An electron spin resonance investigation of the 12C11B12C, 12C11B13C, and 13C11B13C radicals in neon, argon, and krypton matrices: Comparison with ab initio calculations

Abstract

The 11 electron CBC radical has been generated by the pulsed laser vaporization of elemental carbon–boron mixtures and trapped in neon, argon and krypton matrices for detailed electron spin resonance (ESR) studies. Extensive comparisons of the experimental nuclear hyperfine A tenors for carbon and boron were made with a variety of ab initio computational results that involved different levels of theory and basis sets. These new ESR results agree with recent vibrational studies of CBC that show it to have a nonlinear symmetric geometry with a 2A1 electronic ground state. These ESR results provide a description of the singly occupied molecular orbital. The spin density resides primarily on boron in 2s and 2pz orbitals, however a complete resolution of the 13C hyperfine structure does show that approximately 20% resides on the carbon atoms.

Electron spin resonance studies of 45Sc17O, 89Y17O, and 139La17O in rare gas matrices: Comparison with ab initio electronic structure and nuclear hyperfine calculations

“…2 The final set of magnetic parameters that produce agreement with the observed ESR lines within the experimental uncertainty for ScO, YO, and LaO is listed in Table II. A highly resolved and distinct 17 O sextet hyperfine structure is shown for the 45 Sc:M I ϭϪ5/2 transition of 45 Sc 17 O in Fig. 4 for a neon matrix sample at 4 K. The more intense features near the centers of the 17 O sextets for the parallel and perpendicular absorptions result from 45 Sc 16 O radicals which are also present in the matrix sample. Extracting the A ʈ and A Ќ values from the observed spectra is straightforward given the small magnitude of the 17 O hyperfine interaction.…”

“…2 for an expanded-sweep presentation of the 45 Sc:M I ϭ7/2, Ϫ1/2, and Ϫ5/2 transitions. Given the large magnitude of the hyperfine splitting for 45 Sc, the spectral features extended from 541 to 5762 G. A simulated ESR spectrum of 45 Sc 16 O showing all eight hyperfine components is shown in Fig. 3.…”

“…6 with the low-field 17 O sextets shown in the lower half. While there is considerable overlap between the parallel and perpendicular lines of 17 O, it was possible to independently analyze the 89 Y 17 O spectrum-an analysis that yielded the same g tensor and 89 Y A tensor results as that obtained from the 89 Y 16 O spectrum. Part of this analysis included detailed comparisons between observed and simulated spectra at various inputed values of the Lorentzian linewidth parameter.…”

“…14 Previous work in our laboratory has shown that matrix ESR samples prepared from pulsed laser vaporization sources yield higher quality spectra ͑greater intensity and narrower lines͒ and fewer multiple site complications compared to the trapping of radicals from more conventional high temperature sources. 15,16 Pulsed laser vaporization of the pure metal in the presence of isotopically labeled oxygen gas presents an excellent experimental opportunity to generate the M 17 O radicals for matrix ESR study. The fully resolved A tensors for 17 O and those of the metal atoms provide a complete experimental description of the spin-density distribution in the SOMO.…”

Double Aromaticity in Monocyclic Carbon, Boron, and Borocarbon Rings Based on Magnetic Criteria

“…Diatomic and larger BC clusters have been studied by using mass spectrometry [103,104] and EPR. [105][106][107] Other studies have probed the structure of B n C m (n + m = 2-5) clusters. [108][109][110][111][112][113][114][115][116][117][118] Park [119] described structural and bonding trends in a series of isoelectronic borocarbon compounds.…”