期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 19, 期 32, 页码 10698-10707出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201300008
关键词
alkenes; aromaticity; density functional calculations; electronic structure; photochemistry
资金
- Carl Trygger Foundation
- National Science Foundation of China [21103142]
- Program for Changjiang Scholars and Innovative Research Team in University
- Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School
A density functional theory study on olefins with five-membered monocyclic 4n and 4n+2 -electron substituents (C4H3X; X=CH+, SiH+, BH, AlH, CH2, SiH2, O, S, NH, and CH-) was performed to assess the connection between the degree of substituent (anti)aromaticity and the profile of the lowest triplet-state ( (1)) potential-energy surface (PES) for twisting about olefinic CC bonds. It exploited both Huckel's rule on aromaticity in the closed-shell singlet ground state (S-0) and Baird's rule on aromaticity in the lowest * excited triplet state. 2CH(C4H3X) were categorized as set A and set B olefins depending on which carbon atom (C2 or C3) of the C4H3X ring is bonded to the olefin. (0)-antiaromatic/ (1)-aromatic (C5H4+) to strongly S-0-aromatic/ (1)- antiaromatic (C5H4-). Our hypothesis is that the shapes of the (1) PESs, as given by the energy differences between planar and perpendicularly twisted olefin structures in (1) [E( (1))], smoothly follow the changes in substituent (anti)aromaticity. Indeed, correlations between E( (1)) and the (anti)aromaticity changes of the C4H3X groups, as measured by the zz-tensor component of the nucleus-independent chemical shift NICS( (1);1)(zz), are found both for sets A and B separately (linear fits; r(2)=0.949 and 0.851, respectively) and for the two sets combined (linear fit; r(2)=0.851). For sets A and B combined, strong correlations are also found between E( (1)) and the degree of S-0 (anti)aromaticity as determined by NICS(S-0,1)(zz) (sigmoidal fit; r(2)=0.963), as well as between the (1) energies of the planar olefins and NICS(S-0,1)(zz) (linear fit; r(2)=0.939). (1) PESs suitable for adiabatic Z/E photoisomerization.
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