• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1649-1654
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• 2003

We have investigated substituent effect on the stabilization energies, and nucleus-independent chemical shifts of pentafulvalenes and on the electronic structures of the corresponding polypentafulvalenes to design environmentally stable semiconductive or conductive polymers. Geometrical optimizations of the molecules were carried out at the density functional level of theory with B3LYP hybrid functional and 6-311+G(d) basis set. Stabilization energies were estimated using isodesmic and homodesmotic reactions. As a criterion of aromaticity nucleus-independent chemical shifts of the molecules were computed using GIAO approach. For the polymers the geometrical parameters were optimized through AM1 band calculations and the electronic structures were obtained through modified extended Huckel band calculations. It is found that strong electronwithdrawing substituents increase isodesmic and homodesmotic stabilization energies of pentafulvalene, though it does not increase the aromaticity. Nitro-substituted pentafulvalene is estimated to have stabilization energy as much as azulene. However, substitution either with electron-donating groups or with electronwithdrawing groups does not significantly affect the electronic structures of polypentafulvalene and poly (vinylenedioxypentafulvalene).

• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.87-92
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• 2000

The electronic and chemical properties of the surface Pt and Ru atoms in the Pt-Ru alloy have been investigated by means of extended Huckel calculations. An electron transfer occurs from Ru to Pt, resulting in an increased electron density on the surface Pt atoms. The transfer is found to be larger toward Pt atoms out of contact with Ru. The calculated electronic perturbation of the water molecule is similar when it is adsorbed either on the Pt site or on the Ru site in the alloy. However, the water adsorption strength is much smaller in the former case, since the lone-pair donations are reduced relative to the latter case. This is essentially due to a larger closed-shell repulsive interaction between $1b_2(H_2O)$ and $d_{yz}$ (Pt).

• Bulletin of the Korean Chemical Society
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• v.22 no.8
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• pp.807-815
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• 2001

Two-dimensional (2D) correlation method, which generates the synchronous and the asynchronous 2D spectrum by complex cross correlation of the Fourier transformed spectra, is an analysis method for the changes of the sample spectrum induced by vari ous perturbations. In the present work, the 2D electronic correlation spectra have been simulated for the cases where the sample spectrum composed of two gaussian bands changes linearly. When only the band amplitudes of the sample spectrum change, the synchronous spectrum shows strong peaks at the band centers of the sample spectrum, but the asynchronous spectrum does not make peaks. When the sample spectrum shifts without changing intensity and width, the synchronous spectrum shows peaks around the initial and final positions of the band maximum and the asynchronous spectrum shows long peaks spanning the shifting range. The band width change produces the complex 2D correlation spectra. When the sample spectrum shifts with band broadening, the width change by 50% of full width at half maximum (FWHM) does not give so large an effect on the correlation spectrum as the spectral shift by one half of FWHM of the sample spectrum.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.845-850
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• 1995

A systematic method is presented to analyze the bandgaps of conjugated polymers in terms of geometrical relaxations and electronic effect of moieties using the equation of Eg=ΔEδr + ΔE1-4 + ΔEel. The relationship between ΔEδr and δr is derived from trans-PA and is transferred to other conjugated polymeric systems. By applying this method to heterocyclic polymers, very useful information is obtained to understand the evolution of bandgaps of PT, PPy and PF in connection with the chemical structures and electronic effect of the heteroatoms. We believe that this method is very helpful to understand the evolution of bandgaps of various conjugated polymers in connection with the chemical structures and electronic effect of moieties. Also, the method is expected to provide valuable information to design a small bandgap polymers.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1063-1068
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• 1998

The nature of F electronic excitation energy transfer to OH- vibrational levels in KCl crystals is the exchange interaction, although the transfer process exhibits three temporally distinguishable components depending on the distance between excited F center and OH-. The critical distance as well as rate of the major energy transfer process in randomly distributed samples increases rapidly as OH- librational motions become active with temperature rise. The excited state character introduced into the OH- ground electronic state by perturbation is essential for the exchange interaction. The perturbation is brought about by the expanded electron cloud of excited F center for OH- associated to F center, whereas by librations and lattice vibrations perpendicular to the bond axis for isolated OH- . F excitation quenching efficiency by OH- is dependent on the variation of the critical distance rather than the rate as the rate is much faster than the normal F bleach recovery rate.

• Bulletin of the Korean Space Science Society
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• 2006.04a
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• pp.133-136
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• 2006

Unlike large satellites, small satellites, such as nanosatellite and microsatellite, provide a limited interior space for components mounting. In order to mitigate this issue, the compact Bus Electronic Unit (BEU) that integrates satellite electronic modules, combining most of bus subsystems and payloads electronic modules into one unit, has been developed for HAUSAT-2 nanosatellite. This paper addresses the design and environmental test result analyses of BEU.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4332-4336
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• 2011

The chalcopyrite-type $CuInSe_2$ is a remarkable material for thin film solar cells owing to its electronic structure and optical response. Single-phase sphere-like $CuInSe_2$ nanocrystallite particles were prepared by a facile noninjection method with triethanolamine as the complexing agent and the solvent simultaneously. The period of the reaction was the key to form single-phase $CuInSe_2$ nanocrystals at $240^{\circ}C$. TEM, XRD, XPS, EDX investigations were performed to characterize the morphology and the detailed structure of as-synthesized $CuInSe_2$ nanocrystals. All of the analysis results proved that the synthesized nanocrystals were pure phase and close to the stoichiometric ratio rather than a simple mixture. The band gap of the obtained $CuInSe_2$ nanocrystals was $1.03{\pm}0.03$ eV.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.647-652
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• 2009

A novel spiro-type host material, 5-[4-(1-naphthyl)phenyl]-spiro[fluorene-7,9'-benzofluorene] (BH-1PN) and three new dopants, namely, 5-[diphenylamino)phenyl]-spiro[fluorene-7,9'-benzofluorene] (BH-1TPA), 5-[4-(N-phenyl (m-tolyl)amino]-spiro[fluorene-7,9'-benzofluorene] (BH-1MDPA) and 5-[(N-phenyl)-2-naphthyl]amino-spiro[fluorene- 7,9'-benzofluorene] (BH-1NPA) were designed and successfully prepared using the Suzuki or amination reactions. The electroluminescence characteristics of BH-1PN as a blue host material doped with each of the blue dopants were evaluated. The structure of the device is ITO/DNTPD/NPB/BH-1PN:5% dopant/Alq3/Al-LiF. The device obtained from BH-1PN doped with diphenyl-[4-(2-[1,1;4,1]terphenyl-4-yl-vinyl)phenyl]-amine (BD-1) showed good color purity, efficiency, luminance, and current-density characteristics.

• Journal of the Korea Society of Computer and Information
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• v.3 no.4
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• pp.145-153
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• 1998

Electronic paper resources management becomes an important alternative to overcome the inefficiency of various dysfunctions and pathologies dependent upon bureaucratic paperworks and to enhance organizational competitiveness. Korean government and enterprises have less recognized the importance of electronic document management and ignored the merits of introducing information technology into organizations. By means of document and paper exchange, decision making and signature, mail and bulletin board systems, information disclosure and sharing using electronic technology, however, electronic document management system can enhance organizational performance on a considerable degree. In this sense, it is necessary to introduce the system as soon as possible. Several measures are required : revising related laws and regulations, reforming the sense and behavior of personnel, establishing technological basis of the system, standardizing word processors and document formats.

• Bulletin of the Korean Chemical Society
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• v.24 no.4
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• pp.494-498
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• 2003

The transition from aromatics to heteroaromatics is very attractive since it provides an extremely large structural variety, the chemical functionality as well as the possibilities for electronic tuning of the fullerene properties. A synthesis of heterofullerenes in macroscopic quantities is unknown however the spectrometric detection of $C_{59}B$ has been reported. The electronic structures of $C_{(60-2x)}(BN)_x$ systems, isoelectronic with $C_{60}$ have been explored by Extended Hukel, AM1 and ab initio methods. The polyhedral assembly energy are 7.7 kcal greater than $C_{60}$ when one B-N unit is substituted with C-C unit. The assembly energies are getting bigger if more B-N unit is introduced. We focus on HOMO-LUMO energy gap and the stability effects in $C_{(60-2x)}(BN)_x$ with different compositions of $(BN)_x$ moiety. The bonding properties of the substituent atoms were investigated in detail.