Novel triazole bearing zinc(II) and magnesium(II) metallo-phthalocyanines: Synthesis, characterization, photophysical and photochemical properties

Article abstract of DOI:10.1016/j.jorganchem.2013.08.029

The synthesis and characterization of novel tetrakis N-(3,5-dichlorophenyl) -5-methyl-3H-1,2,4-triazol-3-one (1) and N-(3,5-dichlorophenyl)-5-ethyl-3H-1,2, 4-triazol-3-one (2) substituted phthalonitrile derivatives and their new organosoluble peripherally

Full text of DOI:10.1016/j.jorganchem.2013.08.029

Journal of Organometallic Chemistry 745-746 (2013) 379e386
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Novel triazole bearing zinc(II) and magnesium(II) metallo-
phthalocyanines: Synthesis, characterization, photophysical and
photochemical properties
c
d
Hakkı Türker Akçaya, Mehmet Pis¸ kin b, Ümit Demirbas¸ , Rıza Bayrak c, Mahmut Durmus¸ ,
,
Emre Mentes¸ e a, Halit Kantekin c
*
a
ꢀ
Department of Chemistry, Faculty of Sciences, Recep Tayyip Erdogan University, 53100 Rize, Turkey
b Marmara University, Faculty of Art and Science, Department of Chemistry, 34722 Kadikoy-Istanbul, Turkey
c Department of Chemistry, Faculty of Sciences, Karadeniz Technical University, 61080 Trabzon, Turkey
d 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 synthesis and characterization of novel tetrakis N-(3,5-dichlorophenyl)-5-methyl-3H-1,2,4-triazol-3-
one (1) and N-(3,5-dichlorophenyl)-5-ethyl-3H-1,2,4-triazol-3-one (2) substituted phthalonitrile de-
rivatives and their new organosoluble peripherally tetra-substituted zinc(II) (6 and 7) and magnesium(II)
(8 and 9) phthalocyanines were studied in this study. Photophysical and photochemical data of these
compounds were measured in dimethysulfoxide (DMSO). The magnesium(II) phthalocyanine derivatives
showed excellent fluorescent properties and the corresponding zinc(II) phthalocyanines generated
efficient singlet oxygen. The fluorescence quenching behavior of the studied tetra-peripherally
substituted zinc(II) and magnesium(II) phthalocyanine compounds by the addition of 1,4-
benzoquinone were also studied in DMSO. These molecules can distinctly be employed in the field of
photodynamic therapy in combination with fluorescence imaging.
Received 3 July 2013
Received in revised form
13 August 2013
Accepted 14 August 2013
Keywords:
Phthalocyanine
Zinc
Magnesium
Triazole
Ó 2013 Elsevier B.V. All rights reserved.
Singlet oxygen
Fluorescence
1. Introduction
photophysical and photochemical behavior of novel triazole
substituted Pc derivatives were investigated. The synthesis of tri-
Although phthalocyanines (Pcs) are relatively old dye com-
pounds, their potential applications are still extensively studied by
many scientists because of their interesting optical, electrical
azole substituted Pcs is the same as with other substituted Pcs in
literature [14e19].
In our study two different triazole containing phthalonitrile de-
rivatives (4 and 5) were used for synthesis of the peripherally tetra-
substituted Zn(II) (6 and 7) and Mg(II) (8 and 9) Pc macrocycles. The
newly synthesized phthalonitrile derivatives and their Pcs counter-
parts were characterized spectroscopically. The photophysical
properties including fluorescence quantum yields and lifetimes and
photochemical properties including singlet oxygen and photo-
degradation quantum yields of these Pc compounds were investi-
gated in DMSO. The quenching by fluorescence of newly synthesized
Pc compounds was also studied using by 1,4-benzoquinone.
properties and good thermal stability. The fully conjugated 18
p-
electronic structure of Pcs gives to structure good thermal and
optical stability. In addition, Pcs have intense absorption bands in
visible area. Thanks to these special properties, Pcs play an
important role in research of new high technological materials such
as solar cells [1], semiconductors [2], optical data storage devices
[3], laser dyes [4], photodynamic therapy agents [5], liquid crystals
[6], nonlinear optics [7], electrochromic displaying systems [8] and
molecular electronics [9].
Up to now, photophysical and photochemical behavior of Pc
compounds have been extensively studied [10,11] but there are a
few papers on photophysical and photochemical behavior of Pc
bearing triazole moieties [12,13]. Because of this, in this study, the
2. Experimental
2.1. Materials
All reactions were carried out under dry and oxygen free ni-
trogen atmosphere using Schlenk system. Dimethylformamide
* Corresponding author. Tel.: þ90 462 377 25 89; fax: þ90 462 325 31 96.
E-mail address: halit@ktu.edu.tr (H. Kantekin).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.08.029

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H.T. Akçay et al. / Journal of Organometallic Chemistry 745-746 (2013) 379e386
(DMF) was dried and purified as described by Perrin and Armarego
[20]. N-(3,5-dichlorophenyl)-5-methyl-3H-1,2,4-triazol-3-one (1)
[21] and N-(3,5-dichlorophenyl)-5-ethyl-3H-1,2,4-triazol-3-one (2)
[21], 4-nitrophthalonitrile (3) [22] were prepared as described in
the literature. 1,3-diphenylisobenzofuran (DPBF) and unsubstituted
ZnPc were purchased from Fluka and Aldrich, respectively.
The used equipments, the photophysical and photochemical
parameters were supplied as Supplementary information.
(DMSO) lmax/nm: [(10ꢁ5 , dm3 molꢁ1 cmꢁ1)]: 689 (5.19), 622
3
(4.57), 360 (4.83). MS (ESI), (m/z): Calculated: 1544 Found: 1545
[M þ H]þ.
7: Eluent for column chromatography: THF:methanol (100:2).
Yield: 58 mg (27.9%), mp > 300 ꢀC. Anal. calc. for C72H44Cl8
N20O4Zn:C, 53.97; H, 2.77; N, 17.48%; Found: C, 54.15; H, 2.59; N,
17.63%. IR (KBr tablet) ymax/cmꢁ1: 3096
y
(AreCH), 2980
(C]N), 1564, 1493, 1411, 1381, 1185, 1021. 1H
: ppm): 8.41e8.27 (bm, 12H/ArH), 7.86e7.76 (m,
12H/ArH), 2.93e2.81 (q, 8H/CH2), 1.41e1.35 (t, 12H/CH3). UVevis
(DMSO) lmax/nm: [(10ꢁ5 , dm3 molꢁ1 cmꢁ1)]: 690 (5.28), 623
y(alip-CH),
1716
y(C]O), 1591 y
NMR (DMSO-d6), (
d
2.2. Synthesis
3
2.2.1. 4-[N-(3,5-dichlorophenyl)-5-methyl-5-oxo-3H-1,2,4-triazol-
1-yl]phthalonitrile (4)
(4.54), 363 (4.83). MS (ESI), (m/z): Calculated: 1602 Found: 1625
[M þ Na]þ.
Compound (1) (2.44 g, 0.01 mol), 4-nitrophthalonitrile (3)
(1.73 g, 0.01 mol) and dry K2CO3 (1.38 g, 0.01 mol) were mixed in
dry DMF for 96 h. After evaporating the solvent, the compound (4)
was purified by crystallization in acetone/petroleum ether (1:1)
solvent system. Yield 2.96 g (80%). m.p: 214e215 ꢀC Anal. calc. for
8: Eluent for column chromatography: THF:methanol (100:2.5).
Yield: 62 mg (30.6%), mp > 300 ꢀC. Anal. calc. for C68H36Cl8
N20O4Mg:C, 54.26; H, 2.41; N, 18.61. Found: C, 54.13; H, 2.53; N,
18.72%. IR (KBr tablet) ymax/cmꢁ1: 3085
1715 y(C]O), 1590 y
y
(AreCH), 2993
(C]N), 1571, 1493, 1411, 1370, 1185, 1044, 1020.
1H NMR (DMSO-d6), (
: ppm): 8.44e8.33 (m, 8H/ArH), 8.21e8.16 (d,
4H/ArH), 7.80e7.73 (m, 12H/ArH), 2.24 (s, 12H/CH3). UVevis
(DMSO) lmax/nm: [(10ꢁ5 , dm3 molꢁ1 cmꢁ1)]: 689 (5.19), 623
y(alip-CH),
C
17H9Cl2N5O: C, 55.16; H, 2.45; N, 18.92; Found: C, 55.96; H, 2.22; N,
19.18. IR (KBr tablet) ymax/cmꢁ1: 3099
(AreCH), 3073 (AreCH),
2992 (alip-CH), 2943 (alip-CH), 2227 (C^N), 1719 (C]O), 1595
(C]N), 1584, 1570, 1497, 1436, 1417, 1399, 1380, 1303, 1266, 1190,
1161, 1113, 1044, 1023, 897, 874, 842, 801, 790, 731, 696, 668. 1H
NMR (DMSO-d6), ( : ppm): 8.50e8.48 (d, 1H/ArH), 8.40e8.37 (d,
1H/ArH), 8.26e8.24 (d, 1H/ArH), 7.86e7.83 (d, 1H/ArH), 7.81e7.76
(m, 2H/ArH), 2.24 (s, 3H/CH3). 13C NMR (DMSO-d6), (
: ppm):
d
y
y
y
y
y
3
y
(4.57), 362 (4.86). MS (ESI), (m/z): Calculated: 1504, Found: 1543
[M þ K]þ.
d
9: Eluent for column chromatography: THF:methanol (100:2.5).
Yield: 52 mg (25.6%), mp > 300 ꢀC. Anal. calc. for C72H44
Cl8N20O4Mg:C, 55.39; H, 2.84; N, 17.94. Found: C, 55.53; H, 3.03; N,
d
157.40, 153.32, 142.20, 135.67, 134.60, 129.78, 125.11, 122.42, 121.52,
120.78, 116.82, 115.53, 114.96, 110.11, 21.56. MS (ESI), (m/z): Calcu-
lated: 369; Found: 370 [M þ H]þ.
17.85. IR (KBr tablet) ymax/cmꢁ1: 3099
1717 y(C]O), 1593 y
y
(AreCH), 2995
(C]N), 1570, 1495, 1410, 1370, 1186, 1045, 1023.
1H NMR (DMSO-d6), (
: ppm): 8.42e8.23 (bm, 12H/ArH), 7.93e7.69
(bm, 12H/ArH), 2.90e2.82 (q, 8H/CH2), 1.42-1.34 (t, 12H/CH3). UVe
vis (DMSO) lmax/nm: [(10ꢁ5 , dm3 molꢁ1 cmꢁ1)]: 690 (5.33), 623
y(alip-CH),
d
2.2.2. 4-[N-(3,5-dichlorophenyl)-5-ethyl-5-oxo-3H-1,2,4-triazol-1-
yl]phthalonitrile (5)
3
(4.57), 364 (4.88). MS (ESI), (m/z): Calculated: 1560, Found: 1561
Compound (2) (2.58 g, 0.01 mol), 4-nitrophthalonitrile (3)
(1.73 g, 0.01 mol) and dry K2CO3 (1.38 g, 0.01 mol) were mixed in
dry DMF for 96 h. After evaporating the solvent, the compound (5)
was purified by crystallization in acetone/petroleum ether (1:1)
solvent system. Yield 2.96 g (77%). m.p: 225e228 Anal. calc. for
[M þ H]þ.
3. Results and discussion
3.1. Synthesis and characterization
C
18H11Cl2N5O: C, 56.27; H, 2.89; N, 18.23%; Found: C, 56.48; H, 2.71;
N,18.36. IR (KBr tablet) ymax/cmꢁ1: 3093
(AreCH), 2985 (alip-CH),
2943 (alip-CH), 2227 (C^N), 1721 (C]O), 1595 (C]N), 1573,
1493, 1450, 1420, 1387, 1370, 1339, 1277, 1192, 1167, 1148, 1104, 1071,
1059, 979, 900, 858, 843, 803, 735, 710, 666. 1H NMR (DMSO-d6), (
y
y
The synthetic pathway of the novel compounds is shown in
Scheme 1. The dinitrile compounds (4 and 5) were prepared from
the reactions between 4-nitrophthalonitrile and compounds 1
and 2, respectively, that have active eNH groups, by the catalyst
of K2CO3 [12]. All spectral data support the proposed structures
of compounds 4 and 5. According to IR spectroscopy data, new
vibration appeared at 2227 cmꢁ1, which belongs to the C^N
groups, supported the proposed structures of compounds 4 and
5. Two different tautomeric structures are possible for com-
pounds 1 and 2 (Fig. 1). In the IR spectra of the compound 4 and
5, C]O stretching vibrations were obtained at 1719 and
1721 cmꢁ1 indicated that the “keto” forms are more stable than
“enol” forms.
y
y
y
d:
ppm): 8.45e8.39 (m, 2H/ArH), 8.24e8.22 (d, 1H/ArH), 7.83e7.78
(m, 3H/ArH), 2.95e2.89 (q, 2H/CH2), 1.43e1.38 (t, 3H/CH3). 13C NMR
(DMSO-d6), (d: ppm): 156.14, 152.78, 141.32, 134.82, 134.51, 129.63,
124.03, 122.96, 121.44, 121.08, 116.14, 115.84, 115.12, 109.72, 26.22,
11.93. MS (ESI), (m/z): Calculated: 383; Found: 384 [M þ H]þ.
2.2.3. Synthesis of phthalocyanines (6e9)
The same procedure was used for the synthesis of the Pcs (6e9)
with literature [13]. MetalloPcs (6e9) were synthesized with
addition of 0.2 g of substituted phthalonitrile compounds (4 or 5)
and stoichiometric amounts of related anhydrous metal salts
(Zn(CH3COO)2; MgCl2) to the reaction media at reflux temperature
in n-pentanol (3 mL) and by the catalyst of DBU (3 drops) for 24 h.
After precipitating the crude products in methanol, the solid resi-
dues were purified by column chromatography, using silica gel as
support material.
In 1H NMR spectra of phthalonitrile compounds (4 and 5), the e
NH signals at 11.73 and 11.75 ppm for compounds 1 and 2,
respectively disappeared [21]. Presence of additional aromatic
protons indicated that substitution was accomplished. Stable mo-
lecular ion [M þ H]þ peaks m/z at 370 and 384 in the mass spectra
of compounds 4 and 5 were showed that target compounds were
successfully prepared. Also elemental analysis data of these com-
pounds (4 and 5) were satisfactory.
Researchers generally use substituted phthalonitriles or 1,3-
diimino-1H-isoindoles as starting materials for synthesis of Pcs.
In this work, phthalonitrile compounds (4 and 5) were also used
as starting compounds for synthesis of the metallo-Pcs (Zn, Mg)
due to mild reaction conditions. Characterization of new Pc
compounds was performed using by IR, 1H NMR, elemental
6: Eluent for column chromatography: THF:methanol (100:2).
Yield: 51 mg (24.5%), mp > 300 ꢀC. Anal. calc. for C68H36
Cl8N20O4Zn:C, 52.82; H, 2.35; N, 18.12; Found: C, 52.66; H, 2.52; N,
18.21. IR (KBr tablet) ymax/cmꢁ1: 3097
1722 y(C]O), 1593 y
y
(AreCH), 2982
(C]N), 1568, 1493, 1412, 1377, 1186, 1045, 1021.
1H NMR (DMSO-d6), (
: ppm): 8.45e8.36 (m, 8H/ArH), 8.22e8.14
(bd, 4H/ArH), 7.82e7.75 (m, 12H/ArH), 2.21 (s, 12H/CH3). UVevis
y(alip-CH),
d

H.T. Akçay et al. / Journal of Organometallic Chemistry 745-746 (2013) 379e386
381
Scheme 1. The synthetic route of the novel phthalonitrile (4 and 5) and phthalocyanine compounds (6e9).
analysis and UV/Vis, mass spectrometry. All spectral data support
the proposed structures (6e9). The IR spectra of all Pcs were in
good agreement with the proposed structures. The most impor-
tant proof of the cyclotetramerization of nitrile groups is the
absence of the eC^N vibrations at 2227 cmꢁ1 in IR spectra of the
substituted phthalonitrile compounds (4 and 5). The rest of the
spectra were not very different from that of the corresponding
phthalonitrile compounds (4 and 5).
The signals in the 1H NMR spectra of Pcs (6e9) that were
recorded in DMSO-d6 were broad because of the isomeric mixture
and probable aggregation at measured concentration. The spectra
of the compounds were very similar and the integral ratio of the
aromatic protons to aliphatic protons was similar to corresponding
phthalonitrile compounds (4 and 5). In addition, elemental analysis
results and mass spectra of the compounds 6e9 were good
agreement with proposed structure.

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H.T. Akçay et al. / Journal of Organometallic Chemistry 745-746 (2013) 379e386
2.5
2
1.5
1
Mg Pc (8)
Mg Pc (9)
0.5
0
Fig. 1. The possible tautomeric structures of compounds 1 and 2.
3.2. UVevis absorption spectra
300
400
500 600
Wavelength (nm)
700
800
Electronic spectra were mainly used for characterization of the
Pc compounds. Pcs display typical electronic spectra with two ab-
sorption regions, one is called Q-band and observed at around
Fig. 3. Electronic absorption spectra of phthalocyanine compounds 8 and 9 in DMSO at
1 ꢂ 10ꢁ5 M.
600e700 nm and arise from
pep* transitions from highest occu-
pied molecular orbital (HOMO) to the lowest unoccupied molecular
orbital (LUMO) of the Pc ring, other one is called B-band and
The excitation spectra of the triazole containing Pc compounds
were similar to absorption spectra of these compounds and both
were mirror images of the fluorescent spectra in DMSO. The
proximity of the wavelength of each component of the Q-band
absorption to the Q-band maxima of the excitation spectra for all
compounds suggests that the nuclear configurations of the ground
and excited states were similar and not affected by excitation in
DMSO.
observed at around 300e350 nm results from deeper
p levels-
LUMO transitions.
All substituted metalloPcs were soluble in most of organic sol-
vents such as tetrahydrofuran, dichloromethane, chloroform, N,N-
dimethylformamide, dimethylsulfoxide (DMSO) and pyridine. In
UVevis spectra of the metalloPcs (6e9) that were measured in
DMSO at 1 ꢂ10ꢁ5 M the Q-bands were observed at around 690 nm
with the shoulders at around 660 nm and the B-bands were
observed at around 362 nm (Figs. 2 and 3). The sharp absorption
bands were the evidence of non-aggregated species at measured
concentration [13].
Fig. 4 shows fluorescence emission, absorption and excitation
spectra of Pc compounds (6e9) in DMSO. Fluorescence emission
and excitation maximum peaks of compounds (6e9) in DMSO were
listed in Table 1. The triazole containing Pc compounds (6e9)
exhibited red-shifted Q-bands by approximately 18 nm compared
to the corresponding bands of the unsubstituted ZnPc. The
observed Stokes shifts of the studied Pc compounds (6e9) were
slightly lower than unsubstituted zinc Pc and typical of MPc com-
pounds in DMSO (Table 1). Fluorescence emission peaks were
observed at approximately 700 nm for Pc compounds in DMSO
(Table 1).
3.3. Fluorescence quantum yields and lifetimes
The fluorescence quantum yields (FF) and lifetimes of triazole
containing substituted zinc(II) and magnesium(II) Pcs (6e9) were
measured in DMSO and data were given in Table 2. The calculated
values were typical of MPc compounds. Although the FF values of
magnesium(II) Pcs were higher, the FF values of zinc(II) Pcs were
lower than unsubstituted zinc(II) Pcs. The substituted magnesiu-
m(II) Pcs (8 and 9) showed higher FF values than substituted zin-
c(II) Pcs (6 and 7). Due to size of magnesium (II) cation is smaller
than that of zinc (II), MgPcs have more fluorescenece property than
Zn(II)Pcs. The fluorescence lifetime can be introduced the average
staying time of a molecule in its excited state before emission and
this value is directly related to that of fluorescence quantum yield
values. The studied magnesium(II) Pcs showed higher fluorescence
lifetimes values than the studied zinc(II) Pcs, thus should be
accompanied by corresponding high fluorescence quantum yield
values of magnesium(II) Pcs.
2
The natural radiative lifetime (s0) and the rate constants for
1.8
1.6
fluorescence (kF) values in DMSO were also measured and given in
Table 2. The s0 values of the tetra-triazole containing substituted
zinc(II) and magnesium(II) Pc compounds (6e9) were longer than
unsubstituted zinc(II) Pc compound in DMSO. On the contrary,
these substituted Pc compounds (6e9) showed lower kF values
than unsubstituted zinc(II) Pc.
Zn Pc (6)
1.4
1.2
Zn Pc (7)
1
0.8
0.6
0.4
0.2
0
3.4. Singlet oxygen quantum yields
Singlet oxygen quantum yields (FD) were established in DMSO
using 1,3-diphenylisobenzofuran (DBPF) as a chemical quencher.
The decreasing of the absorbances of DPBF at 417 nm was moni-
tored using UVevis spectrometer. Any changes did not observe in
the Q-band intensities of the studied Pcs during the FD de-
terminations (Fig. 5, using compound 7 as an example in DMSO),
indicating that the studied Pc compounds were not degraded under
300
400
500
Wavelength (nm)
600
700
800
Fig. 2. Electronic absorption spectra of phthalocyanine compounds 6 and 7 in DMSO at
1 ꢂ 10ꢁ5 M.

H.T. Akçay et al. / Journal of Organometallic Chemistry 745-746 (2013) 379e386
383
700
0.25
0.2
0.15
0.1
0.05
0
500
450
400
350
300
250
200
150
100
50
0.25
c
600
Excitation
a
0.2
500
Emission
400
0.15
0.1
0.05
0
Excitation
Emission
300
200
100
0
Absorption
Absorption
0
500
550
600
650
Wavelength (nm)
700
750
800
850
500
550
600
650
700
750
800
850
Wavelength (nm)
1000
900
800
700
600
500
400
300
200
100
0
0.3
450
400
350
300
250
200
150
100
50
0.3
0.25
0.2
0.15
0.1
0.05
0
d
b
Excitation
0.25
0.2
0.15
0.1
0.05
0
Emission
Emission
Excitation
Absorption
Absorption
0
500
550
600
650
700
750
800
850
Wavelength (nm)
500
550
600
650 700
Wavelength (nm)
750
800
850
Fig. 4. Electronic absorption, excitation and emission spectra of (a) for compound 6, (b) for compound 7, (c) for compound 8 and (d) for compound 9 in DMSO (lex ¼ 660 nm).
light irradiation (30 Volt) during singlet oxygen determinations.
The FD values of the newly synthesized substituted Pc compounds
(6e9) and unsubstituted zinc(II) Pc were given in Table 2. The
studied Pc compounds showed lower FD values than unsubstituted
zinc(II) Pc except for zinc(II) Pc compound 7. The substituted zinc(II)
Pc compounds (6 and 7) showed higher FD values than magne-
sium(II) Pc counterparts mostly due to the lower FF values of zin-
c(II) Pcs than magnesium counterparts as explained above. The
length of alkyl chain (methyl or ethyl) on the triazole group was
also effected singlet oxygen generation of studied Pc compounds.
When the ethyl group substituted on the triazole group, higher
singlet oxygen production was observed among the studied Pc
compounds.
The photodegradation cause some spectral changes in UVevis
spectra of the Pcs (6e9). An example of these spectral changes is
shown in Fig. 6 (using compound 8 in DMSO). Although decreasing
the absorption bands of Pcs (6e9) in the electronic spectra, there is
no change in the form of the absorption bands refers photo-
degredation instead of phototransformation. The degradation de-
gree of the molecules under light irradiation is confirmed as
photodegradation quantum yield (Fd) and these values of studied
Pc compounds (6e9) in DMSO were given in Table 2. All the com-
pounds showed about the same stability with Fd of the order of
10ꢁ5. While the stable Pc compounds show Fd values as low as
10ꢁ6, the order of 10ꢁ3 had been reported for the unstable Pc
compounds [11]. The Fd values for the triazole containing zinc(II)
and magnesium(II) Pcs were similar with Pc derivatives having
different substituents on the Pc ring in the literature [11]. The
studied zinc(II) (6, 7) and magnesium(II) (8, 9) Pc compounds
showed lower Fd values compared to unsubstituted zinc(II) Pc
(ZnPc). It means the substitution of the Pc framework with triazole
3.5. Photodegradation studies
Degradation of the molecules under light irradiation can be
given hints about their photostability and the determination of the
photostability of the molecules is especially important for use their
photocatalytic applications.
Table 2
Photophysical and photochemical data of the unsubstituted and the substituted
phthalocyanine compounds in DMSO.
Table 1
Absorption, excitation and emission spectral data for the unsubstituted and the
substituted phthalocyanine compounds in DMSO.
0 (ns) kF (sꢁ1) (ꢂ108) Fd (ꢂ10ꢁ5
)
FD
a
Compound FF
sF (ns)
s
6
7
8
9
0.18
1.79
1.35
2.44
2.62
9.93
8.28
8.90
6.90
6.80c
1.01
1.21
1.12
1.45
1.47c
0.98
1.99
2.42
2.53
2.61c
0.55
0.74
0.27
0.60
0.67d
Compound
Q-band
lmax, (nm)
log
3
Excitation
lEx, (nm)
Emission
lEm, (nm)
Stokes shift
DStokes, (nm)
0.16
0.27
0.38
6
7
8
9
689
690
689
690
672
5.19
692
692
692
692
672
700
700
697
697
682
8
8
9
9
10
5. 28
5.19
5.33
5.14
ZnPc
0.20b 1.22c
a
kF is the rate constant for fluorescence. Values calculated using kF
Data from Ref. [24].
Data from Ref. [23].
¼
FF/sF.
b
c
ZnPca
a
d
Data from Ref. [23].
Data from Ref. [25].

384
H.T. Akçay et al. / Journal of Organometallic Chemistry 745-746 (2013) 379e386
Fig. 5. UVevis spectra changes during the determination of singlet oxygen quantum yield. This determination was for compound 7 in DMSO at a concentration of 1 ꢂ10ꢁ5 M (Inset:
Plot of DPBF absorbance versus time).
containing substituents increased the photostability of the com-
pounds under light irradiation. The studied substituted zinc(II) Pcs
(6 and 7) showed lower Fd values compared to magnesium(II)
counterparts (8 and 9) in DMSO. For this reason, the studied Pcs
containing zinc(II) as central metal ion in the Pc cavity are more
stable compared to magnesium containing Pcs due to more sensi-
tive of magnesium atom against to light irradiation.
determined decreasing of the emission spectra of these compounds
by addition of increasing amounts of 1,4-benzoquinone (BQ) in
DMSO. The quenching between Pcs and BQ was found to obey
SterneVolmer kinetics, which is consistent with diffusion
controlled bimolecular reactions. Fig. 7 shows the reducing of the
emission spectra for compound 8 due to the quenching by BQ in
DMSO as an example. The slope of the plots shown in Fig. 8 gave
SterneVolmer constant (KSV) values and these values were listed in
Table 3. The KSV values of the triazole containing substituted zinc Pc
compounds (6 and 7) were lower than unsubstituted ZnPc in
DMSO. The zinc(II) compounds (6 and 7) showed lower KSV value
than the magnesium(II) counterparts (8 and 9) in DMSO could be
3.6. Fluorescence quenching studies by 1,4-benzoquinone [BQ]
The quenching of fluorescence for the tetra-substituted zinc(II)
and magnesium (II) Pc compounds containing triazole groups was
1.8
1.6
2
1.5
1.4
y =-0.0001x + 1.6753
1
R² = 0.9995
1.2
1
0.5
0
0 sec
600 sec
1200 sec
1800 sec
2400 sec
3000 sec
3600 sec
0.8
0.6
0.4
0.2
0
300
350
400
450
500
550
600
650
700
750
800
Wavelength (nm)
Fig. 6. UVevis spectral changes during the photodegradation studies of the compound 8 in DMSO showing the disappearance of the Q-band at 10 min intervals. (Inset: Plot of
absorbance versus time). 300 W General Electric quartz line lamp was used as a light source. Power density was 18 mW/cm2 and used energy was 100 W.

H.T. Akçay et al. / Journal of Organometallic Chemistry 745-746 (2013) 379e386
385
Table 3
1000
800
600
400
200
0
BQ = 0
Fluorescence quenching data for the unsubstituted and the substituted phthalocy-
anine compounds in DMSO.
Compound
KSV (Mꢁ1
)
kq/1010(dm3 molꢁ1 sꢁ1
)
6
7
8
9
16.71
12.55
35.09
26.95
31.90
0.94
0.93
1.44
1.03
2.61
ZnPca
a
BQ = saturated
Data from Ref. [23].
compared to zinc(II) Pcs (6e7) in DMSO due to the smaller nature of
the Mg atom than Zn atom in the Pc cavity. The amount of the
singlet oxygen is very important for the prediction of PDT activity of
photosensitizers. All studied triazole containing Pc compounds
generated quite lot singlet oxygen in DMSO. Especially, the zinc(II)
Pc compound 7 showed highest FD value among the studied Pcs.
The studied zinc(II) (6e7) Pc compounds were stable to degradation
under light irradiation compared to unsubstituted zinc Pc (ZnPc)
and the substituted zinc(II) Pc compounds (6 and 7) were more
stable than magnesium(II) Pcs in DMSO. The SterneVolmer constant
(KSV) and the bimolecular quenching constant (kq) values of the
substituted magnesium(II) Pc compounds (8 and 9) were found
higher than the substituted zinc(II) Pc compounds in DMSO. The
fluorescence quenching between studied Pcs and BQ was proceed
via diffusion-controlled mechanism since bimolecular quenching
670
690
710
730
750
770
790
Wavelength (nm)
Fig. 7. Fluorescence emission spectral changes of the compound 8 (1 ꢂ 10ꢁ5 M) by
addition of different concentrations of BQ in DMSO. [BQ] ¼ 0, 0.008, 0.016, 0.024, 0.032,
0.04 M.
due to lower metal size of magnesium than zinc. The obtained
bimolecular quenching constant (kq) values for all studied Pc
compounds (6e9) were lower than unsubstituted zinc(II) Pc
(ZnPc). When compared to kq values among the studied Pcs,
magnesium(II) Pc compounds had higher values than zinc(II) Pcs.
The increase of the length of the alkyl chain from methyl to ethyl on
the substituents decreased both the KSV and kq values of the studied
compounds. The bimolecular quenching rate constants were ob-
rate constants were obtained to be close to the limits to 1010
M .
ꢁ1 sꢁ1
These properties give an indication of the potential of the com-
pounds as photosensitizers in applications where singlet oxygen is
required, especially compound (7) can be good candidate as a
photosensitizer for PDT application.
tained to be close to the diffusion-controlled limits, w1010
M .
ꢁ1 sꢁ1
4. Conclusions
Acknowledgments
This work described the synthesis, spectral characterization,
photophysical and photochemical properties of newly synthesized
peripherally tetra-substituted zinc(II) and magnesium(II) Pc com-
pounds containing N-(3,5-dichlorophenyl)-5-methyl-3H-1,2,4-
triazol-3-one (1) or N-(3,5-dichlorophenyl)-5-ethyl-3H-1,2,4-triazol
-3-one (2) groups. Elemental analyses, IR, UV/VIS, 1H NMR and mass
spectra confirmed the proposed structure of the compounds. The
substitution of Pc framework with N-(3,5-dichlorophenyl)-5-
methyl-3H-1,2,4-triazol-3-one (1) or N-(3,5-dichlorophenyl)-5-
ethyl-3H-1,2,4-triazol-3-one (2) groups increased the wavelength
of the Q-band. The fluorescence quantum yield and fluorescence
lifetime values were found higher for magnesium(II) Pcs (8e9)
This study was supported by Research Fund of Karadeniz
Technical University (Project No: 2010.111.002.5).
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2013.08.029.
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