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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.
  • Küçük Resim
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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.