Ferromagnetic anomaly associated with the antiferromagnetic transitions in (donor)[Ni(mnt)2]-type charge-transfer salts

Three newly prepared [Ni(mnt)2] complexes, (HMTTF)[Ni(mnt)2], (ChSTF)[Ni(mnt)2], and (DBTTF)2[Ni(mnt)2], are reported (DBTTF = dibenzotetrathiafulvalene, ChSTF = 2,3-cyclohexylenedithio-1,4-dithia-5,8-diselanafulvalene, HMTTF = bis(trimethylene)-tetrathiafulvalene, and mnt = maleonitrile dithiolate). The former two compounds have usual DA-type (D = donor, A = acceptor) mixed stacks, whereas the DBTTF complex has DDDDAA-type 6-fold columns. These compounds are electrical insulators, but the HMTTF and ChSTF complexes exhibit chiT minima at 16 and 55 K, respectively, followed by chiT peaks at 8 and 16 K. Below these temperatures the ESR signal disappears, indicating antiferromagnetic transitions. The origin of the ferromagnetic interaction is explained either from the difference of the g values between the donor and the anion or from the intrinsic ferromagnetic interaction of the [Ni(mnt)2] anions.     

A catalytic immuno-reactor for the amperometric determination of human serum albumin

A catalytic immuno-reactor for the determination of human serum albumin (HSA) was constructed by using immobilized antibody and an amperometric detector. A sandwich assay with hemin-labeled antibody to catalyze the decomposition of hydrogen peroxide was used, the catalytic activity of the hemin-antibody conjugate being determined by measuring the decrease in hydrogen peroxide concentration. The reaction of hemin-labeled antibody with antigen was complete within 30 min and the current decrease was correlated with the HSA concentration. The relative standard deviation was about 9% at an HSA concentration of 1 mg ml^?1.     

Asymmetric synthesis of dipeptides by means of homogeneous hydrogenation catalyzed by chiral rhodium complexes

Asymmetric hydrogenation of dehydrodipeptides, α-acylaminocinnamoyl-(S)-amino esters, catalyzed by rhodium complexes with chiral diphosphines gave either (R)-N-acylphenylalanyl-(S)-amino esters or (S)-N-acylphenylalanyl-(S)-amino esters with high diastereomeric purity up to 98–99% on using proper chiral ligands.     

Signals for scalar top quark atep collider HERA

In the framework of the minimal supersymmetric standard model (MSSM) and theR-parity breaking model (RBM), we investigate production processes of the scalar top (stop) at HERA energies. These models are characterized by the possible existence of the light stop whose mass is lighter than those of the top quark and the other squarks. It is shown that in the MSSM the stop pair production via boson-gluon fusion gives a sizeable cross section and the most serious background $ep \to ec\bar cX$ could be suppressed by appropriate kinematical cuts. We also show that in the RBM the stop is singly produced in the neutral current processes and we have a clear signal as a sharp peak in the Bjorken parameterx distribution of the scattered electron.     

The effect of humidity on thermal process of zinc acetate

The thermal decomposition of zinc acetate dihydrate Zn(CH₃CO₂)₂·2H₂O in some humidity-controlled atmospheres has been successfully investigated by novel thermal analyses, which are sample-controlled thermogravimetry (SCTG), thermogravimety combined with evolved gas analysis using mass spectrometry (TG–MS) and simultaneous measurement of differential scanning calorimetry and X-ray diffractometry (XRD–DSC). The thermal processes of anhydrous zinc acetate in dry gas atmosphere by conventional linear heating experiment initiated with the sublimation around 180 °C, followed by the fusion and the decomposition over 250 °C. SCTG was useful to interpret clearly the successive reaction because the high-temperature parallel decompositions were effectively inhibited. The thermal behavior changed dramatically by introducing water vapor in the atmosphere and the thermal process was quite different from that in dry gas atmosphere. Zinc oxide (ZnO) was formed only in a humidity-controlled atmosphere, and could be easily synthesized at temperatures below 300 °C. XRD–DSC equipped with a humidity generator revealed directly the crystalline change from Zn(CH₃CO₂)₂ to ZnO. A detailed thermal process of Zn(CH₃CO₂)₂·2H₂O and the effect of water vapor are discussed.     

Novel [2 + 2] photocycloaddition-induced rearrangement of bichromophoric naphthalene-tethered resorcinol ethers

The first examples of sequential photocycloaddition-rearrangement reactions of naphthalene-tethered resorcinol ethers are described. Bichromophoric aromatic compounds with naphthalene and resorcinol ether moieties were irradiated in the presence/absence of a small amount of acid to give the corresponding cycloaddition-rearrangement products. From the determination of quantum yields, steady-state fluorescence spectral studies, and fluorescence lifetime measurements, the mechanism of this novel photoinduced multistep reaction was elucidated to involve the initial intramolecular exciplex formation, followed by the intramolecular [2 + 2] photocycloaddition between the two aromatic rings and the subsequent acid-catalyzed skeletal rearrangement of the resulting cyclobutane derivative leading to the final products.     

New highly strained bridgehead imines, 2-azaadamant-1-ene and 4-azaprotoadamant-3-ene

An azaanalog of adamantene, 2-azaadamant-1-ene ($\text{1}$) and 4-azaprotoadamant-3-ene ($\text{7}$) were generated in the nonstatistical ratio via photolysis of 3-azidonoradamantane ($\text{2}$). The highly strained $\text{1}$ and $\text{7}$ could not be isolable but were trapped by MeOH. Acidolysis of $\text{2}$ was also reported, and discussed in comparison with the photolysis.     

Surface-enhanced Raman scattering from crystal violet adsorbed on a silver electrode

SERS from crystal violet (CV) on a Ag electrode was investigated under preresonance and resonance conditions. The excitation profile of the chemisorbed species is like that of dissolved molecules but intensities are ≈ 1000 times larger. The Raman enhancement is ≈ 10⁸ and exhibits a specific potential dependence even in the absence of adsorption-desorption process. At potentials where reduction of CV occurs leuco crystal violet was detected.     

Novel ring transformation reactions of xanthine derivatives

The novel ring transformation reactions were found in the reactions of 1,3,7,9-tetra-alkyl-8,9-dihydroxanthines and acetylenic compounds. The reaction of the dihydroxanthine with DMAD gave a propellane type compound and with methyl propiolate afforded the similar type compound and a pyrimido[4,5-b]diazepine derivative. The mechanism of these reactions was also discussed.     

Cyclic dithio-carbenium ion salts and their conversion to ketene dithioacetals

1,2-Ethanedithiol and 1,3-propanedithiol were treated with perchloric acid in acetic anhydride to give 2-methyl-1,3-dithiolan-2-yl and 2-methyl-1,3-dithian-2-yl perchlorates, respectively, which were converted to ketene dithioacetals by deprotonation with tertiary amines.