Synthesis and electrochemical properties of crown ether functionalized coumarin substituted cobalt and copper phthalocyanines

Article abstract of DOI:10.1016/j.jorganchem.2011.08.045

The synthesis of novel 6,7-[15-crown-5]-3-[p-(3,4-dicyanophenoxy)phenyl] coumarin (1)/6,7-[15-crown-5]-3-[p-(2,3-dicyanophenoxy)phenyl]coumarin (2) and their peripherally/non-peripherally cobalt and copper phthalocyanine complexes (3-6) have been prepared

Full text of DOI:10.1016/j.jorganchem.2011.08.045

Journal of Organometallic Chemistry 696 (2011) 3873e3881
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and electrochemical properties of crown ether functionalized coumarin
substituted cobalt and copper phthalocyanines
,
Aliye Aslı Esenpınara, Ali Rıza Özkayab, Mustafa Bulutb
*
a Kırklareli University, Department of Chemistry, 39100, Kırklareli, Turkey
b Marmara University, Faculty of Art and Science, Department of Chemistry, Kadikoy 34722, Istanbul, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of novel 6,7-[15-crown-5]-3-[p-(3,4-dicyanophenoxy)phenyl]coumarin (1)/6,7-[15-crown-
5]-3-[p-(2,3-dicyanophenoxy)phenyl]coumarin (2) and their peripherally/non-peripherally cobalt and
copper phthalocyanine complexes (3e6) have been prepared and characterized by elementel analysis,
1H-NMR, MALDI-TOF, FT-IR and UVeVis spectral data. Fluorescence intensity changes of compound 1 and
2 have been determined by addition of Naþ or Kþ ions at 25 ꢀC in THF. The effect of substitution type on
the redox and aggregation behaviour of the compounds was investigated by voltammetry and in situ
spectroelectrochemistry.
Received 25 July 2011
Received in revised form
26 August 2011
Accepted 31 August 2011
Keywords:
Coumarin (2H-chromen-2-one)
Crown ether
Ó 2011 Elsevier B.V. All rights reserved.
Phthalocyanine
Fluorescence
Electrochemistry
1. Introduction
important effects in plant biochemistry and physiology, acting as
antioxidants, enzyme inhibitors and precursors of toxic substances.
Since their synthesis in the early 1930, phthalocyanines (Pcs) are
known as excellent functional materials. Metallophthalocyanines
(MPcs) have attracted a great deal of interest due to their high
colouring property, extremely high thermal stability, chemical
resistivity, electrical conductivity, photoconductivity and catalytic
activity [1,2]. They have been studied in details for many years,
especially with regard to their properties as pigments for printing
inks, plastics [3] and in paints and coatings. Nowadays there is
renewed interest in phthalocyanine chemistry, as Pcs and many of
their derivatives exhibit noteworthy properties for applications in
material science [4]. For example, Pcs are used in laser-beam
printers and photocopiers [5,6], in nonlinear optics [7,8], as liquid
crystals [9e11], as electrochromic substances [12], as carrier
generation materials in near infrared (NIR) [13] and Langmuire
Blodgett films [14]. Many substituted derivatives of Pcs behave like
active components in various redox processes, for example, in
photoredox reactions and photooxidations in solution [15,16] and
for photodynamic cancer therapy (PDT) [17e19].
In addition, these compounds are involved in the actions of plant
growth hormones and growth regulators, the control of respiration,
photosynthesis, as well as defense against infection [20]. They have
long been recognized to possess anti-inflammatory, antioxidant,
antiallergic, hepatoprotective, antithrombotic, antiviral, and anti-
carcinogenic activities. The hydroxycoumarins are typical phenolic
compounds and therefore, act as potent metal chelators and free
radical scavengers [20e22].
The crown ethers are multidentate macrocyclic compounds, so
called because of their appearance of space-filling models and
their ability to “crown” cations. Their characteristic properties are
the ability to solubilize inorganic compounds in organic solvents,
and thus increase the range of their reactivities. The size of the
cavity available in each crown ether varies and determines the
type of cation which is bound most efficiently. Crown ether
substituted phthalocyanines, which show a high tendency towards
aggregation by polar protic solvents such as DMSO (dime-
thylsulfoxide) and DMF (dimethylformamide), i.e. and cations have
been described [23]. They can be used for the colorimetric deter-
mination of alkali cations [24] as selective extracting reagents
[25,26] and liquid crystals [27]. It has been proved that they are
capable of forming ion channels and transport ions by arranging
the pendant crown ether rings in stacks [28]. The main feature of
the crown ether groups is that they can hold the alkali cations
within their cavity. We have preferred these groups as substituent
On the other hand, coumarins comprise a group of natural
compounds found in a variety of plant sources. Coumarins have
* Corresponding author. Tel.: þ90 216 3479641/1370; fax: þ90 216 3478783.
E-mail
addresses:
mbulut@marmara.edu.tr,
mustafabulut50@gmail.com
(M. Bulut).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.08.045

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A.A. Esenpınar et al. / Journal of Organometallic Chemistry 696 (2011) 3873e3881
on the Pc ring; we think that they can penetrate easily into the cell
for PDT activation.
The combined organic extracts were washed with water, dried
over CaCl2 and evaporated in vacuum. Column chromatography
of the crude products (silica gel 60, Merck) with chloroform
gave pure chromenone crown ether. The compound is soluble
in ethanol, methanol, THF, CHCl3, CH2Cl2, DMF and DMSO.
Due to intermolecular interactions between the macrocycles,
peripherally unsubstituted metallophthalocyanines are practically
insoluble in common organic solvents, thereby minimizing their
usefulness in applications. The solubility of phthalocyanines can be
improved by introducing substituents on the periphery that
increase the distance between the planar macrocycle rings carrying
Yield: 0.215 g (17%). M.p.: 205e208 ꢀC. IR
n
(cmꢂ1): 3073
(AreCH), 2930e2862 (aliphatic CH), 2231 (C^N), 1708 (C]O),
1614e1573 (Ar C]C), 1250 (AreOeAr). 1H-NMR (DMSO-d6,
the
p
-electrons and making solvation easier. Starting compounds
500 MHz, d ppm): 7.13 (s, 1H, AreH1), 7.07 (s, 1H, AreH2), 8.32 (s,
have formed from simple mono-functional substituents such as,
diazatrioxa-, diazadioxa- and tetraaza-crown ether double layers
have been introduced onto the periphery of the phthalocyanine
nucleus [29]. These structures are capable of binding alkali metal
ions and provide donor sites for binding transition metal ions,
leading to homo- and heteronuclear complexes [30].
The understanding 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. However, it is not possible to
distinguish such processes by voltammetry alone. In situ spec-
troelectrochemistry provide additional support for the assignment
of these redox processes. Moreover, spectroelectrochemical
studies of Pcs are also important in identifying the effect of
aggregation-disaggregation equilibrium of Pcs on their redox
behaviour. Therefore, we also investigate the electrochemical and
in situ spectroelectrochemical behaviour of the synthesized Pc
complexes.
1H, lactone-H3), 7.86 (d, J ¼ 8 Hz, 2H, AreH4), 7.32 (d, J ¼ 8 Hz, 2H,
AreH5), 8.21 (s, J ¼ 8 Hz, 1H, AreH6), 7.47 (d, 1H, AreH7), 8.14 (d,
J ¼ 8 Hz, 1H, AreH8), 4.11 (m, 4H, OCH2), 3.83 (m, 4H, OCH2), 3.65
(m, 8H, OCH2). UVeVis lmax (nm) (log
3
) (THF) (1 ꢁ10ꢂ5 M): 364
(4.20), 307 (3.94). Anal. calcd. for C31H26N2O8: C 67.14; H 4.73; N
5.05%. Found: C 66.12; H 5.12; N 5.01%. MS (MALDI-TOF): m/z 554
[M]þ.
2.3.2. 6,7-[15-Crown-5]-3-[p-(2,3-dicyanophenoxy)phenyl]couma-
rin (2)
6,7-Dihydroxy-3-[p-(2,3-dicyanophenoxy)phenyl]coumarin
(1.00 g, 2.5 mmol) and tetra ethyleneglycolditosylate (1.26 g,
2.5 mmol) were dissolved in dry CH3CN (150 mL) under
nitrogen atmosphere and anhydrous Na2CO3 (0.53 g, 5 mmol)
was added. After stirring for 7 days at 85e90 ꢀC, the solvent was
evaporated in vacuum. %37 HCl (1 ꢁ10ꢂ6 M) was added to the
residue and the mixture was extracted with CHCl3 (4 ꢁ 30 mL).
The combined organic extracts were washed with water, dried
over CaCl2 and evaporated in vacuum. Column chromatography
of the crude products (silica gel 60, Merck) with chloroform
gave pure chromenone crown ether. The compound is soluble in
ethanol, methanol, THF, CHCl3, CH2Cl2, DMF and DMSO.
2. Experimental
2.1. Materials
Yield: 0.215 g (17%). M.p.: 218e220 ꢀC. IR
n
(cmꢂ1): 3081
Acetonitrile, tetra ethyleneglycolditosylate, N,N-dimethylami-
noethanol (DMAE), sodium carbonate, calcium chloride, anhydrous
cobalt acetate, anhydrous copper acetate were purchased from
Acros. DMSO and DMF were dried as described by Perrin and
Armarego [31] before use. Methanol, n-hexane, chloroform,
dichloromethane, tetrahydrofuran (THF), acetone and ethanol
(AreCH), 2961e2869 (aliphatic CH), 2233 (C^N), 1710 (C]O),
1614e1570 (Ar C]C), 1281 (AreOeAr). 1H-NMR (DMSO-d6,
500 MHz,
d ppm): 7.13 (s, 1H, AreH1), 7.07 (s, 1H, AreH2), 8.21 (s,
1H, lactone-H3), 8.14 (d, J ¼ 8 Hz, 2H, AreH4), 7.34 (d, J ¼ 8 Hz, 2H,
AreH5), 7.47 (d, J ¼ 8 Hz, 1H, AreH6), 7.88 (t, 1H, AreH7), 7.41 (d,
J ¼ 8 Hz, 1H, AreH8), 4.11 (m, 4H, OCH2), 3.83 (m, 4H, OCH2), 3.38
were
freshly
distilled.
4-Nitrophthalonitrile
[32],
3-
(m, 8H, OCH2). UVeVis lmax (nm) (log
3
) (THF) (1 ꢁ10ꢂ5 M): 362
nitrophthalonitrile [33], 6,7-dihydroxy-3-[p-(30-40-dicyanophe-
noxy)phenyl]coumarin and 6,7-dihydroksy-3-[p-(20-30-dicyano-
phenoxy)phenyl]-coumar-in [34,35] were synthesized according to
reported procedures.
(4.40), 316 (4.18). Anal. calcd. for C31H26N2O8: C 67.14; H 4.73; N
5.05%. Found: C 66.12; H 5.12; N 5.01%. MS (MALDI-TOF): m/z 554
[M]þ.
2.3.3. 2,9 (10),16 (17),23 (24)-Tetrakis[6,7-(15-crown-5)-3-(4-oxy-
phenyl)coumarin]-phthalocyaninato cobalt and copper complexes
(3) and (4)
2.2. Equipment
The IR spectra were recorded on a Shimadzu Fourier Transform
FTIR-8300 using KBr pellets. Mass spectra were performed on
a Bruker Daltonic Autoflex III MALDI-TOF spectrometer. Absorption
spectra in the UVeVisible region were recorded with a Shimadzu
UV-1601 spectrophotometers. Fluorescence excitation and emis-
sion spectra were recorded on a HITACHI F-7000 spectrofluorom-
eter using 1 cm pathlength cuvettes at room temperature.
6,7-[15-Crown-5]-3-[p-(3,4-dicyanophenoxy)phenyl]coumarin
(1) (0.1 g, 0.18 mmol) Co(AcO)2 (0.011 g, 0.045 mmol)/Cu(AcO)2
(0.007 g, 0.040 mmol) and dry DMAE (2 mL) were refluxed with
stirring under N2 atmosphere for 24 h. After cooling to room
temperature, the reaction mixture was treated with methanol
and then the solid product was filtered off and washed with
water, methanol, ethanol, acetonitrile, ethyl acetate, acetone,
acetic acid and diethyl ether. The compound is soluble in DMF
and DMSO.
2.3. Synthesis
Compound 3: yield: 0.035 g (34%), M.p.: >300 ꢀC. IR
3042 (AreH), 2918e2868 (alkyl-CH), 1715 (C]O lactone),
n
(cmꢂ1):
2.3.1. 6,7-[15-Crown-5]-3-[p-(3,4-dicyanophenoxy)phenyl]couma-
rin (1)
1614e1566 (C]C), 1234 (AreOeAr). UVeVis lmax (nm) (log )
3
6,7-Dihydroxy-3-[p-(3,4-dicyanophenoxy)phenyl]coumarin
(1.0 g, 2.5 mmol) and tetra ethyleneglycolditosylate (1.26 g,
2.5 mmol) were dissolved in dry CH3CN (150 mL) under
nitrogen atmosphere and anhydrous Na2CO3 (0.53 g, 5 mmol)
was added. After stirring for 7 days at 85e90 ꢀC, the solvent was
evaporated in vacuum. %37 HCl (1 ꢁ10ꢂ6 M) was added to the
residue and the mixture was extracted with CHCl3 (4 ꢁ 30 mL).
(DMF) (1.3 ꢁ10ꢂ5 M): 362 (4.88), 665 (4.78). MS (MALDI-TOF), 2,5-
dihydroxybenzoic acid as matrix: m/z 2275 [M þ 1]þ.
Compound 4: Yield: 0.045 g (48%), M.p.: >300 ꢀC. IR (cmꢂ1):
n
3100e3074 (AreH), 2958e2865 (alkyl-CH), 1714 (C]O lactone),
1613e1567 (C]C), 1233 (AreOeAr). UVeVis lmax (nm) (log )
3
(DMF) (1.3 ꢁ 10ꢂ5 M): 362 (5.02), 677 (4.30). MS (MALDI-TOF), 2,5-
dihydroxybenzoic acid as matrix: m/z 2280 [M þ 1]þ.

A.A. Esenpınar et al. / Journal of Organometallic Chemistry 696 (2011) 3873e3881
3875
2.3.4. 1,8(11),15(18),22(25)-Tetrakis[6,7-(15-crown-5)-3-(4-
2.4. Electrochemistry and in situ spectroelecrochemistry
oxyphenyl)coumarin]-phthalocyaninato cobalt and copper
complexes (5) and (6)
The cyclic and differential pulse voltammetry measurements
were carried out with a PAR VersoStat II Model potentiostat/
galvanostat 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. The surface of the
working electrode was polished with H2O suspension of Al2O3
before each run. The last polishing was done with a particle size
of 50 nm. 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 was employed as the supporting electrolyte
at a concentration of 0.10 mol dmꢂ3. 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 measurements. In situ
spectroelectrochemical measurements were carried out by an
Agilent Model 8453 diode array spectrophotometer equipped
with the potentiostat/galvanostat and utilizing an optically
transparent thin layer (OTTLE) cell with three-electrode
6,7-[15-Crown-5]-3-[p-(2,3-dicyanophenoxy)phenyl]couma-
rin (2) (0.1 g, 0.18 mmol) Co(AcO)2 (0.01 g, 0.040 mmol)/Cu(AcO)2
(0.007 g, 0.040 mmol) and dry DMAE (2 mL) were refluxed with
stirring under N2 atmosphere for 24 h. After cooling to room
temperature, the reaction mixture was treated with methanol and
then the solid product was filtered off and washed with water,
methanol, ethanol, acetonitrile, ethyl acetate, acetone, acetic acid
and diethyl ether. The compound is soluble in DMF and DMSO.
Compound 5: Yield: 0.043 g (47%), M.p.: >300 ꢀC. IR
3100e3053 (AreH), 2980e2865 (alkyl-CH), 1713 (C]O lactone),
n
(cmꢂ1):
1613e1574 (C]C), 1248 (AreOeAr). UVeVis lmax (nm) (log ) (DMF)
3
(1.3 ꢁ 10ꢂ5 M): 360 (4.98), 681 (4.76). MS (MALDI-TOF), 2,5-
dihydroxybenzoic acid as matrix: m/z 2275 [M þ 1]þ.
Compound 6: Yield: 0.052 g (51%), M.p.: >300 ꢀC. IR (cmꢂ1):
n
3112e3058 (AreH), 2992e2867 (alkyl-CH), 1714 (C]O lactone),
1613e1572 (C]C), 1249 (AreOeAr). UVeVis lmax (nm) (log )
3
(DMF) (1.3 ꢁ 10ꢂ5 M): 363 (4.86), 695 (4.64). MS (MALDI-TOF), 2,5-
dihydroxybenzoic acid as matrix: m/z 2280 [M þ 1]þ.
HO
HO
O O
HO
HO
O O
CN
O
CN
CN
O
CN
6,7-Dihydroxy-3-[p-(3,4-dicyanophenoxy)phenyl]coumarin
6,7-Dihydroxy-3-[p-(2,3-dicyanophenoxy)phenyl]coumarin
TsO
O
O
O
OTs
TsO
O
O
O
OTs
2Na2CO3
CH3CN
7 days
2Na2CO3
CH3CN
7 days
85-90 0 C
85-90 0 C
10
10
9
1
O
O
11 O
11
O
O
O
10
10
11
9
4
1
O
O
5
11 O
O
O
O
2
O
2
8
9
11
O
CN
CN
5
11
O
3
1
CN
9
11
6
O
CN
7
3
1600
24h Reflux
C
DMAE
2
8
6
7
Metal salts
1600 C
DMAE
Metal salts
24h Reflux
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
N
N
O
O
O
O
O O
O
N
N
M
O
N
N
N
O
N
N
N
N
M
O
N
N
O
O
O
O
N
N
N
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
M: Co (5), Cu (6)
M: Co (3), Cu (4)
Scheme 1. Synthesis route of the 6,7-[15-crown-4-ether-3-[p-(3,4-dicyanophenoxy)phenyl]coumarin (1)/6,7-[15-crown-4-ether-3-[p-(2,3-dicyanophenoxy)phenyl]coumarin (2)
and the chromenone crown ether substituted cobalt/copper phthalocyanine complexes (3e6).

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A.A. Esenpınar et al. / Journal of Organometallic Chemistry 696 (2011) 3873e3881
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.
The 1H-NMR spectra of 1/2 in DMSO-d6 show the expected peak
resonances and peak integrals due to the protons of chromenone
crown ether derivative. The 1H-NMR spectra of 1/2 showed char-
acteristic signals for ether protons (eOeCH2eCH2eOe) at
d
3.65e4.11 ppm/at
d 3.38e4.11 ppm each as multiplet. The singlet
peaks at 8.32 ppm/8.21 ppm indicates the presence of lacton
d
3. Results and discussion
proton at the 4-position of coumarin moiety. In addition; the
chemical shifts of the aromatic protons are observed at range of
7.13e8.21 ppm/7.07e8.14 ppm.
3.1. Synthesis and characterization
The mass spectra of newly synthesized compounds (1 and 2)
confirmed the proposed structure. The mass spectral studies by the
MALDI-TOF technique on the synthesized compounds identified at
m/z: 554 [M]þ for 1 (Fig. 1).
The novel compounds (1e6) show good solubility in solvents
such as DMF, DMSO and they have been characterized by elemental
analysis (1 and 2), FT-IR, 1H-NMR (1 and 2), UVeVis and MALDI-MS
spectroscopy.
6,7-Dihydroxy-3-[p-(3,4-dicyanophenoxy)phenyl]
The UVeVis spectra of cobalt (II)/copper (II) Pc complexes (3/
4e5/6) showed characteristic absorptions in the Q band region at
665 nm/677 nme681 nm/695 nm and the B band region was
observed at around w362 nm in DMSO. The spectrum showed
monomeric behaviour evidenced by a single (narrow) Q band in the
visible region which is typical for metallated phthalocyanine
complexes [36].
With the aim of assessing the effect of alkali cations on the
fluorescence intensity of the crown ether functionalized coumarin
ligand by spectral methods, alkali metal salt (NaSCN or KSCN)
solutions were added to compound 1/2 solution in THF. To avoid
any effect arising from dilution due to the addition of the metal salt
to the ligand solution, the compound 1/2 and metal salts were
prepared at concentrations of 1233 ꢁ10ꢂ5 M for NaSCN and
1029 ꢁ 10ꢂ5 M for KSCN in EtOH, respectively. However, the addi-
tion of NaSCN and KSCN to the compound 1/2 solutions caused
decreasing of the fluorescence intensity of these compounds indi-
cate that the entrance of the Naþ or Kþ cations in the crown ether
cavitiy (Fig. 2). The decreasing of the fluorescence intensity is
coumarin/6,7-dihydroxy-3-[p-(2,3-dicyanophenoxy)phenyl]coumarin
were reacted with tetraethylenglycol ditosylate in the presence of
Na2CO3 in dry CH3CN to give the compound 1/2 in 17% yield. The
crude products were purified by column chromatography over
silica gel using CHCl3 as eluent (Scheme 1). The peripherally 2,9
(10),16 (17),23 (24)-tetrakis[6,7-(15-crown-5)-3-(4-oxyphenyl)
coumarin]phthalocyaninatocobalt and copper complexes (3) and
(4)/the non-peripherally 1,8(11),15(18),22(25)-tetrakis[6,7-(15-
crown-5)-3-(4-oxyphenyl)coumarin]-phthalocyaninatocobalt and
copper complexes (5) and (6) have been prepared by cyclotetra-
merization of the novel 6,7-[15-crown-5]-3-[p-(3,4-dicyanophenoxy)
phenyl] coumarin (1)/6,7-[15-crown-5]-3-[p-(2,3-dicyanophenoxy)
phenyl]coumarin in w50% yield.
The FT-IR spectra of 1/2 showed two vibration peaks at ca. 2862
and 2930 cmꢂ1/2869 and 2961 cmꢂ1 for their CeH stretching
frequency. The characteristic vibration peaks of the carbonyl group
(C]O) and benzene ring were observed in the region 1708 cmꢂ1
/
1710 cmꢂ1 and 1578e1614 cmꢂ1/1570e1614 cmꢂ1
One vibration peak was appeared in the range 1250 cmꢂ1
, respectively.
/
1281 cmꢂ1 corresponding to C-O-C ether chain. Cyclo-
tetramerization of the dinitril compounds to the cobalt (II) and
copper (II) Pc complexes (3e6) was confirmed by the disappear-
ance of the sharp wC^N vibration at 2231 cmꢂ1/2233 cmꢂ1. The IR
spectra of 3e4/5e6 showed vibration peaks at ca. 3042 cmꢂ1 (3)e
3100e3074 cmꢂ1 (4)/3100e3053 cmꢂ1 (5)e3112e3058 cmꢂ1 (6)
for aromatic CeH stretching, at 2918e2868 cmꢂ1 (3)e
2958e2865 cmꢂ1 (4)/at 2980e2865 cmꢂ1 (5) 2992e2867 cmꢂ1 (6)
for their aliphatic CeH stretching frequency. The characteristic
vibration peaks of the carbonyl group (C]O) and C]C bonds at
benzene rings were appeared in the region at w1714 cmꢂ1 and at
1614e1566 cmꢂ1 for 3, at 1613e1567 for 4, at 1613e1574 for 5, at
1613e1572 for 6 respectively. One vibration peak was also appeared
in the range at 1233 cmꢂ1 for 3, 1234 cmꢂ1 for 4, 1248 cmꢂ1 for 5,
1249 cmꢂ1 for 6 corresponding to CeOeC ether chain.
Fig. 1. The positive ion and linear mode MALDI-TOF MS spectrum of 1 ([M þ Na]þ
:
Fig. 2. The effect of alkali cations on the fluorescence intensity of the compound 1 by
spectral methods, (a) during the gradual addition of NaSCN and (b) KSCN for 1 in THF.
577 Da).

A.A. Esenpınar et al. / Journal of Organometallic Chemistry 696 (2011) 3873e3881
3877
Table 1
Voltammetric data on Pt in DMSO/TBAP for 3e6.
Complex
Ring oxidations
MII/MIII
MII/MI
Ring reductionsd
DE1/2
3 (
4 (
5 (
6 (
b-CoPc)
b-CuPc)
a-CoPc)
a-CuPc)
E1/2 (V)a
D
0.39
0.060
ꢂ0.38
ꢂ1.30
0.100
ꢂ0.73
0.080
ꢂ1.33
0.070
ꢂ0.73
0.060
0.77
Ep (V)b
0.060
E1/2 (V)a
Ep (V)b
E1/2 (V)a
Ep (V)b
E1/2 (V)a
Ep (V)b
ꢂ1.08
ꢂ1.64
D
0.100
0.100
0.40
0.060
ꢂ0.37
0.77
1.01
D
0.060
0.28c
0.200
ꢂ1.33
D
0.080
a
E1/2 ¼ (EpaþEpc)/2 at 0.025 V sꢂ1
.
b
c
ΔEp ¼ Epa þ Epc at 0.025 V sꢂ1
.
The first oxidation couple of 6 (a-CuPc) is observed at less positive potentials than those of Cu(II) phthalocyanines in literature [37], probably due to the adsorption of 6 on
the platinum working electrode.
d
D
E1/2 ¼ E1/2 (first oxidation) ꢂ E1/2 (first reduction). This value corresponds to the HOMOeLUMO gap for metallophthalocyanines having electro-inactive metal center, but
it represents metal to ligand (MLCT) or ligand to metal (LMCT) charge transfer transition gap for metallophthalocyanines having redox active metal center.
higher for addition of Naþ cation than Kþ because the size of the
Naþ ion is more suitable for the cavity of 15-crown-5 than the size
of Kþ cation.
at 683 with lower energy. The aggregation of Pc molecules is
usually as a coplanar association, which results mainly from the
pep* interactions between the p electron clouds of adjacent Pc
macrocycles [38]. Some functional groups in Pc molecules also
enable aggregation, which results from additional specific inter-
actions such as hydrogen bonding in Pcs containing carboxylic
3.2. Electrochemistry
Voltammetry and in situ spectroelectrochemistry of the
complexes were carried out in de-aerated DMSO containing TBAP.
The voltammetric data of 3e6, including the half-wave redox
potential value vs. SCE (E1/2), anodic-to-cathodic peak potential
separation (
reduction potential (
D
Ep) and the difference between the first oxidation and
E1/2) are listed in Table 1. The number of
D
electrons transferred is unity for all redox processes. Anyway, in
monophthalocyanines, multi-electron processes occurring in one
step are not common. The ratio of anodic to cathodic peak currents
for the redox couples were usually near unity and anodic to
cathodic peak separation
oxidation couple of 6), thus suggesting reversible to quasi-
reversible behaviour (
E of 80 mV at 0.025 V sꢂ1 was obtained for
DEp ranged 60e100 mV (except the
D
the ferrocene internal standard).
Fig. 3A shows typical cyclic voltammogram of beta-substituted
CuPc, 4 at 0.025 V sꢂ1 scan rate in DMSO/TBAP. It displays three
reduction couples (R1eR3). It is clear from the well-known elec-
trochemistry of metallophthalocyanines that Cu(II) at the center of
Pc core is redox-inactive and thus, these reduction couples are Pc
ligand-based [37]. As shown in Fig. 3A, the cathodic component of
the first reduction couple, R1 is split into two peaks. This splitting
implies that the electron transfer process is associated by aggre-
gationedisaggregation equilibrium of
4 species. Spectroelec-
trochemical measurements in solution have a vital importance, not
only in confirming the assignment of the redox processes but also
in identifying the effect of aggregation phenomenon on the redox
processes. Thus, in situ spectroelectrochemistry of 4 during the
electrolysis of its solution in TBAP/DMSO at a potential slightly
more negative than that of R1c peak was employed to provide
support for the coupling of its electron transfer process by aggre-
gationedisaggregation equilibrium. The concentration of the
complexes was w5.00 ꢁ 10ꢂ5 mol dmꢂ3 in DMSO/TBAP for studies
in OTTLE cell. In situ UVeVis spectral changes during the first
reduction process of 4 at ꢂ0.85 V versus SCE are shown in Fig. 3B.
Aggregation in MPc complexes is typified by a broadened or split Q
band, with the high energy band being due to the aggregate and the
low energy band due to the monomer. Thus, the spectrum at the
start of electrolysis indicates the presence of an equilibrium
between the aggregated and monomer species, as judged by the
splitting of Q band. It is clearly seen that the absorption of the band
at 615 nm with higher energy dominates as compared to that of one
Fig. 3. (A) Cyclic voltammograms of 2.5 ꢁ10ꢂ4 mol dmꢂ3 4 in TBAP/DMSO. (B) In situ
UVeVis spectral changes during the controlled potential electrolysis of 4.

3878
A.A. Esenpınar et al. / Journal of Organometallic Chemistry 696 (2011) 3873e3881
groups [39], ester [40] or alkylamid [41]. The coumarins can also
build aggregation at carboxyl groups. On the other hand, the
lactone carbonyl of coumarins can coordinate metal cations such as
Cu2þ, Mn2þ, Ni2þ, Co2þ [42]. Upon first reduction at ꢂ0.85 V vs. SCE,
the absorption of the all bands decreases while the absorption
between 485 and 585 nm increases and a new band at 541 nm
forms. Thus, isosbestic points are observed at 482 and 586 nm. The
new band at 541 nm and the decrease in the Q band absorption
without shift are characteristic for Pc ring reduction [43,44]. The
formation of isosbestic points at various wavelengths between 570
and 595 nm rather than at a specific wavelength implies that the
reduction of both aggregated and monomer species occurs during
the first reduction at ꢂ0.85 V versus SCE, and provide support for
the presence of equilibrium between the aggregated and monomer
species at the beginning. Fig. 4A and B displays cyclic and differ-
ential pulse voltammograms of alpha-substituted CuPc, 6. The
redox behaviour of 6 at the cathodic side is similar to that of 4.
However, the first reduction peak of 6 is not split and the second
reduction of 6 occurs at more negative potentials than that of 4.
Furthermore, on the contrary of 4, the first oxidation process of 6
can be observed, probably due to its high adsorption tendency on
the platinum working electrode. Normally, this redox process is
observed at relatively more positive potentials or cannot be
observed within the available positive potential window. The peak
current of the first oxidation process is much higher than those of
other reduction processes. In addition, it is directly proportional to
the scan rate at low scan rates. These observations provide strong
support for high adsorption tendency of 6. High adsorption
tendency of copper phthalocyanines on platinum electrode was
also reported previously by other studies [45e47]. Fig.4C displays
in situ UVeVis spectral changes monitored during the first reduc-
tion of 6 at ꢂ1.00 V vs. SCE in DMSO/TBAP. The unsplit and sharp
Q-band absorption in the original spectrum monitored before the
electrolysis shows that, on the contrary of 4, the solution of 6 does
not involve aggregated species. The absence of aggregated species
in solutions of 6 in DMSO/TBAP may be attributed to the non-
peripheral nature of alpha-substitution. It has been well estab-
lished that nonaggregated Pcs are extremely important for their
various applications [48e52]. The spectral changes in Fig.4C are
characteristic for Pc ligand-based reduction with the decrease in
the Q-band adsorption without shift and appearance of a new band
between 500e600 nm [43,44].
which implies that the electron transfer process is associated by
aggregationedisaggregation equilibrium of 3 species. In situ spec-
troelectrochemical measurements in TBAP/DMSO provided strong
support for both the assignment of the redox processes of 3 and
the coupling of its electron transfer processes by
Fig. 5 shows the cyclic and differential pulse voltammograms of 3
in DMSO/TBAP. The redox potentials of 3 are considerably different
in comparisonwith those of 4 and 6 (Table 1). The first reduction of 3
occurs at a potential less negative (ꢂ0.38 V vs. SCE) than those of 4
and 6 (ꢂ0.73 V vs. SCE). This difference in the voltammetric behav-
iour is due to the fact that MPcs, such as MnPc, CoPc and FePc, having
a metal that possesses energy levels lying between the HOMO and
the LUMO of the Pc ligand, in general exhibit redox processes cen-
tred on the metal [37,53e57]. For CoPc complexes, the first oxidation
and first reduction processes usually occur on the metal center in
polar solvents such as DMF and DMSO. However the first oxidation
process usually occurs on the Pc ring in nonpolar solvents such as
DCM and THF. Therefore, the first reduction (R1) and the first
oxidation (O1) processes of 3 may be assigned to the [Co(II)Pc(-2)]/
[Co(I)Pc(-2)]ꢂ and [Co(II)Pc(-2)]/[Co(III)Pc(-2)]þ redox couples,
respectively. The second reduction process (R2) is probably ligand-
based and can be assigned to [Co(I)Pc(-2)]ꢂ/[Co(I)Pc(-3)]2ꢂ [37].
The separation between the first oxidation and the first reduction
potentials of the metal center for the Co(II) complex, 3 (0.77 V) is
comparable with the relevant values in the literature [37,53e57],
and does not reflect the HOMO-LUMO gap. As shown in Fig. 5, the
anodic component of the first reduction couple, R1 and the cathodic
component of the second reduction couple are split into two peaks,
Fig. 4. (A) Cyclic and (B) differential pulse voltammograms of 2.5 ꢁ10ꢂ4 mol dmꢂ3 6 in
TBAP/DMSO. (C) In situ UVeVis spectral changes during the controlled potential
electrolysis of 6.

A.A. Esenpınar et al. / Journal of Organometallic Chemistry 696 (2011) 3873e3881
3879
3.0
A
The first reduction, R1
2.5
2.0
1.5
1.0
0.5
0.0
400
500
600 700
Wavelength/nm
800
900
3.0
2.5
2.0
1.5
1.0
0.5
0.0
B
The second reduction, R2
400
500
600 700
Wavelength/nm
800
900
3.0
2.5
2.0
1.5
1.0
0.5
0.0
C
The first oxidation, O1
Fig. 5. Cyclic (A) and differential pulse (B) voltammograms of 2.5 ꢁ10ꢂ4 mol dmꢂ3 3 in
TBAP/DMSO.
aggregationedisaggregation equilibrium. Fig. 6A represents in situ
UVeVis spectral changes during the first reduction of 3 at ꢂ0.75 V vs.
SCE corresponding to the redox process labeled R1. The concentra-
tion of the complexes was w5.00 ꢁ 10ꢂ5 mol dmꢂ3 in DMSO/TBAP
for studies in OTTLE cell. The spectrum at the start of electrolysis
indicates the presence of an equilibrium between the aggregated
and monomer species, as judged by remarkably broad Q-band
absorption. The broad Q-band at 663 nm decreases and shifts
670 nm, while a new band at 705 nm appears. At the same time, the
B band shifts from 388 to 410 nm. The red shifting of the Q-band and
the formation of a new band at 705 nm indicate the formation of
[Co(I)Pc(-2)]ꢂ species, confirming the voltammetric assignment of
the couple R1 to Co(II)Pc(-2)/[Co(I)Pc(-2)]ꢂ process [58,59].
However, the Q-band obtained after the first reduction process is
still broad and the accompanied spectral changes don’t have well-
defined isosbestic points at specific wavelengths. Furthermore, the
characteristic Co(I)Pc(-2) band around 475 nm could not be
observed clearly although the absorption within the range of
450e500 nm increased. All these observations imply that the
species obtained upon the reduction of aggregated species probably
do not disaggregate after the first reduction process and thus, there
is also equilibrium between aggregated and monomeric forms of
mono-reduced species. During the second reduction, the Q band
400
500
600
Wavelength/nm
700
800
900
Fig. 6. In situ UVeVis spectral changes during the controlled potential electrolysis of 3
upon (A) the first reduction at ꢂ0.75 V vs. SCE, (B) the second reduction at ꢂ1.50 V vs.
SCE and (C) the first oxidation at 0.80 V vs. SCE in TBAP/DMSO.
decreases slightly without shift (Fig. 6B) and the absorption within
the range of 500e600 nm increases. These spectral changes at the
potential of the couple R2 are characteristic for a ring-based second
reduction in Co(II)Pc complex, [Co(I)Pc(-2)]ꢂ/[Co(I)Pc(-3)]2ꢂ. The Q-
band is still broad, suggesting the presence of doubly reduced
aggregated species. Fig. 6C displays in situ UVeVis spectral changes
during the first oxidation process. The broad Q band at 663 nm
increases in intensity with red shift to 676 nm and becomes sharp. At

3880
A.A. Esenpınar et al. / Journal of Organometallic Chemistry 696 (2011) 3873e3881
the same time, the B bands decrease. The increase of the Q band with
red shift is typical of a metal-based oxidation in CoPc complexes
[58e63], and thus confirms the voltammetric assignment of Co(II)
Pc(-2)/[Co(III)Pc(-2)]þ for couple O1 of 5. In addition, the formation
of a sharp Q-band after the first oxidation process implies that
mono-oxidized species are not aggregated, i.e., disaggregation
occurs immediately after the oxidation of aggregated species.
Fig. 7 shows cyclic and differential pulse voltammograms of
alpha-substituted CoPc 5. The redox potentials of beta-substituted
CoPc, 3 and alpha-substituted CoPc, 5 are very similar to each
other with small shifts. However, on the contrary of the reduction
couples of 3, those of 5 are not split due to the absence of aggre-
gated species. It is known that the shape of the alpha-substituted Pc
molecules deviate from planarity, which should be responsible for
the absence of aggregated species since aggregation usually results
from the
pep* interactions between the p electron clouds of
adjacent Pc macrocycles [38]. Fig. 8A and B displays in situ UVeVis
spectral changes during the first reduction and the first oxidation
processes of 5 at suitable potentials, respectively. The spectrum at
the start of the electrolysis in Fig. 8A or B indicates the absence of
aggregated species, as judged by relatively sharper Q-absorption
band at 680 nm, in comparison with the corresponding one for 3 in
Fig. 6A or C. During the first reduction process, the Q-band at
680 nm and its shoulder at 614 nm decrease first, and then disap-
pear while new bands at 650 and 716 nm appears (Fig. 8A). The
result is 36 nm red shift of each band. At the same time, a weak
Fig. 8. In situ UVeVis spectral changes during the controlled potential electrolysis of 5
upon (A) the first reduction at ꢂ0.75 V vs. SCE and (B) the first oxidation at 0.80 V vs.
SCE in TBAP/DMSO.
band at 471 nm appears and the B band decreases with small red
shift from 358 to 363 nm with the appearance of a new band at
317 nm. These spectral changes have well-defined isosbestic points
at 399, 578 and 704 nm. The formation of a new band at 475 nm
and red shifting of the Q band indicate the formation of [Co(I)Pc(-
2)]ꢂ species, confirming the CV assignment of the first reduction
process, R1 to Co(II)Pc(-2)/[Co(I)Pc(-2)]ꢂ process [58,52]. Upon the
first oxidation process, the Q band at 680 nm increases slightly in
intensity with red shift to 6692 nm (Fig. 8B). At the same time, the B
band decreases considerably. The increase of the Q band with red
shift is typical of a metal-based oxidation in CoPc complexes
[58e63], and thus confirms the voltammetric assignment of Co(II)
Pc(-2)/[Co(III)Pc(-2)]þ for the first oxidation process, O1, of 5.
4. Conclusion
In
conclusion,
the
novel
6,7-[15-crown-5]-3-[p-(3,4-
dicyanophenoxy)phenyl] coumarin (1)/6,7-[15-crown-5]-3-[p-
(2,3-dicyanophenoxy)phenyl]coumarin (2) and their cobalt (II)/
copper (II) phthalocyanine complexes (3e6) have been synthesized
and characterized for the first time in this study. The fluorescence
intensity changes of compounds 1 and 2 are investigated by addi-
tion of the Naþ or Kþ ions. The fluorescence intensity decreasing is
higher by addition of Naþ cation than Kþ cation due to the different
size of these cations. The size of the Naþ cation is more suitable
than bigger size Kþ cation for cavity of 15-crown-5.
Fig. 7. Cyclic (A) and differential pulse (B) voltammograms of 2.5 ꢁ10ꢂ4 mol dmꢂ3 5 in
TBAP/DMSO.

A.A. Esenpınar et al. / Journal of Organometallic Chemistry 696 (2011) 3873e3881
3881
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Voltammmetric and in situ spectroelectrochemical measure-
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phthalocyanine complexes in TBAP/DMSO is much higher than
that of alpha-substituted ones. The huge difference in aggregation
tendency of compounds can be attributed to the deviation from
planarity in alpha-substituted molecules as a result of the non-
peripheral substitution.
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Acknowledgements
We are thankful to the Research Foundation of Marmara
University, Commission of Scientific Research Project (BAPKO) FEN-
A-090909-0302.
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