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Electronic Structure of Oxyallyl Diradical: A Photoelectron Spectroscopic Study. Takatoshi Ichino , Rebecca L. Hoenigman, Adam J. Gianola, Django H. Andrews, and W. Carl Lineberger JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 Weston T. Borden

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electronic structure of oxyallyl diradical a photoelectron spectroscopic study

Electronic Structure of Oxyallyl Diradical:A Photoelectron Spectroscopic Study

Takatoshi Ichino, Rebecca L. Hoenigman, Adam J. Gianola,

Django H. Andrews, and W. Carl Lineberger

JILA and Department of Chemistry and Biochemistry,

University of Colorado, Boulder, CO 80309

Weston T. Borden

Department of Chemistry, University of North Texas

Denton, TX 76203

Stephen J. Blanksby

Department of Chemistry, University of Wollongong

Wollongong, NSW 2522, Australia

trimethylenemethane tmm vs oxyallyl
Trimethylenemethane (TMM)vsOxyallyl

TMM diradical

Oxyallyl diradical

tmm diradical intermediate in thermal rearrangement of methylenecyclopropane mcp
TMM Diradical intermediate in thermal rearrangement of methylenecyclopropane (MCP)

TMM diradical

intermediate

Hydrocarbon Thermal Isomerizations

J.J. Gajewski, Academic Press, 1981

JACS1982, 104, 967, Davidson and Borden

trimethylenemethane tmm diradical
Trimethylenemethane (TMM) diradical

4 p electrons

Triplet

Singlet

y4

y4

y2

y3

y2

y3

y1

y1

several ways to construct

singlet wave functions

tmm triplet singlet wave functions
TMM triplet, singlet wave functions

HF energy

Triplet wave function

3A2′ (3B2)

2h + J23 – K23

Singlet wave functions

1Ex′ (1B2)

2h + J23 + K23

1Ey′ (1A1)

2h + J22 – K23

1A1′ (1A1)

2h + J22 + K23

where J22− J23 = K23

sizeable exchange interaction

triplet ground state (ESR measurements by Dowd, 1960’s)

configuration interaction for 1 e x tmm
Configuration interaction for 1Ex′ TMM

1Ex′

mixed with

Y3→Y4excitation

Y1→Y3excitation

CI

“allyl + p”

reduction of electron repulsive interaction

at the expense of p bonding energy

JACS1976, 98, 2695, Borden

configuration interaction for 1 e y tmm
Configuration interaction for 1Ey′ TMM

1Ey′

CI with Y3→Y4 and Y1→ Y4 excitation

CI

“double bond + p + p”

reduction of electron repulsive interaction

at the expense of p bonding energy

electron detachment from tmm anion
Electron detachment from TMM anion

JACS1994, 116, 6961, Wenthold et al.

EA (TMM) = 0.431 ± 0.006 eV

E (X 3A2′ ― b 1A1) = 0.699 ± 0.006 eV

CCC bend in 3A2′ : 425 ± 20 cm-1

in 1A1 : 325 ± 20 cm-1

JACS1996, 118, 475, Wenthold et al.

oxyallyl intermediates
Oxyallyl intermediates

Thermal stereomutation of cyclopropanone

JACS1970, 92, 7488, Greene et al.

Photochemistry of quadricyclanone

JOC1991, 56, 1907, Ikegami et al.

oxygen substitution oxyallyl diradical
Oxygen substitution: Oxyallyl diradical

degeneracy of a2 and 2b1 lifted in oxyallyl

JCS,PT21998, 1037, Borden et al.

hartree fock for non degenerate system
Hartree-Fock for non-degenerate system

energy

Triplet wave function

3B2

h2 + h3 + J23 – K23

Singlet wave functions

1B2

h2 + h3 + J23 + K23

1A1

h2 + h3 + (J22 + J33)/2

± [K232 + {h2-h3+(J22-J23)}2]1/2

1A1

The ground state becomes 1A1 if J22− J23 + K23 < h3 – h2

oxyallyl anion o acetone reaction
Oxyallyl anion : O‾ + acetone reaction

“M−H2” ions

oxyallyl

radical anion

carbene

radical anion

“M−H” ion

acetone

enolate anion

photoelectron spectrum of m h ion
Photoelectron spectrum of M−H ion

OH‾ + acetone reaction

s radical

p radical

“M−H”

acetone enolate

JPC1982, 86, 4873, Ellsion et al.

photoelectron spectrum of m h 2 and m h ions
Photoelectron spectrum of M−H2 and M−H ions

O‾ + acetone reaction

“M−H2”

“M−H2”

“M−H”

photoelectron spectrum of m h 2 ion
Photoelectron spectrum of M−H2 ion

“M−H2”

detachment from

O lone-pair orbitals

“M−H2”

photoelectron spectrum of m h 2 ion1
Photoelectron spectrum of M−H2 ion

oxyallyl

X1A1

a3B2

EA = 1.945 ± 0.010 eV

Te (3B2) = 0.056 ± 0.005 eV

franck condon simulation for the 3 b 2 oxyallyl diradical
Franck-Condon simulation for the 3B2 oxyallyl diradical

CCC bending mode

400 ± 20 cm-1

B3LYP/6-311++G(d,p) calculations on 2A2 anion and 3B2 neutral

conclusions
Conclusions
  • The 351 nm photoelectron spectrum of oxyallyl anion has been measured. The Franck-Condon fitting is successful for the transition from the 2A2 ground state of oxyallyl anion to the 3B2 state of oxyallyl, based on B3LYP/6-311++G(d,p) optimized geometries and normal modes. Vibrational progression is observed for a CCC bending mode of 400 ± 20 cm-1 in the 3B2 spectrum.
  • Angular distributions of the photoelectrons from oxyallyl anion reveal an electronic state of oxyallyl to the lower electron binding energy side of the 3B2 spectrum. This is assigned to the 1A1 ground state of oxyallyl. The electron affinity of oxyallyl is 1.945 ± 0.010 eV, and the term energy for the 3B2 state is 0.056 ± 0.005 eV.
acknowledgements
Acknowledgements
  • Adam J. Gianola, Django H. Andrews, Rebecca L. Hoenigman, and

W. Carl Lineberger, University of Colorado at Boulder

  • Stephen J. Blanksby, University of Wollongong, Australia
  • Weston T. Borden, University of North Texas
  • NSF, AFOSR