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백창현,김진형,나수원,최민수,강상욱,손호진 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
To evaluate the efficacy of ortho-aryllation in the second coordination sphere of octrahedral iridium complex, a series of homoleptic NHCbased Ir(C^C<sup>R</sup>)<sub>3</sub>-type complexes were desgined and prepared by introducing various substituents (R = H, Me, Ph, MePh, and diMePh) at the ortho-position of the aryl unit of orthometalling phenyl group. In solution, unnoticiable increase of emission quantum yields was observed within the variation of the ortho-substituent of sterically demanding side-branch, a -diMePh group, showing the radiative quantum yield of m-Ir(C^C<sup>diMePh</sup>)<sub>3</sub> (Ф<sub>PL</sub> = 1.9%) being higher than that of the pristine carbene-based m-Ir(C^C<sup>H</sup>)<sub>3</sub> (Ф<sub>PL</sub> = 1.2%).
Influence of bulky substituents on the photophysical properties of homoleptic iridium(III) complexes
백창현,김진형,나수원,이대한,조대원,강상욱,손호진 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
A new series of homoleptic cyclometalated iridium(III) complexes based on a phenylpyridine (ppy) ligand containing bulky substituents have been synthesized and characterized. The phosphorescence behavior of the Ir complexes is investigated by steady-state and time-resolved emission spectroscopic techniques. Comparison of the results with those of the reference Ir(ppy)<sub>3</sub> reveals that the emission color and photophysical properties of other Ir complexes are influenced by the electron-donating groups (-CH<sub>3</sub> and phenyl derivatives) attached to the ppy ligand. In particular, systematic red-shifts are observed by increasing the electron-donating ability. The emission spectrum of Ir(Me-ppy)<sub>3</sub>, having a small electron-donating -CH<sub>3</sub> group, is redshifted; however, the emission quantum yield is low and the nonradiative decay constant is large.
백창현,홍주화,위명용,김기영,이동복 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.8
The oxidation behavior of TiN, TiCN and CrN coatings sputtered on a steel substrate was investigated at 850℃ in air. Both TiN and TiCN oxidized to Tio₂ while CrN oxidzed to Cr₂O₃. The oxidation resistance decreased in the order of CrN, TiN and TiCN. During oxidation, the outward diffusion of substrate elements such as Fe, Si occurred to a certain degree. The enrichment of substrate element of Cr at the oxide scale and the depletion of nitrogen at the lower part of the unoxidized CrN coating were observed.
백창현,이승표,장미숙,박영석 대한구강해부학회 2012 대한구강해부학회지 Vol.33 No.1
Inferior a1veo1ar nerve (IAN) is the branch of mandibu1ar division of trigemina1 nerve and is one of the most important nerves in oromaxillary area. In many clinica1 situations. there is the possibi1ity of IAN being injured. Thus, the anatomic properties of IAN were studied first. We a1so studied the reasons of IAN l nJ Ury, the diagnostic methods which he1p determine the extent of injury and the methods for treatment of injured nerve. We reviewed the bio1ogica1 changes of injured IAN. IAN cou1d be damaged from 10wer third mo1ar extraction or imp1ant surgery. When IAN is injured, all the parts of IAN including cell body, axon , Schwann cell and nerve ending wou1d be changed for the nerve regeneration. Schwann cells seem to have a very important ro1e in this process. There are severa1 methods for eva1uating the extent of IAN injury: static 1ight touch test , dynamic 1ight touch test , two point discrimination test. therma1 sense test. e1ectrophysio1ogic test and digita1 infrared therma1 imaging. Injured IAN can be treated by pharmaco1ogica1 therapies. physica1 therapies. and surgica1 interventions such as anastomosis and nerve graft. Recently. the studies on new intervention of using nerve conduits or Schwann cells in IAN repair are on progress.
백창현,김진형,나수원,이대한,조대원,강상욱,손호진 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Incorporation of an electron-withdrawing -SO<sub>2</sub>CF<sub>3</sub> (σ<sub>p</sub> = 0.96) substituent in cyclometalating C^N-phenyl pyridine (ppy) ligand resulted in an expected blue-shifted phosphorescence derived from homoleptic Ir(C^N)<sub>3</sub> complexes [λ<sub>em</sub> = 457 nm for Ir(ppySCF<sub>3</sub>)<sub>3</sub> at 77 K]. Its heteroleptic counterpart, modified by a pyrazolyl borate LX ligand, Ir(ppySCF<sub>3</sub>)<sub>2</sub>(bor) exhibited further blue-shifted phosphorescence (λ<sub>em</sub> = 455 nm at 77 K). Density-functional theory (DFT) calculations supported the efficacy of electron-withdrawing capability of the SO<sub>2</sub>CF<sub>3</sub> substituent lowering HOMO energy and obtained a widened band-gap and resumed a deep blue emission. Stronger σ-bond of C<sub>Ph</sub>-Ir correlates well to a higher emission quantum yield of Ir(ppySCF<sub>3</sub>)<sub>3</sub> than that of Ir(ppySF)<sub>3</sub>, the reported fluoro sulfonyl (-SO<sub>2</sub>F) derivative which is devoid of a <sup>3</sup>MC deactivation manifold resulting in the quantum yields (Ф<sub>PL</sub>) of Ir(ppySCF<sub>3</sub>)<sub>3</sub> and Ir(ppySF)<sub>3</sub> to be 0.89 and 0.72, respectively.