Near-infrared spectroscopy for liquids of microliter volume using capillaries with wall transmission

In the present study we propose a capillary tube method for measuring near-infrared (NIR) spectra of microliter liquid and solution samples. This method enables one to measure NIR spectra of liquids and solutions of only 2.5 microl. As an example of the capillary tube method, Fourier-transform NIR spectra of benzene were measured using a capillary tube with a diameter of 1 mm. Positions and intensities of the NIR bands in the spectra obtained by the capillary tube were almost identical to those measured using a quartz cuvette cell. Moreover, capillary NIR spectra of human blood serum obtained from a patient with backbone neoplasm were also measured. Subtraction of the NIR spectrum of water from those of human blood serum develops unambiguously some NIR bands due to blood components such as proteins and glucose. Our results suggest that capillary NIR spectroscopy will open new areas of NIR applications for small amounts of liquid and solution samples.     

The Interaction of C60, C70, and C60(CN)2 radical anions with cobalt(II) tetraphenylporphyrin in solid multicomponent complexes

A method for the synthesis of the multicomponent ionic complexes: [Cr(I)(C(6)H(6))(2) (.+)][Co(II)(tpp)(fullerene)(-)].C(6)H(4)Cl(2), comprising bis(benzene)chromium (Cr(C(6)H(6))(2)), cobalt(II) tetraphenylporphyrin (Co(II)(tpp)), fullerenes (C(60), C(60)(CN)(2), and C(70)), and o-dichlorobenzene (C(6)H(4)Cl(2)) has been developed. The monoanionic state of the fullerenes has been proved by optical absorption spectra in the UV/vis/NIR and IR ranges. The crystal structures of the ionic [[Cr(I)(C(6)H(6))(2)](.+)](1.7)[[Co(II)(tpp)(C(60))](2)](1.7-). 3.3 C(6)H(4)Cl(2) and [[Cr(I)(C(6)H(6))(2)] (.+)](2)[Co(II)(tpp)[C(60)(CN)(2)]](-)[C(60)(CN)(2) (.-)]).3 C(6)H(4)Cl(2) are presented. The essentially shortened Co.C(fullerene) bond lengths of 2.28-2.32 A in these complexes indicate the formation of sigma-bonded [Co(II)(tpp)][fullerene](-) anions, which are diamagnetic. All the ionic complexes are semiconductors with room temperature conductivity of 2 x 10(-3)-4 x 10(-6) S cm(-1), and their magnetic susceptibilities show Curie-Weiss behavior. The neutral complexes of Co(II)(tpp) with C(60), C(60)(CN)(2), C(70), and Cr(0)(C(6)H(6))(2), as well as the crystal structures of [Co(II)(tpp)](C(60)).2.5 C(6)H(4)Cl(2), [Co(II)(tpp)](C(70)). 1.3 CHCl(3).0.2 C(6)H(6), and [Cr(0)(C(6)H(6))(2)][Co(II)(tpp)] are discussed. In contrast to the ionic complexes, the neutral ones have essentially longer Co.C(fullerene) bond lengths of 2.69-2.75 A.     

Formation of single-bonded (C60-)2 and (C70-)2 dimers in crystalline ionic complexes of fullerenes

New ionic complexes of fullerenes C(60) and C(70) with decamethylchromocene Cp*(2)Cr.C60.(C(6)H(4)Cl(2))(2) (1), Cp*(2)Cr.C60.(C(6)H(6))(2) (2); the multicomponent complex of (Cs(+))(C70-) with cyclotriveratrylene CTV.(Cs)(2).(C70)(2).(DMF)(7).(C(6)H(6))(0.75) (3); bis(benzene)chromium Cr(C(6)H(6))(2).C60.(C(6)H(4)Cl(2))(0.7) (4), Cr(C(6)H(6))(2).C60.C(6)H(5)CN (5), Cr(C(6)H(6))(2).C70.C(6)H(4)Cl(2) (6), Cr(C(6)H(6))(2).C60 (7); cobaltocene Cp(2)Co.C60.C(6)H(4)Cl(2) (8), Cp(2)Co.C70.(C(6)H(4)Cl(2))(0.5) (9); and cesium Cs.C70.(DMF)(5) (10) have been obtained. The complexes have been characterized by the elemental analysis, IR-, UV-vis-NIR spectroscopy, EPR and SQUID measurements. It is shown that C(60)(.-) exists as a single-bonded diamagnetic (C60-)2 dimer in 1, 2, 4, 5, and 8 at low temperatures (1.9-250 K). The dimers dissociate above 160-250 K depending on donor and solvent molecules involved in the complex. C60(.-) dimerizes reversibly and shows a small hysteresis (<2 K) at slow cooling and heating rates. The single-bonded diamagnetic (C70-)2 dimers are also formed in 6, 9, and 10 and begin to dissociate only above 250-360 K. The IR and UV-vis-NIR spectra of sigma-bonded negatively charged fullerenes are presented.     

Palladium-catalyzed [3 + 2] cycloaddition reaction using 2-(sulfonylmethyl)- or 2-(cyanomethyl)allyl carbonate

Reaction of ethyl 2-(sulfonylmethyl)- or 2-(cyanomethyl)allyl carbonate with α,β-unsaturated esters or ketones in the presence of PD₂(dba)₃·.CHCl₃-dppe catalyst gave highly functionalized cyclopentanes regio-selectively in good yields.     

Flame retardancy and heat resistance of phenol-biphenylene-type epoxy resin compound modified with benzoguanamine

The flame retardancy and heat resistance of a phenol-biphenylene-type epoxy resin compound, which forms a self-extinguishing network structure, were increased by the inclusion of a benzoguanamine-modified phenol biphenylene resin. The benzoguanamine-modified phenol biphenylene resin contains a benzoguanamine unit to release non-flammable nitrogen substances during ignition and to increase the resin's reactivity toward epoxy resins, and biphenylene units to keep the resin's thermal degradation and water resistance. The addition of the benzoguanamine-modified phenol biphenylene resin in the epoxy resin compound improved the epoxy resin compound's flame retardancy and heat resistance, and also increased its glass transition temperature while maintaining its water resistance and mechanical properties. Copyright © 2003 John Wiley & Sons, Ltd.     

Classification of single-molecule surface-enhanced resonance Raman spectra of Rhodamine 6G from isolated Ag colloidal particles by principal component analysis

Surface enhanced resonance Raman (SERR) spectra of Rhodamine 6G are measured from single isolated Ag particles and analyzed by using a chemometrics technique, principal component analysis (PCA). The Ag particles are incubated with various amounts of R6G yielding the ratio of Ag particles to R6G molecules from 1:1 to 1:1000. Acquired SERR spectra are considered due to a single or very few R6G molecules. PCA is used to determine the number of chemically distinguishable species that contribute to the measured SERR spectra. A simple clustering tool, score bi-plot, is then inspected on grouping of the SERR spectra. The spectra are found to be largely similar except for the variability in the intensity and position of the bands that is believed to be correlated with the lifetime of the strong enhancement at specific places on an Ag surface. The spectra from four different Ag particles carrying more than 1000 R6G molecules are, however, unambiguously separated. Different aspects of the applied data analysis method and physicochemical perspective of the results are discussed.     

Asymmetric total synthesis of (-)-azaspirene,a novel angiogenesis inhibitor

The asymmetric total synthesis of (-)-azaspirene, an angiogenesis inhibitor, has been accomplished, establishing its absolute stereochemistry. The key steps are a MgBr2.OEt2-mediated, diastereoselective Mukaiyama aldol reaction, a NaH-promoted, intramolecular cyclization of an alkynylamide, and the aldol reaction of a ketone containing functionalized gamma-lactam moiety without protection of tert-alcohol and amide functionalities.     

Segmental orientation and chain relaxation of polymers by fourier transform infrared dichroism

Fourier transform infrared dichroism has been used to investigate molecular orientation in polymeric materials. It is first applied to characterize network behavior in some elastomeric systems such as model networks of poly(dimethylsiloxane). The strain dependence of segmental orientation is analyzed through networks of known degree of cross-linking and experimental results are compared with calculation predictions based on the rotational isomeric state formalism. Infrared dichroism spectroscopy has also been used to analyze orientational relaxation in binary blends of long and short polystyrene chains. The effect of short deuterated chains (M_w = 3000 to 72000) on the orientational relaxation of long entangled chains (Mw = 2 000 000) is examined in the bidisperse melts uniaxially deformed above the glass transition temperature. While the long chain relaxation is found to be dependent on the short-chain concentration, the local orientational order of the latter is molecular weight dependent in agreement with the classical relaxation theories.     

Relationship between the coil-globule transition of an aqueous poly(N-isopropylacrylamide) solution and structural changes in local conformations of the polymer

Structural changes in the local conformation of poly(N-isopropylacrylamide) (PNiPA) during the thermally and solvent-induced coil-globule transitions in an aqueous solution were studied by using attenuated total reflection / infrared (ATR/IR) spectroscopy combined with density functional theory (DFT) calculation. DFT calculation makes it possible to connect the spectral changes observed during the transitions with the structural changes of the local conformation of polymer chains. The results suggest that some of the intramolecular C=O···H-N hydrogen bonds of amide groups are broken, and the changes in local conformations occur during the coil-globule transitions of PNiPA. In this paper, an overview of our recent studies on the coil-globule transitions of PNiPA is given for introducing a new idea that may explain the stimulus sensitivities of PNiPA in solutions; the solubility of segments concerning with the local conformation of repeating monomer units is changed by an external perturbation, and then the polymer system shows the coil-globule transition.