Detection of Trimethylenemethane by IR Spectroscopy: The Result of an Unexpected Photoisomerization of Methylenecyclopropane in a Halogen‐Doped Xe Matrix

The use of calculated IR spectra (ab initio) in the identification of highly reactive organic molecules and intermediates has proven to be a very useful tool to the experimental synthetic organic chemist. The results of recent collaborations between the authors and experimental groups are presented. These include the identification of o‐benzyne, cyclopentadienylideneketene, and trimethylenemethane prepared photochemically in low‐temperature matrices. In the first two examples, it is shown how the very useful experimental technique of obtaining the dichroic IR spectra of medium‐sized molecules greatly aided in the interpretation of the experimental IR spectra. © 1995 John Wiley & Sons, Inc.

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“…The IR spectrum was found to be in good agreement with that calculated with the 6 -3 1~* basis set (UMP2) [54] (see Fig. 7).…”

Section: Ysupporting

confidence: 50%

Calculated infrared spectra of unstable organic molecules and reactive intermediates

Hess

Smentek

1995

Int. J. Quantum Chem.

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“…Following early theoretical studies, 6,7 pioneering ESR The Journal of Physical Chemistry A ARTICLE measurements by Dowd and co-workers [7][8][9] established that the electronic ground state of TMM is triplet ( 3 A 2 0 ), which is in accord with Hund's rule for a case of a nondisjoint degenerate pair of nonbonding MOs. 3,4,10,11 Also, the IR spectrum of TMM was obtained by Maier and co-workers 12 in a halogen-doped xenon matrix. Subsequently, Lineberger and co-workers measured the photoelectron spectrum of the TMM radical anion, which revealed the vibronic structure of not only the ground triplet state but also an excited singlet state ( 1 A 1 ) of TMM.…”

Section: Introductionmentioning

confidence: 99%

Photoelectron Spectroscopic Study of the Oxyallyl Diradical

et al. 2011

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ABSTRACT:The photoelectron spectrum of the oxyallyl (OXA) radical anion has been measured. The radical anion has been generated in the reaction of the atomic oxygen radical anion (O •-) with acetone. Three low-lying electronic states of OXA have been observed in the spectrum. Electronic structure calculations have been performed for the triplet states ( 3 B 2 and 3 B 1 ) of OXA and the ground doublet state ( 2 A 2 ) of the radical anion using density functional theory (DFT). Spectral simulations have been carried out for the triplet states based on the results of the DFT calculations. The simulation identifies a vibrational progression of the CCC bending mode of the 3 B 2 state of OXA in the lower electron binding energy (eBE) portion of the spectrum. On top of the 3 B 2 feature, however, the experimental spectrum exhibits additional photoelectron peaks whose angular distribution is distinct from that for the vibronic peaks of the 3 B 2 state. Complete active space selfconsistent field (CASSCF) method and second-order perturbation theory based on the CASSCF wave function (CASPT2) have been employed to study the lowest singlet state ( 1 A 1 ) of OXA. The simulation based on the results of these electronic structure calculations establishes that the overlapping peaks represent the vibrational ground level of the 1 A 1 state and its vibrational progression of the CO stretching mode. The 1 A 1 state is the lowest electronic state of OXA, and the electron affinity (EA) of OXA is 1.940 ( 0.010 eV. The 3 B 2 state is the first excited state with an electronic term energy of 55 ( 2 meV. The widths of the vibronic peaks of theX 1 A 1 state are much broader than those of theã 3 B 2 state, implying that the 1 A 1 state is indeed a transition state. The CASSCF and CASPT2 calculations suggest that the 1 A 1 state is at a potential maximum along the nuclear coordinate representing disrotatory motion of the two methylene groups, which leads to three-membered-ring formation, i.e., cyclopropanone. The simulation ofb 3 B 1 OXA reproduces the higher eBE portion of the spectrum very well. The term energy of the 3 B 1 state is 0.883 ( 0.012 eV. Photoelectron spectroscopic measurements have also been conducted for the other ion products of the O •-reaction with acetone. The photoelectron imaging spectrum of the acetylcarbene (AC) radical anion exhibits a broad, structureless feature, which is assigned to theX 3 A 00 state of AC. The ground ( 2 A 00 ) and first excited ( 2 A 0 ) states of the 1-methylvinoxy (1-MVO) radical have been observed in the photoelectron spectrum of the 1-MVO ion, and their vibronic structure has been analyzed.

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“…2 Since then, TMM has attracted avid attention of theoreticians and experimentalists. [32][33][34][35][36][37][38][39] In addition to its fascinating electronic structure, there are other reasons for such a persistent interest. For example, TMM is an intermediate in the formation and rearrangements of methylenecyclopropanes.…”

Section: Introductionmentioning

confidence: 99%

“…38 Recently, the infrared spectrum of the triplet ground state was reported. 36,37 Additional information about TMM's vibrational frequencies was derived from the photoelectron spectrum of the corresponding anion. 39 Previous theoretical studies of TMM included investigation of the potential energy surfaces ͑PESs͒ of the two lowest singlet states by Borden and Davidson.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of the trimethylenemethane diradical in its ground and electronically excited states: Bonding, equilibrium geometries, and vibrational frequencies

Slipchenko

Krylov

2003

The Journal of Chemical Physics

109

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Accurate equilibrium properties of the ground and the three lowest excited states of the trimethylenemethane ͑TMM͒ diradical are calculated by using the novel spin-flip electronic structure method. Changes in structures and vibrational frequencies upon excitation are analyzed. The bonding picture in different states of TMM is derived from wave function analysis and comparison of equilibrium structures with typical values of coupled-cluster ͑CC͒ bond lengths, e.g., a double CC bond in ethylene, a single CC bond in twisted ethylene, and a bond in the allyl radical.

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Detection of Trimethylenemethane by IR Spectroscopy: The Result of an Unexpected Photoisomerization of Methylenecyclopropane in a Halogen‐Doped Xe Matrix

Cited by 38 publications

References 26 publications

Calculated infrared spectra of unstable organic molecules and reactive intermediates

Calculated infrared spectra of unstable organic molecules and reactive intermediates

Photoelectron Spectroscopic Study of the Oxyallyl Diradical

Electronic structure of the trimethylenemethane diradical in its ground and electronically excited states: Bonding, equilibrium geometries, and vibrational frequencies

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