933982-96-8Relevant academic research and scientific papers
Color Tuning of Efficient Electroluminescence in the Blue and Green Regions Using Heteroleptic Iridium Complexes with 2-Phenoxyoxazole Ancillary Ligands
Benjamin, Helen,Liang, Jie,Liu, Yu,Geng, Yun,Liu, Xingman,Zhu, Dongxia,Batsanov, Andrei S.,Bryce, Martin R.
, p. 1810 - 1821 (2017/05/15)
A rational molecular design strategy for tuning the emission color of phosphorescent complexes by functionalization of the bis(2-phenylpyridine)(2-(2′-oxyphenyl)-2-oxazoline/oxazole)iridium(III) framework is reported. Five new complexes (2-6) have been synthesized in good yields and characterized by cyclic voltammetry, absorption, and photoluminescence studies, by time-dependent density functional theory (TD-DFT) calculations, and by single-crystal X-ray diffraction studies for complexes 2, 4, and 6. An interesting feature of the complexes is that the HOMO is localized on the Ir d-orbitals and the phenoxylate part of the “ancillary” ligand, while the LUMO is located on the pyridyl ring of the ppy ligands. A few other complexes containing 2′-oxyphenyl-2-oxazoline/oxazole ancillary ligands have been reported previously; however, until now there has not been a systematic investigation into manipulating this unusual frontier orbital distribution to tune the emissive properties. It is shown that exchanging the phenylpyridine (ppy) ligand for 2,4-difluoro-ppy gives a blue shift of 21-22 nm (from 1 to 2 and from 4 to 5), and the introduction of electron-withdrawing substituents (SO2Me, CF3) onto the phenoxylate ring of the (2′-oxyphenyl)-2-oxazole ligand results in a further blue shift of 13-20 nm. Combining these functionalizations gives sky-blue emission with λmaxPL 476 and 479 nm for complexes 5 and 6 in dichloromethane solution. The solution quantum yields of all the complexes are within the range ΦPL 0.42-0.73. The observed lifetimes (τobs = 1.52-3.01 μs) and spectral profiles are indicative of phosphorescence from a mixture of ligand-centered and MLCT excited states. (TD-)DFT calculations are in close agreement with the observed photophysical and electrochemical properties of the complexes. Phosphorescent organic light-emitting diodes have been fabricated using complexes 2, 3, 5, and 6 as the emitter, doped in a 4,4′-bis(N-carbazolyl)biphenyl host, giving efficient emission in the blue-green region. Notably, complex 5 gives λmaxEL 480 nm with a maximum brightness of 26150 cd m-2.
Synthesis and biological activity of novel 1,3-benzoxazine derivatives as K+ channel openers
Yamamoto, Satoshi,Hashiguchi, Shohei,Miki, Shokyo,Igata, Yumiko,Watanabe, Toshifumi,Shiraishi, Mitsuru
, p. 734 - 745 (2007/10/03)
A new series of 1,3-benzoxazine derivatives with a 2-pyridine 1-oxide group at C4 was designed to explore novel K+ channel openers. Synthesis was carried out by using a palladium(0)-catalyzed carbon-carbon bond formation reaction of imino-triflates with organozinc reagents and via a new one-pot 1,3-benzoxazine skeleton formation reaction of benzoylpyridines. The compounds were tested for vasorelaxant activity in tetraethylammonium chloride (TEA) and BaCl2-induced and high KCl-induced contraction of rat aorta to identify potential K+ channel openers, and also for oral hypotensive effects in spontaneously hypertensive rats. An electron- withdrawing group with the proper shape at C6 and a methyl or halogens group at C7 of the 1,3-benzoxazine nucleus were required for the development of optimal vasorelaxant and hypotensive activity. In particular, 2-(6-bromo-7- chloro-2,2-dimethyl-2H-1,3-benzoxazin-4-yl)pyridine 1-oxide (71) showed more potent vasorelaxant activity (EC50=0.14 μM) against TEA and BaCL2- induced contraction and longer-lasting hypotensive effects than cromakalim (1).
