EPR AND TREPR SPECTROSCOPIC STUDIES OF ANTIOXIDANT SESAMOLYL AND RELATED PHENOXYL RADICALS

Abstract Sesamolyl and related phenoxyl radicals were studied by conventional and time-resolved electron paramagnetic resonance (EPR) spectroscopic techniques. Continuous UV irradiation of sesamol in benzene produces two types of radicals. Based on the hyperfine coupling values obtained we determined that one is the neutral sesamolyl radical and the others are the dimer radicals. Comparison was made with related compounds, especially 3,4-dime-thoxyphenol. We found that the 3,4-dimethoxyphenoxyl radical had a shorter lifetime than the neutral sesamolyl radical. The EPR results obtained suggest that a near perpendicular orientation of the oxygen p -orbitals with respect to the benzene ring of sesamol makes the radical more stable. This stability may be important for the antioxidant properties.     

Silver(I) compounds consisting of [2.2]paracyclophane: reversible guest-driven solid-state transformation and incorporation behavior

Reaction of [2.2]paracyclophane with silver(I) heptafluorobutyrate (AgC3F7CO2) has isolated three novel networks: [Ag4(pcp)(C3F7CO2)4] x pyrene (1), [Ag4(pcp)(C3F7CO2)4] x phen (phen = phenanthrene) (2), and [Ag4(pcp)(C3F7CO2)4] x fluorene (3), and an intercalation compound [Ag4(pcp)(C3F7CO2)4] x 2benzene (4). All the four complexes exhibit two-dimensional (2D) sheet structures in which AgC3F7CO2 form an infinite chain and pcp acts as linkage. 1, 2, and 3 show 2D flat sheets with cavities in which guest molecules are situated, whereas 4 exhibits 2D zigzag layers between which guest benzene molecules are intercalated. Pcp shows mu-di-eta1-eta2 coordination mode in 1, mu-tetra-eta1 coordination mode in 2 and 3, and mu-tetra-eta2 coordination mode in 4. The reversible guest exchanges were observed between complex 1, 2, or 3 and intercalation compound 4. It is unprecedented for metal-organic inclusion complexes that the guest exchange occurs where the guest is the solute molecule. Furthermore, 4 can release the guest, and the original framework was completely recovered after reincorporation of benzene. It should be noted that 4 can incorporate pyrene, phen, and fluorene to give 1, 2, and 3, respectively, after desorption.     

Two-Dimensional Near-Field Optical Spectroscopy in Magnetic Fields up to 4 T

We have developed a magnetic-field-type scanning near-field optical microscopy (SNOM) system, which enables us to obtain two-dimensional near-field images under magnetic fields up to 4 T. We have performed two-dimensional near-field scanning optical spectroscopy on (Cd,Mn) Te self-assembled quantum dots with this system.     

Dynamic three-point bending tester using inertial mass and optical interferometer

A method for generating and measuring varying force by means of levitating a rigid object is discussed in this paper. The inertial force is accurately measured using an optical interferometer and an electric frequency counter. The performance of the three-point bending tester based on the proposed idea is investigated. The 12 sets of three-point bending tests have been conducted against aluminum bars. The combined standard uncertainty in measuring the instantaneous value of the reaction force, with the sampling interval of approximately 1–2 ms, is approximately 0.11 N. This corresponds to approximately 3×10⁻³ (0.3%) of the maximum inertial force in the experiments.     

On detonation behavior of mixed fuels

An experimental study of detonation was carried out for mixed fuels (, and ). The results obtained demonstrate that detonation velocities of mixed fuels agree very well with normal C-J velocity and that detonation limits were not extended by the addition of a small amount of . As for mixed fuel, detonation velocities and detonation limits as a function of the equivalence ratio of the whole mixture of mixed fuel coincided with those of single fuel. However, the detonation induction time of a mixture of with a lower sensitivity to detonation decreased considerably with the addition of a small amount of . In addition, the influence of mixed fuels on the quasi-detonation and the fast deflagration in the process of DDT was investigated, showing interesting and complicated features in mixed fuel. Received 20 December 1994 / Accepted 20 November 1995     

A practical synthesis of (-)-kainic acid

A highly practical stereoselective total synthesis of (-)-kainic acid is described. This synthesis features the stereoselective alkylation of an iodolactone intermediate that was efficiently prepared from (+)-carvone and introduction of carboxylic acid by hydrolysis of a nitrile accompanied by epimerizaion. This synthetic route enabled us to obtain 14.6 g of (-)-kainic acid.     

New imidazopyridopyrimidine:naphthyridine base-pairing motif, ImN(N):NaO(O), consisting of a DAAD:ADDA hydrogen bonding pattern, markedly stabilize DNA duplexes

The new imidazopyridopyrimidine:naphthyridine base-pairing motifs, ImO(O):NaN(N) and ImN(N):NaO(O), were designed. Among the base pairs examined, DNA duplexes containing ImN(N):NaO(O) pair(s) consisting of a DAAD:ADDA hydrogen bonding pattern (D = donor, A = acceptor) were markedly stabilized thermally and thermodynamically.