The electronic structure of 5-methylhexa-1,2,4-triene-1,3-diyl, the first representative of highly delocalized triplet ethynylvinylcarbenes, from ESR spectroscopy data and quantum chemical calculations

被引：0
作者：
E. Ya. Misochko
A. V. Akimov
A. A. Masitov
D. V. Korchagin
S. M. Aldoshin
S. E. Boganov
K. N. Shavrin
V. D. Gvozdev
M. P. Egorov
O. M. Nefedov
机构：
[1] Russian Academy of Sciences,Institute of Problems of Chemical Physics
[2] Russian Academy of Sciences,N. D. Zelinsky Institute of Organic Chemistry
来源：
Russian Chemical Bulletin | 2011年 / 60卷
关键词：
carbenes; matrix isolation; ESR spectroscopy; zero-field splitting tensor; electronic spin-spin interactions; quantum chemical calculations; density functional theory;
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摘要：
The ESR spectrum of the first representative of highly conjugated triplet ethynylvinylcarbenes, 5-methylhexa-1,2,4-triene-1,3-diyl (1), was recorded in solid argon matrix. The zero-field splitting (ZFS) parameters of carbene 1 (D = 0.5054±0.0006 cm−1 and E = 0.0045±0.0002 cm−1) determined from the experimental ESR spectrum are in between the corresponding parameters of ethynylcarbene C3H2 (2) and vinylcarbene C3H4 (3): D(3) < D(1) < D(2) and E(2) < E(1) < E(3). Quantum chemical calculations of the ZFS parameters of 1, 2, and 3 have been carried out for the first time using two DFT-based approaches, RODFT and UDFT. An analysis of the experimental and theoretical ZFS parameters shows that carbene 1 is characterized by a greater extent of delocalization of the spin density of unpaired electrons than carbenes 2 and 3. The characteristic structural fragments of carbene 1 possess the principal features of the electronic structure of both ethynylcarbene (2) and vinylcarbene (3), respectively. Magnetic spin-spin interactions are identical in carbenes 1 and 2. The dominant contribution to D in 1 and 2 results from the one-center spin-spin interactions on carbon atoms in the propynylidene group, which are subjected to strong spin polarization.
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页码：2180 / 2187
页数：7
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