• Bulletin of the Korean Chemical Society
• /
• v.23 no.2
• /
• pp.291-294
• /
• 2002

The reactions of triplet oxygen atom with halomethanes as a potential fire extinguisher were studied by a discharge flow-chemiluminescence imaging method. The experiments were carried out under second order conditions. The bimolecular atom-molecule reaction rate constants were determined in terms of the initial rate method. The initial concentration of oxygen atom was also determined under second order rate law instead of the pseudo-first order conditions with $[O(^3P)]_0{\ll}[sample]_0$. The second order conditions were more reliable than pseudo-first order conditions for the determinations of rate constants. The rate constants of the reactions $CF_3I\;+\;O(^3P)$, $CH_3PI\;+\'O(^3P)$, and $CHBrCl_2\;+\;O(^3P)$ were determined to be $5.0\;{\times}\;10^{-12}$ , $1.1\;×\;0^{-11}$ , and $1.9\;{\times}\;10^{-14}cm^3molecule^{-1}s^{-1}$, respectively.

• Journal of Integrative Natural Science
• /
• v.11 no.2
• /
• pp.107-112
• /
• 2018

p38 MAP kinase belongs to the Mitogen-activated protein (MAP) kinase family; a serine/threonine kinase. It plays an important role in intracellular signal transduction pathways. It is associated with the development and progression of various cancer types making it a crucial drug target. Present study involves the HQSAR analysis of recently reported imidazo[1,2-b]pyridazine derivatives as p38 MAP kinase antagonists. The model was generated with Atom (A), bond (B), chirality (Ch), and hydrogen (H) parameters and with different set of atom counts to improve the model. An acceptable HQSAR model ($q^2=0.522$, SDEP=0.479, NOC=5, $r^2=0.703$, SEE=0.378, BHL=97) was developed which exhibits good predictive ability. A contribution map for the most active compound (compound 17) illustrated that hydrogen and nitrogen atoms in the ring A and ring B, as well as nitrogen atom in ring C and the hydrogen atom in the ring D provided positive activity in inhibitory effect while, the least active compound (compound 05) possessed negative contribution to inhibitory effect. Hence, analysis of produced HQSAR model can provide insights in the designing potent and selective p38 MAP kinase antagonists.

• Macromolecular Research
• /
• v.15 no.4
• /
• pp.385-391
• /
• 2007

Block copolymer micelles are generally formed via the self-assembly of amphiphilic block copolymers in an aqueous medium. The hydrophilic and hydrophobic blocks form shell and core micelles, respectively. The block copolymers of methoxy poly(ethylene glycol) (MPEG)-b-poly(2-diisopropylamino)ethyl methacrylate (PDPA) were synthesized via atom transfer radical polymerization, with the macro initiator synthesized by the coupling of 2-bromoisobutyryl bromide with MPEG in the presence of a triethyl amine base catalyst. The atom transfer radical polymerization of 2-diisopropylamino)ethyl methacrylate was performed in conjunction with an N,N,N',N",N"-pentamethyl-diethylenetriamine/copper bromide catalyst system, in DMF, at $70^{\circ}C$. The pH induced micellization/demicellization was studied using fluorescence, with a pyrene probe. Furthermore, the pH dependent micellization was confirmed using the microviscosity method, with a dipyme fluorescence probe. The pH dependant micelle size distribution was studied using dynamic light scattering. The characterization of the synthesized polymers was established using gel permeation chromatography and from the $^1H-nuclear$ magnetic resonance spectroscopy.

• Macromolecular Research
• /
• v.15 no.4
• /
• pp.302-307
• /
• 2007

The living radical polymerization of methyl methacrylate (MMA) by atom transfer radical polymerization, (ATRP) employing a $Fe(II)X_2/diphenyl-2-pyridyl$ phosphine (PyP) catalytic system (X=Cl, Br), was investigated using several initiators and solvents at various temperatures. Most of the polymerizations with the PyP ligand were well controlled, with a linear increase in the number average molecular weights ($M_n$) vs. conversion, with relatively low molecular weight distributions ($M_w/M_n=1.2-1.4$) throughout the reactions. The measured weights matched those of the predicted values. The ethyl-2-bromoisobutyrate (EBriB) initiated ATRP of MMA, with the $Fe(II)X_2/diphenyl-2-pyridyl$ phosphine catalytic system (X=Cl, Br), was better controlled in p-xylene at $80^{\circ}C$ than the other solvents used in this study.

• Bulletin of the Korean Chemical Society
• /
• v.1 no.1
• /
• pp.1-4
• /
• 1980

During the study of the kinetics of Cl atom reactions by atomic fluorescence method we observed anomalous fluorescence emission for some atomic transitions. Instead of usual decrease of the fluorescence intensity by adding substrate, 1363 A transition $(^2P^{\circ}_{3/2}{\to}^2P_{1/2})$ intensity increased by adding substrate. From the normally behaved fluorescence lines the absolute rate constant for the reaction, Cl + $CH_3Cl{\to}$, was found to be $4.2{\times}10^{-13}$ cc/molecule sec at $20^{\circ}C$.

• Journal of the Korean Chemical Society
• /
• v.41 no.6
• /
• pp.277-283
• /
• 1997

Platinum(II) complexes(where, $[Pt(L)_2X_2]$; L=isoxazole(isox), 3,5-dimethylisoxazole(3,5-diMeisox), 3-methyl,5-phenylisoxazole(3-Me,5-Phisox), and 4-amino-3,5-dimethylisoxazole(4-ADI); X=Cl, Br) with planar ligands are investigated on antitumor activity by MM2 and EHMO calculations. It was found that, the net atomic charges of the halogen atoms in all of cis-, trans-isomers are greater than that of the nitrogen with planar form, indicating that ionic character of Pt-X bond is greater than that of Pt-N. Also, the ${\sigma}MO$ energy level($E{\sigma}_{(Pt-X)}$) of the interaction between $d_{x2-y2}$ orbital of Pt atom and $p_x$ orbital of X found to be higher than that of between $d_{x2-y2}$ orbital of Pt atom and $p_x$ orbital of N about all the complexes. It is found that bond strength of between Pt and X atom is weaker than that of between Pt and N atom. The ${\sigma}MO$ energy level($E{\sigma}_{(Pt-X)}$) of trans- complexes found to be higher than that of cis- complexes, as a result of bond strength of Pt-X in cis- and trans-complexes, for all the complexes. The degree of dissociation of X atom in Pt-X bond for trans-complexes are related to antitumor activity and the logIA value of inhibitory activity coefficient(IA).

• Bulletin of the Korean Chemical Society
• /
• v.15 no.9
• /
• pp.752-758
• /
• 1994

Several one-electron reduction products of ${\gamma}$(1,2)-[$H_nSiV_2W_{10}O_{40}]^{(6-n)-}$ were separated by precipitating or coprecipitating with diamagnetic host compounds at different pH. Mono-and diprotonated species, 1 and 2, in powder samples exhibit aPR spectra characteristic of a mononuclear oxovanadium species, indicating that the unpaired electron is trapped at one vanadium atom. The EPR spectrum of the unprotonated species 0 shows 15 parallel lines, indicating that the unpaired electron interacts equally with two vanadium atoms. While different species were precipitated depending upon the pH of the solution and the charge of the host anion, only one species 1' was formed in the frozen solutions at pH 3.2-4.7. The EPR spectrum of 1' indicates that the unpaired electron is trapped at one vanadium atom and 1/16 of the spin density is delocalized onto the second vanadium atom. The species 1' is probably another form of the monoprotonated species. The EPR spectra show that some of 2 transform into 1 and some of 0 transform into 1' in the solid state at low temperatures. It is suggested that proton transfer between the heteropolyanion and water molecues in the solid state is involved in these transformations.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.579-579
• /
• 2013

We study on Argon metastable and 4p state neutral atom density in magnetized ICP Helicon plasmas by Laser Induced Fluorescence and plasma emission. The results show that metastable density is too low at the center of chamber due to significant neutral depletion. Otherwise, 4p state is high at the center of chamber because electron density is very high. Power and pressure dependence of metastable and 4p state neutral atom have been spatially measured in the radial direction of cylindrical chamber.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.6
• /
• pp.515-518
• /
• 1995

YSe1.83 was synthesized by vapor transport technique and its crystal structure was determined. The structure was isostructure of LaTe2-x, which was layered structure consisting of two-atom thick layers of YSe with distorted NaCl-type structure and one-atom thick layer of Se. The substructure of YSe1.83 was tetragonal with space group of P4/nmm and a=4.011(2) and c=8.261(3) Å with final R/Rw=6.4/6.9 %. The superstructure with asuper=2a, bsuper=6b and csuper=2c was found. The measurements of electronic and magnetic properties of this compound indicate that it is an electronic insulator and diamagnet.

• Proceeding of EDISON Challenge
• /
• 2013.04a
• /
• pp.256-259
• /
• 2013

We investigate co-doping effects of conjugated P-N B-N with increasing of N concentration in the graphene sheets using a first principles based on the density functional theory. N doping sites of the graphene consider two possible sites (pyridinic and porphyrin-like). Energy calculation shows that additional doping of B atom in the porphyrin-like N doped graphene ($V+B-N_x$) is hard to form. At the low chemical potential of N, one N atom with additional doping in the graphene ($V+P-N_1$, $P/B-N_1$) has low formation energy on the other hand at high chemical potential of N, high concentration of N ($V+P-N_4$, $P/B-N_3$) in the graphene is governing conformation. From the results of electronic band structure calculation, it is found that $V+P-N_4$ and $P/B-N_3$ cases change the Fermi energy therefore type change is occurred. On the other hand, the cases of $V+P-N_1$ and N+B recover the electronic structure of pristine graphene.