Ab Initio Quantum Chemistry Calculations on the Electronic Structure of Heavier Alkyne Congeners: Diradical Character and Reactivity
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- 作者：Yousung Jung ; Marcin Brynda ; Philip P. Power ; and Martin Head-Gordon
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：June 7, 2006
- 年：2006
- 卷：128
- 期：22
- 页码：7185 - 7192
- 全文大小：305K
- 年卷期：v.128,no.22(June 7, 2006)
- ISSN：1520-5126
文摘
The electronic structure of the heavier congeners of alkynes has been studied with emphasison characterizing their extent of diradical character. Four orbitals play a crucial role in determining theelectronic structure in planar trans-bent geometries. Two are associated with an out-of-plane 
interaction, and *, and two are associated with in-plane interactions and/or in-plane lone pairs, LP(n-) and LP*(n+).The ordering of these orbitals can change depending upon geometry. One extreme, corresponding to thelocal minimum for Si-Si and Ge-Ge, is a diradicaloid multiple-bonding configuration where LP and arenominally occupied. Another extreme, corresponding to a local minimum for Sn-Sn, is a relatively closed-shell single-bond configuration where LP and LP* are nominally occupied. This ordering leads to predictedbond shortening upon excitation from singlet to triplet state. For the heavier elements, there appears to bevery little energy penalty for large geometric distortions that convert from one ordering to the other on thesinglet surface. The implications of these results with respect to experimental observations are discussed.
interaction, and *, and two are associated with in-plane interactions and/or in-plane lone pairs, LP(n-) and LP*(n+).The ordering of these orbitals can change depending upon geometry. One extreme, corresponding to thelocal minimum for Si-Si and Ge-Ge, is a diradicaloid multiple-bonding configuration where LP and arenominally occupied. Another extreme, corresponding to a local minimum for Sn-Sn, is a relatively closed-shell single-bond configuration where LP and LP* are nominally occupied. This ordering leads to predictedbond shortening upon excitation from singlet to triplet state. For the heavier elements, there appears to bevery little energy penalty for large geometric distortions that convert from one ordering to the other on thesinglet surface. The implications of these results with respect to experimental observations are discussed.