Peripheral octa-substituted metal-free, cobalt(II) and zinc(II) phthalocyanines bearing coumarin and chloro groups: Synthesis, characterization, spectral and electrochemical properties

Article abstract of DOI:10.1016/j.poly.2012.08.080

Novel octa-substituted metal-free, cobalt(II) and zinc(II) phthalocyanines have been synthesized by using chloro and/or coumarin substituted phthalonitrile derivatives. The compounds were characterized by UV-Vis, IR, ¹H NMR, and MALDI-TOF mass spectrometry and elemental analysis. The effects of substituents, metals, solvents and concentration on spectroscopic properties and aggregation behaviour of the novel Pcs were investigated. Furthermore, the redox properties of the octa-4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin- substituted compounds were examined in dimethylsulfoxide and dichloromethane by voltammetry and in situ spectroelectrochemistry. Metal-free phthalocyanine and zinc phthalocyanine displayed ligand-based one-electron redox processes whereas cobalt phthalocyanine showed both ligand- and metal-based processes. A couple corresponding to the reduction of 4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin substituents was also detected. The redox processes of the compounds in dimethylsulfoxide were observed to be broad or split, due to the association of electron transfer processes by aggregation-deaggregation equilibrium.

Full text of DOI:10.1016/j.poly.2012.08.080

Polyhedron 48 (2012) 31–42
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Peripheral octa-substituted metal-free, cobalt(II) and zinc(II) phthalocyanines
bearing coumarin and chloro groups: Synthesis, characterization, spectral and
electrochemical properties
⇑
⇑
Selçuk Altun, Ali Rıza Özkaya , Mustafa Bulut
Department of Chemistry, Marmara University, 34722 Göztepe, Kadıköy, Istanbul, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel octa-substituted metal-free, cobalt(II) and zinc(II) phthalocyanines have been synthesized by using
chloro and/or coumarin substituted phthalonitrile derivatives. The compounds were characterized by
UV–Vis, IR, 1H NMR, and MALDI-TOF mass spectrometry and elemental analysis. The effects of substitu-
ents, metals, solvents and concentration on spectroscopic properties and aggregation behaviour of the
novel Pcs were investigated. Furthermore, the redox properties of the octa-4-(4-methoxyphenyl)-
7-oxo-8-methylcoumarin-substituted compounds were examined in dimethylsulfoxide and dichloro-
methane by voltammetry and in situ spectroelectrochemistry. Metal-free phthalocyanine and zinc
phthalocyanine displayed ligand-based one-electron redox processes whereas cobalt phthalocyanine
Received 15 May 2012
Accepted 21 August 2012
Available online 12 September 2012
Keywords:
Coumarin
Phthalocyanine
Octa-substitute
Aggregation
showed both ligand- and metal-based processes.
A couple corresponding to the reduction of
4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin substituents was also detected. The redox processes of
the compounds in dimethylsulfoxide were observed to be broad or split, due to the association of electron
transfer processes by aggregation–deaggregation equilibrium.
Electrochemistry
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Pc compounds have high tendency of aggregation, which is usu-
ally depicted as a coplanar association of rings progressing from
Phthalocyanines (Pcs) form an important class of macrocyclic
compounds [1–3] and continue to attract considerable interest as
pigments [4], dyes [4], sensors [5,6], photodynamic therapy sensi-
tizers [7–12], optical recording and nonlinear optical materials
[13,14], photovoltaics [15], catalysts [16] and electronic device
components [17–19]. Due to the growing interest in the properties
of metal Pcs, the synthesis of new examples involving various func-
tional substituents, with the aim of modifying their properties in
the applications listed above, has become necessary. Coumarin
(2H-1-benzopyran-2-one) and its derivatives, found naturally in
many higher plants and essential oils including tonka beans, sweet
clover and lavender [20,21], are used as anticoagulants [22], addi-
tives in food and cosmetics, in the preparation of insecticides, opti-
cal brighteners and dispersed fluorescent, laser dyes [23–25], anti-
HIV activities, etc. [26]. The family of functional Pcs has been an
interesting target for chemists for the development of further
chemical reactions on Pc complexes [27–31]. Therefore, we have
combined these two functional materials into a single compound
via synthetic methodology to obtain novel Pcs bearing different
substituents and metals.
monomer to dimer and higher order complexes. It is dependent
on the concentration, nature of the solvent, peripheral substituents,
metal ions and temperature [32,33]. In the aggregated state, the
electronic structure of the Pc rings is perturbed resulting in alterna-
tion of the ground and excited state electronic structure [34].
In the present work, octa-substituted Pcs bearing only one type
of substituent (4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin)
8–10 and both 4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin
and chloro substituents 5–7 were synthesized purely and charac-
terized by UV–Vis, IR and MALDI-TOF mass spectrometry, and ele-
mental analysis (Scheme 1). The effect of these substituents as well
as the central metal (Co and Zn), solvent (dimethylsulfoxide
(DMSO), dichloromethane (DCM), toluene and chloroform) and
concentration on the spectroscopic properties and aggregation
behaviours of the novel Pcs was also investigated. The understand-
ing of the redox properties of the Pc complexes is important in
terms of their applications in many areas. The redox or electron
transfer processes of these complexes occur at either the Pc ring
or the metal center, depending on the central metal and/or the
solvent medium. However, in most cases, it is not possible to distin-
guish such processes by voltammetry alone. In situ spectroelectro-
chemistry provide additional support for the assignment of these
redox processes. Moreover, it is also important in identifying the ef-
fect of aggregation–deaggregation equilibrium of Pcs on their redox
⇑
Corresponding authors. Tel.: +90 216 347 96 41; fax: +90 216 347 87 83.
E-mail addresses: aliozkaya@marmara.edu.tr (A.R. Özkaya), mbulut@marmar
a.edu.tr (M. Bulut).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.08.080

32
S. Altun et al. / Polyhedron 48 (2012) 31–42
Scheme 1. Synthesis of starting materials (3 and 4) and Pcs (5–10).
behaviour. Therefore, the electrochemical and in situ spectroelect-
rochemical behaviour of the synthesized Pc complexes were also
examined.
2.2. Sample and matrix preparation
-Cyano-4-hydroxycinnamic acid (ACCA) was prepared in tet-
a
rahydrofuran (THF) at a concentration of 10 mg/mL as matrix.
MALDI samples were prepared by mixing sample solutions
(2 mg/mL in chloroform) and matrix solution (1:10 v/v) in a
2. Experimental
0.5 mL EppendorfÒ micro tube. Finally, 0.5
lL of this mixture was
2.1. Material and methods
deposited on the sample plate, dried at room temperature, and
then analyzed.
IR Spectra and electronic spectra were recorded on a Shimadzu
FTIR-8300 (KBr pellet) and Shimadzu UV-1601 spectrophotometer,
respectively. Elemental analyses were performed by the Instru-
mental Analysis Laboratory of Tubitak–Ankara. 1H NMR and 13C
NMR spectra were recorded in d-chloroform with an instrument
Mercury-Vx 400 MHz. Mass spectra were acquired on Autoflex III
MALDI-TOF mass spectrometer (Bruker Daltonics, Germany)
equipped with a nitrogen UV-laser operating at 337 nm. Spectra
were recorded in reflectron mode with average of 50 shots.
2.3. Synthesis
2.3.1. 4-Chloro-5-(4-(4-methoxyphenyl)-8-methyl-coumarin-7-
yloxy)phthalonitrile 3 and 4,5-bis(4-(4-methoxyphenyl)-8-methyl-
coumarin-7-yloxy) phthalonitrile 4
4,5-Dichlorophthalonitrile 1 (1.00 g, 5.08 mmol) and 7-hydroxy-
4-(4-methoxyphenyl)-8-methylcoumarin 2 (5.73 g, 20.32 mmol)

S. Altun et al. / Polyhedron 48 (2012) 31–42
33
Fig. 1. The UV–Vis spectra of (A) 5, (B) 6, (C) 7, (D) 8, (E) 9 and (F) 10 in various solvents at 3.0 Â 10À6 mol dmÀ3
.
were dissolved in anhydrous dimethylformamide (DMF) (30 mL)
under N2 atmosphere. After stirring for 10 min, finely ground anhy-
drous K2CO3 (3.50 g, 25.37 mmol) was added by stirring. The reac-
tion mixture was stirred at 50 °C for 10 days under N2 atmosphere.
Then the mixture was poured in 250 ml cold aqueous solution of 5%
HCl. The formed precipitate was filtered off and washed with water.
After drying in vacuum at 50 °C, the crude product was purified by
column chromatography with silica gel eluting with DCM. Firstly,
compound 3 and then compound 4 were obtained purely by using
DCM and chloroform as eluting solvents, respectively.
Compound 3 is soluble in DCM, chloroform, THF, DMF and
DMSO. Mp: 194–196 °C. Yield: 1.30 g (58.04%). Anal. Calc. for C25-
H15ClN2O4: C, 67.80; H, 3.41; N, 6.33. Found: C, 68.02; H 3.31; N,
6.42%. IR (KBr pellet) mmax (cmÀ1): 530, 742, 826, 956, 1079,
1175, 1245, 1482, 1511, 1578, 1603, 1720, 2235, 2838, 2930,
3025, 3096. 1H NMR (CDCl3): d, ppm: 2.20 (s, 3H), 3.75 (s, 3H),
6.71 (d, J = 8.59 Hz, 1H), 6.87 (s, 1H), 6.91 (dd, J = 8.59 Hz and
J = 2.74 Hz, 2H), 7.27 (dd, J = 8.59 Hz and J = 2.73 Hz, 2H), 7.35 (d,
J = 8.98 Hz, 1H), 7.77 (s, 1H), 7.15 (s, 1H). 13C NMR. (CDCl3), d,
ppm: 161.04, 160.37, 156.75, 155.02, 154.07, 153.61, 135.77,
129.91, 127.21, 126.18, 120.27, 119.44, 117.62, 115.68, 114.48,
114.45, 110.47, 55.65, 9.26.
2931, 3042. 1H NMR (CDCl3) d, ppm: 2.20 (s, 6H), 3.74 (s, 6H),
6.70 (d, J = 8.99 Hz, 2H), 6.90 (dd, J = 8.99 Hz and J = 2.73 Hz, 4H),
7.03 (s, 2H), 7.11 (s, 2H), 7.25 (dd, J = 8.99 Hz and J = 2.73 Hz, 4H),
7.33 (d, J = 8.59 Hz, 2H). 13C NMR (CDCl3), d, ppm: 160.95, 160.35,
155.11, 154.30, 153.97, 150.59, 129.91, 127.19, 125.95, 122.14,
118.80, 117.14, 114.85, 114.45, 114.00, 113.99, 111.35, 55.48, 9.00.
2.3.2. General procedure of synthesis of metal-free Pcs 5 and 8
The compound 3 (0.20 g, 4.52 Â 10À4 mol) or compound 4
(0.20 g, 2.90 x10À4 mol) was heated in 2 ml dry 2-N,N-dimethyl-
aminoethanol in a sealed tube. The mixture was held at 160 °C
for 48 h under N2 atmosphere. After cooling to room temperature,
the reaction mixture was treated with dilute HCl and the mixture
was filtered and washed with water until the filtrate became neu-
tral. The raw green product was taken in the soxhlet apparatus and
then purified by washing with acetic acid, water, ethanol and ace-
tonitrile for 12 h respectively. The crude product was purified on
column chromatography with silica gel eluting with chloroform a
gradient of chloroform-THF from 0% to 5% THF.
2.3.2.1. 2(3),9(10),16(17),23(24)-Tetrachloro-3(2),10(9),17(16),24(23)-
tetrakis(4-(4-methoxyphenyl)-8-methylcoumarin-7-yloxy)phthalocya-
nine 5. The compound 5 was obtained and purified as mentioned by
the procedure above for synthesis of metal-free Pcs. This compound
is soluble in toluene, DCM, chloroform, THF, DMF, dimethylacetamide
(DMA) and DMSO Mp > 300 °C. Yield: 79.37 mg (58.24%). Anal. Calc.
for C100H62Cl4N8O16: C, 67.73; H, 3.52; N, 6.32. Found: C, 67.55; H,
Compound 4 is soluble in DCM, chloroform, THF, DMF and
DMSO. Mp: 175–178 °C. Yield: 0.29 g (8.56%). Anal. Calc. for
C
42H28N2O8: C, 73.25; H, 4.10; N 4.07. Found: C, 73.41; H, 3.98;
N, 4.19%. IR (KBr pellet) mmax (cmÀ1): 531, 725, 832, 956, 1081,
1173, 1245, 1292, 1365, 1422, 1499, 1603, 1713, 2232, 2838,

34
S. Altun et al. / Polyhedron 48 (2012) 31–42
Fig. 2. Positive ion in reflectron mode MALDI-TOF MS spectra of (A) 5, (B) 6, (C) 7, (D) 8, (E) 9 and (F) 10 in a-cyano-4-hydroxycinnamic acid. Inset spectrum shows expanded
molecular ion, sodium and potassium ion adducts mass region of the complex.
3.38; N, 6.46%. IR (KBr pellet)
m
max (cmÀ1): 534, 614, 760, 836, 883, 960,
H, 4.17; N, 4.06. Found: C, 73.01; H, 3.99; N, 4.21%. IR (KBr pellet)
mmax (cmÀ1): 532, 685,744, 837, 882, 986, 1021, 1085, 1178, 1252,
1367, 1433, 1513, 1599, 1645, 1732, 2841, 2865, 2956, 3073, 3298.
MALDI-TOF mass m/z: 2754.573 (M)+, 2777.742 (M+Na)+. UV–Vis
1023, 1086, 1177, 1250, 1366, 1440, 1513, 1603, 1645, 1730, 2854,
2924, 2955, 3289. MALDI-TOF mass: m/z 1770.025 (M)+ and
1793.664 (M+Na)+. UV–Vis (DCM): kmax (nm), (log
e): 310 (5.742),
609 (4.954), 644 (5.289), 678 (5.384), 710 (5.732). 1H NMR. (CDCl3),
d, ppm: 7.73–6.98 (m, 36H, Ar–H), 3.82 (s, 12H, CH3–O), 2.27 (s, 12H,
CH3–), 1.48 (s, 2H). 13C NMR (CDCl3), d, ppm: 160.72, 151.80, 135.75,
135.64, 132.72, 129.99, 127.56, 125.36, 125.05, 114.10, 55.43, 38.01,
34.21, 30.46.
(DCM): kmax (nm), (loge): 295 (5.316), 343 (5.343), 605 (4.732),
632 (4.988), 665 (5.241), 699(5.498).). 1H NMR (CDCl3), d, ppm:
7.74–6.92 (m, 64H, Ar–H), 3.74 (s, 24H, CH3–O), 2.64 (s, 24H,
CH3–), 1.53 (s, 2H).
2.3.3. General procedure of synthesis of metal Pcs 6,7,9 and 10
A mixture of compound 3 (0.20 g, 4.52 Â 10À4 mol) or com-
pound 4 (0.20 g, 2.90 Â 10À4 mol) with Zn(OAc)2Á2H2O (0.13 g,
5 Â 10À4 mol) or Co(OAc)2.4H2O (0.09 g, 5 Â 10À4 mol) was
powdered in a quartz crucible and transferred in a reaction tube.
2.3.2.2.
2,3,9,10,16,17,23,24-Octakis(4-(4-methoxy-phenyl)-8-
methyl-coumarin-7-yloxy)phthalocyanine 8. Compound 8 is soluble
in toluene, DCM, chloroform, THF, DMF and DMSO. Mp > 300 °C.
Yield: 37.27 mg (35.50%). Anal. Calc. for C168H114N8O32: C, 73.20;

S. Altun et al. / Polyhedron 48 (2012) 31–42
35
Table 1
Spectral data for Pcs 5–10 in various solvents at 3.0 Â 10À6 mol dmÀ3
.
Solvent
Pcs
Q-band, kmax/nm
Log
e
B-band, kmax/nm
Loge
Toluen
CHCl3
DCM
DMSO
Toluen
CHCl3
DCM
DMSO
Toluen
CHCl3
DCM
DMSO
Toluen
CHCl3
DCM
DMSO
Toluen
CHCl3
DCM
DMSO
Toluen
CHCl3
DCM
5
5
5
5
6
6
6
6
7
7
7
7
8
8
8
8
9
9
9
9
10
10
10
10
704, 673, 645, 610
705, 674, 644, 613
701, 669, 644, 609
710, 678, 644, 623
679, 615
676, 610
678, 610
659, 629
5.603, 5.463, 5.143, 5.010
5.638, 5.547, 5.125, 4.959
5.694, 5.561, 5.141, 4.954
5.732, 5.384, 5.289, 5.267
5.099, 4.756
5.542, 4.905
5.504, 4.830
5.357, 5.337
303
302
310
312
309
317
315
319
315
352
336
345
343
345
343
334
311
327
312
320
295
347
313
342
5.654
5.742
5.742
5.784
5.292
5.627
5.573
5.694
5.326
5.182
5.343
5.598
5.231
5.262
5.343
5.670
5.802
5.374
5.610
5.862
5.413
5.434
5.525
5.586
679, 652, 612
680, 651, 613
685, 614
5.372, 4.602, 4.690
5.525, 4.746, 4.771
5.568, 5.024
675, 639
5.529, 5.438
702, 668, 636, 607
700, 665, 635, 605
699, 665, 632, 605
691, 619
673, 607
671, 607
676, 612
656, 625
689, 621
682, 617
5.571, 5.258, 5.917, 4.647
5.481, 5.276, 4.855, 4.613
5.498, 5.241, 4.988, 4.732
5.188, 5.323
5.373, 4.758
5.414, 4.822
5.605, 5.113
5.254, 5.212
5.448, 4.735
5.673, 4.967
690, 621
681, 642
5.641, 4.984
5.435, 5.329
DMSO
0.30 ml of DMF was added to this reaction mixture, and then the
mixture was heated in the sealed glass tube for 20 min under dry
N2 atmosphere at 320 °C. After cooling to room temperature,
3 mL of DMF was added to the residue to solve the product. The
reaction mixture was precipitated by adding acetic acid. The pre-
cipitate was filtered and washed with hot acetic acid, water, etha-
nol and acetonitrile for 12 h in the soxhlet apparatus respectively.
The crude product was purified by column chromatography with
silica gel eluting with chloroform a gradient of chloroform-THF
from 0 to 5% THF.
2.3.3.1. 2(3),9(10),16(17),23(24)-Tetrachloro-3(2),10(9),17(16),24(23)-
tetrakis(4-(4-methoxyphenyl)-8-methylcoumarin-7-yloxy)phthalocyani-
nato cobalt(II) 6. The compound 6 was obtained and purified as ex-
plained by the procedure given above for synthesis of metal Pcs. It is
soluble in toluene, DCM, chloroform, THF, DMF and DMSO.
Mp > 350 °C. Yield: 101.2 mg (74.26%). Anal. Calc. for C100H60Cl4CoN8-
O16: C, 65.62, H, 3.30; N, 6.12. Found: C, 65.85; H, 3.15; N, 5.97%. IR
(KBr pellet) mmax (cmÀ1): 533, 742, 758, 837, 865, 901, 960, 1042,
1086, 1178, 1250, 1278, 1251, 1368, 1415, 1455, 1488, 1513, 1603,
1731, 2865, 2926, 2960. MALDI-TOF mass m/z: 1827.334 (M)+ and
Fig. 3. The UV–Vis spectra of 8 in the range of 3 Â 10À6–1.0 Â 10À7 mol dmÀ3 in
DMSO. The inset shows the plot of absorbance vs. concentration.
cedure given above. Compound 9 is soluble in toluene, DCM,
chloroform, THF, DMF, DMA and DMSO. Mp > 350 °C. Yield:
40 mg (38.10%). Anal. Calc. for C168H112CoN8O32: C, 71.71; H,
4.01; N, 3.98. Found: C, 71.55; H, 3.86; N, 4.21%. IR (KBr pellet)
1850.125 (M+Na)+. UV–Vis (DCM): kmax (nm), (log
e): 315 (2.573),
610 (4.830), 678 (5.504).
m
max/cmÀ1: 533, 687, 751, 836, 886, 1088, 1109, 1178, 1255,
2.3.3.2. 2(3),9(10),16(17),23(24)-Tetrachloro-3(2),10(9),17(16),24(23)-
tetrakis(4-(4-methoxyphenyl)-8-methyl-coumarin-7-yloxy)phthalocyan-
inato zinc(II) 7. The compound 7 was obtained and purified as
explained by the procedure explained above. This compound is soluble
in toluene, DCM, chloroform, THF, DMF, DMA and DMSO. Mp > 300 °C.
Yield: 95.15 mg (69.82%). Anal.Calc.forC100H60Cl4N8O16Zn: C, 65.39;H,
3.29; N, 6.10. Found: C, 65.61; H, 3.11; N, 5.93%. IR (KBr pellet) mmax
(cmÀ1): 527, 566, 604,743, 829, 864, 944, 1024, 1042, 1084, 1114,
1175, 1247, 1366, 1393, 1422, 1469, 1512, 1595, 1724, 2838, 2933,
1367, 1403, 1439, 1513, 1598, 1731, 2930, 2957. MALDI-TOF mass
m/z: 2811.444 (M)+ and 2834.659 (M+Na)+. UV–Vis (DCM): kmax
(nm), (loge): 312 (5.610), 612 (5.113), 676 (5.605).
2.3.3.4. 2,3,9,10,16,17,23,24-Octakis(4-(4-methoxyphenyl)-8-methyl-
coumarin-7-yloxy)phthalocyaninato zinc(II) 10. The compound 10
was obtained and purified as explained by the procedure given
above. This compound is soluble in toluene, DCM, chloroform,
THF, DMF, DMA and DMSO. Mp > 300 °C. Yield: 58.23 mg
(55.46%). Anal. Calc. for C168H112N8O32Zn: C, 71.55; H, 4.00; N,
3.97. Found: C, 71.44; H, 3.89; N, 4.11%. IR (KBr pellet) mmax
(cmÀ1): 531, 615,742, 833, 863, 884, 990, 1024, 1079, 1176,
1245, 1366, 1389, 1422, 1486, 1511, 1596, 1721, 2836, 2936,
2930, 3068. MALDI-TOF mass m/z: 2816.547 (M)+, 2839.669
+
3068. MALDI-TOF mass m/z: 1832.486 (M)+ and 1855.528 (M+Na) ,
1871.712 (M+K)+. UV–Vis (DCM): kmax (nm), (log
e): 336 (5.343), 614
(5.024), 690 (5.568). 1H NMR (CDCl3), d, ppm: 7.80–7.04 (m, 36H,
Ar–H), 3.85 (s, 12H, CH3–O), 2.61 (s, 12H, CH3–).
2.3.3.3. 2,3,9,10,16,17,23,24-Octakis(4-(4-methoxyphenyl)-8-methyl-
coumarin-7-yloxy)phthalocyaninato cobalt(II) 9. A blue-green reac-
tion product 9 was obtained and purified as explained by the pro-
(M+Na)+ and 2855.621 (M+K)+. UV–Vis (DCM): kmax (nm), (log
e):

36
S. Altun et al. / Polyhedron 48 (2012) 31–42
Table 2
Voltammetric data on Pt for 8–10.
Complex
Electrolyte
Ring oxidations
MII/MIII MII/MI
Ring reductions
Substituent reduction fDE1/2 Reference
a8 (H2Pc)
DMSO/TBAP
dE1/2 (V)
eDEp (V)
dE1/2 (V)
eDEp (V)
dE1/2 (V)
eDEp (V)
À0.51
0.060
À0.56
0.090
À0.84
–
À0.97
0.100
À0.88
0.080
À1.11
0.100
tw
bBS-H2Pc
DMSO/TBAP
DCM/TBAP
31
a9 (CoPc)
0.77
0.100
1.20
–
0.35
0.100
0.35
0.060
À0.19
À1.58
–
0.96
0.76
0.66
1.36
1.31
1.51
tw
tw
31
tw
tw
31
0.060
cDMSO/TBAP dE1/2 (V)
eDEp (V)
DMSO/TBAP
À0.41(À0.65) À1.25
À1.84
0.100
À0.31
0.060
–
–
bBS-CoPc
dE1/2 (V)
eDEp (V)
À1.24
0.100
À0.71
0.080
À1.63
0.220
À1.63
0.200
À1.62
0.14
a10 (ZnPc) DCM/TBAP
dE1/2 (V) 1.13 0.65
À1.01
eDEp (V)
–
0.080
0.81 (0.91)
0.060
cDMSO/TBAP dE1/2 (V)
eDEp (V)
DMSO/TBAP
À0.50 (À0.63) À0.91(À1.19)
0.100 0.060
bBS-ZnPc
dE1/2 (V) 1.06 0.96
eDEp (V)
À0.55 (À0.70) À0.81 (À1.07) À1.65
0.060 0.200 (0.18) 0.200
a
b
c
d
e
f
Octa-4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin- substituted phthalocyanine, reported in this study.
Previously reported beta-7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin substituted phthalocyanine.
The redox behaviour of the compounds in DMSO/TBAP was complicated by aggregation phenomenon and thus, some redox couples were split.
E1/2 = (Epa + Epc)/2 at 0.050 V sÀ1
.
D
D
Ep = Epa À Epc (usually at 0.050 V sÀ1).
E1/2 = E1/2 (first oxidation) À E1/2 (first reduction).
313 (5.525), 621 (4.984), 690 (5.641). 1H NMR (CDCl3), d, ppm:
7.60–6.80 (m, 64H, Ar–H), 3.74 (s, 24H, CH3–O), 2.36 (s, 24H, CH3).
starting compounds 3 and 4, respectively (Scheme 1). In fact, the
phthalocyanine product 5, 6 or 7 was a mixture of its positional iso-
mers due to the involvement of two different substituents (chlorine
and coumarine derivative) in the phthalonitrile precursor. The
photophysical and electrochemical data of the relevant compounds
were obtained from the measurements performed on the mixtures
of their isomers.
The characterization of the new products involved a combina-
tion of methods including The IR, UV–Vis, 1H NMR and MALDI-
TOF mass spectrometry and elemental analyses. The results are
consistent with the proposed structures.
The formation of starting compounds was confirmed clearly by
the appearance of the new absorption bands at 2232 cmÀ1 (–C„N)
and 1280 cmÀ1 (Ar–O–Ar) for 3, and at 2235 cmÀ1 (–C„N) and
1292 cmÀ1 (Ar–O–Ar) for 4 in their FT-IR spectra. Compounds 3
and 4 exhibited –C@C– double bond at 1603 and 1604 cmÀ1, couma-
rin carbonyl (lactone, –C@O) at 1720 and 1713 cmÀ1, –CH3 at
2838;2930 and 2838;2931 cmÀ1 and Ar–H stretching frequencies
at 3070 and 3041 cmÀ1 respectively. The FT-IR spectra of Pcs 5–10
showed Ar–O–Ar, @C@C–, –C@O, –C@N, –CH3 and aromatic –CH–
peaks within the ranges of 1220–1285, 1560–1655, 1760–1780,
2.4. Electrochemistry
The cyclic and differential pulse voltammetry measurements
were carried out with a PAR VersoStat II Model potentiostat/galva-
nostat controlled by an external PC and utilizing a three-electrode
configuration at 25 °C. The working electrode was a Pt plate with a
surface area of 0.10 cm2. A Pt wire served as the counter electrode.
Saturated calomel electrode (SCE) was employed as the reference
electrode and separated from the bulk of the solution by a double
bridge. Electrochemical grade tetrabutylammonium perchlorate
(TBAP) in extra pure DMSO or DCM was employed as the support-
ing electrolyte at a concentration of 0.10 mol dmÀ3. High purity N2
was used for deoxygenating the solution at least 20 min prior to
each run and to maintain a nitrogen blanket during the measure-
ments. In situ spectroelectrochemical measurements were carried
out by an Agilent Model 8453 diode array spectrophotometer
equipped with the potentiostat/galvanostat and utilizing an opti-
cally transparent thin layer cell with three-electrode configuration
at 25 °C. The working electrode was transparent Pt gauze. Pt wire
counter electrode and a SCE reference electrode separated from
the bulk of the solution by a double bridge were used.
3. Results and discussion
3.1. Synthesis and characterization
Octa-substituted Pcs bearing eight 4-(4-methoxyphenyl)-7-oxo-
8-methylcoumarin substituents 8–10 and four chloro substituents
in addition to four 4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin
substituents 5–7 were synthesized and characterized to investigate
differences in their spectroscopic and aggregation behaviours. 4,5-
dichlorophthalonitrile (1) and 7-hydroxy-4-(4-methoxyphenyl)-8-
methylcoumarin (2) have been synthesized by the method in the
literature [35,36]. Unfortunately, despite our all efforts, the reaction
between 1 and 2 produced a mixture of 3 and 4 rather than the
single product of 3 or 4. For this reason, the compounds 3 and 4
in the reaction mixture were separated by column chromatography.
Compounds 5–7 and 8–10 were synthesized by using the new pure
Fig. 4. Cyclic voltammograms of 5.0 Â 10À4 mol dmÀ3 8 in DMSO/TBAP.

S. Altun et al. / Polyhedron 48 (2012) 31–42
37
1670–1720, 2800–2980 and 3060–3080 cmÀ1, respectively. The IR-
spectra of the Pcs are very similar, with the exception of metal-free
Pcs 5 and 8, showing a N–H weak stretching band due to the inner
core at 3298, 3289 cmÀ1 respectively. In addition, disappearing of
–C„Npeaksat2232–2235 cmÀ1 clearlyindicatedthatstartingcom-
pounds 3 and 4 were converted to the Pcs 5–10.
The 1H NMR spectra of 3 and 4 showed characteristic signals for
methyl (–CH3) protons at d 2.20 ppm and methoxy (–OCH3) pro-
tons at d 3.75 and 3.74 ppm each a singlet, respectively. The peaks
within the ranges of 6.71–7.15 and 6.70–7.33 ppm indicated the
presence of the aromatic protons in compounds 3 and 4, respec-
tively (Supplementary Materials, Figs. S1 and S2). The 1H NMR
spectra of the Pc compounds 5, 7, 8 and 10 were almost identical
with those of the starting phthalonitrile compounds 3 and 4, ex-
cept broadening and small shifts in the peaks of the formers. The
1H NMR spectra of 5, 7, 8 and 10 showed aromatic protons signals
within the ranges of 7.73–6.98 ppm for 5, 7.80–7.04 ppm for 7,
7.74–6.92 ppm for 8, and 7.60–6.80 ppm for 10 and aliphatic pro-
tons signals within the range of 3.85–2.27 ppm (–OCH3 and –
CH3) for 5, 7, 8 and 10, as expected (Supplementary Materials, Figs.
S3–S6).
The 13C NMR signals for aromatic and aliphatic (–OCH3 and –
CH3) carbon atoms appeared within the range of 161.04–
110.47 ppm, at 55.65 ppm, and at 9.26 ppm for 3 and within the
range of 160.95–111.35 ppm, at 55.48 ppm and at 9.00 ppm for
4, respectively (Supplementary Materials, Figs. S7 and S8).
The UV–Vis spectra of Pcs 5–10 in various solvents (DMSO,
DCM, toluene and chloroform) showed characteristic Q band
absorptions around 656–705 nm which were attributed to the
p
?
p⁄ transitions from the highest occupied molecular orbital
(HOMO) to the lowest unoccupied molecular orbital (LUMO) of
the Pc ring. The other B bands in the UV range 288–352 nm were
due to transitions from the deeper
p levels to the LUMO (Fig. 1).
In MALDI-TOF-MS spectra, the molecular ion peaks of 5–10
were observed at 1770.025, 1827.334, 1832.486, 2754.573,
2811.444 and 2816.547 Da, respectively (Fig. 2). Beside the molec-
ular ion peaks of the complexes, sodium ion adducts were also ob-
served. In addition, potassium ion adducts were only observed in
the spectra of zinc Pcs (7 and 10). The complexes showed low frag-
mentation under the MALDI-TOF-MS conditions in reflectron
mode. All high resolved experimental peaks matched perfectly
the theoretical peaks of the complexes determined by isotropic
software calculation. Thus, MS analyses confirmed the molecular
formula of all Pc samples.
3.2. Spectral properties
The Q and B-band absorption data of 5–10 in different solvents
are summarized in Table 1. The split Q-band absorptions of metal-
free Pcs have been observed at 673 and 704 nm, 674 and 705 nm,
and 669 and 701 nm for 5 and at 668 and 702 nm, 665 and 700 nm,
and 665 and 699 nm for 8 in toluene, chloroform and DCM, respec-
tively (Fig. 1A and B). D2h symmetry of 8 causes the splitting of its
Q-band absorptions. Its split Q-band absorption in non-coordinat-
Fig. 5. Cyclic voltammograms of (A) 5.0 Â 10À4 mol dmÀ3 (B) 2.0 Â 10À4 mol dmÀ3
10 in DMSO/TBAP and (C) 5.0 Â 10À4 mol dmÀ3 10 in DCM/TBAP. The dotted lines in
(A) displays differential puls voltammogram of 5.0 Â 10À4 mol dmÀ3 10 in DMSO/
TBAP.
ing solvents toluene, chloroform and DCM can be attributed to p–
p
⁄ electronic transitions of its monomeric species, but not to the
aggregated species. There are also vibrational absorptions as two
shoulders in its spectrum in the mentioned solvents. The UV–Vis
spectrum of 8 in DMSO involves a broad and weak non-split Q-
band absorption at 691 nm, in addition to a broad and relatively
much stronger absorption at 619 nm, and the B-band at 334 nm
as a single peak (Fig. 1B).
tions and B-bands appear within the range of 607–621 and 309–
352 nm, respectively (Fig. 1C–F and Table 1). However, these com-
plexes display broad or split absorptions in the Q-band region in
DMSO, due to the formation of their aggregated species in this sol-
vent. The comparison of the molar absorptivity of 6 and 7 with
those of 9 and 10 shows that the formers involving eight oxy-cou-
marin substituents have lower molar absorptivity than the latters
with four oxy-coumarin substituents and four chlorine atoms
The UV–Vis spectra of 6, 7, 9 and 10 in non-coordinating sol-
vents toluene, chloroform and DCM exhibit sharp and non-split
Q-band absorptions within the range of 671–690 nm which are
characteristic for monomeric metal Pcs. Their vibrational absorp-

38
S. Altun et al. / Polyhedron 48 (2012) 31–42
Fig. 6. In situ UV–Vis spectral changes during controlled-potential electrolysis of 10 in DMSO /TBAP or DCM/TBAP.
(Table 1). This comparison indicates that the aggregation tenden-
cies of the latters are higher than those of the formers, due to
the increasing intermolecular interactions as a result of the in-
crease in the number of more electron-withdrawing oxy-coumarin
substituents.
Aggregation behaviour of 5–10 was also examined by the spec-
tra monitored at different concentrations in DMSO with the aim of
providing additional support for the formation of their aggregated
species in this solvent. In general, the decrease in the absorptions
of the blue shifted broad bands was more pronounced than that
of the main Q-band corresponding monomeric species. The spectra
of 8 at different concentrations in DMSO within the range between
3 Â 10À6 and 1.0 Â 10À7 mol dmÀ3 are shown in Fig. 3 as a typical
example. As the concentration of 8 is decreased, the decrease in the
absorption for the band at 619 nm is more pronounced than that
for the main Q-band and thus, their intensities become approxi-
mately equal at the concentration of 0.10 Â 10À6 mol dmÀ3. This
observation provides strong evidence for the assignment of the
band at 619 nm to the H-type aggregates. The aggregation phe-
nomenon was also tested by the change of absorbance with con-
centration within the range of 3.0 Â 10À6 to 1.0 Â 10À7 mol dmÀ3
in DMSO. The presence of aggregated species was confirmed by
the deviation from Beer–Lambert law (inset in Fig. 3) [37].
The term solvatochromism is used to describe the pronounced
change in position (and sometimes intensity) of the UV–Vis
absorption band, that accompanies a change in the polarity of
the medium. A hypsochromic (or blue) shift with increasing sol-
vent polarity is usually named negative solvatochromism, while
the positive solvathochromism corresponds to a bathochromic
(or red) shift [38]. Solvent effects on UV–Vis absorption bands of
the Pcs was studied in several solvents with different polarities
(toluene < DCM < chloroform < DMSO). When UV–Vis spectra of

S. Altun et al. / Polyhedron 48 (2012) 31–42
39
CoPcs (6 and 9) and ZnPcs (7 and 10) in DMSO (as a polar solvent)
compared with in non-polar solvents, 14–17 nm and 7–9 nm the
blue shift were observed respectively. On the other hand, Q absorp-
tion bands of metal free Pcs 5 and 8 were shifted 9–12 nm to red
(Fig. 1 and Table 1).
When the spectrum Pcs 5–7 bearing two different substituents
(Cl and oxy-coumarin) compared with Pcs 8–10 bearing only one
type of substituent (oxy-coumarin), it was observed that the Q
band of the 8 and 9 were blue-shifted approximately 5 nm accord-
ing to 5 and 6 but 10 were red-shifted approximately 2 nm accord-
ing to 7. These UV–Vis spectra show that peripheral substituents of
Pcs 5–10 affect their spectral properties weakly (Fig. 1 and Table 1).
in the redox potentials of aggregated and deaggregated species.
The peripheral nature of the substituents in beta-substituted Pcs,
leadingto theplanarityshouldbe themainreasonfor thehighaggre-
gation tendency of these compounds. Fig. 5C shows the cyclic vol-
tammograms of 5.00 Â 10À4 mol dmÀ3 solution of 10 in DCM/TBAP
at different scan rates. It also displays three reduction (R1-R3) pro-
cesses, but two oxidation couples (O1 and O2) due to relatively wide
positive potential range available, compared to that in DMSO/TBAP.
The redox couples of 10 in DCM/TBAP are neither broad nor split
which shows the absence of aggregated species. The R4 couple,
appearing at high negative potentials at the end of solvent-limited
cathodic potential range in DMSO/TBAP and DCM/TBAP, should cor-
respond to the reduction of 4-(4-methoxyphenyl)-7-oxo-8-methyl-
coumarin substituents since these groups, less conjugated as
compared with the Pc ring are expected to be reduced at relatively
high negative potentials. Anyway, the redox-active nature of oxy-
coumarin substituents in Pc compounds has been reported previ-
ously [37,40]. It is clear from the well-known redox-inactive nature
of metal center in zinc Pcs, other redox processes in DMSO/TBAP and
DCM/TBAP (R1, R2, O1 and O2) can be attributed to successive addi-
tion of electrons to, and removal of an electron from the Pc ring [39].
However, in situ spectroelectrochemical measurements were car-
ried out during the controlled potential electrolysis of 10 in DMSO
at a suitable potential corresponding to its first reduction process
since this type of measurements do not only have a vital importance
in determining the nature of the redox processes, but also provide
3.3. Electrochemistry
The electrochemical behaviour of octa-4-(4-methoxyphenyl)-7-
oxo-8-methylcoumarin- substituted Pcs 8–10 was investigated by
cyclic voltammetry, differential pulse voltammetry and in situ
spectroelectrochemistry in DMSO and DCM involving tetrabutyl-
ammonium perchlorate (TBAP) as supporting electrolyte. The vol-
tammetric data of the complexes, including the half-wave redox
potential value (E1/2), anodic-to-cathodic peak potential separation
(D
Ep) and the difference between the first oxidation and reduction
potential ( E1/2) are summarized in Table 2 which also includes
D
the data for recently reported tetra-substituted analogues of 8–
10 for comparison.
Compound 8 displayed two reduction couples (R1 and R2) within
the available potential range in DMSO/TBAP (Fig. 4). These processes
are clearly Pc ring-based since compound 8 is metal-free. As
observed previously for tetra-substituted analogue of 8 [37], the
first oxidation process of 4 is out of the accessible potential range
of DMSO/TBAP medium, probably as a result of the stabilization of
the HOMO and the LUMO, and thus, shifting the redox potentials
towards more positive potentials by 4-(4-methoxyphenyl)-7-oxo-
8-methylcoumarin substituents. Similarly, both cathodic and ano-
dic waves of the first and the second reduction couples (R1 and
R2) of 8 are broad which can be attributed to the presence of its
aggregated species and equilibrium between monomeric and
aggregated species. However, as shown in Table 2, the first reduc-
tion process of 8 occurs at a potential (E1/2 = -0.51 V) somewhat less
negative than that (E1/2 = À0.56 V) of its tetra-substituted analogue
[37]. The separation between the first and second ring reductions is
approximately 0.46 V, which is in agreement with the reported ones
for redox processes in metal-free Pcs [39]. The redox potentials of 8
are less negative than those of the previously reported [39] unsub-
stituted metal-free Pcs in a similar coordinating solvent, DMF, due
to electron withdrawing nature of 4-(4-methoxyphenyl)-7-oxo-8-
methylcoumarin substituents, suggesting that the redox potentials
of Pcs can be changed remarkably by peripheral substituents.
Fig. 5A shows the cyclic and differential pulse voltammograms of
5.00 Â 10À4 mol dmÀ3 solution of 10 in DMSO/TBAP at different scan
rates. It shows three reduction processes (R1–R3) and an oxidation
couple (O1). As shown in Fig. 5A, the first and second reduction
couples are remarkably broad. The oxidation process (O1) could be
identified only by DPV, due to its high positive potential within the
available potential range. Furthermore, R1, R2 and O1 processes
are split on the differential pulse voltammogram of 10. When the
concentration of the compound was changed from 5.00 Â 10À4
-
mol dmÀ3 to 2.00 Â 10À4 mol dmÀ3, the broadness of the R1 and
R2 decreased considerably (Fig. 5B). All these observations indicates
clearly that the electron transfer processes of 10 in DMSO/TBAP are
associated by the equilibrium between aggregated and deaggregat-
ed species. The
p
–
p
⁄ interactions between the
p-electron clouds of
Fig. 7. Cyclic voltammograms of 5.0 Â 10À4 mol dmÀ3 9 in (A) DMSO/TBAP (B)
DCM/TBAP. The dotted lines in (A) displays differential puls voltammogram of
5.0 Â 10À4 mol dmÀ3 9 in DMSO/TBAP. The insets in (A) and (B) shows the cyclic
voltammograms monitored with different switching potentials.
adjacent Pc macrocycles as a result of their coplanar association is
called as aggregation. This phenomenon results generally in broad-
ening of the redox signals or their splitting, due to the differences

40
S. Altun et al. / Polyhedron 48 (2012) 31–42
support for the evaluation of the aggregation effect on the redox pro-
cesses. Fig. 6A and B show the two groups of in situ spectroelectro-
chemical changes, each of which associated with different
isosbestic points, during the controlled-potential electrolysis of the
solution of 10 in DMSO/TBAP at À0.80 V versus SCE. In Fig. 6A, the
Q-band absorption in the spectrum at the start of the electrolysis is
split, although the spectroelectrochemical measurements were car-
ried out at relatively low concentrations (1.00 Â 10À4 mol dmÀ3) as
absorption of all bands, occurred during the electrolysis of its solu-
tion in DMSO/TBAP at 0.98 V versus SCE, instead of the characteristic
spectral changes for this process (Fig. 6D). The UV–Vis spectra, mon-
itoredat thebeginningof bothits firstreduction(Fig. 6E)and thefirst
oxidation (Fig. 6F) of 10 in DCM/TBAP at suitable potentials are not
broad or split, suggesting clearly that it does not form aggregated
species in DCM/TBAP, as also implied by the cyclic voltammograms
recorded in this medium (Fig. 5C). The spectral changes in Figs. 6E
and F, the decrease in the Q-band absorption without shift and the
appearance of a new band within the range of 500–600 nm, are char-
acteristic for Pc-ring-based redox processes [41,42].
The cyclic and differential pulse voltammograms of 9 in DMSO/
TBAP are shown in Fig. 7A, which involves three reductions (R1,
R2 and R3) and an oxidation (O1) within the available potential
range. The comparison of the two cyclic voltammograms in
Fig. 7A suggests that the shape of the R1 couple is strongly affected
by the switching potential at the cathodic side. The R3 couple could
be monitored only by differential pulse voltammetry. The redox sig-
nals of 9 in DMSO/TBAP are split or broad which leads to ill-defined
voltammograms. This is probably due to the presence of aggregated
species. The aggregated species are expected to reduce or oxidize at
different potentials in comparison with the deaggregated species,
causing the splitting or broadening of the redox signals. The differ-
ence between the half-peak potentials of the first oxidation and
compared to that in voltammetric measurements (5.00 Â 10À4
-
mol dmÀ3). Therefore, it can be concluded that there is still aggrega-
tion–deaggregation equilibrium with the high energy band at
640 nm being due to the aggregate and the low energy band at
680 nm due to the monomer. Upon reduction at -0.80 V versus
SCE, the absorption of the aggregation band at 640 nm, decreases
while that of the monomer band at 680 nm increases with red shift
to 688 nm, as a first group of spectral changes (Fig. 6A). These spec-
tral changes, characteristic for Pc-ring reduction, are followed by a
decrease in the monomer band without shift and the formation of
a new band at 583 nm (Fig. 6B). The two groups of subsequent spec-
tral changes with different isosbestic points indicate clearly that
aggregation–deaggregation equilibrium shifts towards to monomer
species before the ligand-based first reduction process. The spectral
changes monitored during the second reduction process (R2) at
À1.30 V versus SCE, the decrease in the Q-band absorption and the
formation of a new band at 548 nm, correspond to the reduction of
singly-reduced monomer species (Fig. 6C). Although the O1 process
of 10 could be monitored with differential pulse voltammetry,
decomposition of the complex, evidenced by the decrease in the
reduction potentials,
DE1/2, of 9 is 0.76 V which is much lower in
comparison with that of 10. Thus, it is reduced and oxidized more
easily than 10. This distinctive behaviour of 9 can be attributed to
the fact that Co(II) center has accessible d orbital levels lying
Fig. 8. In situ UV–Vis spectral changes during controlled-potential electrolysis of 9 in DMSO /TBAP or DCM/TBAP.

S. Altun et al. / Polyhedron 48 (2012) 31–42
41
between the HOMO and the LUMO gap of the Pc species. In that case,
metal center can be oxidized and reduced before the ring-based re-
dox processes. This type of Pc complexes can vary their electro-
chemical behaviour according to their environment, depending on
whether there are any available coordinating species that would
stabilize the Co(II) center. The main difference lies in whether the
metal or the ring is oxidized first. Donor solvents strongly favour
Co(III)Pc(-2) by coordinating along the axis to form six coordinate
species. If such solvents are absent, then oxidation to Co(III) is inhib-
ited and ring oxidation occurs first. Thus, the first oxidation and the
first reduction processes of 9 in DMSO/TBAP are probably metal-
based and correspond to Co(II)Pc(-2)/[Co(III)Pc(-2)]+ and Co(II)Pc
(-2)/[Co(I)Pc(-2)]À redox couples, respectively. On the other hand,
it is also well known from the literature that the second reduction
process is ring-based [39]. The peak currents of the last reduction
couple are much higher than those of the other redox couples, as ob-
served also for 10. This behaviour implies that it corresponds to the
reduction of four oxy-coumarin substituents. Spectroelectrochemi-
cal measurements were also carried out to assign especially the first
reduction and the first oxidation processes of 9 certainly. Fig. 8A
shows in situ UV–Vis spectral changes during the first reduction of
9 at À0.80 V versus SCE, corresponding to the redox process labelled
R1 in Fig. 7A. The split Q-band absorption in the UV–Vis spectrum of
9 in DMSO/TBAP confirms the presence of aggregated species. The
band with higher energy corresponds to the aggregated species
while the one with lower energy is attributed to the deaggregated
species. Upon the first reduction, the absorptions of both bands de-
crease with red shift, while a new band appears at 475 nm. The new
Q-band is considerably broad, suggesting that some singly reduced
species are still aggregated after the first reduction process. The
spectral changes form various isosbestic points at different wave-
lengths within the ranges of 683–713 nm and 563–573 nm, rather
than the ones at specific wavelengths, due to the formation of differ-
ent reduced species produced from reduction of aggregated and
monomer species of 9. The band at 475 nm and the shifting of the
Q-band indicate the formation of [Co(I)Pc(-2)]À species, confirming
the CV assignment of the couple R1 to Co(II)Pc(À2)/[Co(I)Pc(À2)]À
process [36–39]. During the second reduction at À1.50 V versus
SCE, the higher energy side of the broad Q-band at 687 nm decreases
while its lower energy side increases, and thus two new bands ap-
pear at 645 and 702 nm. These spectral changes are associated by
increase in the absorption within the range of 436–625 and thus,
the formation of a band at 492 nm (Fig. 8B). The changes are charac-
teristics for a ring-based reduction in Co(II)Pc complex, and thus,
confirm our voltammetric assignment of this process to [Co(I)Pc
(-2)]À/[Co(I)Pc(-3)]2À. Fig. 8C displays in situ UV–Vis spectral
changes during the first oxidation process at 0.55 V versus SCE.
The absorptions of both peaks of the Q-band decrease and a Q-band
with the wavelength maximum of 637 nm and a new band at
456 nm appears. The new Q-band is considerably broad, suggesting
that some singly oxidized species are still aggregated after the first
oxidation process. The formation of a new band at 456 nm is typical
of a metal-based oxidation in CoPc complexes and thus, confirms
the CV assignment of Co(II)Pc(-2)/[Co(III)Pc(-2)]+ for couple O1 of
9 in Fig. 7A [43–46]. The tetra-substituted analogue of 9 did not
form aggregated species in DMSO/TBAP, as stated in a recent report
[37]. It appears that the increase in the number of peripheral oxy-
coumarin substituents increases the extent of cofacial interactions
between the neighbouring CoPc molecules, and thus, causes H-type
aggregation.
one oxidation couple in DMSO/TBAP within the available potential
ranges. Due to the non-coordinating nature of DCM, the first oxida-
tion processes of 9 (O1) is probably ligand-based and corresponds
to Co(II)Pc(-2)/[Co(II)Pc(-1)]+ couple while the second one (O2) is
metal-based and may be attributed to [Co(II)Pc(-1)]+/[Co(III)Pc
(-1)]2+ couple [39]. Fig. 8D displays the UV–Vis spectrum of 9 in
DCM/TBAP and in situ spectral changes during its first oxidation
at 1.05 V versus SCE. The solution of complex 9 in DCM/TBAP does
not involve aggregated species as understood clearly from the nar-
row and nonsplit Q-band at 671 nm in this figure. Upon the first
oxidation, the absorptions of the sharp Q band at 671 nm and the
vibrational band at 604 nm decreases without shift and two new
Q bands at 526 and 755 nm develops. These spectral changes are
characteristic for a Pc-based oxidation and thus, lead to the forma-
tion of [Co(II)Pc(-1)]+ species [41,42]. Unfortunately, the electroly-
sis of 9 at the potentials more positive than 1.10 V versus SCE in
DCM/TBAP resulted in decomposition of the complex, as evidenced
from decrease in the absorption of all peaks.
4. Conclusions
The novel metal-free Pcs 5, 8 and metal Pcs 6, 7, 9 and 10 have
been prepared from 4-chloro-5-(4-(4-methoxyphenyl)-8-methyl-
coumarin-7-yloxy)phthalonitrile (3) and 4,5-bis(4-(4-methoxy-
phenyl)-8-methylcoumarin-7-yloxy)phthalonitrile (4). The
compounds were characterized by UV–Vis, IR and MALDI-
TOF mass spectrometry, and elemental analysis. The effect of
substituent (the coumarin and chloro), metal (Co and Zn), solvent
(DMSO, DCM, toluene and chloroform) and concentration on the
spectroscopic properties and aggregation behaviour of the novel
compounds were investigated. The compounds displayed high
aggregation tendency in DMSO whereas their aggregated species
were not observed in DCM, toluene and chloroform. The
compounds 8–10 showed redox processes located at the ring
and/or metal centre. The aggregation character of the compounds
in DMSO was reflected by splitting or broadening of the redox
waves while the compounds displayed well-defined voltammo-
grams in DCM, due to the absence of aggregated species in this sol-
vent. Furthermore, the nature of the redox processes and the effect
of aggregation on the electron transfer processes were identified by
in situ spectroelectrochemical measurements during controlled-
potential electrolysis of the complexes at suitable potentials.
Acknowledgments
We are thankful to The Foundation of Marmara University,
The Commission of Scientific Research (BAPKO) (Project No:
FEN-A-090909-0302 and FEN-C-DRP-080410-0091) and Turkish
Academy of Sciences (TUBA).
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2012.08.080.
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