• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.924-926
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• 2004

• Journal of the Korean Chemical Society
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• v.8 no.2
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• pp.43-46
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• 1964

Quenching constants, q, determined for N,N-dimethylanilines by liquid scintillation counting indicate that the quenching involves an energy transfer process to these compounds causing strong n-${\pi}$ interaction within the quencher molecule, which is then followed by an non-radiative degradation of the excitation energy to ground state.

• Bulletin of the Korean Chemical Society
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• v.26 no.12
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• pp.1946-1952
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• 2005

New group 15 organometallic compounds, M$(phenanthrenyl)_3$ (M = P (1), Sb (2), Bi (3)) have been prepared from the reactions of 9-phenanthrenyllithium with $MCl_3$. A reaction of 9-(diphenylphosphino)phenanthrene with 2,6-diisopropylphenyl azide led to the formation of (phenanthrenyl)${(Ph)}_2P$=N-(2,6-$^iPr_2C_6H_3$) (4). The crystal structures of 2 and 4 have been determined by single-crystal X-ray diffractions, both of which crystallize with two independent molecules in the asymmetric unit. Compound 2 shows a trigonal pyramidal geometry around the Sb atom with three phenanthrenyl groups being located in a screw-like fashion with an approximately $C_3$ symmetry. A significant amount of CH- -$\pi$ interaction exists between two independent molecules of 4. The phosphorus center possesses a distorted tetrahedral environment with P-N bond lengths of 1.557(3)$\AA$ (P(1) N) and 1.532(3)$\AA$ (P(2)-N), respectively, which are short enough to support a double bond character. One of the most intriguing structural features of 4 is an unusually diminished bond angle of C-N-P, attributable to the hydrogen bonding of N(1)-H(5A) [ca. 2.49$\AA$ between two adjacent molecules in crystal packing. The compounds 1-3 show purple emission both in solution and as films at room temperature with emission maxima ($\lambda_{max}$) at 349, 366, and 386 nm, respectively, attributable to the ligand centered $\pi$ $\rightarrow$ $\pi^\ast$ transition in phenanthrene contributed by the lone pair electrons of the Gp 15 elements. Yet the nature of luminescence observed with 4 differs in that it originates from $\pi$ (diisopropylbenzene)-$\pi^\ast$ (phenanthrene) transitions with the $\rho\pi$contribution from the nitrogen atom. The emission maximum of 4 is red-shifted ranging 350-450 nm due to the internal charge transfer from the phenanthrenyl ring to the N-arylamine group as deduced from the ab initio calculations.

• Research in Plant Disease
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• v.10 no.4
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• pp.217-226
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• 2004

One hundred isolates of Magnaporthe grisea from Korea and China were characterized for pathogenicity using eight Korean differential varieties(KDV), six Chinese differential varieties(CDV) and six near isogenic lines(NILs) developed in China. The restriction length polymorphism of M. grisea isolates from each country also was analyzed using MGR586 as a probe. One hundred Korean isolates classified into 17 races on KDV were grouped into 29 pathotypes on Chinese near isogenic lines(NILs). Virulence of 46% of Korean isolates against all the six Chinese NILs indicated that the current six Chinese NILs alone was not enough to be used as differential varieties in Korea. Especially, susceptibility of the BL1 carrying resistance gene Pi-b to 70% of tested Korean isolates suggested that BL1(Pi-b) may not be a useful resistance source to Korean blast. Based on the virulence assays of M. grisea populations from each country were divided into two groups. About 50% of Chinese isolates showed similarity to the 30% of the Korean isolates. Especially, the isolates from northern part of China, where Japonica rice cultivars were grown, showed high similarity to the Korean isolates, while isolates from southern part of China, where Indica rice were mainly grown, showed low similarity to Korean isolates. The genome RFLPs of Korean isolates were quite different from those of southern part of China using MGR586 as a probe. These data indicated that the physiological and genetical characteristics of M. grisea population might be determined by strong interaction with cultivated rice.

• Analytical Science and Technology
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• v.7 no.2
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• pp.225-232
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• 1994

The podands I-VII, acyclic polyethers, expected high extractability for $Ag^+$ against $Pb^{2+}$ were designed and synthesized with high yields. Using podands I-VII as extractants, the %extraction(%Ex) of $Ag^+$ and $Pb^{2+}$ as picrates were determined in water/chloroform systems. The stability constants(log K) for the complexation of $Ag^+$ with podands I-VII were also determined by potentiometry. %Ex($Ag^+$) were proportional to the numbers of substituted sulfur donor atoms. Podand VI(log K : 7.65) having 3 substituted sulfur and podand VII(log K : 9.15) having 4 substituted sulfur, however, exhibited almost 100% of extractability, respectively. In %Ex($Ag^+/Pb^{2+}$, oxygen-sulfur mixed donor podands(IV-VII) showed the higher values. Otherwise, the values of log K and %Ex($Ag^+$) largely depended on the variation of donor-site of sulfur. From the results of NMR experiments, it seems that it is due to the ${\pi}-{\pi}$ stacking interaction between the aromatic end-groups.

• BMB Reports
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• v.37 no.6
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• pp.720-725
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• 2004

A number of signaling molecules contain small pleckstrin homology (PH) domains capable of binding phosphoinositides or proteins. Phospholipase C (PLC)-${\gamma}1$ has two putative PH domains, an $NH_2$-terminal (PH1) and a split PH domain ($nPH_2$ and $cPH_2$). We previously reported that the split PH domain of PLC-${\gamma}1$ binds to phosphatidylinositol 4-phosphate (PI(4)P) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)$P_2$) (Chang et al., 2002). To identify the amino acid residues responsible for binding with PI(4)P and PI(4,5)$P_2$, we used site-directed mutagenesis to replace each amino acid in the variable loop-1 (VL-1) region of the PLC-${\gamma}1$ $nPH_2$ domain with alanine (a neutral amino acid). The phosphoinositide-binding affinity of these mutant molecules was analyzed by Dot-blot assay followed by ECL detection. We found that two PLC-${\gamma}1$ nPH2 domain mutants, P500A and H503A, showed reduced affinities for phosphoinositide binding. Furthermore, these mutant PLC-${\gamma}1$ molecules showed reduced PI(4,5)$P_2$ hydrolysis. Using green fluorescent protein (GFP) fusion protein system, we showed that both $PH_1$ and $nPH_2$ domains are responsible for membrane-targeted translocation of PLC-${\gamma}1$ upon serum stimulation. Together, our data reveal that the amino acid residues $Pro^{500}$ and $His^{503}$ are critical for binding of PLC-${\gamma}1$ to one of its substrates, PI(4,5)$P_2$ in the membrane.

• Applied Science and Convergence Technology
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• v.24 no.5
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• pp.151-155
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• 2015

The interfacial electronic structure between zinc phthalocyanine (ZnPc) and aluminumdoped zinc oxide (AZO) substrates has been evaluated by ultraviolet photoemission spectroscopy and angle-dependent x-ray absorption spectroscopy to understanding the molecular orientation of a ZnPc layer on the performance of small molecule organic photovoltaics (OPVs). We find that the ZnPc tilt angle improves the ${\pi}-{\pi}$ interaction on the AZO substrate, thus leading to an improved short-circuit current in OPVs based on phthalocyanine. Furthermore, the molecular orientation-dependent energy level alignment has been analyzed in detail using ultraviolet photoemission spectroscopy. We also obtained complete energy level diagrams of ZnPc/AZO and ZnPc/indium thin oxide.

• Journal of Photoscience
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• v.12 no.2
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• pp.57-61
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• 2005

The ground and excited state dipole moments of Coumarin 450 (C 450) laser dye were measured at room temperature in several solvents of varying dipole moments. The ground state dipole moment (${\mu}_g$) is estimated by using the modified Onsagar model and the excited state dipole moments (${\mu}_e$) were estimated by the method of solvatochromism as well as by utilizing the microscopic solvent polarity parameter ($E^N_T$). Further, the deviation of some of the points from the linearity of the $E^N_T$ versus Stokes shift indicates the existence of specific type of solute-solvent interaction. The excited state dipole moment of C 450 were found to be higher than those of the ground state and is interpreted in terms of the resonance structure of the molecule. A reasonable agreement has been observed between the values obtained by the method of solvatochromism and modified Onsagar model. It is observed that, corresponding to cyclohexane solution, the fluorescence maxima shift towards the red region with increasing the polarity of the solvents, hence the transition involved are of ${\pi}-{\pi}^*$ type.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.11
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• pp.538-543
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• 2006

A high-Power continuous-wave (CW) ten-vane double-strapped magnetron oscillator has been investigated using three-dimensional (3D) particle-in-cell (PIC) numerical simulation code, MAGIC3D. The resonant modes and their resonant frequencies of the ten-vane strapped magnetron resonator were obtained to show a large mode separation near the ${\pi}$-mode. An electron cloud formed in an anode-cathode gap, called an interaction space was confined well enough to result in no leakage current. Five spokes were clearly observed in the electron cloud, which definitely ensured the ${\pi}$-mode oscillation in the ten-vane magnetron. Numerical simulations predicted that the saturated microwave output power measured at the coaxial output port was 5.41 kW at the microwave frequency of 893 MHz, corresponding to a power conversion efficiency of 72.6% when the external axial magnetic field was 1150 gauss and the electron beam voltage and current were 6 kV and 1.25 A, respectively.

• Journal of Integrative Natural Science
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• v.2 no.2
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• pp.65-68
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• 2009

Siloles of considerable current interest, both because of their unusual electronic properties and because of their possible application as electron-transporting materials in devices such as light-emitting diodes (LED's) and chemical sensor. Siloles have been characterized by NMR, FT-IR, and UV-vis absorption spectroscopy. Their optical characteristics have been also investigated using photoluminescence spectroscopy. Thus siloles exhibit a low reduction potential and a low-lying LUMO energy level, attributed to ${\sigma}^*-{\pi}^*$ conjugation arising from the interaction between the ${\sigma}^*$ orbital of the sigma-bonded silicon atom and the $\pi^*$ orbital of the butadiene moiety of the ring.