The cyclooctatetraenyl radical (C8H7) has been identified as an intermediate in combustion reactions of unsaturated hydrocarbons.  The potential energy surface of this radical exhibits two minimum-energy geometries: one a 1,3,5,7-tetraenyl form similar to the familiar COT parent molecule, and the other a more stable 1,2,4,6-tetraenyl radical stabilized by a 5-center, 5-electron allyl-type resonance.  However, at combustion temperatures, the two forms are expected to rapidly interconvert.  To investigate the vibrational dynamics that connect these two geometries, the vibrational potential energy surface has been mapped along three coordinates�an angle, a linear combination of bond distances, and a linear combination of dihedrals�with the intention of addressing the most anharmonic vibrational modes in our analysis.  The surface is constructed from an IMLS (interpolating moving least squares) scan of partially optimized CCSD/cc-pVDZ structures, with convergence checks carried out at selected points using CCSD(T), cc-pVTZ, and single-point CCSD-F12a/cc-PVDZ-F12a calculations.  The vibrational eigenvalues and eigenfunctions are then calculated using a finite element method-based numerical integration.  This work seeks to yield insights about the C8H7  isomerization, as well as similar double-well potentials predicted for other alkenyl radicals.

Vibrational energies and wavefunctions on a 3D tonal, coupled cluster isomerization potential energy surface of cyclooctatetraenyl radical

248th National Meeting (2014)

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