SOD activity and DNA binding properties of a new symmetric porphyrin Schiff base ligand and its metal complexes

Article abstract of DOI:10.1016/j.saa.2015.07.044

4-Methoxy-2,6-bis(hydroxymethyl)phenol (1) was prepared from the reaction of 4-methoxyphenol and formaldehyde. The compound (1) was then oxidized to the 4-methoxy-2,6-diformylphenol (2) compound. Molecular structure of compound (2) was determined by X-ray

Full text of DOI:10.1016/j.saa.2015.07.044

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
SOD activity and DNA binding properties of a new symmetric porphyrin
Schiff base ligand and its metal complexes
⇑
Sevim Çay, Muhammet Köse, Ferhan Tümer, Aysßegül Gölcü, Mehmet Tümer
Chemistry Department, K.Maras Sütcü Imam University, 46100 K.Maras, Turkey
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
ꢀ
4-Methoxy-2,6-diformylphenol
compound has been characterized by
single crystal X-ray diffraction.
A new porphyrin Schiff base ligand
and its transition metal complexes
have been synthesized.
Superoxide dismutase activity and
DNA-binding properties of this type
compounds were investigated for the
first time.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 May 2015
Received in revised form 15 June 2015
Accepted 7 July 2015
Available online 8 July 2015
4-Methoxy-2,6-bis(hydroxymethyl)phenol (1) was prepared from the reaction of 4-methoxyphenol and
formaldehyde. The compound (1) was then oxidized to the 4-methoxy-2,6-diformylphenol (2) compound.
Molecular structure of compound (2) was determined by X-ray diffraction method. A new symmetric por-
phyrin Schiff base ligand 4-methoxy-2,6-bis[5-(4-iminophenyl)-10,15,20-triphenylporphyrin]phenol (L)
was prepared from the reaction of the 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (TTP-NH2) and
the compound (2) in the toluene solution. The metal complexes (Cu(II), Fe(III), Mn(III), Pt(II) and Zn(II))
of the ligand (L) were synthesized and characterized by the spectroscopic and analytical methods. The
DNA (fish sperm FSdsDNA) binding studies of the ligand and its complexes were performed using UV–vis
spectroscopy. Additionally, superoxide dismutase activities of the porphyrin Schiff base metal complexes
were investigated. Additionally, electrochemical, photoluminescence and thermal properties of the com-
pounds were investigated.
Keywords:
Porphyrin-Schiff base
Superoxide dismutase activity
DNA-binding
Spectroscopy
Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction
Schiff bases and their transition metal complexes [4–10] which
report the X-ray structural characterization, antioxidant, anti-
Schiff base ligands and their metal complexes exhibit significant
catalytic activity in many biological systems, and they can be used
as efficient materials in the polymerization reactions, functional
dyes and pigments, medical and pharmaceutical areas [1]. The
chromium(III) and manganese(III) salen complexes, for example,
have been used as efficient catalysts in epoxidation of alkenes [2].
Especially, Schiff base derivatives have been used in the research
on the biological activity studies, and so much works in this area
were published [1,3]. Recently, we published several paper on
cancer, DNA-binding, antimicrobial, photoluminescence, catalytic
activity and electrochemical properties of the ligands and their
complexes. In the DNA binding studies, we established covalent or
non-covalent interactions between the ligands (or their metal com-
plexes) and DNA [4,5]. The hydroxy and methoxy-substituted Schiff
bases have received considerable attention due to their potential
anticancer activity. In the anticancer activity studies, we found sub-
stituent and its position effect on the C6 cell line [9]. Hydroxy or
methoxy groups on the ortho position of the benzenoid ring more
effective than the meta and para position of the benzenoid ring [10].
In view of their special photophysical and electrochemical
⇑
Corresponding author.
E-mail address: mtumer@ksu.edu.tr (M. Tümer).
properties
and
considerable
stability,
porphyrins
and
http://dx.doi.org/10.1016/j.saa.2015.07.044
1386-1425/Ó 2015 Elsevier B.V. All rights reserved.

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S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
Scheme 1. Synthesis of 4-Methoxy-2,6-bis[5-(4-iminophenyl)-10,15,20-triphenylporphyrin]phenol and its metal complexes.
metalloporphyrins have been utilized in many applications such as
in light-activated cancer cure (photodynamic therapy) [11] and
gene therapy [12], fluorescent and electrochemical sensors [13].
They are useful elements of light-harvesting systems [14] and
could be used as artificial endonucleases [15]. Porphyrin com-
pounds and their metal complexes can be taken up by tumor cells
[16] and were utilized as a tumor targeting agent in photodynamic
therapy (PDT) [17]. PDT, in which light activates a photosensitizing
drug and elicits the 1O2-mediated cytotoxic action, has recently
Superoxide dismutase (SOD), catalase and glutathione peroxi-
dase are significant scavengers of the reactive oxygen intermedi-
ates (ROI). Of these enzymes, manganese-SOD (Mn-SOD), which
is embedded in the mitochondrial matrices, is stimulated by cyto-
toxic and cell-spoil stimuli, and protects the cells from generated
superoxide (OÅ2ꢁ) [22,23]. It is pragmatic to guess that tumor cells
which have a high level of Mn-SOD can better protect themselves
across fatal cytotoxic actuators with respect to those with low
Mn-SOD activity. Nevertheless, some researchers reported that
tumor cells with high Mn-SOD activity were delicate to anticancer
emerged as
a promising modality against cancer and allied
diseases [18]. To develop efficient chemotherapeutic agents and
anticancer drugs, it is important to investigate the interactions of
metal complexes with DNA. Porphyrins and their derivatives
are also one of the most investigated DNA-binding agents [19].
The interaction of porphyrins with DNA have been prevalently
studied in the past decades [20]. The binding can be either
intercalative or external, in the minor groove (in some special
cases with self-stacking), depending on the charge distribution of
the porphyrin and the type of the central metal as well as the
peripheral substituents [21].
drugs and c-rays [24,25].
In this paper, the 4-methoxy-2,6-bis(hydroxymethyl)phenol
(1), 4-methoxy-2,6-diformylphenol (2), 5,10,15,20-tetraphenylpor
phyrin
(TPP),
5-(4-Nitrophenyl)-10,15,20-triphenylporphyrin
(TPP-NO2) and TPP-NH2 compounds were synthesized and charac-
terized. The new symmetric porphyrin Schiff base ligand (L) and its
Cu(II), Pt(II), Zn(II), Fe(III) and Mn(III) transition metal complexes
(Scheme 1) were synthesized and characterized by the elemental
analyses, MALDI-TOF Mass, UV–Vis, FT-IR, photoluminescence
and 1H(13C)-NMR spectra. Their electrochemical and thermal

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
823
Fig. 1. The 1H NMR and 13C NMR spectra of the compound (1) (top) and compound (2) (bottom).
properties were also investigated. Superoxide dismutase (SOD)
activity of the porphyrin Schiff base Cu(II) and Mn(III) complexes
was investigated. The DNA (fish sperm FSdsDNA) binding studies
of the complexes were performed using UV–vis spectroscopy.
932. Infrared spectra were obtained using KBr disk (4000–
400 cmꢁ1) on a Perkin Elmer Spectrum 100 FT-IR. The electronic
spectra in the 200–900 nm range were obtained on a Perkin
Elmer Lambda 45 spectrophotometer. 1H and 13C NMR spectra
were recorded on a Bruker 400 MHz instrument and TMS was used
as an internal standard and CDCl3 as solvent. The thermal studies
of the compounds were performed on a Perkin Elmer STA 6000
simultaneous Thermal Analyzer under nitrogen atmosphere at a
heating rate of 10 °C/min. The MS spectra complexes were
obtained in dihydroxybenzoic acid as MALDI Matrix using nitrogen
laser accumulating 50 laser shots using Bruker Microflex LT MALDI
TOF mass spectrometer.
2. Experimental
2.1. Materials and physical measurements
All reagents and solvents were of reagent-grade quality and
obtained from commercial suppliers (Aldrich or Merck).
Elemental analyses (C,H,N) were performed using a LECO CHNS

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S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
Table 1
reference electrode (BAS). All potentials are reported with respect
to Ag+/AgCl. The solutions were deoxygenated by passing dry
nitrogen through the solution for 30 min prior to the experiments,
and during the experiments the flow was maintained over the
solution. Digital simulations were performed using DigiSim 3.0
for windows (BAS, Inc.). Experimental cyclic voltammograms used
for the fitting process had the background subtracted and were
corrected electronically for ohmic drop. Mettler Toledo MP 220
pH meters was used for the pH measurements using a combined
electrode (glass electrode reference electrode) with an accuracy
of 0.05 pH.
X-ray data for 4-methoxy-2,6-diformylphenol.
Identification code
Empirical formula
Formula weight
Crystal size (mm3)
Crystal color
Crystal system
Space group
Unit cell
2
C9H8O4
180.15
0.34 ꢂ 0.22 ꢂ 0.06
Colorless
Orthorhombic
Pca2(1)
a (Å)
b (Å)
c (Å)
32.0052(17)
3.8043(2)
26.1897(14)
90
90
90
3188.8(3)
16
0.120
27,904
100%
Data collection for X-ray crystallography was completed using a
Bruker APEX2 CCD diffractometer and data reduction was per-
formed using Bruker SAINT [26]. SHELXS97 and SHELXL2014/6
were used to solve and refine structures, respectively [27].
a
(°)
b (°)
(°)
c
Volume (Å3)
Z
Abs. coeff. (mmꢁ1
Refl. collected
)
2.2. Preparation of the 4-methoxy-2,6-bis(hydroxymethyl)phenol (1)
Completeness to h = 27.16°
Ind. Refl. [Rint
R1, wR2 [I > 2
R1, wR2 (all data)
CCDC number
]
r
7032 [0.0404]
0.0393, 0.0893
0.0526, 0.0981
1,050,229
4-Methoxyphenol (25.0 g, 0.17 mol) was added to a stirred
warm (70 °C) solution of NaOH (10.60 g, 0.27 mol) in THF
(200 mL). To the stirring mixture p-formaldehyde (45.0 g,
0.61 mol) was added and the mixture was stirred for 48 h at room
temperature. THF was removed on a rotary evaporator. The result-
ing solid was dissolved in distilled water (100 mL), acidified with
HCl (0.5 M) and extracted with diethylether. The diethylether solu-
tion was dried over Na2SO4 and the solvent was removed on a
rotary evaporator. The white crystalline product was collected
and dried in vacuo. (32.45 g, 70%). 1HNMR (CDCl3, TMS): d 6.75
(s, 2H, Ar-H), 4.52 (s, 4H, ACH2OA), 3.66 (s, 3H, AOCH3). 13CNMR
(CDCl3, TMS): d 152.84–111.34 (Ar-C), 59.61 (ACH2O), 55.66
(I)]
The single-photon fluorescence spectra of the porphyrin-Schiff
base compound (H2L) and its metal complexes were collected on
a Perkin Elmer LS55 luminescence spectrometer. All samples were
prepared in spectrophotometric grade solvents and analyzed in a
1 cm optical path quartz cuvette. The solutions of the ligand
(1.0 ꢂ 10ꢁ3–1.0 ꢂ 10ꢁ7 mol Lꢁ1) were prepared in DMSO, DMF,
CH2Cl2 and toluene solvents. To investigate the solvent effect on
the photoluminescence properties of the ligand and its transition
metal complexes, the DMSO, DMF, CH2Cl2 and toluene solutions
were used.
(AOCH3). FTIR(KBr)/cmꢁ1: 3312
1480 (aryl CAC).
m(OH), 2939 m(CAH)alph, 1611,
m
A
stock solution of concentrations of 1 ꢂ 10ꢁ3
M and
2.3. Preparation of the 4-methoxy-2,6-diformylphenol (2)
1 ꢂ 10ꢁ4 M of the porphyrin-Schiff base compound was prepared
in DMF solution for electrochemical studies. Cyclic voltammo-
grams were recorded on a Iviumstat Electrochemical workstation
equipped with a low current module (BAS PA-1) recorder. The elec-
trochemical cell was equipped with a BAS glassy carbon working
electrode (area 4.6 mm2), a platinum coil auxiliary electrode and
a Ag+/AgCl reference electrode filled with tetrabutylammonium
tetrafloroborate (0.1 M) in DMF and CH3CN solution and adjusted
to 0.00 V vs. SCE. Cyclic voltammetric measurements were per-
formed at room temperature in an undivided cell (BAS model C-3
cell stand) with a platinum counter electrode and an Ag+/AgCl
Activated MnO2 (40 g) was added to CHCl3 (200 mL) in a 500 mL
round bottom flask equipped with an overhead stirrer and a
water-cooled condenser. The mixture was heated to reflux with
stirring about 15 min, then the powder of the 4-methoxy-2,6-bis(h
ydroxymethyl)phenol (5 g) was added. After being kept refluxing
for 24 h, the reaction was cooled to room temperature and filtered.
The solid was washed by CHCl3 (40 mL ꢂ 5) thoroughly until the
filtrate was colorless. Then the filtrate was concentrated on a
rotary evaporator yielding a yellow solid. (2.62 g, 53%).
1HNMR (CDCl3, TMS): d 11.09 (OH), 10.25 (s, 2H, carbonyl-H),
7.60 (s, 2H, Ar-H), 3.82 (s, 3H, OCH3). 13CNMR (CDCl3, TMS): d
191.84 (carbonyl-C), 157.98–122.43 (Ar-C), 56.17 (AOCH3).
Table 2
Hydrogen bonds for 4-methoxy-2,6-diformylphenol (2) [Å and °].
FTIR(KBr)/cmꢁ1: 3350
1485 (aryl CAC).
m(OH), 2960 m(CH)alph, 1673 m(C@O), 1598,
D–Hꢃ ꢃ ꢃA
d(D–H)
d(Hꢃ ꢃ ꢃA)
d(Dꢃ ꢃ ꢃA)
<(DHA)
m
O(2)–H(2)ꢃ ꢃ ꢃO(1)
0.84
0.84
0.84
0.95
0.84
0.84
0.84
0.95
0.98
0.95
0.95
0.95
0.98
0.95
0.95
0.95
0.98
1.95
2.43
1.92
2.49
2.61
1.91
1.92
2.60
2.48
2.55
2.58
2.47
2.45
2.52
2.52
2.54
2.50
2.677(3)
2.923(2)
2.654(3)
3.375(3)
3.089(3)
2.637(3)
2.650(3)
3.453(3)
3.461(3)
3.478(3)
3.272(3)
3.398(4)
3.384(3)
3.451(3)
3.409(3)
3.449(3)
3.423(3)
144.7
118.5
145.3
155.8
117.6
144.2
145.0
150.4
174.4
165.0
130.2
166.8
159.6
165.0
155.0
161.5
156.8
O(2)–H(2)ꢃ ꢃ ꢃO(10)i
O(6)–H(6A)ꢃ ꢃ ꢃO(5)
2.4. Preparation of the 5,10,15,20-tetraphenylporphyrin (TPP)
C(6)–H(6)ꢃ ꢃ ꢃO(15)ii
O(10)–H(10)ꢃ ꢃ ꢃO(2)iii
O(10)–H(10)ꢃ ꢃ ꢃO(9)
O(14)–H(14)ꢃ ꢃ ꢃO(13)
C(15)–H(15)ꢃ ꢃ ꢃO(11)i
C(18)–H(18A)ꢃ ꢃ ꢃO(9)iv
C(22)–H(22)ꢃ ꢃ ꢃO(16)ii
C(24)–H(24)ꢃ ꢃ ꢃO(7)v
C(26)–H(26)ꢃ ꢃ ꢃO(1)vi
C(27)–H(27B)ꢃ ꢃ ꢃO(15)ii
C(31)–H(31)ꢃ ꢃ ꢃO(12)vii
C(34)–H(34)ꢃ ꢃ ꢃO(3)viii
C(35)–H(35)ꢃ ꢃ ꢃO(5)
C(36)–H(36B)ꢃ ꢃ ꢃO(11)vii
Benzaldehyde (9.51 g, 0.09 mol) and pyrrole (6.03 g, 0.09 mol)
were added simultaneously to
a refluxing propionic acid
(250 mL). After refluxing for 30 min, the solution was cooled to
room temperature and left overnight for the product to settle.
The reaction mixture was filtered and washed thoroughly first with
methanol and then with water. Column chromatography with
dichloromethane as eluent was performed on the purple
crystals to get rid of impurities and chlorin. Recrystallisation of
the first band from dichloromethane/methanol gave metal-free
tetraphenylporphyrin (TTP) (2.61 g, 19%). Melting point: >200 °C.
dH (CDCl3)/ppm: 8.85 (s, 8H, pyr-CH), 8.29 (m, 8H, 4 ꢂ C6H5),
7.77 (m, 12H, 4 ꢂ C6H5), ꢁ2.71 (s, 2H, pyrrole internal NH). FTIR
Symmetry transformations used to generate equivalent atoms: i: x + 1/2, ꢁy, z; ii: x,
y ꢁ 1, z; iii: xꢁ1/2, ꢁy + 1, z; i : ꢁx + 1/2, y, z – 1/2; : ꢁx + 1/2, y ꢁ 1, z + ½; vi: x ꢁ 1/
2, ꢁy, z; vii: x, y + 1, z; viii: ꢁx + ½, y ꢁ 1, z ꢁ 1/2.
(KBr,
m
,
cmꢁ1): 3311 (NH), 3021 (aryl CAH), 1594
v
v
(CH@N)porphyrin, 1553 (CAC)aryl, 1347 (C@C). UV–Vis [Toluene,

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
825
Fig. 2. Molecular structure of 2,6-diformyl-4-metoxyphenol with atom numbering.
Fig. 3. Hydrogen bond interactions within the structure of 2,6-diformyl-4-metoxyphenol.
kmax(nm),
e
max (Mꢁ1 cmꢁ1)]: 416 nm (4.30 ꢂ 105), 515 (1.30 ꢂ 104),
nitrogen. SnCl2ꢃ2H2O (0.28 g, 1.2 mmol) was added to the solution,
and the reaction was heated to 65 °C for 4 h. The porphyrin solu-
tion was cooled and added to 30 mL of cold water and was adjusted
to pH 8 with concentrated ammonium hydroxide. The aqueous
phase was extracted with chloroform, which was dried over mag-
nesium sulfate. The organic phase was concentrated under pres-
sure and purified by silica column with dichloromethane as an
eluent to give 5-(4-aminophenyl)-10,15,20-triphenylporphyrin
(0.22 g, 89%). 1HNMR (CDCl3) d: 8.93 (d, 2H, b-pyrrole),
8.86 (d, 2H, b-pyrrole), 8.85 (s, 4H, b-pyrrole), 8.20 (m, 6H,
o-triphenyl), 8.01 (d, 2H, 4-aminophenyl), 7.76 (m, 9H, m-/p-tri-
phenyl), 7.09 (d, 2H, 4-aminophenyl), 4.04 (s, 2H, amino), ꢁ2.72
550 (4.23 ꢂ 104), 592 (1.71 ꢂ 104), 648 (0.55 ꢂ 104).
2.5. Preparation of the 5-(4-Nitrophenyl)-10,15,20-triphenylporphyrin
(TPP-NO2)
To
a solution of 5,10,15,20-tetraphenylporphyrin (0.20 g,
0.33 mmol) in trifluoroacetic acid (TFA) (10 mL) was added sodium
nitrite (0.035 g, 0.59 mmol). After stirring for 3 min at room temper-
ature, the reaction was poured into water (100 mL) and extracted
with dichloromethane (6 ꢂ 25 mL). The organic layer was washed
with saturated aqueous NaHCO3, water, and then dried over magne-
sium sulfate. The residue was purified on a plug of silica gel, eluting
with dichloromethane. Solvent removal gave 5-(4-nitrophe
nyl)-10,15,20-triphenylporphyrin (0.14 g, 64%). Melting: point > 200 °C.
1H-NMR: dH (CDCl3)/ppm: 8.87 (m, 6H, pyr-CH), 8.77 (d, 2H,
pyr-CH), 8.69 (m, 2H, C6H4), 8.40 (m, 2H, C6H4), 8.24 (m, 6H,
3 ꢂ C6H5), 7.75 (m, 9H, 3 ꢂ C6H5), ꢁ2.72 (s, 2H, pyrrole internal
(s, 2H, pyrrole internal NH). FTIR (KBr,
m
, cmꢁ1): 3318 (NH), 2973
1506 (CAC)aryl, 1349 (C@C).
(CAH), 1615 (CH@N)pyrrole
,
UV–Vis [Toluene, kmax(nm), emax (Mꢁ1 cmꢁ1)]: 425(3.34 ꢂ 104),
524(0.40 ꢂ 104), 560(0.30 ꢂ 104), 587(0.20 ꢂ 104), 650(0.10 ꢂ 104).
2.7. Preparation of the 4-methoxy-2,6-bis[5-(4-iminophenyl)-
10,15,20-triphenyl porphyrin] phenol (L)
NH). FTIR (KBr,
m,
cmꢁ1): 3315 (NH), 2988 (CAH), 1594
(CH@N)porphyrin, 1557 (CAC)aryl, 1515, 1344 (NO2), 1344 (C@C). UV–
Vis [Toluene, kmax(nm), emax (Mꢁ1 cmꢁ1)]: 418 (4.10 ꢂ 105), 514
(3.11 ꢂ 104), 549 (0.95 ꢂ 104), 589 (0.88 ꢂ 104), 646 (0.75 ꢂ 104).
The porphyrinSchiffbase ligandwas synthesizedas follows:TTP-
NH2 (0.126 g, 0.2 mmol) and the 4-methoxy-2,6-diformylphenol
aldehyde compound (0.180 g, 0.1 mmol) was dissolved in 100 ml
0
2.6. Synthesis of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin
(TPP-NH2)
of dry toluene containing 4 ÅA molecular sieves. The resulting solu-
tion was refluxed until the disappearance of the TTP-NH2, monitored
by TLC (30 h). The solvent was removed under reduced pressure and
the crude product was dissolved in CH2Cl2 and filtered. Evaporation
of the solvent gave purple solid. The obtained product was purified
5-(4-Nitrophenyl)-10,15,20-triphenylporphyrin (0.26 g, 0.39 mmol)
was dissolved in 10 mL of concentrated hydrochloric acid under

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H, 3.45; N, 8.01%. FTIR (KBr,
m
, cmꢁ1): 3005 (CAH)aromatic, 2950
1538 (CAC)aromatic 1342
(CAH)aliphatic 1593 (CH@N)imine
,
,
,
(CAO)phenolic, 996 (Cu-N)porphyrin, 580 (CuAO), 450 (CuAN). MALDI-
TOF-MS, (m/z): Calculated: 1759.13; found: 1757.15 [C97H61Cl3
Cu4N10O2]+, calcd: 1525.68; found: 1527.26 [C97H63Cu2N10O2]+.
LPt4Cl3: Yield: 75.6%, purple red solid. M.p. > 300 °C; Anal. Calcd.
For [C97H61N10O2Cl3Pt4]: C, 50.98; H, 2.69; N, 6.13%; found: C,
51.05; H, 2.74; N, 6.20. FTIR (KBr,
m ,
, cmꢁ1): 3013 (CAH)aromatic
2918 (CAH)aliphatic, 1600 (CH@N)imine, 1516 (CAC)aromatic, 1397
(CAO)phenolic, 999 (Pt-N)porphyrin, 550 (Pt-O), 445 (Pt-N). MALDI-
TOF-MS, (m/z): Calculated: 2285.28; found: 2285.28 [C97H61Cl3
N10O2Pt4]+, calcd: 2055.43; found: 2054.74 [C97H61Cl2N10O2Pt3]+.
LZn4Cl3: Yield: 67%, purple red solid. M.p. > 300 °C. Anal. Calcd.
For [C97H61N10O2Cl3Zn4]: C, 65.95; H, 3.48; N, 7.93%; found: C,
66.02; H, 3.54; N, 7.98%. FTIR (KBr, m ,
, cmꢁ1): 3005 (CAH)aromatic
2922 (CAH)aliphatic, 1619 (CH@N)imine, 1539 (CAC)aromatic, 1319
(CAO)phenolic, 990 (Zn-N)porphyrin, 560 (Zn-O), 440 (Zn-N). MALDI-
TOF-MS, (m/z): Calculated: 1766.58; found: 1699.55 [C97H63N10
O2Cl3Zn3]+, calcd: 1600.32; found: 1599.88 [C97H63N10O2Cl2Zn]+.
LFe3Cl4(H2O)3: Yield: 70%, purple red solid. M.p. > 300 °C. Anal.
Calcd. For [C97H67N10O5Cl4Fe3]: C, 66.06; H, 3.80; N, 7.94%; found:
C, 66.13; H, 3.88; N, 8.01%. FTIR (KBr,
2920 (CAH)aliphatic, 1602 (CH@N)imine, 1539 (CAC)aromatic, 1336
(CAO)phenolic 1001 (Fe-N)porphyrin 550 (FeAO), 445 (FeAN).
m ,
, cmꢁ1): 3058 (CAH)aromatic
,
,
MALDI-TOF-MS, (m/z): Calculated: 1761.98; found: 1734.47
[C97H67N10O5Cl4Fe3ꢁHCN]+, 1681.39 [C97H67N10O5Cl4Fe3ꢁ(HCN+
Cl+H2O)]+, 1629.58 [C97H67N10O5Cl4Fe3ꢁ(HCN+Cl2+H2O+CH3)]+,
1592.94 [C97H67N10O5Cl4Fe3ꢁ(HCN+Cl3+H2O+CH3)]+.
LMn3(AcO)4(H2O): Yield: 75%, purple black solid. M.p. > 300 °C.
Anal. Calcd. for [C105H75N10O11Mn3]: C, 69.32; H, 4.12; N, 7.70%;
Found: C, 69.25, H, 4.18; N, 7.64%. FTIR (KBr,
(H2O), 3020 (CAH)aromatic, 2922 (CAH)aliphatic, 1710 (C@O)acetic acid
m
, cmꢁ1): 3306
Fig. 4. Packing diagram of 2,6-diformyl-4-metoxyphenol. Hydrogen bonds are
shown as dashed lines.
,
1600 (CH@N)imine, 1539 (CAC)aromatic, 1340 (CAO)phenolic, 1010
(MnAN)porphyrin, 550 (MnAO), 430 (MnAN). MALDI-TOF-MS, (m/
z): Calculated: 1817.59; found: 1820.40 [C105H75N10O11Mn3+3H]+,
1684.45 [(C105H75N10O11Mn3+3H) – (2CH3COOꢁ+H2O)]+.
from CHCl3–hexane (v/v, 1/3) solvent mixture. C97H66N10O2, yield:
70%, Melting: point > 200 °C. Color: purple. Elemental analyses:
Found (calcd.)%: C, 82.96 (83.00), H, 4.80 (4.74), 9.94 (9.98).
1HNMR (CDCl3) d (ppm): 10.49 (s, H, OH), 8.98 (d, 2H, b-pyrrole),
8.90 (s, 4H, b-pyrrole), 8.80 (d, 2H, b-pyrrole), 8.64 (s, 2H, CH@N
(imine)), 8.41 (m, 6H, o-triphenyl-H), 8.28–7.82 (m, 9H 2H,
2.9. Superoxide dismutase (SOD) activity studies of the transition
metal complexes
(m-phenyl-H) (p-phenyl-H) aminophenyl),
7.60
(s,
2H,
diformyl-H), 3.84 (s, 3H, AOCH3), ꢁ2.81 (s, 2H, pyrrole internal
NH). 13C-NMR (CDCl3) d (ppm): 56.19, 112.55, 119.30, 117.14,
119.65, 121.92, 126.85, 128.06, 134.54, 135.67, 139.65, 146.25,
SOD assay kit-WST was used to evaluate SOD activities of the
complexes. All reagents were obtained from Sigma–Aldrich
Chemical Co. Ltd. In this method, superoxide was produced aerobi-
cally xanthine-xanthine oxidase enzyme system. The OÅ2ꢁ produced
reacts with 2-(4-iodophenyl)-5-(2,4-disulfophenyl)-2H-tetrazoliu-
m, monosodium salt (WST-1 to give the yellow WST-1 formazan
exhibits a characteristic absorbance peak at 440 nm, therefore,
quantitative reduction of WST-1 to WST-1 formazan by OÅ2ꢁ was
monitored spectrophotometrically at pH 7.8 on a UV-160A UV–
Vis. Spectrophotometer, Shimadzu at 440 nm and 25 °C for
20 min. A schematic representation of the method is illustrated
in Figs. (S1 and S2). In the presence of the complex being tested,
the absorbance values at 440 nm decrease. This is due to the com-
plex competes with the WST-1 to scavenge the OÅ2ꢁ. The rate of
absorption changes was determined and the percent inhibition
(IC50) of WST reduction to WST-1 formazan was calculated. The
WST-1 assay is an indirect method of analysis because the extent
of the reduction of the appearance of the yellow WST-1 formazan
in the presence of a SOD mimic is taken as a measure of SOD activ-
ity [28]. The IC50 values obtained are dependent upon the indicator
used and concentration of the indicator [WST] can be used to cal-
culate rate constant Kcat using the calculation proposed by McCord
and Fridovich [29] shown in the following equation:
148.88, 153.25, 162.50. FTIR (KBr,
(NH), 2950 (CH)aliphatic 1617 (CH@N), 1574 (CAC)aryl
1490 (CH@N)pyrrole
m
, cmꢁ1): 3313 (OH), 3075
,
,
,
1343 (C@C). MALDI-TOF-MS, (m/z):
Calculated: 1403.62; Found: 1406.42 [C98H68N10O2+4H]+, 793.73
[C53H41N6O2]+.
2.8. Preparation of the Cu(II), Fe(III), Mn(III), Pt(II) and Zn(II) metal
complexes of the 4-ethyl-2,6-bis[5-(4-iminophenyl)-10,15,20-
triphenylporphyrin]phenol (L)
The complexes were prepared according to a known procedure.
The porphyrin Schiff base ligand (0.702 g, 0.5 mmol,) was dissolved
in CH2Cl2 (20 mL) solution and the metal salts [2 mmol, 0.273 g for
ZnCl2; 0.342 for CuCl2ꢃ2H2O; 0.542 for FeCl3ꢃ6H2O; 0.830 g for
K2[Pt(Cl)4]; 0.464 g for Mn(AcO)3] were added to the mixture of
CH3OH (20 mL) and the solution was refluxed for about 1 h. The
extent of the reaction was monitored by measuring the UV–Vis
spectrum of the reaction solution every 10 min. After cooling to
room temperature, 200 mL distilled water was added to the reac-
tion mixture and extracted three times. Purity of the complexes
were checked by t.l.c. studies.
LCu4Cl3: Yield: 72.0%, green solid. M.p. > 300 °C. Anal. Calcd. For
[C97H61N10O2Cl3Cu4]: C, 66.23; H, 3.50; N, 7.96%; found: C, 66.15;
Kcat ¼ KWST-1 ꢂ ½WST-1ꢄ=IC50

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
827
L
LFe3Cl4(H2O)3
LZn4Cl3
Fig. 5. MALDI-TOFF spectra of the ligand (L) and its Fe(III) and Zn(II) complexes.

828
S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
where; Kcat
: rate constant KWST-1: rate of WST-1 reduction:
3.7 ꢂ 104 molꢁ1 L sꢁ1 (pH = 8), [WST-1]: concentration of WST-1.
2.10. DNA binding studies of the ligand and its metal complexes
Double-strand FSdsDNA (Sigma) was used as received. The
stock solution of DNA was prepared by dissolving appropriate
amount of DNA in Tris–HCl buffer (20 mM Tris–HCl, 20 mM NaCl,
pH 7.0) by gentle stirring at room temperature and stored at 4 °C
for no longer than a week. The ratio of the UV absorbance at 260
and 280 nm (A260/A280) was checked to be ca. 1.86, indicating that
the DNA is sufficiently free from protein contamination. The DNA
concentration per nucleotide phosphate [NP] was determined by
the UV absorbance at 260 nm after 1:20 dilutions using the known
e
value of 6600 Mꢁ1 cmꢁ1
.
3. Results and discussion
In order to use in the synthesis of the symmetric porphyrin
Schiff base ligand (L), the 4-methoxy-2,6-bis(hydroxymethyl)phe
nol (1) compound was prepared from the reaction of the
4-methoxyphenol and formaldehyde in the basic conditions (see
Supplementary file). The obtained compound was oxidized by acti-
vated MnO2 and then the 4-methoxy-2,6-diformylphenol (2) car-
bonyl compound was obtained. To characterize the compounds
(1 and 2), the analytical and spectroscopic methods were used.
The obtained analytical and spectroscopic data for the compounds
(1) and (2) are given in the experimental section. In the FTIR spec-
trum of the compound (1), the vibration bands at 3312, 2939, 1611
and 1480 cmꢁ1 can be attributed to the (OH), (CAH)alph, and (aryl
CAC) groups, respectively. In the compound (2), the hydrox-
ymethyl vibration at 3312 cmꢁ1 was disappeared and instead of
this band, the carbonyl group band (C@O) at 1673 cmꢁ1 was
occured. In the 1H-NMR spectrum of the compound (1) (Fig. 1),
the signal at 6.75 ppm may be assigned to the aromatic ring pro-
tons. The very strong singlets at 4.52 and 3.66 ppm can be attribu-
ted to the methylene (ACH2A) and methyl (AOCH3) protons,
respectively. The broad band at 3.40 ppm belongs to the hydroxy
protons of the hydroxymethyl groups. In the 13C-NMR spectrum
of the compound (1), the signals in the 152.84–111.34 ppm range
can be attributed to the aromatic carbon atoms. The signals at
59.61 and 55.66 ppm belong to the carbon atoms of the (ACH2O)
and (AOCH3) groups, respectively. In the 1H-NMR spectrum of
the compound (2), the broad signal at 11.09 ppm may be assigned
to the phenolic OH proton. The dicarbonyl group protons were
shown at 10.25 ppm as singlet. Aromatic ring protons are at
7.60 ppm. Methoxy protons are shown at 3.82 ppm. In the
13C-NMR spectrum of the compound (1) (Fig. 1), the signals at
191.84 ppm can be attributed to the carbonyl carbon atom.
Aromatic ring carbon atoms were shown in the 157.98–
122.43 ppm range. Methoxy carbon atom is shown at 56.17 ppm.
Single crystals of the oxidized dicarbonyl compound (2) was
first time obtained and its structural characterization was per-
formed by X-ray crystallography technique. A single crystal of
dimensions 0.34 ꢂ 0.22 ꢂ 0.06 mm3 was chosen for the diffraction
experiment. Data were collected at 150(2) K on a Bruker ApexII
CCD diffractometer using Mo-Ka radiation (k = 0.71073 Å). The
structure was solved by direct methods and refined on F2 using
all the reflections [27]. All the non-hydrogen atoms were refined
using anisotropic atomic displacement parameters and hydrogen
atoms bonded to carbon and oxygen atoms were inserted at calcu-
lated positions with OAH = 0.84 Å, CAH = 0.95 Å and 0.98 Å (aro-
matic and methoxy CAH, respectively). They were refined using a
riding model with Uiso(H) = 1.2 Ueq(C) for aromatic H atoms and
Uiso(H) = 1.5 Ueq(C, O) for metoxy and phenolic H atoms. Details

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
829
Fig. 6. The electronic absorption spectra of the compounds in DMF (top) and DMSO (bottom) solutions.
of the crystal data and refinement are given in Table 1. All the bond
lengths and angles are within the normal ranges. All bond lengths
and angles in the phenyl ring have normal Csp2- Csp2 values with
small distortions. Bond lengths and angles are given in the
Supplementary file. Hydrogen bond parameters are listed in
Table 2. Perspective view of the compound (2) is shown in Fig. 2.
The compound crystallizes in orthorhombic crystal system,
Pca2(1) space group with unit cell parameters a = 32.0052(17),
b = 3.8043(2), c = 26.1897(14) Å, V = 3188.8(3) Å3 and Z = 16 (final
refinement value R = 0.0393). The asymmetric unit contains four
independent molecules differing hydrogen bonding interactions
within the structure. The molecules of the title compound (2) are
essentially planar and all structural parameters are in well agree-
ment with related structures in literature [30,31]. The C7–O1,
C8–O3, C16–O5, C17–O7, C25–O9, C26–O11, C34–O13 and C35–
O15 distances are within the range of C@O double character and
in good agreement with literature values of similar compounds
[30,31]. Independent molecules show an intra-molecular hydrogen
bond (OHꢃ ꢃ ꢃO@C) forming a S(6) hydrogen bonding motif. Four
independent molecules are linked by hydrogen bond type OHꢃ ꢃ ꢃO
and CHꢃ ꢃ ꢃO interactions (Fig. 3). Molecules 1 and 2 are connected
to molecules 3 and 4 by OHꢃ ꢃ ꢃO and O@CHꢃ ꢃ ꢃO interactions result-
ing in a R22(7) hydrogen bond motif. Molecules 3 and 4 are linked by
inter-molecular two complementary (CH(aromatic)ꢃ ꢃ ꢃO) hydrogen
bonds forming a R22(8) hydrogen bond motif (Fig. 3). Crystal pack-
ing of the compound is determined by
and O@CHꢃ ꢃ ꢃO interactions (Fig. 4 and S3).
p
–p
interactions OHꢃ ꢃ ꢃO
Derivatives of the tetrapyrrole compounds (such as porphyrin,
phtalocyanine) perform important acts in the nature, owing to
their specific absorption, emission, charge transfer and complexing

830
S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
Table 4
(a) and (b) Excitation (a) and emission (b) spectral data of the porphyrin Schiff base ligand and its transition metal complexes in the different concentrations.
kmax (nm)
Excitation
(a)
Compounds
1 ꢂ 10ꢁ3 (M)
1 ꢂ 10ꢁ4 (M)
1 ꢂ 10ꢁ5 (M)
1 ꢂ 10ꢁ6 (M)
1 ꢂ 10ꢁ7 (M)
L
451
452
453
454
454
LCu4Cl3
LPt4Cl3
LZn4Cl3
LFe3Cl4(H2O)3
LMn3(AcO)4(H2O)
385, 419
376, 420
369, 402
379, 424
395, 429
386, 420
377, 421
370, 402
380, 425
396, 430
387, 421
378, 422
371, 403
381, 426
397, 431
388, 422
379, 423
373, 404
382, 427
398, 432
389, 423
380, 424
375, 405
383, 428
399, 433
kmax (nm)
Emission
(b)
Compounds
1 ꢂ 10ꢁ3 (M)
1 ꢂ 10ꢁ4 (M)
1 ꢂ 10ꢁ5 (M)
1 ꢂ 10ꢁ6 (M)
1 ꢂ 10ꢁ7 (M)
L
690, 782
691, 783
692, 784
693, 785
694, 786
LCu4Cl3
LPt4Cl3
650, 751, 806
656, 782
652, 752, 807
657, 783
653, 753, 808
658, 784
654, 754, 809
659, 785
655, 755, 810
660, 786
LZn4Cl3
LFe3Cl4(H2O)3
LMn3(AcO)4(H2O)
650, 730, 785
675, 730, 792
773, 795
651, 730, 786
676, 731, 793
774, 796
652, 731, 787
677, 732, 794
775, 797
653, 732, 788
678, 733, 795
776, 798
654, 732, 789
679, 734, 796
777, 799
properties in consequence of their characteristic ring structure of
conjugated double bonds [32]. In their electronic absorption spec-
tra, they indicate that excessive intense bands, the so-called Soret
or B-bands in the 380–500-nm range, with molar extinction coef-
ficients of 105 Mꢁ1 cmꢁ1 extent. Furthermore, at longer wave-
lengths, in the 500–750-nm range, their spectra contain a set of
weaker, but still considerably intense Q bands, with molar extinc-
tion coefficients of 104 Mꢁ1 cmꢁ1 size. Thus, the absorption bands
of the tetrapyrrole compounds considerably overlap with the emis-
sion spectrum of the solar radiation reaching the biosphere, result-
ing in efficient tools for conversion of radiation to chemical energy.
In order to use in the synthesis of the new symmetric porphyrin
Schiff base ligand (L), 5-(4-aminophenyl)-10,15,20-triphenylpor
phyrin (TPP-NH2) was prepepared by the reduction of nitro analog
5-(4-nitrophenyl)-10,15,20-triphenylporphyrin (TPP-NO2) [33,34].
Although the TPP-NH2 compound has the asymmetric nature, syn-
thesized porphyrin Schiff base ligand 4-methoxy-2,6-bis[5-(4-imi
nophenyl)-10,15,20-triphenyl porphyrin] phenol (L) has the sym-
metric nature. Purification of the porphyrin based compounds is
considerably hard and therefore, the yields of these compounds
are very low. Crystallization technique is not suitable in the purifi-
cation of TPP, TPP-NO2 and TPP-NH2 because these compounds are
soluble in same solvents. Therefore, the column chromatography
method was used for this purpose. The ligand (L) is soluble in
the THF, DMF, DMSO, toluene, CH2Cl2, etc. On the other hand, tran-
sition metal complexes of the ligand (L) soluble in solvents CH2Cl2
and DMF, and in some coordinating solvents, such as DMSO and
THF, and low-soluble in nonpolar solvents, e.g., hexane and hep-
tane. The ligand and its metal complexes are very stable com-
pounds at room temperature without decomposing. In this type
compounds, the aggregation is a big problem. The ligand has polar
substitute groups, such as OH and OCH3. On the other hand, it also
contains nitrogen donor atoms. The ligand and its metal complexes
aggregate in noncoordinating solvents, such as heptane and hex-
ane. The polarity and the concentration of the noncoordinating sol-
vent has also an effect on the degree and type of the aggregation. In
addition, as the porphyrin Schiff base ligand has macrocyclic struc-
spectra of the Cu(II), Pt(II), Zn(II), Fe(III) and Mn(III) complexes,
as the oxygen atom of the phenolic OH group is coordinated to
the metal ions by deprotonation, therefore OAH stretching band
is absent. Moreover, the vibration of the azomethine group
(CH@N) shifts to the lower or higher regions and this situation
shows that the nitrogen atom coordinated to the metal ions [35].
When the metal ions coordinated to the nitrogen atoms of the por-
phyrin ring, the N-H bond vibration frequency of the symmetric
porphyrin Schiff base ligand (L) disappeared and the characteristic
functional groups of MAN bond formed in the 1010–990 cmꢁ1
,
which indicated the formation of metal porphyrin compounds
[36] [M@Cu(II), Pt(II), Zn(II), Fe(III) and Mn(III)]. The MAO and
MAN band vibrations were shown in the 580–550 and 450–
430 cmꢁ1 range. The FAR characterization of MACl bond vibration
(M: Cu(II), Fe(III), Pt(II) and Zn(II)) located at 355–376 cmꢁ1
.
In order to further investigate the structural property of the
ligand (L), the 1H(13C)-NMR spectra of the ligand were recorded in
the CDCl3 solution and obtained data are given in the experimental
section. In the 1HNMR spectrum of the ligand (L), the broad signal at
10.49 ppm may be assigned to the hydrogen atom of the CAOH
group. The doublets and singlet at 8.98, 8.90 and 8.80 ppm can be
attributed to the protons of the b-pyrrole rings of the new porphyrin
Schiff base ligand. The singlets at 8.64 ppm belong to the diformyl
azomethine protons. The multiplets at 8.41 ppm may be assigned
to the o-triphenyl protons. m-Phenyl and p-phenyl protons of the
porphyrin molecule were determined in the 8.28–7.82 ppm range.
Two protons of the diformyl ring were shown at 7.60 ppm as a
singlet. Methoxy protons and pyrrole internal NH proton were
indicated as singlets at 3.84 and ꢁ2.81 ppm, respectively.
In the 13C-NMR spectrum of the ligand (L), the methoxy carbon
atom was shown at 56.19 ppm. The aromatic ring carbon atoms of
the porphyrin Schiff base ligand were shown in the 112.55–
153.25 ppm range. The azomethine carbon atoms of the ligand
were shown at 162.50 ppm.
In order to determine the molecular weight of the ligand,
MALDI-TOF studies were done and obtained data for the ligand
are given in the experimental section. Mass spectrum of the
ligand is shown in Fig. 5. In the spectrum of the ligand, the peak
at m/z 1406.42 belongs to the [C98H68N10O2+4H]+ fragmentation
ion. The peak at m/z 793.73 may be assigned to the
[C53H37N6O2+3H]+ ion and this fragmentation ion is formed by loss
of the 5,10,15,20-tetraphenylporphyrinil part. In the spectrum
(Fig. 5) of the Fe(III) complex of the ligand (L), the molecular ion
peak was not shown. The signal at m/z 793.73 belongs to the
[C97H67N10O5Cl4Fe3ꢁHCN]+ ion. In addition, the fragmentation
ture, the extended
p-conjugation of the ligand may cause to the
aggregation. The ligand and its transition metal complexes aggre-
gate as depending on await in the solution for 4–5 h.
The infrared spectral data of the ligand (L) and its metal com-
plexes are given in the experimental section. In the IR spectrum
of the ligand (L), the vibrations at 3313, 3073, 1617, 1574 1490
and 1343 cmꢁ1 can be attributed to the (OH), (NH), (CH@N),
(CAC)aryl, (CH@N)pyrrole and (C@C) groups, respectively. In the

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
831
L
LCu4Cl3
(a)
(b)
LFe3Cl3
LMn3(ACO)2(H2O)
(c)
(d)
LPt4Cl3
LZn4Cl3
(f)
(e)
Fig. 7. (a)–(f) Emission and excitation spectra of the ligand and its transition metal complexes in the different concentrations.
peaks at m/z 1681.39, 1629.58, 1592.94 can be attributed to the
[C97H67N10O5Cl4Fe3ꢁ(HCN+Cl+H2O)]+, [C97H67N10O5Cl4Fe3ꢁ(HCN+
Cl2+H2O+CH3)]+ and [C97H67N10O5Cl4Fe3ꢁ(HCN+Cl3+H2O+CH3)]+
ions. The mass spectrum of the Zn(II) complex (Fig. 5) does not
show molecular ion peak. In the spectrum, the fragmentation peak
at m/z 1699.55 belongs to the [C97H63N10O2Cl3Zn3]+ ion and this
ion is formed by loss of zinc ion from the molecule. By the loss
of the second zinc ion, the peak belonging to the
[C97H63N10O2Cl2Zn]+ ion at m/z 1599.88 is shown. Similar fragmen-
tation peaks for the Cu(II), Pt(II) and Mn(III) complexes were also
shown in their mass spectra.
DMSO, CH2Cl2 and toluene solvents and obtained data are given
in the Table 3. The Uv–vis spectra of the ligand and its metal com-
plexes in DMF and DMSO solutions were shown in Fig. 6. On the
other hand, the compounds TPP, TPP-NO2 and TPP-NH2 were stud-
ied in the toluene solutions and obtained data are given in the
experimental section. As Soret band is arised from an intense per-
mitted p–
p⁄ transition, its intensity is bigger than the Q-band. On
the other hand, the Q band is a quasi-permitted one. Actually, the
Q-band is increased by a vibronic pair to the B band [37]. The com-
pounds have Soret bands in the 425–416 nm range. The Q band of
the new free Schiff base porphyrin ligand (L) is occured four com-
ponents: Qx(0, 0), Qx(1, 0), Qy(0, 0) and Qy(1, 0) which are associ-
ated with D2h symmetry. Q-bands of the porphyrin derivatives
The electronic properties of the new symmetric ligand (L) and
its transition metal complexes were investigated in the DMF,

832
S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
Table 5
The electrochemical data of a new symmetric porphyrin Schiff base ligand (L) and its transition metal complexes.
Compound
L
Concentration (M)
Scan rate (mV/s)
Epa (V)
Epc (V)
Ipa/Ipc
E1/2 (V)
DEp (V)
1 ꢂ 10ꢁ4
100
250
500
750
1000
100
250
500
750
1000
ꢁ0.65, 0.40
ꢁ0.64, 0.41
ꢁ0.63, 0.42
ꢁ0.62, 0.43
ꢁ0.60, 0.45
ꢁ0.55, 0.60
ꢁ0.54, 0.62
ꢁ0.53, 0.65
ꢁ0.52, 0.68
ꢁ0.50, 0.72
ꢁ0.64, 0.69
ꢁ0.66, 0.70
ꢁ0.68, 0.71
ꢁ0.70, 0.72
ꢁ0.73, 0.73
ꢁ0,44, 0.64
ꢁ0,43, 0.65
ꢁ0.42, 0.66
ꢁ0.40, 0.67
ꢁ0,38, 0.68
ꢁ0.29
ꢁ0.27
ꢁ0.26
ꢁ0.24
ꢁ0.23
ꢁ0.23
ꢁ0.20
ꢁ0.18
ꢁ0.16
ꢁ0.14
0.35, ꢁ0.90
0.36, ꢁ0.91
0.37, ꢁ0.92
0.38, ꢁ0.93
0.39, ꢁ0.95
0.55, ꢁ0.73
0.52, ꢁ0.76
0.50, ꢁ0.78
0.47, ꢁ0.80
0.44, ꢁ0.82
0.82, ꢁ0.58
0.83, ꢁ0.62
0.84, ꢁ0.66
0.86, ꢁ0.68
0.88, ꢁ0.70
0.65, ꢁ0.88
0.66, ꢁ0.85
0.67, ꢁ0.82
0.69, ꢁ0.79
0.71, ꢁ0.76
0.50, ꢁ0.70
0.48, ꢁ0.72
0.46, ꢁ0.75
0.45, ꢁ0.77
0.44, ꢁ0.79
0.76, ꢁ0.47
0.74, ꢁ0.48
0.73, ꢁ0.49
0.72, ꢁ0.50
0.70, ꢁ0.52
1.14
1.13
1.13
1.13
1.15
1.09
1.15
1.30
0.65
0.60
0.38
0.39
0.39
0.39
0.42
0.58
–
–
–
–
0.05
0.05
0.05
0.05
0.06
0.05
0.10
0.15
0.28
0.32
1 ꢂ 10ꢁ5
LCu4Cl3
1 ꢂ 10ꢁ4
100
250
500
750
1000
100
250
500
750
1000
1.10
1.06
1.03
1.02
1.02
0.98
0.98
0.98
0.97
0.96
ꢁ0.61
ꢁ0.64
ꢁ0.67
ꢁ0.69
ꢁ0.72
0.65
0.66
0.67
0.68
0.70
ꢁ0.06
ꢁ0.04
ꢁ0.02
ꢁ0.02
ꢁ0.03
ꢁ0.01
ꢁ0.01
ꢁ0.01
ꢁ0.02
ꢁ0.03
0.41
0.45
0.49
0.53
0.56
1 ꢂ 10ꢁ5
LPt4Cl3
LPt4Cl3
LZn4Cl3
1 ꢂ 10ꢁ4
100
250
500
750
1000
0.41
0.38
0.35
0.31
0.29
–
–
–
–
–
1 ꢂ 10ꢁ5
100
250
500
750
1000
0.49
0.42
0.36
0.32
0.27
–
–
–
–
–
0.24
0.28
0.31
0.34
0.38
1 ꢂ 10ꢁ4
100
250
500
750
1000
100
250
500
750
1000
ꢁ0.41
ꢁ0.38
ꢁ0.36
ꢁ0.33
ꢁ0.29
ꢁ0.10
ꢁ0.11
ꢁ0.12
ꢁ0.13
ꢁ0.14
0.55, ꢁ0.61
0.67
0.60
0.54
0.48
0.41
0.83
0.85
0.86
0.87
0.88
–
–
–
–
–
–
–
–
–
–
0.20
0.25
0.30
0.35
0.41
0.02
0.02
0.02
0.02
0.02
0.56, ꢁ0.63
0.58, ꢁ0.66
0.59, ꢁ0.68
0.61, ꢁ0.70
1 ꢂ 10ꢁ5
0.73, ꢁ0.12, ꢁ1.11
0.71, ꢁ0.13, ꢁ1.13
0.70, ꢁ0.14, ꢁ1.15
0.69, ꢁ0.15, ꢁ1.16
0.67, ꢁ0.16, ꢁ1.17
LFe3Cl4(H2O)3
1 ꢂ 10ꢁ4
100
250
500
750
1000
100
250
500
750
1000
ꢁ0.44, 1.08
ꢁ0.42, 1.09
ꢁ0.40, 1.10
ꢁ0.37, 1.11
ꢁ0.34, 1.12
ꢁ0.41
0.52, ꢁ0.87
0.51, ꢁ0.89
0.50, ꢁ0.91
0.49, ꢁ0.94
0.47, ꢁ0.97
0.61, ꢁ0.82
0.59, ꢁ0.84
0.56, ꢁ0.85
0.53, ꢁ0.86
0.50, ꢁ0.88
0.47, 0.12, ꢁ0.70
0.46, 0.11, ꢁ0.68
0.45, 0.10, ꢁ0.67
0.43, 0.09, ꢁ0,66
0.41, 0.08, ꢁ0.64
0.51
0.47
0.43
0.39
0.35
0.50
0.48
0.42
0.40
0.36
–
–
–
–
–
–
–
–
–
–
0.43
0.47
0.51
0.57
0.63
0.41
0.45
0.49
0.54
0.56
1 ꢂ 10ꢁ5
ꢁ0.39
ꢁ0.36
ꢁ0.34
ꢁ0.32
LMn3(AcO)4(H2O)
LMn3(AcO)4(H2O)
1 ꢂ 10ꢁ4
100
250
500
750
1000
ꢁ0.60, ꢁ0.10, 0.88
ꢁ0.61, ꢁ0.11, 0.86
ꢁ0.62, ꢁ0.12, 0.84
ꢁ0.63, ꢁ0.13, 0.83
ꢁ0.64, ꢁ0.14, 0.82
ꢁ0.23, 0.33
ꢁ0.25, 0.32
ꢁ0.28, 0.30
ꢁ0.30, 0.28
ꢁ0.32, 0.26
0.85
0.89
0.92
0.95
1.00
–
–
0.10
0.07
0.05
0.03
0.04
ꢁ0.65
ꢁ0.65
ꢁ0.64
–
–
–
0.27
0.26
1 ꢂ 10ꢁ5
100
250
500
750
1000
0.21, ꢁ0.08
0.23, ꢁ0.10
0.24, ꢁ0.12
0.25, ꢁ0.14
0.26, ꢁ0.17
1.57
1.39
1.25
1.12
1.00
0.12
0.09
0.06
0.03
0.26
All the potentials are referenced to Ag+/AgCl; where Epa and Epc are anodic and cathodic potentials, respectively.
D
Ep = EpaꢁEpc. E1/2 = 0.5 ꢂ (Epa + Epc).
(TPP, TPP-NO2 and TPP-NH2) were shown in the 650–514 nm
range. In the Uv–vis spectra of the ligand (L), new formed bands
415 nm in DMF and CH2Cl2 solutions, the band in DMSO and
toluene solutions were determined at 420 and 422 nm, respec-
tively. Q-bands of the ligand were found in the 514–649 nm range.
Q-band in the toluene solution shifted to lower shorter wave-
lengths (blue shift). In the spectra of the Mn(III), Pt(II) and Zn(II)
complexes, the ligand transitions blue shifted to 374 and 359 nm
in DMSO solution. On the other hand, Soret bands of the complexes
in the 377–379 nm range can be attributed to the p–
p⁄ transitions.
The absorption spectra of symmetric free porphyrin Schiff base
ligand (L) indicated that one major intense Soret band and four
Q-bands in DMF, DMSO, CH2Cl2 and toluene solution in the ultravi-
olet part of the spectrum. While the Soret band was shown at

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
833
L, DMF, 1x10-4
M
exhibited a blue-shift (405–409 nm range) compared to the ligand.
In the Mn(III) complex, a second Soret band was shown in the 421–
456 nm range in the all solvents. In DMF solution, Soret bands were
shown in the 414–421 nm range. Q bands were shown in the 525–
663 nm range. In the complexes, Q band numbers were deter-
mined four, three, three, three two numbers for Cu(II), Zn(II),
Pt(II), Fe(III) and Mn(III), respectively. In toluene solutions, the
ligand
p–
p⁄ transitions at 379 nm shifted to shorter wavelength
values (blue shift) at 375 and 364 nm for Cu(II) and Z(II) com-
plexes, respectively. On the other hand, this transition showing a
red-shift was observed at 381, 382 and 393 nm for Pt(II), Fe(III)
and Mn(III), respectively. Soret band at 411 nm in the spectrum
of the ligand shifted to shorter and longer wavelengths compare
to the free ligand. Q band number for the Cu(II) and Zn(II) com-
plexes was determined only one number at 549 and 548 nm,
respectively. While the Pt(II) and Fe(III) complexes have three Q
band numbers in 527–601 nm range, the Mn(III) complex has
two bands at 529 and 567 nm. In CH2Cl2 solution, the Soret band
of the ligand (L) was shown at 412 nm. While the Cu(II), Zn(II)
and Pt(II) complexes have same band at 410, 411 and 413 nm,
respectively, Soret bands of the Fe(III) and Mn(III) complexes were
observed at 451, 422 and 421 nm, respectively. On the other hand,
Q-bands of the ligand (L) were shown in the 525–660 nm range. In
the Cu(II) and Zn(II) complexes, Q-bands were seen at 562 and
561 nm as one piece, respectively. The Fe(III) complex has two
Q-bands at 562 and 663 nm. Moreover, the Mn(III) and Pt(II) com-
plexes have three Q-bands in the 519–600 and 528–601 nm range,
respectively. As a result, decreasing of the Q-band numbers shows
that the porphyrin inner nitrogen atoms coordinated to the metal
ions.
LCu4Cl3, DMF, 1x10-4
M
LPt4Cl3, DMF, 1x10-4
Excitation and emission spectra of the new symmetric por-
phyrin Schiff base ligand (L) and its transition metal complexes
LZn4Cl3, DMF, 1x10-4
M
were investigated in the different concentrations (1 ꢂ 10ꢁ3
–
1 ꢂ 10ꢁ7 M range) and obtained data are given in Table 4. The spec-
tra of the compounds are shown in Figs. 7a–f. In the excitation
spectrum of the free ligand (L), the intensive band in the 451–
454 nm range in the different concentrations can be attributed to
the Soret band which accounts for the S0 ? S2 transitions of the
Schiff base porphyrin ligand. The emission spectrum of the ligand
(L) shows two peaks, one strong peak at 690 nm and a weaker peak
at 782 nm in the 1 ꢂ 10ꢁ3 M concentration. The former peak corre-
sponds to the Qx(0–0) transition and the latter one to the Qx(0–1)
transition. By changing the concentration of the solution from
1 ꢂ 10ꢁ3 to 1 ꢂ 10ꢁ7 M, the intensity of the emission peaks
decreases and shifts to the longer wavenumbers. In the excitation
spectra of the Cu(II) complex, a new band in the 385–389 nm range
was determined. The Soret band was shifted to the lower region (in
the 419–423 nm range) in the different concentrations. Three
emission bands of the Cu(II) complex were determined in the
650–810 nm range. The band at ꢅ808 nm in Cu(II) complex was
not observed in the emission spectrum of the ligand (L). The emis-
sion and excitation spectra of the Fe(III) and Zn(II) complexes have
LFe3Cl4(H2O)3, DMF, 1x10-4
M
LMn3(AcO)4(H2O), DMF, 1x10-4
M
also similar properties to the Cu(II) complex in the 1 ꢂ 10ꢁ3
–
1 ꢂ 10ꢁ7 M concentration range. But, the emission and excitation
spectra of the Pt(II) and Mn(III) complexes are different than other
complexes. In the Mn(III) complex, two excitation bands were
shown in the 395–433 nm range. On the other hand, two emission
bands were also shown but, these bands were shifted to the longer
wavenumbers than the ligand in the 773–799 nm range. In the
Pt(II) complex, the excitation spectra were shown two bands in
the 376–424 nm range in the different concentrations. The emis-
sion spectra of the Pt(II) complex indicate two peaks in the 656–
786 nm range. The absorption intensities of the emission and exci-
tation spectra of the ligand (L) and its metal complexes were
decreased depending upon by the changing of the solution
concentration.
Fig. 8. CV curves of the novel symmetric porphyrin Schiff base ligand (L) and its
transition metal complexes at different scan rates in DMF solution.
Electrochemical properties of the porphyrin Schiff base ligand
and its metal complexes were investigated in DMF-0.1 M

834
S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
a) LPt4Cl3
b) LFe3Cl4(H2O)3
Fig. 9. (a) and (b) Thermal curves of the LPt4Cl3 (a) and LFe3Cl4(H2O)3 (b) complexes in the 20–1000 °C temperature range.
line is TG,
line is DTA,
line
is DTG.
Bu4NBF4 as supporting electrolyte at 293 K. All potentials quoted
V (Epa/Epc) potential. In the 1 ꢂ 10ꢁ5 M solution, while the process
at 0.60/0.55 V redox couple are reversible, the process at
062/0.52 V are quasi-reversible at the 250 mV sꢁ1 scan rate. At
the other scan rates, the ligand shows the irreversible redox pro-
cesses. In the reversible redox processes, the ligand shows the
refer to measurements run at
a scan rates in the 100–
1000 mV sꢁ1 range and against an internal ferrocene–ferrocenium
standard, unless otherwise stated. The electrochemical studies
were studied in the 1 ꢂ 10ꢁ4 and 1 ꢂ 10ꢁ5
M solutions and
obtained data are given in Table 5. The selective voltammograms
of the ligand L (a) and its Cu(II) (b), Pt(II) (c), Zn(II) (d), Fe(III) (e)
and Mn(III) (f) complexes are shown in Fig. 8. In the cv curves of
the ligand (L), all redox processes, except at 1000 mV sꢁ1 scan rate,
in the 1 ꢂ 10ꢁ4 M solutions are reversible. These redox couples are
at 0.40/0.35, 0.41/0.36, 0.42/0.37 and 0.43/0.38 V at the 100, 250,
500 and 750 mV sꢁ1, respectively. At the 1000 mV sꢁ1 scan rate,
the ligand shows the quasi-reversible redox process at 0.45/0.39
amin-imine transformation [38]. In the 1 ꢂ 10ꢁ4 and 1 ꢂ 10ꢁ5
M
concentrations of the Cu(II) complex, the redox processes at all
scan rates show the reversible in the ꢁ0.73 to 0.88 V range. The
Pt(II) complex in the 1 ꢂ 10ꢁ4 M solution has one anodic and two
cathodic peak potentials in the ꢁ0.23–(ꢁ)0.29 V range and ꢁ0.79
to 0.50 V range, respectively. Moreover, in the 1 ꢂ 10ꢁ5 M solution,
the Pt(II) complex has also similar electrochemical properties. All
redox processes are irreversible in the 100–1000 mV sꢁ1 range

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
835
Table 6
IC50 values and catalytic rate for SOD activity of the complexes.
Compounds
IC50
(l
M) WST-1 assay
kcat (Mꢁ1 sꢁ1
)
Method
Refs.
LCu4Cl3
0.96
0.73
0.62
1.19
1.03
–
–
–
–
–
1.67 ꢂ 106
2.19 ꢂ 106
2.58 ꢂ 106
1.35 ꢂ 106
1.56 ꢂ 106
1.6 ꢂ 109
1.3 ꢂ 106
3.4 ꢂ 104
8 ꢂ 105
Indirect
Indirect
Indirect
Indirect
Indirect
Stopped-flow
Indirect
This work
This work
This work
This work
This work
[4]
[5]
[6]
[7]
[8]
LMn3(AcO)4(H2O)
LFe3Cl4(H2O)3
LPt4Cl3
LZn4Cl3
M40404
Mn(ClO4)2
Mn(ClO4)2 + EDTA
MnSalen(EUK8)
M40403
MnSOD
CuZnSOD (bovine)
Indirect
Stopped-flow
Stopped-flow
indirect
1.6 ꢂ 107
5.2 ꢂ 108
2 ꢂ 109
–
[9]
[10]
Pulse radiolysis
M40403: [manganese(II)dichloro{(4R,9R,14R,19R)-3,10,13,20,26-pentaazatetracyclo[20.3.1.0.4,9014,19]hexacosa-1(26),-22(23),24-triene}],M40404:[manganese(II)dichloro
{2S,21S-dimethyl-(4R,9R,14R,19R)-3,10,13,20,26-pentaazatetracyclo[20.3.1.0.4,9014,19]hexa-cosa-1(26),22(23),24-triene}].
scan rates. The electrochemical properties of the Zn(II) complex
1 ꢂ 10ꢁ4 M solution similar to the Pt(II) complex and its redox
behavior is irreversible at all potentials. On the other hand,
1 ꢂ 10ꢁ5 M solution, the Zn(II) complex has quasi-reversible redox
properties in the ꢁ0.16–(ꢁ)0.14 V range. The Fe(III) complex
shows the irreversible redox properties in both concentrations
and scan rates. The Mn(III) complex in the 1 ꢂ 10ꢁ4 M solution
shows three anodic and cathodic peaks. At the 500, 750 and
1000 mV sꢁ1 scan rates, the complex has reversible redox pro-
cesses in the ꢁ0.67–(ꢁ)0.62 V range. Furthermore, at the 100 and
Fig. 10. Dismutation of superoxide by metal complexes.
250 mV sꢁ1 scan rates, the complex shows the quasi reversible
behavior at the ꢁ0.60/ꢁ0.70 and ꢁ0.61/ꢁ0.68 redox couples. In
the 1 ꢂ 10ꢁ5 M solution, the Mn(III) complex has reversible redox
complexes in this study exhibit considerable SOD activity, as com-
pared with native Mn-SOD and some complexes in the literature
process at 0.26 V potential and 1000 mV sꢁ1 scan rates. But, at the
another scan rates, the complex has irreversible redox behavior.
listed in Table 6. SOD enzymes and mimic complexes catalyze the
Thermal analysis studies of the symmetric porphyrin Schiff base
dismutation of superoxide and hydrogen peroxide in a ping-pong
ligand (L) and its transition metal complexes were investigated in
mechanism where the metal cycles between oxidized and reduced
an air atmosphere at a heating rate of 10 °C/min. The TG and DTA
forms (Fig. 10). The complexes showed SOD activity with rate con-
stants in the range of 2.58 ꢂ 106–1.35 ꢂ 106 Mꢁ1 sꢁ1. The Fe(III)
curves of the Pt(II) complex of the ligand (L) are shown in
Fig. 9a and b. In the TG curve of the ligand (L), decomposition pro-
cesses are taken place in four steps. In the first step, in the 120–
complex showed the greatest SOD activity with an IC50 value of
0.62
l
M which gives a calculated Kcat value of 2.58 ꢂ 106 Mꢁ1 sꢁ1
.
180 °C temperature range, the ligand loses 2.21% of its mass. This
mass loss corresponds to the –CH3 group of the ligand. In the
240–340 °C temperature range, second mass loss occurs as about
6.48% of total mass. This mass comes from loss of the C6H2O group.
In the 340–500 °C temperature range, 13.75% of the mass was lost
in third step. Mass loss in this step corresponds to the lose of the
diformyl imine ring (C9H8N2O2). In fourth step, residual mass
was lost up to 700 °C. In DTA curve of the ligand (L), the mass lost
in the 120–700 °C temperature range were shown as endothermic
peaks. It is shown that the ligand (L) has significant thermal stabil-
ity at high temperatures. Decomposition processes of the metal
complexes of the ligand (L) start in the 150–250 °C temperature
range. The mass loss in this temperature range corresponds to
the coordinated acetate, chloride or water ions or molecules [39].
In DTA curves of the complexes, this process is shown as the
endothermic peaks. In the first step, about 3–5% of the mass has
been lost. In the second step, the complexes continued to decom-
pose in the 350–600 °C temperature range. In this temperature
range, the big exothermic peaks corresponds to the loss of por-
phyrin rings. In the last step, the metal oxides occured.
Direct comparisons of SOD activity of complexes with other related
complexes are somewhat complicated due to diverse methodology
used for the formation of superoxide. The results for SOD activity of
the macrocyclic Mn(III) complex M40404 have been found to show
catalytic rates that exceed that of the natural Mn-SOD enzyme itself
and this complex is the most active SOD mimic to date [41]. Simple
manganese perchlorate has a high rate of catalytic activity [42].
However, addition of EDTA reduces the catalytic rate dramatically
[43]. The manganese salen complex (EUK8) has been found to show
a slower reaction rate than manganese perchlorate [44]. The SOD
activity results that have been obtained for the synthesised por-
phyrin complexes in this research show higher activity to those
of manganese salen complex (EUK8) and manganese perchlorate.
On the other hand, the reaction rates are much less than the rates
of M40404, M40403 [45], natural Mn-SOD [46] and Cu-ZnSOD
(bovine) [47].
3.2. DNA binding studies
In general, the ligands and their metal complexes with aromatic
moieties which bind to fish sperm double strain deoxyribonucleic
acid (FSdsDNA) through intercalation usually results in hypochro-
mism and bathochromism, due to the stacking interaction between
aromatic chromophore of the compounds and the base pairs of
FSdsDNA. In addition, The porphyrins and their metal complexes
are known to bind to DNA via both covalent and/or noncovalent
3.1. The superoxide dismutase (SOD) activity studies
The superoxide dismutase (SOD) activity of porphyrine based
metal complexes were evaluated by a modified indirect chemical
method [40]. The SOD test results indicated that the metal

836
S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
Fig. 11. UV spectra of the L 1/10: DMSO/MeOH ([L] = 1 ꢂ 10ꢁ6 M) solution in the presence of FSdsDNA at increasing amounts. The arrows show the changes upon increasing
amounts of FSdsDNA. Insets: plot of [DNA/ea
ꢁ ef] vs. [DNA].
Fig. 12. UV spectra of the complex LFe3Cl4(H2O)3 1/10: DMSO/MeOH ([LFe3Cl4(H2O)3] = 2 ꢂ 10ꢁ6 M) solution in the presence of FSdsDNA at increasing amounts. The arrows
show the changes upon increasing amounts of FSdsDNA. Insets: plot of [DNA/ea
ꢁ ef] vs. [DNA].
interactions [48]. In covalent binding the labile porphyrin of the
complexes is replaced by a nitrogen base of DNA such as guanine
N7. Moreover, the noncovalent DNA interactions include intercala-
tive, electrostatic and groove (surface) binding of compounds along
outside of DNA helix, along major or minor groove. It has been
reported that FSdsDNA can provide three distinctive binding sites
for all compounds; namely, groove binding, electrostatic binding
to phosphate group and intercalation [49]. This behavior is of great
importance with regard to the relevant biological role of por-
phyrins and metallo porphyrins in the body. The interaction can
be studied with UV spectroscopy in order to investigate the
Table 7
The intrinsic binding constants (Kb) of compounds with DNA.
Compounds
Kb
L
5 ꢂ 106
LCu4Cl3
LZn4Cl3
LMn3(AcO)4(H2O)
LFe3Cl4(H2O)3
LPt4Cl3
1.5 ꢂ 106
2 ꢂ 106
1.4 ꢂ 106
8.8 ꢂ 106
1 ꢂ 105

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838
837
metalloporphyrin is higher than the EB binding affinity for DNA
(Kb = 1.23 0.07 ꢂ 105) suggesting that intercalative interaction
may affect EB displacement [55]. In addition, a distinct isosbestic
point appears at about 430 nm upon addition of FSdsDNA. The
behavior of complexes upon addition of FSdsDNA is quite similar.
Typical UV spectrum of the LFe3Cl4(H2O)3 complex has been given
in Fig. 12.
possible binding modes to FSdsDNA. The changes observed in the
UV spectra upon titration may give the evidence of the existing
interaction mode, since a hypochromism, due to
p–
p⁄ stacking
interactions, may appear in the case of the intercalative binding
mode, while red-shift (bathochromism) may be observed when
the DNA duplex is stabilized [50]. In UV titration experiments,
the spectra of FSdsDNA in the presence of each compounds have
been recorded for a constant compounds concentration in diverse
[ligand or complex]/[FSdsDNA] mixing ratios (r).
Fig. 11 shows the spectral changes occurred in the methanol
solution of 1 ꢂ 10ꢁ6 M L (kmax = 416.12 nm, Amax = 0.48 A) upon
addition of increasing amounts of FSdsDNA. Even though no appre-
ciable change in the position of the intraligand band of L and its
metal complexes are observed by addition of different initial con-
centration of FSdsDNA (initial concentration and UV–Vis results for
4. Conclusion
In this study, we obtained the compounds 4-methoxy-2,6-bis(h
ydroxymethyl)phenol (1) and 4-methoxy-2,6-diformylphenol (2)
as starting materials. We, first time, investigated structural charac-
terization of the 4-methoxy-2,6-diformylphenol compound by
X-ray crystallography method. Then, we prepared a new symmet-
ric porphyrin Schiff base ligand (L) and its transition metal com-
plexes. The electrochemical properties of the new ligand (L) and
its metal complexes were investigated and the ligand was showed
the reversible redox processes in both different concentrations and
scan rates. The compounds exhibited very interesting pholumines-
cence properties.
The SOD test results indicated that the metal complexes in this
study exhibit considerable SOD activity, as compared with native
Mn-SOD and some complexes reported in literature. SOD enzymes
and mimic complexes catalyze the dismutation of superoxide and
hydrogen peroxide in a ping-pong mechanism where the metal
cycles between oxidized and reduced forms. The highest value of
Kb obtained from the LFe3Cl4(H2O)3 complex and the ligand L and
its complexes LZn4Cl3, LCu4Cl3, LMn3(AcO)4(H2O) and LPt4Cl3,
respectively, suggest a strong binding of complexes to FSdsDNA.
Indeed, it is much higher than Kb calculated for L, indicating that
the coordination of porphrin ligand to M(II/III) ion enhance signif-
icantly the ability to bind to FSdsDNA.
metal complexes; 1 ꢂ 10ꢁ6
M for LCu4Cl3: kmax = 414.24 nm,
Amax = 0.5 A, 3 ꢂ 10ꢁ6
M
for LZn4Cl3: kmax = 422.90 nm, Amax
=
=
0.36 A, 2 ꢂ 10ꢁ6 M for LMn3(AcO)4(H2O): kmax = 415.66 nm, Amax
0.44 A,
2 ꢂ 10ꢁ6
M
for
LFe3Cl4(H2O)3:
kmax = 416.00 nm,
Amax = 0.5 A) and 2 ꢂ 10ꢁ6
M
for LPt4Cl3: kmax = 416.00 nm,
Amax = 0.5 A are observed by addition of different initial concentra-
tion of FSdsDNA (2–6 ppm for L; kA = 0.33–0.21
kmax = 8.03–7.19 nm, 0.25–3 ppm for LCu4Cl3; A = 0.17–0.11 A
and kmax = 8.34–7.84 nm, 0.25–4 ppm for LZn4Cl3; A = 0.18–
0.12 A and kmax = 8.85–7.86 nm, 0.25–3 ppm for LMn3(AcO)4
(H2O); kA = 0.44–0.28 A and kmax = 7.40–6.93 nm, 0.25–3 ppm
for LFe3Cl4(H2O)3; kA = 0.3–0.15 A and kmax = 10.23–6.29 nm
and 0.25–3 ppm for LPt4Cl3; kA = 0.2–0.12 A and kmax = 10.01–
A
and
D
D
D
D
D
D
D
D
D
D
D
4.78 nm) is decreased in the presence of DNA. But increasing of
the concentration of DNA, the absorbance value is increased for L
over again. In general, hyperchromism and hypochromism are
the spectral features of DNA concerning changes of its double helix
structure; hyperchromism means the breakage of the secondary
structure of DNA and hypochromism shows that binding of com-
plex to DNA can be due electrostatic effect or intercalation which
may stabilize the DNA duplex [51]. Additionally, the existence of
a red-shift is indicative of stabilization of DNA duplex [52]. On
the other hand, addition of FSdsDNA to L results in slight hypo-
chromism of the band at kmax = 416.12 nm, which is accompanied
by a red-shift of 7.19 nm (up to 423.31 nm). These spectral changes
may be evidence of a possible intercalation, which could subse-
quently stabilize the DNA duplex [53]. For all complexes, the band
centered at 414.24, 422.90, 415.66, 415.99 and 415.53 nm exhibits
a less pronounced chromism of 78% for copper(II), 50% for zinc(II),
63% for Mn(III), 54% for Fe(III) and 66.7% for platinium (II) com-
plexes upon addition of FSdsDNA accompanied by a red-shift.
The binding strength of the L and its complexes with FSdsDNA is
mirrored in the intrinsic binding constant Kb, which represents
the binding constant per DNA base pair and can be obtained by
monitoring the changes in the absorbance at different wavelengths
(for all compounds) with increasing concentrations of FSdsDNA,
according to the following equation (Eq. (1)) [54]
Acknowledgments
We are grateful to The Scientific & Technological Research
Council of Turkey (TUBITAK) (Project number: 113Z907) for the
support of this research. The authors are also grateful to the
Department of Chemistry, Loughborough University for X-ray data
collection.
Appendix A. Supplementary data
CCDC number 1050229 contains the supplementary crystallo-
graphic data for (A) and (B), respectively. Bond lengths and angles
of the compounds were given in Supplementary Information.
These data can be obtained free of charge via www.ccdc.cam.ac.
uk/data_request/cif, by e-mailing data_request@ccdc.cam.ac.uk,
or by contacting The Cambridge Crystallographic Data Centre 12
Union Road Cambridge CB2 1EZ, UK. Fax: +44(0)1223-336033.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2015.07.044.
½DNAꢄ=ðea
ꢁ
ef Þ ¼ ½DNAꢄ=ðeb
ꢁ
ef Þ þ 1=Kbðea
ꢁ
ef
Þ
ð1Þ
where a = Aobs/[Complex],
e
ea = extinction coefficient for the free
complex and b = extinction coefficient for compound in the fully
e
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