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Article Citation - WoS: 14Citation - Scopus: 12Electrochemical Synthesis of New Conjugated Polymers Based on Carbazole and Furan Units(Elsevier Science Sa, 2015) Oguzturk, H. Esra; Tirkes, Seha; Onal, Ahmet M.In this study, synthesis of four new monomers; 3,6-di(2-furyl)-9H-carbazole (M1), 3,6-di(2-furyl)-9-ethyl-carbazole (M2), 2,7-di(2-furyl)-9-H-carbazole (M3), 2,7-di(2-furyl)-9-(tridecan-7-yl)-9H-carbazole (M4), was achieved via Stifle cross-coupling reaction. The monomers were electrochemically polymerized, via repetitive cycling in acetonitrile-tetrabutylammonium hexafluorophosphate electrolytic medium. Optical and electrochemical properties of the monomers and their corresponding polymers were investigated and it was found that optical properties show slight variations depending on the connectivity between the carbazole and furan moieties. However, all the monomers synthesized in this work exhibited an irreversible oxidation peak at around 1.0 V. Electrochemically obtained polymer films, on the other hand, exhibited quasi-reversible redox behavior due to doping/dedoping of the polymers which was accompanied by a reversible electrochromic behavior. Their band gap values (E-g) were elucidated utilizing spectroelectrochemical data and it was found that polymers obtained from 2,7-substituted carbazole derivatives have slightly lower band gap values. Furthermore, scanning electron micrographs were used for morphological examinations. (C) 2015 Elsevier B.V. All rights reserved.Article Citation - WoS: 21Citation - Scopus: 21Synthesis and Electro-Optical Properties of New Conjugated Hybrid Polymers Based on Furan and Fluorene Units(Pergamon-elsevier Science Ltd, 2013) Gunes, Arzu; Cihaner, Atilla; Onal, Ahmet M.A novel series of hybrid monomers containing furan and fluorene units, namely 2-(2-(furan-2-yl)-9H-fluoren-7-yl)furan (FFF), 2,7-di(furan-2-yl)-9H-fluoren-9-one (FOF) and 2-(2-(furan-2-yl)-9,9-dihexyl-9H-fluoren-7-yl)furan (FHF), was synthesized and their electrochemical polymerization was achieved via potential cycling. Optical and electrochemical properties of the polymers, poly(2-(2-(furan-2-yl)9H-fluoren-7-yl)furan (PFFF), poly(2,7-di(furan-2-yl)-9H-fluoren-9-one) (PFOF) and poly(2-(2-(furan2-yl)-9,9-dihexyl-9H-fluoren-7-yl)furan) (PFHF), were investigated and it was found that polymer films exhibited quasi-reversible redox behavior (E-p(ox) =0.92V for PFFF, E-p(ox) = 1.08V for PFOF and E-p(ox) = 0.99V for PFHF) accompanied with a reversible electrochromic behavior, yellow to dark blue for PFFF, orange to green for PFOF and orange to green for PFHF. Their band gap values (E-g) were found to be 2.49, 2.32 and 2.61 eV for PFFF, PFOF and PFHF, respectively. (C) 2012 Elsevier Ltd. All rights reserved.Article Citation - WoS: 18Citation - Scopus: 19Effect of Furan, Thiophene and Selenophene Donor Groups on Benzoselenadiazole Based Donor-Acceptor Systems(Elsevier Science Sa, 2016) Karabay, Lutfiye Canan; Karabay, Bads; Karakoy, Merve Serife; Cihaner, AtillaA series of the monomers called 4,7-di(furan-2-yl)benzo[c][1,2,5]selenadiazole (OSeO), 4,7-di(thiophen-2-yl)benzo[c]11,2,5]selenadiazole (SSeS) and 4,7-di(selenophen-2-yl)benzo[c][1,2,5]selenadiazole (SeSeSe) was synthesized via a donor-acceptor-donor (D-A-D) approach. Benzoselenadiazole was used as an acceptor unit and furan, thiophene and selenophene were used as donor units. The effects of chalcogen atoms (0, S, and Se) in furan, thiophene and selenophene were investigated systematically on the properties of the monomers and their corresponding polymers (POSeO, PSSeS and PSeSeSe, respectively), which were polymerized electrochemically via potentiodynamic or potentiostatic methods. The monomers OSeO, SSeS and SeSeSe exhibited low oxidation potentials of 1.15, 1.25 and 1.19 V vs. Ag/AgCl, respectively. Intramolecular charge transfer interaction between donor and acceptor units was demonstrated from the emission spectra of the monomers. Also, the optical studies showed that the ambipolar and electrochromic polymers POSeO, PSSeS and PSeSeSe have low band gaps of 1.57, 1.47 and 1.45 eV, respectively. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 10Citation - Scopus: 9A Computational Study on 4,7-Di(furan Monomer and Its Oligomers(Springer, 2014) Kayi, Hakan; Kayı, Hakan; Kayı, Hakan; Chemical Engineering; Chemical EngineeringThe energy gap, Eg, between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels that determines the electronic and optical properties of 4,7-di(furan-2yl)benzo[c][1,2,5]thiadiazole (FSF) polymer is calculated by performing quantum chemical calculations. First, we theoretically investigated the most stable conformers of FSF monomer and its corresponding oligomers at the B3LYP/6-31G(d) and B3LYP/LANL2DZ levels of theory. We reveal the theoretical molecular structure of this very recently synthesized novel monomer and its oligomers for the first time in the literature. Our results from the B3LYP/6-31G(d) calculations indicated that FSF polymer has a low HOMO-LUMO gap of 1.55 eV to be in good agreement with the experiments. Experimental design and synthesis of novel conjugated polymers require time-consuming and expensive procedures. The findings from this study are promising for the use of computational methods in the design of the novel conjugated polymers, and help to narrow the materials to be used in design and synthesis of conjugated polymers with desired properties.Article Citation - WoS: 9Citation - Scopus: 10A Theoretical Investigation of 4,7-Di(furan Donor-Acceptor Type Conjugated Polymer(Elsevier, 2015) Kayi, Hakan; Elkamel, AliQuantum chemical calculations are performed using density functional theory (DFT) to investigate the HOMO-LUMO energy gap of the 4,7-di(furan-2-yl)benzo[c][1,2,5]selenadiazole-based (FSeF) donor-acceptor type conjugated polymer which ascertains the optoelectronic properties and plays a crucial role, especially in polymeric solar cell applications. In this paper, the most stable conformers of the FSeF monomer and its corresponding oligomers are investigated at the B3LYP/Def2TZV and B3LYP/LANL2DZ levels of theory, and their molecular structures are revealed. The band gap of the polymer is determined by linear-fitting and extrapolation of the DFT data. This gap is found to be 1.44 eV and 1.45 eV by the B3LYP/Def2TZV, and B3LYP/LANL2DZ with PCM calculations, respectively. Our theoretical findings related to the band gap of the FSeF polymer (PFSeF) are in good agreement with other experimental studies in the literature and, hence, the theoretical methods used in this study are promising for the design of similar donor-acceptor type novel conjugated polymers. (C) 2014 Elsevier B.V. All rights reserved.Article Citation - WoS: 16Citation - Scopus: 16Synthesis and electropolymerization of thieno[3,4-c]pyrrole-4,6-dione based donor-acceptor-donor type monomers(Elsevier Science Sa, 2020) Cakal, Deniz; Cihaner, Atilla; Onal, Ahmet M.Two monomers containing thieno [3,4-c]pyrrole-4,6-dione (TP) acceptor units, namely 5-(2-ethylhexyl)-1,3-di (furan2-yl)-4H-thieno [3,4-c]pyrrole-4,6(5H)-dione (FTPF) and 5-(2-ethylhexyl)-1,3-di (selenophen-2-yl)-4H-thieno[3,4-c] pyrrole-4,6(5H)-dione (STPS), were synthesized via donor-acceptor-donor approach. Under the same template structure, the effect of heteroatom of the donor unit on redox and optical properties of the monomers and their corresponding polymers obtained via electrochemical method (PFTPF and PSTPS) were investigated. The results were also compared to their thiophene analogues 5-(2- ethylhexyl)-1,3-di (thiophen-2-yl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (TTPT) as the monomer and PTTPT as the polymer. Three monomers exhibited dual absorption bands one at high energy region due to the pi-pi* transition and the other one at low energy region which might be attributed to intramolecular charge transfer (ICT). An increase in ICT and a decrease both in the band gap and quantum yield was observed with increasing size of the heteroatomof the donor units. The oxidation potentials of the monomers and that of their corresponding polymer films were found to follow the order of decreasing aromatization energy from thiophene to furan (i.e thiophene > selenophene > furan). Also, heavy-atom substitution (PSTPS) effect showed itself by narrowing the optical band gap of the neutral state electrochromic polymer films: 1.90 eV for PFTPF, 1.82 eV for PTTPT and 1.76 eV for PSTPS.Article Citation - WoS: 13Citation - Scopus: 13Effect of the Donor Units on the Properties of Fluorinated Acceptor Based Systems(Elsevier Sci Ltd, 2021) Cakal, Deniz; Akdag, Akin; Cihaner, Atilla; Onal, Ahmet M.A new series of monomers in the donor-acceptor-donor array, namely 5-fluoro-4,7-di(furan-2-yl)benzo[c][1,2,5] thiadiazole (F2BT-F), and 5-fluoro-4,7-di(selenophen-2-yl)benzo[c][1,2,5] thiadiazole (S2BT-F), bearing 5-fluorobenzo[c][1,2,5]-thiadiazole as the acceptor moiety and furan and selenophene as the electron donating groups was synthesized and polymerized electrochemically. To compare heteroatom effect, thiophene analogue of newly synthesized (FBT)-B-2-F and S2BT-F namely, (5-fluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5] thiadiazole (T2BT-F)) and its corresponding polymer were also synthesized. Effect of donor units on the electrochemical and optical properties of fluorinated acceptor based systems was investigated in terms of the effect of different sized heteroatoms in five-membered rings on the dihedral angle and planarity. Theoretical calculations also suggested a deviation from planarity upon fluorination. Moreover, electrochemically obtained polymers possess low bandgap values (1.62 eV-1.68 eV for PF2BT-F and PS2BT-F, respectively) and exhibited electrochromic properties with relatively low switching times.
