• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.42-48
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• 2013

Potassium N-heterobiaryltrifluoroborates were successfully prepared via a selective Cu-catalyzed C-N coupling reaction. The $BF_3K$ moiety was well tolerated under the reaction conditions involving CuI and dimethyl-ethylenediamine (DMEDA) in the presence of DMSO. The Pd-catalyzed Suzuki-Miyaura cross couplings of potassium N-heterobiaryltrifluoroborates with bromoarenes were studied to prepare the N-heterotriaryl compounds. Moreover, homocoupling, iodination, and hydroxylation of potassium N-heterobiaryltrifluoroborates provided the corresponding products in high yields.

• Bulletin of the Korean Chemical Society
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• v.20 no.4
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• pp.422-426
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• 1999

The Grignard reactions of bis(chloromethyl)dimethylsilane (1) with trimethylchlorosilane (2) in THF give both the intermolecular C-Si coupling and intramolecular C-C coupling products. At beginning stage, 1 reacts with Mg to give the mono-Grignard reagent ClCH2Me2SiCH2MgCl (1) which undergoes the C-Si coupling reaction to give MC2Si(CH2SiMe3)2 3, or C-C coupling to a mixture of formula Me3SiCH2(SiMe2CH2CH2)nR1 (n = 1, 2, 3, ..; 4a, R1I = H: 4b, R1 = SiMe3). In the reaction, two reaction pathways are involved: a) Ⅰ reacts with 2 to give Me3SiCH2SiMe2CH2Cl 6 which further reacts with Mg to afford a Me2SiCH2Mel-SiCH2MgCl (Ⅱ) or b) I cyclizes intramolecularly to a silacyclopropane intermediate A, which undergoes a ring-opening polymerization by the nucleophilic attack of the intermediates I or Ⅱ, followed by the termination reaction with H2O and 2, to give 4a and 4b, respectively. As the mole ratio of 2/1 increased from 2 to 16 folds, the formation of product 3 increased from 16% to 47% while the formation of polymeric products 4 was reduced from 60% to 40%. The intermolecular C-Si coupling reaction of the pathway a becomes more favorable than the intramolecular C-C coupling reaction of the pathways b at the higher mole ratio of 2/1.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.176.1-176.1
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• 2014

Graphene has attracted an increasing attention due to its extraordinary electronic, mechanical, and thermal properties. Especially, the two dimensional (2D) sheet of graphene with an extremely high surface to volume ratio has a great potential in the preparation of multifunctional nanomaterials, as 2D supports to host metal nanoparticles (NPs). Copper oxide is widely used in various areas as antifouling paint, p-type semiconductor, dry cell batteries, and catalysts. Although the copper oxide(II) has been well known for efficient catalyst in C-N cross-coupling reaction, copper oxide(I) has not been highlighted. In this research, CuO and Cu2O nanoparticles (NPs) dispersed on the surface of grapehene oxide (GO) have been synthesized by impregnation method and their morphological and electronic structures have been systemically investigated using TEM, XRD, and XAFS. We demonstrate that both CuO and Cu2O on graphene presents efficient catalytic performance toward C-N cross coupling reaction. The detailed structural difference between CuO and Cu2O NPs and their effect on catalytic performance are discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.138.2-138.2
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• 2013

Copper oxide is a multi-functional material being used in various research areas including catalysis, electrochemical materials, oxidizing agents etc. Among these areas, we have synthesized and utilized graphene based copper oxide nanocomposites (CuOx/Graphene) for the catalytic applications (C-N cross coupling reaction). Briefly, Cu precursors were anchored on the graphite oxide(GO) sheets being exfoliated and oxidized from graphite powder. Two different crystalline structures of Cu2O and CuO on graphene and GO were prepared by annealing them in Ar and O2 environments, respectively. The morphological and electronic structures were systemically investigated using FT-IR, XRD, XPS, XAFS, and TEM. Here, we demonstrate that the catalytic performance was found to depend on oxidative states and morphological structures of CuOx graphene nanocomposites. The relationship between the structure of copper oxides and catalytic efficiency toward C-N cross coupling reaction will be discussed.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.25-35
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• 2013

The intramolecular magnetic coupling constant (J) values of diradical-based magnet models (S1-S5) were studied using unrestricted density functional theory. The model systems were designed with series of oxoverdazyl radicals (o-Ver(N) and o-Ver(C)) linked through a benzene coupler. They were divided according to either connectivity of the radical (C or N) or geometrical topology (meta- and para-) of benzene coupler. Reasonable relationship was found between spin density distribution and sign of J value. With our results we determined ferromagnetic (positive J value) and antiferromagnetic (negative J value) interactions. J values were also calculated along the twisting movement by the scan of dihedral angles between the radical and the coupler. An overall trend was found as absolute value of J decreased over increasing torsion angles.

• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.539-546
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• 2003

The GaN/sapphire layered structure is a potential candidate for high frequency devices due to high acoustic velocity of sapphire. Generally, the GaN thin films are epitaxially grown on c, a, and r-plane sapphire substrates. In this study, wave equations of GaN/sapphire structure were calculated according to crystallographic relationship between GaN layer and sapphire substrate. On each plane, the shear velocity was changed by the kH of GaN layer and propagation direction on sapphire substrate. We found electromechanical coupling constant of r-plane was better than the others. As a result, elastic stiffness and electromechanical coupling constant of materials are affected by a cut and an orientation of substrate. GaN/r-plane sapphire structure is more advantageous for high frequency SAW devices.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1703-1707
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• 2018

Ferromagnetic ${\tau}-phase$ $Mn_{54}Al_{46}C_{2.44}$ particles were synthesized, and its composites with commercial $Sm_2Fe_{17}N_3$ and synthesized $Fe_{65}Co_{35}$ powders were fabricated. Smaller grain size than the single domain size of the $Mn_{54}Al_{46}C_{2.44}$ without obvious grain boundaries and secondary phases is the origin for the low intrinsic coercivity. It was confirmed that the magnetic properties of the $Mn_{54}Al_{46}C_{2.44}$ can be enhanced by magnetic exchange coupling with the hard magnetic $Sm_2Fe_{17}N_3$ and soft magnetic $Fe_{65}Co_{35}$. The high degrees of the exchange coupling were verified by calculating first derivative curves. Thermo-magnetic stabilities of the composites from 100 to 400 K were measured and compared. It was demonstrated that the $Mn_{54}Al_{46}C_{2.44}$ based composites containing $Sm_2Fe_{17}N_3$ and $Fe_{65}Co_{35}$ could be promising candidates for future permanent magnetic materials with the proper control of purity, magnetic properties, etc.

• Journal of Magnetics
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• v.5 no.2
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• pp.50-54
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• 2000

NiMn-pinned spin valve films consisting of a layered glass/NiFe/Co/Cu/Co/NiFe/NiMn/Ta stack were made by do magnetron sputtering. After deposition, the structure was annealed in a series of cycles each including three hours at $220^\circ C, 2\times10^{-6}$ Torr, in a field of 350 Oe, to create an ordered antiferromagnetic structure in the NiMn layer and produce a strong unidirectional pinning field in the pinned magnetic layer, Optimum spin valve properties were obtained after seven annealing cycles, or 21 hours at $220^\circ C$, and were : MR ratio 1%, exchange coupling field 620 Oe, and coercivity of pinned layer 250 Oe. The exchange coupling field remained constant up to an operating temperature of $175^\circ C$, and the blocking temperature was about $380^\circ C$.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.207-207
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• 1996

Through molecular cloning, five muscarinic receptors have been identified. The muscarinic receptors can be generally grouped according to their coupling to either stimulation of phospholipase C (m1, m3, and m5) or the inhibition of adenylate cyclase (m2 and m4). Each m1, m3, and m5 receptors has the additional potential to couple to the activation of phospholipase A$_2$, C, and D, tyrosine kinase, and the mobilization of Ca$\^$2+/. However, the differences in coupling efficiencies to different second messenger systems between these receptors have not been studied well. Ectopic expression of each of these receptors in mammalian cells has provided the opportunity to evaluate the signal transduction of each in some detail. In this work we compared the coupling efficiencies of the m1, m3 and m5 muscarinic receptors expressed in chinese hamster ovary (CHO) cells to the Ca$\^$2+/ mobilization and the stimulation of neuronal nitric oxide synthase (nNOS). Because G protein/PLC/PI turnover/[(Ca$\^$2+/])i/NOS pathway was supposed as a main pathway for the production of nitric oxide via muscarinic receptors, we studied on ml, m3 and m5 receptors. Stimulation of guanylate cyclase activity in detector neuroblastoma cells was used as an index of generation nitric oxide (NO) in CHO cells. The agonist carbachol increased the cGMP formation and the intracellular [Ca$\^$2+/] in concentration dependent manner in three types of receptors and the increased cGMP formation was significantly attenuated by scavenger of NO or inhibitor of NOS. m5 receptors was most efficiently coupled to stimulation of nNOS, And, the coupling efficiencies to the stimulation of neuronal nitric oxide synthase in three types of receptors were parallel with them to the Ca$\^$2+/ mobilization.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.99-99
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• 2003