A silane dendrimer with 48 allylic end groups has been synthesized in excellent yield, via repetitive alkenylation-hydrosilation cycles. Starting with hexaallylethylenedisilane ((CH2=CHCH2)3SiCH2)2 as the core molecule (G0), a succession of alternate platinum catalyzed hydrosilation (Pt/C, 10% platinum content on active carbon) of all allyl groups with methyldichlorosilane and the allylation of all SiCl2 groups with allylmagnesium bromide in THF provided 3rd generation (G3) as carbosilane dendrimer. All the generations of dendrimer have been characterized by 1H and 13C NMR spectroscopy as well as elemental analysis.

1,3-Dipolar cyclization of various nitrile oxides with 3(2H)- and 2(5H)-furanones regioselectively furnished the corresponding syn-addition products of 3-oxotetrahydro-furano[4,5-d]isoxazolines and 2-oxotetrahydrofurano[3,4-d]isoxazolines.

The synthesis is reported of p-nitrophenyl glycosides of D-galactose modified at C-4 with azido- (5), amino- (6) group and fluorine (13). 4-Azido-2,3,6-tri-O-benzoyl-4-deoxy-α-D-galactopyranosyl chloride and 2,3,6-tri-O-benzoyl-4-deoxy-4-fluoro-α-D-galactopyranosyl bromide were coupled with potassium p-nitrophenoxide in the presence of 18-crown-6 giving the corresponding p-nitrophenyl 4-azido-and 4-fluoro-4-deoxy-β-D-galactopyranoside derivatives. p-Nitrophenyl 4-amino-4-deoxy-β-D-galactopyranoside (6) was obtained by selective reduction of p-nitrophenyl 4-azido-4-deoxy-β-D-galactopyranoside (5) using 1,3-propane dithioltriethylamine. These galactoside analogs were slowly hydrolyzed in the increasing rate order of 5, 6 and 13 by β-galactosidase from Escherichia coli.

Semiempirical PM3 MO calculations are applied to estimate both 1-atom (X=S,O,C) and 3-substituent (Y=R, CH2R, SR, CH2SR) effects on the reactions of some 1-atom-replaced and 3-substituted cephem-like β-lactam compounds of thiacephems, oxacephems, and carbacephems. Stabilization energy (SE) of the reaction intermediate for the reaction with a hydroxyl ion can be used to evaluate the facility of a reaction and selected as a chemical reactivity index. With the 1-atom effect only, the SE values obtained imply that thiacephems are generally more reactive than the other two cephem-like molecules and the reactivity order is thiacephems>oxacephems>carbacephems. When it comes to the 3-substituent (Y=R, CH2R, SR, CH2SR) effect, chemical reactivity can be best realized by using a 3-substituted thiacephem molecule capable of giving a resonance-stabilized and electron-rich leaving group after the reaction with a nucleophile. SE values, however, decrease in most cases when an additional intervening ethylene group is present (Y=CH2R, CH2SR). The overall 3-substituent reactivity tendency is SR>CH2SR>R>CH2R.

A series of new NLO-active poly(4-nitrophenylallylamine) derivatives was synthesized by the nucleophilic substitution reaction of several substituted 4-nitrohalobenzenes and poly(allylamine hydrochloride). All polymers obtained were amorphous and their glass transition temperatures (Tg) were observed around 148-160 ℃. For each of these polymers, their specific Tg values were dependent on characteristic electronic structures. UV-visible absorption spectra showed maximum absorption intensity at 355-393 nm for π-π* transition of alkylaminonitrophenyl groups. The χ(2)value of poly(4-nitrophenylallylamine), as determined by the second harmonic generation at 1064 nm, for a thin polymer film poled at an elevated temperature, was 1.4x10-8esu. The third-order NLO properties of poly(4-nitrophenylallylamine) derivatives were evaluated through measurement of degenerate four-wave mixing technique and χ(3) coefficient in the range of 2.7~3.2x10-12 esu at 602 nm was found with 400 fs laser pulses.

The new 1,2-dithiolene, 1,4-butanediyldithioethylene-1,2-dithiolate (BDDT2-), has been isolated. In addition, new monoanionic bis-complexes with nickel and copper have been prepared and characterized. In order to investigate the detailed electronic structure of the metal complexes of the new ligand, BDDT2-, in terms of the oxidation state of the central metal ions, we have carried out molecular orbital (MO) calculations of Ni(BDDT)2-and Cu(BDDT)2- utilizing an Extended Huckel method. Cyclic voltammetry data for both complexes were obtained with a potentiostat. We have also compared these results to the previously synthesized Ni(PDDT)2-, Ni(DDDT)2-,Cu(PDDT)2-, and Cu(DDDT)2-.

The transfer of excitation energy from solvent to solute in polystyrene films doped with 2-(2'-hydroxyphenyl)benzothiazole (HBT) which undergoes intramolecular proton transfer in excited electronic state has been studied by employing steady state and time-resolved fluorescence measurements. The degree of Forster overlap between donor and acceptor molecule in this system is estimated to be moderate. Energy transfer efficiency increases with solute concentration at low concentration range and levels off at high concentration. It is observed that the excimer form of polystyrene is largely involved in energy transfer process. Photostability of HBT in polystyrene to UV light is also investigated to get insight into the long wavelength absorption band of HBT which was observed upon electron radiation.

A variety of metal oxides were coated by sol-gel process from their metal alkoxides on the ribbons of Co-based and Fe-based amorphous alloys, and the effects of surface oxide coating on the magnetic properties of the alloy are investigated. The core loss is found to be reduced significantly by the oxide coating, the loss reduction becoming more prominent at higher frequencies. The shape of the hystersis loop is also dependent upon the kind of the coated metal oxide. The coatings of MgO, SiO2, MgO·SiO2 and MgO·Al2O3 induce tensile stress into the Fe-based ribbon whereas those of BaO, Al2O3, CaO·Al2O3, SrO·Al2O3 and BaO·Al2O3 induce compressive stress. These results may be explained by the modification of domain structures via magnetoelastic interactions with the shrinkage stress induced by the sol-gel coating.

The cobalt-substituted polyoxotungstate [(CoPW11O39)5-] has been used as a catalyst in olefin epoxidation and alkane hydroxylation reactions. The epoxidation of olefins by iodosylbenzene in CH3CN yielded epoxides predominantly with trace amounts of allylic oxidation products. cis-Stilbene was streoselectively oxidized to cis-stilbene oxide with small amounts of trans-stilbene oxide and benzaldehyde formation. The epoxidation of carbamazepine (CBZ) by potassium monopersulfate in aqueous solution gave the corresponding CBZ 10,11-oxide product. Other transition metal-substituted polyoxotungstates (M=Mn2+, Fe2+, Ni2+, and Cu2+) were inactive in the CBZ epoxidation reaction. The cobalt-substituted polyoxotungstate also catalyzed the oxidation of alkanes with m-chloroperbenzoic acid to give the corresponding alcohols and ketones. The presence of CH2Br2 in the hydroxylation of cyclohexane afforded the formation of bromocyclohexane, suggesting the participation of cyclohexyl radical. In the 18O-labeled water experiment, there was no incorporation of 18O into the cyclohexanol product when the hydroxylation of cyclohexane by MCPBA was carried out in the presence of H218O. Some mechanistic aspects are discussed as well.

The structures of fully dehydrated Ca2+- and Rb+-exchanged zeolite X, Ca31Rb30Si100Al92O384(Ca31Rb30-X; a=25.009(1) Å) and Ca28Rb36Si100Al92O384(Ca28Rb36-X; a=24.977(1) Å), have been determined by single-crystal X-ray diffraction methods in the cubic space group Fd&bar{3} at 21(1) ℃. Their structures were refined to the final error indices R1=0.048 and R2=0.041 with 236 reflections for Ca31Rb30-X, and R1=0.052 and R2=0.043 with 313 reflections for Ca28Rb36-X; I>3σ(I). In both structures, Ca2+ and Rb+ ions are located at six different crystallographic sites. In dehydrated Ca31Rb30-X, sixteen Ca2+ ions fill site I, at the centers of the double 6-rings (Ca-O=2.43(1) Å and O-Ca-O=93.3(3)°). Another fifteen Ca2+ ions occupy site II (Ca-O=2.29(1) Å, O-Ca-O=119.5(5)°) and fifteen Rb+ ions occupy site II opposite single six-rings in the supercage; each is 1.60 Å from the plane of three oxygens (Rb-O=2.77(1) Å and O-Rb-O=91.1(4)°). About two Rb+ ions are found at site II', 1.99 Å into sodalite cavity from their three-oxygen plane (Rb-O=2.99(1) Å and O-Rb-O=82.8(4)°). The remaining thirteen Rb+ ions are statistically distributed over site III, a 48-fold equipoint in the supercages on twofold axes (Rb-O=3.05(1) Å and Rb-O=3.38(1) Å). In dehydrated Ca28Rb36-X, sixteen Ca2+ ions fill site I (Ca-O=2.41(1) Å and O-Ca-O=93.6(3)°) and twelve Ca2+ ions occupy site II (Ca-O=2.31(1) Å, O-Ca-O=119.7(4)°). Sixteen Rb+ ions occupy site II; each is 1.60 Å from the plane of three oxygens (Rb-O=2.81(1) Å and O-Rb-O=90.6(3)°) and four Rb+ ions occupy site II'; each is 1.88 Å into sodalite cavity from their three-oxygen plane (Rb-O=2.99(1) Å and O-Rb-O=83.8(2)°). The remaining sixteen Rb+ ions are found at III site in the supercage (Rb-O=2.97(1) Å and Rb-O=3.39(1) Å). It appears that Ca2+ ions prefer sites I and II in that order, and that Rb+ ions occupy the remaining sites. Rb+ ions are too large to be stable at site I, when they are competing with other smaller cations like Ca2+ ions.

Preparation and properties of potential CVD (Chemical Vapor Deposition) precursors for the TiO2, a major component of the perovskite materials such as PT, PLT, PZT, and PLZT were investigated. Reactions between β-diketones and TiMe3, formed in situ failed to produce stable Ti(β-diketonate)3 complexes but a stable purple solid, characterized as (OTi(BPP)2)2 (BPP=1,3-biphenyl-1,3-propanedione) was obtained when BPP was used. Several new Ti(Oi-Pr)2(β-diketonate)2 complexes with aromatic or ring substituents were synthesized by the substitution reaction of Ti(OiPr)4by β-diketones and characterized with 1H NMR, IR, ICP, and TGA. Solid complexes such as Ti(Oi-Pr)2(BAC)2 (BAC=1.-phenyl-2,4-pentanedione), Ti(Oi-Pr)2(BPP)2, Ti(Oi-Pr)2(1-HAN)2 (1-HAN=2-hydroxy-1-acetonaphthone), Ti(Oi-Pr)2(2-HAN)2 (2-HAN=1-hydroxy-2-acetonaphthone), Ti(Oi-Pr)2(ACCP)2 (ACCP=2-acetylcyclopentanone), and Ti(Oi-Pr)2(HBP)2 (HBP=2-hydroxybenzophenone) were found to be stable toward moisture and air. Ti(Oi-Pr)2(ACCP)2 and Ti(Oi-Pr)2(HBP)2 were proved to have lower melting points and higher decomposition temperatures. However, these complexes are thermally stable and pyrolysis under an inert atmosphere resulted in incomplete decomposition. Ti(Oi-Pr)2(DPM)2 (DPM=dipivaloylmethane) and Ti(Oi-Pr)2(HFAA)2 (HFAA=hexafluoroacetylacetone) were sublimed substantially during the thermal decomposition. Pyrolysis mechanism of these complexes are dependent on type of β-diketone but removal of Oi-Pr ligands occurs before the decomposition of β-diketonate ligands.

1,2-Disubstituted chiral calix[4]arene "25-(3,5-dinitrobenzoyloxy)-26-methoxy-27,28-dihydroxycalix[4]arene" was synthesized by the reaction of 25-(3,5-dinitrobenzoyloxy)-calix[4]arene with methyl iodide in the presence of K2CO3. Methylation was occurred at the 26-position of calix[4]arene. The partial cone conformation and 1,2-substitution were characterized based on the 1H NMR, 13C NMR and X-ray diffraction analysis. The crystal structure has been determined by X-ray diffraction method. The crystals are orthorhombic, Pbca, a=10.652(1), b=17.687(1), c=32.247(3) Å, Z=8, V=6075.4(9) Å3, Dc=1.38gcm-3. The intensity data were collected on an Enraf-Nonius CAD-4 Diffractometer with a graphite monochromated Cu-Kα radiation. The structure was solved by direct method and refined by full-matrix least-squares methods to a final R value of 0.050 for 2368 observed reflections. The molecule is in the partial cone conformation. It has two strong intramolecular hydrogen bonds of O(1D)-H…O(1C)-H…O(1B).

We have shown several examples of characterization of multicomponent polymer systems by size exclusion chromatography coupled with a light scattering detector. Although SEC cannot provide a complete information for such systems due to its intrinsic limitation, one can extend its capability by combining multiple detection in order to get relevant information to some extent.

A comparative molecular field analysis (CoMFA) was carried out for the correlation of the transition state structures and the reaction rates for the SN2 reaction of 4-nitrophenyl benzoate and its sulfur analogs with anionic nucleophiles. The CoMFA analysis showed that both steric and electrostatic effects are important, and the steric contribution increased when nucleophiles are alkoxides or arylsulfides. In this study, we have demonstrated that the CoMFA analysis can be expanded beyond the scope of dealing with reactants and products. The reactant complex and transition state conformations generated along the reaction path can be more appropriately used for the correlation of structures and reaction rates.