High-resolution ESR spectroscopy and structure of the acetaldehyde radical cation (CH/sub 3/CHO/sup +/) in neon matrices at 4 K: comparison with results in freon matrices
Detailed ESR studies are reported for the acetaldehyde radical cation (CH/sub 3/CHO/sup +/) trapped in neon matrices. The cation was generated by photoionization, electron bombardment, or laser multiphoton ionization of dilute acetaldehyde neon mixtures (10/sup 2/ to 10/sup 4/ dilution factor) during codeposition on a flat target at 4 K. Its ESR spectrum was well resolved and showed strong preferential orientation effects, two sets of strong features being observed for field directions in the target plane, while another set of weaker line components became strongly enhanced when the field was applied normal to this plane. These results indicate that the cations are aligned with their CCHO planes parallel to the deposition surface. Accordingly, the largest principal value of the g tensor is found to perpendicular to the CCHO plane, as previously determined for the formaldehyde cation (H/sub 2/CO/sup +/). The measured values of the g and aldehydic /sup 1/H hyperfine tensors are consistent with the assignment of the unpaired electron to the nonbonding oxygen-centered 10a' molecular orbital which is, however, about 50% delocalized onto the aldehydic hydrogen (1s) and methyl carbon (2p) orbitals. The g and aldehydic /sup 1/H A tensor components are the following: g/sub x/ = 2.0069 (3), A/sub x/ = 355 (1) MHz; g/sub z/ = 2.0019 (6), A/sub z/ = 374 (3) MHz, g/sub y/ = 2.0026 (3), A/sub y/ = 353 (1) MHz. The much smaller hyperfine interaction (4.3 MHz) with the hydrogens of the methyl group is exceedingly well resolved into a 1:1:1:1 quartet at 4 K with the field normal to the CCHO plane. In contrast to the neon studies, the ESR spectra of the acetaldehyde radical cation in Freon matrices show much poorer resolution and are complicated by the appearance of a highly structures anisotropic /sup 35/Cl hyperfine interaction below 120 K.
- Research Organization:
- Furman Univ., Greenville, SC
- OSTI ID:
- 5523097
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:2; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ACETALDEHYDE
ALDEHYDES
CATIONS
CHARGED PARTICLES
DATA
ELECTRON SPIN RESONANCE
ELEMENTS
EXPERIMENTAL DATA
FLUIDS
FREONS
GASES
HALOGENATED ALIPHATIC HYDROCARBONS
INFORMATION
IONS
MAGNETIC RESONANCE
MATRIX ISOLATION
MOLECULAR STRUCTURE
NEON
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RADICALS
RARE GASES
RESOLUTION
RESONANCE
ULTRALOW TEMPERATURE