448955-87-1Relevant articles and documents
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.
Structure-properties relationship of the derivatives of carbazole and 1,8-naphthalimide: Effects of the substitution and the linking topology
Gudeika, Dalius,Grazulevicius, Juozas Vidas,Volyniuk, Dmytro,Butkute, Rita,Juska, Gytis,Miasojedovas, Arunas,Gruodis, Alytis,Jursenas, Saulius
, p. 239 - 252 (2015/03/31)
Nine compounds having electron-accepting 1,8-naphthalimide and electron-donating carbazole moieties were synthesized employing palladium-catalyzed C-N and C-C coupling reactions and characterized by the thermal methods, absorption and emission spectrometry, electrochemical and photoelectrical tools. The synthesized compounds possess high thermal stability with the 5% weight loss temperatures being in the range of 351-476 °C. Most of the synthesized compounds are capable of glass formation with glass transition temperatures ranging from 30 to 87 °C. The cyclic voltammetry measurements showed that the solid state ionization potentials values of the carbazole and 1,8-naphthalimide derivatives range from 5.46 eV to 5.76 eV and the electron affinities values range from -3.04 eV to -2.92 eV. Dilute solutions of the 3- and 3,6-naphthalimide-substituted derivatives of carbazole in polar solvents were found to emit in the green region with quantum yields ranging from 0.66 to 0.83, while in the solid state fluorescence quantum yields were found to be in the range of 0.01-0.45. ((E)-9-(((N-(2-ethylhexyl)-1,8-naphthalimide)-4-yl)ethenyl)-9H-carbazole) exhibited efficient fluorescence in the solid state with quantum yield as high as 0.45. The effects of the linking topology of the chromophores and of the incorporated alkyl substituents on the thermal, optical, and photoelectrical properties of the synthesized donor-acceptor compounds are analyzed. The impact of the ground state intramolecular twisting of the carbazole and naphthalimide moieties induced by the substituents resulting in significant variation in the rates of radiative and nonradiative excitation deactivation is revealed.
