• Bulletin of the Korean Chemical Society
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• 제28권1호
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• pp.89-94
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• 2007

The new pinane derivative containing unique multifused ring system was synthesized. The crystal, molecular and electronic structure of the title compound has been determined. Both pinane ring systems have the same conformation. The five-membered oxazolidine ring exists in twisted chair conformation. The structure is expanded through O-H…O hydrogen bond to semiinfinite hydrogen-bonded chain. The bond lengths and angles in the optimised structure are similar to the experimental ones. The CH3 and CH2 groups (except this of oxazolidine ring) are negatively charged whereas the CH groups are positively charged. The largest negative potential is on the oxygen atoms. The C-N natural bond orbitals are polarised towards the nitrogen atom (ca. 61% at N) whereas the C-O bond orbitals are polarised towards the oxygen atom (ca. 67% at O). It is consistent with the charges on the nitrogen and oxygen atom of oxazolidine ring and the direction of the dipole moment vector (3.08 Debye).

• 대한화학회지
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• 제50권4호
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• pp.281-290
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• 2006

Hybrid DFT 계산 방법을 이용하여 1H-Indene과 Mono-sila-1H-indene 분자의 구조와 특성에 관한 이론적 연구를 수행하였다. 이 분자들의 방향족성 특성 연구를 위하여 MO, 비등방성 자기 민감도 등을 계산하였다. 1H-Indene과 Mono-sila-1H-indene 분자들에 대한 X8-X9 결합의 상대적인 안정도와 특성을 이해하기 위하여 NBO 계산을 수행하였다. 그 결과, 8, 9 위치의 Si 원자들이 C 원자들로 치환되었을 때, p orbital의 기여도가 증가하였다. 이러한 결과는 X8-X9 결합 길이는 하이브리드 오비탈의 p 오비탈 기여도에 크게 영향받는 사실을 보여준다. NBO계산을 통하여 X8-X9로부터 *X8-X9 결합 오비탈로의 비편재화에 기인하는 정량적인 에너지 안정화 세기를 결정하였다. MO 분석 결과 연구 대상 분자들의 방향족성은 3개의 비편재화된 pMO와 2개의 비편재화된 sMO에 의해서 주로 영향 받는다는 사실을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제25권4호
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• pp.452-459
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• 2004

The geometrical structures of various isomers of hexafluoro-1,3-butadiene (HFBD), tetrafluoro-1,3-butadiene (TFBD), and difluoro-1,3-butadiene (DFBD) have been studied theoretically. Natural steric and natural resonance theory (NRT) analyses indicate that the lower energy of skew s-cis conformer of hexafluoro-1,3-butadiene than that of the s-trans conformer is originated from the strong steric repulsions between fluorine atoms particularly in the s-trans conformer. The resonance structures generated by NRT also show that the lone electron pairs of fluorine atoms effectively extend the conjugation, and the large differences in energy among the structural isomers of tetrafluoro-1,3-butadiene and difluoro-1,3-butadiene are in part attributed to the differences in the delocalization energies, in addition to the steric repulsion between fluorine atoms. Other interatomic interactions, such as hydrogen bonding, also play important roles in determination of the structures of isomers of tetrafluoro-1,3-butadiene and difluoro-1,3-butadiene.

• 대한화학회지
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• 제57권4호
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• pp.461-471
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• 2013

Optimized geometrical structure, atomic charges, molecular electrostatic potential, nonlinear optical (NLO) effects and thermodynamic properties of the title compound N-(2,5-methylphenyl)salicylaldimine (I) have been investigated by using ab initio quantum chemical computational studies. Calculated results showed that the enol form of (I) is more stable than keto form. The solvent effect was investigated for obtained molecular energies, hardneses and the atomic charge distributions of (I). Natural bond orbital and frontier molecular orbital analysis of the title compound were also performed. The total molecular dipole moment (${\mu}$), linear polarizability (${\alpha}$), and first-order hyperpolarizability (${\beta}$) were calculated by B3LYP method with 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) and 6-311++G(d,p) basis sets to investigate the NLO properties of the compound (I). The standard thermodynamic functions were obtained for the title compound with the temperature ranging from 200 to 450 K.

• Carbon letters
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• 제16권3호
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• pp.192-197
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• 2015

In the present work, we propose a molecule (C₁₄H₁₄) that can be used as a building block of hexagonal diamond-type crystals and nanocrystals, including wurtzite structures. This molecule and its combined blocks are similar to diamondoid molecules that are used as building blocks of cubic diamond crystals and nanocrystals. The hexagonal part of this molecule is included in the C₁₂ central part of this molecule. This part can be repeated to increase the ratio of hexagonal to cubic diamond and other structures. The calculated energy gap of these molecules (called hereafter wurtzoids) shows the expected trend of gaps that are less than that of cubic diamondoid structures. The calculated binding energy per atom shows that wurtzoids are tighter structures than diamondoids. Distribution of angles and bonds manifest the main differences between hexagonal and cubic diamond-type structures. Charge transfer, infrared, nuclear magnetic resonance and ultraviolet-visible spectra are investigated to identify the main spectroscopic differences between hexagonal and cubic structures at the molecular and nanoscale. Natural bond orbital population analysis shows that the bonding of the present wurtzoids and diamondoids differs from ideal sp³ bonding. The bonding for carbon valence orbitals is in the range (2s^0.982p^3.213p^0.02)-(2s^0.942p^3.313p^0.02) for wurtzoid and (2s^0.932p^3.293p^0.01)-(2s^0.992p^3.443p^0.01) for diamantane.