Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838

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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

Article history: Received 3 May 2015 Received in revised form 15 June 2015 Accepted 7 July 2015 Available online 8 July 2015 Keywords: Porphyrin-Schiff base Superoxide dismutase activity DNA-binding Spectroscopy

a b s t r a c t 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 porphyrin 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 compounds were investigated. Ó 2015 Elsevier B.V. All rights reserved.

1. Introduction 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 ⇑ Corresponding author. E-mail address: [email protected] (M. Tümer). http://dx.doi.org/10.1016/j.saa.2015.07.044 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.

Schiff bases and their transition metal complexes [4–10] which report the X-ray structural characterization, antioxidant, anticancer, 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 complexes) 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 substituent 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 properties and considerable stability, porphyrins and

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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 compounds 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 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].

Superoxide dismutase (SOD), catalase and glutathione peroxidase are significant scavengers of the reactive oxygen intermediates (ROI). Of these enzymes, manganese-SOD (Mn-SOD), which is embedded in the mitochondrial matrices, is stimulated by cytotoxic and cell-spoil stimuli, and protects the cells from generated superoxide (O 2 ) [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 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 characterized. 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

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Fig. 1. The 1H NMR and

13

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C 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. 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

932. Infrared spectra were obtained using KBr disk (4000– 400 cm1) 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.

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Table 1 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 a (Å) b (Å) c (Å) a (°) b (°) c (°) Volume (Å3) Z Abs. coeff. (mm1) Refl. collected Completeness to h = 27.16° Ind. Refl. [Rint] R1, wR2 [I > 2r (I)] R1, wR2 (all data) CCDC number

2 C9H8O4 180.15 0.34  0.22  0.06 Colorless Orthorhombic Pca2(1) 32.0052(17) 3.8043(2) 26.1897(14) 90 90 90 3188.8(3) 16 0.120 27,904 100% 7032 [0.0404] 0.0393, 0.0893 0.0526, 0.0981 1,050,229

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  103–1.0  107 mol L1) 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. A stock solution of concentrations of 1  103 M and 1  104 M of the porphyrin-Schiff base compound was prepared in DMF solution for electrochemical studies. Cyclic voltammograms were recorded on a Iviumstat Electrochemical workstation equipped with a low current module (BAS PA-1) recorder. The electrochemical 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 performed at room temperature in an undivided cell (BAS model C-3 cell stand) with a platinum counter electrode and an Ag+/AgCl Table 2 Hydrogen bonds for 4-methoxy-2,6-diformylphenol (2) [Å and °]. D–H  A

d(D–H)

d(H  A)

d(D  A)

200 °C. dH (CDCl3)/ppm: 8.85 (s, 8H, pyr-CH), 8.29 (m, 8H, 4  C6H5), 7.77 (m, 12H, 4  C6H5), 2.71 (s, 2H, pyrrole internal NH). FTIR (KBr, m, cm1): 3311 (NH), 3021 (aryl CAH), 1594 (CH@N)porphyrin, 1553 (CAC)aryl, 1347 (C@C). UV–Vis [Toluene,

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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), emax (M1 cm1)]: 416 nm (4.30  105), 515 (1.30  104), 550 (4.23  104), 592 (1.71  104), 648 (0.55  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 temperature, the reaction was poured into water (100 mL) and extracted with dichloromethane (6  25 mL). The organic layer was washed with saturated aqueous NaHCO3, water, and then dried over magnesium 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. 1 H-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  C6H5), 7.75 (m, 9H, 3  C6H5), 2.72 (s, 2H, pyrrole internal NH). FTIR (KBr, m, cm1): 3315 (NH), 2988 (CAH), 1594 (CH@N)porphyrin, 1557 (CAC)aryl, 1515, 1344 (NO2), 1344 (C@C). UV– Vis [Toluene, kmax(nm), emax (M1 cm1)]: 418 (4.10  105), 514 (3.11  104), 549 (0.95  104), 589 (0.88  104), 646 (0.75  104).

nitrogen. SnCl22H2O (0.28 g, 1.2 mmol) was added to the solution, and the reaction was heated to 65 °C for 4 h. The porphyrin solution 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 magnesium sulfate. The organic phase was concentrated under pressure 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-triphenyl), 7.09 (d, 2H, 4-aminophenyl), 4.04 (s, 2H, amino), 2.72 (s, 2H, pyrrole internal NH). FTIR (KBr, m, cm1): 3318 (NH), 2973 (CAH), 1615 (CH@N)pyrrole, 1506 (CAC)aryl, 1349 (C@C). UV–Vis [Toluene, kmax(nm), emax (M1 cm1)]: 425(3.34  104), 524(0.40  104), 560(0.30  104), 587(0.20  104), 650(0.10  104). 2.7. Preparation of the 4-methoxy-2,6-bis[5-(4-iminophenyl)10,15,20-triphenyl porphyrin] phenol (L) The porphyrin Schiff base ligand was synthesized as follows: TTPNH2 (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) 5-(4-Nitrophenyl)-10,15,20-triphenylporphyrin (0.26 g, 0.39 mmol) was dissolved in 10 mL of concentrated hydrochloric acid under

of dry toluene containing 4 Å A molecular sieves. The resulting solution 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

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Fig. 4. Packing diagram of 2,6-diformyl-4-metoxyphenol. Hydrogen bonds are shown as dashed lines.

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). 1 HNMR (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, (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, 148.88, 153.25, 162.50. FTIR (KBr, m, cm1): 3313 (OH), 3075 (NH), 2950 (CH)aliphatic, 1617 (CH@N), 1574 (CAC)aryl, 1490 (CH@N)pyrrole, 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)-10,15,20triphenylporphyrin]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 CuCl22H2O; 0.542 for FeCl36H2O; 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 reaction 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;

H, 3.45; N, 8.01%. FTIR (KBr, m, cm1): 3005 (CAH)aromatic, 2950 (CAH)aliphatic, 1593 (CH@N)imine, 1538 (CAC)aromatic, 1342 (CAO)phenolic, 996 (Cu-N)porphyrin, 580 (CuAO), 450 (CuAN). MALDITOF-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, cm1): 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). MALDITOF-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, cm1): 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). MALDITOF-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, m, cm1): 3058 (CAH)aromatic, 2920 (CAH)aliphatic, 1602 (CH@N)imine, 1539 (CAC)aromatic, 1336 (CAO)phenolic, 1001 (Fe-N)porphyrin, 550 (FeAO), 445 (FeAN). MALDI-TOF-MS, (m/z): Calculated: 1761.98; found: 1734.47 [C97H67N10O5Cl4Fe3HCN]+, 1681.39 [C97H67N10O5Cl4Fe3(HCN+ Cl+H2O)]+, 1629.58 [C97H67N10O5Cl4Fe3(HCN+Cl2+H2O+CH3)]+, 1592.94 [C97H67N10O5Cl4Fe3(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, m, cm1): 3306 (H2O), 3020 (CAH)aromatic, 2922 (CAH)aliphatic, 1710 (C@O)acetic acid, 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) – (2CH3COO+H2O)]+. 2.9. Superoxide dismutase (SOD) activity studies of the transition metal complexes 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 aerobically xanthine-xanthine oxidase enzyme system. The O2 produced reacts with 2-(4-iodophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, 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 O 2 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 complex competes with the WST-1 to scavenge the O 2 . 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 activity [28]. The IC50 values obtained are dependent upon the indicator used and concentration of the indicator [WST] can be used to calculate rate constant Kcat using the calculation proposed by McCord and Fridovich [29] shown in the following equation:

K cat ¼ K WST-1  ½WST-1=IC50

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838

L

LFe3Cl4(H2O)3

LZn4Cl3

Fig. 5. MALDI-TOFF spectra of the ligand (L) and its Fe(III) and Zn(II) complexes.

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where; Kcat: rate constant KWST-1: rate of WST-1 reduction: 3.7  104 mol1 L s1 (pH = 8), [WST-1]: concentration of WST-1.

375(0.84  104), 421(1.05  104), 519(0.18  104), 563(0.17  104), 600(0.15  104)

378(0.30  104), 422(0.54  104), 451(0.52  104), 562(0.24  104), 663(0.16  104)

376(0.74  104), 413(0.74  104), 528(0.19  104), 563(0.18  104), 601(0.16  104)

411(1.38  104), 561(0.20  104)

410(1.64  104), 562(0.21  104)

CH2Cl2

378(0.17  104), 412(1.94  104), 525(0.25  104), 562(0.21  104), 600(0.19  104), 660(0.17  104)

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 M1 cm1.

393(0.14  104), 406(0.79  104), 451(0.42  104), 529(0.16  104), 567(0.14  104) 381(0.20  104), 419(0.68  104), 449(0.39  104), 529(0.10  104), 563(0.10  104) 359(0.28  104), 409(1.59  104), 456(0.46  104), 536(0.28  104), 569(0.21  104) LMn3(AcO)4(H2O)3

382(0.24  104), 409(1.74  104), 527(0.27  104), 566(0.26  104), 597(0.20  104) 379(0.20  104), 421(0.90  104), 530(0.25  104), 565(0.20  104), 610(0.09  104) 379(0.34  104), 405(1.20  104), 569(0.26  104), 658(0.06  104) LFe3Cl3(H2O)3

381(0.12  104), 416(0.94  104), 532(0.14  104), 569(0.13  104), 601(0.09  104) 380(0.14  104), 415(1.30  104), 528(0.24  104), 562(0.22  104), 603(0.20  104) 374(0.16  104), 407(1.64  104), 531(0.26  104), 562(0.25  104), 600(0.21  104) LPt4Cl3

364(0.04  104), 414(0.60  104), 548(0.13  104) 379(0.19  104), 417(0.80  104), 525(0.26  104), 560(0.23  104), 602(0.15  104) 383(0.09  104), 406(1.74  104), 528(0.26  104), 563(0.25  104), 602(0.19  104) LZn4Cl3

375(0.15  104), 413(1.40  104), 549(0.25  104), 648(0.06  104) 379(0.19  104), 414(1.32  104), 527(0.28  104), 563(0.26  104), 602(0.24  104), 663(0.19  104) 379(0.24  104), 405(1.34  104), 560(0.26  104), 601(0.23  104), 660(0.19  104) LCu4Cl3

379(0.18  104), 411(1.90  104), 524(0.28  104), 561(0.26  104), 602(0.20  104), 661(0.18  104)

Toluene DMF

378(0.21  104), 412(1.84  104), 525(0.31  104), 562(0.29  104), 600(0.27  104), 660(0.20  104)

DMSO

377(0.26  104), 413(1.84  104), 525(0.30  104), 562(0.27  104), 601(0.25  104), 663(0.19  104) L

kmax (emax)

Table 3 UV–vis absorption spectral data of the symmetric porphyrin Schiff base ligand (L) and metal complexes in the different solvents.

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 activated MnO2 and then the 4-methoxy-2,6-diformylphenol (2) carbonyl 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 spectrum of the compound (1), the vibration bands at 3312, 2939, 1611 and 1480 cm1 can be attributed to the (OH), (CAH)alph, and (aryl CAC) groups, respectively. In the compound (2), the hydroxymethyl vibration at 3312 cm1 was disappeared and instead of this band, the carbonyl group band (C@O) at 1673 cm1 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 protons. The very strong singlets at 4.52 and 3.66 ppm can be attributed 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 13 C-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 performed by X-ray crystallography technique. A single crystal of dimensions 0.34  0.22  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 calculated positions with OAH = 0.84 Å, CAH = 0.95 Å and 0.98 Å (aromatic 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 agreement 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 (OH  O@C) forming a S(6) hydrogen bonding motif. Four independent molecules are linked by hydrogen bond type OH  O and CH  O interactions (Fig. 3). Molecules 1 and 2 are connected to molecules 3 and 4 by OH  O and O@CH  O interactions resulting in a R22(7) hydrogen bond motif. Molecules 3 and 4 are linked by inter-molecular two complementary (CH(aromatic)  O) hydrogen bonds forming a R22(8) hydrogen bond motif (Fig. 3). Crystal packing of the compound is determined by p–p interactions OH  O and O@CH  O interactions (Fig. 4 and S3). 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

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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  103 (M)

1  104 (M)

1  105 (M)

1  106 (M)

1  107 (M)

L LCu4Cl3 LPt4Cl3 LZn4Cl3 LFe3Cl4(H2O)3 LMn3(AcO)4(H2O)

451 385, 376, 369, 379, 395,

452 386, 377, 370, 380, 396,

453 387, 378, 371, 381, 397,

454 388, 379, 373, 382, 398,

454 389, 380, 375, 383, 399,

419 420 402 424 429

420 421 402 425 430

421 422 403 426 431

422 423 404 427 432

423 424 405 428 433

kmax (nm)

Emission

(b) Compounds

1  103 (M)

1  104 (M)

1  105 (M)

1  106 (M)

1  107 (M)

L LCu4Cl3 LPt4Cl3 LZn4Cl3 LFe3Cl4(H2O)3 LMn3(AcO)4(H2O)

690, 650, 656, 650, 675, 773,

691, 652, 657, 651, 676, 774,

692, 653, 658, 652, 677, 775,

693, 654, 659, 653, 678, 776,

694, 655, 660, 654, 679, 777,

782 751, 806 782 730, 785 730, 792 795

783 752, 807 783 730, 786 731, 793 796

properties in consequence of their characteristic ring structure of conjugated double bonds [32]. In their electronic absorption spectra, they indicate that excessive intense bands, the so-called Soret or B-bands in the 380–500-nm range, with molar extinction coefficients of 105 M1 cm1 extent. Furthermore, at longer wavelengths, in the 500–750-nm range, their spectra contain a set of weaker, but still considerably intense Q bands, with molar extinction coefficients of 104 M1 cm1 size. Thus, the absorption bands of the tetrapyrrole compounds considerably overlap with the emission spectrum of the solar radiation reaching the biosphere, resulting 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, synthesized porphyrin Schiff base ligand 4-methoxy-2,6-bis[5-(4-imi nophenyl)-10,15,20-triphenyl porphyrin] phenol (L) has the symmetric 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 purification 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, transition 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 heptane. The ligand and its metal complexes are very stable compounds 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 hexane. The polarity and the concentration of the noncoordinating solvent has also an effect on the degree and type of the aggregation. In addition, as the porphyrin Schiff base ligand has macrocyclic structure, the extended p-conjugation of the ligand may cause to the aggregation. The ligand and its transition metal complexes aggregate as depending on await in the solution for 4–5 h. The infrared spectral data of the ligand (L) and its metal complexes are given in the experimental section. In the IR spectrum of the ligand (L), the vibrations at 3313, 3073, 1617, 1574 1490 and 1343 cm1 can be attributed to the (OH), (NH), (CH@N), (CAC)aryl, (CH@N)pyrrole and (C@C) groups, respectively. In the

784 753, 808 784 731, 787 732, 794 797

785 754, 809 785 732, 788 733, 795 798

786 755, 810 786 732, 789 734, 796 799

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 porphyrin 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 cm1, 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 cm1 range. The FAR characterization of MACl bond vibration (M: Cu(II), Fe(III), Pt(II) and Zn(II)) located at 355–376 cm1. 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 [C97H67N10O5Cl4Fe3HCN]+ ion. In addition, the fragmentation

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L

(a)

LCu4Cl3

(b) LFe3Cl3

(c)

LMn3(ACO)2(H2O)

(d) LPt4Cl3

(e)

LZn4Cl3

(f)

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 [C97H67N10O5Cl4Fe3(HCN+Cl+H2O)]+, [C97H67N10O5Cl4Fe3(HCN+ Cl2+H2O+CH3)]+ and [C97H67N10O5Cl4Fe3(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 fragmentation peaks for the Cu(II), Pt(II) and Mn(III) complexes were also shown in their mass spectra. The electronic properties of the new symmetric ligand (L) and its transition metal complexes were investigated in the DMF,

DMSO, CH2Cl2 and toluene solvents and obtained data are given in the Table 3. The Uv–vis spectra of the ligand and its metal complexes in DMF and DMSO solutions were shown in Fig. 6. On the other hand, the compounds TPP, TPP-NO2 and TPP-NH2 were studied in the toluene solutions and obtained data are given in the experimental section. As Soret band is arised from an intense permitted 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 compounds have Soret bands in the 425–416 nm range. The Q band of the new free Schiff base porphyrin ligand (L) is occured four components: Qx(0, 0), Qx(1, 0), Qy(0, 0) and Qy(1, 0) which are associated with D2h symmetry. Q-bands of the porphyrin derivatives

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Table 5 The electrochemical data of a new symmetric porphyrin Schiff base ligand (L) and its transition metal complexes. Compound L

Concentration (M) 4

1  10

1  105

LCu4Cl3

1  104

1  105

Scan rate (mV/s)

Epa (V)

100 250 500 750 1000 100 250 500 750 1000

0.65, 0.64, 0.63, 0.62, 0.60, 0.55, 0.54, 0.53, 0.52, 0.50,

100 250 500 750 1000 100 250 500 750 1000

0.64, 0.66, 0.68, 0.70, 0.73, 0,44, 0,43, 0.42, 0.40, 0,38,

Epc (V)

Ipa/Ipc

E1/2 (V)

DEp (V)

0.40 0.41 0.42 0.43 0.45 0.60 0.62 0.65 0.68 0.72

0.35, 0.36, 0.37, 0.38, 0.39, 0.55, 0.52, 0.50, 0.47, 0.44,

0.90 0.91 0.92 0.93 0.95 0.73 0.76 0.78 0.80 0.82

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

0.69 0.70 0.71 0.72 0.73 0.64 0.65 0.66 0.67 0.68

0.82, 0.83, 0.84, 0.86, 0.88, 0.65, 0.66, 0.67, 0.69, 0.71,

0.58 0.62 0.66 0.68 0.70 0.88 0.85 0.82 0.79 0.76

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

LPt4Cl3

1  104

100 250 500 750 1000

0.29 0.27 0.26 0.24 0.23

0.50, 0.48, 0.46, 0.45, 0.44,

0.70 0.72 0.75 0.77 0.79

0.41 0.38 0.35 0.31 0.29

– – – – –

0.41 0.45 0.49 0.53 0.56

LPt4Cl3

1  105

100 250 500 750 1000

0.23 0.20 0.18 0.16 0.14

0.76, 0.74, 0.73, 0.72, 0.70,

0.47 0.48 0.49 0.50 0.52

0.49 0.42 0.36 0.32 0.27

– – – – –

0.24 0.28 0.31 0.34 0.38

LZn4Cl3

1  104

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, 0.56, 0.58, 0.59, 0.61, 0.73, 0.71, 0.70, 0.69, 0.67,

0.61 0.63 0.66 0.68 0.70 0.12, 0.13, 0.14, 0.15, 0.16,

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

100 250 500 750 1000 100 250 500 750 1000

0.44, 0.42, 0.40, 0.37, 0.34, 0.41 0.39 0.36 0.34 0.32

1.08 1.09 1.10 1.11 1.12

0.52, 0.51, 0.50, 0.49, 0.47, 0.61, 0.59, 0.56, 0.53, 0.50,

0.87 0.89 0.91 0.94 0.97 0.82 0.84 0.85 0.86 0.88

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

0.47, 0.46, 0.45, 0.43, 0.41,

0.12, 0.11, 0.10, 0.09, 0.08,

0.85 0.89 0.92 0.95 1.00

– – 0.65 0.65 0.64

0.10 0.07 0.05 0.03 0.04

0.21, 0.23, 0.24, 0.25, 0.26,

0.08 0.10 0.12 0.14 0.17

1.57 1.39 1.25 1.12 1.00

– – – 0.27 0.26

0.12 0.09 0.06 0.03 0.26

1  105

LFe3Cl4(H2O)3

1  104

1  105

LMn3(AcO)4(H2O)

1  104

100 250 500 750 1000

0.60, 0.61, 0.62, 0.63, 0.64,

0.10, 0.11, 0.12, 0.13, 0.14,

LMn3(AcO)4(H2O)

1  105

100 250 500 750 1000

0.23, 0.25, 0.28, 0.30, 0.32,

0.33 0.32 0.30 0.28 0.26

0.88 0.86 0.84 0.83 0.82

1.11 1.13 1.15 1.16 1.17

0.70 0.68 0.67 0,66 0.64

All the potentials are referenced to Ag+/AgCl; where Epa and Epc are anodic and cathodic potentials, respectively. DEp = EpaEpc. E1/2 = 0.5  (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 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 ultraviolet part of the spectrum. While the Soret band was shown at

415 nm in DMF and CH2Cl2 solutions, the band in DMSO and toluene solutions were determined at 420 and 422 nm, respectively. Q-bands of the ligand were found in the 514–649 nm range. Q-band in the toluene solution shifted to lower shorter wavelengths (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

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838

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 determined 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) complexes, 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) complexes 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) complexes 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. Excitation and emission spectra of the new symmetric porphyrin Schiff base ligand (L) and its transition metal complexes were investigated in the different concentrations (1  103– 1  107 M range) and obtained data are given in Table 4. The spectra 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  103 M concentration. The former peak corresponds 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  103 to 1  107 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 808 nm in Cu(II) complex was not observed in the emission spectrum of the ligand (L). The emission and excitation spectra of the Fe(III) and Zn(II) complexes have also similar properties to the Cu(II) complex in the 1  103– 1  107 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 emission spectra of the Pt(II) complex indicate two peaks in the 656– 786 nm range. The absorption intensities of the emission and excitation spectra of the ligand (L) and its metal complexes were decreased depending upon by the changing of the solution concentration.

833

L, DMF, 1x10-4 M

LCu4Cl3, DMF, 1x10-4 M

LPt4Cl3, DMF, 1x10-4

LZn4Cl3, DMF, 1x10-4 M

LFe3Cl4(H2O)3, DMF, 1x10-4 M

LMn3(AcO)4(H2O), DMF, 1x10-4 M

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

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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. is DTG.

Bu4NBF4 as supporting electrolyte at 293 K. All potentials quoted refer to measurements run at a scan rates in the 100– 1000 mV s1 range and against an internal ferrocene–ferrocenium standard, unless otherwise stated. The electrochemical studies were studied in the 1  104 and 1  105 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 s1 scan rate, in the 1  104 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 s1, respectively. At the 1000 mV s1 scan rate, the ligand shows the quasi-reversible redox process at 0.45/0.39

line is TG,

line is DTA,

line

V (Epa/Epc) potential. In the 1  105 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 s1 scan rate. At the other scan rates, the ligand shows the irreversible redox processes. In the reversible redox processes, the ligand shows the amin-imine transformation [38]. In the 1  104 and 1  105 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  104 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  105 M solution, the Pt(II) complex has also similar electrochemical properties. All redox processes are irreversible in the 100–1000 mV s1 range

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S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838 Table 6 IC50 values and catalytic rate for SOD activity of the complexes. Compounds LCu4Cl3 LMn3(AcO)4(H2O) LFe3Cl4(H2O)3 LPt4Cl3 LZn4Cl3 M40404 Mn(ClO4)2 Mn(ClO4)2 + EDTA MnSalen(EUK8) M40403 MnSOD CuZnSOD (bovine)

IC50 (lM) WST-1 assay 0.96 0.73 0.62 1.19 1.03 – – – – – –

kcat (M1 s1) 6

1.67  10 2.19  106 2.58  106 1.35  106 1.56  106 1.6  109 1.3  106 3.4  104 8  105 1.6  107 5.2  108 2  109

Method

Refs.

Indirect Indirect Indirect Indirect Indirect Stopped-flow Indirect Indirect Stopped-flow Stopped-flow indirect Pulse radiolysis

This This This This This [4] [5] [6] [7] [8] [9] [10]

work work work work work

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  104 M solution similar to the Pt(II) complex and its redox behavior is irreversible at all potentials. On the other hand, 1  105 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  104 M solution shows three anodic and cathodic peaks. At the 500, 750 and 1000 mV s1 scan rates, the complex has reversible redox processes in the 0.67–()0.62 V range. Furthermore, at the 100 and 250 mV s1 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  105 M solution, the Mn(III) complex has reversible redox process at 0.26 V potential and 1000 mV s1 scan rates. But, at the another scan rates, the complex has irreversible redox behavior. Thermal analysis studies of the symmetric porphyrin Schiff base ligand (L) and its transition metal complexes were investigated in an air atmosphere at a heating rate of 10 °C/min. The TG and DTA 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 processes are taken place in four steps. In the first step, in the 120– 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 stability 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 decompose in the 350–600 °C temperature range. In this temperature range, the big exothermic peaks corresponds to the loss of porphyrin rings. In the last step, the metal oxides occured.

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

Fig. 10. Dismutation of superoxide by metal complexes.

complexes in this study exhibit considerable SOD activity, as compared with native Mn-SOD and some complexes in the literature listed in Table 6. 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 (Fig. 10). The complexes showed SOD activity with rate constants in the range of 2.58  106–1.35  106 M1 s1. The Fe(III) complex showed the greatest SOD activity with an IC50 value of 0.62 lM which gives a calculated Kcat value of 2.58  106 M1 s1. 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 porphyrin 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 hypochromism 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

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Fig. 11. UV spectra of the L 1/10: DMSO/MeOH ([L] = 1  106 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  106 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].

Table 7 The intrinsic binding constants (Kb) of compounds with DNA. Compounds

Kb

L LCu4Cl3 LZn4Cl3 LMn3(AcO)4(H2O) LFe3Cl4(H2O)3 LPt4Cl3

5  106 1.5  106 2  106 1.4  106 8.8  106 1  105

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 intercalative, 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 porphyrins and metallo porphyrins in the body. The interaction can be studied with UV spectroscopy in order to investigate the

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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  106 M L (kmax = 416.12 nm, Amax = 0.48 A) upon addition of increasing amounts of FSdsDNA. Even though no appreciable change in the position of the intraligand band of L and its metal complexes are observed by addition of different initial concentration of FSdsDNA (initial concentration and UV–Vis results for metal complexes; 1  106 M for LCu4Cl3: kmax = 414.24 nm, Amax = 0.5 A, 3  106 M for LZn4Cl3: kmax = 422.90 nm, Amax = 0.36 A, 2  106 M for LMn3(AcO)4(H2O): kmax = 415.66 nm, Amax = 0.44 A, 2  106 M for LFe3Cl4(H2O)3: kmax = 416.00 nm, Amax = 0.5 A) and 2  106 M for LPt4Cl3: kmax = 416.00 nm, Amax = 0.5 A are observed by addition of different initial concentration of FSdsDNA (2–6 ppm for L; kA = 0.33–0.21 A and Dkmax = 8.03–7.19 nm, 0.25–3 ppm for LCu4Cl3; DA = 0.17–0.11 A and Dkmax = 8.34–7.84 nm, 0.25–4 ppm for LZn4Cl3; DA = 0.18– 0.12 A and Dkmax = 8.85–7.86 nm, 0.25–3 ppm for LMn3(AcO)4 (H2O); DkA = 0.44–0.28 A and Dkmax = 7.40–6.93 nm, 0.25–3 ppm for LFe3Cl4(H2O)3; DkA = 0.3–0.15 A and Dkmax = 10.23–6.29 nm and 0.25–3 ppm for LPt4Cl3; DkA = 0.2–0.12 A and Dkmax = 10.01– 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 complex 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 hypochromism 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 subsequently 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) complexes 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]

½DNA=ðea  ef Þ ¼ ½DNA=ðeb  ef Þ þ 1=K b ðea  ef Þ

ð1Þ

where ea = Aobs/[Complex], ea = extinction coefficient for the free complex and eb = extinction coefficient for compound in the fully bound form, respectively. In plots [DNA]/(eb  ef) vs. [DNA], Kb is given by the ratio of slope to the y intercept (insets in Figs. 11 and 12). The determined Kb values for L and its complexes are given in Table 7. 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 enhances significantly the ability to bind to FSdsDNA. This is an important point Kb of porphyrin and

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metalloporphyrin is higher than the EB binding affinity for DNA (Kb = 1.23 ± 0.07  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. 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 characterization of the 4-methoxy-2,6-diformylphenol compound by X-ray crystallography method. Then, we prepared a new symmetric porphyrin Schiff base ligand (L) and its transition metal complexes. 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 pholuminescence 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 significantly the ability to bind to FSdsDNA. 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 crystallographic 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 [email protected], 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. References [1] [2] [3] [4]

A. Prakash, D. Adhikari, Int. J. Chem. Tech. Res. 3 (2011) 1891. E.M. McGarrigle, D.G. Gilheany, Chem. Rev. 105 (2004) 1563. S. Kumar, D.N. Dhar, P.N. Saxena, I.I.T. Kanpur, J. Sci. Indus. Res. 68 (2009) 181. _ Demirtasß, M. Elmastasß, M. Tümer, Spectrochim. G. Ceyhan, C. Çelik, S. Urusß, I. Acta, Part A 81 (1) (2011) 184. [5] N. Demirezen, D. Tarınç, D. Polat, M. Çesßme, A. Gölcü, M. Tümer, Spectrochim. Acta, Part A 94 (2012) 243–255. [6] G. Ceyhan, M. Tümer, M. Köse, V. McKee, S. Akar, J. Lumin. 132 (11) (2012) 2917. _ Demirtasß, A.S ß. Yag˘liog˘lu, V. McKee, J. Lumin. [7] G. Ceyhan, M. Köse, M. Tümer, I. 143 (2013) 623.

838

S. Çay et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 821–838

[8] S. Koçer, S. Urusß, A. Çakır, M. Güllüce, M. Dıg˘rak, Y. Alan, A. Aslan, M. Tümer, M. Karadayı, C. Kazaz, H. Dal, Dalton Trans. 43 (16) (2014) 6148. _ Demirtasß, I. _ Gönül, V. McKee, Spectrochim. [9] M. Köse, G. Ceyhan, M. Tümer, I. Acta, Part A 137 (2015) 477. _ Demirtasß, V. McKee, Spectrochim. Acta, Part A, [10] G. Ceyhan, M. Köse, M. Tümer, I. under review. [11] W. Waskitoaji, T. Hyakutake, J. Kato, M. Watanabe, H. Nishide, Chem. Lett. 38 (2009) 1164. [12] C.T. Poon, S. Zhao, W.K. Wong, D.W.J. Kwong, Tetrahedron Lett. 51 (2010) 664. [13] M.J. Shieh, C.L. Peng, P.J. Lou, C.H. Chiu, T.Y. Tsai, C.Y. Hsu, C.Y. Yeh, P.S. Lai, J. Control. Release 7 (2008) 200. [14] M. Yedukondalu, M. Ravikanth, Coord. Chem. Rev. 255 (2011) 547. [15] R.J. Fiel, J. Biomol. Struct. Dyn. 6 (1989) 1259. [16] Y. Ishikawa, N. Yamakawa, T. Uno, Bioorg. Med. Chem. 10 (2002) 1953. [17] A. D’Urso, A. Mammana, M. Balaz, A.E. Holmes, N. Berova, R. Lauceri, R. Purrello, J. Am. Chem. Soc. 131 (2009) 2046. [18] E.K. Efthimiadou, N. Katsaros, A. Karaliota, G. Psomas, Bioorg. Med. Chem. Lett. 17 (2007) 1238. [19] A.A. Nejo, G.A. Kolawole, A.R. Opoku, J. Wolowska, P. O’Brien, Inorg. Chem. Acta 362 (2009) 3993. [20] A. McCrate, M. Carlone, M. Nielsen, S. Swavey, Inorg. Chem. Commun. 13 (2010) 537. [21] E.D. Sternberg, D. Dolphin, C. Bruckner, Tetrahedron 54 (1998) 4151. [22] L.W. Oberley, D.S.T. Clair, A.P. Anto, T.D. Oberley, Arch. Biochem. Biophys. 254 (1987) 69. [23] K. Suzuki, M. Nakamura, Y. Hatanaka, Y. Kayanoki, H. Tatsumi, N. Taniguchi, J. Biochem. 122 (1997) 1260. [24] J.J. Li, L.W. Oberley, Cancer Res. 57 (1997) 1991. [25] M. Kizaki, A. Sakashita, A. Karmakar, C.-W. Lin, H.P. Koeffler, Blood 82 (1993) 1142. [26] Bruker (1998). APEX2 and SAINT Bruker AXS Inc. [27] G.M. Sheldrick, A short history of SHELX, Acta Cryst. A64 (2008) 112. [28] J.M. Mccord, I. Fridovic, J. Biol. Chem. 244 (1969) 6049. [29] S. Goldstein, G. Czapski, Free Radic. Res. Commun. 12 (1991) 5. [30] Z.L. Chu, W. Huang, S.H. Gou, Acta Cryst. E61 (2005) o1624. [31] J.C. Jiang, G. Wang, W. You, W. Huang, Acta Cryst. E64 (2008) o1426. [32] A. Rest, in: J.D. Coyle, R.R. Hill, D.R. Roberts (Eds.), Light, Chemical Change and Life: A Source Book of Photochemistry, The Open University Press, Walton Hall, 1982. Chapter 2.3.

[33] G.H. Barnett, M.F. Hudson, K.M. Smith, J. Chem. Soc., Perkin Trans. 1 (1975) 1401. [34] W.J. Kruper, J.A. Chamberlin, M. Kochanny, J. Org. Chem. 54 (1989) 2753. [35] A. Gölcü, M. Tümer, H. Demirelli, R.A. Wheatley, Inorg. Chim. Acta 358 (2005) 1785. [36] W. Lian, Y. Sun, B. Wang, N. Shan, T. Shi, J. Serb. Chem. Soc. 77 (3) (2012) 335. [37] N.M.B. Neto, S.L. Oliveira, I. Guedes, L.R. Dinelli, L. Misoguti, C.R. Mendonça, A.A. Batista, S.C. Zílio, J. Braz. Chem. Soc. 17 (7) (2006) 1377. [38] M. Tümer, D. Ekinci, F. Tümer, A. Bulut, Spectrochim. Acta, Part A 67 (3–4) (2007) 916. [39] M. Tumer, H. Köksal, S. Serin, M. Dıg˘rak, Transition Met. Chem. 24 (1) (1999) 13. [40] J. Vanco, O. Svajlenova, E. Racanska, J. Muselık, J. Valentova, J. Trace Elem. Med Biol. 18 (2004) 155. [41] G.B. Deacon, R.J. Phillips, Coord. Chem. Rev. 33 (1980) 227. [42] K. Aston, N. Rath, A. Naik, U. Slomczynska, O.F. Schall, D.P. Riley, Inorg. Chem. 40 (2001) 1779. [43] S. Durot, C. Policar, F. Cisnetti, F. Lambert, J. Renault, G. Pelosi, G. Blain, H. Korri-Youssoufi, J. Mahy, Eur. J. Inorg. Chem. 17 (2005) 3513. [44] D. Riley, Chem. Rev. 99 (1999) 2573. [45] D. Salvemini, Z. Wang, J. Zweier, A. Samouilov, H. Macarthur, T. Misko, M. Currie, S. Cuzzocrea, J. Sikorski, D.P. Riley, Science 286 (1999) 304. [46] G. Liu, M. Filipovic, F.W. Heinemann, I. Ivanovic-Burmazovic, Inorg. Chem. 46 (2007) 8825. [47] D. Klugroth, I. Fridovic, J. Rabani, J. Am. Chem. Soc. 95 (1973) 2786. [48] H. Bading, Nucleic Acids Res. 16 (12) (1988) 5241. [49] L. Fotouhi, A.B. Hashkavayi, M.M. Heravi, Int. J. Biol. Macromol. 53 (2013) 101. [50] A.M. Pyle, J.P. Rehmann, R. Meshoyrer, C.V. Kumar, N.J. Turro, J.K. Barton, J. Am. Chem. Soc. 111 (1989) 3053. [51] T.M. Kelly, A.B. Tossi, D.J. McConnell, T.C. Strekas, Nucleic Acids Res. 13 (1985) 6017. [52] N. Shahabadi, S. Kashanian, M. Mahdavi, N. Sourinejad, Bioinorg. Chem. Appl. (2011), http://dx.doi.org/10.1155/2011/525794. Article number: 525794. [53] P. Heringova, J. Kasparkova, V. Brabec, J. Biol. Inorg. Chem. 14 (6) (2009) 959. [54] M. Monajjemi, F. Mollaamin, J. Clust. Sci. 23 (2) (2011) 259. _ Demirtasß, Spectrochim. Acta, Part A 135 (2015) 887. [55] M. Çesßme, A. Gölcü, I.