Kazumi Toriyama

Bio: Kazumi Toriyama is an academic researcher from Industrial Research Institute. The author has contributed to research in topics: Electron paramagnetic resonance & Radical. The author has an hindex of 24, co-authored 155 publications receiving 2297 citations. Previous affiliations of Kazumi Toriyama include Daikin.

Structures and reactions of radical cations of some prototype alkanes in low temperature solids as studied by ESR spectroscopy

Abstract: The structures and reactions of radical cations of prototype alkanes such as ethane, propane, isobutane, neopentane, etc. produced in SF6 and in other halocarbon matrices irradiated at 4 K have been extensively studied by ESR. The geometrical structures as well as the unpaired electron orbitals of these cations are unequivocally characterized based on the simple symmetry considerations as well as the INDO MO calculations. The ESR hyperfine coupling constants determined for these cations as well as their deuterated homologs give conclusive evidence for the interpretations. The unpaired electron in linear alkane cations is delocalized over the in‐plane C–H and C–C σ bonds forming delocalized σ radicals, whereas that in highly branched alkane cations is more confined to one of the C–C bonds forming localized σ radicals. The H1s spin density, giving a large hyperfine coupling in the linear alkane cations, is largely contributed from a direct participation of the C–H bond in the unpaired electron orbital, wher...

.sigma.-Delocalized radical cations [H(CH2)nH]+ of primary alkanes. ESR evidence

Abstract: This paper describes the first clear evidence that n-alkane cations (H(CH/sub 2/)/sub n/H)/sup +/ with extended structures are characterized as delocalized sigma radicals. The unpaired electron in the in-plane sigma molecular orbital delocalizes over the entire chain, giving the characteristic 1:2:1 three-line ESR spectra due to the strong hyperfine couplings with the two in-plane end protons. The weak couplings with the out-of-plane CH/sub 2/ protons are unresolvable for most of the cations as is expected from the unpaired electron in the in-plane orbital. The major hyperfine couplings with the in-plane protons decrease with increasing carbon number from 152 G for C/sub 2/H/sub 6//sup +/ to 16 G for n-C/sub 10/H/sub 22//sup +/ depending upon the sigma delocalization over the extended chain. The coupling values obtained from the INDO calculations using standard geometry are in good agreement with the observation, although a slight tilt of the CH/sub 3/ axis was required for the lower alkane cations with n less than or equal to 4.

Linear alkane radical cations prepared in synthetic zeolites by irradiation at 4 K: ESR evidence for ion-molecule reaction to form 1-alkyl radicals

Abstract: A new method is explored for preparing radical cations of alkanes in the system other than halogenated and neon matrices. The radical cations are produced from n-C/sub 6/H/sub 14/ and n-C/sub 8/H/sub 18/ adsorbed in synthetic zeolite (ZSM-5) by X-irradiation at 4 K. The ESR spectra show that the cations exhibit the planar extended structure without showing coexistence of the gauche conformer. With increasing the concentration of alkanes, the parent molecules are increasingly adsorbed as a dimer, from which the 1-alkyl radical is preferentially formed during irradiation at 4 K. This indicates that the n-alkane radical cation undergoes prompt deprotonation via the ion-molecular reaction when a neighboring alkane molecule exists as a proton acceptor in the adsorbed site. The formation of the 1-alkyl radical is consistent with the high unpaired electron density in the in-plane C-H bonds at the chain end of the radical cations. These results are closely related to their previous finding of the selective formation of the 1-alkyl radicals in the 4 K radiolysis of crystalline neat linear alkanes.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Chiral-Induced Spin Selectivity Effect.

Abstract: The chiral-induced spin selectivity (CISS) effect was recently established experimentally and theoretically. Here, we review some of the new findings and discuss applications that can result from special properties of this effect, like the reduction of the elastic backscattering in electron transfer through chiral molecules. The CISS effect opens the possibility of using chiral molecules in spintronics applications and for providing a deeper understanding of spin-selective processes in biology.