Novel coordinatively unsaturated bimetallic complexes, [(eta5-C5Me5)Ru(mu2-iPrNC(Me)=N(i)Pr)Ru(eta5-C5Me5)]+: a bridging amidinate ligand perpendicular to the metal-metal axis effectively stabilizes the highly reactive cationic diruthenium species.

Coordinatively unsaturated diruthenium complexes, [(eta5-C5Me5)Ru(mu2-iPrNC(Me)=NiPr)Ru(eta5-C5Me5)]+, of which crystallography revealed structures bearing a bridging amidinate ligand perpendicular to the Ru-Ru axis, were synthesized by anion exchange of [(eta5-C3Me5(Ru(mu2-iPrNC(Me)=NiPr)Ru(eta5-C5Me5)]+ Br- by weakly coordinating anions. Variable-temperature NMR showed rapid motion of the bridging amidinate ligand. The coordinatively unsaturated nature of the cationic complexes provides their high reactivity toward a series of two electron donor ligands. Oxidative addition of molecular hydrogen occurred to give [(eta5-C5Me5)Ru(mu2-iPrNC(Me)=NiPr)(mu-H)Ru(eta5-C5Me5)(H)]+, which was isolated and characterized.     

A multipolymer system for organocatalytic alcohol oxidation

A system involving two polymer-supported reagents for the selective and organocatalytic oxidation of alcohols to aldehydes or ketones has been developed in which both polymeric reagents can be recovered and reused.     

Solubilization and applications of single-walled carbon nanotubes into aqueous and organic media by the use of nanometer size-controlled fluoroalkyl end-capped oligomeric aggregates

We have studied on the solubilization of single-walled carbon nanotubes (SW-CNTs) into aqueous and organic media by the use of a variety of nanometer size-controlled fluorinated self-assemblies, which were formed by the aggregations of end-capped fluoroalkyl segments in fluoroalkyl end-capped acrylic acid oligomers [R_F-(ACA)_n-R_F], N,N-dimethylacrylamide oligomers [R_F-(DMAA)_n-R_F], acryloylmorpholine oligomers [R_F-(ACMO)_n-R_F], and N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers [R_F-(DOBAA)_n-R_F]. Fluorinated self assemblies formed in organic media (colorless solutions) could solubilize SW-CNTs into organic media to afford the transparent pale yellow solutions. The dynamic light scattering measurements showed that the size of fluorinated self-assemblies increased after the solubilization of SW-CNTs into organic media. It was suggested that the solubilization of SW-CNTs into organic media is due to the encapsulation of SW-CNTs into fluorinated assemblies. Fluorinated assemblies were also able to solubilize SW-CNTs into water to give the transparent gray solutions. Among a variety of fluorinated assemblies, fluorinated assemblies formed by R_F-(ACMO)_n-R_F [R_F = CF(CF₃)OC₆F₁₃] oligomer was more effective for the solubilization of SW-CNTs into both aqueous and organic media. Contact angle measurements of dodecane and the fluorescence spectra for poly(methyl methacrylate) cast film modified by fluorinated self-assemblies—SW-CNTs complexes showed that SW-CNTs are dispersed above the PMMA surface.     

Synthesis and inhibitory effect of novel glycyrrhetinic acid derivatives on IL-1 beta-induced prostaglandin E(2) production in normal human dermal fibroblasts

Olean-11,13(18)-dien-3beta,30-diol dihemiphthalate (3), which was derived from glycyrrhetinic acid (GA), has been reported to produce a potent of anti-inflammatory effect in in vivo assays. Using 3 as a lead compound, we attempted to synthesize some modified compounds which varied in the following; i) the position of a carboxyl group in the phthalate moiety, ii) the number of carboxyls attached to the benzoyl group, iii) conversion of benzene ring to another ring system, iv) the linkage form between the benzene ring and oleanene skeleton at position 3 and/or 30. These were screened for their inhibitory activity against interleukin-1 beta (IL-1 beta)-induced prostaglandin E(2) (PGE(2)) production in normal human dermal fibroblasts (NHDF). Although conversion of the ortho-carboxyl group of 3 into the meta-position or the para-position led to an increase in inhibitory activity, the elimination or increase of the carboxyl group resulted in loss of the inhibitory activity. Conversion of the ester bond to the amide bond at position 3 and/or 30 of 3 did not contribute to a significant increase in inhibitory activity. On the other hand, among the derivatives possessing an anthranilic acid moiety at position 30 of 3beta-O-acetyl-olean-11,13(18)-dien-30-oic acid (20), 3beta-hydroxy-30-nor-olean-11,13(18)-dien-20 beta-[N-(2-carboxyphenyl)]carboxamide (30) showed the most potent inhibitory activity (IC(50) 1.0 microM) in this series.     

Duplex dissociation of telomere DNAs induced by molecular crowding

Because of the importance of telomere DNAs, the structures of these DNAs in vivo are currently of great research interest in the medical, pharmaceutical, chemical, and industrial fields. To understand the structure of biomolecules in vivo, their properties studied in vitro are extrapolated to the in vivo condition, while the condition in a living cell is inherently molecularly crowded and a nonideal solution contains various biomolecules. We investigated the effect of molecular crowding, which is one of the most important cellular environmental conditions, on the structure and stability of the telomere and G-rich and C-rich DNAs using circular dichroism (CD) spectra, CD melting curves, and isothermal titration calorimetry (ITC). The CD spectra and CD melting curves of G-rich DNA, C-rich DNA, and the 1:1 mixture of G-rich and C-rich DNAs showed that each G-rich DNA, C-rich DNA, and the 1:1 mixture form the antiparallel G-quadruplex, I-motif, and duplex, respectively, in the noncrowding condition as previously considered. On the contrary, the G-rich and C-rich DNAs individually form the parallel G-quadruplex and I-motif, respectively, in the molecular crowding condition, and the 1:1 mixture folds into the parallel G-quadruplex and I-motif but does not form a duplex. The ITC measurements indicated that the thermodynamic stability (DeltaG degrees (20)) of the duplex formation between the G-rich and C-rich DNAs in the noncrowding condition was -10.2 kcal mol(-)(1), while only a small heat change was observed in the ITC measurements in the molecular crowding condition. These ITC results also demonstrated that the molecular crowding condition prevents any duplex formation between G-rich and C-rich DNAs. These results indicate that a structural polymorphism of the telomere DNAs is induced by molecular crowding in vivo.     

From mononuclear to multinuclear complexes of palladium containing unsaturated hydrocarbon ligands

This review summarizes the author’s contributions to the field of chemistry of group 10 metal complexes containing unsaturated hydrocarbon ligands, with a brief introduction showing how his research subject has shifted from mononuclear type to multinuclear type complexes. New structure and reactivity trends in the multipalladium complexes with bridging allyl and allenyl/propargyl ligands, as well as bridging conjugated polyene molecules are discussed in terms of some unique bonding features of these complexes.     

Glass transition temperature of polyurethane foams derived from lignin by controlled reaction rate

Sodium ligninosulfonate (LS)-based polyurethane (PU) foams were prepared using three kinds of ethylene glycols, diethylene glycol, triethylene glycol or polyethylene glycol. Two kinds of industrial NaLS, acid-based and alkaline-based NaLS, were mixed with various ratios, and foaming reactions were controlled. Mixing, cream, and rise time were used as an index of foaming reaction. Mixing time was defined as the time interval from adding isocyanate to detection of evolved heat under stirring, cream time as the time interval from termination of stirring to starting of foaming, and rise time as the time interval from starting to completion of foaming. The above reaction time increased with increasing amount of acid base NaLS content in polyols. Apparent density, compression strength and compression modulus of PU foams linearly increased with reaction time. Thermal decomposition temperature was measured by thermogravimetry and glass transition temperature by differential scanning calorimetry. Glass transition temperature can be controlled in a temperature range from 310 to 390 K by changing the mixing rate of two kinds of LS and molecular mass of ethylene glycols. It was found that mechanical and thermal properties of PU foams are controllable through the foaming reaction rate using two kinds of industrial lignin.     

Redox features of β-VOPO4 catalyst using tracer and laser Raman spectroscopy

The oxygen ions of the β-VOPO₄ catalyst were exchanged with an tracer by a reduction–oxidation method and by a catalytic oxidation of but-1-ene using ₂. The bands at 992 and 900 cm⁻¹ were more shifted to lower frequencies than those at 1076 and 1002 cm⁻¹. Applying the correlation between the Raman bands and stretching vibrations in the literature, the exchanged oxygen species were estimated. The results suggest that the P–O–V vacancies corresponding to 992 and 900 cm⁻¹ were responsible for reoxidation and the V=O oxygen corresponding to the 1002 cm⁻¹ band of β-VOPO₄ was not. The (VO)₂P₂O₇ was oxidized to β-VOPO₄ by O₂ above 823 K. The insertion position of oxygen was determined at the bands at 992 and 900 cm⁻¹ of β-VOPO₄ using ₂, which is the same as the exchanged position.     

Novel synthesis, static and dynamic properties, and structural characteristics of 5-cyano[n](2,4)pyridinophane-6-ones (n= 9-6) and their chemical transformations

A novel synthesis of 5-cyano[n](2,4)pyridinophane-6-ones 12a-d (n= 9, 8, 7, and 6) consists of allowing cyanoacetatoamide to react with cycloalk-2-enones. Their static and dynamic properties as well as structural characteristics are studied on the basis of their spectroscopic properties, cyclic voltammetry, and theoretical calculations. The (1)H and (13)C NMR spectra at various temperatures have clarified the dynamic behavior of the methylene chains for [7](2,4)- and [6](2,4)pyridinophane-6-one derivatives 12c and 12d. The energy barrier (Delta G(++)) of the bridge flipping of 12c is estimated to be 12.0 kcal mol(-1)(T(c)= 0 degree C). On the other hand, compound 12d undergoes pseudorotation (conformational change of the methylene chain) at room temperature, and does not undergo bridge flipping even at 150 degree C in DMSO-d(6). The energy barrier (Delta G(++)) of the pseudorotation of the methylene chain 12d of is found to be 10.5 kcal mol(-1)(T(c)=-25 degree C), and thus, two stable conformers of the hexamethylene bridge of 12d are determined as predicted by theoretical calculations. Deformation of the pyridone ring of 12d is also determined by X-ray crystallographic analysis. Furthermore, chemical transformations of 12a-c leading to 5-carbamoyl[n](2,4)pyridinophanes 15a-c are also accomplished successfully in moderate to good yields.