Self-assembling novel phthalocyanines containing a rigid benzothiazole skeleton with a 1,4-benzene linker: Synthesis, spectroscopic and spectral properties, and photochemical/photophysical affinity

Article abstract of DOI:10.1016/j.poly.2012.08.074

A novel benzothiazole containing phthalonitrile derivative and its peripherally tetra substituted metal free (4), Ni(II) (5), Zn(II) (6), Cu(II) (7) and Ti(IV) (8) phthalocyanines have been synthesized. The novel compounds were characterized by elemental analysis, IR, UV-Vis, ¹H NMR, ¹³C NMR and mass spectroscopy. Zn(II)Pc (6) showed monomeric behavior in THF up to 7 × 10^-5 mol dm^-3 concentration and in various solvents (pyridine, dichloromethane, DMF and DMSO) up to 4 × 10^-5 mol dm^-3 concentration. On the other hand, Cu(II)Pc (7) formed aggregates in THF at concentrations higher than 3.6 × 10 ^-5 mol dm^-3 and showed monomeric behavior in THF, DMF and DMSO at 2.4 × 10^-5 mol dm^-3. Furthermore, the photochemical and photophysical properties of the metal free (4), Zn(II) (6) and Ti(IV) (8) phthalocyanines were investigated in THF. All the investigated phthalocyanines showed similar fluorescence behavior in THF. The synthesized Ni(II) (5) and Cu(II) (7) phthalocyanines were not evaluated for this purpose because of the paramagnetic behavior of the central metals in the cavity of these complexes. Singlet oxygen generation properties of these phthalocyanine compounds were also investigated and the order of singlet oxygen quantum yields were found as: Zn(II) Pc (6) > Ti(IV) Pc (8) > unsubstituted Zn(II) Pc (ZnPc) > metal free Pc (4). The degradation of the studied compounds was studied under light irradiation and the oxotitanium (IV) phthalocyanine derivative was found to be very sensitive to light irradiation. The fluorescence quenching behavior of the studied novel peripherally tetra 4-(1,3-benzothiazol- 2-yl)phenoxy substituted metal free (4), Zn(II) (6) and Ti(IV) (8) phthalocyanines by the addition of 1,4-benzoquinone was also studied.

Full text of DOI:10.1016/j.poly.2012.08.074

Polyhedron 48 (2012) 80–91
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Self-assembling novel phthalocyanines containing a rigid benzothiazole skeleton
with a 1,4-benzene linker: Synthesis, spectroscopic and spectral properties, and
photochemical/photophysical affinity
a
b
a,
⇑
_
Ayßse Aktaßs , Mahmut Durmusß , Ismail Deg˘irmenciog˘lu
a Department of Chemistry, Faculty of Sciences, Karadeniz Technical University, 61080 Trabzon, Turkey
b 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:
Received 13 July 2012
Accepted 10 August 2012
Available online 13 September 2012
A novel benzothiazole containing phthalonitrile derivative and its peripherally tetra substituted metal
free (4), Ni(II) (5), Zn(II) (6), Cu(II) (7) and Ti(IV) (8) phthalocyanines have been synthesized. The novel
compounds were characterized by elemental analysis, IR, UV–Vis, 1H NMR, 13C NMR and mass spectros-
copy. Zn(II)Pc (6) showed monomeric behavior in THF up to 7 ꢀ 10ꢁ5 mol dmꢁ3 concentration and in var-
ious solvents (pyridine, dichloromethane, DMF and DMSO) up to 4 ꢀ 10ꢁ5 mol dmꢁ3 concentration. On
the other hand, Cu(II)Pc (7) formed aggregates in THF at concentrations higher than 3.6 ꢀ 10ꢁ5 mol dmꢁ3
and showed monomeric behavior in THF, DMF and DMSO at 2.4 ꢀ 10ꢁ5 mol dmꢁ3. Furthermore, the pho-
tochemical and photophysical properties of the metal free (4), Zn(II) (6) and Ti(IV) (8) phthalocyanines
were investigated in THF. All the investigated phthalocyanines showed similar fluorescence behavior
in THF. The synthesized Ni(II) (5) and Cu(II) (7) phthalocyanines were not evaluated for this purpose
because of the paramagnetic behavior of the central metals in the cavity of these complexes. Singlet oxy-
gen generation properties of these phthalocyanine compounds were also investigated and the order of
singlet oxygen quantum yields were found as: Zn(II) Pc (6) > Ti(IV) Pc (8) > unsubstituted Zn(II) Pc
(ZnPc) > metal free Pc (4). The degradation of the studied compounds was studied under light irradiation
and the oxotitanium (IV) phthalocyanine derivative was found to be very sensitive to light irradiation.
The fluorescence quenching behavior of the studied novel peripherally tetra 4-(1,3-benzothiazol-2-
yl)phenoxy substituted metal free (4), Zn(II) (6) and Ti(IV) (8) phthalocyanines by the addition of 1,4-
benzoquinone was also studied.
Keywords:
Phthalocyanine
Benzothiazole
Aggregation
Photophysics
Photochemistry
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
widely used for the preparation of anti-inflammatory drugs and
analgesics [8], organic optoelectronic materials, second-order
Phthalocyanines (Pcs) have been under systematic study for
more than 70 years due to their glorious functional properties
[1]. Pcs are used in a number of applications due to their high
stability, diverse coordination properties and improved spectro-
scopic characteristics. Possible application areas of Pcs are electro-
photography, molecular electronics, photovoltaic and solar cells,
Langmuir–Blodgett films, gas sensors, electrochromic display
devices, NLO, optical discs and photosensitizers in photodynamic
therapy of cancer (PDT) [2,3].
On the other hand, nitrogen and sulfur containing aromatic
heterocyclic compounds, called benzothiazole and its derivatives,
are very important species [4]. They are popular molecules due
to their pharmaceutical and biological activities, such as antitumor
[5], local anesthetic [6], antimicrobial [7] and antiglutamate/
antiparkinson agents. Recently, these compounds have been
non-linear optical (NLO) materials [9], calcium channel antagonists
[10], liquid crystals [11], fluorophores [12], inhibitors of several
enzymes, azo dyes [13,14] and corrosion inhibitors [15–17].
Pcs are useful photosensitizers due to their high molar absorp-
tion coefficients, long lifetimes of the photoexcited triplet states
and photostabilities [18,19]. One of the most important problems
related to Pcs is their low solubility in common organic solvents,
such as chloroform, methanol, acetone, THF, diethylether and ethyl
acetate. Their insolubility does not allow scientists to investigate
them. Locating bulky groups or long alkyl, alkoxy or alkylthio
chains to peripheral areas or quaternary ion formation enhances
the solubility of phthalocyanine products in many solvents [20].
In view of the biological importance of both benzothiazoles and
phthalocyanines, it is worthwhile to combine these two functional
structures into a single compound.
In the last decade, microwave heating technology has arisen as
a strategic alternative to thermal energy due to advantages such as
selectivity, rapidity in heating and cooling, decreased reaction
⇑
Corresponding author. Tel.: +90 462 3773321; fax: +90 462 3253196.
E-mail address: ismail61@ktu.edu.tr (I. Deg˘irmenciog˘lu).
_
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.08.074

A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
81
in DMSO. The absorbance of the solutions at the excitation wave-
length ranged between 0.04 and 0.05.
time, increased yields and easy improved controllability [21–23].
From this perspective, microwave assisted synthesis of phthalocy-
anines is even more important [23–25].
Natural radiative lifetimes (s0) were determined using the Pho-
tochemCAD program [31] which uses the Strickler–Berg equation.
The fluorescence lifetimes (sF) were evaluated using Eq. (2).
In this study, the synthesis, characterization and structural
investigation of metal-free and Ni(II), Zn(II), Cu(II) and Ti(IV)
metallo phthalocyanines containing nitrogen, sulfur and oxygen
donor atoms on the periphery are described. They are discussed
below on the basis of their spectroscopic characteristics. The
photophysical and photochemical properties of the novel metal-
free (4), Zn(II) (6) and Ti(IV) (8) phthalocyanines were also investi-
gated in THF and results are compared.
sF
s0
UF
¼
ð2Þ
2.4. Photochemical parameters
2.4.1. Singlet oxygen quantum yields
Singlet oxygen quantum yield (UD) determinations were car-
ried out using the experimental set-up described in the literature
[32–34] in THF. Typically, a 3 mL portion of the respective substi-
tuted phthalocyanine (metal-free (4), Zn(II) (6) and Ti(IV) (8)) solu-
tions (C = 1 ꢀ 10ꢁ5 M) containing the singlet oxygen quencher was
irradiated in the Q band region with the photo-irradiation set-up
described in the references [32–34].
Singlet oxygen quantum yields (UD) were determined in air
using the relative method with unsubstituted ZnPc (in THF) as
the reference. DPBF was used as a chemical quencher for singlet
oxygen in THF. Eq. (3) was employed for the calculations:
2. Experimental
2.1. Materials
4-(1,3-Benzothiazol-2-yl)phenol (1) [26] and 4-nitrophthalonit-
rile (2) [27] were prepared according to literature procedures. All
reactions were carried out under an atmosphere of dry, oxygen-
free nitrogen, using standard Schlenk techniques. All solvents were
dried and purified as described by Perrin and Armarego [28].
2.2. Equipment
Std
R ꢂ I
1H NMR and 13C NMR spectra were recorded on a Varian XL-200
NMR spectrophotometer in CDCl3, and chemical shifts are reported
(d) relative to Me4Si as an internal standard. FT-IR spectra were re-
corded on a Perkin–Elmer Spectrum one FT-IR spectrometer using
KBr pellets. The mass spectra were measured with a Micromass
Quattro LC/ULTIMA LC-MS/MS spectrometer equipped with chlo-
roform–methanol as the solvent. All experiments were performed
in the positive ion mode. Elemental analyses were performed on
a Costech ECS 4010 instrument and the obtained values agreed
with the calculated ones. A Beko MD 1500, 2.45 MHz domestic
microwave oven was used in the synthesis of all the phthalocya-
nines, except for metal-free and Ti(IV) Pc. Melting points were
measured on an electrothermal apparatus and were uncorrected.
UV–Vis spectra were recorded by means of Unicam UV2-100 and
Shimadzu 2101 UV–Vis spectrophotometers, using 1 cm path
length cuvettes at room temperature. Fluorescence excitation and
emission spectra were recorded on a Varian Eclipse spectrofluo-
rometer using 1 cm path length cuvettes at room temperature.
A General Electric quartz line lamp (300 W) was used for photo-
irradiation studies. A 600 nm glass cut off filter (Intor) and a water
filter were used to filter off ultraviolet and infrared radiations,
respectively. An interference filter (Intor, 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 (Molelectron Detector Incorporated) power meter.
USDtd
ð3Þ
abs
UD
¼
RStd ꢂ Iabs
where USDtd is the singlet oxygen quantum yield for the standard
unsubstituted ZnPc (UDStd = 0.53 in THF) [35]. R and RStd are the DPBF
photobleaching rates in the presence of the respective samples
(metal-free (4), Zn(II) (6) and Ti(IV) (8) phthalocyanines) and stan-
dards, respectively. Iabs and IStd are the rates of light absorption by
abs
the samples and standard, respectively. To avoid chain reactions in-
duced by DPBF in the presence of singlet oxygen [36], the concen-
tration of the quencher was lowered to ꢃ3 ꢀ 10ꢁ5 M. Solutions of
sensitizer (1 ꢀ 10ꢁ5 M) containing DPBF was prepared in the dark
and irradiated in the Q band region using the setup described above.
DPBF degradation at 417 nm was monitored. A light intensity of
6.39 ꢀ 1015 photons sꢁ1 cmꢁ2 was used for UD determinations.
2.4.2. Photodegradation quantum yields
Photodegradation quantum yield (Ud) determinations were car-
ried out using the experimental set-up described in the literature
[32–34]. Photodegradation quantum yields were determined using
Eq. (4),
ðC0 ꢁ CtÞ ꢂ V ꢂ NA
Ud
¼
ð4Þ
Iabs ꢂ S ꢂ t
where C0 and Ct are the sample (metal-free (4), Zn(II) (6) and Ti(IV)
(8) phthalocyanines) concentrations before and after irradiation
respectively, V is the reaction volume, NA is Avogadro’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 2.13 ꢀ 1016 pho-
tons sꢁ1 cmꢁ2 was employed for Ud determination.
2.3. Photophysical parameters
2.3.1. Fluorescence quantum yields and lifetimes
Fluorescence quantum yields (UF) were determined by the
comparative method using Eq. (1) [29].
F ꢂ AStd ꢂ n2
UF
¼
UFðStdÞ
ð1Þ
2.4.3. Fluorescence quenching studies by 1,4-benzoquinone [BQ]
Fluorescence quenching experiments on the substituted phtha-
locyanine compounds (metal-free (4), Zn(II) (6) and Ti(IV) (8))
were carried out by the addition of different concentrations of
BQ to a fixed concentration of the compounds, and the concentra-
tions of BQ in the resulting mixtures were 0, 0.008, 0.016, 0.024,
0.032 and 0.040 M. The fluorescence spectra of the substituted
phthalocyanine compounds at each BQ concentration were
recorded, and the changes in fluorescence intensity were related
FStd ꢂ A ꢂ n2Std
where F and FStd are the areas under the fluorescence emission
curves of the samples (metal-free (4), Zn(II) (6) and Ti(IV) (8)
phthalocyanines) and the standard, respectively. A and AStd are
the respective absorbances of the samples and standard at the exci-
tation wavelengths, respectively. n and nStd are the refractive indi-
ces of solvents used for the sample and standard, respectively.
Unsubstituted ZnPc (UF = 0.20) [30] was employed as the standard

82
A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
to the BQ concentration by the Stern–Volmer (SV) equation [37]
(Eq. (5)):
Ar–Hc,d(d )). 13C NMR (CDCl3), (d, ppm): 173.99 (C3–NS), 168.01
(C1–O), 161.51 (C2–O), 158.0 (C4–N), 156.01 (C5–S), 154.32
(Cisoiminoindoline), 146.12, 140.0, 138.55, 135.21, 131.11, 129.81,
127.19, 126.60, 125.50, 123.44, 121.93, 107.89. UV–Vis (THF)
0
I0
¼ 1 þ KSV½BQꢄ
ð5Þ
I
kmax/nm [(10ꢁ5 log dm3 molꢁ1 cmꢁ1)]: 320(4.36), 607(3.63),
e
where I0 and I are the fluorescence intensities of the fluorophore in
the absence and presence of quencher, respectively. KSV is the
Stern–Volmer constant, and this is the product of the bimolecular
quenching constant (kq) and the fluorescence lifetime sF (Eq. (6)):
644(3.86), 663(4.23), 697(4.30). MS (ESI), (m/z): Calculated:
1414.26; Found: 1415.89 [M+H]+.
2.5.3. Ni(II) phthalocyanine (5)
A mixture of compound 3 (100 mg, 0.283 mmol), anhydrous
Ni(CH3COO)2 (12.5 mg, 0.071 mmol), dry DMAE (3 ml) and 1,8-dia-
zabycyclo[5.4.0]undec-7-ene (DBU) (0.067 ml, 0.44 mmol) was
irradiated in a microwave oven at 1000 W for 15 min. Then the
mixture was diluted with hot methyl alcohol and stirred for
12 h. The product was filtered and then washed with hot methyl
alcohol, diethyl ether and dried in vacuum over P2O5. Purification
of the solid crude product was accomplished by preparative silica-
gel plate (0.5 mm) with THF–chloroform (95:5) as eluents to give a
dark green powder. Crude yield: 40 mg (38.46%), after purification
of 25 mg, yield: 7.5 mg, (30%), mp: 210–213 °C (decomposition).
Anal. Calc. for C84H44N12O4S4Ni: C, 68.56; H, 2.99; N, 11.43; Ni,
3.99. Found: C, 68.85; H, 2.84; N, 11.77; Ni, 4.20. IR (KBr tablet)
KSV ¼ kqsF
ð6Þ
The ratios I0/I were calculated and plotted against [BQ] according to
Eq. (5), and KSV was determined from the slope.
2.5. Synthesis
2.5.1. 4-[4-(1,3-Benzothiazol-2-yl)phenoxy]phthalonitrile (3)
A
mixture of 4-(1,3-benzothiazol-2-yl)phenol (1) (500 mg,
2.2 mmol) and dry DMF (20 ml) was charged into a 100 ml one-
necked flask and stirred at room temperature under an inert nitro-
gen atmosphere. 4-Nitrophthalonitrile (2) (381 mg, 2.2 mmol) was
added to the solution and the temperature was increased up to 55–
60 °C. Powdered dry K2CO3 (456 mg, 3.3 mmol) was added to the
system in eight equal portions at 15 min intervals, with efficient
stirring, and the reaction system was stirred at the same tempera-
ture for 4 days. Aliquots were taken and checked periodically for
completeness of the reaction and observed by thin layer chroma-
tography (TLC) (chloroform). The reaction system was cooled and
poured into ice-water and then mixed for 24 h. The mixture was
filtered and dried in vacuum over P2O5 for 4 h and recrystallized
from ethanol to give a light orange crystalline powder. Yield:
67 mg, (86%), mp: 90–92 °C. Anal. Calc. for C21H11N3OS: C, 71.31;
H, 3.11; N, 11.88. Found: C, 71.43; H, 2.95; N, 11.53. IR (KBr tablet)
m
max/cmꢁ1: 3060 (Ar–CH), 1599–1514 (CH@N/C@C), 1472–1432
(@C–S), 1234–1164, 1093–1053 (@C–O–C). 1H NMR (CDCl3),
0
(d, ppm): 9.02–8.51 (m, 12H/Ar–He(e ),f), 8.24–8.18 (m, 8H/
Ar–Ha,b), 7.88–7.69 (m, 12H/Ar–Hi,g,h), 7.51–7.46 (m, 12H/
Ar–Hc,d(d )). 13C NMR (CDCl3), (d, ppm): 177.20 (C3–NS), 166.98
0
(C1–O), 161.42 (C2–O), 159.00 (C4–N), 156.19 (C5–S), 150.45
(Cisoiminoindoline), 144.71, 142.98, 140.27, 134.51, 127.69, 125.74,
124.54, 122.43, 121.51, 120.39, 115.0, 103.0. UV–Vis (THF)
kmax/nm [(10ꢁ5 log dm3 molꢁ1 cmꢁ1)]: 324(4.67), 613(4.04),
e
680(4.79). MS (ESI), (m/z): Calculated: 1470.18; Found: 1506.54
[M+2H2O]+.
m
max/cmꢁ1: 3044 (Ar–CH), 2232 (C„N), 1594–1562 (C@N/C@C),
1477–1434 (@C–S), 1087–1013 (C–O–C). 1H NMR (CDCl3), (d,
2.5.4. Zn(II) phthalocyanine (6)
0
ppm): 8.22–8.15 (dt, 2H/Ar–He(e ), J = 9.00 and 2.60 Hz), 8.10–8.05
A mixture of compound 3 (100 mg, 0.283 mmol), anhydrous
Zn(CH3COO)2 (12.9 mg, 0.071 mmol), dry DMAE (3 mL) and 1,8-
diazabycyclo[5.4.0]undec-7-ene (DBU) (0.166 ml, 1.09 mmol) was
irradiated in a microwave oven at 1000 W for 10 min. Then the
mixture was diluted with hot methyl alcohol and stirred for 12 h.
The product was filtered and then washed with hot methyl alcohol,
diethyl ether and dried in vacuum over P2O5. Purification of the so-
lid crude product was accomplished by preparative silicagel plate
(0.5 mm) with THF–chloroform (95:5) as eluents to give a dark
green powder. Crude yield: 71 mg, (67.98%), after purification of
25 mg, yield: 10 mg (40%), mp: 270-274 °C (decomposition). Anal.
Calc. for C84H44N12O4S4Zn: C, 68.28; H, 2.98; N, 11.38; Zn, 4.43.
(dt, 1H/Ar–Hf, J = 7.60 and 0.80 Hz), 7.95–7.91 (dt, 1H/Ar–Ha,
J = 7.80 and 0.80 Hz), 7.78–7.74 (d, 1H/Ar–Hb, J = 7.60 Hz), 7.56–
7.48 (td, 1H/Ar–Hi, J = 7.80 and 1.60 Hz), 7.46-7.41 (dd, 1H/Ar–Hg,
J = 7.60 and 1.60 Hz), 7.38–7.31 (dd, 1H/Ar–Hh, J = 7.40 and
0
1.80 Hz), 7.28–7.26 (m, 1H/Ar–Hc), 7.23–7.16 (dt, 2H/Ar–Hd(d )
,
J = 9.00 and 2.60 Hz). 13C NMR (CDCl3), (d, ppm): 166.23 (C3–NS),
160.92 (C1–O), 155.75 (C2–O), 154.02 (C4–N), 135.56 (C5–S),
135.06, 131.58, 129.89, 126.58, 125.53, 123.30, 122.09, 121.84,
121.72, 120.90, 117.81, 115.24 (C„N), 114.78 (C„N), 109.55. MS
(ESI), (m/z): Calculated: 353.40; Found: 353.97 [M]+.
2.5.2. Metal-free phthalocyanine (4)
Found: C, 67.93; H, 2.85; N, 11.88; Zn, 4.74. IR (KBr tablet) mmax/
A standart Schlenk tube was charged with (212 mg, 0.65 mmol)
of 3, 3 ml of N,N-dimethylaminoethanol (DMAE) and (0.23 ml,
1.51 mmol) of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) under a
nitrogen atmosphere. The reaction mixture was stirred at 160 °C
for 24 h. Then, the reaction mixture was cooled and evaporated
to dryness. The remaining dark green solid was stirred with methyl
alcohol for 24 h. The product was filtered and washed with hot
methyl alcohol and diethyl ether successively, and dried in vacuum
over P2O5. Purification of the solid crude product was accom-
plished by preparative silicagel plate (0.5 mm) with THF as the elu-
ent to give a dark green powder. Crude yield: 85 mg, (36.56%), after
purification of 25 mg, yield: 6.5 mg, (26%), mp: 230–233 °C
(decomposition). Anal. Calc. for C84H46N12O4S4: C, 71.27; H, 3.25;
N, 11.88. Found: C, 71.09; H, 3.53; N, 12.01. IR (KBr tablet)
cmꢁ1
: 3058 (Ar–CH), 1600 (C@N/C@C), 1480–1435 (@C–S),
1232–1165, 1088–1045 (@C–O–C). 1H NMR (CDCl3), (d, ppm):
8.03–7.26 (m, 44H/Ar–H). 13C NMR (CDCl3), (d, ppm): 177.12 (C3–
NS), 167.88 (C1–O), 161.32 (C2–O), 161.19 (C4–N), 158.17 (C5–S),
154.45 (Cisoiminoindoline), 147.61, 143.98, 142.17, 135.31, 129.79,
127.84, 126.64, 123.33, 121.91, 120.79, 113.0, 105.0. UV–Vis
(THF) kmax/nm [(10ꢁ5 log dm3 molꢁ1 cmꢁ1)]: 316(4.60),
e
613(3.87), 675(4.61). MS (ESI), (m/z): Calculated: 1476.18; Found:
1476.19 [M]+.
2.5.5. Cu(II) phthalocyanine (7)
A mixture of compound 3 (100 mg, 0.283 mmol), anhydrous
CuCl2 (9.5 mg, 0.071 mmol), dry DMAE (3 mL) and 1,8-diazabycy-
clo[5.4.0]undec-7-ene (DBU) (0.166 ml, 1.09 mmol) was irradiated
in a microwave oven at 1000 W for 15 min. Then the mixture was
diluted with hot methyl alcohol and stirred for 12 h. The dark
green product was filtered and then washed with hot methyl alco-
hol, diethyl ether and dried in vacuum over P2O5. Purification of
m
max/cmꢁ1: 3286 (–NH), 3050 (Ar–CH), 1600–1517 (CH@N/C@C),
1474, 1435 (@C–S), 1234–1165, 1092–1011 (@C–O–C). 1H NMR
0
(CDCl3), (d, ppm): 8.04–7.91 (m, 12H/Ar–He(e ),f), 7.89–7.80
(m, 8H/Ar–Ha,b), 7.39–7.27 (m, 12H/Ar–Hi,g,h), 7.24–6.99 (m, 12H/

A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
83
0
0
the solid crude product was accomplished by preparative silicagel
plate (0.5 mm) with THF–chloroform (95:5) as eluents to give a
dark green powder. Crude yield: 91 mg, (87%), after purification
of 25 mg, yield: 9.5 mg (38%), mp: 240–245 °C (decomposition).
Anal. Calc. for C84H44N12O4S4Cu: C, 68.33; H, 2.98; N, 11.39; Cu,
4.31. Found: C, 68.47; H, 3.24; N, 11.58; Cu, 4.08. IR (KBr tablet)
ABX spin system, as expected [43,44]. The Hd(d ) and He(e ) protons
have been split into a pseudo-doublet of triplets, instead of double
doublets, due to the long-range interactions, (meta and/or para
positioned couplings), therefore they were each not able to affect
the other sufficiently, as shown in Fig. 2 [43–45]. As a consequence
of the strong electron-withdrawing effect of the cyano group with
sp hybridisation and azomethine groups with sp2 hybridisation,
the lowest shifted signals at 8.15–8.22, 8.05–8.10, 7.91–7.95 and
7.74–7.78 ppm have been assigned to exterior aromatic protons
of the fragment with related terminal groups. Five sets of reso-
nances have been observed at 7.48–7.56, 7.41–7.46, 7.31–7.38,
7.26–7.28 and 7.16–7.23 ppm, integrating for five protons each,
making a total of 24 protons expected for the periphery protons
of each phthalocyanine ring. While the 1H NMR spectra of 1 and
3 are mostly similar, the proton-decoupled 13C NMR spectrum
indicates the presence of a nitrile carbon atom in 3 at d = 115.24
and 114.78 ppm. In addition, the mass spectrum of 3 shows a
molecular ion peak at m/z = 353.97 [M]+, supporting the proposed
formula for this compound.
m
max/cmꢁ1: 3044 (Ar–CH), 1601 (C@N/C@C), 1479–1429 (@C–S),
1234–1164, 1093–1043 (@C–O–C). UV–Vis (THF) kmax/nm [(10ꢁ5
loge
dm3 molꢁ1 cmꢁ1)]: 318(4.73), 612(3.87), 680(4.41). MS (ESI),
(m/z): Calculated: 1475.18; Found: 1521.16 [M+2Na]2+
.
2.5.6. Ti(IV) phthalocyanine (8)
A mixture of compound 3 (275 mg, 0.78 mmol), urea (23.3 mg,
0.39 mmol), and 1,8-diazabycyclo[5.4.0]undec-7-ene (DBU)
(0.17 ml, 1.12 mmol) were mixtured in dry n-amyl alcohol and
heated to 120 °C. At that temperature, titanium (IV) butoxide
Ti(OBu)4 (0.081 ml) was added through a syringe and the reaction
mixture was heated at reflux at 155 °C for 7 h. After cooling to
room temperature, the mixture was poured into n-hexane and
stirred for 12 h. Then the dark green product was filtered, washed
with hot diethyl ether and dried in vacuum over P2O5. Purification
of the solid crude product was accomplished by preparative silica-
gel plate (2 mm) with chloroform–methanol (95:5) as eluents to
give a dark green powder. Crude yield: 109 mg, (94%), after puri-
fication of 55 mg, yield: 14.0 mg (25.5%), mp: >300 °C (decompo-
sition). Anal. Calc. for C84H44N12O5S4Ti: C, 68.25; H, 2.98; N, 11.38;
Ti, 3.24. Found: C, 68.20; H, 3.05; N, 11.18; Ti, 3.32. IR (KBr tablet)
In a microwave oven, all attempts to obtain the metal free (4)
and Ti(IV) Pc (8) resulted in failure. So, the metal-free (4) and Ti(IV)
Pc (8) derivatives were obtained directly by the reaction of the
substituted phthalonitrile 3 with DMAE and DBU (1,8-diazabicy-
clo[5.4.0]undec-7-ene) [42] and of the substituted phthalonitrile
3 with dry n-amyl alcohol/urea/DBU/Ti(OBu)4 mixtures, respec-
tively. On the other hand, in the presence of metal salts, cyclotet-
ramerization of the phthalonitrile based on 1,3-benzothiazol 3
gave the metal phthalocyanines 5, 6, 7, and 8 [42,46,47]. In the
cases of 5, 6 and 7 metal salts, the solvent for the microwave-
assisted method was DMAE (N,N-dimethylaminoethanol), and for
8 the solvent was dry n-amyl alcohol. In addition, in the micro-
wave-assisted method, the reactions of 5, 6 and 7 were accom-
plished in DMAE/DBU mixtures at 1000 W in 15 min for Ni(II),
10 min for Zn(II) and 15 min for Cu(II), whereas in the classical
method, the reaction of 8 was accomplished in dry n-amyl alco-
hol/urea/DBU media after 7 h.
m
max/cmꢁ1: 3049 (Ar–CH), 1630 (C@N/C@C), 1474–1432 (@C–S),
1234–1163, 1067–1006 (@C–O–C), 965 (Ti@O). 1H NMR (CDCl3),
(d, ppm): 8.05–7.30 m, (44H/Ar–H). UV–Vis (THF) kmax/nm
[(10ꢁ5 log dm3 molꢁ1 cmꢁ1)]: 319(4.34), 611(4.66), 636(3.93),
e
666(4.19), 698(4.46). MS (ESI), (m/z): Calculated: 1476.91; Found:
1477.89 [M+H]+.
3. Results and discussion
The IR spectrum of the metal-free phthalocyanine 4 shows the
known classical –NH band (inner –NH) at 3286 cmꢁ1, as indicated
in previous reports [42,46–51]. The rest of the spectrum of 4 is sim-
ilar to that of 3, except for the C„N group in 3. The typical shielding
of the inner core protons belonging to metal-free phthalocyanines,
which are generally located in the negative ppm region were not
observed in the 1H NMR spectrum of compound 4 because of strong
aggregation of this compound in the solution at the NMR concen-
tration (especially, because of the crowded benzene moieties)
[52,53]. The signals related to aromatic groups in the macrocyclic
moieties and phthalocyanine skeleton gave a significant absor-
bance characteristic of the proposed structure. The mass spectrum
of 4 shows a molecular ion peak at m/z = 1415.89 [M+H]+, support-
ing the proposed formula of this compound.
On the other hand, the studied metallophthalocyanines (5, 6, 7
and 8) were obtained from the substituted phthalonitrile deriva-
tive 3 and the corresponding anhydrous metal salts Ni(CH3COO)2,
Zn(CH3COO)2, CuCl2 and Ti(OBu)4 respectively. In the IR spectra
of all the metallophthalocyanines, the disappearance of the strong
C„N stretching vibration of 3 at 2228 cmꢁ1 is an evidence for the
formation of metalloPcs. In addition the presence of a Ti@O stretch
at 960 cmꢁ1 confirmed the titanium phthalocyanine formation
[54]. Due to the paramagnetic nature of 7, the 1H NMR spectrum
of this compound could not be recorded. The molecular ion peaks
were observed at m/z = 1506.54 [M+2H2O]+ for Ni(II) (5), 1476.19
[M]+ for Zn(II) (6), 1521.16 [M+2Na]2+ for Cu(II) (7) and 1477.89
[M+H]+ for Ti(IV) (8) phthalocyanines. These peak values confirm
the proposed structures.
3.1. Outlook of the synthesized compounds
The preparation of 4-(1,3-benzothiazol-2-yl)phenoxy substi-
tuted phthalonitrile (3) and its target metal-free (4) and metall-
ophthalocyanine (5, 6, 7 and 8) derivatives is shown in Fig 1. The
structures of the novel compounds were characterized by a combi-
nation of 1H/13C NMR, IR, UV–Vis, elemental analysis and mass
spectral data.
3.2. Spectroscopic characterization via complementary techniques
Compound 3 was obtained from the reaction of 4-(1,3-ben-
zothiazol-2-yl)phenol (1) with 4-nitrophthalonitrile (2) in dry
K2CO3/dry DMF under N2 atmosphere at 55–60 °C in a Schlenk sys-
tem over 4 days. This was accomplished by a base catalyzed nucle-
ophilic aromatic nitro displacement of 4-nitrophthalonitrile with
compound 1 [38–42]. A comparison of the IR spectral data clearly
indicates the formation of compound 3 by the disappearance of the
O-H band of 1 at 3401 cmꢁ1, and by the appearance of a new vibra-
tion band at 2228 cmꢁ1 for (C„N) stretching and at 1287–1207
and 1087–1013 cmꢁ1 for @C–O–C vibration bands. In the 1H
NMR spectrum of compound 3, the disappearance of the resonance
at 10.25 ppm belonging to the –OH group also confirms the exis-
tence of the expected compound 3. The functionalized phthalonit-
rile 3 seems to be a very good resonance (Fig. 2). In the 1H NMR
0
0
spectrum of this compound, the Hd(d ) and He(e ), Hf, Hg, Hh, and
Hi protons possess AA’XX’ and AA’BB’ spin systems, respectively,
and the Ha, Hb and Hc protons associated with nitrile show an

84
A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
Fig. 1. The synthesis of metal-free and metallophthalocyanines.
3.3. Ground state electronic absorption spectra
In H-aggregates, the component monomers are arranged into a
face-to-face conformation, and transition dipoles are perpendicular
to the line connecting their centers. In contrast, in J-aggregates, the
component monomers adopt a side-by-side conformation, and
their transition dipoles are parallel to the line connecting their cen-
ters [60].
In general, phthalocyanines show typical electronic spectra
with two strong absorption regions, one of them is observed in
the UV region at ca. 300–500 nm and is called the B band, and
the another is observed in the visible region at ca. 600–750 nm
and is called the Q band [55]. The Q band absorptions of 4 in THF
were observed at k = 697 and 663 nm. A shoulder band was also
observed at k = 607 nm. The other absorption band (B) was ob-
Aggregation is dependent on the concentration, nature of the
solvent, nature and connection of the substituents, coordinated
metal ions and temperature [61,62]. In aggregated species, the
intensity of the Q-band starts to decrease, while the intensity of
the blue-shifted shoulder starts to increase for H-type aggregation.
Taking inspiration from this basic information, the aggregation
behavior of the zinc(II) phthalocyanine (6) and copper(II) phthalo-
cyanine (7) were investigated at different concentrations in THF
and in different solvents (Figs. 5 and 6). As the concentration was
increased, the intensity of the Q-band maxima increased and no
new bands, that would be a sign of aggregation, were observed
at the measured concentrations. The Zn(II) and Cu(II) phthalo-
cyanine derivatives showed monomeric behavior and the Beer-
Lambert law was obeyed between the concentrations 2 ꢀ 10ꢁ5
served at 320 nm, which is ascribed to deeper
p ?
p⁄ levels of
LUMO transitions [52,53,56] (Fig 3). As can be seen in the spec-
trum, the splitting of the Q band absorption of 4 to Qx and Qy bands
can be attributed to the fact that the D2h symmetry of the metal-
free phthalocyanine is non-degenerate [38–42].
The UV–Vis absorption spectra of the studied metallophthalocy-
anines (5, 6, 7 and 8) are given in Figs. 3 and 4. These compounds
showed the expected absorptions in THF at the main peaks of the Q
and B bands, appearing at k = 680 nm (corresponding to degener-
ate D4h symmetry), 324 nm (corresponding to the B region) for
Ni(II), 675, 613 and 316 nm for Zn(II), 680, 612 and 318 nm for
Cu(II), 698, 666, 636, 611 and 319 nm for Ti(IV) phthalocyanines,
respectively. These results are typical for metal complexes
of substituted and unsubstituted Pcs with D4h symmetry
[38–42,50–55]. The absorption spectra of 5-8 in THF indicated that
all compounds exist mainly as a monomeric species.
and 7 ꢀ 10ꢁ5 mol dmꢁ3, 1.2 ꢀ 10ꢁ5 and 3.2 ꢀ 10ꢁ5 mol dmꢁ3
,
respectively (Figs. 5a and 6a). However, Zn(II)Pc and Cu(II)Pc did
show aggregation at concentrations higher than 7 ꢀ 10ꢁ5 and
3.6 ꢀ 10ꢁ5 mol dmꢁ3, respectively. To investigate the effect of
the solvents on the aggregation behavior of the Zn(II)Pc and
Cu(II)Pc derivatives, the absorptions of the Zn(II)Pc and Cu(II)Pc
derivatives were measured in different solvents at 4 ꢀ 10ꢁ5 and
2.4 ꢀ 10ꢁ5 mol dmꢁ3, respectively. The Zn(II)Pc and Cu(II)Pc deriva-
tives did not show aggregation in the used solvents (Figs. 5b and 6b).
3.4. Aggregation studies
The high aggregation tendency of phthalocyanine compounds
due to interactions between their 18
p-electron systems often
cause weak solubility or insolubility in many solvents. It also af-
fects seriously their spectroscopic, photophysical, photochemical
and electrochemical properties. It has been established that
phthalocyanines can form H- and J-type aggregates, depending
on the orientation of the induced transition dipoles of their constit-
uent monomers [57–59].
3.5. Fluorescence spectra
Fig 7 shows the fluorescence emission, absorption and excita-
tion spectra of the studied phthalocyanine compounds 4, 6 and 8
in THF. The fluorescence emission peaks are listed in Table 1. The
observed Stokes shifts were within the region observed for

A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
85
Fig. 2. 1H NMR spectrum of compound 3 in CDCl3.
Fig. 4. The absorption spectra of compounds NiPc (5) and ZnPc (6) in THF at
1 ꢀ 10ꢁ5 mol dmꢁ3 concentration.
Fig. 3. The absorption spectra of compound sH2Pc (4), CuPc (7) and TiOPc (8) in THF
at 1 ꢀ 10ꢁ5 mol dmꢁ3 concentration.
for the studied tetra-substituted phthalocyanine compounds (4, 6
and 8) in THF suggesting that the nuclear configurations of
the ground and excited states are similar and not affected
phthalocyanine compounds. All the studied phthalocyanine com-
pounds (4, 6 and 8) showed similar fluorescence behavior in THF
(Fig. 7). The excitation spectra are similar to absorption spectra

86
A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
Fig. 5. (a) Absorption spectra of compound 6 in THF at different concentrations: A; 2 ꢀ 10ꢁ5, B; 3 ꢀ 10ꢁ5, C; 4.0 ꢀ 10ꢁ5, D; 5 ꢀ 10ꢁ5, E; 6 ꢀ 10ꢁ5, F; 7 ꢀ 10ꢁ5 mol dmꢁ3. (b)
Absorption spectra of compound 6 in different solvents. Concentration: 4 ꢀ 10ꢁ5 mol dmꢁ3
.
by excitation. The fluorescence emission of the substituted
Ti(IV)Pc compound (8) is less intense than the other studied
metal-free (4) and Zn(II) (6) phthalocyanine compounds in THF,
suggesting that there is more quenching of the substituted Ti(IV)Pc
compound (8).
except for the tetra-substituted Zn(II)Pc compound in THF. The rate
constants for fluorescence (kF) of studied tetra-substituted
phthalocyanine compounds (4, 6 and 8) are lower than for the
unsubstituted Zn(II)Pc compound, except for the tetra-substituted
Zn(II)Pc compound in THF. The kF value of compound 6 is the high-
est among the studied zinc Pc compounds.
3.6. Fluorescence quantum yields and lifetimes
3.7. Singlet oxygen quantum yields
The fluorescence quantum yields (UF) of the studied phthalocy-
anine compounds 4, 6 and 8 are given in Table 2. The UF values of
these compounds are slightly lower than that of the unsubstituted
zinc phthalocyanine, which was used as a standard for the fluores-
cence quantum yield determinations in THF. For a comparison
among the studied phthalocyanine compounds, the UF value of
the Zn(II)Pc compound (6) is the lowest among the studied phtha-
locyanine compounds.
The quantity of the singlet oxygen quantum yield (UD) is a sign
of the capability of the compounds as photosensitizers in photocat-
alytic applications, for instance PDT. The UD values of the studied
tetra-substituted phthalocyanine compounds (4, 6 and 8) were
determined in THF using a chemical method and DPBF used as a
scavenger. A reduction of the DPBF absorbance at 417 nm was
monitored using a UV–Vis spectrophotometer for all the studied
phthalocyanine compounds.
Fluorescence lifetime (sF) values of the studied tetra-substituted
phthalocyanine compounds (4, 6 and 8) are higher compared to
the unsubstituted zinc phthalocyanine compound in THF, except
for the substituted Zn(II)Pc compound (6). However, the sF values
are typical for phthalocyanine compounds [63–65].
Many factors can be responsible for the magnitude of the singlet
oxygen generation by a phthalocyanine, such as the triplet excited
state energy, ability of substituents and solvents to quench the sin-
glet oxygen, the triplet excited state lifetime and the efficiency of
the energy transfer between the triplet excited state of the phtha-
locyanine and the ground state of oxygen. It is believed that during
photosensitization, the photosensitizer molecule is first excited to
its singlet state and through intersystem crossing forms the triplet
The natural radiative lifetime (s0) and the rate constants for
fluorescence (kF) values are also given in Table 2. The s0 values of
the studied tetra-substituted phthalocyanine compounds (4, 6
and 8) are higher than for the unsubstituted Zn(II)Pc compound,

A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
87
Fig. 6. (a) Absorption spectra of compound
7
in THF at different concentrations: A; 1.2 ꢀ 10ꢁ5
,
B; 1.6 ꢀ 10ꢁ5
,
C; 2.0 ꢀ 10ꢁ5
,
D; 2.4 ꢀ 10ꢁ5
,
E; 2.8 ꢀ 10ꢁ5
, F;
3.2 ꢀ 10ꢁ5 mol dmꢁ3. (b) Absorption spectra of compound 7 in different solvents. Concentration: 2.4 ꢀ 10ꢁ5 mol dmꢁ3
.
state, and then transfers its energy to ground state oxygen,
the presence of a metal ion in the phthalocyanine cavity
could enhance intersystem crossing between excited singlet and
triplet states.
P
D
O2(3 g), generating excited singlet state oxygen, O2(1 g). This pro-
cess is known as the Type II mechanism. The formed singlet oxygen
is the main cytotoxic species and subsequently degradates the
substrate.
3.8. Photodegradation studies
There were not any changes in the Q band intensities of the
studied tetra-substituted phthalocyanine compounds during the
UD determinations (see Fig. 8 as an example for compound 4), con-
firming that the compounds were not degraded during the singlet
oxygen studies. The UD values of the studied tetra-substituted
phthalocyanine compounds (4, 6 and 8) are given in Table 2. While
the UD value of the metal-free phthalocyanine compound 4 is low-
er, the UD values of the Zn(II) (6) and Ti(IV) (8) phthalocyanine
compounds are higher than the unsubstituted Zn(II)Pc compound
in THF. The studied tetra-substituted Zn(II)Pc compound (6)
showed the highest UD value among the studied phthalocyanine
compounds (Table 2). Generally, Zn(II)Pc compounds possess high
triplet yields and they can generate singlet oxygen due to the d10
configuration of the central Zn2+ ion, which make them appropriate
photosensitizers for PDT applications. The metal-free phthalocya-
nine compound (4) showed the lowest UD value among the stud-
ied tetra-substituted Pc compounds (Table 2). It is suggest that
Degradation of the molecules under light irradiation gave the
idea to study their stability and this is especially important for
those molecules intended for use in photocatalytic applications.
The collapse of the absorption spectra without any distortion of
the shape confirms photodegradation not associated with photo-
transformation into different forms of MPc absorbing in the
visible region. The spectral changes observed for the studied
tetra-substituted phthalocyanine compounds 4, 6 and 8 during
light irradiation are as shown in Fig. 9 (using compound 9 as an
example in THF), and these confirm photodegradation occurred
without phototransformation.
Table 2 shows that the Ud values of the studied tetra-substituted
metal-free (4) and Zn(II) (6) and Ti(IV) (8) phthalocyanine com-
pounds are higher than the unsubstituted Zn(II)Pc compound
and that these studied compounds are less stable to degradation
under light irradiation compared to the unsubstituted Zn(II)Pc

88
A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
1000
800
600
400
200
0
0.3
0.25
0.2
0.15
0.1
0.05
0
(A)
Excitation
Emission
Absorption
500
550
600
650
700
750
800
Wavelength (nm)
800
0.5
0.4
0.3
0.2
0.1
0
(B)
Excitation
600
400
200
0
Emission
Absorption
500
550
600
650
700
750
800
Wavelength (nm)
1000
800
600
400
200
0
1
(C)
0.8
0.6
0.4
0.2
0
Excitation
Emission
Absorption
500
550
600
650
700
750
800
Wavelength (nm)
Fig. 7. Absorption, excitation and emission spectra of the compounds: (A) for complex 4, (B) for complex 6 and (C) for complex 8 in THF. Excitation wavelength = 640 nm for
4, 645 nm for 6 and 635 nm for 8.
Table 1
Absorption, excitation and emission spectral data for unsubstituted and tetrakis-4-(1,3-benzothiazol-2-yl)phenoxy substituted phthalocyanine compounds in THF.
Compound
Q band kmax (nm)
log
e
Excitation kEx (nm)
Emission kEm (nm)
Stokes shift DStokes (nm)
4
5
6
7
697, 663
680
675
680
698
4.88, 4.87
4.79
5.27
4.29
4.91
698, 665
–
675
–
699
666
703
–
681
–
703
673
5
–
6
–
4
7
8
ZnPca
666
5.19
a
Data from Ref. [64].
compound in THF. Especially, the Ud value of Ti(IV) phthalocyanine
compound 8 is very sensitive to light irradiation.
mimicker is the ability to undergo excited state charge transfer
with ease, and phthalocyanine-quinone systems have proved to
be the favored candidates for understanding the energy transfer
process [34,66].
3.9. Fluorescence quenching studies by 1,4-benzoquinone [BQ]
The fluorescence quenching behavior of the studied tetra-
substituted phthalocyanine compounds 4, 6 and 8 by BQ in THF
was found to obey Stern–Volmer kinetics, which is consistent with
Phthalocyanine compounds may also be used as photosynthetic
mimickers. An essential requirement for a good photosynthetic

A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
89
Table 2
Photophysical and photochemical data for unsubstituted and tetrakis-4-(1,3-benzothiazol-2-yl)phenoxy substituted phthalocyanine compounds in THF.
a
Compound
UF
sF (ns)
s0 (ns)
kF (sꢁ1) (ꢀ 107)
Ud (ꢀ 10ꢁ4
)
UD
4
6
8
ZnPc
0.24
0.20
0.23
0.25b
2.85
1.65
3.23
2.72b
11.87
8.25
8.42
12.1
0.19
3.49
0.08
0.73
0.63
0.53c
14.05
7.11
0.001
10.90b
9.17b
0.02b
a
b
c
kF is the rate constant for fluorescence. Values calculated using kF = UF/sF.
Ref. [64].
Ref. [35].
diffusion-controlled bimolecular reactions. Fig. 10 shows the
quenching of compound 4 by BQ in THF as an example. The slope
of the plots shown in Fig. 11 gave the KSV values and these are
listed in Table 3. The KSV values of the studied tetra-substituted
phthalocyanine compounds 4, 6 and 8 are lower than that of the
unsubstituted Zn(II)Pc compound in THF. The substituted metal-
free phthalocyanine compound 4 has the highest KSV value, the
substituted Ti(IV)Pc compound 8 has the lowest KSV in THF. The
bimolecular quenching constant (kq) values of the studied tetra-
substituted phthalocyanine compounds (4, 6 and 8) are also lower
1
1
0.8
0.6
y = -0.0018x + 0.9095
R
0.4
2 = 0.9948
0.8
0.2
0
0
50
100
150
Time ( Sec)
0.6
0 sec
30 sec
60 sec
0.4
90 sec
120 sec
150 sec
0.2
0
350
450
550
650
750
Wavelength (nm)
Fig. 8. The absorption spectral changes during the determination of singlet oxygen quantum yields. This determination was for compound 4 in DMF at a concentration of
1 ꢀ 10ꢁ5 M. (Inset: plot of DPBF absorbance vs. time.)
0.7
0.8
0.6
0.6
0.4
0.2
0
y = -0.0165x + 0.6592
R
2 = 0.9419
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
10
Time (Sec)
0 sec
5 sec
10 sec
350
450
550
650
750
Wavelength (nm)
Fig. 9. The absorption spectral changes of compound 8 in THF under light irradiation showing the disappearance of the Q-band at five seconds intervals. (Inset: plot of
absorbance vs. time.)

90
A. Aktaßs et al. / Polyhedron 48 (2012) 80–91
1000
800
600
400
200
0
[BQ]=0
[BQ]=saturated
650
670
690
710
730
750
770
790
Wavelength (nm)
Fig. 10. Fluorescence emission spectral changes of 4 (1.00 ꢀ 10ꢁ5 M) on addition of different concentrations of BQ in DMF. [BQ] = 0, 0.008, 0.016, 0.024, 0.032 and 0.040 M.
2.4
2.2
2
intensity of the emission spectrum of the substituted Ti(IV)Pc
compound (8) is less intense than the other studied phthalocya-
nine compounds. The studied tetra substitute Zn(II) (6) and Ti(IV)
(8) phthalocyanine complexes produced singlet oxygen in THF
and these complexes are good candidates for photocatalytic appli-
cations, such as PDT. The studied phthalocyanine compounds (4, 6
and 8) are less stable to degradation under light irradiation com-
pared to the unsubstituted Zn(II)Pc compound in THF. Especially,
the Ti(IV)Pc compound (8) is very sensitive to light irradiation.
The fluorescence quenching behavior of the studied tetra-
substituted phthalocyanine compounds (4, 6 and 8) were also
determined by BQ in THF and the results were found to obey
Stern–Volmer kinetics, which is consistent with diffusion-
controlled bimolecular reactions.
4
6
8
1.8
1.6
1.4
1.2
1
0
0.01
0.02
0.03
0.04
[BQ]
Fig. 11. Stern–Volmer plots for BQ quenching of substituted metal-free (4), zinc (II)
(6) and oxotitanium(IV) (8) phthalocyanines. [MPc] ꢃ1.00 ꢀ 10ꢁ5
M in DMF.
Acknowledgements
[BQ] = 0, 0.008, 0.016, 0.024, 0.032 and 0.040 M.
The authors thank The Research Fund of Karadeniz Technical
University, Project No.: 2010.111.002.8 (Trabzon/Turkey).
Table 3
Fluorescence quenching data for unsubstituted and tetrakis-4-(1,3-benzothiazol-2-
yl)phenoxy substituted phthalocyanine compounds in THF.
KSV (Mꢁ1
)
kq/1010 (dm3 molꢁ1 sꢁ1
)
References
Compound
4
6
8
32.69
28.62
26.87
48.48
1.14
1.73
0.83
1.78
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of kq values among the substituted compounds also follows the or-
der 6 > 4 > 8 in THF.
4. Conclusions
The novel peripherally tetra 4-(1,3-benzothiazol-2-yl)phenoxy
substituted metal free (4), Ni(II) (5), Zn(II) (6), Cu(II) (7) and Ti(IV)
(8) phthalocyanines were synthesized and characterized by ele-
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