Accepted Manuscript Monodentate Schiff base ligands: Their structural characterization, photoluminescence, anticancer, electrochemical and sensor properties Muhammet Köse, Gökhan Ceyhan, Mehmet Tümer, İbrahim Demirtaş, İlyas Gönül, Vickie McKee PII: DOI: Reference:

S1386-1425(14)01279-7 http://dx.doi.org/10.1016/j.saa.2014.08.088 SAA 12609

To appear in:

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Received Date: Revised Date: Accepted Date:

17 July 2014 21 August 2014 24 August 2014

Please cite this article as: M. Köse, G. Ceyhan, M. Tümer, İ. Demirtaş, İ. Gönül, V. McKee, Monodentate Schiff base ligands: Their structural characterization, photoluminescence, anticancer, electrochemical and sensor properties, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), doi: http://dx.doi.org/ 10.1016/j.saa.2014.08.088

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Monodentate Schiff base ligands: Their structural characterization, photoluminescence, anticancer, electrochemical and sensor properties

Muhammet Kösea, Gökhan Ceyhana, Mehmet Tümera*, İbrahim Demirtaşb, İlyas Gönülc, Vickie McKeed a

Chemistry Department, K.Maras Sütcü Imam University, 46100, K.Maras, Turkey.

b

Chemistry Department, Çankırı Karatekin University, 18100, Çankırı, Turkey.

c

Chemistry Department, Çukurova University, 01100, Adana, Turkey.

d

Chemistry Department, Loughborough University, LE11 3TU, Leics, UK.

ABSTRACT Two Schiff base compounds, N,N’-bis(2-methoxy phenylidene)-1,5-diamino naphthalene (L1) and N,N’-bis(3,4,5-trimethoxy phenylidene)-1,5-diamino naphthalene (L2) were synthesized and characterized by the analytical and spectroscopic methods. The electrochemical and photoluminescence properties of the Schiff bases were investigated in the different conditions. The compounds L1 and L2 show the reversible redox processes at some potentials. The sensor properties of the Schiff bases were examined and color changes were observed upon addition of the metal cations, such as Hg(II), Cu(II), Co(II) and Al(III). The Schiff base compounds show the bathochromic shift from 545 to 585 nm. The single crystals of the compounds (L1) and (L2) were obtained from the methanol solution and characterized structurally by the X-ray crystallography technique. The molecule L2 is centrosymmetric whereas the L1 has no crystallographically imposed molecular symmetry. However, the molecular structures for these compounds are quite similar, differing principally in the conformation about methoxy groups and the dihedral angle between the two aromatic rings and diamine naphthalene.

Keywords: Schiff base, Colorimetric sensors, Electrochemistry, Photoluminescence, Anticancer Corresponding author: Mehmet Tümer Tel.: +90 344 280 14 44, Fax: +90 344 280 13 52, E-mail address: [email protected]

1

1.

Introduction Schiff base ligands have comprehensive applications in a great deal of, such as

biological, inorganic and analytical chemistry [1-5]. Application of many new analytical devices requires the presence of organic reagents as essential compounds of the measuring system. Schiff base ligands are used in optical and electrochemical sensors, and likewise in several chromatographic methods, to make possible detection of enhance selectivity and sensitivity [6-8]. The Schiff base compounds have high biological properties substances [910]. As the Schiff base ligands have high coordination capability, they are widely used in analytical applications. Schiff base ligands can be easily synthesized by reactions of condensation of primary amines and carbonyl compounds in which the azomethine bond is formed and they can used as complex formation reactions (determination of amines, carbonyl compounds and metal ions); or utilizing the variation in their spectroscopic characteristics. A great number of metal complexes of the Schiff bases (acyclic or cyclic) have been prepared, and they have provided an enormously rich world of chemistry [11]. Transition metal complexes derived from Schiff bases have occupied a central role in the development of coordination chemistry. The azomethine group >C=N of the Schiff base forming a stable metal complexes by coordinating through nitrogen atom. Schiff base ligands are able to coordinate many different metals, and to stabilise them in various oxidation states, enabling the use of Schiff base metal complexes for a large variety of useful catalytic transformations. As the Schiff base compounds contain the imine (>C=N), hydroxyl and various alkyl or alkoxy groups, they have high bioigical activity. Recently, we synthesized some monodentate Schiff base ligands and characterized structurally. As a continuation of our interest in the coordination behavior of Schiff bases with aromatic and aliphatic amines, the synthesis, structural characterization, luminescence, electrochemical, catalysis and anticancer activities of various metal complexes were reported [12-16]. In this study, two Schiff base compounds, N,N’-bis(2-methoxy benzaldiimine)-1,5diamino

naphthalene

(L1)

and

N,N’-bis(2,3,4-trimethoxy benzaldiimine)-1,5-diamino

naphthalene (L2) were prepared and characterized by analytical and spectroscopic methods. The compounds were structurally characterized by X-ray diffraction studies. Additionally, electrochemical, thermal, luminescence and anticancer properties of the compounds were investigated. To investigate the sensor properties of the Schiff base ligands (L1 and L2), the metal cations K(I), Na(I), Ba(II), Cd(II), Co(II), Cu(II), Hg(II), Mg(II), Mn(II), Ni(II), Zn(II) and Al(III) for complexation with ligands were used.

2

2.

Experimental

2.1

Materials and 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 disc (4000-400 cm-1) 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. Mass spectra of the ligands were recorded on a LC/MS APCI AGILENT 1100 MSD spectrophotometer. 1H and

13

C NMR spectra were

recorded on a Bruker 400 MHz instrument. TMS was used as internal standard and CDCl3 as solvent. The thermal analysis 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 single-photon fluorescence spectra of the Schiff base compounds L1 and L2 were collected on a Perkin Elmer LS55 luminescence spectrometer. All samples were prepared in spectrophotometric grade solvents and analysed in a 1 cm optical path quartz cuvette. The solutions of ligands (1.0 x 10 -3-1.0 x 10 -7 mol L-1) were prepared in DMF solvent. To investigate the solvent effect on the photoluminescence spectra of the ligands, the DMF, CHCl3, CH2Cl2, THF and dithylether solutions (1.0 x 10 -3 mol L-1) of the compounds were used. A stock solution of a concentration of 1x10–3 M and 1x10–4 M of Schiff base compounds was prepared in DMF 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 made at room temperature in an undivided cell (BAS model C–3 cell stand) with a platinum counter electrode and an Ag+/AgCl 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 3

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. Data collection for X-ray crystallography was completed using a Bruker APEX2 CCD diffractometer and data reduction was performed using Bruker SAINT [17]. SHELXTL was used to solve and refine the structures [18]. 2.2

Synthesis of the Schiff base compounds

The benzaldehyde derivatives (2 mmol; 272 mg) 2-methoxy benzaldehyde for L1 and 392 mg 2,3,4-trimethoxy benzaldehyde for L2) in ethanol (20 mL, absolute) and 1,5-diamino naphthalene (1 mmol, 264 mg) in ethanol (20 mL, absolute) were mixed and refluxed for about 10 h at 80 °C. The color of the solution changed to brown. After cooling the solution, the resulting precipitate was filtered and washed with cold ethanol. Single crystals of the Schiff base compounds (L1 and L2) suitable for X-ray diffraction study were obtained by slow evaporation of the compounds in ethanol. Physical properties and other spectroscopic data are given in the experimental section. L1: (C26H22N2O2). Yield: 87%, color: brown, d.p.: 218 °C(decompose). Elemental analyses, found (calcd. %): C, 79.13 (79.16); H, 5.66 (5.62); N, 7.07 (7.10). 1H NMR (DMSO-d6, δ (ppm)): 8.63 (s, CH=N, 2H), 7.81-6.24 (m, Ar-H, 14H), 3.88 (s, OCH3, 6H). 13C NMR (DMSO-d6, δ (ppm)): 164.05 (CH=N), 155.15-110.50 (Ar-C), 58.10 (OCH3). Mass spectrum (LC/MS APCI): m/z 394 [M]+ (100%), m/z 393 [M - 1]+ (13%), m/z 395 [M + 1]+ (25%), m/z 395 [M + 2]+ (50%). FT-IR: (KBr, cm-1): 3010 ν(C-H)aromatic, 2975 ν(C-H)alph, 1612 ν(CH=N). L2: (C30H30N2O6). Yield: 88%, color: brown, d.p.: 226 °C (decompose). Elemental analyses, found (calcd. %): C, 69.97 (70.02); H, 5.93 (5.88); N, 5.49 (5.45). 1H NMR (DMSO-d6, δ (ppm)): 8.85 (s, CH=N, 2H), 7.85-6.20 (m, Ar-H, 10H), 3.95, 384, 3.80 (s, OCH3, 18H). 13C NMR (DMSO-d6, δ (ppm)): 163.40 (CH=N), 158.45-111.25 (Ar-C), 59.85, 58.60, 57.75 (OCH3). Mass spectrum (LC/MS APCI): m/z 514 [M]+ (100%), m/z 515 [M + 1]+ (35%), m/z 516 [M + 2]+ (42%). FT-IR: (KBr, cm-1): 3006 ν(C-H)aromatic, 2942 ν(C-H)alph, 1614 ν(CH=N).

4

2.3

X-Ray Determination

X-ray diffraction data for these compounds were collected at 150(2)K on a Bruker Apex II CCD diffractometer using Mo-K α radiation (λ = 0.71073 Å) . The structures were solved by direct methods and refined on F2 using all the reflections [18]. All the non-hydrogen atoms were refined using anisotropic atomic displacement parameters and hydrogen atoms bonded to carbon were inserted at calculated positions using a riding model. 2.4

Anticancer activity studies of the Schiff base compounds

2.4.1 Preparation of samples Stock solutions of the samples were prepared in DMSO and diluted with Dulbecco’s modified eagle medium (DMEM). DMSO final concentration is below 1% in all tests. 2.4.2 Cell lines and cell culture HeLa, Vero and C6 cancer cell lines were grown in Dulbecco’s modified eagle medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 2% penicilin streptomycin. The medium was changed twice a week. 2.4.3 Cell proliferation assay Antiproliferative effects of the plants were investigated on Vero cells (African green monkey kidney), C6 cells (Rat Brain tumor cells) and HeLa cells (human uterus carcinoma) using proliferation BrdU ELISA assay [19,20]. Cultured cells were grown in 96-well plates (COSTAR, Corning, USA) at a density of 3 x 104 cells/well. In each experimental set, cells were plated in triplicates and replicated twice. The cell lines were exposed to two concentrations of methanolic extracts of different organs (flower, steam and root) of CC, for 24 h at 37 °C in a humidified atmosphere of 5% CO2. 5-Fluorouracil, cisplatin were used as standart compounds. Cells were than incubated for overnight before applying the BrdU Cell Proliferation ELISA assay reagent (Roche, Germany) according to manufacturer’s procedure. The amount of cell proliferation was assessed by determining the A450 nm of the culture media after addition of the substrate solution by using a microplate reader (Ryto, China). Results were reported as percentage of the inhibition of cell proliferation, where the optical density measured from vehicle-treated cells was considered to be 100% of proliferation. All assays were repeated at least twice using HeLa and C6 cells. Percentage of inhibition of cell proliferation was calculated as follows: 5

[1-(Asamples/Acontrol)]× 100. 2.4.4 Statistical analysis The results of investigation in vitro are means ± SD of nine measurement. Differences between groups were tested with ANOVA. p values of

Monodentate Schiff base ligands: their structural characterization, photoluminescence, anticancer, electrochemical and sensor properties.

Two Schiff base compounds, N,N'-bis(2-methoxy phenylidene)-1,5-diamino naphthalene (L(1)) and N,N'-bis(3,4,5-trimethoxy phenylidene)-1,5-diamino napht...
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