Photophysical, photochemical and DNA binding studies of prepared phthalocyanines

Article abstract of DOI:10.1016/j.poly.2019.114205

In this study, three phthalocyanine derivatives (M = Zn, Co, and metal-free) were synthesized using the corresponding ligand 4-(2-(4-(tert-butyl)phenoxy)ethoxy)phthalonitrile 2 in peripheral position, which was prepared from the reaction of 4-nitrophthalonitrile with 2-(4-(tert-butyl)phenoxy)ethan-1-ol 1. Metallophthalocyanine (MPc) and Metal-free phthalocyanine (H₂Pc) derivatives, which have soluble groups in peripheral positions were synthesized. They are have high soluble in organic solvents depending on the appropriate position such as (tetrahydrofuran (THF), chloroform (CHCl₃), methylene chloride (DCM), acetone (ACE), Dimethyl formamide (DMF), and dimethylsulphoxide (DMSO))….etc. The structures of Metallophthalocyanine (MPc) and Metal-free phthalocyanine (H₂Pc) compounds 3a, 3b, and 3c were characterized using UV–vis spectroscopy, infrared (FT-IR) spectroscopy, and MALDI-TOF MS. Additionally, DNA binding, metal chelating effect assay, and DPPH [2,2-diphenyl-1-picrylhydrazyl hydrate] radical scavenging assay of MPcs H₂Pc were investigated. In the interaction between Pc and CT-DNA the intrinsic binding constant (Kb) calculation was gave. Although the phthalocyanine compounds (3a, 3b and 3c) shoved low iron-containing iron chelating properties compared to EDTA, they can be said to have high metal chelating properties at the specified concentrations for this phthalocyanines. The DPPH radical scavenging activity of Pcs was elucidated according to the estimation of their in vitro antioxidant activities.

Full text of DOI:10.1016/j.poly.2019.114205

Journal Pre-proofs
Photophysical, photochemical and DNA binding studies of prepared phthalo-
cyanines
Arif Baran, Sumeyye Çol, Emel Karakılı ç, Furkan Özen
PII:
S0277-5387(19)30650-3
DOI:
https://doi.org/10.1016/j.poly.2019.114205
POLY 114205
Reference:
Polyhedron
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Accepted Date:
15 September 2019
19 October 2019
23 October 2019
Please cite this article as: A. Baran, S. Çol, E. Karakılı ç, F. Özen, Photophysical, photochemical and DNA binding
studies of prepared phthalocyanines, Polyhedron (2019), doi: https://doi.org/10.1016/j.poly.2019.114205
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MANUSCRIPT
Photophysical, photochemical and DNA binding studies of prepared
phthalocyanines
Arif Baran*, Sumeyye Çol, Emel Karakılıç, Furkan Özen
Sakarya University, Faculty of Arts and Sciences, Chemistry Department, 54187, Sakarya,
Turkey
abaran@sakarya.edu.tr
ABSTRACT
In this study, three phthalocyanine derivatives (M= Zn, Co, and metal-free) were synthesized
using the corresponding ligand 4-(2-(4-(tert-butyl)phenoxy)ethoxy)phthalonitrile 2 in
peripheral position, which was prepared from the reaction of 4-nitrophthalonitrile with 2-(4-
(tert-butyl)phenoxy)ethan-1-ol 1. Metallophthalocyanine (MPc) and Metal-free phthalocyanine
(H2Pc) derivatives, which have soluble groups in peripheral positions were synthesized. They
are have high soluble in organic solvents depending on the appropriate position such as
(tetrahydrofuran (THF), chloroform (CHCl3), methylene chloride (DCM), acetone (ACE),
Dimethyl formamide (DMF), and dimethylsulphoxide (DMSO))….etc. The structures of
Metallophthalocyanine (MPc) and Metal-free phthalocyanine (H2Pc) compounds 3a, 3b, and
3c were characterized using UV–vis spectroscopy, infrared (FT-IR) spectroscopy, and MALDI-
TOF MS. Additionally, DNA binding, metal chelating effect assay, and DPPH [2,2-diphenyl-
1-picrylhydrazyl hydrate] radical scavenging assay of MPcs H2Pc were investigated. In the
interaction between Pc and CT-DNA the intrinsic binding constant (Kb) calculation was gave.
Although the phthalocyanine compounds (3a, 3b and 3c) shoved low iron-containing iron
chelating properties compared to EDTA, they can be said to have high metal chelating
properties at the specified concentrations for this phthalocyanines. The DPPH radical
scavenging activity of Pcs was elucidated according to the estimation of their in vitro
antioxidant activities.
Keywords: Photodegradation, Singlet oxygen, Binding properties, Photophysical and
Photochemical investigation

1. Introduction
Phthalocyanines (Pcs) and their derivatives are important molecules and thus extensive studies
on Pcs have been going on for many years. Hitherto Pcs and their derivatives have had many
potential applications in material science, including chemical sensors, liquid crystals,
Langmuir–Blodgett films [1-3] and sensitizers for photodynamic therapy of cancer [4,5].
Moreover, they are also known for their good conductive properties such as in optical
components for nonlinear optics [6,7]. The unknown additional properties of these molecules
will be discovered in time. As the properties of such molecules are being discovered, world-
class chemists are taking interest in the more fascinating features of Pcs [8,9].
Because of intermolecular interactions between peripherally unsubstituted Pcs they have a
solubility problem in organic solvents [10]. If the solubility of the synthesized Pc is low in
organic solvents, in this case it undergoes aggregation and this solubility problem limits its use
[11] To overcome this problem of solubility and aggregation, the substituent must be chosen
meticulously. Introduction of tri- or tetra-substituent groups into the periphery of the Pc
framework can minimize the solubility problem by increasing the distance between atoms in
the porphyrin skeleton. In connection with the formation of constitutional isomers and high
dipole moment that results from the unsymmetrical arrangement of the substituents at the
periphery, tetra-substituted Pcs exhibit better solubility and lower aggregation than the
corresponding octa-substituted Pcs [12,13]. If there are substituents that are electron releasing
in the peripheral or non-peripheral position of the Pc ring, it provides a bathochromic shift in
the Q band. That is to say, a complex substituent in a peripheral position has a greater tendency
to minimize aggregation than a complex substituent in a non-peripheral position [14].
In the present study, 2-(4-(tert-butyl) phenoxy) ethan-1-ol 1, prepared first from the reaction of
4-(tert-butyl) phenol and ethylene carbonate, was reacted with 4-nitrophthalonitrile, which
resulted in 4-(2-(4-(tert-butyl)phenoxy)ethoxy)phthalonitrile 2 as a good electron-donating
system for the metallophthalocyanine (MPc) and metal-free phthalocyanine (H2Pc). The
reaction of 4-(2-(4-(tert butyl)phenoxy)ethoxy)phthalonitrile 2 with Zn(OAc)2.2H2O and
Co(OAc)2.4H2O, complex salts in DMF, using DBU catalytically at reflux temperature gave
metallophthalocyanines (MPcs). Using the same condition (without using complex salts) gave
the metal-free phthalocyanine (H2Pc). Then these complexes were investigated in terms of
DNA binding, metal chelating effect, and DPPH radical scavenging.

2. Material and methods
2.1. General procedures-materials and methods
The chemicals and solvents using in this study, (4-(tert-butyl)phenol, 1,3-dioxolan-2-one, 4-
nitrophthalonitrile, K2CO3, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), Zn(OAc)2.2H2O, and
Co(OAc)2.4H2O), were purchased from Merck, Sigma Aldrich, Acros,…. The solutions used
in the experiment (DMF, THF, DCM, DMSO, and ethanol) were dried and purified. For
recording the NMR spectra 300 MHz (1H NMR) and 75 MHz (13C NMR) spectrometers were
used. The chemical shifts were given in ppm (δ) relative to internal tetramethylsilane (TMS, δ
0.0 ppm) or with the solvent reference relative to TMS employed as the internal standard
(CDCl3, δ 7.26 ppm and CD3OD, δ 3.35, 4.78 ppm or (CD3)2SO). An Ati Unicam Mattson 1000
Series FT-IR (ATR system) spectrometer was used for recording the IR spectra. The MALDI-
TOF spectra were recorded with Bruker Daltonics flex Analysis. Photo-irradiation was
conducted using a General Electric quartz line lamp (300 W). A Shimadzu UV 2600 model
spectrophotometer was used for recording the UV–vis spectra. Fluorescence measurements and
DNA-binding experiments were conducted with the Agilent Technologies Cary Eclipse
spectrophotometer.
2.2. Synthesis
2.2.1. Synthesis of 2-(4-(tert-butyl)phenoxy)ethan-1-ol (1): 2-(4-(tert-butyl)phenoxy)ethan-1-
ol (1) was prepared according to the method reported in the literature,[15] with some
modifications. To 4-(tert-butyl)phenol (1.0 g, 6.66 mmol) in DMF was added the substituted
1,3-dioxolan-2-one (1.17 g, 13.31 mmol). After the mixture was stirred for 15 min, K2CO3 (1.84
g, 13.31 mmol) was added. Then the stirring solution was refluxed for 24 h. The completion of
the reaction was checked by TLC, the mixture was added dropwise, and then ice water (250
mL) was added, followed by shaking. The inorganic layer was eluted off. The organic phase
was washed with plenty of water, dried on Na2SO4, and evaporated to give light brown liquid
(1.04 g, 80% yield). MW: 194.27. FT-IR max/cm−1: 3367 cm−1 (OH), 3040 cm−1 (Ar–H); 2959,
1
2904 cm−1 (aliphatic C-H); 1609, 1580, 1512 cm−1 (Ar–C=C); 1040 cm−1 (C-O-C). H-NMR
(300 MHz, CD3OD): 7.33 (2H, d, H4), 6.88 (2H, d, H5), 4.08 (2H, t, H7), 3.95 (2H, t, H8), 2.33

(H, s, OH), and 1.31 (9H, s, H1). 13C-NMR (75 MHz, CD3OD): 156.56 C6, 144.07 C3, 126.56
C4, 114.25 C5, 69.39 C7, 61.75 C8, 34.34 C2, and 31.76 C1.
2.2.2. Synthesis of 4-(2-(4-(tert-butyl)phenoxy)ethoxy)phthalonitrile (2): To a mixture of 4-
nitrophthalonitrile (0.7 g, 3.60 mmol) in 15 mL of dry DMF was added 2-(4-(tert-
butyl)phenoxy)ethan-1-ol (0.62 g, 3.60 mmol) (1) and the resulting mixture was stirred at 50
°C under N2. Then to the stirred solution was added anhydrous K2CO3 (0.5 g, 3.60 mmol) over
1 h. After stirring for a further 12 h, TLC was used to check that the reaction was completed.
The insoluble residue was removed by filtration. The solution was added dropwise and then ice
water (250 mL) was added, followed by shaking. Then the solution was washed with plenty of
water, dried on Na2SO4, evaporated, and dried to give residue. The residue was subjected to
column chromatography with silica gel, using different ratios of DCM/EtOAc to give a brown
solid after evaporation of the collected filtrates (Yield: 0.85 g, 73%). Mp: 107-109 °C. FT-IR
max/cm−1: 3093 cm−1 (Ar–H); 2961, 2873 cm−1 (aliphatic C-H); 2232 cm−1 (C≡N); 1598, 1564,
1
1509 cm−1 (C=C) and 1099 cm−1 (C-O-C). H-NMR (300 MHz, CDCl3): δ ppm 7.73 (d, 1H,
H13), 7.34-7.23 (m, 4H, H4, 10, 14), 6.87 (d, 2H, H5), 4.42 (t, 2H, H8), 4.35 (t, 2H, H7), and
1.29 (s, 9H, H1). 13C-NMR (75 MHz, CDCl3): 162.05 C9, 156.07 C6, 144.56 C3, 135.48 C13,
126.68 C4, 120.02 C14, 119.84 C10, 117.65 C11, 115.92 C15, 115.50 C16, 114.25 C5, 107.82
C12, 67.98 C8, 66.17 C7, 34.38 C2, and 31.74 C1.
2.2.3. Synthesis of zinc (II) phthalocyanine (3a): To compound 2 (0.2 g, 0.62 mmol) was
added Zn(OAc)2.2.H2O (0.095 g, 0.44 mmol) and a catalytic amount of 1.8-
diazabicyclo[5.4.0]undec-7-ene (DBU) at rt. The stirred solution was heated to 130 °C using
DMF as reaction solution under N2. The reaction was stirred at this temperature for 24 h until
the color turned dark green. After completion of the reaction, the temperature was lowered to
room temperature. The insoluble salt was removed by filtration and the dark green product was
poured into ice water (100 mL), stirred, and filtrated. The filtrate was then washed with hot
water and dried in an open oven. Finally the filtrate was eluted on silica gel with ether and
hexane/EtOAc 4:1 respectively for separation from the starting materials or unreacted materials.
Then the undesired fractions were separated and filtered with tetrahydrofuran. The filtrate was
evaporated using an evaporator to give a pure and readily soluble product in DCM, CDCl3,
THF, DMF, and DMSO. MW: 1346.95. Yield: 0.15 g (42%). Mp>350 °C. FT-IR νmax (cm−1):
3041 cm−1 (Ar–H); 2952, 2904 cm−1 (aliphatic C–H); 1606, 1583, 1511 cm−1 (C=N, C=C); 1041
cm−1 (C-O-C). UV–vis (DMF), λmax, nm: 680, 612.5, 357.6. MALDI-TOF MS: m/z [M]+ calcd.

for C80H80N8O8Zn: 1346.95; found [M] 1346.93. Elemental analysis for [C80H80N8O8Zn]: C,
71.34; H, 5.99; N, 8.32. Found: C, 71.38; H, 5.96; N, 8.37%.
2.2.4. Synthesis of cobalt (II) phthalocyanine (3b): To compound 2 (0.2 g, 0.62 mmol) was
added a mixture of Co(OAc)2.4H2O (0.077 g, 0.44 mmol) and a catalytic amount of DBU,
followed by stirring at 130 °C in dry DMF under N2 for 24 h. At the end of this time, after the
color of the reaction had turned green, the reflux temperature was reduced to room temperature.
The insoluble residue was disposed of by filtration and the dark green solution in DMF was
poured into ice-water (100 mL) and stirred. The precipitation phase was filtered and washed
with hot water and warm ethanol. The dark blue residue was dried in an open oven and was
separated from the starting materials or unreacted materials after purification on silica gel by
column chromatography using a solution such as ether, hexane/ethylacetate, and
tetrahydrofuran (THF). After the same fraction was collected and evaporated under reduced
pressure, an easily soluble product was obtained in DCM, CDCl3, THF, DMF, and DMSO.
Yield: 0.18 g (50%). Mp>350 °C. MW: 1340.50. FT-IR νmax (cm−1): 3040 cm−1 (Ar-H); 2954,
2868 cm−1 (aliphatic C–H); 1608, 1512, 1479 cm−1 (C=N, C=C); 1094, 1066 cm−1 (C-O-C).
UV–vis (DMF), λmax, nm: 670.0, 609.5, 325.0. MALDI-TOF MS: m/z [M]+ calcd. for
C80H80N8O8Co: 1340.50; found [M] 1340.80. Elemental analysis for [C80H80N8O8Co]: C,
71.68; H, 6.02; N, 8.36. Found: C, 71.70; H, 6.05; N, 8.37%.
2.2.5. Synthesis of metal-free phthalocyanine (3c): To a mixture of 2 (0.2 g, 0.62 mmol) in
absolute DMF was added a catalytic amount of DBU and the mixture was stirred at 130 °C in
dry DMF for 24 h under N2. After the change of the color to dark blue was complete the reaction
mixture was cooled to room temperature. The insoluble salt was removed by filtration and the
dark green product was poured into ice-water (100 mL) and stirred. After precipitation of the
filtrates, the mixture was washed with water and warm ethanol, and the unreacted organic
materials were removed. The dark blue product was dried in an open oven and chromatographed
with ether, hexane/ethylacetate, and tetrahyrofuran to remove the starting materials or unreacted
material. After collection and evaporation of the solution by evaporator gave pure 3c; it is
readily soluble in DCM, CDCl3, THF, DMF, and DMSO. Yield: 0.15 g (48%). Mp>350 °C.
MW: 1283.58. FT-IR νmax (cm−1): 3283 cm−1 (Ar-H); 2923, 2853 cm−1 (aliphatic C–H); 1735,
1607, 1479 cm−1 (C=N, C=C); 1238, 1097 cm−1, (C-O-C). UV–vis (DMF), λmax, nm: 703, 672,
644, 610, 397, 343. MALDI-TOF MS: m/z [M]+ calcd. for C80H82N8O8: 1283.58.; found [M]

1283.67. Elemental analysis for [C80H82N8O8]: C, 74.86; H, 6.44; N, 8.73. Found: C, 74.82; H,
6.47; N, 8.76%.
2.3. DNA Binding Study
2.3.1. DNA Binding assay:
The DNA solution was prepared as follows: 10 mg of CT-DNA was dissolved in 1.5 mL of 5
μM Tris-HCl/50 μM NaCl buffer. The UV absorption ratio of the CT-DNA solution is 1.85 at
260 and 280 nm, indicating that the DNA is sufficiently free from protein and single-stranded
DNA. Using absorption spectroscopy the concentration of CT-DNA per nucleotide phosphate
was calculated by its molar absorption coefficient value of 6600 M−1 cm−1 at 260 nm. The Pcs’
(concentration was kept constant, 7.5 µM) electronic absorption spectrum was assessed before
and after the addition of gradually increasing concentrations of DNA. The electronic absorption
spectrum of Pcs was obtained in 1-cm quartz cuvettes, after 10 min incubation in 5 μM Tris-
HCl/50 μM NaCl buffer, 5% DMSO (pH
=
7.2) at 400-750 nm.
The absorbance of DNA was eliminated by applying a reference cuvette containing an equal
amount of DNA. In the interaction between Pc and CT-DNA the intrinsic binding constant (Kb)
calculation was given as follows (Equal 1):
[DNA] / (εa-εf) = [DNA] / (εb-εf) + 1 / Kb (εa-εf)
(Eq.1)
Here εa = Absorption/[phthalocyanine] (the apparent), εa = extinction coefficient for the free
phthalocyanine, εb = extinction coefficient for phthalocyanine in bound form. The [DNA] / (εb
εf) is versus [DNA], Kb is given by the ratio of slope to the y intercept [16].
2.3.2. Metal Chelating Effects Assay
The metal chelating activities of Pcs were investigated by the iron ion-ferrozine method,
compared to EDTA, which was used as reference compound [17]. To a solution of 50 μL of 2
mM FeCl2 and 100 μL of 5 mM ferrozine was added 500 μL of varying concentrations (25–100
μM) of Pc. The optical density of samples at rt was recorded after 10 min incubation at 562 nm,
The control assay of the mixture was also conducted without using Pc. All experiments were in

triplicate and the results recorded as the mean ± standard deviation (S.D.). The metal chelating
effect was calculated as follows (Equal 2) [18].
Metal chelating effect (%): [[Acontrol - Asample]/Acontrol] x 100
(Eq. 2)
2.3.3. DPPH Radical Scavenging Assay
The DPPH radical scavenging activity of Pcs was elucidated according to the estimation of their
in vitro antioxidant activities [19]. To the mixture of 0.5 mL of Pcs prepared at varying
concentrations in DMSO was added a mixture of freshly prepared 1 mL of 0.1 mM DPPH in
methanol. The incubation assay of the mixtures in the dark for 50 min at rt was performed and
after this incubation time the optical density of the assay mixtures was recorded at 517 nm. In
the same condition the control mixture (without Pcs) and gallic acid standard mixture were
examined. All experiments were in triplicate and the results recorded as the mean ± S.D. The
free radical scavenging effect of Pcs was calculated according to the above method (Equal 2).
3. Result and discussion
3.1. Synthesis and characterization
In the synthetic pathway, a well-established method for the synthesis of easily soluble
tetrasubstituted MPcs and H2Pc was implemented, which involved an aromatic nucleophilic
substitution
reaction
occurring
between
4-nitrophthalonitrile
and
2-(4-(tert-
butyl)phenoxy)ethan-1-ol 1, followed by cyclic tetramerization using Zn(OAc)2.2H2O and
Co(OAc)2.4H2O metal salt for MPcs and without using a metal salt for H2Pc. The metallation
reaction after reflux in DMF and using DBU (catalytically) afforded 42% yield for ZnPc and
afforded 50% yield for CoPc. The same method without using metal salt afforded 48% yield of
metal-free Pc. At the start of the reaction, different solvents (pentane-1-ol, DMSO, and DMF)
with high boiling points were used for MPcs and H2Pc. The efficiency of the reaction was higher
in DMF. The MPcs and H2Pc reactions were therefore carried out in DMF. For the purity of the
product, different solution ratios were used but the only convenient solution was chosen as THF
and acetone in 4:1 ratio and the purification was realized by column chromatography on silica
gel.

Ha
Hb
Hb
Ha
CN
Ha'
Ha'
Hb'
Hb'
2
C1
3
3
2
C2
4
1
4
1
O
O
CN
O
OH
3'
2'
2'
C3
C4
1
3'
2
Figure 1. 2-(4-(tert-butyl)phenoxy)ethan-1-ol (1) and 4-(2-(4-(tert-butyl)phenoxy)ethoxy) phthalonitrile (2)
The characterization of the Pcs was performed by NMR, IR, UV-vis, and MALDI-TOF MS.
The results of the analysis were compatible with the estimated structures. The proton NMR in
CDCl3 showed that the synthesized compounds were pure and that all protons occurred in their
pending regions in the ring. In compound 1, while aromatic protons (H-3 and H-3') resonated
between 7.37 and 7.30 ppm (A part of an AA'BB' system), other aromatic protons (H2 and H2')
resonated between 6.89 and 6.84 ppm (B part of an AA'BB' system. On the other hand, while
methylenic protons (Ha and Ha’) resonated at 4.07 ppm as multiplets, the other methylenic
protons (Hb, Hb’) resonated at 3.95 ppm, also as multiplets. The hydroxyl and methyl groups
resonated as broad singlets at 2.19 ppm (for –OH group) and as singlets at 1.30 ppm (for methyl
groups), respectively. The nine 13C-NMR resonance signals are compatible with the prescribed
structure in Scheme 1. In the configuration elucidation of compound 2, the nitrile bound ring
proton (Hc4) resonated as a multiplet giving the A part of an AA’BB’ system at 7.70 ppm and
the neighboring proton Hc3 resonated as a multiplet giving the B part of an AA’BB’ system at
7.32 ppm. Another aromatic ring proton (Hc1) resonated as a multiplet at 7.31 ppm. For
elucidation of the other part of a molecule, the H3 and H3’ protons resonated as multiplets
giving the A part of an AA’BB’ system at 7.29 ppm, and the other protons (H2 and H2’)
resonated as multiplets giving the B part of an AA’BB’ system at 6.86 ppm. Ethylenic protons
Ha and Ha’ or Hb and Hb’ resonated as multiplets giving the A part of an AB system at 4.41
ppm and the other protons (Hb and Hb’ or Ha and Ha’) resonated as multiplets giving the B
part of an AB system at 4.34 ppm. Methyl group protons resonated in their respective regions
giving singlets at 1.29 ppm. In comparison with their theoretical result, the seventeen 13C
1
13
signals are consistent with the structure. In the course of the study, H- and C-NMR of the
synthesized metallophthalocyanine (3a, 3b) and metal-free Pc (3c) compounds could not be
obtained even though different deuterium solvents were used (Scheme 1). NMR measurements
of the CoPc (3b) was precluded owing to its paramagnetic nature, and the ZnPc (3a) and H2Pc
(3c) were not measured despite good solubility. However, all the mass spectra for
phthalocyanines (3a, 3b, 3c) confirmed the proposed cyclotetramerization.

The IR spectra for compound 1 showed that while the hydroxyl group vibration appeared at
3450-3250 cm–1, the aliphatic CH stretching vibration appeared at 2959-2869 cm–1. However,
the most convincing characteristic group is the etheric (C–O–C) bond vibration at ca. 1243–
1245 cm–1 for 1. In the IR spectra of compound 2, the aliphatic CH stretching was shown at ca.
3074–2961 cm–1, which resembles the aliphatic CH stretching of compound 1. In addition, the
most convincing feature is the presence of 2232 cm–1 vibrations in the cyano-functional group
and the disappearance of the hydroxyl group. For the phthalocyanines (ZnPc, CoPc and H2Pc)
most convincing things is that the cyclotetramerization of the phthalonitrile derivatives with the
disappearance of the CN three band at approximately 2232 cm-1. Already three phthalocyanines
(ZnPc, CoPc and H2Pc) IR-spectra are close to each other.
In the MPc compounds (3a–3b) the UV–vis spectra are characteristic for the Q-band region, in
this region at around 655-700 nm for MPc (3a) and 640-680 nm for MPc (3b) in DMF. The
Soret band or B band is characteristic in the UV-vis spectra in the region at around 320-374 nm
for MPc (3a) and at around <400 nm for MPc (3b). In the case of metal-free Pc Q1 and Q2 are
characteristic at around 645-665 nm and 694-720 nm, while the B band is seen at around 320-
380 nm. This is due to the π-π* transition of the Q band resulting from the HOMO (highest
occupied molecular orbital) and the deepest π-π* transition of the B band originating from the
LUMO (lowest unoccupied molecular orbital).
CN
CN
O
O
O2N
O
O
OH
OH
4- (tert-butyl) phenol
i
ii
1
(80%)
CN
O
O
OH
CN
O
2
(73%)
1

N
N
CN
CN
N
N
N
M
iii
N
N
N
2
3a M
( = Zn, 42%),
3b M
( = Co, 50%),
3c M= 2H,
( 48%)
Scheme 1. (i) K2CO3, DMF, reflux, 24 h; (ii) K2CO3, DMF, 50 °C; 12 h (iii) 3a Zn(OAc)2.2H2O, DBU, DMF, 130
°C, 24 h; 3b Co(OAc)2.4H2O, DBU, DMF, 130 °C, 24 h; 3c DBU, DMF, 130 °C, 24 h.
In the UV-vis spectra of the Pcs, the concentration and density of a solvent are interconnected;
depending on the increase in concentration for the Q-band absorption, the density will also
increase. Moreover, the Q band depends on the environmental conditions and substitution of
the Pc macro-ring. Q-band absorption occurs with the transition of the HOMO to the LUMO π
→ π* [20]. The UV-vis spectra of the ZnPc, CoPc, and H2Pc in the experiment are shown in
text.
3.2. Aggregation behavior
The electronic spectra of 3a and 3c show absorption, emission, and excitation in DMF (Figure
2, Figure 3). The excitation spectra for complex 3a are different from the absorption and
emission spectra in the mentioned solution because of a blue shift giving slight aggregation and
a low split at 600-620 nm. However, there is little aggregation in the excitation band relative to
the absorption band. According to the excitation spectra, the representation of the unaggregated
strong absorption band of 3a with the low splitting in the Q band is clearer in the fluorescence
excitation spectra in DMF (Figure 2). The fluorescence emission Q-band of 3a is different from
the fluorescence absorption and excitation Q-bands (Figure 2), which have red shifted and
included aggregation [21,22a]. Pc-3c, which does not contain metal, could not detect much
different special properties than ZnPc-3a containing metal at its center. The absorption,
emission, and excitation spectra for 3a and 3c in DMF were compared with those in standard
ZnPc, and the results are given in Table 1.

700
600
500
400
300
200
100
0
1.6
1.4
1.2
1
Excitation
Emission
Absorption
0.8
0.6
0.4
0.2
0
500
600
700
Wavelength (nm)
800
Figure 2. Absorption, excitation, and emission spectra of compound 3a in DMF. Excitation wavelength 682 nm.
800
700
600
500
400
300
200
100
0
1.2
1
Excitation
Emission
Absorption
0.8
0.6
0.4
0.2
0
300
400
500
600
700
800
Wavelength (nm)
Figure 3. Absorption, excitation, and emission spectra of compound 3c in DMF. Excitation wavelength 672, 718
nm.
Table 1. Absorption, excitation, and emission spectral data for 3a, 3c and standard studied ZnPc.
Compound
Solvent
Q band λmax
(nm)
log ε
Excitation
λEx, (nm)
682
Emission
λEm, (nm)
693
Stokes shift
(nm)
13
3a
3c
DMF
DMF
DMF
680
5.15
4.72, 4.68
5.37
699, 705
670
672, 718
670
720
15
ZnPca
676
6
a Data from Ref. [22b].

For the ZnPc-3a in Figure 4, while the B bond region appears between 325 and 375 nm, the Q
bond region appears between 660 and 700 nm as a single (narrow) band in different solutions
such as DMF, DMSO, and DCM with the same concentration, showing no aggregation except
for low splitting at 600-630 nm. This unaggregation is also due to the fact that the tert-butyl
substituents in the peripheral position donating electrons to the Pc macro-ring can have high
dipole moment [12,13,21].
Figure 4. UV-vis of 3a (1.0×10–5 M) in different solutions.
In the CoPc-3b, electron-donating tert-butyl groups in a peripheral position donate electron
density into the π system and increasing conjugation in the macro-ring, thus causing red shifting
and a lower HOMO–LUMO gap [20,21]. In the absorbance-wavelength graph both the B band
and Q band cause red shifting in the mentioned solution, showing low aggregation and low
splitting at 590-620 nm. (Figure 5.)

Figure 5. UV-vis of 3b (1.0×10–5 M) in different solutions.
The metal-free Pc LUMO trajectory forms Qx and Qy states with a lower D2h symmetry than
planar metallophthalocyanines’ D4h symmetry and the Q-band is split into two [23] The B- band
and Q-band electronic absorption, which are characteristic for H2Pc-3c, were recorded at a
concentration of 1.0×10–5 M in the 300-750 nm range. The B band showed strong absorption
between 310 and 400 nm, while the Q band showed strong absorption with low aggregation
between 610 and 720 nm. Moreover, the small splits seen between 600 and 630 nm belong to
the vibration tones of the Q band. (Figure 6.)
Figure 6. UV-vis of 3c (1.0×10–5 M) in different solutions.
The concentration dependence of complex 3a in DMF is shown in Figure 7. The intensity of
the Q band increases with the increase in solution in different concentrations. In the absorption
spectral changes, aggregation also depends on the nature of the solvent, and because of

aggregation there are no new bands [24]. In Figure 7, it is seen that the Lambert–Beer law is
obeyed at different concentrations of solvent ranging from 2×10–6 to 1×10–5 M.
Figure 7. Absorption spectral changes of compound 3a in DMF at concentrations from 2×10–6 to 1×10–5 M.
3.3. Photophysical and photochemical parameters
3.3.1. Singlet oxygen quantum yields
The absorbance changes for the determination of singlet oxygen quantum yield were studied in
1.0×10–5 M concentration. The experiment was performed in DMF solution in air. After
compound 3a and DPBF were mixed, the results were recorded at regular intervals in a system
containing air under light irradiation in the dark. The intensity of the light used was
6.63×1015photons–1cm–2. To avoid the occurrence of side chain reactions the concentration of
DPBF was maintained at ~3 × 10–5 M. Electronic absorption spectral changes during the
investigation of the photodegradation quantum yield were exhibited for compound 3a and 3c
using DPBF as chemical quencher, compared to the known relative method ZnPc (Figure 8,
Table 2) [25-27].

Figure 8. Absorbance changes for the determination of singlet oxygen quantum yield of complex 3a (1.0×10–5
M) in DMF using DPBF as singlet oxygen quencher. (Inset: plot of DPBF absorbance versus time).
Table 2. Photochemical parameters of 3a and 3c in DMF.
Compound
ΦΔ
Φd (x10-4)
0.45
3a
0.04
0.03
0.56
3c
0.57
ZnPca
0.23
aData from Ref.[27]
Equation 3 was used with absorbance changes for the determination of singlet oxygen quantum
yield for complex 3a, and 3c.
Std
R .
I
abs
Φ∆ = ΦS∆td
,
(퐸푞. 3)
RStd.Iabs
휱푺∆풕풅 in Equal (3)
defines the singlet oxygen quantum yield (Φ ) in relation to the standard
Δ
Zn-Pc method ( 푺풕풅=0.56 in DMF). R and RStd exhibit DPBF photo-quencher properties in the
휱∆
푺풕풅
presence of related samples (3a and 3c). Iabs and
are the rates of light absorption by the
푰풂풃풔
samples (ZnPc-3a and metal free-3c) and the standard, respectively.
3.3.2. Photodegradation studies
Photodegradation, in general, is expressed as the resistance of a molecule to light.
Photodegradation quantum yield (Φd) can be calculated by examining the change in the

absorption spectrum during light degradation of the compound. The photodegradation of Pcs
are observed with a decrease in Q bands during photolysis of the Q-band region at certain time
intervals and the photodegradation quantum yield (Φd) can be calculated using the slopes of the
calibration graphs created at these certain time intervals. After laser radiation, or photolysis, Q
bands was decreased over time for compound 3a. This decrease in Q absorption band was
measured between 615-680 nm (Figure 9). Also the same decrease was observed in Q bands
absorption between 699-705 nm for compound 3c. All results are exhibited in Table 2. A light
intensity of 3.26×1016 photons s–1 cm–2 was employed for Φd determinations.
.
Figure 9. Electronic absorption spectral changes during the investigation of the photodegradation quantum yield
of compound 3a (1.0×10–5 M). (Inset: plot of absorbance versus time).
Absorption spectral changes during the investigation of photodegradation quantum yield (Φd)
for compound 3a and 3c were calculated by Equal 4 [28,29].
(
)
C0 ― Ct . V. NA
Φd =
,
(퐸푞. 4)
Iabs . S. t
Here C0 is the concentration before irradiation, Ct is the concentration after irradiation, V is
volume, NA is the Avogadro constant, S is irradiated cell area, t is irradiation time, and Iabs is
the overlap integral of the radiation source light intensity [30].

3.3.3. Fluorescence quenching studies of 1,4-benzoquinone (BQ)
The fluorescence quenching assays for the complex 3a and 3c were performed by adding
benzoquinone (BQ) at different concentrations of saturated solutions of MPc, obeyed the Stern–
Volmer equation and kinetics for calculation the change in fluorescence intensity [31].
Fluorescence emission reduction of compound 3a by adding BQ at different concentrations (0,
0.008, 0.016, 0.024, 0.032, and 0.040 mol dm–3) in DMF is shown in Figure 10. Because of the
high electron affinity of quinones and their good participation in electron transfer processes,
the lowest excited state energy for them is greater than the excited single state energy of MPc
complexes [32-34]. Therefore, it is unlikely that energy transfer from exciting MPc to BQ will
occur and MPc are known to be readily reduced. Accordingly, fluorescence MPc quenched by
BQ occurs through electron transfer of excited state from MPc to BQ [35]. The Stern-Volmer
constant value (Figure 10) were calculated in DMF (Ksv = 60.1 M-1 for 3a, Ksv = 13.4 M-1 for
3c ), on the slope plot graph against BQ concentration [32]. According to Stern-Volmer
constant, the Ksv value of ZnPc complex 3a was higher than the standard Sdt-ZnPc, whereas
the Ksv value of H2Pc complex 3c was showed lower than the Sdt-ZnPc (Std-ZnPc Ksv =
57.60 M-1 in DMF).
3.5
3a
3c
3
2.5
2
Linear (3a)
Linear (3c)
1.5
1
0
0.01
0.02
0.03
0.04
[BQ]
.
Figure 10. (Left) Fluorescence emission spectral changes of 3a (1.0 × 10–5 M) on addition of different
concentrations of BQ in DMF. (Right) Stern-Volmer plot for BQ quenching of substituted phthalocyanines ( ZnPc
3a and H2Pc 3c) in DMF. [BQ] = 0, 0.008, 0.016, 0.024, 0.032, 0.040 M.
I0/I = 1 + KSV[BQ].
(Eq. 5)
The fluorescence intensities are shown by I0 and I, which are the fluorescence intensities of
fluorophore in the absence and presence of quencher, respectively. The concentration of

quencher is indicated by [BQ]. KSV is the Stern–Volmer constant [31]. The ratios of I0/I were
calculated and plotted against [BQ] according to Equal 5, and KSV was determined from the
slope [36].
3.3.4. Determination of Binding of Pc Compounds with CT-DNA
The use of UV-vis spectroscopy to determine the mode of binding of a compound to DNA is a
useful in vitro instrumental technique that gives information about band position in the
spectrum for the molecular interaction based on shifting [18,37,38]. Shifting indicates the
strength of the interaction between DNA and Pcs, in which in these aqueous solutions of Pcs
cause aggregation and this aggregation can sometimes be severe. In some cases, aggregation
can greatly reduce the Q band absorption [39]. The interaction of Pcs with DNA was
investigated by electronic absorption spectroscopy in terms of how the Pcs change the UV-
absorption band in the presence of DNA, and the interaction between the double bonded DNA
with the Pcs during the titration of the DNA [18, 38,40]. The UV spectrum of compound 3a
was recorded at constant (7.5 µM) concentration before and after the stepwise increase in DNA
concentration (0, 5, 10, 15, 20, 25 µM) for DNA binding studies. In the event of intercalation a
strong stacking interaction occurs between compounds and the base pairs of DNA, and with
this strong stacking interaction the binding of an intercalative compound to DNA causes
hypochromism (decrease in absorption intensity) and significant bathochromism (red shift at
wavelength) in the absorption spectrum [38-40]. Compound 3a was studied in different DNA
concentrations and the results are shown in Figure 11.
Figure 11 UV-vis absorption spectra of 3a upon increasing amounts of CT-DNA (0, 5, 10, 15, 20, 25 µM) (from
top to bottom).

The increase in DNA concentration between 400 and 750 nm exhibited for compound 3a in the
optimal absorption condition remained stable, but the spectral data exhibited hypochromism
(decrease in absorbance value) upon the addition of CT-DNA. Hypochromism is the spectral
feature of dsDNA showing changes in the double helix structure, and which is an indicator of
electrostatic or intercalation-like interactions between dsDNA and compounds, and also must
be accompanied by a red shift (bathochromic shift) for an intercalative interaction [41].
In electronic absorption titration, batchromism (redshift), hypochromite and isosbestic point,
because of π-π* strong interaction between tert-butyl substituent and DNA bases are compatible
with intercalation [42]. The stacking interaction of the Pcs and DNA base pairs, are affected by
binding electron donating tert-butyl substituent on the Pcs ring, and this electron-donating
substituents are also exhibit the interaction of the aromatic π system on the metal atom in the
cavity. The stacking interaction between aromatic π system on the metal and electron donating
system for compound 3a caused 31% bathochromism (Figure 11). Also, the hypochromic effect
was observed without any red shifting, non-intercalative binding mode of 3a with CT-DNA.
3.3.5. DPPH Radical Scavenging Assay
The basis of this method is the reduction of DPPH with a synthesized molecule gives a strong
violet color during reduction. This reduction causes the color of the radical to change from
violet to yellow during reduction at quantifiable levels using a spectrophotometer in 517 nm
[43]. The antioxidant capacity of synthesized compounds is detected by DPPH radical
scavenging assay[18, 40,44]. In the present study, Pcs were synthesized that have the ability to
scavenge DPPH radicals. The experiment was carried out according to a previously described
procedure[17]. After the preparation of the Pc stock solutions in DMSO, DPPH solution in
MeOH was mixed and then the stock solution was used at different concentrations ranging from
25 to 50 mL in the experiment. DMSO as a control was used in instead of the tested Pcs. The
DPPH radical cleaning capacity of the Pcs is exhibited in Table 3 against gallic acid in different
concentrations. The observation of the antioxidant capacity for compound 3b (32.81 ± 0.40%
for 100 µM concentration) may have higher DPPH activity than compounds 3a (14.55 ± 0.19%
) and 3c (22.74 ± 0.15% for 100 µM concentration), since it has redox active metal atoms, and
the results showed that the antioxidant capacities for Pcs (3a, 3b, and 3c) , are not as effective
as gallic acid, when their DPPH radical cleaning capacity calculated according to the

concentration range (14.57 ± 0.31%, 22.58 ± 0.35%, 30.63 ± 0.32%, 32.81 ± 0.40%) (Table 3,
Figure 12).
As a result, it is though that the effect of the electron donating system (tert-butyl groups bearing
pheripheral position) give rise to the change electron density around center metal atom in the
cavity of MPc and influenced by resonance of localized π electron system. The DPPH behavior
is directly relative to this resonance of localized π electron system, and metal atom that entering
to the cavity of MPc have directly affected by the π electron system and also, this resonance
localized π electron system, change the result of DPPH or redox activity of center metal atoms.
So, gallic acid showed more DPPH free radical scavenging activity than the tested compounds
(3a, 3b, and 3c).
Table 3. Radical-scavenging activity on DPPH radicals (%) of the phthalocyanines.
µMa
25
3a
3b
14.57 ± 0.31 b
3c
Gallic Acidc
68.88 ± 0.40 b
81.53 ± 0.42 b
87.71 ± 038 b
90.58 ± 0.50 b
3.02 ± 0.09 b
7.79 ± 0.12 b
9.39 ± 0.15 b
5.55 ± 0.11 b
8.46 ± 0.11 b
50
22.58 ± 0.35 b
30.63 ± 0.32 b
32.81 ± 0.40 b
75
15.52 ± 0.19 b
22.74 ± 0.15 b
100
14.55 ± 0.19 b
a Four experiments were performed for all compounds in each experiment in triplicate.
b
Mean values ± SD are shown for triplicate experiments.
c Reference compound.
Figure 12. Scavenging ability of compounds
3.3.6. Metal Ions Chelating Effects Assay

Fe+2 is a feasible therapeutic approach to prevent radicals in Fe+2 chelation metabolism, as
single electrons are capable of acting from peroxides that permit the formation of alkoxy
radicals [18,45]. Divalent iron chelates ferrozine iron quantitatively by forming a colored
complex. The presence of another chelator may hinder complex formation, which leads to a
decrease in color, and the measurement of this color reduction helps to predict the chelating
capacities of the chelator candidates [45]. The Pcs metal chelating activity was conducted at 25,
50, 75, and 100 metal concentrations by using 1 mM stock solutions in DMSO. The chelating
(%) activity of ions and complexes (3a, 3b, and 3c) shows that chelating activity is increased
relative to the increasing concentrations used (Table 4). At the end of the experiment 3c was
found to be good chelator for Fe+2 chelating capacity, as 26.96 ± 0.39%, up to 100 µM
concentration. The other complexes (3a and 3b) showed lower iron-containing ion chelating
properties compared to EDTA, The results showing that they have high metal chelating
properties at the different concentrations mentioned for Pcs are reported in the Table 4 [18].
According to the results in table 4, the tert-butyl substituent bearing onto peripheral position of
the Pcs were positively affected the cavity. So, it can be say that the Pc gained ferrous ion-
ferrozine complex formation (FIC ability) owing to involving metal atoms in the inner core and
have affected the lower values of Pcs and gained high antioxidant properties. Also, the ferrious
chelating activity and concentration of compound was exhibited in the plot in Fig. 13.
Table 4. Ferrous ions chelating activity (%) of the phthalocyanines.
µMa
25
3a
3b
10.63 ± 0.22 b
3c
EDTAc
15.65 ± 0.15 b
2.25 ± 0.11 b
5.41 ± 0.05 b
8.63 ± 0.07 b
5.87 ± 0.25 b
50
16.52 ± 0.09 b
21.74 ± 0.76 b
24.96 ± 0.51 b
11.52 ± 0.37 b
17.63 ± 0.24 b
26.96 ± 0.39 b
51.42 ± 0.18 b
82.31 ± 0.08 b
96.85 ± 0.21 b
75
100
11.62 ± 0.06 b
a Four experiments were performed for all compounds in each experiment in triplicate.
b
Mean values ± SD are shown for triplicate experiments.
c Reference compound.

Figure 13. Chelating ability of the compounds.
4. Conclusion
Three new phthalocyanines were prepared. For the synthesis of MPcs [M = Zn (3a) and M =
Co (3b)], the 4-(2-(4-(tert butyl)phenoxy)ethoxy) phthalonitrile 2 was reacted with metal salts
(Zn(OAc)2.2H2O, Co(OAc)2.4H2O) in the presence of a catalyst (DBU). For the synthesis of
metal-free phthalocyanine [H2Pc (3c)], without using a metal salt as mentioned, the 4-(2-(4-
(tert butyl)phenoxy)ethoxy) phthalonitrile was reacted in the same condition. The
photophysical and photochemical parameters of the resulting molecules (3a, 3b, and 3c) were
determined. The photodegradation quantum yield (Φd) of 3a and 3c are higher than those of
standard ZnPc (Tablo 2). In the photochemical study, the singlet oxygen production and photo
degradation of 3a were measured. Photodegradation showed an increase parallel to the
literature. Therefore, 3a has the potential to be used in photodynamic therapy.
The DNA binding mode of Pcs with CT-DNA was analyzed quantitatively. Kb values of 3a
estimated from the Wolfe–Shimmer equation were 5.2 (± 0.52) 103 M–1. The binding constant
of 3a is lower than that of ethidium bromide, a known DNA intercalator (Kb = 1.23 ± 0.07 ×
105). These results suggest the existence of non-intercalative interactions between the
synthesized Pcs and CT-DNA.
When the results obtained in this study are compared with those of other studies done with Pcs,
it is possible to see compounds with similar Kb values [15,40]. Moreover, these higher Kb values
were reported for a zinc Pc [40] and manganese and copper Pcs [29]. In addition, the Pc 3b is a
good chelator for Fe+2 chelating capacity with 24.96 ± 0.51% up to 100 µM concentration. The

other Pcs (3a and 3c) show low iron-containing ion chelating properties compared to EDTA.
The DPPH radical cleaning capacity of Pcs was shown against gallic acid in different
concentrations. The observation of the highest antioxidant capacity exhibited for all Pcs (3a,
3b, and 3c) showed they were not as effective as gallic acid when their DPPH radical cleaning
capacity was calculated according to the concentration range (14.57 ± 0.31%, 22.58 ± 0.35%,
30.63 ± 0.32%, 32.81 ± 0.40%).
CONFLICT OF INTEREST
The authors confirm that this article content has no conflict of interest.
ACKNOWLEDGEMENT
This study was supported by The Scientific and Technological Research Council of Turkey
(TÜBİTAK, project no: 115Z446 and 217Z043).
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Photophysical, photochemical and DNA binding studies of prepared
phthalocyanines

Arif Baran*, Sumeyye Çol, Emel Karakılıç , Furkan Özen
Sakarya University, Faculty of Arts and Sciences, Chemistry Department, 54187, Sakarya,
Turkey
abaran@sakarya.edu.tr
Graphical Abstract
3a,
The Pc
exhibited high excitation
and emission and also have good Stokes
hift relative to Zn-Pc in lit.
N
3c
PC- , have a
3a
Pc
has high
good chelating
N
N
photodegradation
quantum yield than
Zn-Pc known
N
capacity as
chelator for Fe+ 2
N
M
N
N
.
N
in literature
All synthesized PCs,
have good soluble and also have
low aggregation in organic solvents
Photophysical, photochemical and DNA binding studies of prepared
phthalocyanines
Arif Baran*, Sumeyye Çol, Emel Karakılıç , Furkan Özen
1Sakarya University, Faculty of Arts and Sciences, Chemistry Department, 54187, Sakarya,
Turkey
abaran@sakarya.edu.tr
Highlights
•
•
Three new and efficient synthesis of phthalocyanine were performed.
The soluble and aggregation behavior of new Pcs were examined.

•
DNA binding, metal chelating, and DPPH radical scavenging activity were investigated.
Figures
Ha
Hb
Hb
Ha
CN
Ha'
Ha'
Hb'
Hb'
2
C1
3
3
2
C2
4
1
4
1
O
O
CN
O
OH
3'
2'
2'
C3
C4
1
3'
2
Figure 1. 2-(4-(tert-butyl)phenoxy)ethan-1-ol (1) and 4-(2-(4-(tert-butyl)phenoxy)ethoxy) phthalonitrile (2)
700
600
500
400
300
200
100
0
1.6
1.4
1.2
1
Excitation
Emission
Absorption
0.8
0.6
0.4
0.2
0
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700
Wavelength (nm)
800
Figure 2. Absorption, excitation, and emission spectra of compound 3a in DMF. Excitation wavelength 682 nm.
800
700
600
500
400
300
200
100
0
1.2
1
Excitation
Emission
Absorption
0.8
0.6
0.4
0.2
0
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400
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Wavelength (nm)

Figure 3. Absorption, excitation, and emission spectra of compound 3c in DMF. Excitation wavelength 672, 718
nm.
Figure 4. UV-vis of 3a (1.0×10–5 M) in different solutions.
Figure 5. UV-vis of 3b (1.0×10–5 M) in different solutions.

Figure 6. UV-vis of 3c (1.0×10–5 M) in different solutions.
Figure 7. Absorption spectral changes of compound 3a in DMF at concentrations from 2×10–6 to 1×10–5 M.
Figure 8. Absorbance changes for the determination of singlet oxygen quantum yield of complex 3a (1.0×10–5
M) in DMF using DPBF as singlet oxygen quencher. (Inset: plot of DPBF absorbance versus time).