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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 50, Number 4
JKCSEZ 50(4)
August 20, 2006 

 
Title
Theoretical Studies on the Structure and Aromaticity of 1H-Indene and Mono-sila-1H-Indene

1H-Indene과 Mono-sila-1H-Indene의 구조와 방향족성에 대한 이론적 연구
Author
Reza Ghiasi*, Majid Monnajemi

Reza Ghiasi*, Majid Monnajemi
Keywords
1H-Indene, Sila-1H-Indene, Aromaticity, magnetic properties, Natural bond orbital (NBO) , 1H-Indene, Sila-1H-Indene, Aromaticity, magnetic properties, Natural bond orbital (NBO)
Abstract
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 σX8-X9로 부터 σ*X8-X9 결합 오비탈로의 비편재화에 기인하는 정량적인 에너지 안정화 세기를 결정하였다. MO 분석 결과 연구대상 분자들의 방향족성은 3개의 비편재화된 pMO와 2개의 비편재화된 sMO에 의해서 주로 영향 받는다는 사실을 알 수 있었다.

The electronic structure and properties of the 1H-indene and mono-sila-1H-indene series have been investigated using basis set of 6-31G(d, p) and hybrid density functional theory. Basic measures of aromatic character derived from structure, molecular orbitals, a variety of magnetic criteria (magnetic isotropic and anisotropic susceptibilities) are considered. Energetic criteria suggest that In(Si7) enjoy conspicuous stabilization. However, by magnetic susceptibility isotropic this system are among the least aromatic of the family: Within their isomer series, In(Si4) is the most aromatic using this criteria. Natural bond orbital (NBO) analysis method was performed for the investigation of the relative stability and the nature of the 8-9 bonds in 1H-indene and mono-sila-1H-indene compounds. The results explained that how the p character of natural atomic hybrid orbital on X8 and X9 (central bond) is increased by the substitution of the C8 and C9 by Si. Actually, the results suggested that in these compounds, the X8-X9 bond lengths are closely controlled by the p character of these hybrid orbitals and also by the nature of C-Si bonds. The magnitude of the molecular stabilization energy associated to delocalization from σX8-X9 and to σ* X8-X9 bond orbital were also quantitatively determined. Molecular orbital (MO) analysis further reveal that all structure has three delocalized π MOs and two delocalized σ MOs and therefore exhibit the aromaticity.

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