• Bulletin of the Korean Chemical Society
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• 제11권1호
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• pp.49-54
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• 1990

The gas-phase thermolysis reactions of ${\alpha}$- and ${\beta}$-methylated ethyl formates, Y = $CH-X-CHR_1CH_2R_2$ where X = Y = O or S and $R_1\;=\;R_2$ = H or $CH_3$, are investigated theoretically using the AM1 method. The experimental reactivity order is reproduced correctly by AM1 in all cases. The thermolysis proceeds through a six-membered cyclic transition state conforming to a retro-ene reaction, which can be conveniently interpreted using the frontier orbital theory of three-species interactions. The methyl group substituted at $C_{\alpha}\;or\;C_{\beta}$ is shown to elevate the ${\pi}$-HOMO of the donor fragment (Y = C) and depress the ${\sigma}^{\ast}$-LUMO of the acceptor fragment ($C_{\beta}$-H), increasing the nucleophilicity of Y toward ${\beta}$-hydrogen which in turn increases the reactivity. The two bond breaking processes of the $C_{\alpha}$-X and $C_{\beta}$-H bonds are concerted but not synchronous so that the reaction takes place in two stages as Taylor suggested. The initial cleavage of $C_{\alpha}$-X is of little importance but the subsequent scission of $C_{\beta}$-H occurs in a rate determining stage.

• 한국산업융합학회 논문집
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• 제15권4호
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• pp.95-101
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• 2012

In order to explain observed catalytic reactivity of aminophosphine complexes (seven-membered chelate), total energy, net charge, atomic orbital electron population, HOMO and LUMO energy of free ligands are calculated by PM3 methods of HyperChem 6.0. Free ligands are 1,2-bis{(diphosphino)amino}propane{$H_2PNHCH_2CH(CH_3)NHPH_2$;ligand 1},1,2-bis{(dimenylphosphino)amino}propane{$(CH_3)_2PNHCH_2CH(CH_3)NHP(CH_3)_2$;ligand 2},1,2-bis{(diphenylphosphino)amino}propane{$(C_6H_5)_2PNHCH_2CH(CH_3)NHP(C_6H_5)_2$;ligand 3}. The result showed that ligand 3 is stable than ligand 2 and ligand 1 and ligand 2 is stable than ligand 1 in total energy. Net charge of P atom is changed by H atom, methyl groups and phenyl groups in P atoms. Net charge of N atoms in ligands is nagative. The results of atomic orbital electron population are similar net charge data..

• 대한화학회지
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• 제53권6호
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• pp.671-676
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• 2009

밀도 함수이론을 사용해 철 부식 방지제로써 메톨(N-메틸-p-아미노페놀 설페이트)에 대한 기하학적 및 전자구조에 대한 연구가 처음으로 기술되었다. B3LYP/6-31G+(d,p) 기저세트를 사용해 기상 및 액상에서 HOMO, LUMO, 에너지갭 (${\Delta}E$), 멀리칸하전 ($q_M$), 자연원자하전 ($q_n$)과 같은 양자화학적 변수들이 계산되었다. 부식방지메카니즘을 이해하기 위해 부식방지효율과 양자화학적 변수들간의 연관성이 논의되었다.

• 대한화학회지
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• 제36권1호
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• pp.51-56
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• 1992

페로브스카이트구조를 갖는 $Pb(Zr_{1-y}Ti_y)O_3$ (PZT)계의 $Pb^{2+}$ 위치에 $Nd^{3+}$ 이온을 치환시키면서 그 결정구조와 결합특성을 X-선 회절분석법 및 적외선 분광광도법으로 알아보았으며, 이런 구조변화가 (Pb1-xNdx)(Zr1-yTiy)O3 (PNZT)계의 전기적 및 광학적 특성에 미치는 영향에 대하여 조사하였다. $Pb^{2+}$ 이온이 $Nd^{3+}$ 이온으로 치환될수록 정방성이 감소하며, 8${\sim}$12 mol% 치환되었을 때 입방정계의 구조이다. 결정내의 결합강도는 입방정게의 구조일 때 가장 강하고 높은 투광도를 나타냈으며, PNZT계 화합물이 투광도를 나타내는 것은 전자의 전하-이동 전이에 의한 것으로 생각된다.

• Corrosion Science and Technology
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• 제21권1호
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• pp.32-40
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• 2022

The o-Vanillin - Glutamine Schiff base [2-Hydroxy-3-Methoxy BenzylidineCarbomyl) -2-Butanoic Acid] was examined for low carbon steel corrosion inhibition in acid media. Weight loss studies were carried out at three different temperatures to determine the inhibition efficiency (IE). Electrochemical impedance spectroscopy revealed that the charge transfer resistance controlled the corrosion reaction and Tafel polarization indicated that the Schiff base acts as mixed mode of inhibitor. SEM images were recorded for the surface morphology of the low carbon steel surface. DFT studies revealed corrosion control mechanisms using quantum chemical parameters such as E_HOMO, E_LUMO, energy gap (∆E), chemical Hardness (η), chemical Softness (σ), Electronegativity (χ), and the fraction of electron transferred (∆N), which is calculated using Gaussian software 09. The gas-phase geometry was fully optimized in the Density Functional Theory (DFT/B3LYP-6-31G (d)).The DFT results are in good agreement with the experimental results. All the results proved that the Schiff Base (2-Hydroxy-3-Metoxy BenzylidineCarbomyl) -2-Butanoic is a suitable alternative for corrosion inhibition of low carbon steel in acid media.

• Bulletin of the Korean Chemical Society
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• 제29권3호
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• pp.627-640
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• 2008

The geometrical structures, atomic charges, and relative energies of tetracoordinated Pd complexes [PdCl3Z (Z = Cl-, Br-, OH?-, H2O, NH3, PH3), PdCl2Z2 (Z = Br-, OH?-, H2O, NH3, PH3), PdZ?2X (Z = Cl-, OH?-, H2O, NH3, PH3; X = oxalate, O2-?CCO2-), and PdZ2Y (Z = Cl?-, OH?-, H2O, NH3, PH3; Y = succinate, CO2-?CHCHCO2-?)] and the ligand exchange reactions of the Pd complexes were investigated using the ab initio second order Mller-Plesset perturbation (MP2) and Density Functional Theory (DFT) methods. The geometrical characteristics of the tetracoordinated Pd(II) complexes with mono- and bidentate ligands, the effects of the atomic charges for the charged and uncharged ligands, the (dz2-p ) interactions between the dz2-orbital of Pd(II) and the p -orbital of bidentates, and the relative stabilities between the isomers of PdCl2Z2 and PdZ2Y were investigated in detail. The potential energy surfaces for the ligand exchange reactions used for the conversions of {[PdCl2(NH3)2] + H2O} to {[PdCl(NH3)2(H2O)]+ + Cl?-?} and {[PdCl2(PH3)2] + H2O} to {[PdCl(PH3)2(H2O)]+ + Cl?-?]} were investigated. The geometrical structure variations, molecular orbital variations (HOMO and LUMO), and relative stabilities for the ligand exchange processes were also examined quantitatively.

• 한국염색가공학회:학술대회논문집
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• 한국염색가공학회 2011년도 제44차 학술발표회
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• pp.36-36
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• 2011

We synthesized new dye sensor based on indole compound. Through the UV-vis absorptions, we analyzed chemosensing properties to explain metal binding properties. The peak absorptions increased at 472 nm when added metal cations($Cd^{2+}$, $Cu^{2+}$, $Hg^{2+}$, $Fe^{2+}$, $Zn^{2+}$, $Ni^{2+}$ and $Cr^{3+}$) and gradually decreased the peak at 516 nm. Thus, this UV-Vis absorption behavior clearly showed the metal binding reaction. To measure energy level of used dye sensor, HOMO/LUMO energy value was calculated with cyclovaltagramm(CV) and using computational calculation method, in which we estimated the optimum structure of dye sensor. CV and computational calculation method, both compared to find suitable geometric structure. (with almost same energy values.) From the computational calculation, dye sensor has plane structure. So, Amine and ketone in the dye sensor faced each other and makes position to bind metal cations. In addition, these positions was supported pull-push electron system and generated MLCT process, when the dye sensor was bonded with the metal cations and resulted chemosensing properties. Through the electrochemical and computational calculation method analyze, we proposed the chemosensing principles that the dye sensor bind the metal cation between ketone and amine. Finally, the formation type of metal ion bindings was determined by Job's plot measurements.

• Macromolecular Research
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• 제14권3호
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• pp.343-347
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• 2006

A novel, blue light-emitting polymer, poly(phenyl-9,9-dioctyl-9',9'dihexanenitrile)fluorene (PPFC6N), containing an alkyl and cyano group in the side chain, was synthesized by Suzuki polymerization and characterized. The polymer structure was confirmed by $^1H-NMR$. The number average molecular weight and the weight average molecular weight of the obtained polymer were 9,725 and 9,943 respectively. The resulting polymer was thermally stable with a glass transition temperature ($T_g$) of $93^{\circ}C$, and was easily soluble in common organic solvents such as THF, toluene, chlorobenzene and chloroform. The HOMO and LUMO energy levels of the polymer were revealed as 5.8 and 2.88 eV by cyclic voltammetry study, respectively. The ITO/PEDOT:PSS (40 nm)/PPFC6N (80 m)/LiF (1 nm)/Al (150 nm) device fabricated from the polymer emitted a PL spectrum at 450 nm and showed a real blue emission for pure PPFC6N in the EL spectrum. When t-butyl PBD was introduced as a hole blocking layer, the device performance was largely improved and the EL spectrum was slightly shifted toward deep blue. The device with PPFC6N containing t-butyl PBD layer showed the maximum luminance of 3,200 $cd/m^2$ at 9.5 V with a turnon voltage of 7 V.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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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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• 제26권5호
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• pp.795-801
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• 2005

New PPV derivatives which contain electron-withdrawing trifluoromethyl ($CF_3$) group, poly[2-(2-ethylhexyloxy)-5-(4-trifluoro methylphenyl)-1,4-phenylenevinylene] (EH$CF_3$P-PPV), and poly[2-(2-ethylhexyloxy)-5-(3,5-bis(trifluoromethyl)-phenyl)-1,4-phenylenevinylene] (EHB$CF_3$P-PPV), have been synthesized by GILCH polymerization. As the result of the introduction of the electron-withdrawing $CF_3$ group to the phenyl substituent, the LUMO and HOMO energy levels of EH$CF_3$P-PPV (2.8, 5.1 eV) and EHB$CF_3$P-PPV (3.0, 5.3 eV) were lower than those of known poly[2-(2-ethylhexyloxy)-5-phenyl-1,4-phenylenevinylene] (EHP-PPV) (2.6, 4.9 eV). These polymers have been used as the electroluminescent (EL) layers in double layer lightemitting diodes (LEDs) (ITO/PEDOT/polymer/Al). EH$CF_3$P-PPV, and EHB$CF_3$P-PPV show maximum photoluminescence (PL) peaks at ${\lambda}_{max}$ = 550, 539 nm, and maximum EL peak at ${\lambda}_{max}$ = 545, 540 nm, respectively. The current-voltage-luminance (I-V-L) characteristics of the polymers show that turn-on voltages of EH$CF_3$P-PPV and EHB$CF_3$P-PPV are around 4.0 and 3.5 V, respectively.