476360-83-5Relevant academic research and scientific papers
Novel fluorescent carbazolyl-pyridinyl alternating copoloymers: Synthesis, characterization, and properties
Pan, Xiaoyong,Liu, Shouping,Chan, Hardy S.O.,Ng, Siu-Choon
, p. 7629 - 7635 (2005)
A novel series of AB-type polymers comprised of alternating carbazolyl and pyridinyl units were synthesized using palladium(0)-catalyzed Suzuki cross-coupling reaction in good to high yields. In this series of alternating copolymers, the electron-rich 2,7-(N-(2-ethylhexyl)carbazolyl) unit was used as a light-emitting unit, and the electron-deficient unit of pyridinyl was introduced to tune the wavelength of the emitting light and improve their electron transportation. These polymers were characterized by 1H NMR and 13C NMR, gel permeation chromatography (GPC), thermal analysis, UV-vis, fluorescence spectroscopy, and cyclic voltammetry (CV). The glass transition temperature of these polymers ranged from 120 to 150°C, and the polymers showed high thermal stability with decomposition temperatures in the range 370-400°C in nitrogen. The different linkage pattern of pyridinyl units in the copolymer backbone has a significant effect on the electronic and optical properties in solution and in film phases. For pure blue emission and prevention of aggregation of polymer chain, the meta-linkage pattern (3,5-and 2,6-linkage) of pyridinyl units in the polymer backbone is more favorable than the para-linkage pattern (2,5-linkage) of the pyridinyl units. The cyclic voltammetry (CV) results indicate that these polymers with pyridinyl units possess lower LUMO energy levels for an easy electron injection from a cathode than poly[3,6-(N-octyl)carbazolyl] and its derivatives do.
Multinuclear 2-(Quinolin-2-yl)quinoxaline-Coordinated Iridium(III) Complexes Tethered by Carbazole Derivatives: Synthesis and Photophysics
Zhu, Xiaolin,Liu, Bingqing,Cui, Peng,Kilina, Svetlana,Sun, Wenfang
, p. 17096 - 17108 (2020/11/30)
Five mono/di/trinuclear iridium(III) complexes (1-5) bearing the carbazole-derivative-tethered 2-(quinolin-2-yl)quinoxaline (quqo) diimine (N^N) ligand were synthesized and characterized. The photophysical properties of these complexes and their corresponding diimine ligands were systematically studied via UV-vis absorption, emission, and transient absorption (TA) spectroscopy and simulated by time-dependent density functional theory. All complexes possessed strong well-resolved absorption bands at 400 nm that have predominant ligand-based 1π,π? transitions and broad structureless charge-transfer (1CT) absorption bands at 400-700 nm. The energies or intensities of these 1CT bands varied pronouncedly when the number of tethered Ir(quqo)(piq)2+ (piq refers to 1-phenylisoquinoline) units, πconjugation of the carbazole derivative linker, or attachment positions on the carbazole linker were altered. All complexes were emissive at room temperature, with 1-3 showing near-IR (NIR) 3MLCT (metal-to-ligand charge-transfer)/3LLCT (ligand-to-ligand charge-transfer) emission at ～710 nm and 4 and 5 exhibiting red or NIR 3ILCT (intraligand charge-transfer)/3LMCT (ligand-to-metal charge-transfer) emission in CH2Cl2. In CH3CN, 1-3 displayed an additional emission band at ca. 590 nm (3ILCT/3LMCT/3MLCT/3π,π? in nature) in addition to the 710 nm band. The different natures of the emitting states of 1-3 versus those of 4 and 5 also gave rise to different spectral features in their triplet TA spectra. It appears that the parentage and characteristics of the lowest triplet excited states in these complexes are mainly impacted by the πsystems of the bridging carbazole derivatives and essentially no interactions among the Ir(quqo)(piq)2+ units. In addition, all of the diimine ligands tethered by the carbazole derivatives displayed a dramatic solvatochromic effect in their emission due to the predominant intramolecular charge-transfer nature of their emitting states. Aggregation-enhanced emission was also observed from the mixed CH2Cl2/ethyl acetate or CH2Cl2/hexane solutions of these ligands.
