Synthesis of metal-free and zinc phthalocyanines containing 2-pyridyl-methyl pendant arm linked with NS4-donor macrocyclic moiety and their selectivity towards Cu(II) cations

Article abstract of DOI:10.1142/S1088424613500600

New phthalonitrile (L1), metal-free phthalocyanine (H₂Pc) and zinc-phthalocyanine (ZnPc) substituted in peripheral positions with 2-pyridyl methyl pendant arm linked mixed donor macrocyclic ligands have been prepared in a multi-step reaction sequence. The novel compounds were characterized by a combination of elemental anlaysis, ¹H NMR, ¹³C NMR, IR, UV-vis and MS spectral data. The influence of metal cations such as Cd ²⁺, Zn²⁺, Hg²⁺, Al³⁺, Fe ³⁺ and Cu²⁺ on the spectroscopic properties of dinitrile compound L1 and free phthalocyanine H₂Pc was investigated by means of absorption spectrophotometry. Spectrophotometric titrations were carried out with these ligands for Cu²⁺ ion. The complex composition of Cu-L1 was found 1:1 by means of spectrophotometric titration data. The spectrophotometric method showed good sensitivity for Cu²⁺ with linear range of 2.6 × 10^-6 to 1.3 × 10^-4 M with dinitrile compound.

Full text of DOI:10.1142/S1088424613500600

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2013; 17: 480–488
DOI: 10.1142/S1088424613500600
Published at http://www.worldscinet.com/jpp/
Synthesis of metal-free and zinc phthalocyanines
containing 2-pyridyl-methyl pendant arm linked with
NS4-donor macrocyclic moiety and their selectivity towards
Cu(II) cations
Nilgün Kabaya, Ümmühan Ocakb, Serhat Günb andYas¸ar Gök*a
a Department of Chemistry, Pamukkale University, 20017, Denizli, Turkey
b Department of Chemistry, Karadeniz Technical University, Trabzon, Turkey
Dedicated to Professor Özer Bekaroğlu on the occasion of his 80th birthday
Received 24 January 2013
Accepted 17 April 2013
ABSTRACT: New phthalonitrile (L1), metal-free phthalocyanine (H2Pc) and zinc-phthalocyanine
(ZnPc) substituted in peripheral positions with 2-pyridyl methyl pendant arm linked mixed donor
macrocyclic ligands have been prepared in a multi-step reaction sequence. The novel compounds were
characterized by a combination of elemental anlaysis, 1H NMR, 13C NMR, IR, UV-vis and MS spectral
data. The influence of metal cations such as Cd2+, Zn2+, Hg2+, Al3+, Fe3+ and Cu2+ on the spectroscopic
properties of dinitrile compound L1 and free phthalocyanine H2Pc was investigated by means of
absorption spectrophotometry. Spectrophotometric titrations were carried out with these ligands for Cu2+
ion. The complex composition of Cu-L1 was found 1:1 by means of spectrophotometric titration data.
The spectrophotometric method showed good sensitivity for Cu2+ with linear range of 2.6 × 10-6 to 1.3 ×
10-4 M with dinitrile compound.
KEYWORDS: metal-free phthalocyanines, zinc-phthalocyanines, mixed donor macrocycle, pendant
arm, transition metals, spectrophotometric titration.
security devices, information storage, computer disk
INTRODUCTION
writing, conducting polymers and photoconductors,
Synthetic macrocycles have been known for over 75
catalysts for oxidation of thiols, disulfides, chemical
years, although a real spate of publications in this area
sensors and photodynamic theraphy of cancer [2]. A
was observed in the late 1960s [1]. In that period, more
disadvantage of metal-free and metallophthalocyanines
than 5000 macrocyclic compounds were reported and
is their low solubility in common organic solvents.
since then their number has increased markedly from
For most of these applications, metal-free or metallo-
year to year.
phthalocyanines with long alkyl or alkoxy chains or
Phthalocyanines and their metal complexes have
macrocyclic polyether moieties had to be synthesized in
been studied for many years, and they are still the
order to facilitate the above-mentioned purposes and also
subject of intense investigation. They exhibit a number
to enhance solubility [3].
of extraordinary properties leading to their potential
The physical and chemical properties of a phthalocyanine
applications in various scientific and technological areas
containing macrocyclic moieties could also be modified by
such as pigments in paints and printing inks, infrared
the substitution and arrangement of N, O, S atoms in the ring
system. The “hard” ether-oxygen-containing macrocycles
show a binding preference toward “hard” alkali and alkaline
earth metal cation, but the incorporation of “soft” sulfide
*Correspondence to: Yaşar Gök, email: gyasar@pau.edu.tr
tel.: +90 258-296-3567, fax: +90 258-296-3535
Copyright © 2013 World Scientific Publishing Company

SYNTHESIS OF METAL-FREE AND ZINC PHTHALOCYANINES CONTAINING 2-PYRIDYL-METHYL PENDANT ARM
481
or amine linkages shifts its preference toward “soft” heavy
metal cations [4]. It has been demonstrated that macrocyclic
ligands containing nitrogen-sulfur donor atoms can behave
as highly selective complexing agents for transition metal
cations [5]. The aza-ligands are more selective against
hard ions whereas the thia-ligands preferentially bind soft
ions. Selectivity can be enhanced by combining different
donor atoms in one ring system. Therefore, nitrogen-sulfur
macrocycles having different cycle size or arrangement
have been prepared and their complexation properties have
been investigated with various metal cations [6].
Pendant arm substitution also affects the complexation
properties of a macrocycle. Such a substitution can
increase the coordination capability of the unsubstituted
macrocycles as they can encapsulate the metal into the
macrocyclic cavity [7]. The cation-binding ability of
these kind of macrocycles is essentially controlled by the
nature of the macrocyclic cavity and pendant arms [8].
Transition metal ions represent a typical class of
heavy metal ions that are generally considered to have
deleterious effect on human beings and biological systems
[9]. The dedection and measurement of copper(II) ions
have been actively investigated due to its important role
in various biological processes within the human body as
an essential trace element [10]. The higher concentration
of this cation causes liver and kidney failure as in the case
of Wilson disease [11].
a Perkin Elmer Lambda 25 spectrophotometer which is
double-beamedwiththermostaticallycontrolledcellblock.
The elemental analysis were performed on a Costech ECS
4010 insrument. Melting points were determined on an
electrothermal apparatus and are uncorrected.
Synthesis
4,5-Bis-(3-chloro-propylsulfanyl)-phthalonitrile
(3). 3-chloro 1-propanthiol 2 (3.32 g, 30 mmol) was
addedtoasolutionof4,5-dichlorophthalonitrile1(2.95g,
15 mmol) in dry dimethyl formamide (20 mL) under
argon atmosphere. After stirring for 15 min at 50 °C, dry
fine-powdered sodium carbonate (1.85 g, 17.45 mmol)
was added portion wise over 2 h with efficient stirring
to this solution. The reaction mixture was stirred under
argon at 50 °C for 7 days and monitored by thin layer
chromatography [silica gel (chloroform:hexane) (95:5)].
After cooling to room temperature, the orange mixture
was filtered off and the solvent was evaporated under
reduced pressure and dried in vacuo and then diethyl
ether (25 mL) was added to the residue and stirred
overnight. The mixture was filtered and washed with
diethyl ether and then dried in vacuo. The solid product
was purified by crystallized from the acetone:diethyl
ether mixture. Yield 3.36 g (65%), mp 106–107 °C.
Anal. calcd. for C14H14N2S2Cl2: C, 48.70; H, 4.09; N,
8.11%. Found C, 48.43; H, 3.97; N, 7.84. IR: d, cm-1
3083 (ArCH), 2957–2862 (CH2), 2231 (C≡N), 1566,
1463, 1435, 1351, 1244, 1227, 1114, 957, 648. 1H NMR
(200 MHz, CDCl3): dH, ppm 7.53 (s, 2H, ArH), 3.72 (t,
4H, ClCH2), 3.22 (t, 4H, SCH2), 2.19 (m, 4H, CH2).
13C NMR (50 MHz, CDCl3): dC, ppm 143.55, 133.27,
128.97, 114.52, 42.95, 30.40, 28.63. MS (LC-MS/MS):
m/z 345.19 [M]+.
In this work, we have been synthesized novel
phthalonitrile (L1), metal-free phthalocyanine (H2Pc)
and zinc-phthalocyanine (ZnPc) substituted in peripheral
positions with four 2-pyridyl methyl pendant arm linked
macrocyclic ligand with nitrogen-sulfur donor atoms and
also spectrophotometric titrations with L1 and H2Pc for
Cu(II) cation were investigated.
4,5-Bis-(3-iodo-propylsulfanyl)-phthalonitrile
(4). A solution of 3 (0.92 g, 2.67 mmol) in dry acetone
(15 mL) was added into a solution of dry NaI (1.60 g,
10.68 mmol) in dry acetone (30 mL) in a round-
bottom two-necked flask under argon atmosphere. The
reaction mixture was refluxed and stirred for 3 h. The
reaction was monitored by a thin layer chromatography
[silica gel (chloroform)]. At the end of this period, the
reaction mixture was cooled to room temperature and
the precipitate was filtered off, washed with dry acetone
and then the solution was evaporated to dryness under
reduced pressure. The pale yellow crude product was
crystallized from methanol. Yield 1.02 g (72%), mp 156
°C. Anal. calcd. for C14H14N2S2I2: C, 31.83; H, 2.67; N,
5.30%. Found C, 31.65; H, 2.60; N, 5.18. IR: n, cm-1
3081 (ArH), 2958–2918 (CH2), 2229 (C≡N), 1569, 1458,
1435, 1350, 1283, 1204, 1170, 1154, 1118, 959, 584. 1H
NMR (300 MHz, CDCl3): dH, ppm 7.65 (s, 2H, ArCH),
3.32 (t, 4H, ICH2), 2.47 (t, 4H, SCH2), 2.13 (m, 4H, CH2).
13C NMR (75 MHz, CDCl3): dC, ppm 141.73, 135.67,
124.52, 111.43, 41.49, 32.63, 26.44. MS (LC-MS/MS):
m/z 550.7 [M + Na]+, 582.7 [M + 3H2O]+.
EXPERIMENTAL
General methods and materials
Unless otherwise stated, all operations were carried
out under argon atmosphere in a vacuum line or using
standard Schlenk techniques. All solvents were freshly
purified by standard procedures before use [12]. The
metal perchlorates purchased from Acros were of the
highest quality available and vacuum dried over silicagel
blue before use. 2,2′-(pyridin-2-ylmethylazanediyl) dieth-
anethiol (5) was synthesized according to the known
procedure [13]. 4,5-dichlorophthalonitrile (1) and other
chemicals were purchased from Merck and Aldrich as
analytical grade and used without purification. 1H and 13C
NMRspectraweremeasuredonVarianMercury200-NMR
and Varian Mercury Plus 300-MHz instruments. Infrared
spectra were recorded on a Perkin Elmer Spectrum BX
FT-IR spectrometre as KBr pellets. Mass spectra measured
on micrOTOF and Micromass Quattro Ultima LC-MS/
MS instruments. Electronic spectra were determined on
Copyright © 2013 World Scientific Publishing Company
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N. KABAY ET AL.
12-Pyridin-2-ylmethyl-7,8,11,12,13,14,17,18-
octahydro-6H,10H,16H-5,9,15,19-tetrathia-12-
azabenzocyclo-heptadecene-2,3-dicarbonitrile (L1).
A solution of 4 (0.528 g, 1.0 mmol) in dry DMF (50 mL)
and 5 (0.228 g, 1.0 mmol) in dry DMF (50 mL) was
added via syringe pump under argon atmosphere over a
period of 20 h to a stirred suspension of pre-dried Cs2CO3
(2.96 g, 9.1 mmol) in dry DMF (250 mL) at 35 °C. The
reaction mixture was stirred at this temperature for a
further 7 days. The reaction was monitored by thin layer
chromatography (silica gel (ethyl acetate)). After cooling
to room temperature the reaction mixture was evaporated
under reduced pressure and the residue was dissolved
with chloroform (150 mL). The organic phase was
washed with water (30 mL × 3) and dried over MgSO4
and then evaporated under reduced pressure to give brown
oil product. The crude product was purified by column
chromatography technique (silica gel (ethyl acetate)).
Yield 0.29 g (58%).Anal. calcd. for C24H28N4S4: C, 57.56;
H, 5.64; N, 11.19%. Found C, 57.26; H, 5.46; N, 11.08.
IR: n, cm-1 3082 (ArH), 3059 (PyH), 2923–2852 (CH2),
2227 (C≡N), 1648, 1588, 1560, 1457, 1431, 1346, 1257,
1224, 1112, 1044, 993. 1H NMR (300 MHz, CDCl3): dH,
ppm 8.55 (d, 1H, py-H), 7.75 (t, 1H, py-H), 7.69 (s, 2H,
Ar-H), 7.58 (d, 1H, Py-H), 7.28 (t, 1H, Py-H), 3.77 (s, 2H,
Py-CH2), 2.73 (m, 4H, NCH2), 2.63 (m, 4H, Ar-SCH2),
2.55 (m, 8H, SCH2), 2.01 (m, 4H, CH2). 13C NMR (75
MHz, CDCl3): dC, ppm 159.49, 149.32, 144.78, 136.83,
135.51, 131.23, 123.40, 128.62, 123.40, 122.91, 115.60,
112.34, 60.34, 55.71, 40.18, 32.31, 27.82. MS (LC-MS/
MS): m/z 501.13 [M + 1]+.
were added into a Schlenk tube and then heated and
stirred at 180 °C for 6 h under argon. After having cooled
to room temperature, the product was precipitated by
adding methanol. Solid product was filtered and washed
with methanol and diethyl ether. The purification of the
green precipitate was carried out in a soxhlet extractor
with chloroform. The solvent was then evaporated to
give a green zinc phthalocyanine. The product was
dried in vacuo. Yield 0.020 g (53%). Anal. calcd. for
C96H112N16S16Zn: C, 55.74; H, 5.46; N, 10.83%. Found C,
55.49; H, 5.38; N, 10.75. IR: n, cm-1 3096 (CHAr), 2846–
2921 (CH3), 1645 (C=N), 1551, 1412, 1399, 1373, 1114,
1087, 1067, 943, 745, 699. UV-vis (CHCl3): lmax, nm
(log e) 709 (4.84), 660 (4.56), 365 (4.79), 301 (4.80). 1H
NMR (200 MHz, CDCl3): dH, ppm 8.72 (m, 4H, Py-H),
8.01 (m, 4H, Py-H), 7.74 (m, 8H, Ar-H), 7.49 (m, 4H,
Py-H), 7.35 (m, 4H, Py-H), 4.09 (m, 8H, Py-CH2), 2.83
(m, 16H NCH2), 2.51 (m, 16H, Ar-S-CH2), 2.39 (m, 32H,
SCH2), 1.89 ( m, 16H, CH2).
RESULTS AND DISCUSSION
The preparation of the target metal-free (H2Pc)
and zinc(II) phthalocyanines (ZnPc) is shown in
Scheme 1. To prepare the compound 3, 1,2-dichloro-
4,5-dicyanobenzene (1) was reacted with 3-chloro-
1-propanthiol (2) in dry DMF and Na2CO3. This
1
displacement reaction was recognized in the H NMR
spectrum from the proton resonance of the CH2Cl, CH2S
and CH2 groups. By proton-decoupled 13C NMR spectral
data of the same compound, the presence of new signals
due to the same groups also supported the formation of
the proposed compound (3). The mass spectrum of 3,
which showed a peak at m/z = 345 [M]+ supported the
proposed formula of this compound.
Conversion of 3 to 4 in 72% yield was carried out in
dry acetone in the presence of dry NaI. The resonances
of the aromatic protons and aromatic carbons in the
proton or carbon-13 NMR spectra of 4 were very similar
to those of the precursor compound 3 except for the
chemical shifts of carbons and protons connected to
CH2-I groups. The elemental analysis and mass spectrum
of 4 also supported the replacement of chlorine by iodine
with the peaks at m/z = 550 and 582 indicating [M + Na]+
and [M + 3H2O]+ formation, respectively.
Synthesis of metal-free phthalocyanine (H2Pc).
Dicarbonitrile compound (L1) (0.1352 g, 0.2704 mmol),
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU; 0.3 mL)
and dry pentanol (2.5 mL) were added into a Schlenk
tube and then heated and stirred at 155 °C for 6 h under
argon. After the reaction mixture cooled, the product
was precipitated by adding methanol. Solid product was
filtered and washed with methanol and diethyl ether. The
purification of the dark green precipitate was carried
out in a soxhlet extractor with chloroform. The solvent
was then evaporated to give a deep green metal-free
phthalocyanine. The product was dried in vacuo. Yield
0.035 g (26%). Anal. calcd. for C96H114N16S16: C, 57.51;
H, 5.73; N 11.18%. Found C, 57.27; H, 5.58; N, 10.95.
IR: n, cm-1 3221 (NH), 3090, 3062 (ArH), 2927–2858
(CH2), 1645 (C=N), 1541, 1424, 1261, 1196, 1022, 856.
UV-vis (CHCl3): lmax, nm (log e) 731 (4.50), 699 (4.53),
17-membered monoaza-tetrathiamacrocycle (L1)
was obtained in 58% yield from compound 4 with
2,2′-(pyridine-2-ylmethylazadiyl)-diethanethiol (5)
1
1
at 35°C. It was found that H NMR spectrum of L1
670 (4.37), 447 (4.20), 296 (4.74), 352 (4.65). H NMR
clearly indicated the characteristic emerged resonances
for the 17-membered macrocycles. This compound
contained a pyridyl moieties and was substantiated by
two characteristic resonances as expected. 13C NMR
spectrum of this compound showed individual resonances
for the novel methylene connected to N, S atoms clearly
suggesting the desired macrocyclization had accurred.
Compound L1 displayed the expected molecular ion
(200 MHz, CDCl3): dH, ppm 8.65 (m, 4H, Py-H), 7.78
(m, 4H, Py-H), 7.65 (s, 8H, Ar-H), 7.55–7.14 (m, 4H,
Py-H), 7.39 (m, 4H, Py-H), 3.97 (m, 8H, Py-CH2), 2.89
(m, 16, NCH2), 2.58 (m, 16H, Ar-S-CH2), 2.48 (m, 32H,
SCH2), 1.93 (m, 16H, CH2), -2.29 (s, 2H, N-H).
Synthesis of zinc phthalocyanine (ZnPc). A mixture
of compound (H2Pc) (0.037 g, 0.0185 mmol), anhydrous
Zn(OAc)2 (0.0034 g, 0.0185 mmol) and quinoline (1 mL)
Copyright © 2013 World Scientific Publishing Company
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SYNTHESIS OF METAL-FREE AND ZINC PHTHALOCYANINES CONTAINING 2-PYRIDYL-METHYL PENDANT ARM
483
Cl
S
Cl
Cl
NC
NC
NC
NC
Na2CO3, Ar
2
+
dry DMF, 50 °C
9 d
SH
Cl
S
Cl
2
1
3
Ar, NaI
dry CH3COCH3
reflux, 7 d
S
Cs2CO3, Ar
dry DMF
S
S
I
CN
N
NC
N
N
+
high dil.
35 °C, 7d
N
CN
NC
I
S
S
S
HS
SH
5
4
L1
Ar, DBU,
dry n-pentanol
150 °C, 6 h
N
N
N
N
N
S
N
S
N
N
S
S
S
S
S
S
S
S
S
S
S
S
S
S
N
Zn
N
N
Ar, dry quinoline
anhyd. Zn(CH3COO)2
N
N
NH
N
N
N
N
N
N
180 °C, 6 h
HN
N
N
N
S
S
S
S
S
S
N
S
S
S
S
S
S
S
S
S
S
N
N
N
N
N
N
N
H2Pc
Scheme 1. Synthesis of metal-free (H2Pc) and zinc phthalocyanine (ZnPc)
ZnPc
peak at m/z = 501 [M + 1]+ in its mass spectrum, which
supported the structure. The result of the mass spectrum
of L1 is shown in Fig. S1 (Supplementary information).
Cyclotetramerization of four dicyano compound (L1)
into the metal-free phthalocyanine was carried out in
dry n-pentanol in 26% yield as deep green solid after
purification. The H NMR spectrum of H2Pc in CDCl3
exhibited the characteristic resonances of the macrocycle
and phtahaolcyanine moieties. Strong shielding of the
cavityprotonsinthephthalocyaninecoreofthiscompound
1
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484
N. KABAY ET AL.
was manifested by a broad signal at d = -2.29 ppm at
the high concentration which is attributed to the N–H
resonance and easily confirmed with deuterium exchange
[14]. In the IR spectrum of this compound, a diagnostic
feature of the formation of L1 was the disappearance
of the sharp C≡N resonances and the presence of
C=N and N–H vibrations at 1645 and 3221 cm-1,
respectivley, confirmed the formation of metal-free
phthalocyanine.
The synthesis of zinc(II) phthalocyanine (ZnPc) was
accomplished with metal-free phthalocyanine (H2Pc)
1
and anhydrous Zn(CH3COO)2 in dry quinoline. The H
NMR spectrum of ZnPc was identical with those of the
precursor metal-free phthalocyanine (H2Pc), a significant
difference being the disappearance of the broad inner
core NH protons. However, aromatic protons which are
neighbourhood to phthalocyanine core were shifted to
lower field because of the p-electron ring current effect
of the phthalocyanine core even after complexation with
zinc(II) [15]. The characteristic proton resonances of the
proposed structure of ZnPc exhibited the pyridyl and
aliphatic resonances of monoazatetrathia macrocycle
moieties at the expected region.
The UV-vis spectra of H2Pc and ZnPc in chloroform
showed characteristic absorption in the Q-band region
at 731–670 and 709–660 nm, respectively (Fig. 1).
The split Q-band for metal-free phthalocyanine which
is the characteristics of this class of
Fig. 1. UV-vis spectra of H2Pc (−) and ZnPc (−) (1 × 10-5 M in
chloroform)
compounds showed the Q-band absor-
ptions of D2h symmetry [16]. This two
absorptions around 731(Qx) and 699
(Qy) nm were due to the p→p* trasition
of the fully conjugated 18 p electron
system [17]. For H2Pc, the effect of
macrocyclic thia substitution caused
a shift of intense Q-band to higher
wavelengths compared to substituted
alkyl or alkoxy derivatives [18]. The
bands of H2Pc were broadened due to
the superimposition of the B1 and B2
bands in the 350 nm region [19]. The
electronic spectrum of ZnPc showed
characteristic Q-band absorption as a
singlet peak at 709 nm and a shoulder at
Fig. 2. The absorption spectra of the ligands (L1) and H2Pc. Concentration: 1.3 ×
660 nm. The formation of ZnPc caused
significant change in the Q-band with
incresing of the intensity of the peak
at 731 nm which observed for H2Pc.
The absorption spectrum of ZnPc also
10-5 M. Solvent:chloroform-acetonitrile (1/1)
were measured using 1 cm long absorption cell. Figure 3
showed monomeric behavior evidenced by a single and
narrow Q-band typical for tetrasubstituted derivatives of
metallophthalocyanines [18a].
The UV-vis spectra of L1 and H2Pc in acetonitrile-
chloroform solution (1/1) are given Fig. 2. Absorption
spectra of L1 with a concentration of 1.29 × 10-5 M in
acetonitrile-chloroform solution (1/1) containing 10
molar equivalents of appropriate metal perchlorate salt
shows the effect of Al3+, Fe3+, Cd2+, Zn2+, Hg2+ and Cu2+
cations on the absorptions of the nitrile compound, L1.
As seen from Fig. 3, all metal cations caused moderate
change in absorbance at 278 nm except for Cu2+. Cu2+
caused a significant enhancement in absorption at 278 nm.
This finding suggested that the nitrile compound L1
interacted strongly with Cu2+ compared to other metal
cations.
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SYNTHESIS OF METAL-FREE AND ZINC PHTHALOCYANINES CONTAINING 2-PYRIDYL-METHYL PENDANT ARM
485
Fig. 3. The effects of metal cations on the absorption spectra of L1. Solvent: acetonitrile-chloroform (1/1), Ligand concentration:
1.3 × 10-5 M. Metal perchlorate concentration: 1.3 × 10-4 M
Fig. 4. The effects of metal cations on the absorption spectra of H2Pc. Solvent: acetonitrile-chloroform (1/1), Ligand concentration:
1.3 × 10-5 M. Metal perchlorate concentration: 1.3 × 10-3 M
The effect of Al3+, Fe3+, Cd2+, Zn2+, Hg2+ and Cu2+
cations in the absorption of the free phthalocyanine H2Pc
with a concentration of 1.29 × 10-5 M in acetonitrile-
chloroform solution (1/1) were shown in Fig. 4. 100-fold
metal concentrations were used in measurements.As seen
from Fig. 4, all metal cations caused moderate changes in
absorbance within the Q-band region (699 nm) except for
Cu2+. This result was similar to that of L1. However, a
significant decrease in absorbance was observed for Cu2+
in the case of H2Pc. This finding suggested that the free
phthalocyanine compound H2Pc also interacted strongly
with Cu2+ compared to other metal cations.
atoms. Soft donor atoms, especially sulfur, prefer
interaction with soft metal ion such as Cu2+ [20]. This
is well-known as HSAB concept [21]. In this content,
crown ether rings on the peripheral positions of the
phthalocyanine compound H2Pc may be effective with
the interaction with Cu2+.
Spectrophotometric titrations
According to the results of Figs 3 and 4, we decided to
carry out spectrophotometric titrations with L1 and H2Pc
for Cu2+ ion. Spectrophotometric titration was not carried
out with ZnPc because it does not have good solubility in
acetonitrile-chloroform solution (1/1). Figure 5 shows the
The interaction of Cu2+ ion with both ligands can be
explained with the crown ether ring having soft donor
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486
N. KABAY ET AL.
Fig. 5. Absorption spectra of (L1) complexed with Cu2+. The spectral changes during the addition of 0–6 equivalents of Cu(ClO4)2.
Ligand concentration: 1.3 × 10-5 M. Inset: Molar ratio plot for the Cu-L1 complex. Wavelength: 345 nm
Fig. 6. Absorbance of the L1 vs. the Cu2+ concentration for the spectrophotometric titration. Wavelength: 278 nm, ligand
concentration = 1.3 × 10-5 M
change of absorption spectra of L1 with increasing Cu2+
concentration. The spectral changes were recorded during
the addition of 0–6 equivalents of Cu(ClO4)2. Inset shows
molar ratio plot for the Cu-L1 complex. The inflection
point was 1.0 ([M]/[L]). It can thus be concluded that L1
formed a stable 1:1 (M:L) complex with Cu2+. Figure 6
shows the regular absorbance enhancement depending
on increasing Cu2+ concentrations with L1. A linear
response of the absorbance at 278 nm as a function
of Cu2+ concentration was observed from 2.6 × 10-6 to
1.3 × 10-4 M with linearly dependent coefficient R2 =
0.9993 (Fig. 6).
The change in the absorption spectra of the ligand
H2Pc with increasing concentrations of Cu2+ is shown
in Fig. 7. There are three isosbestic points at 486, 596,
and 758 nm. This result indicates that there were three
equilibriums during the complexation. Isosbestic points
were not clear when it was observed in detail. This
seems to be due to the presence of small amounts of
free ligand. The presence of many isosbestic points may
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 486–488

SYNTHESIS OF METAL-FREE AND ZINC PHTHALOCYANINES CONTAINING 2-PYRIDYL-METHYL PENDANT ARM
487
Fig. 7. The change in absorption spectra of H2Pc increasing Cu2+ concentration. 0–10 equivalents of Cu(ClO4)2. Ligand concentration:
1.3 × 10-5 M. Inset: Molar ratio plot, 698 nm
Fig. 8. Absorbance of the H2Pc vs. the Cu2+ concentration for the spectrophotometric titration. Wavelength: 698 nm, ligand
concentration = 1.3 × 10-5 M
result from different complex compositions. Figure 7
inset shows the molar ratio plot for Cu-Pc complex.
CONCLUSION
As seen from the inset, the break point is [M]/[L] = 4.
This result shows that the complex stoichiometry for
Cu-Pc is 4:1 (M:L). In this case, one can be say that
Cu2+ ions insert monoazatetrathia crown ether cavities
in peripheral positions of the free phthalocyanine
compound H2Pc. Reason of this is affinity of soft
sulfur donor atoms to soft metal ion such as Cu2+
as expected from HSAB concept. We also found a
regular change in the absorption spectra of H2Pc with
increasing concentrations of Cu2+. A linear decrease
of the absorbance at 698 nm as a function of Cu2+
concentration were observed from 1.3 × 10-5 to 3.4 ×
10-5 M with linearly dependent coefficient R2 = 0.9868
(Fig. 8).
A peripherally substituted phthalocyanine derivative
containing pendant armed linked 17-membered monoaza-
tetrathia macrocycle was synthesized in good yield by the
cycloteramerization reaction of 12-pyridine-2-ylmethyl-
7,8,11,12,13,14,17,18-octahydro-6H,10H,16H-
5,9,15,19-tetrathia-12-azabenzocycloheptadecene-2,3-
dicarbonitrile in the presence of DBU in dry n-pentanol.
With the desired anhydrous zinc(II) acetate, it became
possible to convert the metal-free phthalocyanine into
metallo derivative (ZnPc). This acetate of Zn(II) has been
used in dry quinoline to prepare metallphthalocyanine.
All structures of the novel compounds have been
unequivocally identified by using elemental analaysis,
IR, NMR, UV-vis and MS techniques.
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 487–488

488
N. KABAY ET AL.
On the other hand, both L1 and H2Pc can be used as
selective ligands to determinate Cu2+ ion in various real
samples by spectrophotometric method. This result has
an important role in a possible selective system. We
observed that L1 showed a selectivity for Cu(II) cation
as seen in Fig. 6, that may lead to practical applications
in the field of environmental sciences. It is obvious that,
L1 is better than H2Pc because of it’s larger linear range
for Cu2+ concentration (2.6 × 10-6 to 1.3 × 10-4 M), the
higher linear dependent coefficient (R2 = 0.9993) and the
simpler chemical structure.
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Supporting information
Mass spectrum of L1 is given in the supplementary
material (Fig. S1). This material is available free of
charge via the Internet at http://www.worldscinet.com/
jpp/jpp.shtml.
Acknowledgements
The authors thank to the Research Fund of Pamukkale
University, Project number: 2008 FBE 002 (Denizli/
Turkey) for financial support.
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