Synthesis and antimicrobial activity of new phthalocyanine complexes and electrochemical and spectroelectrochemical behaviour of cobaltphthalocyanine

Article abstract of DOI:10.3184/174751912X13491019351916

A novel phthalocyanine bearing oxygen donor atoms on the peripheral positions has been synthesised by cyclotetramerisation of (E)-4-(4- cinnamoylphenoxy) phthalonitrile and its nickel, zinc, cobalt, copper and lead derivatives prepared. The thermal stabilities of the phthalocyanine compounds have been determined and their possible biological activities (antibacterial, anticandidal and antifungal) studied. The effects of substituent on the electrochemical and in situ spectroelectrochemical behaviour of cobaltphthalocyanine have been investigated and an in situ electrocolorimetric method was applied to investigate the colour of the electrogenerated anionic and cationic forms of the complex.

Full text of DOI:10.3184/174751912X13491019351916

JOURNAL OF CHEMICAL RESEARCH 2012
RESEARCH PAPER 665
NOVEMBER, 665–671
Synthesis and antimicrobial activity of new phthalocyanine complexes
and electrochemical and spectroelectrochemical behaviour of
cobaltphthalocyanine
Elif Çelenk Kayaa*, Hülya Karadenizb, Atıf Kocac, Nuran Kahrimand and Atalay Sökmene
aGümüs¸hane Vocational School, Gümüs¸hane University, 29100 Gümüs¸hane, Turkey
bCouncil of Forensic Medicine, 61080Trabzon, Turkey
cDepartment of Chemical Engineering, Faculty of Engineering, Marmara University, 34722, Istanbul, Turkey
dDepartment of Chemistry, Faculty of Sciences, KaradenizTechnical University, 61080Trabzon, Turkey
eDepartment of Biology, Faculty of Sciences, KaradenizTechnical University, 61080Trabzon, Turkey
A novel phthalocyanine bearing oxygen donor atoms on the peripheral positions has been synthesised by cyclo-
tetramerisation of (E)-4-(4-cinnamoylphenoxy) phthalonitrile and its nickel, zinc, cobalt, copper and lead derivatives
prepared. The thermal stabilities of the phthalocyanine compounds have been determined and their possible bio-
logical activities (antibacterial, anticandidal and antifungal) studied. The effects of substituent on the electrochemical
and in situ spectroelectrochemical behaviour of cobaltphthalocyanine have been investigated and an in situ electro-
colorimetric method was applied to investigate the colour of the electrogenerated anionic and cationic forms of the
complex.
Keywords: phthalocyanine, metal complexes, antimicrobial activity, spectroelectrochemistry, chromaticity diagram.
For many years, phthalocyanine (Pc) compounds have been
widely used as organic pigments and dyestuffs. Besides their
application in such traditional areas, phthalocyanines (Pcs)
have been extensively studied due to their spectroscopic
electrochemical, electrical and photoelectric properties. The
solubility of Pcs is very important for the investigation of their
chemical and physical characteristics and can be increased by
introducing different kinds of solubility-enhancing substitu-
ents such as alkyl, alkoxy, phenoxy and macrocyclic groups at
the peripheral and axial position of the Pc ring.1–3 Metalloph-
thalocyanines can be obtained by the classial template reactions
of diverse precursors such as phthalonitrile, cyano-benzamide,
phthalamide and phthalic acid with metal salts in high-boiling
nonaqueous solvents at elevated temperatures.4,5 Pcs are gener-
ally blue-green in colour due to the π→π* bands associated
with the planar heteroaromatic π- conjugation system. Pcs and
their metal complexes have been widely used as dyes and pig-
ments. In particular, they have drawn much attention in recent
years by their functional properties and potential application to
chemical sensors, electrophotography, photovoltaics, optical
discs, solar cells, photodynamic therapy, catalysis, etc.6–12 Pcs
and their analogues (e.g. naphthalocyanines) show great poten-
tial as phototherapeutic agents for the treatment of a variety of
oncological and non-oncological diseases.13,14 Previous inves-
tigations showed that some Zn(II)-phthalocyanines (ZnPcs)
can efficiently photosensitise the inactivation of various mic-
robial pathogens.15–17 The importance of this class of com-
pounds as antimicrobial photosensitisers was further enhanced
by the observation that the presence of positively charged
functional groups allows an extensive photoinduced killing of
Gram-negative bacterial cells, 18 which are usually resistant to
the action of non-cationic porphyrinoid photosensitisers.19 In
recent years, growing interest has focused on the application
of microwave irradiation in organic synthesis. Microwave
processing has attracted potential interest as an alternative to
classical thermal processing because of the inherent advanta-
ges of microwave heating, which is selective, direct, rapid,
internal and controllable.20–24 The use of microwave irradiation
for synthesis of phthalocyanines reduces reaction time and
enhances yield in comparison with classical methods.25,26
We now describe the synthesis and characterisation of metal-
free- and metallo-phthalocyanines bearing oxygen donor
atoms on the peripheral positions. In addition, we investigated
the antimicrobial activities of these novel metallophthalocya-
nine complexes. Furthermore, we report the voltammetric,
in situ spectroelectrochemical, and in situ electrocolorimetric
responses of newly synthesised CoPc 7.
Results and discussion
Synthesis and characterisations
The general route for the synthesis of the new phthalocyanines
is shown in Fig. 1. As the first step, (E)-1-(4-hydroxyphenyl)-3-
phenylprop-2-en-1-one was used to prepare (E)-4-(4-cinnamoyl-
phenoxy) phthalonitrile through base-catalysed, nucleophilic
aromatic nitro displacement of 4-nitrophthalonitrile. The reac-
tion was catalysed by K2CO3 in dimethylformamide (DMF).
The IR spectrum of 3 clearly indicates the presence of C≡N
groups by the intense stretching band at 2232 cm−1. In the 1H
NMR spectrum of 3 in deuterated chloroform, the aromatic
protons and olefinic protons appear as a multiplet at 8.16–
7.17 ppm. The 13C NMR spectrum of 3 indicated the presence
of nitrile carbon atoms in 3 at 115.44, 115.01 (C≡N) ppm. The
mass spectrum of this compound at (m/z): 350 [M]+ supports
the proposed formula for this compound and elemental
analysis confirms the desired compound 3.
Starting from the dicyano derivatives, many chemical routes
may be used to form the corresponding metal-free phthalocya-
nines. Metal-free phthalocyanine 4 was synthesised from the
corresponding dicyano compound 3 in dry n-pentanol under
dinitrogen in the presence of 1, 8-diazabicyclo[5.4.0]undec-7-
ene (DBU). The IR spectrum of metal-free phthalocyanine 4
shows (NH) vibrations at 3430 cm−1. The disappearance of the
C≡N stretching vibration in the IR spectrum of 3 indicates the
formation of compound 4. In the 1H NMR spectra of this com-
pound, the inner core protons of Pc-2H could not be observed
due to strong aggregation of molecules.27 The mass spectrum
of this compound at (m/z): 1403 [M]+ supports the proposed
formula for this compound and elemental analysis confirms
the desired compound 4.
The metallophthalocyanines 5, 6, 7, 8 and 9 were obtained
from dicyano derivative 3 and corresponding anhydrous metal
salts NiCl2, Zn(CH3COO)2, CoCl2, CuCl2 and PbCl2 respec-
tively, by microwave irradiation in 2-(dimethyl-amino)ethanol
at 175 °C, 350 W.
* Correspondent. E-mail: elifcelenk1629@hotmail.com

666 JOURNAL OF CHEMICAL RESEARCH 2012
Fig. 2 UV-Vis spectra of H2Pc (▬▬), NiPc (▬▬) and ZnPc
(▬▬) complexes.
Compound
M
4
5
6
7
8
9
2H
Ni (II)
Zn(II)
Co(II) Cu(II) Pb(II)
Fig. 1 The synthesis of the metal-free phthalocyanine and
metallophthalocyanines.
Fig. 3 UV-Vis spectra of CoPc (▬▬), CuPc (▬▬) and PbPc
(▬▬) complexes.
In the IR spectra of metallophthalocyanines 5, 6, 7, 8 and 9
the disappearance of the strong C≡N stretching vibration of 3
was evidence for the IR spectra of metallophthalocyanines,
and the IR spectra of 5, 6, 7, 8 and 9 are very similar to those
of the metal-free phthalocyanine 4. The NMR characteristics
of these compounds were similar to those of the precursor
dicyano compound 3 and the metal-free phthalocyanine 4. In
the mass spectrum of Ni, Zn, Co, Cu and Pb phtahlocyanines,
the presence of molecular ion peaks at (m/z): 1460 [M]+, 1467
[M+1]+, 1460 [M]+, 1465 [M]+, 1608 [M]+ respectively, and
their elemental analyses, confirm the proposed structures of 5,
6, 7, 8 and 9.
the split form in their metal-free derivatives are their basic
characteristic.34
The thermal behaviour of the metallophthalocyanines were
investigated by TG/DTA. Although the thermal stabilities of
phthalocyanines are well known, the phthalocyanine com-
pounds are not stable above 364.9 °C. The initial and main
decomposition temperatures are given in Table 1. The initial
decomposition temperature decreased in the order: 8 > 6 > 7>
9 > 5 > 4.
Phthalocyanines 4–9 show typical electronic spectra with
Antimicrobial activity
two different strong absorption regions. The first, in the UV
region at around 340 nm and called the Soret (or B) band,
The antimicrobial activities of metallophthalocyanines 5, 6, 7,
8 and 9 were assayed against the microorganisms considered
in the present study and were qualitatively and quantitatively
assessed, evaluating the presence of inhibition zones, zone
diameter, and MIC values. As shown in Table 2 Acinetobacter
haemolyticus bacterium and Enterobacter cloacea are sensi-
tive to all the complexes. The maximal inhibition zones and
MIC values for microorganisms, which were sensitive to 5, 6,
28
arising from the deeper π levels→LUMO transition between
an a2u and the same eg orbitals and extending to the blue of the
visible spectrum, is generally much less intense. The second,
in the visible region at 600–700 nm and called the Q band, is
attributed to the π–π* transition from the HOMO to the LUMO
of the Pc2− ring.29,30 The electronic absorption spectrum of the
metal-free Pc 4 in chloroform at room temperature is shown
in Fig. 2. The split Q bands in 4, which are characteristic of
metal-free phthalocyanines, were observed at λmax 698(2.58)
and 660(2.50) nm. These Q band absorptions indicate a mono-
meric species with D2h symmetry due to the phthalocyanine
ring being involved in a fully conjugated 18 π electron
system.31−33 Phthalocyanine 4, in chloroform, an intense peak
at λmax = 292(3.18) (B-band region).
Table 1 Thermal properties of the metallo-phthalocyanines
˙
Initial decomposition Main decomposition
Compound
M
temperature/°C
temperature/°C
4
5
6
7
8
9
H2
Ni
Zn
Co
Cu
Pb
364.9
380.0
405.0
395.9
410.3
395.4
482.3
460.0
472.1
464.2
495.4
434.8
The UV-Vis absorption spectra of the metallophthalocya-
nines 5–9 show intense Q band absorptions at λmax = 672(2.87),
678(2.80), 668(2.88), 676(2.83), 668 (2, 73) nm, respectively
(Figs 2 and 3). The single Q band in metallo-derivatives and

JOURNAL OF CHEMICAL RESEARCH 2012 667
Table 2 Antimicrobial activity of the metallo phthalocyanines
Sample
9
8
7
6
5
K*
DD*
MIC*
DD
MIC
DD
MIC
DD
MIC
DD
MIC
DD
MIC
A. haemolyticus
B. subtilis
12
–
1000
12
–
1000
12
–
2000
11
–
2000
12
–
2000
18(NET)
20(NET)
14(NET)
12(NET)
18(NET)
20(NET)
22(NET)
16(NET)
–(NET)
31–25
7–8
31–25
31–25
62–5
125
31–25
31–25
31–25
–
62–5
15–62
–
500
–
–
–
500
–
–
–
E. cloacae
13
–
13
–
1000
13
–
12
–
2000
12
–
2000
E. faecalis
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
E. coli
–
–
–
–
–
–
–
P. vulgaris
–
–
–
–
–
–
–
Ps. aeruginosa
St. aureus
–
–
–
–
–
–
–
–
–
–
–
–
–
–
C. albicans
Rhyzopus sp.
Fusarium sp.
Aspergillus sp.
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–(NET)
–
–
–
–
–
–
–
–(NET)
–(NET)
–
–
–
–
–
–
–
DD, Maximal inhibition zone; MIC, minimal inhibitor concentration; K, control; NET, Netilmicin. –, No activity
7, 8 and 9, were in the range of 11–13 mm and 500–2000 µL
mL−1, respectively (Table 2). As a result, 5, 6, 7, 8 and 9
exerted slight antibacterial activity against A. haemolyticus
and E. cloacae. However, the rest of the test microorganisms,
including fungi and the yeast, showed resistance. Lead (II)
phthalocyanine 9 and cobalt (II) phthalocyanine 7 were
found to be more effective compared to the other samples by
exhibiting inhibition zones in the disk diffusion assay (MIC:
500nµL mL−1).
be 0.059/n and independent of scan rate. In practical applica-
tions, ∆Ep of a couple is compared with that of universal indi-
cator ferrocene/ferrocenium couple. In our system, ∆Eps were
changed from 60 to 110 mV for ferrocene with increasing scan
rates from 0.010 to 1.00 V s−1. With respect to ∆Ep values, the
redox couples of the complex are electrochemically reversible
at all scan rates. SWVs clearly show the reversibility of the
redox processes (Fig. 4b).43 The effect of coupled chemical
reactions to the electron transfer reactions is illustrated with
the Ip,a/Ip,c ratio change as a function of the scan rate and Ip
changes as a function of the square root of the scan rate
Electrochemical measurements
1/2
Solution redox properties of the complexes were studied using
CV and SWV measurements in DCM containing TBAP
as supporting electrolyte on a Pt electrode. Table 3 lists the
assignments of the redox couples and the electrochemical
parameters, which included the half-wave peak potentials
(E1/2), anodic to cathodic peak potential separation (∆Ep), ratio
of the anodic to cathodic peak currents (Ipa/Ipc), and difference
between the first oxidation and reduction processes (∆E1/2).
Peak to peak separations as well as the E1/2 and ∆E1/2 values
were in agreement with the reported data for redox processes
in metallophthalocyanine complexes in the literature.35–42
Within the potential window of the DCM/TBAP electrolyte
system, two reductions and two oxidation processes are
recorded with CoPc 7 (Fig. 4). The couples at –0.30 V (∆Ep =
74 mV and Ip,a/Ip,c = 0.98), at –1.39 V(∆Ep = 64 mV and Ip,a/Ip,c
= 0.85), at 0.56 V (∆Ep = 90 mV and Ip,a/Ip,c = 0.87 at 0.100
Vs−1), and at 1.05 V are well resolved. For the first reduction
couple, ∆Ep values change from 60 to 140 mV with increasing
scan rate; suggesting electrochemical reversibility of the
electron transfer process.43 Theoretically, for a system that is
both electrochemically and chemically reversible, ∆Ep should
((Ipc–ν ). While the first reduction and oxidation processes are
purely diffusion controlled with respect to unit Ip,a/Ip,c ratio at
1/2
all scan rates and linear variation of Ipc–ν , deviation of the
Ip,a/Ip,c ratio from unity with decreasing scan rate indicates
the kinetic complication of the second electrochemically
reversible reduction and oxidation processes. First-row transi-
tion metals-Pc differ from those of the main-group metals-Pc
because the energy of the metal d-orbitals may be positioned
between the energies of HOMO and LUMO of the phthalocya-
nine (Pc2−) ligand. The first oxidation and first reduction pro-
cesses occur on the metal centre in the MPc complexes only
for Mn, Fe and Co derivatives in polar solvents such as DMF
and DMSO, while the first reduction and second oxidation
processes are metal-based in nonpolar solvents such as DCM.
Thus, the first reduction and second oxidation processes
of CoPc 7 recorded at −0.30 V and 1.05 V could be assigned
easily to the CoII/CoI and CoII/CoIII redox couples respectively
and the remaining processes to the phthalocyanine ring.39
Assignments of the redox couples are performed by the in situ
spectroelectrochemical measurements given below.
Table 3 Voltammetric data of CoPc (7) with the related metallophthalocyanines for comparison
d
Complex
Ring oxidations
MIII /MII
MII /MI
Ring reductions
∆E1/2
Ref
Tw
..CoPc aE1/2 vs SCE
(7)
0.56
1.05e
–
–
–0.30
74
0.98
–1.39
64
0.85
0.98
b∆Ep (mV) vs SCE
–
–
90
0.87
cIpa/Ipc
CoPc
CoPc
CoPc
CoPc
CoPc
CoPc
fE1/2 (in DMSO)
E1/2 (in THF)
0.91
0.75
0.48
1.13
0.43
1.55
–
–0.47
–0.21 (–0.55)
–0.43
–0.28 (–0.70)
–0.21 (–0.62)
–0.39 (–0.72)
–0.81
–1.29
–0.83
–1.42
–1.40
–1.45
–1.30 –1.62
–1.39
0.95
0.90
0.87
0.98
0.81
1.04
35
40
41
52
52
52
fE1/2 (in DMSO)
aE1/2 (in DCM)
aE1/2 (in DCM)
aE1/2 (in DCM)
0.85 (0.70)
0.76 (0.59)
0.65 (0.45)
a E1/2=(Epa+Epc)/2 at 0.100 V s−1. b ∆Ep= |Epa – Epc| at 0.100 V s−1. c Ipa/Ipc for reduction, Ipc/Ipa for oxidation processes at 0.100Vs−1 scan rate.
d ∆E1/2 = E1/2 (first oxidation)–E1/2 (first reduction) = HOMO–LUMO gap for metallophthalocyanines having electro-inactive metal cen-
tre (metal to ring (MLCT) or ring to metal (LMCT) charge transfer transition gap for MPc having redox active metal centre.). e The
process is recorded with SWV. Tw, This work.

668 JOURNAL OF CHEMICAL RESEARCH 2012
any potential application, the solution of CoPc 7 is green (x =
0.3581 and y = 0.4336). As the potential is stepped from 0 to
–0.50 V and then –1.50 V, the colour of the neutral [CoIIPc−2]
starts to change to yellow (x = 0.4378 and y = 0.4403) and then
orange (x = 0.4522 and y = 0.4221), these colours were
observed for the anionic forms of the complex respectively
during the reduction processes. Similarly the colour of the
solution changes from green to yellow (x = 0.4143 and
y = 0.4169) during the first oxidation process of CoPc 7. Deep
colour differences between the electrogenerated anionic and
cationic species of CoPc’s indicate possible electrochromic
applications of this complex.
Experimental
All reactions were carried out under dry N2 using standard Schlenk
techniques. The IR spectra were recorded on a Perkin Elmer 1600
FTIR spectrophotometer, using potassium bromide pellets. 1H and 13
C
NMR spectra were recorded on a Varian Mercury 200 MHz spectrom-
eter in CDCl3, and chemical shifts are reported (δ) relative to Me4Si as
internal Standard. Mass spectra were measured on a Varian 711 and
VG Zapspec spectrometer. UV-Vis absorpion spectra were measured
by a Unicam UV-Vis spectrometer. Melting points were measured
on an Electrothermal apparatus. A domestic oven (Arçelik MD 823,
350 W) was used for all the syntheses of metallophthalocyanines. A
Seiko II Exstar 6000 thermal analyser was used to record the DTA
curves under N2, with a heating rate of 20 °C min−1 in the temperature
range of 30–900 °C, using platinum crucibles.
(E)-4-(4-cinnamoylphenoxy) phthalonitrile (3): (E)-1-(4-hydroxy-
phenyl)-3-phenylprop-2-en-1-one 149 (1 g, 4.46 mmol) was dissolved
in dry DMF (15 mL) under N2 and 4-nitrophthalonitrile 2 (0.773 g, 4,
46 mmol) was added to the solution. After stirring for 10 min finely
ground anhydrous K2CO3 (3.07 g, 22.3 mmol) was added portionwise
within 2 h with efficient stirring. The reaction mixture was stirred
under N2 at 50 °C for 72 h. Then the solution was poured into ice-
water (100 mL) and was stirred for one day. The solid product was
filtered, washed in water and dried in vacuo over P2O5. The product
was crystallised from ethanol.Yield: 1.35 g (86%). M.p. 128 °C. Anal.
Calcd for C23H14N2O2: C, 78.84; H, 4.03; N; 8.00. Found: C, 78.87; H,
4.09; N, 8.02%. IR (KBr pellets), υmax (cm−1): 3077 (ArH), 2917–2851
(Aliphatic. C–H), 2232 (C≡N), 1603(C=O), 1589, 1486, 1338, 1277,
1211, 1155, 844, 773, 693. 1H NMR (CDCI3), (δ: ppm): 8.16–7.17(m,
ArH, olefinic C–H). 13C NMR (CDCl3), (δ: ppm): 189.00 (C=O),
160.80, 157.65 (ArC), 145.79 (ArCH), 136.08 (ArC), 135.88 (ArCH),
134.82 (ArC), 131.56, 131.13, 129.30, 128.81, 122.67, 122.50,
121.53, 120.41 ArCH, olefinic C–H), 118.13 (ArC), 115.44, 115.01
(C≡N), 110.14 (ArC). MS (ES+), (m/z): 350 [M]+.
Metal-free phthalocyanine (4): (E)-4-(4-cinnamoylphenoxy) phthalo-
nitrile 3 (300 mg, 0, 86 mmol), DBU (five drop) and dry n-pentanol
(4 mL) were added to a Schlenk tube and then heated and stirred
at 160 °C for 24 h under N2, then the reaction mixture was cooled at
30 °C and precipitated by adding ethanol. The solid product was fil-
tered and washed with ethanol. The green solid product was chroma-
tographed on silica gel with chloroform/methanol (7:1) as eluent.
Yield: 63 mg (21%). Anal. Calcd for C92H58N8O8: C, 78.76; H, 4.13;
N, 7.98. Found: C, 78.71; H, 4.19; N, 7.96%. IR (KBr tablets), υmax
(cm−1): 3430 (N–H), 3054 (ArH), 2924–2853 (Aliphatic. C–H), 1660,
1594, 1497, 1360, 1232, 1164, 1026, 824, 764, 697. 1H NMR (CDCI3),
(δ: ppm): 8.23–7.21(m, ArH, olefinic C–H). 13C NMR. (CDCl3), (δ:
ppm): 183.12 (C=O), 178.22, 172.74, 165.31, 160.82, 153.61, 154.76,
146.11, 134.13, 131.12, 130.86, 129.18, 128.65, 123.24, 120.32,
119.42, 119.28, 116.31, 110.28. UV-Vis[in chloroform) λmax /nm10−5
ε(mol−1cm−1)]: 698(2.58), 660(2.50), 632(2.33), 596(2.09), 292(3.18).
MS (ES+), (m/z): 1403 [M]+.
Fig. 4 (a) CVs of CoPc (7) (5.0 10−4 mol dm−3) at various scan
rates on a Pt working electrode in DCM/TBAP. (b) SWV of CoPc
(7) with SWV parameters: step size = 5 mV; pulse size = 100 mV;
Frequency = 25 Hz.
Spectroelectrochemical studies
All CoPc complexes give very similar in situ recorded UV-Vis
spectral changes and chromaticity diagrams. The differences
between them are only the wave length of the absorption bands
recorded. Figure 5 presents in situ UV-Vis spectral changes
and chromaticity diagrams of CoPc 7 as a representative of
the CoPcs complexes under applied potentials. As shown in
Fig. 5a during the first reduction process, the Q band shifts
from 667 to 700 nm with descending intensity with a new band
increasing at 471 nm. These spectroscopic changes indicate a
metal-based reduction and are assigned to the [CoIIPc−2]/
[CoIPc−2]1− process.44–48 During the electrochemical reduction
at –0.50 V, well-defined isosbestic points were recorded at
395, 562, and 685 nm. These isosbestic points demonstrate
that the reduction proceeds cleanly in deoxygenated DCM to
give a single, reduced species. Further reduction of [CoIPc−2]1−
at –1.50 V expresses the ring-based redox process. During this
process, the Q band decreases in intensity without shift, while
a new broad band is recorded at around 540 nm (Fig. 5b).
Well-defined isosbestic points demonstrate that the second
reduction proceeds to give single, reduced [CoIPc−3]2− species.
Figure 5c represents the spectral changes during the oxidation
processes of the complex. Decreasing of the Q band without a
shift and observation of new bands at around 530 and 750 nm
indicate the ring-based [CoIIPc−2] / [CoIIPc−1]1+ oxidation pro-
cess during the controlled potential application at 0.70 V.44–48
Further oxidation of the species showed the oxidation of the
metal centre. There are deep colour differences between
the electro-generated species of CoPc’s (Figure 5d). Without
Nickel (II) phthalocyanine (5): A mixture of (E)-4-(4-cinnamoyl-
phenoxy) phthalonitrile 3 (200 mg, 0.57 mmol), anhydrous NiCl2
(18.5 mg, 0.14 mmol), and 2-(dimethylamino)ethanol (3 mL) was
irradiated in a microwave oven at 175 °C, 350 W for 8 min. After
cooling to room temperature the reaction mixture was refluxed with
ethanol to precipitate the product which was filtered off and dried
in vacuo over P2O5. The obtained green solid product was purified by
column chromatography on silica gel with chloroform–methanol (5:1)
as eluent.Yield: 67mg (32%).Anal. Calcd for C92H56N8O8Ni: C, 75.68;
H, 3.83; N, 7.67. Found: C, 75.62; H, 3.89; N, 7.64%. IR (KBr

JOURNAL OF CHEMICAL RESEARCH 2012 669
Fig. 5 In situ UV-Vis spectral changes of CoPc (7). (a) (inset: initial part of the spectral changes at Eapp = -0.50 V) final part of the
spectral changes at Eapp = –0.50 V. (b) Eapp = –1.50 V. (c) Eapp = 1.00 V (Inset: Eapp = 1.60 V). (d) Chromaticity diagram of CoPc (7). (each
symbol represents the colour of electro-generated species; ꢀ: [CoIIPc−2], {:[CoIPc−2]−1 (initial part of the first reduction), U: [CoIPc−2]−
(final part of the first reduction), V: [CoIPc−3]−2, ‘: [CoIIPc−1]+1 œ:[CoIIIPc−1]+2.
pellets), υmax/cm−1: 3054 (ArH), 2917–2846 (Aliphatic. C–H), 1657,
1597, 1472, 1412, 1333, 1238, 1163, 1093, 1031, 834, 765. 1H NMR.
(CDCI3), (δ: ppm): 8.49–6.34 (m, ArH, olefinic C–H). 13C NMR.
(CDCl3), (δ: ppm): 189.06 (C=O), 175.25, 170.71, 162.01, 161.91,
157.81, 153.41, 143.51, 135.03, 133.12, 130.96, 129.19, 128.79,
122.49, 121.42, 119.86, 119.18, 117.51, 107.88. UV-Vis (chloroform):
λmax/nm: [(10−5 ε dm3 mol−1 cm−1)]: 672(2.87), 608(2.53), 318(3.23).
MS (ES+), (m/z): 1460 [M]+.
Zinc (II) phthalocyanine (6): A mixture of (E)-4-(4-cinnamoylphe-
noxy) phthalonitrile 3 (200 mg, 0.57 mmol), anhydrous Zn(CH3COO)2
(29 mg, 0.14 mmol), and 2-(dimethylamino)ethanol (3 mL) was irra-
diated in a microwave oven at 175 °C, 350 W for 6 min. After cooling
to room temperature the reaction mixture was refluxed with ethanol to
precipitate the product which was filtered off and dried in vacuo over
P2O5. The obtained green solid product was purified by column chro-
matography on silica gel with chloroform–methanol (6:1) as eluent.
Yield: 75 mg (36%). Anal. Calcd for C92H56N8O8Zn: C, 75.37; H, 3.82;
to room temperature the reaction mixture was refluxed with ethanol
to precipitate the product which was filtered off and dried in vacuo
over P2O5. The obtained green solid product was purified by column
chromatography on silica gel with chloroform–methanol (5:1) as
eluent.Yield: 79 mg (38%). Anal. Calcd for C92H56N8O8Co): C, 75.68;
H, 3.83; N, 7.67. Found: C, 75.65; H, 3.87; N, 7.69%. IR (KBr
pellets), υmax/cm−1: 3054 (ArH), 2923–2857 (Aliphatic. C–H), 1662,
1597, 1471, 1333, 1238, 1162, 1095, 833, 765. UV-Vis (chloroform):
λmax/nm: [(10−5 ε dm3 mol−1 cm−1)]: 668(2.88), 598(2.34), 312(3.18).
MS (ES+), (m/z): 1460 [M]+.
Copper (II) phthalocyanine (8): A mixture of (E)-4-(4-cinnamoyl-
phenoxy) phthalonitrile 3 (200 mg, 0.57 mmol), anhydrous CuCl2
(19.1 mg, 0.14 mmol) and 2-(dimethylamino)ethanol (3 mL) was irra-
diated in a microwave oven at 175 °C, 350 W for 5 min. After cooling
to room temperature the reaction mixture was refluxed with ethanol to
precipitate the product which was filtered off and dried in vacuo over
P2O5. The obtained green solid product was purified column chroma-
tography on silica gel with chloroform–methanol (6:1) as eluent.
Yield: 73 mg (35%). Anal. Calcd for C92H56N8O8Cu: C, 75.45; H,
3.82; N, 7.65. Found: C, 75.41; H, 3.87; N, 7.63%. IR (KBr pellets),
υmax/cm−1: 3049 (ArH), 2928–2857 (Aliphatic. C–H), 1659, 1596,
1473, 1404, 1333, 1237, 1163, 1093, 946, 834, 765. UV-Vis (chloro-
form):λmax/nm: [(10−5 ε dm3 mol−1 cm−1)]: 676(2.83), 604(2.35),
308(3.18). MS (ES+), (m/z): 1465 [M]+.
N, 7.64. Found: C, 75.43; H, 3.79; N, 7.68%. IR (KBr pellets), υmax
/
cm−1: 3049 (ArH), 2926–2846 (Aliphatic. C–H), 1659, 1596, 1487,
1393, 1334, 1235, 1163, 1088, 944, 835, 765. 1H NMR. (CDCI3), (δ:
ppm): 8.11–6.68 (m, ArH, olefinic C–H). 13C NMR. (CDCl3), (δ:
ppm): 187.56 (C=O), 172.14, 172.01, 162.98, 162.54, 158.54, 152.51,
144.97, 144.85, 135.82, 134.91, 134.53, 129.21, 128.70, 122.51,
121.72, 120.81, 118.35, 118.01, 110.01. UV-Vis (chloroform): λmax
/
nm: [(10−5 ε dm3 mol−1 cm−1)]: 678(2.80), 608(2.36), 278(3.19). MS
Lead (II) phthalocyanine (9): A mixture of (E)-4-(4-cinnamoylphe-
noxy) phthalonitrile 3 (200 mg, 0.57 mmol), anhydrous PbCl2
(39.6 mg, 0.14 mmol) and 2-(dimethylamino)ethanol (3 mL) was irra-
diated in a microwave oven at 175 °C, 350 W for 6 min. After cooling
to room temperature the reaction mixture was refluxed with ethanol to
precipitate the product which was filtered off and dried in vacuo over
(ES+), (m/z): 1467 [M+1]+.
Cobalt (II) phthalocyanine (7): A mixture of (E)-4-(4-cinnamoyl-
phenoxy) phthalonitrile 3 (200 mg, 0.57 mmol), anhydrous CoCl2
(18.5 mg, 0.14 mmol) and 2-(dimethylamino)ethanol (3 mL) was irra-
diated in a microwave oven at 175 °C, 350 W for 8 min. After cooling

670 JOURNAL OF CHEMICAL RESEARCH 2012
P2O5. The obtained green solid product was purified from the column
chromatography on silica gel with chloroform–methanol (7:1) as
eluents. Yield: 64 mg (28%). Anal. Calcd for C92H56N8O8Pb: C, 68.72;
H, 3.48; N, 6.96. Found: C, 68.76; H, 3.42; N, 6.94%. IR (KBr
pellets), υmax/cm−1: 3057 (ArH), 2921–2846 (Aliphatic. C–H), 1661,
1594, 1474, 1333, 1231, 1163, 1091, 939, 835, 765. 1H NMR. (CDCI3),
(δ: ppm): 8.03–6.72 (m, ArH, olefinic C–H). 13C NMR. (CDCl3), (δ:
ppm): 188.52 (C=O), 173.26, 171.06, 164.72, 163.56, 160.44, 154.72,
146.86, 145.32, 136.42, 135.18, 134.43, 128.52, 128.26, 122.14,
the bulk of the solution by a double bridge. Ferrocene was used as an
internal reference. Tetrabuthylammonium perchlorate (TBAP) in
dichloromethane (DCM) was employed as the supporting electrolyte
at a concentration of 0.10 mol dm−3. High purity N2 was used to
remove dissolved O2 at least for 15 minutes prior to each run and to
maintain a dinitrogen blanket during the measurements. IR compensa-
tion was applied to the CV and SWV scans to minimise the potential
control error.52
UV-Vis absorption spectra and chromaticity diagrams were mea-
sured by an OceanOptics QE65000 diode array spectrophotometer.
In situ spectroelectrochemical measurements were carried out by util-
ising a three-electrode configuration, thin-layer quartz spectroelectro-
chemical cell at 25 ˚C. The working electrode was a Pt gauze. A Pt
wire counter electrode and a SCE reference electrode, separated from
the bulk of the solution by a double bridge, were used. In situ electro-
colorimetric measurements under potentiostatic control were obtained
by using an OceanOptics QE65000 diode array spectrophotometer in
colour measurement mode by utilising a three-electrode configura-
tion, thin-layer quartz spectroelectrochemical cell. The standard illu-
minant A with 2 degree observer at constant temperature in a light
booth designed to exclude external light was used. Prior to each set of
measurements, background colour coordinates (x, y, and z values)
were taken at open-circuit, using the electrolyte solution without the
MPc under study. During the measurements, readings were taken as a
function of time under kinetic control.
121.46, 120.83, 118.38, 118.33, 112.27. UV-Vis (chloroform): λmax
/
nm: [(10−5 ε dm3 mol−1 cm−1)]: 668(2.73), 604(2.28), 286(3.13). MS
(ES+), (m/z): 1608 [M]+.
Antimicrobial activity assays
The metallophthalocyanines 5, 6, 7, 8 and 9 were individually tested
against 12 microorganisms, among which there are eight bacteria and
four fungi and yeast species. The list of microorganisms used is given
in Table 4.
The metallophthalocyanines 5, 6, 7, 8 and 9 were dissolved in
dimethyl sulfoxide to a final concentration of 30 mg mL−1. Antimicro-
bial tests were then carried out by the disk diffusion method.50 The
disks (6 mm in diameter), impregnated with samples (300 µg/disk),
were placed on the inoculated agar. Negative controls were prepared
with the same solvents used to dissolve the samples. Netilmicin
(30 µg/disk) was used as positive reference standard to determine the
sensitivity of one strain/isolate in each microbial species tested. The
inoculated plates were incubated at 37 °C for 24 h for clinical bacterial
strains, 48 h for the yeast, and 72 h for fungi isolates. Plant-associated
microorganisms were incubated at 27 °C. Antimicrobial activity was
evaluated by measuring the zone of inhibition against test organisms.
Each assay was repeated twice.
MIC values were determined for the bacterial strains that were
sensitive to the complexes in the disk diffusion assay. The inocula
of the bacterial strains were prepared from 12 h broth cultures, and
suspensions were adjusted to 0.5 McFarland standard turbidity. MIC
values of the complexes against bacterial strains and Candida
albicans isolates were determined on the basis of a microwell dilution
method51 with some modifications.
96-Well plates were prepared by dispensing 95 µL of nutrient broth
and 5 µL of the inoculum into each well; 100 µL from the stock solu-
tions of the samples prepared at the 500 µg mL−1 concentration was
added into the first wells. Then, 100 µL from the serial dilutions was
transferred into the six consecutive wells. The last well containing
195 µL of nutrient broth without compound and 5 µL of the inoculum
on each strip was used as a negative control. The final volume in each
well was 200 µL. The plate was covered with a sterile plate sealer.
The complexes tested in this study were screened twice against each
organism.
Conclusion
In this work, we describe the synthetic procedure and charac-
terisation of new metal-free and metallophthalocyanines
bearing oxygen donor atoms on the peripheral positions. In
addition, thermal properties of the phthalocyanines were
examined by thermogravimetric analysis. The biological acti-
vities (antibacterial, anticandidal and antifungal) of the new
metallo-phtalocyanines were also investigated. All of the new
metallo phtalocyanines exerted slight antibacterial activity
against A. Haemolyticus and E. cloacae. However, the rest of
the test microorganisms, including fungi and the yeast, showed
resistance. Voltammetric and spectroelectrochemical studies
show that cobalt phthalocyanine complex (7) give both
metal and ring-based, diffusion controlled, multi-electrons
and reversible/quasi-reversible reduction processes. Definite
determination of the colours of the electrogenerated anionic
and cationic forms of the complexes is important to decide
about their possible electrochromic application. Diffusion-
controlled, multi-electron and reversible redox processes of
the complexes indicate possible electrocatalytic activity for
different target species.
Electrochemical analysis
Electrochemical and spectroelectrochemical measurements were car-
ried out with a Gamry Reference 600 potentiostat/galvanostat utilising
a three-electrode configuration at 25 °C. The working electrode was a
Pt disc with a surface area of 0.071 cm2. The surface of the working
electrode was polished with a diamond suspension before each run. A
Pt wire served as the counter electrode. Saturated calomel electrode
(SCE) was employed as the reference electrode and separated from
Received 27 June 2012; accepted 17 September 2012
Paper 1201383 doi: 10.3184/174751912X13491019351916
Published online: 12 November 2012
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