Crystallographic Evidence for Direct Metal–Metal Bonding in a Stable Open‐Shell La2@Ih‐C80 Derivative

Endohedral metallofullerenes (EMFs) have novel structures and properties that are closely associated with the internal metallic species. Benzyl radical additions have been previously shown to form closed‐shell adducts by attaching an odd number of addends to open‐shell EMFs (such as Sc₃C₂@I_h‐C₈₀) whereas an even number of groups are added to closed‐shell EMFs (for example Sc₃N@I_h‐C₈₀). Herein we report that benzyl radical addition to the closed‐shell La₂@I_h‐C₈₀ forms a stable, open‐shell monoadduct instead of the anticipated closed‐shell bisadduct. Single‐crystal X‐ray diffraction results show the formation of a stable radical species. In this species, the La?La distance is comparable to the theoretical value of a La?La covalent bond and is shorter than reported values for other La₂@I_h‐C₈₀ derivatives, providing unambiguous evidence for the formation of direct La?La bond.     

Degradation of liposome cluster caused by the interaction with endocrine disrupting chemicals (EDCs)

The interaction between endocrine disrupting chemicals (EDCs) and liposome clusters was investigated using UV-vis spectroscopy and observed by microscope. Since liposome clusters are composed of small unilamellar liposomes and membrane proteins, they are regarded as a model of plasma membranes. The size of each cluster was 10microm in diameter. UV-vis spectroscopy of liposome clusters showed an apparent absorption at 300nm which was affected by the interaction with EDCs. Four EDCs caused an alteration in absorption in a concentration-dependence manner between 0.1 and 10ppm (i.e. 0.1-10mg/l). Microscopic observation showed that the effect was caused by the degradation of liposome clusters while degradation was induced by the interaction; liposome was broken down by EDCs. This report suggests that the liposome cluster can be applied for universal detection of EDCs based on the interaction between a plasma membrane model and EDCs.     

Neurite outgrowth-promoting active constituents of the Japanese cypress (Chamaecyparis obtusa)

In the screening of biologically active constituents from woody plants, the methanol extract of leaves of Chamaecyparis obtusa showed potent neurite outgrowth-promoting activity in neuronal PC12 cells. The ethyl acetate-soluble fraction of the methanol extract showed potent activity and was separated by means of various chromatographic methods to give the two new compounds 1 and 2, as well as 11 known lignan and sesquiterpene derivatives. The structures of the new compounds were determined to be 9-O-acetyldihydrosesamin (1) and 9-O-(11-hydroxyeudesman-4-yl)dihydrosesamin (2), respectively, in NMR studies including 2D-NMR experiments. Of the 13 compounds, the known compound hinokinin (5) and the new compound 2 showed potent neurite outgrowth-promoting activity in PC 12 cells.     

Triterpene glycosides from the roots of Codonopsis lanceolata

In the course of the development of new designer foods using the roots of Codonopsis lanceolata, we found that hot-water extracts of C. lanceolata recovered decreased testosterone levels in the blood and accelerated the restoration of reproductive dysfunction induced by hyperthermic treatment in male mice. Thus we studied the constituents of the polar fraction of the roots of C. lanceolata and identified six new triterpene saponins, lancemasides B (2), C (3), D (4), E (5), F (6), and G (7), along with the known saponin lancemasaide A (1) and phenylpropanoid glycosides 8-10. The structures of the new compounds 2-7 were determined by means of spectral data including 2D-NMR studies and chemical reactions to be oleanan-type bisdesmoside with sugars at C-3 and C-28. Compounds 2-6 have echinocystic acid as an aglycone, and compound 7 has asterogenic acid as an aglycone. Identification of the sugars and determination of their D,L-chiralities were carried out by application of the exciton chirality method to the per-O-p-bromobenzoylmethyl sugar derived from saponins.     

Beyerane derivatives and a sesquiterpene dimer from Japanese Cypress (Chamaecyparis obtusa)

In the course of studies on biological active constituents from woody plants, we previously reported the isolation of many lignan derivatives as neurite outgrowth-promoting compounds from an ethyl acetate soluble fraction of Japanese Cypress (Chamaecyparis obtusa). Further chemical investigation on the residual parts of the ethyl acetate soluble fraction of a methanol extract of Japanese Cypress resulted in the isolation of four new beyerene type derivatives and a novel sesquiterpene dimer formed between cryptomeridiol and hinokiic acid. Their structures were elucidated as 18-O-(Z)-p-coumaroylbeyer-15-ene-18-ol (1), 18-O-(E)-p-coumaroylbeyer-15-ene-18-ol (2), 18-O-(E)-p-coumaroylbeyer-15-ene-11beta,18-diol (3), 18-O-(Z)-p-coumaroylbeyer-15-ene-11beta,18-diol (4) and ent-cryptomeridiol-4-yl-hinokiiate (5) by (1)H-NMR, (13)C-NMR, 2D-NMR, and HR-MS spectral analysis.     

Electronic structure of six-coordinate iron(III) monoazaporphyrins

The electronic structures of six-coordinate iron(III) octaethylmonoazaporphyrins, [Fe(MAzP)L 2] (+/-) ( 1), have been examined by means of (1)H NMR and EPR spectroscopy to reveal the effect of meso-nitrogen in the porphyrin ring. The complexes carrying axial ligands with strong field strengths such as 1-MeIm, DMAP, CN (-), and (t)BuNC adopt the low-spin state with the (d xy ) (2)(d xz , d yz ) (3) ground state in a wide temperature range where the (1)H NMR and EPR spectra are taken. In contrast, the complexes with much weaker axial ligands, such as 4-CNPy and 3,5-Cl 2Py, exhibit the spin transition from the mainly S = 3/2 at 298 K to the S = 1/2 with the (d xy ) (2)(d xz , d yz ) (3) ground state at 4 K. Only the THF complex has maintained the S = 3/2 throughout the temperature range examined. Thus, the electronic structures of 1 resemble those of the corresponding iron(III) octaethylporphyrins, [Fe(OEP)L 2] (+/-) ( 2). A couple of differences have been observed, however, in the electronic structures of 1 and 2. One of the differences is the electronic ground state in low-spin bis( (t)BuNC) complexes. While [Fe(OEP)( (t)BuNC) 2] (+) adopts the (d xz , d yz ) (4)(d xy ) (1) ground state, like most of the bis( (t)BuNC) complexes reported previously, [Fe(MAzP)( (t)BuNC) 2] (+) has shown the (d xy ) (2)(d xz , d yz ) (3) ground state. Another difference is the spin state of the bis(3,5-Cl 2Py) complexes. While [Fe(OEP)(3,5-Cl 2Py) 2] (+) has maintained the mixed S = 3/2 and 5/2 spin state from 298 to 4 K, [Fe(MAzP)(3,5-Cl 2Py) 2] (+) has shown the spin transition mentioned above. These differences have been ascribed to the narrower N4 cavity and the presence of lower-lying pi* orbital in MAzP as compared with OEP.     

Dependence of the conduction of a single biphenyl dithiol molecule on the dihedral angle between the phenyl rings and its application to a nanorectifier

The transport properties of a biphenyl dithiol (BPD) molecule sandwiched between two gold electrodes are studied using the nonequilibrium Green's function method based on the density functional theory. In particular, their dependence on the dihedral angle (phi=90 degrees -180 degrees ) between two phenyl rings is investigated. While the dihedral-angle dependence of the density of states projected on the BPD molecular orbitals is small, the transport properties change dramatically with phi. The transmission at the Fermi energy exhibits a minimum at phi=90.0 degrees and greatly increases with phi. The ratio of the maximum obtained at phi=180 degrees to the minimum exceeds 100. As an application of this characteristic transport behavior, a BPD molecule functionalized with NH(2) and NO(2) groups is considered. It is found that this molecule works as a nanorectifier.