Barrier to methyl internal rotation of 1-methylvinoxy radical in the {approx. ovr X({sup 2}A") and {approx. ovr B({sup 2}A") states : experiment and theory.

Journal Article · Thu Nov 16 04:00:00 EST 2000 · J. Phys. Chem. A

DOI:https://doi.org/10.1021/jp001009q· OSTI ID:942897

Stanton, J F; Weisshaar, J C

The jet-cooled laser induced fluorescence spectrum of the {tilde B} {yields} {tilde X} electronic transition of the 1-methylvinoxy radical is assigned, including both hot and cold bands. The barrier to methyl internal rotation in both {tilde X} and {tilde B} states is determined by fitting pure torsional transitions to a one-dimensional hindered-rotor model. The resulting 3-fold torsional barrier parameters are V{sub 3}' = -740 {+-} 30 cm{sup -1} for the {tilde B} state (minimum-energy conformation with one methyl CH bond cis to the frame CO bond) and V{sub 3}' = +130 {+-} 30 cm{sup -1} for the {tilde X} state (methyl CH bond trans to CO). The intensity pattern clearly indicates a change in the preferred methyl conformation upon excitation, while ab initio calculations provide the absolute conformations in each state. A variety of ab initio methods including CASSCF, multireference Cl, and coupled-cluster techniques were applied to both the {tilde X} and the {tilde B} states of 1-methylvinoxy. Only the largest coupled-cluster calculations yield a {tilde B}-state barrier in good quantitative agreement with experiment. In unsubstituted vinoxy, a {tilde B}-state geometry adjusted earlier to fit experimental rotational constants is evidently in error.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 942897
• Report Number(s): ANL/CHM/JA-35731
• Journal Information: J. Phys. Chem. A, Journal Name: J. Phys. Chem. A Journal Issue: 45 ; Nov. 16, 2000 Vol. 104; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CALCULATION METHODS
ELECTRONIC STRUCTURE
EXCITATION
FLUORESCENCE
MATHEMATICAL MODELS
RADICALS
ROTATION