The dependence of photoluminescence (PL) and photoluminescence itation (PLE) on preparation condi-tions and the aging of porous silicon carbide (PSC) have been investigatted. The fiber size of the material pre-pared under dark-current mode, labele d DCM, was larger than that of the photoassisted (PA)process.The intensity of the PL spectrum for the PA condition was higher than that of the DCM condition. The PA condition giving small fiber size exhibited amore prominent high-energy component but the emission bands of both con-ditionsobserved were rather similar. The origin of the PL may have played an importantrole in the surface defect center introduced by the reaction conditions ofHFatthe surface of the silicon carbide. Selective excita-tion of the PL bandsusingdifferent excitation wavelengths has been used to identify distinct componentswith-in the PL bandwidth. Two main PL bands with peak wavelength of494 and534 nm were clearly resolved. On the other hand, selectivc emission of the PLEbands using different emission wavelengths has been used to identify distinct components within the PLE bandwidth. The higher energy band with peak wavelength of 338 nm and the lower energy bands involving 390,451 and 500 nm were clearly resolved. According to the pro-ionged aging in air, PL spectra appearedasone band, This emission probably originated from states localized to the band-to-band recombination due to the oxidation on the crystallite surface.

A convenient total synthesis of a new 7-deoxyidarubicinone ivative21,the aglycon of the anticancer anti-biotic idarubicin analogue,is described.Keyfeatures of the synthesis are the Friedel-Crafts acylation and the functionalization of an A-ring si de chain. A synthon 14 for the A and B rings was prepared from intermediate 6 in five steps.

Comparing the adsorption properties and dissociation on a Pt(111) iththat ona Fe(111) surface, we have con-sidered seven coordination modes of the adsorbed binding site: $di-${\sigma}$${\Delta}$\mu\pi/\mu$, 1-fbld,2-fold, and 3-fbld sites. On the Pt(111) surface, t he adsorbed binding site of carbon dioxide was strongestat the1-fold site and weakest at the $\pi/\mu-site.$ The adsorbed binding site on the Fe(111) surface was strongest at the di-бsite and weakest at the 3-fold site. We have found that the binding energy at each site that excepted 3-fold on the Fe(111) surface was stronger than the binding energy on the Pt(111) surface and that chemisorbed $CO_2bends$ because of metal mixing with $2\piu${\rightarrow}$6a_1CO_2orbital.$, The dissociation reaction occured in two steps, with an intermediate com-plex composed of atomic oxygen and ${\pi}bonding$ CO forming. The OCO angles of reaction intermediate com-plex structure for the dissociation reaction $were115^{\circ}Con$ the Pt(111), and $117^{\circ}C$ on the Fe(111) surface. We have found that the $CO_2dissociation$ rea11) surface proceeds easily,with an activationenergy about 0.2 eV lower than that on the Pt(111) surface.

Mass spectral fragmentations of six chlorinated organophosphorus pesticides were investigated using electron impact mass spectrometry. Understanding the fragmentation pathways, based on the fragment ions of mass spectra, should be useful in the structural elucidation and chemical identification of these compounds. The pro-posed fragmentation pathways were verified by collision-induced dissociation B/E-linked scan spectra. ln most cases,the structures of characteristic fragment ions could be expected by the observation of the peak clusters due to 35Cl and 37Cl isotopes. According to substituted groups on phosphorus atom, phosphate and phospho-rothioate exhibited significantIy differentfragmentation patterns. Especially, phosphate and phosphorothioate with diethyl ester produced more diverse fragment ions than that with dimethyl ester.

In the neat flow vacuum pyrolysis of 2-methoxy-2-(o-N,N+dimethylaminomethyl)phenyl-3-trimethylsilyl-5,5-dime-thyl-2-silahexane (4) at $600^{\circ}C$ and its static thermolysis at $350^{\circ}C23-benzo-5-aza-1-silacyclohexane$, (5) has been obtained in97% and 46％ y ields, respectively. Product 5 might have been formed via an intramolecular rearrangement invoIving a zwitterionic species generated from the pentacoordinated silene Si-atom. From trapping experiments with an excess of MeOH, we have obtained 2-(o-N,N-dimethylaminomethyl)phenyl-5,5-dimethyl-2-trimethylsiloxy-2-silahexane (6) and 2-(o-N,N-dimethylaminomethyl)phenyl-2-methoxy-5,5-dime-thyl-2-silahexane (7) formed via an intermolecular protodesilylation reaction rather than through trapped prod-ucts of the silene.

The reaction of o-acylthiophenacyl chloride 5a with onc equivalent ofsodium azide in aqueous acetone at-10~ $-5^{\circ}C$ gave 2,9-dimethyl-6H,I3H-dibenzo[d,i][1,6]dithiecin-7,14-dione 7(10%),acyclic dimer 8(64%),and tri-mer 9 (8%). Dimer 8 and trimer 9 we re converted readily to 7 under the similar conditions at room temperature in yields of 72% and 53%,respectivel. Also, one pot synthesis of 7 (64%, 45%) from the reaction of 5a or 5b with two equivalents of sodium azide at room temperature was very successful.

A crossed beam scattering of a $Pb(ZrxTi1-x)O_3plume$ and an oxygen jetwas studied by using a time-of-flight quadrupole mass spectroscopy. Both simple collisions and reactive scatterings had significant effects on the transportand energetics of ions in the plume. Relative enrichment of metal and metal oxide ions was also changed with the oxygen pulse because of the differences in the mass and chemical properties of the ions. In particular, an anomalous increase ofPb+ ions was observed as the oxygen jet crossed the plume at high laserfluences, while the signal magnitudes of alI other ions were reduced. This originates from the fact that PbO+ ions dissociate easily to liberate Pb+ ions inthe plume since the bond energy of PbO+ is as low as 2.2 eV.

Mixed crystal powders based on Cd,Fe, and S have been synthesized by varying the ratio of CdS and $FeS_2in$ order to find a suitable material usefuI for the effectivc conversion of solar energy. Hydrogen gas was evolved only with CdS/Ptby photocatal ytic reaction under white light in an aqueous 1 M sodiumsulfite solution. From electrochemical studies of semiconductor electrodes. itwas shown that the onset potential shifted to the positive direction and that the bandgap energy also decreased as the molar ratio of Fe increased. A hydrogen evolution mechanism in terms of the conduction band potential and hydrogen evolution potential is proposed.

Treatment of the aromatic compounds with benzyl halides in the presence of a catalytic amount of indunm gave the corresponding diarylmethane products in good to excellent yields.

The synthesis of bisphenol A-derived calixarenes has been studied by changing the protecting group of the phe-nol moiety and reaction conditions. Depending on the protecting groups,the corresponding calix[6,7,8]arenes are obtained in different rat ios. For example, whcn mono-p-tert-butyldimethylsilyl-protected bisphenol A is treated with paraformaldehyde and a catalytic amount ofaqueous KOH in refluxing p-xylene with a Dean-Stark water collector for 36 h, the corresponding calix[8]arene, calix[7]arene, and calix[6]arene are producedand separated in the ratio of about 3 : 2 : l and with overall 63% yield. The calixarenes are characterized by NMR spectroscopy and mass analysis. The X-raycrystal structure of the calix[8]arene shows a pleated loop confor-mation, stabilized by intramoIecular hydrogen bonding between the inner phenolic hydroxy groups.

Crack-free hard coating siIica films were prepared by sol-gel processfrom twokinds of silicon alkoxide (tetra-ethoxysilane and methyltrimethoxysilane) and two kinds of alcohol (methanol and isopropyl alcohol) with an acid catalyst,acetic acid. A silicate framework of the precursor solution was investigated by infrared spectros-copy (IR) in the process of hydrolysis and condensation. Theextent of the condensation in the intermediates was elucidated by gel permeation chromatography (GPC) and 29Si-NMR spectroscopy. The hard coating films werecharacterized by IR,scanning electron microscope (SEM), thermo gravimetric analyzer (TGA) and dif-ferential scanning calroimeter (DSC). The synthetic condition for the crack-free and transparent silica film for-mation was optimized interms of starting materials for the precursor solution as well as preparation method of the silica film.

Gas-Phase reactions of methyl and ethyl nitrites with anionic nucleophiles of SH-, F- and OH- are investigated theoretically at the MP2/6-311+G* level. The SN2 processes are all highly exothermic and proceed with a typ-icaI double-weIl reaction coordinate profile. The elimination reactions of methyl nitrite with SH- and F- are double-well energy surface processes,with stabilizedproduct complexes of NO-...H2S and NO-...HF, pro-ceeding by an E1 cb-like E2 mechanism. The $\beta-elimination$ of ethyl nitrite is an E2 type process. The $\alpha-elimi-nation$ reactions of methyl and ethyl nitrites with OH- have triple-well energy profiles of Elcb pathway with an $\alpha-carbanion$ intermediate which is stabilized bythe vicinal $nc\alpha-{\sigma}*o-N$ charge transfer interactions. CompIex-ation ofmethyl carbanion with HF seems to provide a stable intermediate within a triple-well energy profile of El cb channel in the reaction of F- with methyl nitrite.