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Öğe A Cation Radical From 2,6-Dimethoxypyridine - Investigations By Insitu Radiolysis Esr(Pergamon-Elsevier Science Ltd, 1989) Icli, SÖğe Characterization of N,N '-bis-2-(1-hydoxy-4-methylpentyl)-3,4,9,10-perylene bis (dicarboximide) sensitized nanocrystalline TiO2 solar cells with polythiophene hole conductors(Elsevier Science Bv, 2005) Zafer, C; Karapire, C; Sariciftci, NS; Icli, SWe have fabricated solid-state, dye-sensitized nanocrystalline TiO2 solar cells (DSSC) based on perylene derivative dye, N,N '-bis-2-(1-hydoxy-4-methylpentyl)-3,4,9,10-perylene bis (dicarboximide) (HMPER) with two different polythiophenes as hole conductors; i.e. poly (3-octyl thiophene) (P3OT) and poly (3-hexyl thiophene) (P3HT), respectively. HMPER adsorbs strongly to the surface of nanocrystalline TiO2 and inject electrons into TiO2 conduction band upon absorption of light. Polythiophene derivatives are well-known materials as hole conductors in solid-state dye-sensitized solar cells. We obtained quite similar results with P3OT and P3HT yielding a short-circuit current density of around 80 mu A/cm(2) and open-circuit voltage of around 0.7 V at 80 mW/cm(2) AM 1.5 light intensity. The results are compared with Ru-535 TBA-sensitized nc-TiO2 cells prepared by using the same polythiophene derivatives. (c) 2004 Elsevier B.V. All rights reserved.Öğe A comparative study of the photophysical properties of perylenediimides in liquid phase, PVC and sol-gel host matrices(Elsevier Sci Ltd, 2003) Karapire, C; Timur, C; Icli, SThe photophysical and photochemical properties of three different perylenediimide derivatives, N,N'-di-dodecylperylene-3,4,9,10-bis(diarboximide), N,N'-di-(1-dehydroabietyl)perylene-3,4,9,10-bis(dicarboximide) and N,N'-di-(4-carboxy phenyl)perylene-3,4,9,10-bis(dicarboximide) (N-DODEPER, ABIPER and PECA, respectively), were determined in immobilized pleases (PVC films, both plasticized and non-plasticized, and sol-gel matrix) using steady-state-fluorescence spectroscopy and compared with the data in solution phase. It was found that the plasticizers support the interaction of the dyes with the quencher and bis-(2-ethylhexyl)phthalate (DOP) itself acts as a quencher for the perylenediimide derivatives with aromatic substituents. The sol-gel matrix imparted serious changes to the properties of the perylenediimides. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe A comparative study of the photophysical properties of perylenediimides in liquid phase, PVC and sol-gel host matrices(Elsevier Sci Ltd, 2003) Karapire, C; Timur, C; Icli, SThe photophysical and photochemical properties of three different perylenediimide derivatives, N,N'-di-dodecylperylene-3,4,9,10-bis(diarboximide), N,N'-di-(1-dehydroabietyl)perylene-3,4,9,10-bis(dicarboximide) and N,N'-di-(4-carboxy phenyl)perylene-3,4,9,10-bis(dicarboximide) (N-DODEPER, ABIPER and PECA, respectively), were determined in immobilized pleases (PVC films, both plasticized and non-plasticized, and sol-gel matrix) using steady-state-fluorescence spectroscopy and compared with the data in solution phase. It was found that the plasticizers support the interaction of the dyes with the quencher and bis-(2-ethylhexyl)phthalate (DOP) itself acts as a quencher for the perylenediimide derivatives with aromatic substituents. The sol-gel matrix imparted serious changes to the properties of the perylenediimides. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Dielectric studies of tetraethylene glycol-bis(3-methylimidazolium) dichloride (TEGDC) exhibiting large negative dielectric anisotropy(Amer Chemical Soc, 2005) Yakuphanoglu, F; Okutan, M; Koysal, O; Ozder, S; Ocakoglu, K; Icli, SA dielectric anisotropy property of a TEGDC (tetraethylene glycol-bis(3-methylimidazolium) dichloride) is investigated as a function of frequency. TEGDC showed an extremely large negative dielectric anisotropy (-10.95 to -4753.73). Variation of dielectric anisotropy (Delta is an element of) with respect to the spot frequencies reveals that liquid crystal (LC) orientation has an n-type property at low frequencies and as the frequency increases dielectric anisotropy character shifts from negative dielectric anisotropy type (n-type) to positive dielectric anisotropy type (p-type). Consequently, the TEGDC is a liquid crystal with large negative dielectric anisotropy.Öğe Fluorescence emission and photooxidation studies with 5,6-and 6,7-benzocoumarins and a 5,6-benzochromone under direct and concentrated sun(Elsevier Science Sa, 2002) Karapire, C; Kolancilar, H; Oyman, U; Icli, S4-Methyl-8-hydroxy-benzo(6,7)coumarin, 1,4-methyl-6-hydroxy-benzo(5,6)coumarin, II, and 2-methyl-6-hydroxy-benzo(5,6)chromone, III, have shown similar absorption and fluorescence emission spectra. Fluorescence emission quantum yields for I and III are found to be very low, phi(f) = 0.02, but 4-methyl-6-hydroxy-benzo(5,6)coumarin, II, has a eight-fold higher fluorescence quantum yield of the other two specie, in acetonitrile solution, of = 0.16. Quenching of anthracene fluorescence emission by 1, II and III are found to give k(q) values of 1.0 x 10(7)-1.2 x 10(9) M-1 s(-1). Benzo(5,6)coumarin, II, which gives the most intense fluorescence also presents the highest quenching rate, k(q) = 1.2 x 10(9) M-1 s(-1). Experimentally determined k(q) values are seen to correlate well with the free energy of electron transfer (DeltaG(ET)) which are calculated to be in the range of -8.0 to -9.4 kcal/mol, where benzo(5,6)coumarin, II, gives the lowest free energy of electron transfer DeltaG(ET) = -9.4 kcal/mol. These results indicate that I-III behave as electron acceptor moieties toward a condensed aromatic ring, anthracene. The Stokes shift values of 88-105 mm and broad fluorescence emission bands respect to absorption-excitation bands, indicates a molecular structure change in the excited states of I-III. Fluorescence lifetimes of 0.1-0.9 ns in I-III, singlet oxygen quantum yields of 0.15 and 0.40 for I and II, respectively, may be taken as evidence of singlet-triplet intersystem crossings. The photooxidation products of alpha-terpinene, sensitised by II, under direct and concentrated sun light conditions that are mainly p-cymene and ascaridole. In accordance with literature data on coumarin derivatives, benzocoumarins also seem to produce singlet oxygen and beside singlet oxygen, in addition super oxide anion radical production appear to be dominant especially under concentrated sun light. Under direct sun light conditions ascaridole is the major product. Some by-products of alpha-terpinene photooxidation are also determined at GC-MS analysis. Those by-products are assumed to be generated from ascaridole decomposition. (C) 2002 Elsevier Science B.V All rights reserved.Öğe Fluorescence emission studies of an azlactone derivative embedded in polymer films - An optical sensor for pH measurements(Elsevier Science Sa, 2000) Ertekin, K; Alp, S; Karapire, C; Yenigul, B; Henden, E; Icli, SAzlactone molecules can be protonated in acidic media, and the process of protonation is irreversible due to ring opening in solutions. A new fully reversible pH sensor has been developed 4-(p-N,N-dimethylamino phenyl methylene)-2-phenyl-5-oxazolone (DPO), an azlactone derivative, embedded in a plasticized PVC polymer film. The sensor membrane is completely transparent and exhibits pH induced color change which is capable of measuring of pH in the range 1-7 and has a pK(a) value of 3.4. In agreement with crystal phase studies, DPO displays enhanced fluorescence emission quantum yield, Q(f) = 0.52, and fluorescence emission lifetime, tau (f) = 1.35 ns, in immobilized PVC film matrix, compared to Q(f) congruent to 0.03 and tau (f) = 0.02-0.03 ns in solutions. Stokes shift decreased to 46 nm in plasticized PVC film, with respect to Stokes shift of 81 nm in acetonitrile solution. Singlet energy, E-s = 60.4 kcal mol(-1), of DPO in PVC film, which is 1.1-1.4 kcal mol(-1) lower with respect to solutions, is taken as evidence of lessened singlet-triplet crossings in excited state of DPO in immobilized phase, and result in enhanced fluorescence emissions. (C) 2000 Elsevier Science B.V All rights reserved.Öğe Fluorescence emission studies on 1-phenyl-4-aroyl (and acyl)-1H-1,2,3-triazoles(Elsevier Science Bv, 1999) Icli, S; Astley, AS; Timur, C; Anac, O; Sezer, O; Dabak, KFluorescence emission from 378 nm excitation yielded fluorescence quantum yields Q(f), radiative lifetimes tau(0), and fluorescence rate constants k(f), in the range of 0.0004-0.0069, 17-132 ns and (0.9-18.2) x 10(6) s(-1), respectively, for seven 4-aroyl(acyl) derivatives of 1-phenyl-1,2,3-triazoles in chloroform solutions. The fluorescence lifetimes, tau(f), are estimated to be 0.01-0.45 ns. Some substitution effects are detected in the fluorescence emission parameters. The strong pi-electron donor, 5,10-dihydrocarbazolo[3,4-c]carbazole,is found ito be quenched by triazoles at quenching rates of 7.7 x 10(10)-2.8 x 10(12) M-1 s(-1). The high rates of fluorescence quenching, k(q), are attributed to a ground state complexation between 1,2,3-triazoles and the strong pi-electron donor carbazolocarbazole. 1,2,3-Triazoles have shown intense solvatochromic absorbance shifts in n-hexane, chloroform and methanol. Absorbance shifts reaching 44 nm were observed from polar to protic solvents. (C) 1999 Elsevier Science B.V. All rights reserved.Öğe Fluorescence Quantum Yields of Perylene 3,4,9,10-Tetracarboxylic Acid-Bis-N,N'-Aryl(Alkyl) Diimides(Marcel Dekker Inc, 1994) Icli, S; Icil, HThe synthesized perylenes 3,4,9,10-tetracarboxylic acid N,N'-ethyl, phenyl, rho-anisyl, alpha-naphthyl and acetyl diimides have shown great variations in absorption and emission spectra. The variation in molar extinction coefficients and fluorescence quantum yields have indicated that steric and electronic effects, caused by N-substitution, alters emission characteristics of perylene diimides significantly.Öğe Fluorescence quenching between strong pi-electron donor-acceptors of carbazolocarbazole and tetranitrofluorenone leading to electron transfer(Elsevier Science Bv, 1997) Icli, S; Icil, H; Whitten, DG; Sayil, C; Dityapak, ISinglet energies and fluorescence quantum yields of synthesized dihydrocarbazolocarbazole, 1, dimethylcarbazolocarbazole, 2, dibenzylcarbazolocarbazole, 3, were measured to be between 76.5-74.3 kcal/mol and 0.07-0.02 respectively. A Stern-Volmer plot of fluorescence quenching of dihydrocarbazolocarbazole, 1, with 2,4,5,7-tetranitrofluorenone, 4, has given a rate constant of quenching of k(q) = 7.4 x 10(12) M(-1)s(-1). The free energies of the exothermic electron transfer reaction are calculated to be -33.6 kcal/mol for dihydrocarbazolocarbazole, 1, and -26.8 kcal/mol for dimethylcarbazolocarbazole, 2. High values for the rate of fluorescence quenching and the free energies are the evidence for an electron transfer process between these strong pi-electron donor-acceptor complexed molecules.Öğe High fluorescence emissions of some natural benzofurane derivatives isolated from Styrax officinalis(Scientific Technical Research Council Turkey, 2000) Icli, S; Anil, H; Dindar, B; Alankus-Caliskan, O; Yayla, Y; Doroshenko, AO; Alp, SThe fluorescent properties of several natural benzofuran derivatives, egonols, isolated from Styrax officinalis, were determined. The studied egonol derivatives were found to be effective UV organic luminophores, with quantum yields of near to unity, phi(f) = 0.92. The fluorescence quenching experiments with electron donor molecules of aniline, N,N-dimethylaniline and carbazolocarbazole, presented very high efficiency of quenching at above diffusion quenching rates of 4.5x10(10), 2.1x10(x) and 5.6x10(12) s(-1)mol(-1), respectively. A strong electron acceptor molecule, tetranitrofluorenone, presented quenching rate of 2.6x10(11) s(-1)mol(-1). It is concluded that the first excited singlet state of egonol molecule is a more efficient electron acceptor.Öğe High rates of fluorescence quenching between perylene dodecyldiimide and certain pi-electron donors(Scientific Technical Research Council Turkey, 1997) Icli, S; Icil, H; Gurol, IPerylene bis-n-dodecyl diimide is found to quench fluorescenc emissions of naphthalene, phenanthrene and dihydrocarbazolocarbazole molecules at rates of 4.4 x 10(11), 2.8 x 10(12) and 2.5 x 10(4) M-1 sec(-1), in respective order of aromaticity. These unusulally high rates of fluorecence quenchings are attributed to Perrin model static quenching and presence of electron transfer through singlet excited state of perylene diimide. Calculated free energy of electron transfer, Delta G(ET)=-120.5 kJ/mol, between perylene diimide and dihydro carbazolocarbazole is taken as evidence for observation of high fluorescence quenching rate for carbazolocarbazole molecule.Öğe Highly chemoselective thiocarbonyl oxidation upon reaction of 4-methyl-3-phenyl-2-thiazolidinethione with singlet oxygen(Marcel Dekker Inc, 1996) Icli, S; Astley, ST; Timur, C; Altinok, A4-Methyl-3-phenyl-2-thiazolidinethione was reacted with both photochemically and chemically generated singlet oxygen. Despite reaction conditions which were selected to favor oxidation of the sulfide group, both reactions afforded a single product arising solely from thiocarbonyl oxidation.Öğe Insitu Radiolysis Esr Studies of Hydroxypyridones(Pergamon-Elsevier Science Ltd, 1990) Icli, SÖğe Isolation and structure elucidation of novel natural products from Turkish lichens(Scientific Technical Research Council Turkey, 2003) Kirmizigul, S; Koz, M; Anil, H; Icli, S; Zeybek, UThree natural products were isolated from three different Turkish lichens. Microbiological investigations were also examined of these lichens. Compound 1 is known as 2-hydroxy-4-methoxy-3,6-dimethyl benzoic acid, and is isolated from Pseudevernia furfuracea for the first time. Compounds 2 and 3 are detected as new compounds and called, 3-acetyl-4-amino-2-chloro-1-(4-hydroxy-2-methoxy-6-methylphenyl carbonyloxy) benzene and 2-(4-methoxyphenyl)-2-(5-oxo-4-phenyl-2,5-dihydro-2-furaniliden) acetic acid; they were isolated from Evernia prunastri and Letharia vulpina, respectively. All these compounds had different skeletons. Their structures were established by chemical methods and spectroscopic techniques using IR, UV, 1D and 2D NMR and EI and (+) FAB-Mass methods.Öğe Nmr, Absorption and Fluorescence Parameters of Azlactones(Marcel Dekker Inc, 1994) Icli, S; Icil, H; Alp, S; Koc, H; Mckillop, AAbsorption and fluorescence wavelenghts for a series of azlactones have been measured from acetonitrile solutions that had no pre-light exposure. Fluorescence quantum yields, Q(F), are found to be in general less than 0.01, excluding the the derivatives with naphthyl and p-dimethylaminophenyl substituents. Previously reported Q(F) values did not fit to our results.Öğe Photochemical reactions of alpha-terpinene and acenaphthene under concentrated sunlight(Scientific Technical Research Council Turkey, 2003) Avcibasi, N; Icli, S; Gilbert, Aalpha-Terpinene was successfully dehydrogenated to p-cymene in photocatalytic reaction with benzophenone and cupric ions under 40 suns concentrated sunlight irradiation, proving that photodehydrogenation reactions may be employed for the synthesis of fine chemicals under sunlight. Acenaphthene dehydrogenation under concentrated sunlight resulted in the minor formation of acenaphthylene and the quantitative formation of acenaphthenone when the solution was aerated. Stable benzylic-type radical intermediates are thought to lower the yield of dehydrogenation reactions.Öğe Photoinduced electron transfer-catalyzed processes of sulfoamino perylene diimide under concentrated sun light(Pergamon-Elsevier Science Ltd, 2006) Dincalp, H; Icli, SA new water-soluble perylene diimide derivative, N,N'-bis(12-sulfoaminododecyl)-3,4,9,10-perylenetetracarboxdiimide (SULFAPER), has been synthesized and characterized by visible, fluorescence, IR, H-1 and C-13 NMR, mass, CV and time resolved measurements. Its photophysical properties in aqueous and organic solutions have been described. The singlet energy levels of the synthesized compound have been found to be 57.8 kcal/mol and 59.2 kcal/mol in aqueous and methanol solution, respectively. The LUMO energy level of SULFAPER has been determined by solid state cyclic voltammetry, and found to be -3.60 eV. SULFAPER undergoes two electron reduction process (-0.64 V and -0.42 V) versus ferrocene. SULFAPER has an energy band gap of 2.56 eV. The absorption maximum of the synthesized compound gives bathochromic shift of 12 nut in water with respect to its visible spectrum in methanol solution. The fluorescence quantum yields of the compound are low both in water and methanol solution because of the aggregation effect. Time-resolved fluorescence measurements have showed that the fluorescence decay times of the SULFAPER are tau(1) = 4.1 ns and tau(2) = 0.8 ns in water, and tau(1) = 4.0 ns and tau(2) = 2.5 ns in methanol solutions. The aqueous solution of SULFAPER is stable under UV-VIS irradiation, but a slight loss of fluorescence emission (25%) has been detected at a rate of k(p) = 6.3 x 10(-5) s(-1) in methanol solution, which might be the result of either the quenching of fluorescence emission by reactive oxygen species, or by enhanced aggregation effect. SULFAPER-sensitized photooxidations of (E)-cinnamic acid and methyl acrylate have been found to give selective photoproduct formations under concentrated sun light in organic phase. (E)-cinnamic acid has been seen to favor photochemical E-Z isomerization and methyl acrylate has been seen to favor the formation of methyl 2-oxopropanoate. The quantum yield of (E)-cinnamic acid (Phi(CA)) under concentrated solar irradiation process has been calculated to be about 0.015, by the employment of an actinometry method developed by Erten and Icli. (c) 2005 Elsevier Ltd. All rights reserved.Öğe Photoinduced energy-electron transfer studies with naphthalene diimides(Elsevier Science Sa, 2000) Alp, S; Erten, S; Karapire, C; Koz, B; Doroshenko, AO; Icli, SSeven derivatives of naphthalene diimides, synthesized, have shown similar photophysical properties. Low fluorescence quantum yields (0.002-0.006) and short fluorescence lifetimes (5-18 ps) have suggested rapid intersystem crossing processes from excited singlet state. Quenching of fluorescence emissions of aromatic donor molecules, i.e. naphthalene, phenanthrene and pyrene, at rates reaching to diffusion Limits in acetonitrile (2-8 x 10(10) M-1 s(-1)), have proven the electron acceptor capacities of naphthalene diimides. Photooxydation of styrene to benzaldehyde, in presence of naphthalene diimide (NDI) molecule, is found to occur at similar rates with respect to perylene diimides. Addition of ferric and cupric ions to NDI, have enhanced the formation rate of benzaldehyde by about two-fold. Photooxidation of alpha-terpinene with naphthalene diimide, produced only p-cymene, no endoperoxide adduct was identified. Naphthalene diimides appear to produce no singlet oxygen, and photooxidation probably occurs on radical chain reactions of super oxide anion radical. But the electron transfer electron via excited triplet or singlet state, remains to be unclear. (C) 2000 Elsevier Science S.A. All rights reserved.Öğe Photooxidation of a conjugated diene by an exciplex mechanism: Amplification via radical chain reactions in the perylene diimide-photosensitized oxidation of alpha-terpinene(Amer Chemical Soc, 1998) Chen, LH; Lucia, LA; Gaillard, ER; Whitten, DG; Icil, H; Icli, SIrradiation of the perylene diimide (1) or 9,10-dicyanoanthracene (DCA) in the presence of alpha-terpinene (2-HH) in the presence of molecular oxygen leads to moderately efficient oxidation of 2-HH to p-cymene (2). Although 1 might be expected to photosensitize oxidations by the conventional "singlet oxygen" pathways, spectroscopic studies indicate that while oxygen can quench the fluorescent singlet of 1, no singlet oxygen is produced. 2-HH is also an efficient quencher of the fluorescent singlets of 1 and DCA and, for nonpolar solvents such as methylene chloride, in each case the quenching results in formation of an exciplex or contact radical ion pair. Under conditions where quenching by 2-HH to form the exciplex is complete, maximum quantum yields of 2 are obtained, thus indicating that the exciplex is the precursor to its formation. Nonproductive decay of the exciplex to starting materials is its major fate, thus the moderately high quantum efficiencies for formation of 2 require a mechanism involving amplification. Spin-trapping experiments suggest the role of hydroperoxy radicals and amplification by a radical chain mechanism involving these radicals and the intermediate 2-H-. is proposed. Possible paths for reaching these radicals from the exciplex are considered; either oxygen quenching of the exciplex or proton transfer within the exciplex followed by oxygen interception of the semireduced perylene diimide appear viable. For the reaction of DCA with 2-HH and oxygen, it is found that the much longer-lived exciplex undergoes quenching by oxygen.
