Phthalocyanines formed from several precursors: synthesis, characterization, and comparative fluorescence and quinone quenching

Article abstract of DOI:10.1080/00958972.2018.1471686

We have synthesized a new phthalonitrile with different substituents in 4- and 5-positions (1). Cyclotetramerization of 1 yielded phthalocyanines with cobalt(II) (2), zinc(II) (3), gallium(III)chloride (4), and indium(III)chloride (5) containing diethylam

Full text of DOI:10.1080/00958972.2018.1471686

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Phthalocyanines formed from several precursors:
synthesis, characterization, and comparative
fluorescence and quinone quenching
H. R. Pekbelgin Karaoğlu, H. Yasemin Yenilmez & Makbule B. Koçak
To cite this article: H. R. Pekbelgin Karaoğlu, H. Yasemin Yenilmez & Makbule B. Koçak
(2018): Phthalocyanines formed from several precursors: synthesis, characterization, and
comparative fluorescence and quinone quenching, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2018.1471686
To link to this article: https://doi.org/10.1080/00958972.2018.1471686
Published online: 11 May 2018.
Submit your article to this journal
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=gcoo20

Journal of Coordination Chemistry, 2018
https://doi.org/10.1080/00958972.2018.1471686
Phthalocyanines formed from several precursors: synthesis,
characterization, and comparative fluorescence and quinone
quenching
H. R. Pekbelgin Karaoğlu, H. Yasemin Yenilmez and Makbule B. Koçak
department of Chemistry, istanbul technical university, istanbul, turkey
ABSTRACT
ARTICLE HISTORY
received 20 february 2018
accepted 16 april 2018
We have synthesized a new phthalonitrile with different substituents
in 4- and 5-positions (1). Cyclotetramerization of
1 yielded
phthalocyanines with cobalt(II) (2), zinc(II) (3), gallium(III)chloride
(4), and indium(III)chloride (5) containing diethylamino-phenoxy
and hexylsulfanyl substituents on each benzene unit. Elemental
analyses, Fourier transform infrared spectra, 1H-nuclear magnetic
resonance spectra, mass spectra, and ultraviolet-visible spectra were
used for characterization of the phthalocyanines. The aggregation
behavior of the zinc phthalocyanine derivative was studied in different
concentrations. Also four chloro and four diethyllaminophenoxy
substituted zinc phthalocyanine (6) and octa-diethylaminophenoxy
substituted zinc phthalocyanine (7) were synthesized. These
phthalocyanines (3, 6, and 7) were compared for electronic absorption
spectra, fluorescence quantum yields, fluorescent lifetimes, and
fluorescence quenching in the presence of benzoquinone. The
fluorescence quantum yield gives the efficiency of the fluorescence
process. The fluorescence lifetime is an important parameter for
practical applications of fluorescence such as fluorescence resonance
energy transfer and fluorescence-lifetime imaging microscopy.
KEYWORDS
Phthalocyanine;
diethylaminophenoxy;
aggregation behavior;
fluorescence; quinone
1. Introduction
Phthalocyanines constitute an aromatic macrocycle with delocalized two-dimensional
18π-electron systems exhibiting unparalleled optical, electronic, and catalytic properties.
They are thus used in many different scientific and technological applications, such as
CONTACT makbule B. Koçak
mkocak@itu.edu.tr
© 2018 informa uK limited, trading as taylor & francis Group

2
H. R. P. KARAOĞLU ET AL.
photoconducting agents in photocopying devices, chemical sensors, molecular metals, liquid
crystals, nonlinear optical materials, and catalysts [1–4]. To promote solubilization of phtha-
locyanines in these applications is crucial. Because π-stacking, referred to as aggregation, is
present between planar macrocycles, phthalocyanines without substitution are poorly sol-
uble in common organic solvents, including chloroform, ethanol, or tetrahydrofuran, as well
as in water. The solubility is enhanced dramatically by introduction of substituents on the
periphery (β) or non-periphery (α) of the phthalocyanine ring, and by the presence of axial
substituents in the metal center since the distances between stacks are increased [5–15].
The size, nature, and positions of substituents have positive effects on the solubility of
the final structures and they improve chemical and physical properties. Peripheral octa-sub-
stituted phthalocyanines are formed from phthalonitrile derivatives with two identical or
different substituents at the 4- and 5-positions of the ring. The superior solubility of those
with two different substituents to the octa-substituted phthalocyanines is well known,
because four constitutional isomers are formed, and a high dipole moment from the unsym-
metrical arrangement occurs [16, 17].
A red-shift in the phthalocyanine is observed in cases when electron-donating substituents
are available at non-peripheral positions of phthalocyanine compounds, whereas minor shifts
are observed after peripheral substitution [18, 19]. Phthalocyanines bearing axial substituents
on the metal ions also induce a bathochromic shift of the Q-band maximum values.
Due to advantages, such as high selectivity, direct and rapid application, and considerable
controllability, microwave heating is attractive as an alternative to the conventional thermal
synthesis [20].
Owing to the difficult preparation of phthalonitrile precursors with different substituents,
phthalocyanines with two or three different substituents on each aromatic ring have been
rarely obtained. In previously published studies, we have described the synthesis of octa-
and hexadeca-substituted phthalocyanines [16, 20, 21].
In the present paper, we report the synthesis of octa-substituted metallophthalocyanines
bearing four diethylaminophenoxy and four hexylsulfanyl substituents in peripheral posi-
tions, adjacent to each other. The introduction of diethylaminophenoxy and hexylsulfanyl
substituents in peripheral positions and an axial chloro ligand (for gallium (4) and indium
(5) Pcs) increase the solubility of phthalocyanines. Herein, we also examined the aggregation
behaviors of the zinc phthalocyanine (3) in different concentrations of CHCl3. The octa-sub-
stituted metallophthalocyanines were obtained by either conventional thermal processing
or microwave heating. We report here the photophysical (fluorescence quantum yields and
lifetimes) and quenching properties of 3, 6 and 7 in DMF. The photophysical and quenching
properties of a newly synthesized zinc phthalocyanine were compared with those of previ-
ously synthesized zinc phthalocyanines (6, 7) [16, 21, 22].
2. Experimental
2.1. Materials and equipment
All chemicals and solvents were reagent grade from commercial suppliers. Molecular sieves
were used to draw extra water from the solvents. Thin layer chromatography on silica was used
for testing whether the reaction has finished or not. 1-Chloro-3,4-dicyano-6-[3-(diethylamino)
phenoxy]benzene and its corresponding zinc phthalocyanines 6 and 7 were synthesized
according to the literature [16, 21, 22].

JOURNAL OF COORDINATION CHEMISTRY
3
IR spectra were obtained, on a Universal attenuated total reflectance (UATR) module, with
a Perkin Elmer Spectrum One FT-IR spectrometer and electronic spectra were obtained on
1
a Scinco LabPro Plus UV/Vis spectrophotometer. H NMR spectra were acquired with an
Agilent VNMRS spectrometer, operating at 500 MHz, with TMS as an internal standard. A
Micromass Quattro LC/ULTIMA LC–MS/MS spectrometer was used to record the mass spectra.
AThermo Finnigan Flash EA 1112 apparatus was used for elemental analyses at 950–1000 °C.
For fluorescence measurements, a Perkin Elmer LS55 fluorescence spectrophotometer and
for UV/Vis spectra, a Scinco SD 1000 spectrophotometer, were used.
2.2. Synthesis
2.2.1. 4-[3-(Diethylamino)phenoxy]-5-(hexylthio)phthalonitrile (1)
1-Chloro-3,4-dicyano-6-[3-(diethylamino)phenoxy]benzene (0.500 g, 1.54 mmol) was dis-
solved in 10.00 cm3 of dry DMF, and 0.83 g of n-hexanethiol (2.3 mmol) was added. The
mixture was stirred for 15 min, and finely ground anhydrous 2.3 g cesium carbonate (Cs2CO3;
6.14 mmol) was added in small portions during 2 h with stirring. The temperature of the
reaction mixture was set to 45 °C for 48 h under N2. The mixture was cooled to room tem-
perature, and the mixture was poured into cracked ice-water mixture (100 cm3) and the
precipitate that formed was filtered, washed with copious amounts of water until the filtrate
had a neutral pH, and dried in vacuo. The brown product was purified by column chroma-
tography with silica gel as stationary phase, eluting with n-hexane:ethyl acetate (5:1, v:v).
Compound 1 was soluble in THF, chloroform, dichloromethane, DMF, and DMSO. Yield:
25%. 1H NMR (CDCl3): δ 7.57 (s, H–Ar, H), 7.47 (d, H–Ar, H), 6.96 (s, H–Ar, H), 6.57 (d, H–Ar, H),
6.29 (s, H–Ar, H), 6.24 (d, H–Ar, H), 3.34 (q, N–CH2, 4H), 2.98 (t, S–CH2, 2H), 1.76 (q, S–CH2–CH2,
2H), 1.50–1.32 (q, CH2, 4H), 1.16 (t, CH3, 6H), 0.90 (t, CH3, 3H); IR (ν, cm−1): 3076 (H–Ar), 2959,
2928 (H-Aliphatic), 2230 (C≡N), 1563 (Ar C=C), 1275 (Ar C–N), 1247 (Ar–O–Ar); C24H29N3OS
calculated %: C, 70.73; H, 7.17; N, 10.31; O, 3.93; S, 7.87. Found %: C, 70.95; H, 7.25; N, 10.29;
MS [m/z]: 407 [M]+, 392 [M–CH3]+, 322 [M–C6H13]+, 290 [M-SC6H13]+; m.p.: 137.5 °C.
2.2.2. General procedures for phthalocyanine derivatives (2–5)
A mixture, containing 1 (0.150 g, 0.37 mmol), anhydrous metal salts (0.0925 mmol) [CoCl2,
12 mg; Zn(CH3COO)2, 16.8 mg] in hexan-1-ol (2.0 mL) and a 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU, catalytic amount) were charged into a glass tube under nitrogen.The mixture was heated,
by stirring efficiently, at 160 °C for 24 h. Instead of conventional heating, microwave heating
was used for gallium and indium phthalocyanines. A mixture having 1 (0.150 g, 0.37 mmol)
and dried gallium(III)chloride (16 mg, 0.0925 mmol) or indium(III)chloride (20.4 mg,
0.0925 mmol) in freshly distilled quinoline (2 mL) (for 4) or hexan-1-ol (for 5) in the presence
of a drop of DBU was subjected to irradiation by microwave at 170 °C for 25 min. After cooling
to room temprature, the resulting green suspension was turned into a precipitate with meth-
anol or a mixture of methanol and water. The precipitate was isolated from the suspension
and washed thoroughly with the same solvents. Pure phthalocyanine derivatives were obtained
by column chromatography on silica gel, which is the stationary phase, using a suitable solvent
as eluent. Colors: dark green. Solubility: very soluble in chloroform, THF, DMF, and DMSO.
2.2.2.1. 2,9,16,23-Tetrakis-[3-(diethylamino)phenoxy]-3,10,17,24-tetrahexylsulfanyl-
phthalocyaninatocobalt(II) (2). The crude product was purified by column chromatography,
with silica gel as stationary phase, using THF:n-hexane (20:1, v:v) as eluent. Yield: 36 mg,

4
H. R. P. KARAOĞLU ET AL.
23%; IR, γmax (cm−1): 3069 (C–H, aromatic) 2957–2926 (C-H aliphatic), 1230 (Ar-O-Ar); UV–vis
(CHCl3): λmax = 315, 627, 695; C96H116CoN12O4S4 calculated %: C, 68.26; H, 6.92; N, 9.95; found
%: C, 68.30; H, 6.96; N, 9.92; MS: (ESI) m/z 1687.91 [M−H]+.
2.2.2.2. 2,9,16,23-Tetrakis-[3-(diethylamino)phenoxy]-3,10,17,24-tetrahexylsulfanyl-
phthalocyaninatozinc(II) (3). The green product was subjected to column chromatography
on silica gel (stationary phase) using ethyl acetate:n-hexane (5:1, v/v) as eluent. Yield: 42 mg,
27%; IR, γmax (cm−1): 3068 (C–H, aromatic) 2956–2924 (C–H aliphatic), 1227 (Ar–O–Ar); UV–Vis
(CHCl3): λmax (nm) = 361, 626, 698; 1H NMR (CDCl3) δ: 7.19–6.52 (m, Ar–H, 24H), 3.40 (br, N–
CH2, S–CH2, 24H), 1.94 (br, S–CH2–CH2, 8H), 1.60 (br, Aliph–CH2, 24H), 1.20 (t, CH3, 24H), 0.93
(t, CH3, 12H); C96H116ZnN12O4S4 calculated %: C, 68.00; H, 6.90; N, 9.91; found %: C, 68.03; H,
6.88; N, 9.95. MS: (ESI) m/z 1694.25 [M]+.
2.2.2.3. 2,9,16,23-Tetrakis-[3-(diethylamino)phenoxy]-3,10,17,24-tetrahexylsulfanyl-
phthalocyaninato(chloro)gallium(III) (4). Purification was done with column
chromatography (silica gel as adsorbent) with THF:methanol (1:1, v:v) as eluent. Yield: 11 mg,
7%; IR, γmax (cm−1): 3066 (C–H, aromatic) 2957–2919 (C–H aliphatic), 1258 (Ar–O–Ar); UV–vis
(CHCl3): λmax (nm) = 359, 715; 1H NMR (CDCl3 δ): 7.39–6.58 (m, Ar–H, 24H), 3.48 (br, N–CH2,
S-CH2, 24H), 1.72 (br, S–CH2–CH2, 8H), 1.56 (br, Aliph–CH2, 24H), 0.99 (br, CH3, 36H) ppm;
C96H116ClGaN12O4S4 calculated %: C, 66.44; H, 6.74; N, 9.69; found %: C, 66.46; H, 6.72; N, 9.67.
2.2.2.4. 2,9,16,23-Tetrakis-[3-(diethylamino)phenoxy]-3,10,17,24-tetrahexylsulfanyl-
phthalocyaninato(chloro)indium(III) (5). The crude product was purified with column
chromatography twice (silica gel as adsorbent, THF:methanol 25:1, v:v and THF:ethyl acetate
1:1, v:v as eluents). Yield: 23 mg, 14%; IR, γmax (cm−1): 3069 (C–H, aromatic), 2954–2924
(C–H aliphatic), 1261–1228 (Ar–O–Ar); UV–vis (CHCl3): λmax (nm) = 362, 728; 1H NMR (CDCl3
δ): 7.53–6.84 (m, Ar–H, 24H), 3.44 (br, N–CH2, S–CH2, 24H), 1.94 (br, S–CH2–CH2, 8H), 1.57 (br,
Aliph–CH2, 24H), 0.96 (br, CH3, 36H) ppm; C96H116ClInN12O4S4 calculated %: C, 64.76; H, 6.57;
N, 9.44; found %: C, 64.79; H, 6.60; N, 9.42%; MS: (ESI) m/z 1803 [M + Na]+, 1710 [M–5CH2]+,
1675 [M–5CH2–Cl]+.
2.3. Photophysical parameters
2.3.1. Fluorescence quantum yields (ΦF) and fluorescence lifetimes (τF)
The comparative method for fluorescence quantum yields of zinc phthalocyanines (3, 6, and
7) was used [23]. Unsubstituted ZnPc, with a ΦF value of 0.17 [24], was employed as the
standard in DMF.
FAStdꢀ2
� = � (Std)
(1)
F
F
FStdAꢀS2td
Natural radiative lifetimes, designated as τ0, were determined with PhotochemCAD software,
employing the Strickler-Berg equation [25]. The evaluation was performed using Equation (2).
ꢀF
� =
(2)
F
ꢀ0

JOURNAL OF COORDINATION CHEMISTRY
5
2.3.2. Benzoquinone (BQ)-based fluorescent quenching
Fluorescence quenching experiments with the substituted zinc phthalocyanines (3, 6, and
7) were performed by adding a series of concentrations of benzoquinone to a constant
concentration of the complex. The Stern-Volmer constants of the studied compounds were
found by Equation (3) [26]. The I0/I ratios were calculated and are shown as a plot against
[BQ] by using Equation (3), and KSV is determined from the slope.
I0
= 1 + KSV[BQ]
(3)
I
The bimolecular quenching constant was found with Equation (4).
Ksv = kq ∗ ꢀF
(4)
3. Results and discussion
3.1. Synthesis and characterization of the compounds
The procedure for synthesis of phthalocyanines carrying four diethylamino-phenoxy and
four hexylsulfanyl substituents at peripheral positions is depicted in Scheme 1, whereas
Figure 1 represents phthalocyanine derivatives 6 and 7 which were synthesized according
to methods described [16, 21, 22]. The precursor material we chose for the synthesis of the
mentioned phthalocyanines was 1-chloro-3,4-dicyano-6-[3-(diethylamino)phenoxy]ben-
zene, whose synthesis and characterization were previously described by our group [16].
First, this compound was reacted with n-hexanethiol in the presence of cesium carbonate
in anhydrous DMF at 45 °C for 48 h to yield 4-[3-(diethylamino)phenoxy]-5-(hexylthio)
phthalonitrile (1). The reaction of this new disubstituted phthalonitrile 1 with metal salts
(cobalt(II) chloride, zinc acetate) in hexan-1-ol at 160 °C for 24 h in nitrogen yielded the
respective metallophthalocyanines (2 and 3) (Scheme 1). The syntheses of gallium and
indium phthalocyanines (4 and 5) were achieved by treatment of 1 with anhydrous metal
salts (GaCl3 for 4 and InCl3 for 5) and DBU as a catalyst in suitable solvents (quinoline for 4
and hexan-1-ol for 5) at 170 °C in a sealed tube under microwave irradiation for 25 min
(Scheme 1). The new phthalocyanines were obtained pure through silica gel column chro-
matography by using different mixtures of solvents [THF:hexane (20:1, v:v) for cobalt (2),
ethyl acetate:n-hexane (5:1, v:v) for zinc (3), THF:methanol (1:1, v:v) for gallium (4),
THF:methanol (25:1, v:v) and THF:ethyl acetate (1:1, v:v) for indium (5) phthalocyanines].
As expected, the disubstituted phthalonitrile containing differing substituents in the 4-
and 5-positions generated metal phthalocyanines (2–5) which constitute a mixture of four
positional isomers. These isomers are mentioned by their molecular symmetry (Cs, D2h, C2v,
and C4h). No separation of these four structural isomers was achieved, employing common
column chromatography or by recrystallization was reported. Therefore, we did not attempt
to separate the structural isomers 2–5.
The lack of solubility of unsubstituted phthalocyanines in solvents, such as chloroform,
methanol, or THF, is well known. Peripheral, non-peripheral, and/or axial substituents can
dramatically increase the overall solubility of phthalocyanines in water or common solvents.
In general, the presence of a pair of different substituents in each aromatic ring results in
better solubility than two identical substituents in the aromatic ring. Thus, due to the pres-
ence of four constitutional isomers, phthalocyanines have enhanced solubility. Therefore,
2–5 have exceedingly high solubility in chloroform, THF, DMF, and DMSO.

6
H. R. P. KARAOĞLU ET AL.
Scheme 1. synthesis of 2–5. i. na2Co3, dmf, 50 °C, 96 h, ii. Cs2Co3, dmf, 45 °C, 48 h, iii. 1-hexanol, 24 h,
160 °C, dBu (for 2, 3); quinoline, dBu, 170 °C, 25 min, mW (for 4); 1-hexanol, dBu, 170 °C, 25 min, mW (for 5).
Several spectroscopic techniques were employed to elucidate the structures of the newly
obtained compounds, including proton and carbon nuclear magnetic resonance spectros-
copy, Fourier transform infrared spectroscopy, ultraviolet-visible spectrophotometry, and

JOURNAL OF COORDINATION CHEMISTRY
7
matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The spectral
data for 2–5 were consistent with the formulations suggested. Vibrations in the relevant IR
spectrum at 2230 cm−1 for 1 indicated the presence of a C≡N group, whereas those at
1247 cm−1 implied the availability of a C–O–C group. Stretches were also observed at
3076 cm−1 and 2959, 2928 cm−1 for aromatic and aliphatic groups, respectively. The FT-IR
spectra of phthalocyanines are generally almost identical. The characteristic vibrations for
the ether groups were observed at ca. 1230 cm−1 for all phthalocyanine derivatives
studied.
In the proton nuclear magnetic resonance spectra of the phthalocyanine precursor 1 in
deuterio-chloroform, three singlets were displayed at 7.57, 6.96, and 6.29 ppm, three dou-
blets at 7.47, 6.57 and 6.24 ppm, belonging to aromatic protons in the system. The N–CH2
and N–CH2–CH3 protons of ethylaminophenoxy moiety were observed as a quartet at
3.34 ppm and a triplet at 1.16 ppm, respectively. Aliphatic protons of the hexylthio group
were detected at 2.98 ppm as a triplet, at 1.76 ppm as a quartet, at 1.50–1.32 ppm as another
quartet, and at 0.90 ppm as a triplet. Due to the use fact of high concentrations of phthalo-
cyanines for recording 1H NMR spectra of 2–5, the resulting peaks are quite broad, indicating
high aggregation of the macrocycles. Another reason for the broad signals in the final phtha-
locyanine compounds is the presence of positional isomers, which are substituted
differently.
The mass spectral results confirmed the presence of the structures we proposed. For 2
and 3, the molecular ion peaks were observed at m/z: [M–H]+ 1687.91 and m/z: [M]+ 1694.25,
respectively. The mass spectrum of 5 showed peaks, most important of which were at m/z:
1803 for [M+Na]+, m/z: 1710 for [M–5CH2]+, and m/z: 1675 for [M–5CH2–Cl]+. The results of
the elemental analyses were in agreement with the percentages of carbon, hydrogen, and
nitrogen in the structures of all phthalocyanines.
3.2. Electronic absorption (ground-state) and fluorescence spectra
Absorption spectra are useful for obtaining information on whether a phthalocyanine has
been formed. Generally, most phthalocyanines have bands in the visible region at 600–
700 nm (referred to as the Q-band) resulting from the HOMO→LUMO (π→π*) transitions, as
well as in the ultraviolet region at 300–350 nm (B-band) due to transitions between lower
π-levels to LUMO.
Figure 1. Zinc phthalocyanine derivatives.

8
H. R. P. KARAOĞLU ET AL.
The electronic absorption spectra (ground-state) of 2–5 dissolved in chloroform showed
the presence of monomeric species along with a single (narrow) Q-band at ca. 695–728 nm
and a B band at ca. 315–362 nm. The Q-bands of the synthesized phthalocyanines were
observed at 695 nm (2), 698 nm (3), 715 nm (4) and 728 nm (5) (in CHCl3) (Figure 2). We also
detected the vibronic bands of 2–5 at 627, 626, 644 and 651 nm, correspondingly, all of which
correlated with n–π* transitions [27]. Because of the central metal ion nature, the Q-band
maxima of the series of compounds were in the following descending order In >Ga>Zn>Co.
Within the scope of this work, we studied the aggregation behavior of zinc phthalocyanine
in chloroform with different concentrations (Figure 3), which were found to conform to the
Beer-Lambert Law at concentrations within the range 4 × 10−6 – 14 × 10−6 mol dm−3 for 3.
The increase in the concentration of the substance causes parallel increase of the intensity
of the Q band, and no new band due to aggregation is observed [28–30].
1
0.8
ZnPc
0.6
CoPc
InPc
0.4
0.2
0
GaPc
300
400
500
600
700
800
Wavelength / nm
Figure 2. uV spectra of CoPc (2), ZnPc (3), GaPc (4) and inPc (5) in ChCl3.
5
5
4.5
4.5
4
y = 310581x
R² = 0.9721
3.5
4
3
2.5
3.5
2
1.5
A
B
C
D
E
F
3
1
0.5
2.5
2
0
0.00E+00
5.00E-06
1.00E-05
1.50E-05
Concentration/M
1.5
1
G
0.5
0
300
400
500
600
700
800
Wavelength / nm
Figure 3. absorption spectra of ZnPc (3) in ChCl3 at different concentrations: 14 × 10−6 (a), 12 × 10−6 (B),
10 × 10−6 (C), 8 × 10−6 (d), 6 × 10−6 (e) and 4 × 10−6 (f) mol dm−3.

JOURNAL OF COORDINATION CHEMISTRY
9
The electronic absorption spectra of 3 in various solvents (chloroform, THF, DMF, and
DMSO) were also investigated (Figures 4 and 5). The bathochromic shift of the Q band for 3
was due to the effect of the solvent and was changed in the following order: ethyl acetate
<THF<DMF<chloroform<DMSO. The electronic absorption spectra of 3 in these solvents
were examined by the Bayliss method [30]. The plot of the frequency of the Q band versus
(n2−1)/(2n2+1) function is depicted in Figure 5, in which n is the refractive index of the solvent
used. There is a linear response owing to the solvent used, caused by the solvent itself, not
by a ligation effect [31].
In comparison of the diethylaminophenoxy- and chlorine-substituted phthalocyanines
reported earlier with the compounds we synthesized in the present paper [16, 21], we found
that substitution of the chloro-group for hexylsulfanyl moiety clearly yielded a red-shift of
the Q-band maxima at approximately 15–21 nm for 2 and 3 (Figure 6). The Q-band maxima
of the gallium and indium phthalocyanines (4 and 5) were further bathochromically shifted,
when compared to 2 and 3 having divalent metal ions in the core; the reason of this might
2.0
DMF
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
DMSO
EtAc
THF
CHCl3
300
400
500
600
700
800
Wavelength / nm
Figure 4. absorption spectra of ZnPc (3) in different solvents (6 × 10−6 mol dm−3).
4350
4340
EtAc
THF
4330
4320
DMF
4310
CHCl3
4300
DMSO
4290
0.18
0.19
0.2
0.21
0.22
0.23
(n2-1/(2n2+1)
Figure 5. Plot of the Q band frequency of ZnPc (3) against (n2−1)/(2n2+1), where n is the refractive index
of the solvent.

10
H. R. P. KARAOĞLU ET AL.
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
300
400
500
600
700
800
Wavelength (nm)
Figure 6. electronic spectra of the zinc phthalocyanine derivatives (3, 6, and 7) in dmf. the concentration
in this study is 4.00 μmol dm−3.
be the influence of the atom in the axial position and the relevant higher oxidation state of
the metal ion in question.
Fluorescence and fluorescence quenching measurements were performed as described
[23]. Fluorescence studies of the zinc phthalocyanines have been recorded in DMF. The
absorption spectra, fluorescent emission, and subsequent excitation spectra of zinc phtha-
locyanines (3, 6 and 7) are presented in Figure 7. We detected fluorescence emission peaks
at 713, 700 and 702 nm (Table 1). The Stokes’ shifts of the ZnPc derivatives were between
5.00 × 105 and 5.26 × 105 cm−1. The fluorescence quantum yields (ΦF) were calculated by
comparison with unsubstituted ZnPc (Table 2).
The fluorescence quantum yield (ФF) of a compound is a measure of the molecular effi-
ciency of the fluorescent process. The comparative method is the most reliable approach
for calculation of ΦF. The method known as ΦF uses a well-characterized sample as a standard.
Essentially, when the excitation wavelength of the solutions of the standard and samples
are at the same excitation wavelength, it may be speculated that they absorb the same
amount of photons. The ratio of two quantum yields is what one gets for a simple ratio of
fluorescent intensities of two compared solutions.
Table 1 lists the data of the fluorescence quantum yield, fluorescence lifetimes, and natural
radiative lifetimes. The ΦF values of the zinc phthalocyanines synthesized in this study were
lower than that of unsubstituted zinc phthalocyanine in DMF.
Substituent groups may affect the fluorescence properties of phthalocyanines. Structural
rigidity plays a role in the fluorescence intensity of a chromophore with a more rigid structure
resulting in enhanced fluorescence [32]. Electron-accepting functional groups (such as car-
boxyl and nitro) result in quenching of the fluorescence [33]. The fluorescence quantum
yield of 6-thiohexanoic acid-substituted zinc phthalocyanine is lower than unsubstituted
ZnPc in DMF [34]. The fluorescence quantum yields of the poly (aryl benzyl ether) dendrimer-
ic-zinc phthalocyanine are higher than unsubstituted ZnPc in DMF [35]. The bigger ΦF value
in the higher generation dendrimer indicates the dendrimer backbone becomes less rigid
as the molecule size grows larger. Salicylhydrazone-zinc complex and its Schiff base metal
complex have lower fluorescence quantum yields than standard ZnPc in DMSO because of
the bulky substituents which promote intersystem crossing [36].

JOURNAL OF COORDINATION CHEMISTRY
11
700
600
500
400
300
200
100
0
300
400
500
600
700
800
Wavelength (nm)
160
140
120
100
80
60
40
20
0
300
400
500
600
700
800
Wavelength (nm)
180
160
140
120
100
80
60
40
20
0
300
400
500
600
700
800
Wavelength (nm)
Figure 7. absorption (top), excitation (middle), and emission (bottom) spectra for 3, 6 and 7 in dmf;
excitation wavelength is 614 nm.
Fluorescence lifetime (τF) is the average time of the molecule at the excited state before
fluorescing. This value affects the quantum yield, and longer lifetime results in a higher quan-
tum yield of fluorescence. Factors, such as internal conversion and intersystem crossing,
reduce the fluorescence lifetime while the value of ΦF decreases. In the present examination,

12
H. R. P. KARAOĞLU ET AL.
160
140
120
100
80
60
40
20
0
650
700
750
800
800
800
850
Wavelength (nm)
60
50
40
30
20
10
0
650
700
750
850
Wavelength (nm)
80
70
60
50
40
30
20
10
0
650
700
750
850
Wavelength (nm)
Figure 8a. fluorescent emission spectral changes of 3, 6, and 7 (4.00 μmol dm−3) in which different
concentrations of benzoquinone in dmf was added as quencher. the concentration of benzoquinone is
0.000, 0.008, 0.016, 0.024, 0.032, and 0.040 mol dm−3.
fluorescent lifetimes (τF) were calculated by the equation of Strickler and Berg. [37]. Using
this equation, we obtained a good correlation between fluorescent lifetimes, both experi-
mentally and theoretically, of the unaggregated molecules, which was also the case for the
octa-(3-(diethylamino)phenoxy- and hexylsulfanyl-substituted Pc compounds in DMF. The

JOURNAL OF COORDINATION CHEMISTRY
13
140
120
100
80
60
40
20
0
650
700
750
800
850
Wavelength (nm)
70
60
50
40
30
20
10
0
650
700
750
800
850
Wavelength (nm)
80
70
60
50
40
30
20
10
0
650
700
750
800
850
Wavelength (nm)
Figure 8b. fluorescent emission spectral changes of 3, 6, and 7 (4.00 μmol dm−3) in which different
concentrations of hydroquinone in dmf was added as quencher. the concentration of hydroquinone is
0.000, 0.008, 0.016, 0.024, 0.032, and 0.040 mol dm−3.
fluorescence lifetimes (τF) and natural radiative lifetimes (τ0) of ZnPc were calculated by the
respective equation, and the corresponding values are displayed in Table 2. The lifetimes of
fluorescence (τF) values of the octakis(3-(diethylamino)phenoxy and hexylsulfanyl-substituted

14
H. R. P. KARAOĞLU ET AL.
2.5
2
1.5
1
y = 15.666x + 1
R² = 0.9879
0.5
0
0
0.02
0.04
0.06
0.08
0.1
[BQ]
1.6
1.4
1.2
1
y = 4.4249x + 1
R² = 0.9488
0.8
0.6
0.4
0.2
0
0
0.02
0.04
0.06
0.08
0.1
[BQ]
2
1.8
1.6
1.4
1.2
1
y = 8.8457x + 1
R² = 0.9882
0.8
0.6
0.4
0.2
0
0
0.02
0.04
0.06
0.08
0.1
[BQ]
Figure 9a. stern-Volmerplotsof3, 6, and7 quenchedbyBQ. [ZnPc] = 4.00 μmoldm−3 indmf. Concentration
of the quencher is 0.000, 0.008, 0.016, 0.024, 0.032, and 0.040 mol dm−3.
zinc phthalocyanine are lower than that of unsubstituted zinc phthalocyanine in DMF [38].
The kF value of the substituted zinc phthalocyanines was smaller than that of unsubstituted
ZnPc [23].

JOURNAL OF COORDINATION CHEMISTRY
15
1.4
1.2
1
y = 4.1635x + 1
R² = 0.9694
0.8
0.6
0.4
0.2
0
0
0
0
0.02
0.02
0.02
0.04
0.06
0.08
0.08
0.08
0.1
0.1
0.1
[HQ]
1.4
1.2
1
y = 3.5198x + 1
R² = 0.9915
0.8
0.6
0.4
0.2
0
0.04
0.06
[HQ]
1.4
1.2
1
0.8
0.6
0.4
0.2
0
y = 1.9254x + 1
R² = 0.9753
0.04
0.06
[HQ]
Figure 9b. stern-Volmerplotsof3, 6, and7 quenchedbyhQ. [ZnPc] = 4.00 μmoldm−3 indmf. Concentration
of the quencher is 0.000, 0.008, 0.016, 0.024, 0.032 and 0.040 mol dm−3.
3.3. Fluorescence quenching studies by BQ
Fluorescence quenching features were investigated by adding benzoquinone (BQ) or hydro-
quinone (HQ) to the ZnPc solutions. In the presence of quinone, an energy transfer occurred
between the excited Zn(II) phthalocyanine (fluorophore) and BQ/HQ (quencher). We

16
H. R. P. KARAOĞLU ET AL.
Table 1. substituted ZnPcs in this paper and unsubstituted ZnPc: absorption, excitation, and emission
spectral data (in dmf).
Stokes’shift ΔStokes
(×105 cm−1)
Compound
Q Band λmax (nm)
Log ε
Excitation λEx (nm)
Emission λEm (nm)
3
693
680
680
670
5.23
5.35
5.34
5.17
693
682
683
670
713
700
702
676
5.00
5.56
5.26
6
7
ZnPca
16.67
aref. [21].
Table 2. Photophysical and photochemical parameters, and fluorescence quenching of the zinc phtha-
locyanines in dmf as solvent.
c
kF (s−1)(×108)a
Ksv
kq/(×1010 s−1)c
Compound
ΦF
τF (ns)
τo (ns)
3
0.06
0.01
0.02
0.17
0.437
0.068
0.138
1.03
7.29
6.81
6.89
6.05
13.72
14.68
14.51
16.53
15.67
4.42
8.85
3.59
1.30
3.20
5.59
6
7
ZnPcb
57.60
akf is the rate constant for fluorescence. Values were calculated using kf=Φf/τf.
bref. [21].
ckf is the bimolecular quenching constants and Ksv is the stern-Volmer constant (for benzoquinone).
established a progressive decrease in the fluorescence intensity with increase in the con-
centration of the quencher. The fluorescent quenching of zinc phthalocyanines (3, 6 and 7),
obtained by adding known amounts of benzoquinone or hydroquinone in DMF, obeys the
kinetics mechanism outlined by Stern and Volmer [39]. The fluorescent spectrum of ZnPc
with different amounts of benzoquinone and hydroquinone as the quencher can be seen
in Figure 8(a) and 8(b). When we generated the Stern-Volmer plots for 3, 6, and 7, straight
lines were obtained; thus, the quenching mechanisms obeyed the diffusion-control hypoth-
esis [39]. The values of zinc phthalocyanines can be observed in the slopes, depicted in Figure
9(a) and 9(b). In addition, the calculated KSV values are presented in Table 2. The Ksv values
of the phthalocyanines in this study were lower than that for unsubstituted ZnPc
(Ksv = 57.60 M−1). Comparing fluorescence quenching values with BQ and HQ, the phthalo-
cyanines interact better with benzoquinone. The Ksv values of the zinc phthalocyanines were
reduced when using hydroquinone. The kq value (bimolecular quenching constants) of the
substituted zinc phthalocyanine was smaller than that of unsubstituted ZnPc [23].
4. Conclusion
We described the syntheses and characterizations of metallophthalocyanines (M=Co, Zn,
Cl-Ga, Cl-In) substituted with two different substituents on each aromatic group. The elec-
tronic absorption spectra of the zinc phthalocyanine in various solvents were investigated.
Aggregation behavior of the zinc phthalocyanine was also examined. According to Beer-
Lambert Law, no aggregation was observed in chloroform in the concentration range from
4 × 10−6 to 14 × 10−6 mol dm−3. The photophysical properties of three different ZnPcs were
studied in DMF, and the effect of the peripheral substituents on photophysical properties
was investigated. Fluorescence quantum yields of the derivatives were lower than those of
the standard. The decrease in the fluorescent quantum yields is related to the low degree

JOURNAL OF COORDINATION CHEMISTRY
17
of symmetry observed in these complexes. Furthermore, the fluorescence of the ZnPc com-
pounds was typically quenched by benzoquinone. The Stern-Volmer kinetics were followed
in the fluorescence quenching of zinc phthalocyanines by benzoquinone in DMF.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the Research Fund of the Istanbul Technical University; the TUBITAK [grant
number 109T163].
References
[1] C.C. Leznoff, A.B.P. Lever (Eds.). In Phthalocyanines: Properties and Applications, Vols. 1–4, VCH,
New York (1989).
[2] K. Kadish, K.M. Smith, R. Guilard. In The Porphyrin Handbook, Vols. 15–20, Academic Press, Boston,
MA (2003).
[3] F.H. Moser, L.R. Thomas. Phthalocyanine Compounds, Reinhold, New York, NY (1963).
[4] N.B. McKeown. Phthalocyanine Materials. Synthesis, Structure and Function., Cambridge University
Press, Cambridge (1998).
[5] A. Atsay, I. Nar, E. Hamuryudan, M.B. Koçak, A. Gül. Chem. Select, 2, 9233 (2017).
[6] O.L. Osifeko, T. Nyokong. J. Coord. Chem., 69, 1050 (2016).
[7] R. Matshitse, K.E. Sekhosana, O.J. Achadu, T. Nyokong. J. Coord. Chem., 70, 3308 (2017).
[8] D.M. Mafukidze, T. Nyokong. J. Coord. Chem., 70, 3598 (2017).
[9] E. Guzel, G.Y. Atmaca, A. Erdoğmuş, M.B. Kocak. J. Coord. Chem., 70, 2659 (2017).
[10] P. Sena, N. Dege, S.Z. Yildiz. J. Coord. Chem., 70, 2751 (2017).
[11] A. Atsay, A. Gül, M.B. Koçak. Dyes Pigm., 100, 177 (2014).
[12] Y. Mahmiani, A.M. Sevim, A. Gül. J. Photochem. Photobiol., A, 321, 24 (2016).
[13] N. Özgür, I. Nar, A. Gül, E. Hamuryudan. J. Organomet. Chem., 781, 53 (2015).
[14] H.Z. Uzunmehmetoğlu, H.Y. Yenilmez, K. Kaya, A. Koca, A. Altındal, Z.A. Bayır. Inorg. Chim. Acta,
459, 51 (2017).
[15] H. Koçan, K. Kaya, İ. Özçeşmeci, B.Ş. Sesalan, M. Göksel, M. Durmuş, A.K. Burat. J. Biol. Inorg. Chem.,
22, 1261 (2017).
[16] H.R.P. Karaoğlu, A. Koca, M.B. Koçak. Dyes Pigm., 92, 1005 (2012).
[17] H.A. Dinçer, A. Gül, M.B. Koçak. J. Porphyrins Phthalocyanines, 8, 1204 (2004).
[18] A.K. Burat, A. Koca, J.P. Lewtak, D.T. Gryko. Synth. Met., 161, 1537 (2011).
[19] A. Cidlina, Z. Pausimova, M. Miletin, P. Zimcik, V. Novakova. J. Porphyrins Phthalocyanines, 19,
1095 (2015).
[20] Ö. Kurt, A. Koca, A. Gül, M.B. Koçak. Synth. Met., 206, 72 (2015).
[21] H.R.P. Karaoğlu, A. Koca, M.B. Koçak. Synth. Met., 182, 1 (2013).
[22] D. Dei, G. Chiti, M.P. De Filippis, L. Fantetti, F. Giuliani, F. Grunting, M. Soncin, G. Jori, G. Roncucci.
J. Porphyrins Phthalocyanines, 10, 147 (2006).
[23] E.G. Duruk, H.Y. Yenilmez, A. Altındal, Z.A. Bayır. Dalton Trans., 44, 10060 (2015).
[24] Y. Zorlu, F. Dumoulin, M. Durmus, V. Ahsen. Tetrahedron, 66, 3248 (2010).
[25] H. Du, R.C.A. Fuh, J. Li, L.A. Corkan, J.S. Lindsey. J. Photochem. Photobiol., A, 68, 141 (1998).
[26] J. Rose. Advanced Physico-Chemical Experiments, Sir Isaac Pitman & Sons Ltd., London (1964).
[27] B. Ertem, A. Bilgin, Y. Gök, H. Kantekin. Dyes Pigm., 77, 573 (2008).
[28] J. Simon, P. Bossoul. In Phthalocyanines: Properties and Applications, C.C. Leznoff, A.B.P. Lever (Eds),
Vol. 2, p. 223, VCH, New York (1993).
[29] M. Özceşmeci, İ. Özceşmeci, E. Hamuryudan. Polyhedron, 29, 2710 (2010).

18
H. R. P. KARAOĞLU ET AL.
[30] N.S. Bayliss. J. Chem. Phys., 18, 292 (1950).
[31] W.F. Law, R.C.W. Liu, J.H. Jiang, D.K.P. Ng. Inorg. Chim. Acta, 256, 147 (1997).
[32] H.Y. Yenilmez, A.M. Sevim, Z.A. Bayır. Synth. Met., 176, 11 (2013).
[33] T. Nyokong. Coord. Chem. Rev., 251, 1707 (2007).
[34] O. Tayfuroglu, G.Y. Atmaca, A. Erdogmus. J. Coord. Chem., 70, 3095 (2017).
[35] S.-J. Pan, D.-D. Ma, J.-S. Liu, K.-Z. Chen, T.-T. Zhang, Y.-R. Peng. J. Coord. Chem., 69, 618 (2016).
[36] P. Sen, S.Z. Yıldız, G.Y. Atmaca, A. Erdogmus. J. Coord Chem., (2018). doi:10.1080/00958972.2018.
1455094.
[37] G. Gümrükçü, G.K. Karaoğlan, A. Erdoğmuş, A. Gül, U. Avcıata. Dyes Pigm., 95, 280 (2012).
[38] A. Ogunsipe, T. Nyokong. J. Photochem. Photobiol., A, 173, 211 (2005).
[39] D. EVREN, H.Y. Yenilmez, A.K. Burat. Turk. J. Chem., 38, 1174 (2014).