MHz
(13C). Measurements were performed under the Fourier
transformation conditions in 5 mm cells at various
temperatures. Chemical shifts were measured with
reference to the internal standard — tetramethylsilane
(TMS). The accuracy of measurements was 0.005 ppm.
Electron absorption spectra (UV-vis) were registered
by means of Unico 2800 (USA) spectrophotometer in a
spectral range of 200–1000 nm. Quarts optical cell were
used for the measurements. UV-vis spectra were recorded
at 298.15 0.03 K.
Absolutely unexpected results are obtained for Co(X)
Pc1-3. There is inhibition of the oxidation under increase
of the temperature while maintaining the formal first-
order kinetic reaction on the substrate. The calculation
of the activation parameters of the system showed
negative energies of activation process (Table 3).These
data characterizes the process as complex. Obviously,
the rate constant of the process (3), which is limiting
stage, is increased under increase of temperature. But
the presence of strong acceptor groups (NO2) contained
in the macrocycle in para-position towards benzoic acid
fragments leads to contraction of p-electronic density
from central metal cation and decrease of partially
positive charge compensation [29]. Macrocycle-solvent
coordination interaction compensates this charge.
Increase of activation entropy change indicates the
desolvation of activated complex (Fig. 5) and introducing
of substrate or oxygen into coordination sphere,
which characterizes the transfer towards association-
dissociation mechanism of the process.
Mass spectra were measured on an Axima MALDI-
TOF mass-spectrometer (Shimadzu, Japan).
pH values of the solutions were controlled with pH
meterS220SevenCompact(MettlerToledo,Switzerland).
Relative error of pH determining was 0.002.
Obviously, there is an exchange between DTC and
coordinated by phthalocyanine ligand (Fig. 5) which can
be presented by solvent or molecular oxygen [30]. The
exchange depends essentially on electron-donor power of
second ligand, for ions — on their basicity.
Synthesis of bifunctional nitriles
4-bromo-5-nitrophthalonitrile (1) was synthesized
according to the method recommended in [31]. Physical
and chemical properties of the obtained compound are in
good agreement with literature data. mp 140–142°C (%).
Elemental analysis found C, 38.10; N, 16.50; H, 0.68%.
Anal. calcd. for (C8H2BrN3O2) C, 38.16; N, 16.67; H,
0.80. IR (KBr): n, cm-1 2241 (C≡N), 1560 (NO2), 1341
(NO2), 813 (C–Br).
R
X
R
N
O
O
C
S
HS
General method. 2.52 g (0.01 mol) 4-bromo-5-
nitrophthalonitrile (1) and 0.01 mol of corresponding
benzoic acid were dissolved in 50 mL of DMF and
placed into two-necked flask equipped with a reflux. The
where X = solvent or molecular oxygen
Figure 5. Exchange of ligands
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 43–47

44
A. VASHURIN ET AL.
solution of 1.38 g (0.01 mol) of anhydrous potassium
carbonate in 7 mL of water was added to the mixture. The
reaction mixture was stirred at 25°C for 1 h. Obtained
precipitate was filtered off and washed with 5% aqueous
solution of hydrochloric acid until the colorless filtrate.
Then it was dried on air under 70–80°C. Extraction was
performed by acidification of the reaction mixture by 5%
solution of hydrochloric acid. The precipitate was filtered
and washed with acidified water.
4-(4,5-Dicyano-2-nitrophenoxy)benzoic acid (2).
It was synthesized from 1.38 g of para-hydroxybenzoic
acid. The yield is 1.76 g (57%). Elemental analysis
found C, 59.02; H, 2.32; N, 13.30%. Anal. calcd. for
(C15H7N3O5) C, 58.26; H, 2.28; N, 13.59. IR (KBr):
n, cm-1 3014 (OH), 2231 (C≡N), 1719 (C=O), 1558
(NO2), 1380 (NO2), 1254 (Ar–O–Ar). MS (MALDI-
TOF): m/z 309.29 [M], calcd. [M] 309.24.
(C≡N); 1708 (C=O); 1220 (Ar–O–Ar). MS (MALDI-
TOF): m/z 399.30 [M–H]-; calcd. [M] 400.07.
4,4′-((4,5-Dicyano-1,2-phenylene)bis(sulfanediyl))
dibenzoic acid (6). It was synthesized from 3.08 g
of para-mercaptobenzoic acid. Yield 3.80 g (88%).
Elemental analysis found C, 60.95; H, 2.93; N, 6.15; S,
14.35%. Anal. calcd. for (C22H12N2O4S2) C, 61.10; H,
1
2.80; N, 6.48; S, 14.83. H NMR (DMSO-d6): d, ppm
10.55 s (COOH, 2H), 7.88 s (H1, 2H), 7.57–7.60 d (H2,
4H; J 2.05 Hz), 7.96–8.02 d (H3, 4H; J 2.04 Hz). IR
(KBr): n, cm-1 3417 (OH); 2229 (C≡N); 1710 (C=O);
1104 (Ar–S–Ar). MS (MALDI-TOF): m/z 431.28
[M–H]-; calcd. [M] 432.02.
4,4′-((4,5-Dicyano-1,2-phenylene)bis(azanediyl))
dibenzoic acid (7). It was synthesized from 2.74 g of
para-aminobenzoic in presence of 2 mL of triethylamine.
After finish of the synthesis the desired compound was
extracted by pouring of the reaction mixture onto water
and then adding chloroform. Next the chloroform was
separated from water part on separating funnel, after this
the solvent was removed. The compound was column
chromatographed on silica using chloroform as eluent.
Yield 1.59 g (40%). Elemental analysis found C, 65.20;
H, 3.33; N, 14.10%. Anal. calcd. for (C22H14N4O4) C,
4-((4,5-Dicyano-2-nitrophenyl)thio)benzoic
acid (3). It was synthesized from 1.54 g of para-
phenylsulfanylbenzoic acid. Yield 1.12
g (34%).
Elemental analysis found C, 55.25; H, 2.02; N, 13.00%.
Anal. calcd. for (C15H7N3O4S) C, 55.38; H, 2.17; N,
12.92. IR (KBr): n, cm-1 3417 (OH), 2232 (C≡N), 1725
(C=O), 1550 (NO2), 1383 (NO2), 1117 (Ar–S–Ar). MS
(MALDI-TOF): m/z 324.71 [M–H]-, calcd. [M] 325.65.
4-((4,5-Dicyano-2-nitrophenyl)amino)benzoic acid
(4). It was synthesized from 1.37 r para-aminobenzoic
acid in presence of 2 mL of triethylamine. Yield 1.96 g
(63%). Elemental analysis found C, 58.20; H, 3.00; N,
18.10%. Anal. calcd. for (C15H7N4O4) C, 58.45; H, 2.62;
N, 18.18. IR (KBr): n , cm-1 3418 (OH), 3195 (NH),
2237 (C≡N), 1708 (C=O), 1613 (NH), 1523 (NO2), 1406
(NH), 1346 (NO2). MS (MALDI-TOF): m/z 332.01 [M +
Na]+, calcd. [M] 308.25.
1
66.33; H, 3.54; N, 14.06. H NMR (DMSO-d6): d, ppm
8.58 s (COOH, 2H), 8.51 s (NH, 2H), 8.01 s (H1, 2H),
7.52–7.53 d (H2, 1H; J 2.05 Hz), 7.62–7.63 d (H3, 2H;
J 2.01 Hz). IR (KBr): n, cm-1 3418 (OH), 3195 (NH),
2234 (C≡N), 1706 (C=O), 1604 (NH), 1434 (NH). MS
(MALDI-TOF): m/z 399.34 [M + H]+; calcd. [M] 398.38.
General methods. II variant. 0.1 mmol of nitrile
(2–3) and 0.1 mmol of corresponding benzoic acid
were dissolved in 5 mL of DMF and placed into two-
necked flask equipped with reflux. The solution of 0.14 g
(0.1 mmol) of anhydrous potassium carbonate in 0.7 mL
of water was added to the mixture. It was stirred under
80–90°C for 24 h. The precipitate obtained was filtered
off and washed with aqueous solution of hydrochloric
acid (5%) until colorless filtrate. Then it was dried on air
under 70–80°C.
Synthesis of symmetrical nitriles
General methods. I variant. 2.52 g (0.01 mol)
of 4-bromo-5-nitrophthalonitrile (1) and 0.02 mol of
corresponding benzoic acid were dissolved in 50 mL of
DMF and placed into two-necked flask equipped with
reflux. The solution of 5.52 g (0.04 mol) of anhydrous
potassium carbonate in 7 mL of water was added to the
mixture. The reaction mixture was stirred under 100°C
for 24 h, then poured onto acidic water and desired
product was collected from the filter. The precipitate
obtained was filtered of and washed with 5% aqueous
solution of hydrochloric acid until colorless filtrate.
4,4′-((4,5-Dicyano-1,2-phenylene)bis(oxy))
dibenzoic acid (5). It was synthesized from 2.76 g
of para-hydroxybenzoic acid. Yield 2.88 g (72%).
Elemental analysis found C, 64.59; H, 3.12; N, 6.83%.
Anal. calcd. for (C22H12N2O6) C, 66.00; H, 3.02; N, 7.00.
1H NMR (DMSO-d6): d, ppm 10.58 s (COOH, 2H), 7.66 s
(H1, 2H), 6.96–7.06 d (H2, 4H, J 2.01 Hz), 8.03–8.12 d
(H3, 4H, J 2.05 Hz). IR (KBr): n, cm-1 3457 (OH); 2237
The compound (7) was not obtained by this method.
4,4′-((4,5-Dicyano-1,2-phenylene)bis(oxy))
dibenzoic acid (5). It was synthesized from 0.31 g of
4-(4,5-dicyano-2-nitrophenoxy)benzoic acid (2) and
0.14 g of para-hydroxybenzoic acid. Yield 0.21 g (52%).
Elemental analysis found C, 64.63; H, 3.14; N, 6.67%.
Anal. calcd. for (C22H12N2O6) C, 65.70; H, 3.02; N, 7.00.
IR (KBr): n, cm-1 3454 (OH); 2237 (C≡N); 1708 (C=O);
1220 (Ar–O–Ar).
4,4′-((4,5-Dicyano-1,2-phenylene)bis(sulfanediyl))
dibenzoic acid (6). It was synthesized from 0.33 g
4-((4,5-dicyano-2-nitrophenyl)thio)benzoic acid (3) and
0.15 g para-mercaptobenzoic acid. Yield 0.27 g (62%).
Elemental analysis found C, 60.90; H, 2.90; N, 6.24; S,
14.52%. Anal. calcd. for (C22H12N2O4S2) C, 61.10; H,
2.80; N, 6.48; S 14.83. IR (KBr): n, cm-1 3417 (OH);
2229 (C≡N); 1710 (C=O); 1104 (Ar–S–Ar).
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SYMMETRICAL AND DIFUNCTIONAL SUBSTITUTED COBALT PHTHALOCYANINES WITH BENZOIC ACIDS FRAGMENTS
45
Synthesis of cobalt complex of phthalocyanines
Cobalt octa-4,5-(4′-carboxyphenoxy)phthalocyani-
nate (Co(O)Pc4). It was synthesized from 120 mg of
phthalonitrile 5. Yield 82 mg (60%). Elemental analysis
found C, 63.10; H, 3.04; N, 6.55%. Anal. calcd. for
(C88H48N8O24Co) C, 63.66; H, 2.91; N. 6.75. IR (KBr):
n, cm-1 3443 (OH); 1712 (C=O); 1224 (Ar–O–Ar). MS
(MALDI-TOF): m/z 1676.17 [M + H2O – H]+; calcd. [M]
1659.31.
Cobalt octa-4,5-(4′-carboxyphenylsulfanyl)phtha-
locyaninate (Co(O)Pc5). It was synthesized from 130 mg
of phthalonitrile 6. Yield 95 mg (64%). Elemental
analysis found C, 59.17; H, 2.82; N, 6.10%. Anal. calcd.
for (C88H48N8O16S8Co) C, 59.09; H, 2.70; N, 6.26. IR
(KBr): n, cm-1 3447 (OH), 1711 (C=O), 1104 (Ar–S–
Ar). MS (MALDI-TOF): m/z 1789.78 [M + 2H]+; calcd.
[M] 1787.03.
Cobalt octa-4,5-(4′-carboxyphenylamino)phthalo-
cyaninate (Co(O)Pc6). It was synthesized from 120 mg
of phthalonitrile 7.Yield 50 mg (37%). Elemental analysis
found C, 63.70; H, 3.55; N, 13.18%. Anal. calcd. for
(C88H56N16O16Co)C, 63.96; H, 3.42; N, 13.56. IR (KBr):
n, cm-1 3413 (OH); 3172 (NH); 1703 (C=O); 1602 (NH);
1434 (NH). MS (MALDI-TOF): m/z 1652.36 [M + H]+;
calcd. [M] 1651.34.
General method. Carefully stirred mixture of 0.33
mmol of corresponding substituted phthalonitrile, 54 mg
(0.20 mmol) of cobalt chloride hexahydrate and 60 mg
(1 mmol) of urea was held under the temperature of 190–
195°C until solidifying of the reaction mixture. Next, it
was stirred, washed with acidic water and acetone, then
dried on air under 70–80°C.
Cobalt tetra-4-nitro-tetra-5-(4-carboxyphenoxy)
phthalocyaninate (Co(O)Pc1). It was synthesized from
101 mg of phthalonitrile 2.Yield 62 mg (58%). Elemental
analysis found C, 55.10; H, 2.54; N, 13.15%. Anal. calcd.
for (C60H28N12O20Co) C, 55.61; H, 2.18; N, 12.97. IR
(KBr): n , cm-1 3463 (OH), 1722 (C=O), 1509 (NO2),
1384 (NO2), 1263 (Ar–O–Ar). MS (MALDI-TOF): m/z
1294.90 [M]-, calcd. [M] 1295.09.
Cobalt tetra-4-nitro-tetra-5-(4-carboxyphenoxyul-
phanyl)phthalocyaninate (Co(S)Pc2). It was synthe-
sized from 108 mg of phthalonitrile 3. Yield 67 mg
(60%). Elemental analysis found C, 53.17; H, 2.20; N,
12.00%. Anal. calcd. for (C60H28N12O16S4Co) C, 52.98;
H, 2.07; N, 12.36. IR (KBr): n, cm-1 3440 (OH), 1719
(C=O), 1589 (NO2), 1404 (NO2) 1194 (Ar–S–Ar), 1050
(N=N), 744 (C–N). MS (MALDI-TOF): m/z 1382.18
[M + Na], calcd. M 1359.01.
Cobalt tetra-4-nitro-tetra-5-(4-carboxyphenyla
mino)phthalocyaninate (Co(NH)Pc3). It was synthe-
sized from 101 mg of phthalonitrile 4.Yield 51 mg (48%).
Elemental analysis found C, 56.00; H, 2.38; N, 18.00%.
Anal. calcd. for (C60H32N16O16Co) C, 55.78; H, 2.50; N,
17.35. IR (KBr): n, cm-1 3432 (OH), 3192 (NH), 1703
(C=O), 1379 (NO2). MS (MALDI-TOF): m/z 1326.36
[M + 2H2O – H]-, calcd. [M] 1291.15.
Studies of catalytic activity
The catalytic activity of metallophthalocyanines was
tested with a known [32, 33] reaction of sodium N,N-
diethylcarbamodithioate (DTC) oxidation. It proceeds
according to general scheme:
Advantages of this reaction are low toxicity of initial
materials and possibility of monitoring of concentration
C2H5
C2H5
S
C2H5
C2H5
S
S
S
S
C2H5
C2H5
cat
+ 2 NaOH
2
N C
+ 1/2 O2 + H2O
SNa
N C
C N
Scheme 4. Oxidation of DTC
of initial and desired materials and identification of
reaction products using electron absorption (UV-vis
spectra) and FT-IR spectroscopy methods. Experiments
to study the kinetics of DTC oxidation were carried out
in thermostatic cell in which the solution of DTC of
650 mL was loaded.
The air needed for oxidation was fed via micro
compressor with constant rate of 2 L.min-1. The reaction
takes place in kinetic region under these parameters [23].
After establishing a constant temperature of reaction
mixture, it was stirred and sample of 2 mL was taken to
determine initial concentration of DTC, then compressor
was turned on. This moment was taken as the beginning
of the reaction. Samples of 2 mL were taken periodically
during the experiment to determine current concentration
of DTC. The concentration of DTC was monitored by
spectrophotometric method.
Under conditions of constant concentrations of oxygen
and catalyst, constant pH of solution the rate of DTC
oxidation is described by first order kinetic equation:
∂c
∂t
= -kobscDTC
(7)
where kobs — observed constant of the rate, s-1.
It is confirmed by straightness of graphics in
coordinates lnc — t and constancy of rate constants
calculated according to the equation:
ln c
0
c
(8)
kobs
=
t
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 45–47

46
A. VASHURIN ET AL.
where C0 — initial concentration of DTC, c — current (t)
concentration of DTC.
The rate constants of (n + 1)-order were calculated
using Equation 9.
of peripheral substituents affects rate and mechanism
of the oxidation significantly. Introduction of electron
acceptor groups in periphery of the phthalocyanine
molecule leads to increase of catalytic activity.
kobs
cDi TC
kw298
=
Acknowledgements
(9)
The work was supported by Russian Science
Foundation project 14-23-00204 and partially supported
by Russian President’s grant for young scientists — PhD
(MK-2776.2015.3).
The activation energy (E≠) for the studied temperature
range was calculated by the Arrhenius equation in the
integrated form:




T T2
k2
k1
REFERENCES
E≠ = 19.1
lg
(10)
1

T -T
1 
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E≠
∆S≠ = 19.1ln kw298
+
− 253
(11)
298
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(12)
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