Synthesis of new photochromic compounds from the dimer of arylphenanthroimidazoles

Treatment of the dimer of 2-arylphenanthro[9,10-d]imidazoles with nucleophilic compounds such as alcohols, aliphatic amines, and carboxylic acids afforded 2-substituted-2H- and 4-substituted-4H-2-arylphenanthro[9,10-d]isoimidazoles. These products showed a characteristic photochromism by dissociation to a stable imidazolyl radical.     

Antioxidants from rape (Brassica campestris vir. Japonica Hara) oil cake

A simple but novel compound, S-1-methoxy-1-(3,5-dimethoxy-4-hydroxyphenyl)ethane, was isolated as a moderately antioxidative compound from rape (Brassica campestris L. subsp. napus) oil cake together with 5 known compounds. Three of these compounds, indolacetonitrile, 4-hydroxyindolacetonitrile, and 4-hydroxyphenylacetonitrile, showed strong antioxidative activity evaluated by the ferric thiocyanate method.     

Synthesis of nitrogen-containing heterocycles. 5. A new route to 5-amino-[1,2,4]triazolo[1,5-a][1,3,5]triazine derivatives

Treatment of certain diaminomethylenehydrazones 1 of aromatic carbonyl compounds with ethyl N-cyanoimidate ( 2 ) in acetonitrile in the presence of a tertiary amine at room temperature gives the corresponding amino(N-cyanoiminomethyl)aminomethylenehydrazones 3 in high yields. The intermediate 3 can readily be cyclized to the corresponding 5-amino-2,3-dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazines 4 in moderate to good yields by brief heating in acetonitrile. When the reaction of diaminomethylenehydrazones 1 with ethyl N-cyanoimidate ( 2 ) is performed at reflux temperature in the presence of a tertiary amine, 5-amino-2,3-dihydro[1,2,4]triazolo[1,5-a]1,3,5]triazines 4 can be directly obtained in moderate yields. The yields of triazolotriazine produced by the one-step synthesis are generally comparable or even higher than the overall yields from the two-step procedure.     

Dichloro­(4,4′‐dialkyl‐2,2′‐bipyridine‐κ2N,N′)platinum(II), where alkyl is pentyl and heptyl

Dichloro­(4,4′‐dipentyl‐2,2′‐bipyridine‐κ²N,N′)platinum(II), [PtCl₂(C₂₀H₂₈N₂)], adopts a discrete π–π stacking structure, where the alkyl chains are located in a random manner. In contrast, dichloro­(4,4′‐diheptyl‐2,2′‐bipyridine‐κ²N,N′)platinum(II), [PtCl₂(C₂₄H₃₆N₂)], forms a layer structure comprised of alkyl chain layers and paired coordination sites, as observed for analogous complexes with longer alkyl chains.     

Crystal Structure of Zinc(II) Complexes with 2-Ethyl-3-hydroxy-4H-pyran-4-thione and 2-Ethyl-3-hydroxy-4H-pyran-4-selenone

Crystallography Reports - Zn(II) complexes with 2-ethyl-3-hydroxy-4H-pyran-4-thione, [Zn(ehpt)2], and 2-ethyl-3-hydroxy-4H-pyran-4-selenone, [Zn(ehps)2], were synthesized and characterized by...     

Facile synthesis of urea derivatives under mild conditions

Urea derivatives were readily synthesized in good yields under quite mild conditions, i.e., at ambient pressure and room temperature by sulfur-assisted carbonylation of primary amines with carbon monoxide followed by oxidation of the resulting ammonium thiocarbamates with molecular oxygen.     

Preparation and functions of self‐assembled monolayers of helix peptides

Self‐assembled monolayers (SAMs) of helix peptides oriented vertically to a gold surface were prepared. Negative surface potentials of a few hundred millivolts were observed for the helix peptide SAMs when they were immobilized on gold through the N terminal of the peptides. However, positive surface potentials were generated in the helix peptide SAMs when the N terminal of the peptides was directed the opposite way. The large dipole moment of the helical peptide was thought to be the major factor for generation of the surface potential. The effect of the dipole moment on the electron transfer through the helix peptide SAMs was investigated. Photocurrent generation by photoexcitation of the N‐ethylcarbazolyl group of the peptide SAMs was accelerated by the dipole moment directed toward the gold substrate. Helical peptides were thus shown to be a suitable medium for electron transfer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4826–4831, 2000     

Selection of modulation frequency of FT-IR equipped with an MCT detector for thin-film analysis

Optimal modulation frequency (scan rate) of an FT-IR equipped with a mercury–cadmium–telluride (MCT) detector has been investigated for obtaining high quality spectra of a monolayer-level thin film. Since an MCT detector is a semiconductor light device, it does not respond to modulation frequency significantly in comparison to a pyroelectric detector. A very thin film, however, requires high-throughput measurements to have high signal-to-noise ratio. In this study, a balance of throughput and measurement time has been investigated by varying modulation frequency by using two spectrometers that have different sampling frequencies. In this study, the stability of the baseline of absorbance spectra was also investigated depending on modulation frequencies, which suggested that 60 kHz was most suitable for quantitatively reliable transmission measurements of Langmuir–Blodgett films.     

Note on a min‐max conjecture of Woodall

In 1978 Woodall [ 6 ] conjectured the following: in a planar digraph the size of a shortest cycle is equal to the maximum cardinality of a collection of disjoint tranversals of cycles. We prove that this conjecture is true when the digraph is series‐parallel. In fact, we prove a stronger weighted version that gives the latter result as a corollary. © 2001 John Wiley & Sons, Inc. J Graph Theory 38: 36–41, 2001     

Packing triangles in low degree graphs and indifference graphs

We consider the problems of finding the maximum number of vertex-disjoint triangles (VTP) and edge-disjoint triangles (ETP) in a simple graph. Both problems are NP-hard. The algorithm with the best approximation ratio known so far for these problems has ratio 3/2+?, a result that follows from a more general algorithm for set packing obtained by Hurkens and Schrijver [On the size of systems of sets every t of which have an SDR, with an application to the worst-case ratio of heuristics for packing problems, SIAM J. Discrete Math. 2(1) (1989) 68-72]. We present improvements on the approximation ratio for restricted cases of VTP and ETP that are known to be APX-hard: we give an approximation algorithm for VTP on graphs with maximum degree 4 with ratio slightly less than 1.2, and for ETP on graphs with maximum degree 5 with ratio 4/3. We also present an exact linear-time algorithm for VTP on the class of indifference graphs.