Browsing by Author "Aydemir, Murat"

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    High efficiency OLEDs based on anthracene derivatives: The impact of electron donating and withdrawing group on the performance of OLED
    (Elsevier, 2016-03) Aydemir, Murat; Haykır, Gülçin; Battal, Ahmet; Jankus, Vygintas; Sugunan, Sunish K.; Dias, Fernando B.; Al-Attar, Hameed; Türksoy, Figen; Monkman, Andrew P.; Tavaslı, Mustafa; Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-9466-1111; AAB-1630-2020; 6506308760
    New well-defined bulky anthracene derivatives with side groups having electron donating or withdrawing properties 8a-d were synthesized. The compounds contain substituted anthracene as the central core attaching 2-(4-(2-pyridinyl)-phenyl)vinyl and 4-R-phenyl [R:H (a), OMe (b) and CF3 (c), N(Ph)(2) (d)] groups at 9- and 10-positions. The impact of electron donating, withdrawing and neutral groups and their influence on the molecules photophysical, charge transfer (CT), triplet transfer (TT) and triplet-triplet annihilation (TTA) properties has been investigated. Based on the photophysical studies the most promising molecule (8d) has been selected and high efficiency fluorescent OLEDs with EQE at very low current efficiency reaching 7% were obtained. The value at low current density implies a Triplet Fusion (TF) contribution of 45%, very close to the maximum theoretical value of 50% when only the singlet decay channel is open to TTA, however we believe that in this case both TTA and TADF contribute to the triplet harvesting to yield high EQE values, and this mixed triplet harvesting arises through the heterogeneity of the films. At high current density a brightness of 20000 cd/m(2) was achieved and it is assigned partially to the material crystallisation.
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    Synthesis of biscyclometalated iridium(III) acetylacetonate complexes via a 15 min bridge-splitting reaction, their characterisations and photophysical properties
    (Elsevier, 2017-09-19) Aydemir, Murat; Dos Santos, Paloma L.; Monkman, Andrew P.; Altınölçek, Nuray; Tavaslı, Mustafa; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-9466-1111; AAB-1630-2020; 56955836600; 6506308760
    Chloro-bridged diiridium(III) complexes (4a and 4b) were subjected to a bridge-splitting reaction with acetylacetone and sodium carbonate in 2-ethoxyethanol. The reaction was complete within 15 min and two novel biscyclometalated iridium(III) acetylacetonate complexes (5a and 5b) were successfully obtained in 41% and 63%, respectively. Complexes (5a and 5b) were fully characterised by H-1, C-13 NMR, FT-IR and elemental analysis. UV-Vis spectra of complexes (5a and 5b) showed two absorption bands: a strong one appears below 400 nm due to ligand-centered (LC, pi-pi*) transitions and the weak one arises between 400 and 600 nm due to metal-to-ligand charge-transfer (MLCT, d-pi*) transitions. The emission of the complexes (5a and 5b) arises in the red region of the spectrum, emitting ca. 675 nm for 5a and ca. 625 nm for 5b. A short emission lifetime (62 ns) for complex 5a indicates emission originates from (LC)-L-3 transitions. However longer emission lifetime (657 ns) for complex 5b confirms that the emission totally results from (MLCT)-M-3 transitions.
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    Synthesis, thermal and optical properties of a novel bis(2-(4-dicyanovinylphenyl) pyridinato-N, C2) iridium(acetylacetonate)
    (Elsevier, 2015-10-09) Aydemir, Murat; Abay, Bahattin; Monkman, Andrew P.; Altınölçek, Nuray; Tavaslı, Mustafa; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-9466-1111; AAB-1630-2020; 56955836600; 6506308760
    Bis(2-(4-formylphenyl) pyridinato-N, C2) iridium(acetylacetonate) (5) was subjected to a Knoevenagel reaction with malononitrile in dichloromethane in the presence of catalytic amount of pyrrolidine. This gave successfully a novel bis(2-(4-dicyanovinylphenyl) pyridinato-N, C2) iridium(acetylacetonate) (6) in good yield (83%). Complex 6 was fully chracterised by H-1, C-13 NMR, FT-IR, elemental analysis. Complex 6 showed a strong ligand centred (LC) absorption band at 355 nm (epsilon 56490 L mol (1) cm (1)) and weak metal-to-ligand charge transfer (MLCT) bands at 445 (epsilon 4154 L mol (1) cm (1)) and 535 nm (epsilon 2606 L mol (1) cm (1)). Complex 6 loses its acac moiety between 248 and 336 Alpha degrees C (under N-2 atmosphere) and emits a red light at 695 nm with a large Stokes shift (160 nm).