Structure identification of chemical substances from infrared spectra can be done with various approaches: a theoretical method using quantum chemistry calculations, an inductive method using standard spectral databases of known chemical substances, and an empirical method using rules between spectra and structures. For various reasons, it is difficult to definitively identify structures with these methods. The relationship between structures and infrared spectra is complicated and nonlinear, and for problems with such nonlinear relationships, neural networks are the most powerful tools. In this study, we have evaluated the performance of a neural network system that mimics the methods used by specialists to identify chemical structures from infrared spectra. Neural networks for identifying over 100 functional groups have been trained by using over 10000 infrared spectral data compiled in the integrated spectral database system (SDBS) constructed in our laboratory. Network structures and training methods have been optimized for a wide range of conditions. It has been demonstrated that with neural networks, various types of functional groups can be identified, but only with an average accuracy of about 80%. The reason that 100% identification accuracy has not been achieved is discussed.

In order to clarify the origin of the cocrystallization and phase segregation phenomena observed for a series of polyethylene blends between the deuterated and hydrogeneous species, time-resolved Fourier-transform infrared spectroscopic measurements have been performed under isothermal crystallization conditions by controlling the degree of undercooling or the temperature jump depth from the molten state to the isothermal crystallization temperature. A closeness of the crystallization rate between the pure D and H species was found to correlate well with the occurrence of the cocrystallization phenomenon. In the cocrystallizable blend sample, the crystallization rates of the D and H components were found to be almost the same and accelerated remarkably when compared with those of the individual pure components. The mechanism of cocrystallization and phase segregation was discussed from the viewpoints of both thermodynamics and kinetics.

It has always been difficult to perform analysis and characterization of substances in aqueous solution by using infrared (IR) spectrometry. We propose a new method in which ions are concentrated on the attenuated total reflection (ATR) surface of a germanium prism by using an electrophoretic means. The method may provide insolution. These results implied that the dissolved state of sodium decanoate in 0.06 M solution was different from that in 0.02, 0.04, and 0.2 M solutions.

Liquid-crystalline benzoic acid derivatives, 4-pentylbenzoic acid and 4-hexylbenzoic acid, have been examined by infrared spectroscopy. These benzoic acids show nematic phases. In the crystalline state, only the dimeric form is observed. However, the monomeric non-hydrogen-bonded benzoic acid appears once the temperature reaches the crystal-nematic transition (melting) point. The fraction of the monomeric moiety increases upon heating and an abrupt increase is observed at the isotropization temperature. These results suggest that the stability of the hydrogen bonds is not simply a function of the temperature, but greatly depends on the molecular orientation.

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Abstract The stability of a hydrogen-bonded complex built through inter-molecular hydrogen bonding between carboxylic acid and pyridine fragments has been examined using infrared spectroscopy. Infrared spectra as a function of temperature have been recorded for the 1:1 complex of 4-hexyloxybenzoic acid and trans-4-propoxy-4′-stilbazole from the crystalline state to the isotropic state. A dependence of the stability of the hydrogen bond on molecular orientation is observed clearly in the infrared spectra. The spectra also suggest that the hydrogen bond is an unionized type with a double minimum potential energy.

Mesogenic structures have been built from 2:1 (molar ratio) mixtures of 4-alkoxy- or 4-alkylbenzoic acid (nOBA or nBA; n is the carbon number of the alkyl chain) and 4,4'-bipyridine (BPy)or trans-1,2-bis(4-pyridyl)ethylene(BPyE). In these complexes, the benzoic acid derivative functions as an H-bond donor and the bipyridyl compound operates as a bifunctional H-bond acceptor. Well-defined structures of the mesogenic complexes are formed from independent and different molecules. These complexes exhibit stable mesophases that are not observed for each of the single components. For example, a 2:1 (molar ratio) complex prepared from 4-ethoxybenzoic acid (20BA) and 4,4'-bipyridine (BPy) shows a nematic phase from 150 to 169-degrees-C while both individual compounds are nonmesogenic. The liquid-crystalline phase is induced by the hydrogen bonding. The 2:1 complex of 4-butoxybenzoic acid (40BA) and bis(4-pyridyl)ethylene (BPyE) exhibits a smectic A phase (146-168-degrees-C) and a nematic phase trans-1,2-(168-177-degrees-C). The smectic phase displayed by the complex is not observed for 4OBA and BPyE. The isotropization temperature is increased by the complexation through the H bonds. The effect of the terminal alkyl chain length on thermal properties has been examined for the 2:1 H-bonded complexes of a series of the benzoic acids and the bipyridyl compound. The type of mesophases obtained is affected by the alkyl chain length. Infrared study suggests that the hydrogen bond is an un-ionic type with a double minimum potential energy and its stability is greatly dependent on the order of the molecular complexes. Phase diagrams have been obtained for the binary mixture of H-bond donor and acceptor moieties. The isotropization temperature curves show significant positive deviations because of the intermolecular H-bond interaction.

The structure of cis-[CoF2(NH3)4]ClO4 has been determined by a single-crystal X-ray diffraction method. Crystals are tetragonal, space group P4(1) (or P4(3)), a = 7.2645(6), c = 16.260(2) angstrom, V = 858.1(2) angstrom 3, Z = 4, T = 297(1) K, final R = 0.052 for 970 observed unique reflections. The coordinated F and N atoms could be distinguished unambiguously from each other based on the thermal parameters. The bond distances Co-F and Co-N are 1.828(6)-1.870(5) and 1.924(7)-1.944(7) angstrom, respectively. The absorption spectra of the single crystals have been examined in the visible and infrared regions with polarized radiation by the use of microspectrophotometers. The 584 nm band (B1) was considered to borrow intensity from some A1 bands through vibronic coupling with some B1 vibrations, and the 504 nm band (A2 & B2) through some A2 and B2 vibrations. Two of the four ammine groups of this cobalt complex were found to give an NH3 rocking frequency (860 cm-1) higher by 50 cm-1 than the other two (at 810 cm-1). This fact has been attributed to two inter-molecular hydrogen bonds (NH...F = 2.85-2.68 angstrom) in which the former two ammine groups are involved.

A fowl feather barb 10 μm in thickness was subjected to a polarized infrared spectroscopic measurement by the use of a microscopic device. Nearly 50% of its peptide groups were found to give the 1633 and 1684 cm−1 bands characteristic of the antiparallel-chain pleated sheet structure, and the remaining 50% gave the 1659 cm−1 band assignable to unordered polypeptide chains. The orientation of the pleated sheet was determined to be on average θ = 52° and χ = 39°, where θ and χ are the angles for the transformation of the XYZ coordinate system fixed on the pleated sheet and the abc coordinate system fixed on the sample barb. The Raman spectra of the barb were also examined with another microscopic device and a 488.0-nm laser beam. A sharp aa component of the Raman scattering tensor was observed at 1667 cm−1. Based on this fact, a revised set of parameters for the vibrational couplings among the peptide groups in the pleated sheet has been proposed. Some discussions have been made on the amide I Raman tensor of the antiparallel-chain pleated sheet. Key words: fowl feather barb, Raman microscope, infrared microscope, antiparallel-chain pleated sheet, Raman scattering tensor.

Porous glass was made from a mixture of 45–70% SiO2, 8–30% B2O3, 8–25% CaO, 5–15% Al2O3, 3–8% Na2) + 1–5% K2O and 0–8% MgO. The mixture was heated at 600–850°C for 20 h and cut into square sheets of 5 cm × 5 cm × 0.5 mm. Each sheet was leached with 1 M hydrochloric acid at 80–90%C for 4–16 h to make it porous. The surface of each sheet was examined with a scanning electron micrograph. The various sheets with pore diameters from 110 to 1200 nm were developed with a few common solvents for thin-layer chromatography (TLC). The larger the pore diameters, the shorter were the developing times with the solvents. A sheet of 700 nm pore diameter required only a few minutes and showed good separations, and was adopted in the subsequent TLC study.

Basic studies of the combined system of a high performance liquid chromatograph (HPLC) and a circular dichroism (CD) spectrometer for separation and analysis of proteins are described. The HPLC-CD measurement of standard protein mixture was easily carried out by using a micro flow-cell device with a beam condenser and with a thin cell of a 1 mm-optical path. The effluent was firstly monitored at 280 nm by using an UV detector and subsequently monitored at 220 nm by using a CD spectrometer. The CD spectrum at each chromatographic peak by CD was measured in the wavelength region of 250–195 nm by a stopped flow method.

赤外吸収スぺクトル法による定量は通常標準物質を用い,頂点強度法により行なわれているが,この測定法は標準物質が得られない時には適用できず,頂点強度は器差が大きいため,文献値の借用はできないといわれている。そこで器差の少ない強度測定法を検討するために,Ramsay法による絶対強度と分子吸光係数比をとり上げ,各種多数の装置を用いて測定した。その結果,共に満足すべき結果が得られたが,絶対強度の場合には,半値幅の測定の誤差が大きく,装置間の変動係数は5%程度であった。これは装置などを改良することにより更に改善されると考えられる。分子吸光係数比に関しては,3%程度の変動係数で一致し,十分文献値を利用できることがわかった。両方法ともに岩塩プリズム使用の分光光度計では装置の両端,すなわち,約3600cm-1以上と約750cm-1以下ではバラツキが大きくなり,注意する必要があった。