• Journal of the Korean Applied Science and Technology
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• v.27 no.1
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• pp.1-5
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• 2010

HOMO(the highest occupied molecular orbital) and LUMO(the lowest unoccupied molecular orbital) of four recalcitrant polycyclic aromatic hydrocarbons (PAHs) were calculated by MOPAC program(CaChe Co). The previous papers which reported experimental results about radical reaction of PAHs were reviewed. The reported radical reaction positions of four PAHs corresponded with predicted positions in which ${\Delta}E$(HOMO-LUMO) was high. From these results, it appears that determining the ${\Delta}E$(HOMO-LUMO) of a PAH is a promising method for predicting the radical reaction position.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.142.2-142.2
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• 2016

The metal intercalation to an organic semiconductor is of importance since the charge transfer between a metal and an organic semiconductor can induce the highly enhanced conductivity for achieving efficient organic electronic devices. In this regard, the changes of the electronic structure of copper phthalocyanine (CuPc) caused by the intercalation of potassium are studied by ultraviolet photoemission spectroscopy (UPS) and density functional theory (DFT) calculations. Potassium intercalation leads to the appearance of an intercalation-induced peak between the highest molecular occupied orbital (HOMO) and the lowest molecular unoccupied orbital (LUMO) in the valence-band spectra obtained using UPS. The DFT calculations show that the new gap state is attributed to filling the LUMO+1, unlike a common belief of filling the LUMO. However, the LUMO+1 is not conductive because the ${\pi}$-conjugated macrocyclic isoindole rings on the molecule do not make a contribution to the LUMO+1. This is the origin of a metal-insulator transition through heavily potassium doped CuPc.

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1015-1019
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• 1995

The electronic structures and properties of the neutral and multiply charged C60n ions (n=2+ to 6-) with spin states have been investigated by semi-empirical MNDO calculations. In the ground state, C601- has the lowest total energy and the highest binding energy. The neutral C60 ion is supposed to have a high ionization potential and a high electron affinity. The HOMO and LUMO positions are lower in the cationic C60 than in the anionic C60. The LUMO energy becomes increasingly positive from C601- to C606- and the HOMO energy becomes increasingly negative from C602+ to C60. The HOMO-LUMO gap of the neutral C60 ion is higher than that of the multiply charged C60 ions. From the HOMO-LUMO gap, it seems reasonable to expect that electrons of the multiply charged C60 ions will be more polarizable than those of the neutral C60 ion. The HOMO and LUMO energies increase as the negative charge increases.

• Journal of the Korean Chemical Society
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• v.40 no.8
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• pp.579-584
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• 1996

The HOMO-LUMO gap, and static and dynamic third-order polarizabilities for the polyenes are evaluated by means of the time-dependent Hartree Fock(TDHF) semiempirical PM3, AM1, MNDO, and MINDO/3 calculations. All calculations have performed on the series $C_2H_4$ to $C_{32}H_{34}$. The HOMO-LUMO gap increases in the order: MINDO/3> MNDO> PM3> AM1 levels. THG, DC-EFISHG, IDRI, and OKE for the various calculations show the order: AM1 > MNDO > PM3 levels. The various third-order effects for the polyenes have the following order: THG> DC-EFISHG> IDRI> OKE.

• Journal of the Korean institute of surface engineering
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• v.45 no.1
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• pp.15-19
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• 2012

Tris(8-quinolinolato)aluminum(III); $Alq_3$ has been frequently used as an electron transporting layer in organic light-emitting diodes. Either Ba with a low work function or Au with a high work function was deposited on $Alq_3$ layer in vacuum. And then, the behaviors of electron transition at the $Alq_3$/Ba and $Alq_3$/Au interfaces were investigated by using the near edge x-ray absorption fine structure (NEXAFS) spectroscopy. In the each interface, the energy levels of unoccupied obitals were assigned as ${\pi}^*$(LUMO, LUMO+1, LUMO+2 and LUMO+3) and ${\sigma}^*$. And the relative intensities of these peaks were investigated. In an oxygen atom composing $Alq_3$ molecule, the relative intensities for a transition from K-edge to LUMO+2 were largely increased as Ba coverage (${\Theta}_{Ba}$, 2.7 eV) with a low work function was in-situ sequentially increased on $Alq_3$ layer. In contrast, the relative intensities for the LUMO+2 peak were reduced as Au coverage (${\Theta}_{Au}$, 5.1 eV) with a high work function were increased on $Alq_3$ layer. This means that the electron transition by photon in oxygen atom which consists in the unoccupied orbitals in $Alq_3$ molecule, largely depends on work function of a metal. Meanwhile, in the case of electron transition in a carbon atom, as ${\Theta}_{Ba}$ was increased on $Alq_3$, the relative intensity from K-edge to ${\pi}_1{^*}$ (LUMO and LUMO+1) was slightly decreased, and from K-edge to ${\pi}_2{^*}$ (LUMO+2 and LUMO+3) was somewhat increased. This rising of the energy state from ${\pi}_1{^*}$ to ${\pi}_2{^*}$ exhibits that electrons provided by Ba would contribute to the process of electron transition in the $Alq_3$/Ba interfaces. As shown in above observation, the analyses of NEXAFS spectra in each interface could be important as a basic data to understand the process of electron transition by photon in pure organic materials.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.357-360
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• 1994

The CNDO/2 calculations have been applied on cluster models for the representative active sites in V-silicalite to get Wiberg bond orders, LUMO energies and total energies. The B acidities of suggested models were investigated in terms of O-H bond orders. And the calculated LUMO energies showed the L acidities of the active sites. The structural stabilities of cluster models were also explained in terms of total energies.

• Analytical Science and Technology
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• v.20 no.1
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• pp.61-69
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• 2007

The geometrical parameters, total and relative energies, vibrational frequencies, the HOMO-LUMO energy gap, and reorganization energies for the neutral molecule, anion, and cation of $C_{16}H_{16}O_3$ have been determined using density functional method (DFT). The highest level of theory employed in this study is $B3LYP/6-311G^{**}$. Harmonic vibrational frequencies were determined at the $B3LYP/6-311G^{**}$ level of theory. All positive vibrational frequencies were obtained to confirm minimum structures. The HOMO-LUMO energy gap and reorganization energies were calculated to predict the charge transport property of liquid-crystal.

• Journal of the Korean Chemical Society
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• v.40 no.4
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• pp.229-234
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• 1996

Carcinogenicities of Benzo[a]pyrene(BP) and its metabolites were investigated by PM3. The 4, 5, 5a, and 6 positions forming transbutadiene(TB) frame in BP have been proved to be carcinogenic region by LUMO. We have found that the carcinogenic region of BP-triol, ultimate cacinogen, is shifted from 4, 5, 5a, and 6 positions of precarcinogen to 10, 10a, 12c, and 12b ones. The appreximate charge transfer quantities turned out to have the largest value between HOMO of Guanine and LUMO of BP-triol corresponding to TB region on each other.

• Journal of the Korean Chemical Society
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• v.31 no.2
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• pp.133-142
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• 1987

Stereoselectivities of (4+2) cycloaddition reactions of cyclopentadiene with the methyl-substituted allenic acids and esters were investigated by application of $\pi$-nonbonded interaction ($\pi$-NBI) theory. 2-FMO method has been found to be adequate for determination of endo selectivities of diene(LUMO)-dienophile (LUMO) interaction in the thermal reactions and diene (HOMO)-dienophile (LUMO) interaction in the Lewis acid catalyzed reactions. $\pi$-isoconjugate diene structure was formed by through-bond interaction of allene moiety with methyl group in the cumulated diene system; the methyl substituent acts as a conjugative chain and causes inter-level narrowing effect of the FMO's. In dienophiles which do not form $\pi$-isoconjugate diene system, methyl group acts merely as an electron donating group. In thermal reactions, the stereoselectivities are controlled by $\pi$-nonbonded secondary orbital interaction ($\pi$-NSOI) of methyl substituent, which behaves similarly as an ethylene molecule.

• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.284-292
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• 1984

This paper aims to predict the substituent and Lewis acid catalysis effect or reactivity on the regioselectivity of (4+2) cycloaddition reaction of the substituted-E-arene-diazocyanides and nitrosobenzenes. Frontier orbital theory (FMO) has been applied to thermal and catalyzed Diels-Alder reaction by means of CNDO/2 and EHT-SPD methods. It has been found that: (1) The above reaction is positive rho(${\rho}$) values in Hammett equation, so it takes normal electron demand reaction, and four-frontier orbitals and Anh methods are identical with experimental major regioisomer.(2) When electron withdrawing radicals are substituted HOMO and LUMO energies of dienophiles are reduced, and the reactivity is increased. (3) The major regioisomer is predicted as B type, as the Lewis acid makes complexes of dienophile, and polaries LUMO coefficients of dienophile in an opposite way. (4) The linear correlation of Hammett is indicated in the graph of stabilized energies(${\Delta}$E) and sigma(${\sigma}$).