Tuning of spin density wave strengths in quasi-one-dimensional mixed-halogen-bridged nickel(III) complexes with strong electron correlation, [Ni(III)(chxn)(2)Cl(1-x)Br(x)](NO(3))(2)

This communication describes the syntheses of the quasi-one-dimensional mixed-halogen-bridged Ni(III) complexes with strong electron correlation [Ni(chxn)(2)Cl(1-x)Br(x)](NO(3))(2) and the tuning of the spin density wave strengths of these compounds. If the Cl 3p and Br 4p make one band in the compounds, we should observe a single peak in the electronic spectra. As a result, we should observe the single peak from 1.45 to 2.00 eV depending on the mixing ratios of Cl and Br ions. Therefore, the Cl 3p and Br 4p make one band. Then, we have succeeded in tuning the spin density wave strengths of the Ni(III) complexes with the strong electron correlation by mixing the bridging halogen ions successively.     

Site-specific discrimination of Cytosine and 5-methylcytosine in duplex DNA by Peptide nucleic acids

For site-specific discrimination of cytosine (C) and 5-methylcytosine (mC) in duplex DNA, we developed a new method using peptide nucleic acids (PNAs). The combination of a PNA-assisted DNA displacement complex and a fluorescein-labeled probe oligomer allowed the detection of mC at the defined sites in target DNA using a restriction enzyme. After treatment of the complex with a restriction enzyme, strong fluorescence emission was observed for the complex containing C at the target site, whereas the fluorescence intensity for the complex containing mC was extremely weak.     

Microwave-assisted simple ion-exchange of ZSM-5-type zeolites with copper ions and their specific adsorption properties for N2 molecules at room temperature

Copper ion-exchanged ZSM-5 samples, prepared using an easy method that takes advantage of microwaves, exhibit a quite peculiar adsorption feature for dinitrogen molecules, in that a large volume of chemisorbed N2 was detected, even at room temperature, and the specificity of the adsorption properties was clarified by comparing with the properties of samples prepared by an ordinary ion-exchange method.     

Inhibition of restriction enzyme's DNA sequence recognition by PUVA treatment

Applying various restriction enzymes on a specially designed 1.5 kb DNA fragment revealed that the inhibitory effects of psoralens + UVA irradiation (PUVA) treatment on restriction endonuclease activities are caused by recognition inhibition. In this study restriction enzymes that have a 5'-TpA sequence at the cleaving site (KpnI, XbaI, PmeI and DraI), and the noncleaving site (PacI) in recognition sites, or have two 5'-TpA sequences at the recognition site, and a nonspecific sequence between the recognition and the cleaving sites (BciVI), were inhibited by PUVA treatment. Most of the other restriction enzymes used in this study, which do not have a 5'-TpA sequence at their restriction site, were not inhibited by PUVA treatment, although a 5'-TpA sequence is located adjacent (SmaI) or very close (BamHI, SacI and PstI) to the recognition and cleaving sites for these enzymes. Because SphI, which does not have 5'-TpA at its restriction site, was strongly inhibited by PUVA treatment, the 5'-CpA sequence is suggested to be a new binding site of psoralens after UVA irradiation.     

Deoligomerization of siloxanes with dimethyl carbonate over solid-base catalysts

Hexamethyldisiloxane and hexamethylcyclotrisiloxane were almost completely deoligomerized with dimethyl carbonate over alumina-supported potassium fluoride catalyst to form methoxytrimethylsilane (85% yield) and dimethoxydimethylsilane (94% yield), respectively, and moreover the addition of a small amount of methanol to the hexamethyldisiloxane deoligomerization reaction enhanced the methoxytrimethylsilane yield to 98%.     

Specific Alkylation of Guanine Opposite to a Single Nucleotide Bulge: A Chemical Probe for the Bulged Structure of DNA

Remarkable enhancement of guanine alkylation just opposite a bulged site by 13R-1 compared with those in normal duplex DNA is ascribable to the formation of a unique intercalated complex that is attainable only at the bulged sites (see picture). This observation suggests that 13R-1 can be used as a chemical probe for the bulged structure of DNA.     

Heat capacities of Laves phase compounds RMn2 (R = Y, Gd and Er)

Measurements of heat capacity indicate that the Mn moment in YMn₂ has an itinerant character and an additional C_M is observable even above T_N. In GdMn₂, the Gd moments are in disorder at T_N simultaneously with the Mn moments. The CEF contributions in ErMn₂ are observed and are calculated using a single-ion Hamiltonian.     

Synthesis and copolymerizations of 3,3-difluorocyclobutene-1-carbonitrile

3,3-Difluorocyclobutene-1-carbonitrile (DFCB) was synthesized via cycloaddition of 1-chloro-2,2-difluoroethylene and acrylonitrile, followed by dehydrochlorination with 1,4-diazabicyclo[2.2.2]octane in tetrahydrofuran. Unlike cyclobutene-1-carbonitrile, this monomer did not homopolymerize either under radical or anionic conditions. As an electron-poor monomer it copolymerized in the presence of free radicals with electronrich monomers such as styrene in good yield. It also copolymerized with electron-poor monomers such as acrylonitrile, although in lower yields. The extent of incorporation of DFCB in the copolymers also depended on the electronic characteristics of the comonomers: high incorporation occurred with electron-rich monomers, low incorporation with electron-poor monomers. One extremely electron-poor monomer, trimethyl ethylenetricarboxylate, did not copolymerize with DFCB.     

A new electrochemical system for stereoselective allylic hydroxylation of cholesteryl acetate with dioxygen induced by iron picolinate complexes

The oxygenation reaction of cholesteryl acetate 1 was examined with the Fe(III)(PA)(3)/O(2)/MeCN system using an electrochemical method. The constant potential technique gave mainly the 7-hydroxylated product stereoselectively, along with the 7-oxo product. This oxygenation system is mechanistically unique, requiring iron catalyst, dioxygen, and both cathode and anode.