• Journal of the Korean Chemical Society
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• v.20 no.1
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• pp.15-18
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• 1976

The preferred conformation of benzenesulfenyl chloride was determined by EHMO calculation. It was found that the stability was dictated by the n-${\pi}$ conjugation of S atom with the benzene ring. The ethanolysis reaction of benzenesulfenyl chlorides has been studied. The rate constants obtained have been discussed in terms of substituent effects and d-orbital participation of sulfur atom. From a non-linear Hammett plot, bipyramid type of intermediate has been suggested.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.414-416
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• 1995

We have studied the effect of the mesogenic core of nematic liquid crystals (NLCs) for polar (out-of-plane tilt) anchoring strength on rubbed polyimide (PI) films. The order of polar anchoring strength for NLCs on rubbed PI films is 5CB > PCH5 > CCH5. This order is the same for all rubbing strengths investigated. From these results, we suggest that the polar anchoring strength strongly depends on the polarizability of the NLCs.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.213-214
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• 2000

New light-emitting polyimides were synthesized from the conventional polycondensation of 5,5'-bis(4-aminophenyl)-2,2'bifuryl (PFDA) with fluorinated and non-fluorinated aromatic dianhydrides, providing a good quality of thin films: 6F-PFDA PI and ODPA-PFDA PI. Their UV-visible absorbance and photoluminescent characteristics were investigated. The polymers emit blue and blue-greenish light in a quantum yield of 7.3-14.9%, depending on the polymer backbone.

• 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.

• Macromolecular Research
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• v.13 no.4
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• pp.334-338
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• 2005

A three-layered poly(benzyl ether) dendrimer having a bis-ethynylbenzene core was synthesized and characterized with $^{1}H$ NMR and MALDI-TOF-MS spectroscopy. The dendrimer was reacted with platinum complexes to obtain platinum-acetylide based organometallic polymers. When the dendrimer was reacted with trans-[$PtCl_{2}(PEt_{3})_{2}$], a high molecular weight polymeric compound was formed, whereas, with cis-[$PtCl_{2}dppp$], a uniform molecular weight compound was formed, which was found to be a dimeric metallacycle by $^{1}H\;NMR,\;^{31}P\;NMR$ and ESI-TOF-MS spectroscopy. Both these complexes exhibited relatively a strong emission around 440 nm, indicating that they could be potential candidates for blue emitting polymer LEDs.

• Journal of the Korean Chemical Society
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• v.68 no.3
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• pp.146-150
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• 2024

Precise molecular configuration elucidation of poly(3-hexylthiophene) (P3HT) through advanced spectroscopic techniques is pivotal for enhancing P3HT-based photovoltaic device efficiencies since its high charge-carrier mobility is directly correlated to its well-ordered structure. In this study, we examine Raman depolarization ratios of annealed and non-annealed P3HT films to elucidate their intermolecular π-π configurations. Our findings suggest that the backbone of the annealed film possesses stronger π-π conjugation overlaps than that of the non-annealed film owing to the greater depolarization ratio of the annealed film. In addition, the depolarization ratios are also supported by theoretical calculations, where parallel-stacked thiophene structures display a higher depolarization ratio compared with that of twisted-stacked structures, as calculated by the Møller-Plesset perturbation theory. This study highlights the utility of polarized Raman spectroscopy as a versatile tool for assessing the degree of molecular order in highly conjugated polymer films.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.164-165
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• 2000

There has recently been a considerable amount of interest in two-photon(TP) processes because of their applications to 3-D optical data storage and imaging, up-conversion lasing, and optical power limiting. Recently, the role of Dithienothlophene(DTT) as $\pi$-center of two-photon absorption(TPA) molecules was reported to give a large enhancement of TPA, compared with the benzeniods counterparts.$^{[1]}$ In this report, we carried out two experiments to investigate nonlinear optical absorption of the molecules in which central DTT is attached through conjugation to either a D/D or a D/A pair at the ends, forming a D-$\pi$-D(1 and 3) or D-$\pi$-A(2 and 4) sequence(Fig.1). All the samples were prepared in solutions with the same molar concentration. (omitted)

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3211-3217
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• 2013

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been employed to investigate the molecular structures and absorption spectra of three D-${\pi}$-A-type organic dyes (C1-1, D5 and TH208) containing identical ${\pi}$-spacers and electron acceptors, but different aromatic amine electron-donating groups (tetrahydroquinoline, triphenylamine and phenothiazine). The coplanar geometries indicate that the strong conjugation is formed in the dyes. The electronic structures suggest that the intramolecular charge transfer from the donor to the acceptor occurs, and the electron-donating ability of tetrahydroquinoline is stronger than those of triphenylamine and phenothiazine. The computed orbital energy levels of these dyes confirm that the electrons could be injected from the excited dyes to the semiconductor conduction band and the oxidized dyes could be reduced effectively by electrolyte. The TD-DFT results show that the CAM-B3LYP/6-31+G(d, p) is suitable for calculating the absorption spectra. The first absorption band for these dyes is assigned to the HOMO${\rightarrow}$LUMO and HOMO-1${\rightarrow}$LUMO transitions.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.330-336
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• 2002

A quantum-chemical investigation on the conformations and electronic properties of bis[2-{2-methoxy-4,6-di(t-butyl)phenyl}ethenyl]benzenes (MBPBs) as building block for ${\pi}$-conjugate polymer are performed in order to display the effects of t-butyl and methoxy group substitution and of kink(ortho and meta) linkage. The conjugation length of the polymers can be controlled by substituents and kink linkages of backbone. Structures for the molecules, o-, m-, and p-MBPBs as well as unsubstituted o-, m-, and p-DSBs were fully optimized by using semiempirical AM1, PM3 methods, and ab initio HF method with 3-21G(d) basis set. The potential energy curves with respect to the change of single torsion angle are obtained by using semiempirical methods and ab initio HF/3-21G(d) basis set. The curves are similar shape in the molecules with respect to the position of vinylene groups. It is shown that the conformations of the molecules are compromised between the steric repulsion interaction and the degree of the conjugation. Electronic properties of the molecules were obtained by applying the optimized structures and geometries to the ZINDO/S method. ZINDO/S analysis performed on the geometries obtained by AM1 method and HF/3-21G(d) level is reported. The absorption wavelength on the geometries obtained by AM1 method is much longer than that by HF/3-21G(d) level. The absorption wavelength of MBPBs are red shifted with comparison to that of corresponding DSBs in the same torsion angle because of electron donating substituents. The absorption wavelength of isomers with kink(orth and meta) linkage is shorter than that of para linkage.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2497-2502
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• 2010

Arg13 is a conserved active-site residue in all known Pi class glutathione S-transferases (GSTs) and in most Alpha class GSTs. To evaluate its contribution to substrate binding and catalysis of this residue, three mutants (R13A, R13K, and R13L) were expressed in Escherichia coli and purified by GSH affinity chromatography. The substitutions of Arg13 significantly affected GSH-conjugation activity, while scarcely affecting glutathione peroxidase or steroid isomerase activities. Mutation of Arg13 into Ala largely reduced the GSH-conjugation activity by approximately 85 - 95%, whereas substitutions by Lys and Leu barely affected activity. These results suggest that, in the GSH-conjugation activity of hGST P1-1, the contribution of Arg13 toward catalytic activity is highly dependent on substrate specificities and the size of the side chain at position 13. From the kinetic parameters, introduction of larger side chains at position 13 results in stronger affinity (Leu > Lys, Arg > Ala) towards GSH. The substitutions of Arg13 with alanine and leucine significantly affected $k_{cat}$, whereas substitution with Lys was similar to that of the wild type, indicating the significance of a positively charged residue at position 13. From the plots of log ($k_{cat}/{K_m}^{CDNB}$) against pH, the $pK_a$ values of the thiol group of GSH bound in R13A, R13K, and R13L were estimated to be 1.8, 1.4, and 1.8 pK units higher than the $pK_a$ value of the wild-type enzyme, demonstrating the contribution of the Arg13 guanidinium group to the electrostatic field in the active site. From these results, we suggest that contribution of Arg13 in substrate binding is highly dependent on the nature of the electrophilic substrates, while in the catalytic mechanism, it stabilizes the GSH thiolate through hydrogen bonding.