Electronic structure analysis of iron(III)-porphyrin complexes by X-ray absorption spectra at the C, N and Fe K-edges.

X-ray absorption near edge structure (XANES) measurements at the C, N, and Fe K absorption edges were performed for iron(III)-tetraphenylporphyrin (FeTPP), iron(III)-tetrakis(p-carboxyphenyl)porphyrin (FeTCPP), and iron(III)-tetrakis(p-sulfonatophenyl)porphyrin (FeTSPP). The spectral shapes differ in the Fe K XANES, but not in C and N K XANES among FeTPP, FeTCPP, and FeTSPP. Crosschecks of XANES data for C, N, and Fe K absorption edges in combination with discrete variational (DV)-Xalpha molecular orbital (MO) calculations indicate that each p-electron-withdrawing group on four meso-phenyl substitutes in an Fe(III)-porphyrin complex brings about a unique electron state through the complex because of the electron-withdrawal strength, itself. Consequently, they affect the positive charge of the center Fe(III) ion.     

Local structure of nitrogen atoms in a porphine ring of mesophenyl substituted porphyrin with an electron-withdrawing group using X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.

This study investigated the protonation of nitrogen atoms in porphyrins with meso-phenyl p-substituted by an electron-withdrawing group using N 1s X-ray photoelectron spectroscopy (XPS), the N K X-ray absorption near-edge structure (XANES), and the discrete variational (DV)-Xalpha molecular orbital (MO) method. Both tetraphenylporphyrin (TPP) and tetrakis(p-sulfonatophenyl)porphyrin (TSPP) have a single structure: the former has two protonated and two non-protonated N atoms in the porphine ring; the latter has four protonated N atoms in the porphine ring. In contrast, a combination of XPS, XANES, and DV-Xalpha MO calculations shows that tetrakis(p-carboxyphenyl)porphyrin (TCPP) has a dual structure: one structure has two protonated and two non-protonated N atoms; the other has four protonated N atoms. Furthermore, this result was also considered based on the protonation constants of N atoms in the porphyrins. The correlation between the strength of electron-withdrawing groups and protonation to N atoms in porphyrins can be described using the spectral patterns of the N 1s XPS and N K XANES spectra.     

Efficient N-sulfenylation of 2-azetidinones using S-substituted thiophthalimides

Reaction of N-unsubstituted β-lactams with various S-substituted thiophthalimides provides an efficient route to the corresponding N-thio-2-azetidinones.     

Time-resolved ESR study of the lowest excited triplet states of para-quinones in glassy matrices at 77 k

The lowest excited nπ* triplet of 9.10-anthraquinone, 1.4-naphthoquinone and 1,4-benzoquinone were studied in glassy matrices at 77 K using a time-resolved ESR method. The D value of the triplet state of 9,10-anthraquinone varied from ?0.351 cm^?1 in a polar solvent to ?0.318 cm^?1 in a non-polar solvent. Both 1,4-naphthoquinone and 1,4-benzoquinone in polar solvents showed triplet state spectra with a D value of ?0.330 cm^?1. A computer simulation revealed the existence of widely distributed zero-field splitting parameters in the glassy condition. These data are compared with an analysis of CIDEP results of para-quinones.     

The primary fragmentation step of isoxazole upon electron impact. A correlation with photochemistry

Three isomeric compounds, I, II and III, were prepared and their mass spectra recorded. Comparisons of the spectra showed that the fragmentation of I proceeds only by way of II, and that II itself is transformed in part to III upon electron impact. It is suggested that selective ionization of each one of the two isolated functional groups in II may afford two isomeric radical ions, IIa and IIb. A possible interrelation to the photochemistry of these compounds is also discussed.     

Beta-ray angular distribution in aligned 12B and 12N and G-parity irregular induced tensor current

We made an explicit formula for beta-ray angular distribution by taking into account the radiative corrections, Coulomb corrections of the finite-size nucleus, weak magnetism, induced pseudoscalar, second-class induced tensor, and contributions of the d-wave leptons. Experimental data on the beta decays of aligned ¹²B and ¹²N given at Osaka are carefully investigated, and it is shown that these data are compatible with no induced tensor current, $\text{?}{}_{\mathrm{T}}\text{?}{}_{\mathrm{A}}\text{=}\text{?(0.44 +-0.88)}\text{2M}$. The nuclear parameter y is 3.3±0.9 in excellent agreement with the predicted value 3.6.