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    Direct Photopatterning of BODIPY-Based Small Molecules via Thiol-ene Click Chemistry
    (John Wiley and Sons Inc, 2023) Özdemir, Mücahit; Altınışık, Sinem; Ömeroğlu, İpek; Köksoy, Baybars; Durmuş, Mahmut; Yalçın, Bahattin; Koyuncu, Sermet
    We demonstrate a BODIPY-based small molecule photopatterned surface by thiol-ene click chemistry at room temperature utilizing only 366 nm UV light. The resulting cross-linked polymer exhibits porous surfaces according to AFM and TEM results. A dramatic blue shift occurred in absorption spectra and the photoluminescence was also intensified as a result of crosslinking. Optical and electrochemical results are compatible with the DFT calculations. The obtained results prove that the photopatterned BODIPY-based material can be easily and inexpensively applied in multilayer optoelectronic devices.
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    Electron-Donating and Electron-Withdrawing Subunit Effects on Coumarin-BODIPY Dyads: Optical and Electrochemical Properties and Molecular Interactions
    (John Wiley and Sons Inc, 2023) Köksoy, Baybars; Özdemir, Mucahit; Altınışık, Sinem; Zorlu, Yunus; Yalcın, Bahattin; Durmuş, Mahmut; Koyuncu, Sermet
    In this study, a series of coumarin-BODIPY molecules were synthesized using a Sonogashira cross-linking reaction. The effects of electron withdrawing and electron donating moieties on electrochemical and optical properties were supported by results of density functional theory calculations, and energy transfer mechanisms were investigated. The band gap value decreased from 2.0 eV to 1.6 eV due to reversible oxidation of the extra dimethylamino subunit at lower potential. Besides, characteristics of the crystal structures were investigated with single-crystal X-ray diffraction, and crystallinity was supported by differential scanning calorimetry. In addition, when the thin film surface morphologies were examined, it was clearly observed that the N,N-dimethylamino group on the coumarin-BODIPY dyad (B3) formed large-scale domains due to its crystalline behavior. As a result, Förster-type energy transfer was observed for coumarin-BODIPY dyads containing different electron withdrawing and donating subunits.
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    Symmetrical and Asymmetrical Thiophene-Coumarin-Based Organic Semiconductors
    (American Chemical Society, 2024) Altınışık, Sinem; Özdemir, Mücahit; Kortun, Arzu; Zorlu, Yunus; Yalçın, Bahattin; Köksoy, Baybars; Koyuncu, Sermet
    Organic semiconductors are a valuable material class for optoelectronic applications due to their electronic and optical properties. Four new symmetric and asymmetric thiophene-coumarin derivatives were designed and synthesized via Pd-catalyzed Suzuki and Stille Cross-Coupling reactions. Single crystals of all synthesized thiophene-coumarin derivatives were obtained, and π···π interactions were observed among them. The π···π interactions were supported by UV–vis, transmission electron microscopy, and atomic force microscopy analyses. The photophysical and electrochemical properties of the coumarins were investigated and supported by density functional theory studies. Fluorescence quantum yields were recorded between 36 and 66%. Moreover, mega Stokes shifts (175 nm or 8920 cm–1) were observed in these new chromophore dyes. The emission and absorption colors of the thiophene-coumarin compounds differed between their solution and film forms. Electrochemically, the highest occupied molecular orbital levels of the coumarins increased with the 3,4-ethylenedioxythiophene group, leading to a narrowing of the band gap, while the phenyl bridge weakened the donor–acceptor interaction, expanding the band gap.
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    Synthesis and photovoltaic properties of novel ferrocene-substituted metallophthalocyanines
    (Royal Society of Chemistry, 2022) Özdemir, Mücahit; Köksoy, Baybars; Kuruca, Halid; Altindal, Ahmet; Durmuş, Mahmut; Koyuncu, Sermet; Yalçin, Bahattin
    In this paper, a series of new metallophthalocyanines, including ferrocene groups, were designed, synthesized and, characterized, and their photovoltaic properties were investigated as alternative electron-donor materials in bulk heterojunction (BHJ) solar cells. These products were synthesized by a Sonogashira cross-coupling reaction between tetraiodophthalocyanine and ethynyl ferrocene. The newly synthesized phthalocyanines (4-6) were characterized by FT-IR, UV-Vis, H-1 NMR, and MALDI-TOF spectroscopic methods and elemental analysis. The electrochemical characterizations were carried out by cyclic voltammetry as well as differential pulse voltammetry. Density functional theory calculations were realized to prove the charge separation between ferrocene as an electron-donor and the phthalocyanine ring as an acceptor. According to UV-Vis measurements, a 25 nm red-shift was observed for complex 4 compared with complexes 5 and 6. Finally, the photovoltaic performance of these compounds used as an electron-donor moiety in a BHJ device were investigated. A function of different blend ratios was tested by fabricating a series of BHJ devices with the architecture of FTO/PEDOT:PSS/4-6: PCBM blend/Ag with an identical thickness of the active layer. The results indicated that the photovoltaic conversion efficiency of BHJ devices exhibited a strong blend-ratio dependence. The maximum power conversion efficiency was obtained by 5-based devices, as 3.65%, with a blend ratio of 1.5 : 1.0 under standard AM 1.5 illumination.
  • Küçük Resim
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    The Role of Electron-Donating Subunits in Cross-Linked BODIPY Polymer Films
    (John Wiley and Sons Inc, 2023) Özdemir, Mücahit; Köksoy, Baybars; Yalçın, Bahattin; Koyuncu, Sermet
    A new method for synthesizing cross-linked 4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPYs) using a radical-based thiol-ene click reaction is developed. This method is simple, efficient, and cost-effective, and it produces polymers with unique optical, electrochemical, and surface morphology properties. Significant blue shifts in absorption and photoinduced electron transfer in emissions are observed in the cross-linked BODIPY thin films. Cross-linking also leads to the restriction of conjugation, which results in the breakage of the terminal vinyl group, an increase in the oxidation potential, and a slight upshift in the HOMO position. As a result, the electrochemical band gap is widened from 1.88 to 1.94 eV for polymer bearing N,N-dimethylamino-BODIPY and from 1.97 to 2.02 eV for polymer bearing N,N-diphenylamino-BODIPY moieties. Monomer thin films form planar surfaces due to crystallinity, while amorphous cross-linked BODIPY polymers form more rough surfaces. Additionally, photopatterning on the film surface is successfully performed using different patterned masks. This new method for synthesizing cross-linked BODIPYs has the potential to be used in a variety of applications, including organic electronics, bioimaging, and photocatalysis.