Synthesis and characterization of a new soluble metal-free and metallophthalocyanines bearing biphenyl-4-yl methoxy groups

Article abstract of DOI:10.1016/j.jorganchem.2011.04.026

The synthesis and characterization of peripherally tetra-biphenyl-4-yl- methoxy substituted metal-free (4), Ni(II) (5), Cu(II) (6), Zn(II) (7), Co(II) (8) and Pb(II) (9) phthalocyanine derivatives are reported. These new phthalocyanine derivatives show th

Full text of DOI:10.1016/j.jorganchem.2011.04.026

Journal of Organometallic Chemistry 696 (2011) 2805e2814
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of a new soluble metal-free
and metallophthalocyanines bearing biphenyl-4-yl methoxy groups
b
,
a
Gülsev Dilber a, Mahmut Durmus¸ , Halit Kantekin a , Volkan Çakır
*
a Department of Chemistry, Karadeniz Technical University, 61080 Trabzon, Turkey
b Gebze Institute of Technology, Department of Chemistry, PO Box 141, Gebze 41400, Kocaeli, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and characterization of peripherally tetra-biphenyl-4-yl-methoxy substituted metal-free
(4), Ni(II) (5), Cu(II) (6), Zn(II) (7), Co(II) (8) and Pb(II) (9) phthalocyanine derivatives are reported.
These new phthalocyanine derivatives show the enhanced solubility in organic solvents and they have
been characterized by a combination of IR, 1H NMR, 13C NMR, UVevis, mass spectral data, elemental
analysis and thermal analysis methods (TG/DTA). The photophysical (fluorescence quantum yield and
lifetime) and photochemical (singlet oxygen generation and photodegradation quantum yield) properties
of tetra-biphenyl-4-yl-methoxy substituted zinc (II) phthalocyanine derivative (7) are also investigated.
The fluorescence of this phthalocyanine derivative (7) is effectively quenched by addition of 1,4-ben-
zoquinone (BQ).
Received 18 February 2011
Received in revised form
14 March 2011
Accepted 27 April 2011
Keywords:
Phthalocyanine
Macrocyclic compound
Nucleophilic displacement
Fluorescence
Ó 2011 Elsevier B.V. All rights reserved.
Singlet oxygen
Quantum yield
1. Introduction
purify and characterize them. However, the solubility of Pcs is very
important for investigating their chemical and physical character-
Phthalocyanines (Pcs) have many considerable physical and
chemical features. Therefore, they have attracted many investiga-
tors in the science world for decades [1]. Because of these proper-
ties, phthalocyanines have been utilized in many fields such as gas
sensors [2], semiconductor materials [3], photovoltaic cells [4,5],
liquid crystals [6,7], optical limiting devices [8e10], molecular
electronics [11], non-linear optical applications [12], Langmuire-
Blodgett films [13], fibrous assemblies [14] and photodynamic
therapy [15e18].
Phthalocyanines can be synthesized using microwave irradiation
as an alternative method, which has been used since 1980 [19,20].
Recently, microwave processing techniques have been received
a great deal of attention due to its various advantages such as
selectivity, rapid, direct, controllable and internal etc [21e23]. In the
last years, much effort has been dedicated to the microwave assisted
synthesis of metal-free and metallophthalocyanines [24,25].
The main disadvantage of phthalocyanines is their insolubility
in organic solvents. Lower solubilitiy of phthalocyanines hinders
the utilization in many fields including PDT and makes difficult to
istics [26]. In order to improve the solubility of phthalocyanines,
several substituents such as long alkyl, alkoxy, phenoxy groups and
crown ethers can be added from peripheral positions of the
phthalocyanines [27,28]. Soluble phthalocyanines with enhanced
optical, electronic, redox and magnetic properties are expected to
increase their possible application fields [29].
In this paper, we describe the synthesis and characterization of
a new type soluble metal-free phthalocyanine (4) and its Ni(II) (5),
Cu(II) (6), Zn(II) (7), Co(II) (8) and Pb(II) (9) complexes substituted
with biphenyl-4-yl methoxy groups by microwave irradiation.
Photophysical and photochemical properties of phthalocyanine
complexes are very useful for photocatalytic applications such as
photodynamic therapy (PDT) of cancer. We also investigated the
photophysical (fluorescence quantum yield and lifetime) and
photochemical (singlet oxygen generation and photodegradation
quantum yield) properties of zinc phthalocyanine derivative (7) in
DMSO, because zinc phthalocyanines have been extensively used as
photosensitizers for PDT application because of closed shell d10
configuration of zinc atom [30]. Zinc phthalocyanines have inten-
sive long wavelength absorption and high singlet and triplet yields,
which make them valuable photosensitizer for PDT applications.
The fluorescence-quenching behavior of this zinc phthalocyanine
(7) by 1,4-benzoquinone in DMSO is also reported.
* Corresponding author. Tel.: þ90 462 377 2589; fax: þ90 462 325 3196.
E-mail address: halit@ktu.edu.tr (H. Kantekin).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.04.026

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G. Dilber et al. / Journal of Organometallic Chemistry 696 (2011) 2805e2814
2. Experimental
2.4. Photochemical parameters
2.1. Materials
2.4.1. Singlet oxygen quantum yields
Singlet oxygen quantum yield (FD) determination was carried
out by using the experimental set-up described in literature
[38e40]. Typically, 3 ml portion of the respective zinc (II) phtha-
locyanine (7) solution (absorbance w 1 at the irradiation wave-
length) containing the singlet oxygen quencher was irradiated in
the Q band region with the photo-irradiation set-up described in
references [38e40]. FD was determined in air using the relative
method with ZnPc (in DMSO) as a reference. DPBF was used as
chemical quenchers for singlet oxygen in DMSO. Equation (3) was
Biphenyl-4-yl-methanol (1) and 4-nitrophthalonitrile (2) were
prepared by reported procedures [31,32]. All reactions were carried
under a dry nitrogen atmosphere using standard Schlenk tech-
niques. 1,3-diphenylisobenzofuran (DPBF) was purchased from
Fluka. All chemicals, solvents, and reagents were of reagent grade
quality and were used as purchased from commercial sources. All
solvents were dried and purified as described by Perrin and
Armarego [33].
employed for the calculations of FD
:
2.2. Equipments
Std
R$I
abs
FD
¼
FSDtd
(3)
RStd$Iabs
FTIR spectra were obtained on a Perkin Elmer 1600 FTIR spec-
trophotometer with the samples prepared as KBr pellets. 1H and 13
C
where FSDtd is the singlet oxygen quantum yield for the standard
ZnPc (FSDtd ¼ 0:67 in DMSO) [41] R and RStd are the DPBF photo-
bleaching rates in the presence of the respective sample (7) and
standard, respectively. Iabs and ISabtds are the rates of light absorption
by the sample (7) and standard, respectively. To avoid chain reac-
tions induced by DPBF in the presence of singlet oxygen [42], the
NMR spectra were recorded on a Varian Mercury 200 MHz spec-
trometer in CDCl3, and chemical shifts were reported ( ) relative to
d
TMS as an internal standard. Mass spectra were recorded on a
Micromass Quatro LC/ULTIMA LC-MS/MS spectrometer. Elemental
analyses of the complexes were performed on a LECO Elemental
Analyzer (CHNS O932) and Unicam 929 AA spectrophotometer.
UVevis spectra were recorded using a Unicam and Shimadzu 2001
UVevis spectrometers operating in the range 200e900 nm with
quartz cells. Melting points were measured on an electrothermal
apparatus. Domestic microwave oven was used for all synthesis of
phthalocyanines.
concentration of quencher was lowered to w3 ꢀ 10ꢁ5 mol dmꢁ3
.
Solutions of sensitizer containing DPBF was prepared in the dark
and irradiated in the Q band region using the above set-up. DPBF
degradation at 417 nm was monitored. The light intensity was
6.57 ꢀ 1015 photons sꢁ1 cmꢁ2 for FD determinations.
Photo-irradiations were done using a General Electric quartz
line lamp (300 W) for zinc (II) phthalocyanine derivative (7). A
600 nm glass cut off filter (Schott) and a water filter were used to
filter off ultraviolet and infrared radiations respectively. An inter-
ference 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.
2.4.2. Photodegredation quantum yields
Determination of photodegredation quantum yield (Fd) was
carried out previously described in the literature [38e40]. Fd was
determined using equation (4),
ðC0 ꢁ CtÞ$V$NA
Fd
¼
(4)
I
abs$S$t
where C0 and Ct are the sample (7) concentrations before and after
irradiation respectively, V, NA, S, t and Iabs are reaction volume, the
Avogadro’s constant, irradiated cell area, irradiation time and the
overlap integral of the radiation source light intensity, respectively.
A light intensity of 2.19 ꢀ 1016 photons sꢁ1 cmꢁ2 was employed for
Fd determinations.
2.3. Photophysical parameters
2.3.1. Fluorescence quantum yields and lifetimes
Fluorescence quantum yields (FF) were determined by the
comparative method (equation (1)) [34,35]
2.4.3. Fluorescence quenching by 1,4-benzoquinone (BQ)
F$AStd$n2
Fluorescence quenching experiments on the substituted ZnPc
derivative (7) was carried out by the addition of different
concentrations of BQ to a fixed concentration of the sample, and
the concentrations of BQ in the resulting mixtures were 0, 0.008,
0.016, 0.024, 0.032 and 0.040 M. The fluorescence spectra of
substituted ZnPc derivative (7) at each BQ concentration were
recorded, and the changes in fluorescence intensity related to BQ
concentration by the SterneVolmer (SeV) equation [43] was
shown in equation (5):
FF
¼
FFðStdÞ
(1)
FStd $A$n2Std
where F and FStd are the areas under the fluorescence emission
curves of the zinc phthalocyanine (7) and the standard, respec-
tively. A and AStd are the relative absorbance of the sample and
standard at the excitation wavelength, respectively. n and nstd
are the refractive indices of solvents for the sample and stan-
dard, respectively. Unsubstituted ZnPc (in DMSO) (FF ¼ 0.20)
[36] was employed as the standard. Both the sample and stan-
dard were excited at the same wavelength. The absorbance of
the solutions was ranged between 0.04 and 0.05 at the excitation
wavelength.
I0
I
¼ 1 þ KSV½BQꢂ
(5)
where I0 and I are the fluorescence intensities of fluorophore in the
absence and presence of quencher, respectively. [BQ] is the
concentration of the quencher and KSV is the SterneVolmer
constant which is the product of the bimolecular quenching
Natural radiative (s0) lifetimes were determined using Photo-
chem CAD program which uses the StricklereBerg equation [37].
The fluorescence lifetimes (
s
F) were evaluated using equation (2).
(2)
constant (kq) and the
sF and is expressed in equation (6).
sF
s0
FF
¼
KSV ¼ kq$sF
(6)

G. Dilber et al. / Journal of Organometallic Chemistry 696 (2011) 2805e2814
2807
The ratios of Io/I were calculated and plotted against [BQ]
according to equation (5), and KSV is determined from the slope.
decomposition products. The obtained green product was filtered
off, washed with hot ethanol and then dried in vacuo (P2O5). Puri-
fication of the solid products were accomplished by preparative
thin layer chromatography (TLC) (chloroform/methanol (10:1) and
chloroform/methanol (20:1) solvent system as eluents, respec-
tively). The phthalocyanine derivatives are soluble in CHCl3, CH2Cl2,
DMSO, DMF, THF and pyridine.
2.5. Synthesis
2.5.1. 4-(Biphenyl-4-ylmethoxy)phthalonitrile (3)
4-Nitrophthalonitrile (2) (1.41 g, 8.15 mmol) was dissolved in
dry DMF (20 ml) under N2 atmosphere, and biphenyl-4-yl-
methanol (1) (1.5 g, 8.15 mmol) was added to solution. After stir-
ring for 15 min, finely ground anhydrous K2CO3 (3.37 g,
24.42 mmol) was added portion wise within 2 h. The reaction
mixture was stirred under N2 at 50 ꢃC for 5 days. During this
process, the reaction was monitored by TLC using chloroform as
eluent. At the end of this period, the reaction mixture was poured
into ice-water and stirred at room temperature for 24 h to yield
a crude product. Then, this precipitate was isolated by filtration and
washed with distilled water and cold ethanol. The crude product
was crystallized from ethanol to give pure product and then dried
in vacuo (P2O5). Yield: 1.68 g (67%), mp: 158e160 ꢃC. Anal. Calc. for
C21H14N2O: C, 81.27; H, 4.55; N, 9.03%. Found: C, 81.34; H, 4.61; N,
9.06. IR (KBr tablet) vmax/cmꢁ1: 3081 (AreH), 2927e2873 (Aliph.
CeH), 2230 (C^N), 1597 (C]C), 1595, 1493, 1457, 1322, 1255
2.5.3.1. 2(3),9(10),16(17),23(24)-Tetrakis(biphenyl-4-yl-methoxy)pht-
halocyaninato nickel (II)(5). Yield: 0.089 g (45%), mp: 334.9e361.9
(decomposition). Anal. Calc. for C84H56N8O4Ni: C, 77.60; H, 4.34; N,
8.62%. Found: C, 77.58; H, 4.35; N, 8.66.IR (KBr tablet) vmax/cmꢁ1
:
3049 (AreH), 2917e2862 (Aliph. CeH), 1510, 1485, 1408, 1277, 1238
(AreCH2eO), 1093, 1063, 1007, 824, 758, 696. 1H NMR (CDCl3) (
d:
ppm): 7.71e7.69 (m, 8H, AreH), 7.61e7.19 (m, 36H, AreH), 6.99 (s,
4H, AreH), 4.24 (s, 8H, AreCH2eO). 13C NMR (CDCl3) (
d: ppm): 162.6,
CN
CN
CH2OH
NO2
(1)
(2)
(AreCH2eO), 1084, 997, 786, 754, 704. 1H NMR (CDCl3) (
d: ppm):
dry DMF
anhydrous K2CO3
7.70 (d, J ¼ 8 Hz, 1H, AreH), 7.65 (d, J ¼ 8 Hz, 1H, AreH), 7.58e7.29
50 o
C
(m, 9H, AreH), 7.26 (s, 1H, AreH), 5.20 (s, 2H, AreCH2eO). 13C NMR
(CDCl3) (d: ppm): 161.6, 141.9, 140.3, 135.2, 133.3, 128.9, 128.0, 127.7,
127.1, 119.9, 119.7, 117.5, 115.6, 115.2, 107.6, 70.8. MS (ESþ), (m/z):349
[M þ K]þ.
CN
CN
O
2.5.2. 2(3),9(10),16(17),23(24)-Tetrakis(biphenyl-4-yl-methoxy)
phthalocyanine (4)
(3)
A mixture of 4-(biphenyl-4-yl-methoxy)phthalonitrile (3) (0.2 g,
0.64 mmol) and catalytic amount of 1,8-diazabicyclo[5.4.0]undec-
7-ene (DBU) in 2.5 ml of dry n-pentanol was heated and stirred at
160 ꢃC in a sealed glass tube for 24 h under N2. After cooling to room
temperature, the reaction mixture was precipitated by the addition
of 20 ml of ethanol and green precipitate was filtered off. This
product was refluxed with ethanol (40 ml) for 4 h to dissolve the
unreacted starting materials and decomposition products. The
obtained dark green product was filtered off, washed with hot
ethanol and then dried in vacuo (P2O5). This crude product was
purified by preparative thin layer chromatography (TLC) using
chloroform as eluent. The dark green solid product is soluble in
CHCl3, CH2Cl2, DMSO, DMF, THF and pyridine. Yield: 0.075 g (38%),
mp: 373.0e420.9 (decomposition). Anal. Calc. for C84H58N8O4: C,
81.14; H, 4.70; N, 9.01%. Found: C, 81.14; H, 4.67; N, 9.07. IR (KBr
tablet) vmax/cmꢁ1: 3250 (NeH), 3054 (AreH), 2923e2852 (Aliph.
CeH), 1602 (NeH bending), 1517, 1485, 1404, 1226 (AreCH2eO),
II
I
O
O
N
N
N
N
N
N
M
N
N
1113, 1006, 822, 758, 696. 1H NMR (CDCl3) (
8H, AreH), 7.69e7.11 (m, 36H, AreH), 6.77 (s, 4H, AreH), 4.23 (s, 8H,
AreCH2eO). 13C NMR (CDCl3) (
: ppm): 168.1, 139.5, 134.9, 132.6,
131.2, 129.1, 128.5, 127.4, 125.7, 119.5, 116.2, 114.7, 114.3, 102.6, 102.3,
d: ppm): 7.73e7.70 (m,
O
(4)
O
d
68.4. UVevis (CHCl3): lmax/nm (log 3): 335 (5.28), 389 (4.94), 643
(5.02), 671 (5.10), 707 (5.07). MS (ESþ), (m/z): 1266 [M þ Na]þ.
2.5.3. The general procedure for synthesis of metallophthalocyanines
(5) and (6)
A mixture of 4-(biphenyl-4-yl-methoxy)phthalonitrile (3) (0.2 g,
0.64 mmol), anhydrous metal salt (0.16 mmol; 0.02 g NiCl2 or
0.022 g CuCl2) catalytic amount of DBU in 2.5 ml of dry n-pentanol
was heated and stirred at 160 ꢃC in a sealed glass tube for 24 h
under N2. After cooling to room temperature, the reaction mixture
was precipitated by the addition of 20 ml of ethanol and green
precipitate was filtered off. This product was refluxed with ethanol
(40 ml) for 4 h to dissolve the unreacted starting materials and
Compound
M
4
5
6
7
8
9
2H Ni+2 Cu+2 Zn+2 Co+2 Pb+2
Scheme 1. The synthesis of the metal-free and metallophthalocyanines. (I) n-pentanol,
DBU and metal salts or (II) MW, 175 ꢃC, 350 W and metal salts.

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G. Dilber et al. / Journal of Organometallic Chemistry 696 (2011) 2805e2814
138.2, 135.5, 133.0, 132.7, 131.2, 128.3, 127.3, 125.1, 124.7, 119.2, 114.5,
(
d
: ppm): 7.70e7.62 (m, 8H, AreH), 7.57e7.35 (m, 36H, AreH), 7.25
(s, 4H, AreH), 4.21 (s, 8H, AreCH2eO). 13C NMR (CDCl3) (
: ppm):
167.4, 137.9, 135.6, 133.9, 132.2, 129.1, 128.3, 127.7, 127.4, 126.2, 121.7,
111.3, 106.1, 105.0, 68.4. UVevis (CHCl3): lmax/nm (log
3): 365 (4.96),
d
392 (4.93), 623 (4.86), 692 (5.27). MS (ESþ), (m/z): 1340[M þ 1 þ K]þ.
118.2, 113.3, 110.8, 108.1, 67.9. UVevis (CHCl3): lmax/nm (log 3): 281
2.5.3.2. 2(3),9(10),16(17),23(24)-Tetrakis(biphenyl-4-yl-methoxy)pht-
halocyaninato copper (II) (6). Yield: 0.074 g (37%), mp: 323.9e356.5
(decomposition). Anal. Calc. for C84H56N8O4Cu: C, 77.31; H, 4.33; N,
(5.15), 350 (5.02), 620 (4.65), 686 (5.21). MS (ESþ), (m/z): 1308
[M þ 1]þ.
8.59%. Found: C, 77.37; H, 4.34; N, 8.52. IR (KBr tablet) vmax/cmꢁ1
:
2.5.4.2. 2(3),9(10),16(17),23(24)-Tetrakis(biphenyl-4-yl-methoxy)phth-
alocyaninato cobalt (II) (8). Yield: 0.1 g (51%), mp: 354.4e423.1-
(decomposition). Anal. Calc. for C84H56N8O4Co: C, 77.59; H, 4.34; N,
3049 (AreH), 2925e2851 (Aliph. CeH), 1521, 1486, 1401, 1275, 1231
(AreCH2eO), 1116, 1095, 1055, 1007, 824, 759, 697. UVevis (CHCl3):
lmax/nm (log
3
): 339 (5.13), 393 (4.76), 639 (4.79), 681 (5.06). MS
8.62%. Found: C, 77.58; H, 4.49; N, 8.57. IR (KBr tablet) vmax/cmꢁ1
:
(ESþ), (m/z): 1305[M]þ.
3049 (AreH), 2923e2857 (Aliph. CeH), 1519, 1486, 1457, 1374, 1275,
1224 (AreCH2eO), 1119, 1095, 1004, 824, 758, 696. UVevis (CHCl3):
2.5.4. The general procedure for synthesis of metallophthalocy-
anines (7), (8) and (9)
lmax/nm (log 3
): 260 (5.15), 338 (5.07), 617 (4.69), 671 (5.15). MS (ESþ),
(m/z): 1300 [M]þ.
A
mixture of 4-(biphenyl-4-yl-methoxy)phthalonitrile (3)
(0.2 g, 0.64 mmol), anhydrous metal salt (0.16 mmol; 0.029 g
Zn(CH3COO)2, 0.02 g CoCl2 or 0.036 g PbO) and 2-(dimethylamino)
ethanol (2.5 ml) was irradiated in a microwave oven at 175 ꢃC,
350 W for 8 min. After cooling to room temperature, the reaction
mixture was precipitated by the addition of 20 ml of ethanol and
green precipitate was filtered off. This product was refluxed with
ethanol (40 ml) for 4 h to dissolve the unreacted starting materials
and decomposition products. The obtained green product was
filtered off, washed with hot ethanol and then dried in vacuo (P2O5).
Purification of the solid products were accomplished by preparative
thin layer chromatography (TLC) (chloroform/methanol (10:1),
chloroform and chloroform/methanol (20:1) solvent system as
eluents, respectively). The phthalocyanine derivatives are soluble in
CHCl3, CH2Cl2, DMSO, DMF, THF and pyridine.
2.5.4.3. 2(3),9(10),16(17),23(24)-Tetrakis(biphenyl-4-yl-methoxy)ph-
thalocyaninato lead (II) (9). Yield: 0.074 g (32%), mp: 320.0e354.9
(decomposition). Anal. Calc. for C84H56N8O4Pb : C, 69.65; H, 3.90; N,
7.74. Found: C, 69.76; H, 4.02; N, 7.74. IR (KBr tablet) vmax/cmꢁ1
:
3071 (AreH), 2917e2851 (Aliph. CeH), 1517, 1485, 1457, 1374, 1322,
1273, 1222 (AreCH2eO), 1113, 1079, 1005, 824, 756, 745, 696. 1H
NMR (CDCl3) (
36H, AreH), 7.15 (s, 4H, AreH), 4.23 (s, 8H, AreCH2eO). 13C NMR
(CDCl3) ( : ppm): 168.1, 136.2, 135.5, 132.7, 131.4, 131.2, 129.0, 128.3,
127.9, 127.8, 127.4, 125.1, 120.2, 119.9, 114.7, 68.4. UVevis (CHCl3):
d: ppm): 7.70e7.67 (m, 8H, AreH), 7.62e7.26 (m,
d
lmax/nm (log 3): 361 (4.90), 389 (4.85), 671 (4.64), 727 (5.17). MS
(ESþ), (m/z): 1450 [M þ 1]þ.
3. Results and discussion
2.5.4.1. 2(3),9(10),16(17),23(24)-Tetrakis(biphenyl-4-yl-methoxy)ph-
thalocyaninato zinc (II) (7). Yield: 0.096 g (46%), mp: 375.4e432.0
(decomposition). Anal. Calc. for C84H56N8O4Zn: C, 77.20; H, 4.32; N,
3.1. Synthesis and characterization
The general synthetic route for the synthesis of new metal-free
and metallophthalocyanines is given in Scheme 1. The first step in
the synthetic procedure was to obtain 4-(biphenyl-4-ylmethoxy)
phthalonitrile (3), starting from biphenyl-4-yl-methanol (1) and
8.57%. Found: C, 77.17; H, 4.31; N, 8.55. IR (KBr tablet) vmax/cmꢁ1
:
3049 (AreH), 2923e2846 (Aliph. CeH), 1487, 1451, 1376, 1279, 1225
(AreCH2eO), 1092, 1051, 1004, 824, 745, 696. 1H NMR (CDCl3)
Fig. 1. 1H NMR spectrum of compound 3.

G. Dilber et al. / Journal of Organometallic Chemistry 696 (2011) 2805e2814
2809
Fig. 2. 13C NMR spectrum of compound 3.
4-nitrophthalonitrile (2). This reaction involves the nucleophilic
aromatic nitro displacement of 4-nitrophthalonitrile (2) with
biphenyl-4-yl-methanol (1) in the presence of anhydrous K2CO3 as
the base in dry dimethylformamide (DMF) at 50 ꢃC [44]. The
Cyclotetramerization of the phthalonitrile derivative (3) to the
metal-free phthalocyanine (4) was accomplished in n-pentanol in
the presence of a few drops of DBU as a strong base at 160 ꢃC
in sealed tube. The cyclotetramerization was realized in a moderate
yield of 38%. The nickel (II) and copper (II) phthalocyanines
condensation was realized in
a moderate yield of 67%.
Fig. 3. COSY spectrum of compound 3.

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G. Dilber et al. / Journal of Organometallic Chemistry 696 (2011) 2805e2814
1.5
1
0.5
0
200
300
400
500
600
700
800
900
Fig. 4. UVevis spectra of compounds 4 (d), 5 (....) and 6 (-.-.) in chloroform.
(5 and 6) were obtained from dinitrile compound (3) in the pres-
ence of anhydrous metal salts NiCl2 or CuCl2 and DBU in n-pentanol
at 160 ꢃC. The zinc (II), cobalt (II) and lead (II) phthalocyanines
(7e9) were synthesized from dinitrile derivative (3) and corre-
sponding anhydrous metal salts Zn(CH3COO)2, CoCl2 and PbO,
respectively, by microwave irradiation in 2-(dimethylamino)
ethanol at 175 ꢃC and 350 W for 8 min. The structures of novel
compounds were characterized by IR, 1H NMR, 13C NMR, UVevis,
mass spectral data, elemental analysis and thermal methods
TG/DTA.
In the IR spectrum of 3, the disappearance of OH and NO2 groups
stretching vibrations belong to compounds 1 and 2 along with the
appearance of new bands at 2230 and 1255 cmꢁ1 arising from C^N
and AreCH2eO groups, respectively, are in agreement with the
proposed structure. In the 1H NMR spectrum of 3, OH group of
compound 1 disappeared as expected. The 1H NMR spectrum of 3
Fig. 6. DTA thermograms of compounds 6, 4 and 8.
strong aggregation of the molecules [45]. The mass spectrum of 4
shows a peak at m/z ¼ 1266 [M þ Na]þ, which confirms the
structure. The results of the elemental analysis confirmed the
proposed structure of compound 4.
After conversion of the phthalonitrile compound (3) to metal-
lophthalocyanines 5e9, the sharp C^N vibration around
2230 cmꢁ1 disappeared in the IR spectra of metallophthalocyanines
(5e9). The rest of the IR spectra of metallophthalocyanines are very
similar to those of the metal-free phthalocyanine 4. In the 1H NMR
spectra of these compounds (5e9) are almost identical to those of
metal-free phthalocyanine 4. 1H NMR measurement of the cop-
per(II) and cobalt(II) phthalocyanine (6 and 8) were precluded
owing to their paramagnetic nature of these compounds. In the
mass spectra of compounds 5, 6, 7, 8 and 9, the presence of
molecular ion peaks at m/z ¼ 1340[M þ 1 þ K]þ, 1305[M]þ, 1308
[M þ 1]þ, 1300 [M]þ, and 1450 [M þ 1]þ, respectively, confirmed
the proposed structures. In addition to these data, the elemental
analysis of these compounds was also determined. The new
phthalocyanines 4e9 were reasonably soluble in CHCl3, CH2Cl2,
DMSO, DMF, THF and pyridine.
(Fig.1) showed new signals at
d
¼ 7.70 (d, 8 Hz, 1H, AreH), 7.65 (d,
8 Hz, 1H, AreH), 7.58e7.29 (m, 9H, AreH), 7.26 (s, 1H, AreH),
belonging to aromatic protons and 5.20 (s, 2H, AreCH2eO)
belonging to aliphatic protons. The 13C NMR spectrum of 3 (Fig.2)
indicated the presence of nitrile carbon atoms in 3 at
d
¼ 115.6 and
115.2 ppm. The COSY spectral data was also in good agreement with
the formation of 3, shown in Fig.3. The mass spectrum of compound
3, which shows a peak at m/z ¼ 349 [M þ K]þ, supports the
proposed formula for this compound.
In the IR spectrum of 4, characteristic peaks for phthalocyanines
were observed. The peak at 3250 cmꢁ1 is the characteristic metal-
free phthalocyanine NeH stretching bands. However, 3054 (AreH),
2923e2852 (Aliph. CeH), 1602 (NeH bending) bands were pre-
sented in the spectrum. The disappearance of the C^N stretching
vibration on the IR spectra of 3 suggested the formation of
compound 4. In the 1H NMR spectrum of 4, the typical shielding of
inner core protons could not be observed due to the probable
1.5
1
0.5
0
200
300
400
500
600
( nm )
Fig. 5. UVevis spectra of compounds 7 (-.-.), 8 (d) and 9 (....) in chloroform.
700
800
900
Fig. 7. DTA thermograms of compounds 9, 5 and 7.

G. Dilber et al. / Journal of Organometallic Chemistry 696 (2011) 2805e2814
2811
Table 1
Thermal properties of the biphenyl-4-yl-methoxy substituted phthalocyanines.
3.3. Thermal properties
The thermal behaviors of the metallophthalocyanines were
investigated by TG/DTA. The thermal stabilities of the metal-free (4)
and metallophthalocyanines (5e9) were evaluated by the ꢁt1her-
Compound
M
Initial decomposition
temperature in ꢃC
Main decomposition
temperature in ꢃC
4
5
6
7
8
9
2H
Ni
Cu
Zn
Co
Pb
373.0
334.9
323.9
375.4
354.4
320.0
420.9
361.9
356.5
432.0
423.1
354.9
mogravimetric analysis at a heating rate of 20 ꢃC min
in
a nitrogen flow (Figs. 6 and 7). DTA curves exhibited exothermic
changes for studied compounds 4e9 in the investigated region.
There were no melting points for any of the studied phthalocya-
nines; it means that they were decomposed. Though the potential
thermal stabilities of phthalocyanines are well known, the obtained
novel phthalocyanines (4e9) were observed not to be stable above
320 ꢃC. The initial and main decomposition temperatures were
given in Table 1. The initial decomposition temperatures decreased
in the order of 7 > 4 > 8 > 5 > 6 > 9.
3.2. Ground state electronic absorption properties
Electronic spectra are especially useful to identify the structure
of the phthalocyanines. Generally, UVevis spectra of phthalocya-
nines show typical electronic spectra with two strong absorption
bands known as Q and B bands. The Q band in the visible region at
3.4. Photophysical properties of zinc (II) phthalocyanine (7)
ca. 600e750 nm is attributed to the
pe
p* transition from HOMO
3.4.1. Fluorescence quantum yield and lifetime
(highest occupied molecular orbital) to the LUMO (lowest unoc-
cupied molecular orbital) of the Pc (ꢁ2) ring and the B band in the
UV region at ca. 300e400 nm arises from the deeper nep* transi-
tions [46].
The electronic spectra are given for phthalocyanine compounds
4e6 in Fig. 4, and 7e9 in Fig. 5. In the UVevis spectrum of metal-
free phthalocyanine (4), the characteristic split Q band was
observed at 671 and 707 nm in chloroform which can be attributed
The fluorescence behavior of the zinc phthalocyanine complex
(7) was studied in DMSO. Fig. 8 shows the absorption, fluorescence
emission and excitation spectra of this complex in DMSO. Fluo-
rescence emission intensity was observed at 695 nm for 7. The
shape of the excitation spectrum (lEx ¼ 684 nm) of 7 was similar to
its absorption spectrum (lAbs ¼ 682 nm). The observed Stokes shift
was 13 nm and typical of MPc complexes in DMSO. This proximity
of the wavelength of the Q band absorption to the Q band maxima
of the excitation spectrum for zinc phthalocyanine complex (7)
suggest that the nuclear configurations of the ground and excited
states are similar and not affected by excitation.
The fluorescence quantum yield (FF) of zinc phthalocyanine
complex (7) (FF ¼ 0.19) was typical of MPc complexes in DMSO
[30]. The FF value of the substituted zinc phthalocyanine complex
(7) is slightly lower than for unsubstituted ZnPc (FF ¼ 0.20) [36] in
DMSO.
a1u
eg transition [47]. A typical spectrum of the metal-free
phthalocyanine (4) showed B bands at 335 and 389 nm in chloro-
form. The UVevis absorption spectra of metallophthalocyanines
5e9 in chloroform were observed the intense Q absorption at 692,
681, 686, 671 and 727 nm with weaker absorptions at 623, 639, 620,
617 and 671 nm, respectively. In addition, the intense B band
absorptions were observed at 365 and nm for 5, 339 and 393 for 6,
281 and 350 for 7, 260 and 338 nm for 8 and 361 and 389 nm for 9.
The Q band of the lead phthalocyanine complex (9) was red-shifted
when compared to the corresponding other studied phthalocya-
nine complexes (4e8), suggesting that the non-planar effect of the
bigger lead as central atom.
Lifetime of fluorescence (sF) was calculated using the Strick-
lereBerg equation. Using this equation, a good correlation has been
[35] found for the experimentally and theoretically determined
fluorescence lifetimes for the unaggregated molecules as is the case
700
600
500
400
300
200
100
0
0.35
0.3
0.25
Excitation
Emission
Absorption
0.2
0.15
0.1
0.05
0
500
550
600
650
700
750
800
Wavelength (nm)
Fig. 8. Absorption, fluorescence emission and excitation spectra of zinc phthalocyanine complex (7) in DMSO. Excitation wavelength ¼ 650 nm.

2812
G. Dilber et al. / Journal of Organometallic Chemistry 696 (2011) 2805e2814
1
0.8
0.6
0.4
0.2
0
0 sec
5 sec
10 sec
15 sec
20 sec
25 sec
30 sec
y = -0.0149x + 0.844
= 0.9925
R
Time (sec)
300
400
500
600
700
800
Wavelength (nm)
Fig. 9. A typical spectrum for the determination of singlet oxygen quantum yield. This determination was for zinc phthalocyanine complex (7) in DMSO at a concentration of
1.0 ꢀ 10ꢁ5 M (Inset: Plots of DPBF absorbance versus time).
in this work for 7 in DMSO.
was longer when compared to unsubstituted ZnPc (sF ¼ 1.22 ns) [48]
in DMSO. The natural radiative lifetime ( 0) value of the complex 7
s0 ¼ 14.91 ns) was also longer when compared to unsubstituted
s
F value of the complex 7 (sF ¼ 2.79 ns)
of DPBF spectra was monitored using UVevis spectrophotometer
(Fig. 9). Many factors are responsible for the magnitude of the
determined quantumyieldofsingletoxygenincluding;tripletexcited
state energy, ability of substituents and solvents to quench the singlet
oxygen, the triplet excited state lifetime and the efficiency of the
energy transfer between the triplet excited state and the ground state
of oxygen.
There was no change in the Q band intensity of zinc phthalo-
cyanine complex (7) during the FD determination, confirming that
complex was not degraded during singlet oxygen study. The FD
value of the complex 7 is 0.42 and it is lower than unsubstituted
ZnPc value (FD ¼ 0.67) [41] in DMSO, but still enough for photo-
catalytic applications such as PDT.
s
(
ZnPc (s0 ¼ 6.80 ns) in DMSO [48]. The rate constants for fluorescence
(kF) value of the complex 7 (kF ¼ 6.70 ꢀ 107
s
ꢁ1) was lower than
unsubstituted ZnPc (kF ¼ 14.7 ꢀ 107 sꢁ1) in DMSO [48].
3.5. Photochemical properties of zinc (II) phthalocyanine (7)
3.5.1. Singlet oxygen quantum yield
Singletoxygenquantumyield(FD)wasdeterminedinDMSOusing
a chemical method using DPBF as a quencher. The disappearance
350
[BQ]=0
2.5
2
300
250
y = 22.496x + 1
R
= 0.9957
1.5
1
[BQ]=saturated
200
0.5
0
0
0.01
0.02
0.03
0.04
150
100
50
[BQ]
0
660
680
700
720
740
760
780
800
Wavelength (nm)
Fig. 10. Fluorescence emission spectral changes of 7 (1.00 ꢀ 10ꢁ5 M) on addition of different concentrations of BQ in DMSO. [BQ] ¼ 0, 0.008, 0.016, 0.024, 0.032, 0.040 M and
saturated with BQ. Inset: SterneVolmer plot for BQ quenching of 7 in DMSO.

G. Dilber et al. / Journal of Organometallic Chemistry 696 (2011) 2805e2814
2813
3.5.2. Photodegradation study
this work, we also present a study of the light harvesting and
energy transducing tendencies of mixtures of zinc phthalocyanine
complex (7) and BQ. The effective quenching of the complex’
fluorescence by BQ suggests that systems that are composite of
complex 7 and quinones could well serve as good light harvesters
and energy transducers.
Degradation of the molecules under light irradiation can be used
to study their stability and this is especially important for those
molecules intended for use as photocatalysts. The collapse of
the absorption spectra without any distortion of the shape
confirms clean photodegradation not associated with photot-
ransformation. The spectral changes observed for zinc phthalocy-
anine complex (7) during confirmed photodegradation occurred
without phototransformation.
Acknowledgement
Fd values indicate that the stability of the molecules toward the
light irradiation. Stable phthalocyanine complexes show Fd values
as low as 10ꢁ6 and for unstable molecules, values of the order of
10ꢁ3 have been reported [30]. The photodegradation value of the
complex 5 is 0.18 ꢀ 10ꢁ4 and it is less stable to degradation
compared to unsubstituted ZnPc (Fd ¼ 2.61 ꢀ 10ꢁ4) [48] in DMSO.
Thus the substitution of zinc phthalocyanine with biphenyl-4-yl-
methoxy group seems to decrease the stability of this complex in
DMSO.
This study was supported by the Research Fund of Karadeniz
Technical University, Project no: 2006.111.002.1 (Trabzon-Turkey).
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In the presented work, the synthesis of novel metal-free (4),
Ni(II) (5), Cu(II) (6), Zn(II) (7), Co(II) (8) and Pb(II) (9) phthalocya-
nine derivatives bearing peripheral biphenyl-4-ylmethanol
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