Azine-bridged binuclear metallophthalocyanines functioning photophysical and photochemical-responsive

Article abstract of DOI:10.1016/j.dyepig.2012.05.010

The new phthalodinitrile containing azine-bridged (3) was prepared by the reaction of 4-nitrophthalonitrile (2) and 4,4′-(1E,1'E)-hydrazine-1,2- diylidenebis(methan-1-yl-1-ylidene)diphenol (1). The new binuclear asymmetric type zinc(II) (5), oxotitanium(I

Full text of DOI:10.1016/j.dyepig.2012.05.010

Dyes and Pigments 95 (2012) 330e337
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Azine-bridged binuclear metallophthalocyanines functioning photophysical
and photochemical-responsive
c
,
a
Rıza Bayrak a, Hakkı Türker Akçay a, Mehmet Pis¸ kin b, Mahmut Durmus¸ , Ismail Degirmencioglu
_
*
ꢀ
ꢀ
a Department of Chemistry, Faculty of Arts and Sciences, Karadeniz Technical University, 61080 Trabzon, Turkey
b Marmara University, Faculty of Art and Science, Department of Chemistry, 34722 Kadikoy-Istanbul, Turkey
c Gebze Institute of Technology, Department of Chemistry, P.O. Box, 141, 41400 Gebze, Kocaeli, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
The new phthalodinitrile containing azine-bridged (3) was prepared by the reaction of 4-
nitrophthalonitrile (2) and 4,40-(1E,1’E)-hydrazine-1,2-diylidenebis(methan-1-yl-1-ylidene)diphenol
(1). The new binuclear asymmetric type zinc(II) (5), oxotitanium(IV) (6), tin(II) (7), cobalt(II) (8), cop-
per(II) (9) and nickel(II) (10) phthalocyanine complexes containing azine moiety were synthesized by the
cyclotetramerization of azine containing phthalonitrile (3) and unsubstituted phthalonitrile (4). The
aggregation behaviors of these compounds were investigated at different concentrations in dime-
thylsulfoxide (DMSO). Furthermore, the photophysical (fluorescence quantum yields and lifetimes) and
photochemical properties (singlet oxygen and photodegradation quantum yields) were studied for zin-
c(II) (5), oxotitanium(IV) (6) and tin(II) (7) phthalocyanine complexes in DMSO. The synthesized cobalt
(8), copper (9) and nickel (10) phthalocyanine complexes were not evaluated for this purpose due to
transition metal and paramagnetic behavior of central metals in the phthalocyanine cavity.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 28 April 2012
Received in revised form
13 May 2012
Accepted 14 May 2012
Available online 22 May 2012
Keywords:
Phthalocyanine
Dimeric
Azine
Fluorescence
Photophysics
Photochemistry
1. Introduction
planar phthalocyanine rings. Additionally, bulky peripheral
substitutions of phthalocyanines increase their solubility in
Phthalocyanines (Pcs) are important class of compounds for
many technological applications in different scientific areas such as
chemical sensors [1e3], electrochromic displaying systems [4],
non-linear optics [5], solar cells [6], molecular electronics [7],
semiconductors [8], liquid crystals [9], optical storage devices [10],
laser dyes [11], catalyst [12] and photodynamic therapy (PDT) [13].
Binuclear phthalocyanines have two phthalocyanine units con-
necting one another via covalently bonding. Many researchers have
been focused on their metal complexes due to their different
electrical and spectroscopic properties [14e16].
Main drawback of phthalocyanines is aggregation causing low
photosensing ability in technological applications. Aggregation
decreases the solubility of the phthalocyanines in many organic
solvents or water. The substitution of Pcs with different bulky
organic groups or cationic and anionic species or axially substitu-
tion on the central metal ions can increase the solubility of these
compounds [17e20]. Especially bulky peripheral substituents
common organic solvents. Generally, it’s known that organic
solvents decrease the aggregation, while aqueous solvents increase
it. Furthermore the type of solvent is important factor on the
photophysical and photochemical properties of MPc complexes
[21e25].
The highest absorption band of phthalocyanines in visible
region is Q band and this band occurs because of the transition
between the HOMO (highest occupied molecular orbital) and
LUMO (lowest unoccupied molecular orbital). The most important
advantage of Pcs compared with porphyrins is their Q bands which
have more intense and longer wavelengths than that of porphyrins.
Therefore some phthalocyanines show higher biological activity
against tumors than porphyrins due to long wavelength absorption
[26,27].
In heterocyclic chemistry, although the term of azine is used for
description of six-membered ring system such as pyrazines,
pyrimidines, in acyclic chemistry, azines are non-heterocyclic
compounds which are synthesized one mol hydrazine hydrate
reaction with 2 mol aldehyde. Additionally this compound class is
called “aldazines” when an aldehyde is used as carbonyl compound
[28,29]. Some azines are biological active compounds having anti-
tumor [30], antibacterial [31] and antifungal activity [32].
decrease the aggregation, hindering the
pep stacking between
* Corresponding author. Tel.: þ90 262 6053075; fax: þ90 262 6053101.
E-mail address: durmus@gyte.edu.tr (M. Durmus¸ ).
0143-7208/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2012.05.010

R. Bayrak et al. / Dyes and Pigments 95 (2012) 330e337
331
Many researchers have been focused on binuclear phthalocya-
2.3. Photophysical parameters
nines and their metal complexes due to their different electrical and
spectroscopic properties. The objectives of this research are to
determine whether new peripherally azine-bridged binuclear
phthalocyanines have potential for photodynamic therapy of cancer.
The azine moiety is symmetrical molecule with high conjugation
providing chemical stability. The chemical stability is important
parameter in the photochemical studies. Furthermore, in literature
there isn’t any study on synthesis, photophysical and photochemical
characterisation of the phthalocyanine derivatives having azine
moieties. In this study, new phthalonitrile derivative (3) consisting
of two phthalonitrile unit and its zinc(II) (5), oxotitanium(IV) (6),
tin(II) (7), cobalt(II) (8), copper(II) (9) and nickel(II) (10) phthalocy-
anine derivatives were synthesized and characterized. The aggre-
gation behaviors of these dimeric metallophthalocyanines (5e10)
were investigated at different concentration in DMSO. The photo-
physical (fluorescence quantum yields and lifetimes) and photo-
chemical (singlet oxygen and photodegradation quantum yields)
properties were investigated for zinc(II) (5), oxotitanium(IV) (6),
tin(II) (7) phthalocyanine complexes in DMSO. The investigation of
the photophysical and photochemical properties of phthalocyanine
complexes are very useful for photocatalytic applications such as
photodynamic therapy of cancer.
2.3.1. Fluorescence quantum yields and lifetimes
Fluorescence quantum yields (FF) were determined by the
comparative method using equation (1) for zinc(II) (5), oxotita-
nium(IV) (6) and tin(II) (7) phthalocyanine complexes [36].
F,AStd,n2
FF
¼
FFðStdÞ
(1)
F
Std,A,n2Std
where F and FStd are the areas under the fluorescence emission
curves of the samples [zinc(II) (5), oxotitanium(IV) (6) and tin(II) (7)
phthalocyanines] and the standard, respectively. A and AStd are the
respective absorbances of the samples and standard at the excita-
tion wavelengths, respectively. n and nstd are the refractive indices
of solvents used for the sample and standard, respectively.
Unsubstituted ZnPc (Std-ZnPc) (FF ¼ 0.20) [37] was employed as
the standard in DMSO. The absorbance of the solutions at the
excitation wavelength ranged between 0.04 and 0.05
Natural radiative lifetimes (s0) were determined using Photo-
chemCAD program [38] which uses the StricklereBerg equation.
The fluorescence lifetimes (
s
F) were evaluated using equation (2).
(2)
sF
FF
¼
s0
2. Experimental
2.4. Photochemical parameters
2.1. Materials
2.4.1. Singlet oxygen quantum yields
Singlet oxygen quantum yield (FD) determinations were carried
out using the experimental set-up described in literature [39e41]
for zinc(II) (5), oxotitanium(IV) (6) and tin(II) (7) phthalocyanine
complexes in DMSO. Typically, a 3 cm3 portion of the respective
zinc(II) (5), oxotitanium(IV) (6) and tin(II) (7) phthalocyanine
solutions (C ¼ 1 ꢀ 10ꢁ5 M) containing the singlet oxygen quencher
was irradiated in the Q band region with the photo-irradiation set-
up described in references [39e41]. Singlet oxygen quantum yields
All reactions were carried out under dry and oxygen-free
nitrogen atmosphere using standard Schlenk techniques. 1,3-
diphenylisobenzofuran (DPBF) and 1,8-diazabycyclo[5.4.0]undec-7-
ene (DBU) were purchased from Fluka. Unsubstituted phthalonitrile
(4) was purchased from Merck. Unsubstituted ZnPc was purchased
from Aldrich. All solvents were dried and purified as described by
Perrin and Armarego [33] before use. 4,40-(1E,1’E)-hydrazine-
1,2-diylidenebis(methan-1-yl-1-ylidene)diphenol (1) [34] and 4-
nitrophthalonitrile (2) [35] were prepared according to the literature.
(FD) were determined in air using the relative method with
unsubstituted ZnPc (Std-ZnPc) as reference in DMSO. DPBF was
used as chemical quencher for singlet oxygen quantum yield
determinations. Equation (3) was employed for the calculations:
2.2. Equipment
1H NMR and 13C NMR (for phthalonitrile compound 3) spectra
were recorded on a Varian XL-200 NMR spectrophotometer in
CDCl3 and chemical shifts were reported (d) relative to Me4Si as
Std
R,I
RStd,Iabs
FD
FSDtd
abs
¼
(3)
where FSDtd is the singlet oxygen quantum yield for the standard
unsubstitutedZnPc(FDStd ¼ 0.67inDMSO)[42]. Rand RStd aretheDPBF
photobleaching rates in the presence of the respective samples [zin-
c(II) (5), oxotitanium(IV) (6) and tin(II) (7) phthalocyanines] and
internal standard. FT-IR spectra were recorded on a PerkineElmer
Spectrum one FT-IR spectrometer in KBr pellets. The mass spectra
were measured with a Micromass Quattro LC/ULTIMA LC- MS/MS
spectrometer using chloroformemethanol as solvent system and
a linear mode Bruker Microflex LT MALDI-TOF mass spectrometer
using nitrogen laser accumulating 50 laser shots in dihydrox-
ybenzoic acid (DHB) as MALDI matrix. All experiments were per-
formed in the positive ion mode. Elemental analyses were
performed on a Costech ECS 4010 instrument; the obtained values
agreed with the calculated ones. Melting points were measured on
an electrothermal apparatus and are uncorrected. Absorption
spectra in the UVevisible region were recorded with a Shimadzu
2101 UVeVis spectrophotometer. Fluorescence excitation and
emission spectra were recorded on a Varian Eclipse spectrofluo-
rometer using 1 cm path length cuvette at room temperature.
General Electric quartz line lamp (300 W) was used for photo-
irradiation studies. A 600 nm glass cut off filter (Schott) and
a water filter were used to filter off ultraviolet and infrared radia-
tions. An interference filter (Into, 670 nm with a band width of
40 nm) was additionally placed in the light path before the sample.
Light intensities were measured with a POWER MAX5100 (Mole-
lectron detector incorporated) power meter.
Std
standard, respectively. Iabs and I are the rates of light absorption by
abs
the samples and standard, respectively. To avoid chain reactions
induced by DPBF in the presence of singlet oxygen [43], the concen-
tration of quenchers was lowered to w3 ꢀ 10ꢁ5 M. Solutions of
sensitizer (1 ꢀ10ꢁ5 M) containingDPBFwereprepared inthedark and
irradiated in the Q band region using the photo-irradiation set-up and
degradation of DPBF at 417 nm was monitored. The light intensity
6.45 ꢀ 1015 photons sꢁ1 cmꢁ2 was used for FD determinations.
2.4.2. Photodegradation quantum yields
Photodegradation quantum yield (Fd) determinations were
carried out using the experimental set-up described in literature
[39e41]. Photodegradation quantum yields were determined using
equation (4),
ðC0 ꢁ CtÞ,V,NA
Fd
¼
(4)
I
abs,S,t

332
R. Bayrak et al. / Dyes and Pigments 95 (2012) 330e337
where C0 and Ct are the samples [zinc(II) (5), oxotitanium(IV) (6)
and tin(II) (7) phthalocyanines] concentrations before and after
irradiation respectively, V is the reaction volume, NA is the Avoga-
dro’s constant, S is the irradiated cell area, t is the irradiation time
and Iabs is the overlap integral of the radiation source light intensity
and the absorption of the samples. A light intensity of 2.15 ꢀ 1016
photons sꢁ1 cmꢁ2 was employed for Fd determinations.
Yield: 0.04 g, (7.1%), mp:>300 ꢂC (decomposition). Anal. Calc. for
C78H40N18O4Ti2: C, 67.45; H, 2.90; N, 18.15; Found: C, 67.49; H, 2.94;
N, 18.77. FT-IR (KBr tablet) ymax/cmꢁ1: 3045
y
(AreCH), 2927e2847
(CH ¼ N), 1269e1252
(CH), 953 (Ti]O). 1H NMR (DMSO-d6), (
: ppm):
y(aliph. CH), 1618e1611
(CeOeC), 981
y(C]C), 1503 y
y
d
d
8.92 (s, 2H, CH ¼ N), 7.92e7.59 (m, 18H/AreH), 7.42e7.03 (bm, 20H/
AreH). UVevis (DMSO): lmax/nm (log ): 689 (4.91), 623 (4.28), 340
3
(4.64). MALDI-TOF-MS, (m/z): Calculated: 1389.05; Found: 1389.90
[M þ H]þ.
2.5. Synthesis
2.5.1. 4,40-(2,20-(1E,1’E)-hydrazine-1,2-diylidenebis(methan-1-yl-1-
ylidene)bis(2,1-phenylene))bis(oxy)diphthalonitrile (3)
2.5.2.3. Dimeric tin(II) phthalocyanine (7). Solvent system for
column chromatography: Chloroform:methanol (100:4). Yield:
0.04 g, (6.6%), mp:>300 ꢂC (decomposition). Anal. Calc. for
C78H40N18O2Sn2: C, 62.51; H, 2.69; N, 16.82; Found: C, 62.54; H,
Compound 1 (1.39 g, 5.78 mmol) was added to a solution of 4-
nitrophthalonitrile (2) (2 g, 11.55 mmol) in dry DMF (20 cm3) and
the temperature was increased up to 55 ꢂC. Finely powdered dry
K2CO3 (1.60 g, 11.56 mmol) was added to the reaction in eight equal
portions at 15 min intervals with efficient stirring and the reaction
was stirred at the same temperature for 5 days. The reaction
mixture was poured into ice-water and the precipitate was filtered
and dried in vacuum over P2O5 and recrystallized from ethanol to
give dark yellow crystalline powder. Yield: 1.97 g, (69.2%), mp:
214e215 ꢂC. Anal. Calc. for C30H16N6O2: C, 73.16; H, 3.27; N, 17.06,
Found: C, 73.18; H, 3.25; N,17.09. FT-IR (KBr tablet) ymax/cmꢁ1: 3051
2.64; N, 16.86. FT-IR (KBr tablet) ymax/cmꢁ1: 3052
y
(AreCH),
(CH ¼ N),
(CH). 1H NMR (DMSO-d6), (
: ppm):
2934e2861
1275e1242
y
(aliph. CH), 1621e1604
y(C]C), 1512 y
y(CeOeC), 986
d
d
9.02 (bs, 2H, CH ¼ N), 8.03e7.87 (m, 10H/AreH), 7.77e7.65 (bd, 8H/
AreH), 7.52-7.02 (bm, 20H/AreH). UVevis (DMSO): lmax/nm
(log ): 691 (4.96), 628 (4.26), 342 (4.69). MALDI-TOF-MS, (m/z):
3
Calculated: 1498.71; Found: 1566.76 [M þ 4OH]þ.
2.5.2.4. Dimeric cobalt(II) phthalocyanine (8). Solvent system for
column chromatography: Chloroform:methanol (100:5). Yield:
0.08 g, (14.3%), mp:>300 ꢂC (decomposition). Anal. Calc. for
C78H40N18O2Co2: C, 67.93; H, 2.92; N, 18.28; Found: C, 67.81; H,
y
(AreCH), 2925e2851
C), 1505
(CH ¼ N), 1270e1253
(DMSO-d6), (
: ppm): 8.27 (s, 2H, CH ¼ N), 7.89e7.85 (m, 4H/AreH),
7.69e7.65 (d, 2H/AreH), 7.46e7.43 (m, 4H/AreH), 6.99-6.92 (m, 4H/
AreH). 13C NMR (DMSO-d6), (
: ppm): 162.21, 160.78, 160.65,
y
(aliph. CH), 2227 (C^N), 1621e1601
y(C]
y
y(CeOeC), 982
d
(CH). 1H NMR
d
2.84; N, 18.36. FT-IR (KBr tablet) ymax/cmꢁ1: 3054
y
(AreCH),
(CH ¼ N),
(CH). UVevis (DMSO): lmax/nm (log ):
d
2924e2847
1272e1249
y
(aliph. CH), 1615-1602
y(C]C), 1509 y
139.75, 134.25, 129.62, 126.13, 124.14, 118.87, 115.89, 115.25, 112.35,
y
(CeOeC), 982
d
3
107.84. MS (ESI), (m/z): Calculated: 492.13; Found: 493.61 [M þ H]þ.
656 (5.27), 595 (4.63), 325 (5.05). MALDI-TOF-MS, (m/z): Calcu-
lated: 1379.16; Found: 1402.59 [M þ Na]þ.
2.5.2. General procedure for synthesis of dimeric
metallophthalocyanines (5e10)
2.5.2.5. Dimeric copper(II) phthalocyanine (9). Solvent system for
column chromatography: Chloroform:methanol (100:8). Yield:
0.07 g, (12.4%), mp:>300 ꢂC (decomposition). Anal. Calc. for
C78H40N18O2Cu2: C, 67.48; H, 2.90; N, 18.16; Found: C, 67.53; H,
In a glass sealed tube, the mixture of compound 3 (0.20 g,
0.406 mmol), phthalonitrile 4 (0.32 g, 2.489 mmol) and related
metal salts [(Zn(Ac)2 (0.149 g, 0.812 mmol); Ti(OBu)4 (0.28 cm3,
0.812 mmol); SnCl2 (0.472 g, 2.489 mmol); CoCl2 (0.105 g,
0.812 mmol); CuCl2 (0.109 g, 0.812 mmol); Ni(Ac)2 (0.144 g,
0.812 mmol)] in dry n-pentanol (3 cm3) was heated to 90 ꢂC and 3
drops of 1,8-diazabycyclo[5.4.0]undec-7-ene (DBU) was added and
the temperature was increased to 160 ꢂC for 24 h. Then they were
precipitated by methanol and then filtered. After washing with hot
water, ethanol, acetone and diethyl ether, the precipitates were
dissolved in chloroform and filtered. Then chloroform was evapo-
rated under reduced pressure. The pure dimeric metal-
lophthalocyanines (5e10) were isolated through silica gel column
to remove impurities as well as formed symmetrically unsub-
stituted phthalocyanines. The chemical and physical spectral
characteristics of these new products are given below.
2.94; N, 18.09. FT-IR (KBr tablet) ymax/cmꢁ1: 3049
y
(AreCH), 2921-
(CH ¼ N), 1268e1248
(CH). UVevis (DMSO): lmax/nm (log ): 670 (5.24),
2844
y(aliph. CH), 1618e1610 y(C]C), 1505 y
y(CeOeC), 972
d
3
604 (4.53), 332 (4.80). MALDI-TOF-MS, (m/z): Calculated: 1388.38;
Found: 1389.91[M þ H]þ.
2.5.2.6. Dimeric nickel(II) phthalocyanine (10). Solvent system for
column chromatography: Chloroform:methanol (100:7). Yield:
0.09 g, (16.1%), mp:>300 ꢂC (decomposition). Anal. Calc. for
C78H40N18O2Ni2: C, 67.95; H, 2.92; N,18.29; Found: C, 67.85; H, 2.82;
N, 18.41. FT-IR (KBr tablet) ymax/cmꢁ1: 3049
y
(AreCH), 2924-2845
(CH ¼ N), 1267e1244
(CH). 1H NMR (DMSO-d6), (
: ppm): 8.95 (bs, 2H,
y(aliph. CH), 1619e1604
(CeOeC), 976
y(C]C), 1501 y
y
d
d
CH ¼ N), 7.82e7.71 (m, 10H/AreH), 7.66e7.35 (bm, 18H/AreH),
2.5.2.1. Dimeric zinc(II) phthalocyanine (5). Solvent system for
column chromatography: Chloroform:methanol (100:3). Yield:
0.05 g, (8.8%), mp:>300 ꢂC (decomposition). Anal. Calc. for
C78H40N18O2Zn2: C, 67.30; H, 2.90; N, 18.11. Found: C, 67.41; H, 2.84;
7.17e6.92 (m, 10H/AreH). UVevis (DMSO): lmax/nm (log ): 671
3
(4.91), 605 (4.16), 341 (4.71). MALDI-TOF-MS, (m/z): Calculated:
1378.68; Found: 1424.54 [M þ 2Na]2þ
.
N, 18.19. FT-IR (KBr tablet) ymax/cmꢁ1: 3053
y
(AreCH), 2922e2851
(CH ¼ N), 1277e1249
(CH). 1H NMR (DMSO-d6), (
: ppm): 8.97 (s, 2H,
3. Results and discussion
y
y
(aliph. CH), 1616e1607
(CeOeC), 987
y(C]C), 1507 y
d
d
3.1. Outlook of the synthesized compounds
CH ¼ N), 7.92e7.85 (m, 10H/AreH), 7.72e7.61 (bd, 8H/AreH),
7.52e7.38 (m, 10H/AreH), 7.11e6.89 (m, 10H/Ar-H). UVevis
The synthesis route of 4,40-(2,20-(1E,1’E)-hydrazine-1,2-
diylidenebis(methan-1-yl-1-ylidene)bis(2,1-phenylene))bis(oxy)
diphthalonitrile (3) and its target binuclear metallophthalocyanine
complexes (5, 6, 7, 8, 9 and 10) is shown in Fig. 1. The structures of
new compounds have been characterized by a combination of 1H
and 13C NMR (for phthalonitrile compound), FT-IR, UVeVis spec-
troscopy, elemental analysis and mass spectral data.
(DMSO): lmax/nm (log
3 ): 672 (5.03), 609 (4.23), 341 (4.53).
MALDI-TOF-MS, (m/z): Calculated: 1392.08; Found: 1393.42
[M þ H]þ.
2.5.2.2. Dimeric oxotitanium(IV) phthalocyanine (6). Solvent
system for column chromatography: Chloroform:methanol (100:7).

R. Bayrak et al. / Dyes and Pigments 95 (2012) 330e337
333
Generally, many researchers use substituted phthalonitrile or
1,3-diimino-1H-isoindoles to prepare phthalocyanines by cyclo-
tetramerization [44,45]. Base catalyzed nucleophilic aromatic nitro
substitution reaction of 4-nitrophthalonitrile has been achieved by
many authors [46,47]. In general, nucleophilic displacement of
a nitro group from an activated aromatic substrate can be effec-
tively achieved by a variety of strong nucleophiles under dipolar
aprotic solvents for example in DMF or DMSO [48,49].
In this respect, we prepared phthalonitrile derivative 3 from the
reaction of 4,40-(1E,1’E)-hydrazine-1,2-diylidenebis(methan-1-yl-
1-ylidene)diphenol (1) with 4-nitrophthalonitrile (2) in the pres-
ence of anhydrous K2CO3 as basic catalyst under N2 atmosphere at
55 ꢂC in schlenk system for 5 days in DMF. In the FT-IR spectrum of
this compound, the absence of eOH stretching/deformation of
compound 1 and the presence of C^N absorption band at
2227 cmꢁ1 clearly proves the formation of compound 3. In the 1H
NMR spectrum of 3, OH group of compound 1 disappeared as
expected. In the mass spectrum of compound 3, the presence of
molecular ion peaks at m/z ¼ 493.61 [M þ H]þ, confirmed the
proposed structures.
The dimeric metallophthalocyanine complexes (5e10) were
synthesized by statistical cross-condensation of a 1:6.13 M ratio of
phthalonitriles 3 and 4 and corresponding metal salts in the pres-
ence of DBU by heating under reflux for 24 h in n-pentanol. For
SnPcs, the reaction of phthalonitrile with SnCl2 may produce Sn(II)
Pc or Cl2Sn(IV)Pc species. The amount of SnCl2 used in the reaction
determines the type of the product. The Sn(II)Pc derivatives can be
prepared by the use of excess amount of SnCl2. In this study, Sn(II)
Pc derivative was synthesized in the presence of excess amount of
SnCl2 [50].
they will give a mixture of the symmetric Pc (AAAA), and the
desired asymmetric Pc (AAAB) and other cross-condensation
products [53,54]. In our research, excess of phthalonitrile (A) was
used in the reaction media, so there were mixture of mainly two
products; unsubstituted symmetric Pc (AAAA) and desired asym-
metric Pc (AAAB). It is known that the solubility of unsubstituted Pc
(AAAA) in common organic solvents is very low. The crude product
washed with chloroform and then filtered off for separating the
formed unsubstituted Pc derivatives. The filtrate was evaporated
and purified by column chromatography [55].
The spectroscopic characterization of the newly synthesized
phthalocyanine compounds includes 1H NMR, FT-IR, UV/Vis and
mass spectral methods, and the results are in accordance with the
proposed structures. The products (5e10) obtained by the cyclo-
tetramerization reaction of phthalodinitrile 3 and phthalonitrile 4
were confirmed in their FT-IR spectra by the disappearance of the
sharp C^N vibration at around 2227 cmꢁ1. The rest of the spectra of
Pcs were similar to that of 3. The 1H NMR spectra of 8 and 9 could
not be determined because of the presence of paramagnetic cobalt
and copper atoms in the cavity [56]. The 1H NMR spectra of other
MPcs (5, 6, 7 and 10) were not very different than that of the
compound 3 except the broadness of the signals because of prob-
able aggregation at the concentration for NMR measurements [57].
In the mass spectra of compounds 5e10, the parent molecular ion
peaks were observed at m/z ¼ 1393.42 [M þ H]þ for 5, 1389.90
[M þ H]þ for 6, 1566.76 [M þ 4OH]þ for 7, 1402.59 [M þ Na]þ for 8,
1389.91[M þ H] for 9 and 1424.59 [M þ 2Na]þ for 10, these peaks
have verified the proposed structures.
3.2. UVeVis absorption spectra and aggregation studies
Generally, statistical cross-condensations of phthalonitriles are
used to prepare different asymmetrical Pcs. However, this method
gives the mixture of phthalocyanines [51,52]. According to the
statistical considerations, if two phthalonitrile compounds (A and
B) having same chemical reactivity react together in the ratio of 3:1,
The electronic spectra of the phthalocyanine complexes (5e10)
showed characteristic absorption in the Q band region at around
656e691 nm in DMSO, Table 1. The B-bands were observed at
around 325e341 nm. The spectra showed monomeric behavior for
NC
NC
HO
CN
CN
N
2
O
N
N
N
3
6
O2N
CN
OH
O
1
CN
2
4
NC
NC
ii
N
N
N
N
N
O
N
N
M
N
N
N
N
O
N
M
N
N
N
N
N
N
7
9
5
6
8
10
Ni
Zn
Sn
OTi
Co Cu
M
Fig. 1. Synthetic route of novel phthalocyanine compounds. (i) dry DMF, anhydrous K2CO3, N2, 5 days, 55 ꢂC. (ii) dry n-pentanol, DBU, N2, Zn(OAc)2, Ti(BuO)4, SnCl2, CoCl2, CuCl2 or
Ni(OAc)2.

334
R. Bayrak et al. / Dyes and Pigments 95 (2012) 330e337
Table 1
800
0.3
0.25
0.2
0.15
0.1
0.05
0
Absorption, excitation and emission spectral data for unsubstituted zinc(II) (Std-
ZnPc) binuclear zinc(II) (5), oxotitanium(IV) (6), tin(II) (7), cobalt(II) (8), copper(II)
(9) and nickel(II) (10) phthalocyanine complexes in DMSO.
600
400
200
0
Compound
Q band lmax
(nm)
,
log
3
Excitation
lEx, (nm)
Emission
lEm, (nm)
Stokes shift
DStokes, (nm)
5
6
7
8
672
689
691
656
670
671
672
5.03
4.91
4.96
5.27
5.24
4.91
5.14
673
689
690
e
680
699
693
e
7
10
3
Excitation
Absorption
e
Emission
9
e
e
e
10
e
e
e
ZnPca
672
682
10
a
Data from ref. [63].
500
600
700
800
Wavelength (nm)
studied Pc complexes evidenced by a single (narrow) Q band,
typical of metalated Pc complexes [58]. The Q band of the tin(II)
phthalocyanine complex (7) was red-shifted when compared to the
corresponding other studied phthalocyanine complexes in DMSO,
suggesting that the non-planar effect of the bigger lead as central
metal atom. The B-bands were broad due to the superimposition of
the B1 and B2 bands in the w320e340 nm regions.
In this study, the aggregation behaviors of studied phthalocya-
nine complexes (5e10) were also investigated at different
concentrations in DMSO. The BeereLambert law was obeyed for all
of these complexes at concentrations ranging from 1.2 ꢀ 10ꢁ5 to
2 ꢀ 10ꢁ6 M. All the studied phthalocyanine complexes did not show
aggregation at these concentrations ranging in DMSO (Fig. 2).
Fig. 3. Absorption, excitation and emission spectra of the complex 5 in DMSO. (Exci-
tation wavelength ¼ 673 nm).
excitation spectra for zinc(II) (5) and oxotitanium(IV) (6) phthalo-
cyanine complexes suggest that the nuclear configurations of the
ground and excited states are similar and not affected by excitation.
For studied tin(II) phthalocyanine complex (7), the shape of exci-
tation spectrum was different from the absorption spectrum in that
the Q band of the excitation was observed as a split band in DMSO.
This suggests that there are changes in the molecules following
excitation most likely due to loss of symmetry, or change in
aggregation status following excitation. Thus, the Q band maxima
of the excitation and absorption spectra were different due to the
differences in the ground and excited state species. The difference
in the behavior of tin(II) phthalocyanine complex (7) on excitation
could be due to the larger tin metal being more displaced from the
core of the Pc ring, and the displacement being more pronounced
on excitation hence a loss of symmetry.
3.3. Fluorescence spectra
Fig. 3 shows fluorescence emission, absorption and excitation
spectra of complex 5 in DMSO as an example for the studied
phthalocyanine complexes. Fluorescence emission peak values
were listed in Table 1. The observed Stokes shifts were 10 nm for
complex 5, 7 nm for complex 6 and 3 nm for complex 7 in DMSO.
Zinc(II) (5) and oxotitanium(IV) (6) phthalocyanine complexes
showed similar fluorescence behavior in DMSO (Fig. 3 as an
example for complex 5). The excitation spectra were similar to
absorption spectra and both were mirror images of the fluorescent
spectra for zinc(II) (5) and oxotitanium(IV) (6) phthalocyanine
complexes in DMSO. The proximity of the wavelength of each
component of the Q band absorption to the Q band maxima of the
3.4. Fluorescence quantum yields and lifetimes
The fluorescence quantum yield (FF) values of zinc(II) (5) and
oxotitanium(IV) (6) phthalocyanine complexes were similar but the
FF value of tin(II) phthalocyanine complex (7) was lower than these
complexes (Table 2). The FF values of the binuclear phthalocyanine
complexes (5e7) were lower compared to unsubstituted zinc(II)
phthalocyanine (Std-ZnPc) in DMSO. The FF value of the tin(II)
phthalocyanine complex (7) was the lowest among the studied Pc
complexes could be due to heavy metal effect of tin.
3.2
Lifetimes of fluorescence (sF, Table 2) were calculated using the
3.5
3
2.5
2
2
1.5
1
0.5
0
2.8
StricklereBerg equation. Using this equation, a good correlation has
been found for the experimentally determined fluorescence life-
times and the theoretically determined lifetimes for the unag-
gregated molecules as is the case in this work [36]. Thus we believe
A
B
C
D
E
F
y = 254121x
R
= 0.9982
2.4
2
0.00E+00
5.00E-06
1.00E-05
1.50E-05
1.6
1.2
0.8
0.4
0
Concentration (M)
Table 2
Photophysical and photochemical data for unsubstituted zinc(II) (Std-ZnPc) binu-
clear zinc(II) (5), oxotitanium(IV) (6) and tin(II) (7) phthalocyanine complexes in
DMSO.
Compound FF
sF (ns)
s
0 (ns) akF (sꢁ1) (x108) Fd (x10ꢁ5
)
FD
5
6
7
0.17
1.04
0.64
0.10
6.14
5.30
5.45
6.80c
1.62
1.89
1.83
1.47c
1.10
3.11
0.40
0.55
0.59
0.67d
0.12
0.02
44.35
300
400
500
600
700
800
ZnPc
0.20b 1.22c
2.61c
Wavelength (nm)
a
kF is the rate constant for fluorescence. Values calculated using kF
Data from Ref. [37].
Data from Ref. [63].
¼
FF/sF.
b
c
Fig. 2. Absorption spectral changes for complex 7 in DMSO at different concentrations:
12 ꢀ 10ꢁ6 (A), 10 ꢀ 10ꢁ6 (B), 8 ꢀ 10ꢁ6 (C), 6 ꢀ 10ꢁ6 (D), 4 ꢀ 10ꢁ6 (E), 2 ꢀ 10ꢁ6 (F) M.
(Inset: Plot of absorbance versus concentration).
d
Data from Ref. [42].

R. Bayrak et al. / Dyes and Pigments 95 (2012) 330e337
335
that the values which obtained using this equation are a good
measure of fluorescence lifetimes.
The F values were within the range reported for MPc complexes
[59,60]. The F values were lower for zinc(II) (5), oxotitanium(IV) (6)
and tin(II) (7) phthalocyanine complexes when compared to
unsubstituted zinc(II) phthalocyanine (Std-ZnPc) (Table 2) sug-
gesting quenching of fluorescence by the ring substituents.
However, the sF values are typical for zinc(II) (5) and oxotitaniu-
m(IV) (6) phthalocyanine complexes [59,60]. The sF values of
zinc(II) (5) and oxotitanium(IV) (6) phthalocyanine complexes were
higher than tin(II) (7) complex because of the tin is heavy atom,
Table 2.
2.1
1.8
1.5
1.2
0.9
0.6
0.3
0
0 sec
s
300 sec
600 sec
900 sec
1200 sec
1500 sec
s
The rate constants for fluorescence (kF) values of zinc(II) (5),
oxotitanium(IV) (6) and tin(II) (7) phthalocyanine complexes were
higher than unsubstituted zinc(II) phthalocyanine (Std-ZnPc). The
300
400
500
600
700
800
Wavelength (nm)
natural radiative lifetime (s0) value of studied zinc(II) (5) phthalo-
Fig. 5. Absorption changes during the photodegradation studies of compound 7 in
DMSO showing the disappearance of the Q band at 10 min intervals. (Inset: Plot of
absorbance versus time).
cyanine was longer than for the other complexes (6, 7 and Std-
ZnPc) in DMSO. The s0 values among substituted complexes
decrease as follows: 5 > Std-ZnPc > 7 > 6, Table 2.
binuclear zinc(II) Pc complex (5) was lower than other Pc
complexes (6 and 7).
3.5. Singlet oxygen quantum yields
The quantity of the singlet oxygen quantum yield (FD) is a sign
of the capability of the compounds as photosensitizers in photo-
catalytic applications for instance PDT. The FD values were deter-
mined in DMSO using a chemical method and DPBF used as
a quencher. The disappearance of DPBF absorbance at 417 nm was
monitored using by UVevis spectrophotometer (Fig. 4 for complex
5 as an example).
Energy transfer between the triplet state of photosensitizers and
ground state molecular oxygen cause to generation of singlet
oxygen. There is a necessity of high efficiency of transfer of energy
between excited triplet state of MPc and ground state of oxygen to
generate large amounts of singlet oxygen, essential for PDT. The
singlet oxygen quantum yields (FD), give an indication of the
potential of the complexes as photosensitizers in applications
where singlet oxygen is required such as Type II mechanism.
There were no changes in the Q band intensities during the FD
determinations, confirming that complexes were not degraded
during singlet oxygen studies (Fig. 4 as an example for complex 5).
The FD values of the newly synthesized phthalocyanine complexes
(5e7) were given in Table 2. All studied Pc complexes showed lower
FD values than unsubstituted zinc (II) Pc complex (Std-ZnPc) in
DMSO. The tin(II) phthalocyanine complex (7) showed the highest
FD value among the studied Pc complexes (Table 2). The FD value of
3.6. Photodegradation studies
Photodegradation is the oxidative degradation that a photosen-
sitizer molecule is allocated to over time lower molecular weight
fragments under light [43]. Photodegradation is related to the
concentration of the molecule, structure, light intensity and
solvent. Photodegradation is a singlet oxygen mediated process, as
singlet oxygen has highly reactive and capability reacts with
phthalocyanines [61]. Largely, phthalimide residual was found to be
the photooxidation crop following degradation of phthalocyanines
[62]. The stability of Pc complexes are low when the photo-
degradation quantum yield values are high. This property makes
them suitable for use as photocatalysts (such as photosensitizers).
The spectral changes observed for all studied complexes (5e7)
during light irradiation are as shown in Fig. 5 (using complex 7 as
an example in DMSO) and hence confirm photodegradation
occurred without phototransformation. The Fd values, found in this
study, are similar to Pc derivatives having different metals and
substituents on the Pc ring in literature [59,60]. Stable studied Pc
molecules show Fd values as low as 10ꢁ6 and for unstable mole-
cules, values of the order of 10ꢁ3 have been reported [59]. Table 2
shows that studied oxotitanium(IV) (6) and tin(II) (7) phthalocya-
nine complexes were less stable to degradation under light irradi-
ation compared to unsubstituted (Std-ZnPc) and substituted (5)
zinc Pc complexes in DMSO. The tin(II) phthalocyanine complex (7)
was least stable when compared to the other studied binuclear
complexes (5 and 6) due to the larger tin metal being more dis-
placed from the core of the Pc ring.
1.4
1.2
0 sec
5 sec
1
0.8
0.6
0.4
0.2
0
10 sec
15 sec
20 sec
4. Conclusion
In the presented work, the synthesis of new binuclear zinc(II),
oxotitanium(IV), tin(II), cobalt(II), copper(II) and nickel(II) (5e10)
phthalocyanine complexes were described and these new
complexes were characterized by elemental analysis, FT-IR, 1H
NMR, 13C NMR (for compound 3), UVeVis and mass spectra.
Aggregation behaviors of all studied complexes were investigated
in DMSO at different concentrations. The spectra showed mono-
meric behavior evidenced by a single (narrow) Q band, typical of
metalated phthalocyanine complexes at concentration range
1.2 ꢀ 10ꢁ6e2 ꢀ 10ꢁ6 M. The Q band of the tin(II) phthalocyanine
complex (7) was red-shifted in DMSO due to the non-planar effect
300
400
500
600
700
800
Wavelength (nm)
Fig. 4. Absorption changes during the determination of singlet oxygen quantum yield.
This determination was for compound 5 in DMSO at a concentration of 1 ꢀ 10ꢁ5 M.
(Inset: Plot of DPBF absorbance versus time).

336
R. Bayrak et al. / Dyes and Pigments 95 (2012) 330e337
phthalocyanine conjugated with a butadiyne linker. J Fluorine Chem 2009;
130:1164e70.
of the bigger tin as central atom. The photophysical and photo-
chemical properties of newly synthesized phthalocyanine
complexes (5e7) were also described in DMSO for comparison of
the effect of metal atoms on the Pc framework. Binuclear zinc(II) (5)
and oxotitanium(IV) (6) phthalocyanine complexes showed similar
and typical fluorescence behavior in DMSO. But the shape of exci-
tation spectrum was different from the absorption spectrum for
studied binuclear tin(II) phthalocyanine complex (7) in DMSO. The
fluorescence quantum yield (FF) values of binuclear zinc(II) (5) and
oxotitanium(IV) (6) phthalocyanine complexes were found similar
but the FF value of binuclear tin(II) phthalocyanine complex (7) was
lower than these complexes. The difference in the behavior of tin(II)
phthalocyanine complex (7) on excitation could be due to the larger
tin metal being more displaced from the core of the Pc ring. The sF
values were found lower for binuclear phthalocyanine complexes
(5e7) when compared to respective unsubstituted zinc phthalo-
cyanine (Std-ZnPc). The sF values of binuclear zinc(II) (5) and
oxotitanium(IV) (6) phthalocyanine complexes were found higher
than binuclear tin(II) phthalocyanine complex (7) in DMSO because
of the tin is heavy metal. All newly synthesized binuclear phtha-
locyanine complexes (5e7) showed lower FD values than unsub-
stituted zinc (II) Pc complex (Std-ZnPc) in DMSO but the singlet
oxygen generation of these phthalocyanine complexes still enough
for photocatalytic application such as PDT. Generally, the Fd values
of studied binuclear phthalocyanine complexes (5e7) were similar
to MPc complexes.
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