Browsing by Author "Icli S."
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Item Spectral properties and G-quadruplex DNA binding selectivities of a series of unsymmetrical perylene diimides(2007) Dincalp H.; Avcibasi N.; Icli S.A series of new unsymmetrical perylene diimides have been synthesized to investigate their binding selectivities to G-quadruplex DNA structure, a unique four-stranded DNA motif, which is significant to the regulation of telomerase activity. The structures of the perylene diimides have been characterized by IR spectrophotometer, 1H NMR, 13C NMR, MS, TGA and time-resolved instruments. Spectrochemical behaviors have been investigated by visible absorption and fluorescence emission spectra. The spectral characterization of the compounds has been investigated in five common organic solvents of different polarity and in water (in 170 mM phosphate buffer at pH 6). Marked red shifts of absorbance and fluorescence emission bands of the compounds in aqueous solution are compared with the other organic solutions. The fluorescence quantum yields are determined low in more polar solvents and also calculated to be about less than about 0.05 in aqueous solution because of the aggregation effects. Photodegradation rate constants (kp) of the synthesized compounds have been compared under xenon lamp irradiation in acetonitrile solution. Binding abilities of the synthesized perylene diimides to different form of DNA strands have been investigated by visible absorption and fluorescence spectroscopy in the phosphate buffer solutions. Also, pH-dependent aggregation and G-quadruplex DNA binding selectivity of these ligands have been compared. Among these ligands, N-(2,6-diisopropylphenyl)-N′-(4-pyridyl)-perylene-3,4,9,10-tetracarboxylic diimide (PYPER) has been found to be the most selective interactive ligand for G-quadruplex formed in the G4′-DNA structure. PYPER has shown a significant selectivity to G4′-DNA which is comprised of d(TTAGGG) repeats, known as human telomeres, in the phosphate buffer at pH 6. The absorption maximum of the PYPER/G4′-DNA complex has given bathochromic shift of 7 nm with respect to the absorption maximum of DNA-free solution of PYPER in phosphate buffer at pH 6. Fluorescence quenching experiments between PYPER and G4′-DNA show that PYPER demonstrates about a 9.3-fold selectivity for binding to G4′-DNA versus ds-DNA base pairs with the bimolecular rate constant of 0.95 × 1012 M-1 s-1. © 2006 Elsevier B.V. All rights reserved.Item New perylene derivative dyes for dye-sensitized solar cells(2007) Zafer C.; Kus M.; Turkmen G.; Dincalp H.; Demic S.; Kuban B.; Teoman Y.; Icli S.We have studied the influence of the spacer alkyl chain length of perylenemonoimide (PMI) dyes on the device performance in dye-sensitized solar cells (DSSCs). We observed that the dyes with longer and brunched alkyl chains exhibit higher efficiencies in DSSCs. In line with these statements we now report the highest efficiency obtained under standard conditions for a perylene imide derivative with PMI-DA1 that performs 300 mV open circuit voltage, 9.79 mA/cm2 short-circuit current and 1.61% overall conversion efficiency. © 2006.Item New thiophene-based azo ligands containing azo methine group in the main chain for the determination of copper(II) ions(2007) Dinçalp H.; Toker F.; Durucasu I.; Avcibaşi N.; Icli S.New kind of azo chromophores containing thiophene moiety and salicyaldimine-based ligand as side chains have been synthesized by a sequential process for optical sensing of Cu2+ metal ions in organic solution. Compounds have been characterized by IR and UV-vis spectrophotometer, 1H NMR, 13C NMR, MS, TGA and CV instruments. Spectral characteristics of the synthesized compounds have been investigated in five organic solvents of different polarity. Polarizibility effects of the solvents on the spectral characteristics and the dipole moments in the excited state are estimated. The fluorescence quantum yields of the synthesized compounds have been calculated to be in the range of 0.0035-0.0095 in solvents of different polarity. The fluorescence emission quenching experiments between the synthesized compounds and electron donor (pyrene, anthracene), electron acceptor (Co2+) compounds give the bimolecular quenching rate constants of 1011 and 1014 M-1 s-1, respectively. The free energies of photo-electron transfer process (ΔGET) between the azo dyes and the quenchers have been found to be about -19 kcal/mol. Cyclic voltammetry studies indicate that synthesized azo ligands undergo two- or three-reversible reduction potentials (versus ferrocene) and give LUMO energy value of -3.07 eV which is lower than that of TiO2 conduction band and has a band gap value of ∼2.5 eV. These results may point that synthesized azo dyes could be used as hole conducting materials in solid DSSC (Dye Sensitized Solar Cell) devices. Thermal decomposition behavior of the azo dyes gives more information about the structure of the studied materials. The photoisomerization behavior of the synthesized compounds has been investigated in ethyl acetate under Xe lamp irradiation in the fluorescence spectrophotometer for 1 h. Photoisomerization rate constants of cis-trans orientation (kc-t) have been found to be about 10-5 s-1. The complexation process of synthesized thienylidene azo dyes gives subtle changes in their absorption spectra. © 2006 Elsevier Ltd. All rights reserved.Item Optical and electrochemical properties of polyether derivatives of perylenediimides adsorbed on nanocrystalline metal oxide films(Elsevier, 2008) Kus M.; Hakli O.; Zafer C.; Varlikli C.; Demic S.; Özçelik S.; Icli S.We report optical and electrochemical properties of polyether derivatives of perylenediimides (PDIs) thin films formed in various materials (semiconductor, insulator, amorphous and self-assembly). Perylenediimides adsorbed on nanocrystalline TiO2 (NT) nanocrystalline alumina (NA), amorphous silicon (PS) and neat self-assemblied (SA) films were prepared and characterized based on spectroscopic, electrochemical, spectro-electrochemical techniques. The absorption and fluorescence spectra of PDIs in chloroform exhibit vibronic features. The fluorescence quantum yields (Φf) of PDIs with end amino substituents in chloroform solutions are over 0.95, while the quantum yield of triethoxyphenyl substituted PDI Φf value is 0.024 in solution. Optical spectroscopy proves that PDIs in metal oxide thin films form aggregated type complexes. An electrochromism, a color change from red to blue/violet, is observed on metal oxide films, that indicates existence of mono and dianion forms of PDIs. Reversibility of electrochemical reductions in NT film depends on the scanning rate. However, electrochromism in NA films is stable and reversibility is independent from scanning rate. Stable mono and diaionic species are formed on NA films. SA films show broad absorption peaks during the voltammetric scan. On the other hand, the first reduction onset potentials of PDIs are almost equal to the onset potential of capacitive current of TiO2 which lead to low efficiency in dye-sensitized solar cells. © 2008 Elsevier B.V. All rights reserved.Item Synthesis and spectroscopic characterization on 4-(2,5-di-2-thienyl-1H-pyrrol-1-yl) benzoic acid: A DFT approach(Elsevier, 2016) Kurt M.; Sas E.B.; Can M.; Okur S.; Icli S.; Demic S.; Karabacak M.; Jayavarthanan T.; Sundaraganesan N.Abstract A complete structural and vibrational analysis of the 4-(2,5-di-2-thienyl-1H-pyrrol-1-yl) benzoic acid (TPBA), was carried out by ab initio calculations, at the density functional theory (DFT) method. Molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO) 13C NMR and 1H NMR chemical shift values of (TPBA), in the ground state have been calculated by using ab initio density functional theory (DFT/B3LYP) method with 6-311G(d,p) as basis set for the first time. Comparison of the observed fundamental vibrational modes of (TPBA) and calculated results by DFT/B3LYP method indicates that B3LYP level of theory giving yield good results for quantum chemical studies. Vibrational wavenumbers obtained by the DFT/B3LYP method are in good agreement with the experimental data. The study was complemented with a natural bond orbital (NBO) analysis, to evaluate the significance of hyperconjugative interactions and electrostatic effects on such molecular structure. By using TD-DFT method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental one is determined. In addition, the molecular electrostatic potential (MEP), frontier molecular orbitals analysis and thermodynamic properties of TPBA were investigated using theoretical calculations. © 2015 Elsevier B.V.